Journal articles on the topic 'Pathway FA'
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1
Jenkins, Chelsea, Jenny Kan, and Maureen E. Hoatlin. "Targeting the Fanconi Anemia Pathway to Identify Tailored Anticancer Therapeutics." Anemia 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/481583.
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The Fanconi Anemia (FA) pathway consists of proteins involved in repairing DNA damage, including interstrand cross-links (ICLs). The pathway contains an upstream multiprotein core complex that mediates the monoubiquitylation of the FANCD2 and FANCI heterodimer, and a downstream pathway that converges with a larger network of proteins with roles in homologous recombination and other DNA repair pathways. Selective killing of cancer cells with an intact FA pathway but deficient in certain other DNA repair pathways is an emerging approach to tailored cancer therapy. Inhibiting the FA pathway becomes selectively lethal when certain repair genes are defective, such as the checkpoint kinase ATM. Inhibiting the FA pathway in ATM deficient cells can be achieved with small molecule inhibitors, suggesting that new cancer therapeutics could be developed by identifying FA pathway inhibitors to treat cancers that contain defects that are synthetic lethal with FA.
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Kennedy, R. D., P. Stuckert, E. Archila, M. De LaVega, C. Chen, L. Moreau, and A. D'Andrea. "Sensitivity of tumor cells deficient in the fanconi anemia pathway to inhibition of ataxia telangiectasia mutated (ATM)." Journal of Clinical Oncology 25, no. 18_suppl (June 20, 2007): 10509. http://dx.doi.org/10.1200/jco.2007.25.18_suppl.10509.
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10509 Loss of the fanconi anemia (FA) pathway function has been described in a number of sporadic tumor types including breast, ovarian, pancreatic, head and neck and hematological malignancies. Functionally, the FA pathway responds to stalled DNA replication following DNA damage. Given the importance of the FA pathway in the response to DNA damage, we hypothesized that cells deficient in this pathway may become hyper-dependent on alternative DNA damage response pathways in order to respond to endogenous genotoxic stress such as occurs during metabolism. Therefore, targeting these alternative pathways could offer therapeutic strategies in FA pathway deficient tumors. To identify new therapeutic targets we treated FA pathway competent and deficient cells with a DNA damage response siRNA library, that individually knocked out 230 genes. We identified a number of gene targets that were specifically toxic to FA pathway deficient cells, amongst which was the DNA damage response kinase Ataxia Telangiectasia Mutated (ATM). To test the requirement for ATM in FA pathway deficient cells, we interbred Fancg ± Atm± mice. Consistent with the siRNA screen result, Fancg-/- Atm-/- mice were non viable and Fancg± Atm-/- and Fancg-/- Atm ± progeny were less frequent that would have been expected. Several human cell lines with FA gene mutations were observed to have constitutive activation of ATM which was markedly reduced on correction with the appropriate wild-type FA gene. Interestingly, FA pathway deficient cells, including the FANCC mutant and FANCG mutant pancreatic cancer cell lines, were selectively sensitive to monotherapy with the ATM inhibitor KU55933, as measured by dose inhibition and colony count assays. FA pathway deficient cells also demonstrated an increased level of chromosomal breakage, cell cycle arrest and apoptosis following KU55933 treatment when compared to FA pathway corrected cells. We conclude that FA pathway deficient cells have an increased requirement for ATM activation in order to respond to sporadic DNA damage. This offers the possibility that monotherapy with ATM inhibitors could be a therapeutic strategy for tumors that are deficient for the FA pathway. No significant financial relationships to disclose.
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Li, Niu, Jian Wang, Susan S. Wallace, Jing Chen, Jia Zhou, and Alan D. D’Andrea. "Cooperation of the NEIL3 and Fanconi anemia/BRCA pathways in interstrand crosslink repair." Nucleic Acids Research 48, no. 6 (January 25, 2020): 3014–28. http://dx.doi.org/10.1093/nar/gkaa038.
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Abstract The NEIL3 DNA glycosylase is a base excision repair enzyme that excises bulky base lesions from DNA. Although NEIL3 has been shown to unhook interstrand crosslinks (ICL) in Xenopus extracts, how NEIL3 participants in ICL repair in human cells and its corporation with the canonical Fanconi anemia (FA)/BRCA pathway remain unclear. Here we show that the NEIL3 and the FA/BRCA pathways are non-epistatic in psoralen-ICL repair. The NEIL3 pathway is the major pathway for repairing psoralen-ICL, and the FA/BRCA pathway is only activated when NEIL3 is not present. Mechanistically, NEIL3 is recruited to psoralen-ICL in a rapid, PARP-dependent manner. Importantly, the NEIL3 pathway repairs psoralen-ICLs without generating double-strand breaks (DSBs), unlike the FA/BRCA pathway. In addition, we found that the RUVBL1/2 complex physically interact with NEIL3 and function within the NEIL3 pathway in psoralen-ICL repair. Moreover, TRAIP is important for the recruitment of NEIL3 but not FANCD2, and knockdown of TRAIP promotes FA/BRCA pathway activation. Interestingly, TRAIP is non-epistatic with both NEIL3 and FA pathways in psoralen-ICL repair, suggesting that TRAIP may function upstream of the two pathways. Taken together, the NEIL3 pathway is the major pathway to repair psoralen-ICL through a unique DSB-free mechanism in human cells.
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Hays, Laura E. "Multifunctionality of the FA pathway." Blood 121, no. 1 (January 3, 2013): 3–4. http://dx.doi.org/10.1182/blood-2012-11-464636.
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Zhang, Haojian, David Kozono, Kevin O'Connor, Sofia Vidal-Cardenas, Abigail Hamilton, Emily Gaudiano, Joel S. Greenberger, Markus Grompe, Kalindi Parmar, and Alan D. D'Andrea. "Bone Marrow Failure in Fanconi Anemia from Hyperactive TGF-β Signaling." Blood 124, no. 21 (December 6, 2014): 356. http://dx.doi.org/10.1182/blood.v124.21.356.356.
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Abstract Fanconi anemia (FA) is the most common inherited bone marrow failure syndrome. FA patients develop bone marrow failure during the first decade of life due to attrition of hematopoietic stem and progenitor cells (HSPCs). FA patients also develop other hematologic manifestations, including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) due to clonal evolution. FA is caused by biallelic mutants in one of sixteen FANC genes, the products of which cooperate in the FA/BRCA DNA repair pathway and regulate cellular resistance to DNA cross-linking agents. Bone marrow failure in FA may result, directly or indirectly, from hyperactivation of cell autonomous or microenvironmental growth suppressive pathways induced due to genotoxic stress. Recent studies suggest that one suppressive pathway may be the hyperactive p53 response observed in HSPCs from FA patients. In order to further identify suppressive mechanisms accounting for bone marrow failure in FA, we performed a whole genome-wide shRNA screen in FA cells. Specifically, we screened for candidate genes whose knockdown would rescue cellular growth inhibition and genotoxic stress induced by a DNA cross-linking agent mitomycin C (MMC). We transduced a FA-deficient human fibroblast line with pools of shRNAs and screened for rescue of MMC-inhibited growth. Selected shRNA inserts were identified by next generation sequencing. The top hits in the screen were shRNAs directed against multiple components of the TGF-β signaling pathway. Consistent with this, disruption of the TGF-β signaling pathway by shRNA/sgRNA-mediated knockdown of SMAD3 or TGFR1 (downstream components of the TGF- β pathway) rescued growth of multiple cell lines from several FA complementation groups in presence of genotoxic agents (e.g. MMC or acetaldehyde). Pharmacologic inhibition of the TGF- β pathway using small molecule inhibitors resulted in improved survival of FA-deficient lymphoblast cells in presence of MMC or acetaldehyde, suggesting that a hyperactive, TGF-β-mediated, suppression pathway may account, at least in part, for reduced FA cell growth. Interestingly, genes encoding TGF-β pathway signaling components were highly expressed in the bone marrow from FA patients and FA mice. Moreover, disruption of the TGF- β pathway by shRNA-mediated knockdown of SMAD3 rescued the growth defects of primary HSPCs from FA-deficient murine bone marrow. To further implicate the TGF-β pathway, we established primary stromal cell lines from the bone marrow of FA-deficient mice as well as human FA patients. We confirmed that TGF-β signaling was hyperactive in these stroma cells resulting in growth suppression and elevated phospho-ERK levels due to non-canonical signaling of the pathway. Inhibitors of TGF-β signaling partially rescued the growth defects and reduced phospho-ERK levels in these FA stroma cells. The deficiency of FA DNA repair pathway leads to cellular defects in homologous recombination (HR) repair and hyperactivation of toxic non-homologous end joining (NHEJ)-mediated repair. We therefore tested whether inhibition of the TGF-β pathway in FA cells could rescue HR defects and account for the improvement of FA cellular growth. Interestingly, disruption of the TGF-β signaling pathway caused a decrease in NHEJ activity. Disruption of the TGF-β pathway also resulted in reduced MMC-mediated DNA damage and increased HR. Taken together, our results demonstrate that primary FA hematopoietic and bone marrow stromal cells exhibit hyperactive TGF-β signaling accounting at least in part for the bone marrow failure in FA. Inhibitors of the TGF-β signaling pathway may therefore be useful in the clinical treatment of patients with bone marrow failure and Fanconi anemia. Disclosures No relevant conflicts of interest to declare.
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Niraj, Joshi, Anniina Färkkilä, and Alan D. D'Andrea. "The Fanconi Anemia Pathway in Cancer." Annual Review of Cancer Biology 3, no. 1 (March 4, 2019): 457–78. http://dx.doi.org/10.1146/annurev-cancerbio-030617-050422.
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Fanconi anemia (FA) is a complex genetic disorder characterized by bone marrow failure (BMF), congenital defects, inability to repair DNA interstrand cross-links (ICLs), and cancer predisposition. FA presents two seemingly opposite characteristics: ( a) massive cell death of the hematopoietic stem and progenitor cell (HSPC) compartment due to extensive genomic instability, leading to BMF, and ( b) uncontrolled cell proliferation leading to FA-associated malignancies. The canonical function of the FA proteins is to collaborate with several other DNA repair proteins to eliminate clastogenic (chromosome-breaking) effects of DNA ICLs. Recent discoveries reveal that the FA pathway functions in a critical tumor-suppressor network to preserve genomic integrity by stabilizing replication forks, mitigating replication stress, and regulating cytokinesis. Homozygous germline mutations (biallelic) in 22 FANC genes cause FA, whereas heterozygous germline mutations in some of the FANC genes (monoallelic), such as BRCA1 and BRCA2, do not cause FA but significantly increase cancer susceptibility sporadically in the general population. In this review, we discuss our current understanding of the functions of the FA pathway in the maintenance of genomic stability, and we present an overview of the prevalence and clinical relevance of somatic mutations in FA genes.
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Seton-Rogers, Sarah. "Stress management by the FA pathway." Nature Reviews Cancer 15, no. 12 (November 13, 2015): 699. http://dx.doi.org/10.1038/nrc4047.
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Taylor, Sarah J., Mark J. Arends, and Simon P. Langdon. "Inhibitors of the Fanconi anaemia pathway as potential antitumour agents for ovarian cancer." Exploration of Targeted Anti-tumor Therapy 1, no. 1 (February 29, 2020): 26–52. http://dx.doi.org/10.37349/etat.2020.00003.
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The Fanconi anaemia (FA) pathway is an important mechanism for cellular DNA damage repair, which functions to remove toxic DNA interstrand crosslinks. This is particularly relevant in the context of ovarian and other cancers which rely extensively on interstrand cross-link generating platinum chemotherapy as standard of care treatment. These cancers often respond well to initial treatment, but reoccur with resistant disease and upregulation of DNA damage repair pathways. The FA pathway is therefore of great interest as a target for therapies that aim to improve the efficacy of platinum chemotherapies, and reverse tumour resistance to these. In this review, we discuss recent advances in understanding the mechanism of interstrand cross-link repair by the FA pathway, and the potential of the component parts as targets for therapeutic agents. We then focus on the current state of play of inhibitor development, covering both the characterisation of broad spectrum inhibitors and high throughput screening approaches to identify novel small molecule inhibitors. We also consider synthetic lethality between the FA pathway and other DNA damage repair pathways as a therapeutic approach.
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O'Connor, Kevin, Sofia Vidal-Cardenas, Haojian Zhang, Alfredo Rodriguez, Lisa Moreau, Chunyu Yang, Michael W. Epperly, et al. "Hyperactive Non-Canonical TGF-β Pathway Signaling in Fanconi Anemia Bone Marrow Stromal Cells Contributes to Growth Suppression." Blood 128, no. 22 (December 2, 2016): 1039. http://dx.doi.org/10.1182/blood.v128.22.1039.1039.
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Abstract Introduction: Fanconi anemia (FA) is the most common inherited bone marrow failure syndrome. FA patients develop bone marrow failure during the first decade of life due to attrition of hematopoietic stem cells (HSCs). FA is caused by autosomal recessive or X-linked mutations in one of nineteen FANC genes, the products of which cooperate in the FA/BRCA DNA repair pathway and regulate cellular resistance to genotoxic DNA cross-linking agents. Although its mechanism is unknown, bone marrow failure in FA may be the result, directly or indirectly, of hyperactivation of cell-autonomous or microenvironmental growth-suppressive pathways induced, in part, due to genotoxic stress. We have recently identified canonical transforming growth factor-β (TGF-β) pathway-mediated growth suppression of HSCs as a cause of bone marrow failure in FA (Zhang H et al, Cell Stem Cell, 2016). We have shown that TGF-β pathway inhibition rescues genotoxic stress, proliferation defects and engraftment defects of FA-deficient HSCs, and ameliorates bone marrow failure in FA mice. Previous studies have suggested that bone marrow stromal fibroblasts from human FA patients and FA pathway-deficient mouse models, like HSCs, are hypersensitive to genotoxic stress and have impaired growth. Here, we therefore investigated the possible suppressive function of the TGF-β pathway in bone marrow stromal cells derived from FA mice and patients with FA. Methods: We established primary stromal cell lines from bone marrow of FA-deficient mice (Fancd2-/- mice) or wild-type sibling control mice. Primary bone marrow stromal cultures were also established from FA patients or normal healthy donors. The stromal cells were characterized and evaluated for growth kinetics, mitomycin C (MMC) sensitivity, chromosome breakage, inflammatory signals and response to the TGF-β inhibitors. CRISPR/Cas-9 technology was used to knockdown specific genes in stromal cells. Results: As expected,the primary bone marrow stromal cells from Fancd2-/- mice exhibited classical FA phenotypes, including hypersensitivity to a DNA cross-linking agent, MMC, and increased MMC-induced chromosomal radials. Fancd2-/- stromal cells also demonstrated a growth defect characterized by an enrichment of cells in G1 and elevated p21 expression. Interestingly, the FA stromal cells derived from FA patients or from Fancd2-/- mice expressed constitutively elevated levels of phosphorylated (activated) ERK1/2 (pERK) compared to control cells. In order to determine whether the factor responsible for inducing ERK1/2 phosphorylation in the murine FA stromal cells was cell-intrinsic or cell-extrinsic, we examined the conditioned media from the stromal cells. Indeed the FA stromal cells secreted a high level of TGF-β cytokine responsible for increased pERK levels, and expressed a high level of secreted TGF-β mRNA. The high level of pERK indicated that the TGF-β non-canonical pathway was hyperactive in the FA stromal cells. Interestingly, CRISPR/Cas9-mediated knockdown of Tgfbr1 or inhibition of the TGF-β pathway by a treatment with a small molecule inhibitor of TGFβR1 or a neutralizing antibody against TGF-β in these cells reduced pERK levels, promoted DNA repair and rescued MMC sensitivity. In addition, a MEK inhibitor also significantly improved the clonogenic growth of Fancd2-/- stromal cells. However, CRISPR/Cas9-mediated knockdown of Smad3, a downstream target of the canonical TGF-β pathway, did not rescue the growth inhibition of FA stromal cells in MMC, further indicating that hyperactivation of the canonical pathway is less relevant to their growth defect. Collectively, these results demonstrated that the hyperactive TGF-β pathway increases phosphorylation of ERK1/2 in FA stromal cells through the non-canonical signaling pathway and impairs their growth after genotoxic stress. Conclusions: The primary FA bone marrow stromal cells exhibit hyperactive non-canonical TGF-β pathway signaling and blocking this pathway improves their growth under genotoxic stress. The TGF-β signaling pathway-mediated growth suppression in bone marrow stromal cells may account, at least in part, for defective microenvironment, impaired HSC function and bone marrow failure in FA. This work suggests that the TGF-β signaling pathway may be a potential therapeutic target for the treatment of bone marrow failure in FA. Disclosures Shimamura: TransCellular Therapeutics: Other: Husband is founder. No revenue to date.; Novartis: Other: In discussion regarding possible clinical trial for aplastic anemia; Glaxo Smith Kline: Honoraria.
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Milletti, Giacomo, Luisa Strocchio, Daria Pagliara, Katia Girardi, Roberto Carta, Angela Mastronuzzi, Franco Locatelli, and Francesca Nazio. "Canonical and Noncanonical Roles of Fanconi Anemia Proteins: Implications in Cancer Predisposition." Cancers 12, no. 9 (September 20, 2020): 2684. http://dx.doi.org/10.3390/cancers12092684.
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Fanconi anemia (FA) is a clinically and genetically heterogeneous disorder characterized by the variable presence of congenital somatic abnormalities, bone marrow failure (BMF), and a predisposition to develop cancer. Monoallelic germline mutations in at least five genes involved in the FA pathway are associated with the development of sporadic hematological and solid malignancies. The key function of the FA pathway is to orchestrate proteins involved in the repair of interstrand cross-links (ICLs), to prevent genomic instability and replication stress. Recently, many studies have highlighted the importance of FA genes in noncanonical pathways, such as mitochondria homeostasis, inflammation, and virophagy, which act, in some cases, independently of DNA repair processes. Thus, primary defects in DNA repair mechanisms of FA patients are typically exacerbated by an impairment of other cytoprotective pathways that contribute to the multifaceted clinical phenotype of this disease. In this review, we summarize recent advances in the understanding of the pathogenesis of FA, with a focus on the cytosolic noncanonical roles of FA genes, discussing how they may contribute to cancer development, thus suggesting opportunities to envisage novel therapeutic approaches.
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Longerich, Simonne, Jian Li, Yong Xiong, Patrick Sung, and Gary M. Kupfer. "Stress and DNA repair biology of the Fanconi anemia pathway." Blood 124, no. 18 (October 30, 2014): 2812–19. http://dx.doi.org/10.1182/blood-2014-04-526293.
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Abstract Fanconi anemia (FA) represents a paradigm of rare genetic diseases, where the quest for cause and cure has led to seminal discoveries in cancer biology. Although a total of 16 FA genes have been identified thus far, the biochemical function of many of the FA proteins remains to be elucidated. FA is rare, yet the fact that 5 FA genes are in fact familial breast cancer genes and FA gene mutations are found frequently in sporadic cancers suggest wider applicability in hematopoiesis and oncology. Establishing the interaction network involving the FA proteins and their associated partners has revealed an intersection of FA with several DNA repair pathways, including homologous recombination, DNA mismatch repair, nucleotide excision repair, and translesion DNA synthesis. Importantly, recent studies have shown a major involvement of the FA pathway in the tolerance of reactive aldehydes. Moreover, despite improved outcomes in stem cell transplantation in the treatment of FA, many challenges remain in patient care.
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Parmar, Kalindi, Patrizia Vinciguerra, Susana Godinho, Abigail Hamilton, David Pellman, and Alan D. D'Andrea. "Cytokinesis Failure In Fanconi Anemia Pathway Deficient Hematopoietic Cells." Blood 116, no. 21 (November 19, 2010): 878. http://dx.doi.org/10.1182/blood.v116.21.878.878.
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Abstract Abstract 878 Fanconi Anemia (FA) is a human genomic instability disorder characterized by progressive bone marrow failure, congenital abnormalities and high predisposition to cancer. Bone marrow failure in FA children is attributed partly to the excessive apoptosis and subsequent failure of the hematopoietic stem cell compartment. Understanding the mechanisms of bone marrow failure may allow better diagnosis and treatment for FA and other aplastic anemia patients. There are fourteen known Fanconi Anemia genes (A, B, C, D1, D2, E, F, G, I, J, L, M, N, O). The FA pathway, regulated by these FA gene products, mediates DNA repair and promotes normal cellular resistance to DNA crosslinking agents. Recent studies suggest that besides maintaining genomic stability, the FA pathway may also play a role in mitosis since FANCD2 and FANCI, the two key FA proteins, are localized to the extremities of ultra-fine DNA bridges (UFBs) linking sister chromatids during cell division (Chan et al, Nat Cell Biol, 11:753-760, 2009; Naim and Rosselli, Nat Cell Biol, 11:761-768, 2009). Whether FA proteins play a direct role in cell division is still unclear. To dissect the mechanisms of bone marrow failure in FA, we have investigated the requirement of FA pathway during mitosis. Initially, we investigated the number of DNA bridges occurring during mitosis in FA-deficient and proficient cells by immunofluorescence and Hoechst staining. FA-deficient patient cell lines (FANCG-deficient and FANCD1/BRCA2-deficient cells) as well as Hela cells with shRNA-mediated knockdown of the FA pathway, displayed an increase in UFBs compared to the FA proficient cells during mitosis. The UFBs were coated by BLM (the RecQ helicase mutated in Bloom syndrome) in early mitosis. In contrast, the FA protein, FANCM, was recruited to the bridges at a later stage. Since the DNA bridges occluding the cleavage furrow potentially induce cytokinesis failure, we assessed FA-deficient cells for multinucleation. The increased number of DNA bridges correlated with a higher rate of binucleated cells in FA deficient Hela cell lines and FA patient-derived fibroblast cells. Moreover, an increase in binucleated cells was also detectable in FA-deficient primary murine bone marrow hematopoietic stem cells (Fancd2-/- cells and Fancg-/- cells) compared to the wild-type cells undergoing proliferation and in FA patient-derived bone marrow stroma cells compared to the stroma cells from normal human bone marrow. Interestingly, the increase in binucleated cells in FA-deficient murine hematopoietic stem cells correlated with the increase in apoptotic cells. Binuclearity, scored by immunostaining for microtubules and Hoechst staining for DNA, was the result of cytokinesis failure as observed by live cell imaging. Therefore, we investigated whether the FA-deficient cells are sensitive to the cytokinesis inhibitors. FA-deficient murine bone marrow lineage negative cells (Fancd2-/- cells) or FA human fibroblast cells were exposed to VX-680 (an inhibitor of Aurora kinases regulating cytokinesis) in culture for 72 hrs and cell survival was assessed. VX-680 caused increased toxicity (reduced cell viability and increased apoptosis) on FA-deficient cells in comparison to the wild-type cells. Enhanced inhibition of clonogenic growth of murine FA-deficient bone marrow cells (Fancd2-/- cells) compared to the wild-type cells was also observed by exposure to VX-680. These data indicated that FA pathway-deficient hematopoietic cells are hypersensitive to cytokinesis inhibitors. Collectively, our results underscore the importance of the FA pathway in mitosis and suggest that the cytokinesis failure observed in FA deficient hematopoietic cells could contribute to bone marrow failure in Fanconi anemia patients. Disclosures: No relevant conflicts of interest to declare.
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Soulier, Jean, Thierry Leblanc, Jérôme Larghero, Hélène Dastot, Akiko Shimamura, Philippe Guardiola, Hélène Esperou, et al. "Detection of somatic mosaicism and classification of Fanconi anemia patients by analysis of the FA/BRCA pathway." Blood 105, no. 3 (February 1, 2005): 1329–36. http://dx.doi.org/10.1182/blood-2004-05-1852.
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AbstractFanconi anemia (FA) is characterized by congenital abnormalities, bone marrow failure, chromosome fragility, and cancer susceptibility. Eight FA-associated genes have been identified so far, the products of which function in the FA/BRCA pathway. A key event in the pathway is the monoubiquitination of the FANCD2 protein, which depends on a multiprotein FA core complex. In a number of patients, spontaneous genetic reversion can correct FA mutations, leading to somatic mosaicism. We analyzed the FA/BRCA pathway in 53 FA patients by FANCD2 immunoblots and chromosome breakage tests. Strikingly, FANCD2 monoubiquitination was detected in peripheral blood lymphocytes (PBLs) in 8 (15%) patients. FA reversion was further shown in these patients by comparison of primary fibro-blasts and PBLs. Reversion was associated with higher blood counts and clinical stability or improvement. Once constitutional FANCD2 patterns were determined, patients could be classified based on the level of FA/BRCA pathway disruption, as “FA core” (upstream inactivation; n = 47, 89%), FA-D2 (n = 4, 8%), and an unidentified downstream group (n = 2, 4%). FA-D2 and unidentified group patients were therefore relatively common, and they had more severe congenital phenotypes. These results show that specific analysis of the FA/BRCA pathway, combined with clinical and chromosome breakage data, allows a comprehensive characterization of FA patients.
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Zhang, Haojian, David Kozono, Kevin O'Connor, Alix Rousseau, Lisa Moreau, Emily Gaudiano, Joel S. Greenberger, et al. "TGF-β Pathway Inhibition Rescues the Function of Hematopoietic Stem and Progenitor Cells Derived from Patients with Fanconi Anemia." Blood 126, no. 23 (December 3, 2015): 297. http://dx.doi.org/10.1182/blood.v126.23.297.297.
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Abstract Introduction: Fanconi anemia (FA) is the most common inherited bone marrow failure syndrome. FA patients develop bone marrow failure during the first decade of life, and frequently require an allogeneic or unrelated donor bone marrow transplant. FA patients also develop other hematologic manifestations, including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) due to clonal evolution. FA is caused by biallelic mutation in one of eighteen FANC genes, the products of which cooperate in the FA/BRCA DNA repair pathway and regulate cellular resistance to DNA cross-linking agents. Bone marrow failure in FA is attributable to an impaired hematopoietic stem and progenitor cell (HSPC) pool. HSPCs in FA patients and FA mice exhibit reduced cell number and compromised stem cell function. Recent studies suggest that bone marrow failure in FA and impaired HSPC function result from the genotoxicity of endogenous cross-linking agents or from physiological stress. A greater understanding of the mechanisms of impairment of HSPC function could improve the therapeutic options for FA patients. Using a whole genome-wide shRNA screen, we have recently identified that the canonical transforming growth factor-β (TGF-β) pathway plays an important growth suppressive role in FA and targeting this pathway can reduce the genotoxic stress-induced growth inhibition of FA cells. Here, we investigated the possible suppressive function of the TGF-β pathway in HSPCs derived from patients with FA. Methods: We performed in vitro colony-forming assays using primary FA patient- derived bone marrow CD34+ cells which were either transduced with shRNA targeting SMAD3 or treated with the anti-human TGF-β neutralizing antibody GC1008. FA-like HSPCs were generated by stably knocking down FANCD2 with lentivirus encoded shRNA in primary human cord blood CD34+ cells. An in vivo engraftment assay was performed by transplanting the FA-like HSPCs into irradiated NSG mice. Results: The primary human FA bone marrow cells displayed elevated mRNA expression of multiple TGF-β pathway components. The TGF-β pathway inhibition, by knockdown of SMAD3 or anti-human TGF-β neutralizing antibody GC1008, rescued the in vitro clonogenic defects of primary CD34+ cells from bone marrow of five different FA patients. Similarly, the TGF-β pathway disruption by depletion of SMAD3 or GC1008 antibody in primary FA-like HSPCs, also rescued their clonogenic defect, and partially restored genotoxic stress-induced growth inhibition. Further, as the very low number of CD34+ cells in FA patients did not allow efficient xenograft assay to analyze in vivo clonogenicity, we performed a surrogate in vivo xenograft assay using FA-like primary CD34+ cells. Importantly, blockade of the TGF-β pathway by GC1008 antibody treatment enhanced the engraftment potential of primary FA-like CD34+ cells in vivo. Collectively, these results demonstrated that increased TGF-β pathway signaling impairs the hematopoietic function of primary human FA HSPCs. Conclusions: The TGF-β pathway signaling is increased in primary FA patient-derived hematopoietic cells and blockade of this pathway can restore the function of human FA-deficient primary HSPCs. The TGF-β signaling pathway-mediated growth suppression may account, at least in part, for bone marrow failure in FA. This work suggests that the TGF-β signaling pathway provides a novel therapeutic target for the treatment of bone marrow failure in FA. Disclosures No relevant conflicts of interest to declare.
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Levitus, Marieke, Hans Joenje, and Johan P. de Winter. "The Fanconi Anemia Pathway of Genomic Maintenance." Analytical Cellular Pathology 28, no. 1-2 (January 1, 2006): 3–29. http://dx.doi.org/10.1155/2006/974975.
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Fanconi anemia (FA), a recessive syndrome with both autosomal and X-linked inheritance, features diverse clinical symptoms, such as progressive bone marrow failure, hypersensitivity to DNA cross-linking agents, chromosomal instability and susceptibility to cancer. At least 12 genetic subtypes have been described (FA-A, B, C, D1, D2, E, F, G, I, J, L, M) and all except FA-I have been linked to a distinct gene. Most FA proteins form a complex that activates the FANCD2 protein via monoubiquitination, while FANCJ and FANCD1/BRCA2 function downstream of this step. The FA proteins typically lack functional domains, except for FANCJ/BRIP1 and FANCM, which are DNA helicases, and FANCL, which is probably an E3 ubiquitin conjugating enzyme. Based on the hypersensitivity to cross-linking agents, the FA proteins are thought to function in the repair of DNA interstrand cross-links, which block the progression of DNA replication forks. Here we present a hypothetical model, which not only describes the assembly of the FA pathway, but also positions this pathway in the broader context of DNA cross-link repair. Finally, the possible role for the FA pathway, in particular FANCF and FANCB, in the origin of sporadic cancer is discussed.
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Oda, Tsukasa, Toshiya Hayano, Hidenobu Miyaso, Nobuhiro Takahashi, and Takayuki Yamashita. "Hsp90 regulates the Fanconi anemia DNA damage response pathway." Blood 109, no. 11 (June 1, 2007): 5016–26. http://dx.doi.org/10.1182/blood-2006-08-038638.
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Abstract Heat shock protein 90 (Hsp90) regulates diverse signaling pathways. Emerging evidence suggests that Hsp90 inhibitors, such as 17-allylamino-17-demethoxygeldanamycin (17-AAG), enhance DNA damage-induced cell death, suggesting that Hsp90 may regulate cellular responses to genotoxic stress. However, the underlying mechanisms are poorly understood. Here, we show that the Fanconi anemia (FA) pathway is involved in the Hsp90-mediated regulation of genotoxic stress response. In the FA pathway, assembly of 8 FA proteins including FANCA into a nuclear multiprotein complex, and the complex-dependent activation of FANCD2 are critical events for cellular tolerance against DNA cross-linkers. Hsp90 associates with FANCA, in vivo and in vitro, in a 17-AAG–sensitive manner. Disruption of the FANCA/Hsp90 association by cellular treatment with 17-AAG induces rapid proteasomal degradation and cytoplasmic relocalization of FANCA, leading to impaired activation of FANCD2. Furthermore, 17-AAG promotes DNA cross-linker–induced cytotoxicity, but this effect is much less pronounced in FA pathway-defective cells. Notably, 17-AAG enhances DNA cross-linker–induced chromosome aberrations. In conclusion, our results identify FANCA as a novel client of Hsp90, suggesting that Hsp90 promotes activation of the FA pathway through regulation of intracellular turnover and trafficking of FANCA, which is critical for cellular tolerance against genotoxic stress.
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Chlon, Timothy M., Elizabeth E. Hoskins, Sonya Ruiz-Torres, Christopher N. Mayhew, Kathryn A. Wikenheiser-Brokamp, Stella M. Davies, Parinda A. Mehta, Kasiani C. Myers, James M. Wells, and Susanne I. Wells. "Inducible Loss of the Fanconi Anemia Pathway in iPSC Causes Rapid Cell Cycle Arrest and Apoptosis through ATM/ATR and p53 Signaling." Blood 124, no. 21 (December 6, 2014): 3528. http://dx.doi.org/10.1182/blood.v124.21.3528.3528.
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Abstract As the source of all cells in the developing embryo proper, embryonic stem cells (ESC) bear the unique responsibility to prevent mutations from being propagated throughout the entire organism and the germ line. It is likely for this reason that ESC and induced pluripotent stem cells (iPSC) maintain a dramatically lower mutation frequency than cultured somatic cells. Multiple mechanisms for this enhanced genomic surveillance have been proposed, including hypersensitivity of DNA damage response signaling pathways and increased activity of error-free DNA repair pathways, such as homologous recombination. However, the effect of loss of function of DNA repair pathways in these cells remains poorly understood. The Fanconi Anemia (FA) pathway is a DNA repair pathway that is required for the repair of DNA interstrand crosslink damage and also promotes repair of DNA double-strand breaks by homologous recombination . Genetic defects in this pathway cause a disease characterized by bone marrow failure and extreme cancer incidence. Several recent studies have revealed that the FA pathway is required for efficient somatic cell reprogramming to iPSC and suggest that FA cells undergo cell death during this process. Another recent study found that the growth of FA patient-specific iPSC was attenuated with a G2/M arrest when compared to control iPSC, suggesting that these cells arrest upon failed DNA repair. In this study, we sought to determine the effects of acute loss of function of the FA pathway in iPSC through the generation of FA patient-derived iPSC with inducible complementation of the defective FA gene. Fibroblasts were cultured from skin biopsies of multiple FA patients and transduced with a lentiviral vector expressing the complementing FA gene product under DOX-inducible control. Cells were then reprogrammed to iPSC using episomal transfection. These cells formed iPSC colonies only when reprogramming was carried out in the presence of DOX, confirming that the FA pathway is required for efficient reprogramming. Once cell lines were obtained, DOX-dependent FA functionality was verified based on FANCD2 monoubiquitination and nuclear focus formation after treatment with DNA damaging agents. We then cultured the iPSC for extended periods of time in the presence and absence of DOX. Interestingly, the cultures underwent profound cell death and cell cycle arrest within 7 days of DOX-withdrawal and completely failed to expand after one passage. EdU cell cycle analysis confirmed cell cycle arrest in the G2/M phase. Furthermore, cleaved caspase 3 staining confirmed that the number of apoptotic cells increased by 3-fold in the -DOX culture. Despite these effects, cells cultured in both the presence and absence of DOX formed teratomas in nude mice, thus indicating the maintenance of full differentiation capacity in the absence of the FA pathway. In order to determine the mechanisms underlying G2/M arrest and cell death, expression of p53 and its target genes was detected by both western blot analysis and qRT-PCR. Only a slight increase in p53 activation was observed by 7 days post DOX-withdrawal. Furthermore, knockdown of p53 resulted in rescue from apoptosis to normal levels but not rescue from cell cycle arrest. Increased ATM and ATR DNA damage sensor kinase activities were also detected in –DOX cells, concominant with increased phosphorylation of the ATM-target Chk2 and reduced abundance of the G2/M checkpoint protein CDC25A. These results reveal hyperactive DNA damage responses upon FA loss which may underlie the attenuated cell cycle progression of FA-iPSC independent of p53. Remarkably, effects in this FA model system appear equivalent to those responsible for the depletion of HSC in the bone marrow of FA patients. Thus, iPSC models may be useful for future studies of the mechanisms underlying FA stem cell arrest and for the development of therapeutics that alleviate these phenotypes. Disclosures No relevant conflicts of interest to declare.
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Medhurst, Annette L., El Houari Laghmani, Jurgen Steltenpool, Miriam Ferrer, Chantal Fontaine, Jan de Groot, Martin A. Rooimans, et al. "Evidence for subcomplexes in the Fanconi anemia pathway." Blood 108, no. 6 (September 15, 2006): 2072–80. http://dx.doi.org/10.1182/blood-2005-11-008151.
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AbstractFanconi anemia (FA) is a genomic instability disorder, clinically characterized by congenital abnormalities, progressive bone marrow failure, and predisposition to malignancy. Cells derived from patients with FA display a marked sensitivity to DNA cross-linking agents, such as mitomycin C (MMC). This observation has led to the hypothesis that the proteins defective in FA are involved in the sensing or repair of interstrand cross-link lesions of the DNA. A nuclear complex consisting of a majority of the FA proteins plays a crucial role in this process and is required for the monoubiquitination of a downstream target, FANCD2. Two new FA genes, FANCB and FANCL, have recently been identified, and their discovery has allowed a more detailed study into the molecular architecture of the FA pathway. We demonstrate a direct interaction between FANCB and FANCL and that a complex of these proteins binds FANCA. The interaction between FANCA and FANCL is dependent on FANCB, FANCG, and FANCM, but independent of FANCC, FANCE, and FANCF. These findings provide a framework for the protein interactions that occur “upstream” in the FA pathway and suggest that besides the FA core complex different subcomplexes exist that may have specific functions other than the monoubiquitination of FANCD2.
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Lyakhovich, Alex, and Jordi Surralles. "New Roads to FA/BRCA Pathway: H2AX." Cell Cycle 6, no. 9 (May 2, 2007): 1019–23. http://dx.doi.org/10.4161/cc.6.9.4223.
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D'Andrea, Alan D. "Abstract IA002: Inherited DNA repair defects and premature aging." Cancer Research 83, no. 2_Supplement_1 (January 15, 2023): IA002. http://dx.doi.org/10.1158/1538-7445.agca22-ia002.
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Abstract Fanconi anemia (FA), a DNA repair disorder, is the most frequently inherited bone marrow failure (BMF) syndrome. Patients with FA suffer from early childhood onset of BMF, developmental abnormalities, and heightened susceptibility to solid tumors. FA patients also have a strong predisposition to myelo- dysplastic syndrome (MDS) and acute myeloid leukemia (AML). FA is caused by biallelic mutations in one of 23 FANC genes, whose protein products cooperate in the FA/BRCA DNA repair pathway and regulate cellular resistance to DNA cross-linking agents. Because of their underlying DNA repair defect, FA cells exhibit chromosomal instability and hypersensitivity to genotoxic DNA cross-linking agents, such as mitomycin C (MMC). FA bone marrow (BM) HSPCs are also hypersensitive to oxidative stress and inflammatory cytokines. FA patients and FA cells exhibit many features of Premature Aging. FA patients develop BMF because of HSPC exhaustion. Progressive age-related attrition is observed in CD34+ cell content in FA patients. Additionally, FA patients and FA mice exhibit HSPC functional defects. BMF in FA results from accumulation of DNA damage in HSPCs caused by endogenous cross-linking agents or physiological stress. In response to genotoxic stress, FA HSPCs hyperactivate growth-suppressive pathways, such as the p53 pathway (Ceccaldi et al, Cell Stem Cell, 2012) and the transforming growth factor (TGF-b) pathway (Zhang et al, Cell Stem Cell, 2016), further contributing to BMF. The molecular pathways in FA HSPCs leading to BMF and MDS/AML remain unknown. Although primary HSPCs from BM of FA patients are a useful model system, studying these cells is challenging because of their heterogeneity and low numbers. Sub-populations of HSPCs with heterogeneous transcriptional profiles may co-exist in the BM of FA patients. These subpopulations may include (1) stressed HSPCs sustaining hematopoiesis, (2) HSPCs committed to apoptosis resulting from accumulation of unrepaired DNA damage, and (3) premalignant/malignant cells that eventually lead to clinically detectable MDS or AML. Recently, in order to identify determinants of BMF, we performed single-cell transcriptome profiling of primary HSPCs from FA patients (Rodriguez et al, Cell Stem Cell, 2020). In addition to overexpression of p53 and TGF-b pathway genes, we identified high levels of MYC expression. We correspondingly observed coexistence of distinct HSPC subpopulations expressing high levels of TP53 or MYC in FA bone marrow (BM). MYC-high HSPCs showed significant downregulation of cell adhesion genes, consistent with enhanced egress of FA HSPCs from bone marrow to peripheral blood. We speculate that MYC overexpression impairs HSPC function in FA patients and contributes to exhaustion in FA bone marrow. In my seminar, I will describe the cellular and clinical manifestations of senescence and premature aging in FA patients. Specifically, FA patients exhibit the three major causes of cellular senescence including 1) replicative senescence 2) oncogene-induced senescence (OIS) and 3) stress-induced senescence. Citation Format: Alan D. D'Andrea. Inherited DNA repair defects and premature aging [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA002.
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Ghosal, Kajal, Christian Agatemor, Richard I. Han, Amy T. Ku, Sabu Thomas, and Sudit Mukherjee. "Fanconi Anemia DNA Repair Pathway as a New Mechanism to Exploit Cancer Drug Resistance." Mini-Reviews in Medicinal Chemistry 20, no. 9 (May 27, 2020): 779–87. http://dx.doi.org/10.2174/1389557520666200103114556.
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Chemotherapy employs anti-cancer drugs to stop the growth of cancerous cells, but one common obstacle to the success is the development of chemoresistance, which leads to failure of the previously effective anti-cancer drugs. Resistance arises from different mechanistic pathways, and in this critical review, we focus on the Fanconi Anemia (FA) pathway in chemoresistance. This pathway has yet to be intensively researched by mainstream cancer researchers. This review aims to inspire a new thrust toward the contribution of the FA pathway to drug resistance in cancer. We believe an indepth understanding of this pathway will open new frontiers to effectively treat drug-resistant cancer.
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Chlon, Timothy Michael, Susanne I. Wells, Sonya Ruiz-Torres, Matthew Kuhar, and James M. Wells. "Models of Pluripotent and Somatic Stem Cells to Study Tissue-Specific Sensitivities in Fanconi Anemia." Blood 126, no. 23 (December 3, 2015): 168. http://dx.doi.org/10.1182/blood.v126.23.168.168.
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Abstract The Fanconi Anemia (FA) DNA Repair pathway functions through homologous recombination for error-free repair of DNA interstrand crosslinks. Loss of function of this pathway causes a complex genetic disease that is characterized by congenital abnormalities, bone marrow failure (BMF), and extreme incidence of squamous cell carcinomas. BMF is caused by exhaustion of hematopoietic stem and progenitor cells (HSPCs) and is nearly 100% penetrant by age 40 in FA patients, indicating a profound sensitivity of HSPCs to FA pathway deficiency. In contrast, stem cells in other rapidly regenerating tissues, such as the skin and intestine, are not similarly exhausted. Interestingly, squamous epithelium is highly prone to transformation while intestinal epithelium is not. In order to explore the developmental origins of such striking tissue-specific phenotypes in FA patients, we have generated induced pluripotent stem cell (iPSC) lines conditional for FA pathway function (cFA-iPSCs) and used them to derive FA-proficient and deficient in vitro models of diverse tissues. FA patient cells are refractory to reprogramming. To circumvent this defect and prevent the selection of FA-resistant iPSC clones, fibroblasts from 2 FANCA patients were inducibly complemented with a FANCA transgene under the control of a tetracycline-inducible promoter and then were reprogrammed to iPSC. In this way, the FA pathway was functional throughout reprogramming and could then be turned on or off in established iPSC lines by the addition or withdrawal of doxycycline (DOX) to the media. Here, we describe the effect of FA pathway loss on iPSCs, and present preliminary data on iPSC-derived equivalents of three lineages: hematopoietic, squamous, and intestinal. First, functional consequences of FA pathway loss on iPSC pluripotency and self-renewal were examined. Upon withdrawal of DOX from the culture media, the complementing FA transgene was effectively silenced, resulting in loss of FA pathway function within 7 days. FA-deficient iPSCs maintained normal expression of OCT-3/4 and NANOG and formed teratomas in NSG mice, indicating that pluripotency was maintained. However, profound cell cycle arrest and apoptosis were observed under normal in vitro culture conditions within 7 days of DOX-withdrawal, and the iPSCs failed to expand by 2-3 passages. Thus, we concluded that iPSCs require an intact FA pathway for self-renewal in vitro. Mechanistic studies of FA pathway-deficient iPSCs revealed a 10-fold increase in gH2AX foci in the G2-M phase of the cell cycle. This correlated with activated DNA damage response signaling through ATR and CHK1. Inhibition of CHK1 completely restored the growth of FA-deficient iPSCs to that of their FA-proficient counterparts through a remarkable rapid bypass of the G2-M checkpoint. Unexpectedly, cells maintained in CHK1 inhibitor for over 40days accrued few karypotypic abnormalities (<5% of cells), of which most were trisomies, and only 1 cell out of 40 contained translocations. The rarity of deletions and translocations in CHK1 inhibited iPSC suggests that error-free repair still occurs by an unknown mechanism. We next differentiated the cFA-iPSCs into 3D squamous epithelium and intestine with timed-withdrawal of the FA pathway to determine the effect of FA pathway loss on tissue development and homeostasis. Squamous epithelial rafts and intestinal organoids were generated in the presence and absence of DOX using established protocols. These demonstrated that FA pathway loss does not cause gross abnormalities in epithelial tissues, in line with patient phenotypes. We will present the latest results on proliferation, survival, and differentiation of stem and progenitor cells within each tissue. These will include an assessment of epithelial hyperplasia, which has been observed previously in immortalized FA patient keratinocyte-derived organotypic squamous epithelial rafts and in the oral epithelia of FANCD2 knockout mice. Finally, we will present our latest data on the effects of FA deficiency on hematopoietic progenitor cells, which are currently being generated from the cFA-iPSCs. Collectively, these experiments will quantify cell intrinsic sensitivity of pluripotent versus somatic stem cells that reside in diverse tissue types to loss of the FA pathway. The results may inform the development of novel therapeutics to treat FA BMF without increasing disease risk in other tissues. Disclosures No relevant conflicts of interest to declare.
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Landais, Igor, Aiming Sun, Stacie N. Stone, Alexandra Sobeck, James P. Snyder, and Maureen Hoatlin. "A Novel Cell-Free Assay Identifies the Curcumin Analog EF24 as a Potent Inhibitor of the Fanconi Anemia Pathway." Blood 112, no. 11 (November 16, 2008): 2654. http://dx.doi.org/10.1182/blood.v112.11.2654.2654.
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Abstract Objective: The Fanconi anemia (FA) pathway is a DNA damage response network involved in the cellular resistance against DNA interstrand crosslinks (ICLs). A recent study showed that the FA pathway is synthetic lethal with several other DNA repair genes (Kennedy, 2007) such as ATM, NBS1, RAD54B and TP53BP1. Defects in those genes have been linked to a wide range of inherited and sporadic hematological malignancies including B-CLL, ALL, AML, CML, non-Hodgkin lymphoma, mantle cell lymphoma and multiple myeloma. FA pathway inhibitors may therefore selectively kill malignant cells bearing these defects. Curcumin, a natural product, was the first identified FA pathway inhibitor with activity in the micromolar range in cells (Chirnomas, 2006). However, the poor bioavailability of curcumin hinders its clinical efficacy. Identification of a curcumin analog with better activity, bioavailability and low toxicity could overcome this obstacle. We recently developed a cell-free assay for FA pathway function using Xenopus egg extracts to test the activity of curcumin analogs. As a pilot study we evaluated how well the assay identified inhibitors of the FA pathway in human cells. Methods: Fourteen curcumin analogs previously assayed in the NCI anticancer cell line screen (Adams, 2004) were tested for their activity on the FA pathway. Xenopus egg extracts were used to measure the relative inhibitory activity of the analogs on FANCD2 monoubiquitylation (FANCD2-L) and phosphorylation of other DNA damage response proteins. The underlying mechanism of inhibition was explored by testing the integrity of the core complex, the recruitment of the core complex to DNA and chromatin, and analyzing DNA replication and proteasome activity. Activity of several analogs was confirmed in HeLa cells by evaluation of the inhibition of hydroxyurea (HU)-induced FANCD2-L and FANCD2 foci. Results: EF24 (Adams, 2005) and three structurally similar analogs were 10 times more active than curcumin for FANCD2-L inhibition in Xenopus extracts. These analogs inhibited Mre11 phosphorylation at similar concentrations but had no effect on RPA32 and H2AX phosphorylation. In contrast to curcumin, EF24 did not display significant proteasome inhibition activity and did not affect integrity of the core complex or its recruitment to DNA and chromatin, ruling out these mechanisms to explain inhibition of the FA pathway. In HU-treated HeLa cells, EF24 strongly inhibited FANCD2-L and FANCD2 foci with an IC50 of 350 nM, confirming the results observed in Xenopus extracts. Conclusions: EF24 is a more potent FA pathway inhibitor than curcumin both in Xenopus extracts and in human cells, and as such may be effective as a single agent in targeted therapies against hematological malignancies deficient in ATM, NBS1, RAD54B or TP53BP1. In addition, this study demonstrates that Xenopus extracts are a powerful tool to identify and evaluate small molecules that modulate the FA and other DNA damage response pathways.
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Spardy, Nicole, Anette Duensing, Domonique Charles, Nathan Haines, Tomomi Nakahara, Paul F. Lambert, and Stefan Duensing. "The Human Papillomavirus Type 16 E7 Oncoprotein Activates the Fanconi Anemia (FA) Pathway and Causes Accelerated Chromosomal Instability in FA Cells." Journal of Virology 81, no. 23 (September 26, 2007): 13265–70. http://dx.doi.org/10.1128/jvi.01121-07.
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ABSTRACT Fanconi anemia (FA) patients have an increased risk for squamous cell carcinomas (SCCs) at sites of predilection for infection with high-risk human papillomavirus (HPV) types, including the oral cavity and the anogenital tract. We show here that activation of the FA pathway is a frequent event in cervical SCCs. We found that FA pathway activation is triggered mainly by the HPV type 16 (HPV-16) E7 oncoprotein and is associated with an enhanced formation of large FANCD2 foci and recruitment of FANCD2 as well as FANCD1/BRCA2 to chromatin. Episomal expression of HPV-16 oncoproteins was sufficient to activate the FA pathway. Importantly, the expression of HPV-16 E7 in FA-deficient cells led to accelerated chromosomal instability. Taken together, our findings establish the FA pathway as an early host cell response to high-risk HPV infection and may help to explain the greatly enhanced susceptibility of FA patients to squamous cell carcinogenesis at anatomic sites that are frequently infected by high-risk HPVs.
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García-de-Teresa, Benilde, Alfredo Rodríguez, and Sara Frias. "Chromosome Instability in Fanconi Anemia: From Breaks to Phenotypic Consequences." Genes 11, no. 12 (December 21, 2020): 1528. http://dx.doi.org/10.3390/genes11121528.
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Fanconi anemia (FA), a chromosomal instability syndrome, is caused by inherited pathogenic variants in any of 22 FANC genes, which cooperate in the FA/BRCA pathway. This pathway regulates the repair of DNA interstrand crosslinks (ICLs) through homologous recombination. In FA proper repair of ICLs is impaired and accumulation of toxic DNA double strand breaks occurs. To repair this type of DNA damage, FA cells activate alternative error-prone DNA repair pathways, which may lead to the formation of gross structural chromosome aberrations of which radial figures are the hallmark of FA, and their segregation during cell division are the origin of subsequent aberrations such as translocations, dicentrics and acentric fragments. The deficiency in DNA repair has pleiotropic consequences in the phenotype of patients with FA, including developmental alterations, bone marrow failure and an extreme risk to develop cancer. The mechanisms leading to the physical abnormalities during embryonic development have not been clearly elucidated, however FA has features of premature aging with chronic inflammation mediated by pro-inflammatory cytokines, which results in tissue attrition, selection of malignant clones and cancer onset. Moreover, chromosomal instability and cell death are not exclusive of the somatic compartment, they also affect germinal cells, as evidenced by the infertility observed in patients with FA.
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Shimamura, Akiko, Rocio Montes de Oca, John L. Svenson, Nicholas Haining, Lisa A. Moreau, David G. Nathan, and Alan D. D'Andrea. "A novel diagnostic screen for defects in the Fanconi anemia pathway." Blood 100, no. 13 (December 15, 2002): 4649–54. http://dx.doi.org/10.1182/blood-2002-05-1399.
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Fanconi anemia (FA) is an autosomal recessive chromosomal instability syndrome characterized by congenital abnormalities, progressive bone marrow failure, and cancer predisposition. Although patients with FA are candidates for bone marrow transplantation or gene therapy, their phenotypic heterogeneity can delay or obscure diagnosis. The current diagnostic test for FA consists of cytogenetic quantitation of chromosomal breakage in response to diepoxybutane (DEB) or mitomycin C (MMC). Recent studies have elucidated a biochemical pathway for Fanconi anemia that culminates in the monoubiquitination of the FANCD2 protein. In the current study, we develop a new rapid diagnostic and subtyping FA assay amenable for screening broad populations at risk of FA. Primary lymphocytes were assayed for FANCD2 monoubiquitination by immunoblot. The absence of the monoubiquitinated FANCD2 isoform correlated with the diagnosis of FA by DEB testing in 11 known patients with FA, 37 patients referred for possible FA, and 29 healthy control subjects. Monoubiquitination of FANCD2 was normal in other bone marrow failure syndromes and chromosomal breakage syndromes. A combination of retroviral gene transfer and FANCD2 immunoblotting provides a rapid subtyping assay for patients newly diagnosed with FA. These new FA screening assays would allow efficient testing of broad populations at risk.
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Ishiai, Masamichi. "Regulation of the Fanconi Anemia DNA Repair Pathway by Phosphorylation and Monoubiquitination." Genes 12, no. 11 (November 5, 2021): 1763. http://dx.doi.org/10.3390/genes12111763.
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The Fanconi anemia (FA) DNA repair pathway coordinates a faithful repair mechanism for stalled DNA replication forks caused by factors such as DNA interstrand crosslinks (ICLs) or replication stress. An important role of FA pathway activation is initiated by monoubiquitination of FANCD2 and its binding partner of FANCI, which is regulated by the ATM-related kinase, ATR. Therefore, regulation of the FA pathway is a good example of the contribution of ATR to genome stability. In this short review, we summarize the knowledge accumulated over the years regarding how the FA pathway is activated via phosphorylation and monoubiquitination.
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Pannia, Emanuela, Rola Hammoud, Ruslan Kubant, Rebecca Simonian, Zdenka Pausova, Erland Arning, Teodoro Bottiglieri, and G. Harvey Anderson. "High 5MTHF, but Not Folic Acid During Pregnancy, Alters Hypothalamic Regulatory Pathways and Associates with Post-Partum Weight-Gain in Wistar Rat Mothers." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 1230. http://dx.doi.org/10.1093/cdn/nzaa057_046.
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Abstract Objectives 5-methyltetrahydrofolate (5MTHF), the bioactive folate form, has been proposed an alternative supplement to folic acid (FA) due to direct cellular uptake and utilization. In North America, 5MTHF is incorporated into prenatal supplements at the equivalent high dose (1000 µg) as FA and discussion has been raised of its formation into baby formula. Our lab was the first to compare the dose (1X vs high, 5X) and form (FA vs 5MTHF) effects of folate during pregnancy on later-life metabolic health of the Wistar rat mother. Contrary to our hypothesis, 5MTHF diets, independent of dose, led to mothers with 40% greater body weight-gain and higher food intake post-birth compared to FA. The objective of this study was to identify differentially expressed genes and related hypothalamic pathways of mothers fed FA vs 5MTHF diets during pregnancy. Methods Pregnant Wistar rats were fed an AIN-93 G diet with recommended (1X, control, 2 mg/kg diet) or high (5X) FA or equimolar levels of 5MTHF. At birth, a subset of dams were terminated and RNA-seq analysis was performed in the arcuate nucleus of the hypothalamus (ARC), a key regulator of body weight and food intake, in dams fed the high FA and MTHF diets. Results Over 350 differentially expressed genes were identified in the ARC of dams fed high 5MTHF vs FA diets. Combining differential gene expression patterns with reported GO function terms and Kegg pathway analyses, four candidate genes (prolactin hormone receptor, corticotropin releasing hormone receptor, KISS1 peptide and dopamine receptor) were validated by qPCR thus far as plausible contributors to higher body weight-gain and food intake in 5MTHF dams. These genes correspond to neuroactive ligand-receptor interaction pathway (path: hsa04080), associated with metabolic diseases including leptin deficiency and genetic obesity. Other significantly enriched pathways included the retrograde endocannabinoid signalling and morphine addiction pathway. Conclusions High 5MTHF supplementation during pregnancy alters expression of central feeding regulatory pathways in the hypothalamus of the mother, potentially programming post-partum body-weight gain. 5MTHF, at the equivalent dose of FA, may not be the preferred folate form during pregnancy. Funding Sources CIHR-INMD; EP supported by NSERC-CGS D.
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Sobeck, A., S. Stone, and M. E. Hoatlin. "DNA Structure-Induced Recruitment and Activation of the Fanconi Anemia Pathway Protein FANCD2." Molecular and Cellular Biology 27, no. 12 (April 9, 2007): 4283–92. http://dx.doi.org/10.1128/mcb.02196-06.
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ABSTRACT The Fanconi anemia (FA) pathway proteins are thought to be involved in the repair of irregular DNA structures including those encountered by the moving replication fork. However, the nature of the DNA structures that recruit and activate the FA proteins is not known. Because FA proteins function within an extended network of proteins, some of which are still unknown, we recently established cell-free assays in Xenopus laevis egg extracts to deconstruct the FA pathway in a fully replication-competent context. Here we show that the central FA pathway protein, xFANCD2, is monoubiquitinated (xFANCD2-L) rapidly in the presence of linear and branched double-stranded DNA (dsDNA) structures but not single-stranded or Y-shaped DNA. xFANCD2-L associates with dsDNA structures in an FA core complex-dependent manner but independently of xATRIP, the regulatory subunit of xATR. Formation of xFANCD2-L is also triggered in response to circular dsDNA, suggesting that dsDNA ends are not required to trigger monoubiquitination of FANCD2. The induction of xFANCD2-L in response to circular dsDNA is replication and checkpoint independent. Our results provide new evidence that the FA pathway discriminates among DNA structures and demonstrate that triggering the FA pathway can be uncoupled from DNA replication and ATRIP-dependent activation.
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Müller, Lars U. W., Michael D. Milsom, Chad E. Harris, Rutesh Vyas, Kristina M. Brumme, Kalindi Parmar, Lisa A. Moreau, et al. "Overcoming reprogramming resistance of Fanconi anemia cells." Blood 119, no. 23 (June 7, 2012): 5449–57. http://dx.doi.org/10.1182/blood-2012-02-408674.
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Abstract Fanconi anemia (FA) is a recessive syndrome characterized by progressive fatal BM failure and chromosomal instability. FA cells have inactivating mutations in a signaling pathway that is critical for maintaining genomic integrity and protecting cells from the DNA damage caused by cross-linking agents. Transgenic expression of the implicated genes corrects the phenotype of hematopoietic cells, but previous attempts at gene therapy have failed largely because of inadequate numbers of hematopoietic stem cells available for gene correction. Induced pluripotent stem cells (iPSCs) constitute an alternate source of autologous cells that are amenable to ex vivo expansion, genetic correction, and molecular characterization. In the present study, we demonstrate that reprogramming leads to activation of the FA pathway, increased DNA double-strand breaks, and senescence. We also demonstrate that defects in the FA DNA-repair pathway decrease the reprogramming efficiency of murine and human primary cells. FA pathway complementation reduces senescence and restores the reprogramming efficiency of somatic FA cells to normal levels. Disease-specific iPSCs derived in this fashion maintain a normal karyotype and are capable of hematopoietic differentiation. These data define the role of the FA pathway in reprogramming and provide a strategy for future translational applications of patient-specific FA iPSCs.
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Dan, Chenchen, Hongjing Pei, Buzhe Zhang, Xuan Zheng, Dongmei Ran, and Changzheng Du. "Fanconi anemia pathway and its relationship with cancer." Genome Instability & Disease 2, no. 3 (June 2021): 175–83. http://dx.doi.org/10.1007/s42764-021-00043-0.
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AbstractFanconi Anemia (FA) is a rare inherited hematological disease, caused by mutations in genes involved in the DNA interstrand crosslink (ICL) repair. Up to date, 22 genes have been identified that encode a series of functionally associated proteins that recognize ICL lesion and mediate the activation of the downstream DNA repair pathway including nucleotide excision repair, translesion synthesis, and homologous recombination. The FA pathway is strictly regulated by complex mechanisms such as ubiquitination, phosphorylation, and degradation signals that are essential for the maintenance of genome stability. Here, we summarize the discovery history and recent advances of the FA genes, and further discuss the role of FA pathway in carcinogenesis and cancer therapies.
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Liu, Hengzhou, Deep Patel, Yifu Chen, Luke T. Roling, and Wenzhen Li. "Elucidating Pathways to Electrochemical Reduction of Furfural Via Tailoring Interfacial Environments Toward Selective Production of Valuable Furanic Chemicals." ECS Meeting Abstracts MA2022-01, no. 56 (July 7, 2022): 2347. http://dx.doi.org/10.1149/ma2022-01562347mtgabs.
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Electrochemical reduction of biomass-derived feedstocks holds great promise to produce value-added chemicals or fuels driven by renewable electricity. However, mechanistic understanding of the aldehyde reduction toward valuable products at the electrode/electrolyte interface at the molecular level is still lacking. Herein, we studied the furfural reduction on Pb electrodes in acid conditions and elucidated the detailed pathways toward three key products: furfuryl alcohol (FA), 2-methylfuran (MF), and hydrofuroin. First, by coupling isotopic labeling and electrokinetics, we revealed that protons (H2O and H3O+) plays an important role in the hydrogenation pathway toward FA and MF. In particular, the study of product-selective kinetic isotopic effect of H/D and the surface property-dependent hydrogenation/deuteration pathway strongly impacted the generation of FA but not MF, which can be attributed to their different formation mechanisms: FA is produced from Langmuir-Hinshelwood pathway that need both adsorbed furfural and hydrogen, but MF produced from Eley-Rideal pathway that need proton directly from the electrolyte. Modifying the double layer by cations with large radii, we further correlated the product selectivity (FA and MF) with interfacial environments (local H3O+ and H2O content, etc). Combined methods, including pulsed electrolysis, electron paramagnetic resonance (EPR) spectroscopy, and DFT calculations, further suggested that the formation of hydrofuroin and FA shared one intermediate. Hydrofuroin is produced through the desorption of the intermediate as ketyl radicals followed by its self-coupling in the electrolyte, while FA is generated from further hydrogenation of that intermediate. The acquired into the electrochemical reduction of the aldehyde group in furfural to alcohol, alkyl, and dimer may be extended to other organic compounds with carbonyl group, such as 5-hydromethylfurfural, toward a sustainable electrochemical manufacturing of higher-valued chemicals from biomass feedstock.
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Rominiyi, Ola, Katie Myers, Natividad Gomez-Roman, Nikita Lad, Dawoud Dar, David Jellinek, Anthony Chalmers, et al. "RDNA-12. THE FANCONI ANAEMIA (FA) PATHWAY AND GLIOBLASTOMA: A NEW FOUNDATION FOR DNA DAMAGE RESPONSE TARGETED COMBINATIONS." Neuro-Oncology 21, Supplement_6 (November 2019): vi209. http://dx.doi.org/10.1093/neuonc/noz175.871.
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Abstract Treatment resistance in glioblastoma is underpinned by highly interconnected DNA damage response (DDR) processes. The FA-pathway is a fundamental DDR process required for the resolution of replication fork impeding lesions, and we have previously shown that it is inactive in normal brain, but is re-activated in glioblastoma, providing a cancer-specific target for combination DDR therapies. Here, we find that elevated FA-pathway gene expression in gliomas is associated with poor survival (-17.1% 5-year OS, p< 0.0001, n=329–REMBRANT). Furthermore, patient-derived glioblastoma stem cell (GSC) populations, which drive therapeutic resistance, display high FA-pathway expression relative to paired bulk tumour cell populations (mean 2.3-fold higher across genes, p=0.0073). We further show that inhibition of a single DDR process (FA-pathway, PARP, ATR or ATM) increases the susceptibility of glioblastoma cell lines and patient-derived GSCs to current adjuvant therapy. Importantly, clinically approved PARP inhibitor (PARPi) monotherapy stimulates robust FANCD2 mono-ubiquitination, supporting a role of FA-pathway activation in response to current DDR-targeted therapy. In clinically-relevant 3D GSC models, simultaneous inhibition of the FA-pathway (FAPi) and PARP or ATR enhanced temozolomide sensitisation compared to a single DDR inhibitor (DDRi). Furthermore, combined FAPi+PARPi consistently conferred radiosensitisation whilst combined FAPi+ATRi led to a profoundly radiosensitising effect; e.g. sensitizer enhancement ratio (SER0.37) of 3.23 (3.03–3.49, 95% CI). Furthermore, comparison of α/β ratio enhancement suggests dual-DDRi strategies fundamentally alter the response of GSCs, whilst single cell gel electrophoresis & immunofluorescence studies suggest FA-pathway based DDRi combinations profoundly delay the resolution of IR-induced DNA strand breaks at 6 hours post-treatment, with increased persistent DNA double strand breaks at 24 hours. In conclusion, simultaneously targeting the FA-pathway and interconnected DDR processes represents an appealing therapeutic strategy. Additionally, constitutive lack of FA pathway function in some tumours, could serve as a novel predictive biomarker for patient response to PARPi and ATRi currently in clinical trials.
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Levitus, Marieke, Martin A. Rooimans, Jûrgen Steltenpool, Nicolle F. C. Cool, Anneke B. Oostra, Christopher G. Mathew, Maureen E. Hoatlin, et al. "Heterogeneity in Fanconi anemia: evidence for 2 new genetic subtypes." Blood 103, no. 7 (April 1, 2004): 2498–503. http://dx.doi.org/10.1182/blood-2003-08-2915.
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Abstract Fanconi anemia (FA) is an autosomal recessive syndrome featuring diverse symptoms including progressive bone marrow failure and early occurrence of acute myeloid leukemia. Nine genetic subtypes have been described for FA (A, B, C, D1, D2, E, F, G, and L), all of which have been connected to distinct disease genes, except B. Here we report on 8 unrelated FA patients who were excluded from the known subtypes on the basis of phenotypic correction or genetic data. Four of these cell lines failed to complement each other in somatic cell hybrids and therefore represent a new group, termed FA-I. The remaining cell lines complemented group FA-I but did not complement each other, thus representing a second new group, FA-J. Both FA-I and -J cell lines were capable of forming an FA multiprotein core complex. This complex is required for activation of the FANCD2 protein by mono-ubiquitination, a key downstream event in the FA pathway. In FA-I cells FANCD2 was not mono-ubiquitinated, indicating a defect upstream in the FA pathway, whereas in FA-J cells FANCD2 was mono-ubiquitinated, indicating a downstream defect. Our results suggest that the FA pathway of genome stabilization may be controlled by at least 11 different genes, including FANCI and FANCJ.
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Nagareddy, Bhavika, Arafat Khan, and Hyungjin Kim. "Acetylation modulates the Fanconi anemia pathway by protecting FAAP20 from ubiquitin-mediated proteasomal degradation." Journal of Biological Chemistry 295, no. 40 (August 6, 2020): 13887–901. http://dx.doi.org/10.1074/jbc.ra120.015288.
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Fanconi anemia (FA) is a chromosome instability syndrome of children caused by inherited mutations in one of FA genes, which together constitute a DNA interstrand cross-link (ICL) repair, or the FA pathway. Monoubiquitination of Fanconi anemia group D2 protein (FANCD2) by the multisubunit ubiquitin E3 ligase, the FA core complex, is an obligate step in activation of the FA pathway, and its activity needs to be tightly regulated. FAAP20 is a key structural component of the FA core complex, and regulated proteolysis of FAAP20 mediated by prolyl cis-trans isomerization and phosphorylation at a consensus phosphodegron motif is essential for preserving the integrity of the FA core complex, and thus FANCD2 monoubiquitination. However, how ubiquitin-dependent FAAP20 degradation is modulated to fine-tune FA pathway activation remains largely un-known. Here, we present evidence that FAAP20 is acetylated by the acetyltransferase p300/CBP on lysine 152, the key residue that when polyubiquitinated results in the degradation of FAAP20. Acetylation or mutation of the lysine residue stabilizes FAAP20 by preventing its ubiquitination, thereby protecting it from proteasome-dependent FAAP20 degradation. Consequently, disruption of the FAAP20 acetylation pathway impairs FANCD2 activation. Together, our study reveals a competition mechanism between ubiquitination and acetylation of a common lysine residue that controls FAAP20 stability and highlights a complex balancing between different posttranslational modifications as a way to refine the FA pathway signaling required for DNA ICL repair and genome stability.
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Ali, Abdullah Mahmood, Arun Pradhan, Thiyam Ramsingh Singh, Changhu Du, Jie Li, Kebola Wahengbam, Elke Grassman, Arleen D. Auerbach, Qishen Pang, and Amom Ruhikanta Meetei. "FAAP20: a novel ubiquitin-binding FA nuclear core-complex protein required for functional integrity of the FA-BRCA DNA repair pathway." Blood 119, no. 14 (April 5, 2012): 3285–94. http://dx.doi.org/10.1182/blood-2011-10-385963.
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Abstract Fanconi anemia (FA) nuclear core complex is a multiprotein complex required for the functional integrity of the FA-BRCA pathway regulating DNA repair. This pathway is inactivated in FA, a devastating genetic disease, which leads to hematologic defects and cancer in patients. Here we report the isolation and characterization of a novel 20-kDa FANCA-associated protein (FAAP20). We show that FAAP20 is an integral component of the FA nuclear core complex. We identify a region on FANCA that physically interacts with FAAP20, and show that FANCA regulates stability of this protein. FAAP20 contains a conserved ubiquitin-binding zinc-finger domain (UBZ), and binds K-63–linked ubiquitin chains in vitro. The FAAP20-UBZ domain is not required for interaction with FANCA, but is required for DNA-damage–induced chromatin loading of FANCA and the functional integrity of the FA pathway. These findings reveal critical roles for FAAP20 in the FA-BRCA pathway of DNA damage repair and genome maintenance.
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van der Vusse, Ger J., Theo Arts, James B. Bassingthwaighte, and Robert S. Reneman. "Intra-cardiac transfer of fatty acids from capillary to cardiomyocyte." PLOS ONE 17, no. 1 (January 28, 2022): e0261288. http://dx.doi.org/10.1371/journal.pone.0261288.
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Blood-borne fatty acids (Fa) are important substrates for energy conversion in the mammalian heart. After release from plasma albumin, Fa traverse the endothelium and the interstitial compartment to cross the sarcolemma prior to oxidation in the cardiomyocytal mitochondria. The aims of the present study were to elucidate the site with lowest Fa permeability (i.e., highest Fa resistance) in the overall Fa trajectory from capillary to cardiomyocyte and the relative contribution of unbound Fa (detach pathway, characterized by the dissociation time constant τAlbFa) and albumin-bound Fa (contact pathway, characterized by the membrane reaction rate parameter dAlb) in delivering Fa to the cellular membranes. In this study, an extensive set of 34 multiple indicator dilution experiments with radiolabeled albumin and palmitate on isolated rabbit hearts was analysed by means of a previously developed mathematical model of Fa transfer dynamics. In these experiments, the ratio of the concentration of palmitate to albumin was set at 0.91. The analysis shows that total cardiac Fa permeability, Ptot, is indeed related to the albumin concentration in the extracellular compartment as predicted by the mathematical model. The analysis also reveals that the lowest permeability may reside in the boundary zones containing albumin in the microvascular and interstitial compartment. However, the permeability of the endothelial cytoplasm, Pec, may influence overall Fa permeability, Ptot, as well. The model analysis predicts that the most likely value of τAlbFa ranges from about 200 to 400 ms. In case τAlbFa is fast, i.e., about 200 ms, the extracellular contact pathway appears to be of minor importance in delivering Fa to the cell membrane. If Fa dissociation from albumin is slower, e.g. τAlbFa equals 400 ms, the contribution of the contact pathway may vary from minimal (dAlb≤5 nm) to substantial (dAlb about 100 nm). In the latter case, the permeability of the endothelial cytoplasm varies from infinite (no hindrance) to low (substantial hindrance) to keep the overall Fa flux at a fixed level. Definitive estimation of the impact of endothelial permeability on Ptot and the precise contribution of the contact pathway to overall transfer of Fa in boundary zones containing albumin requires adequate physicochemical experimentation to delineate the true value of, among others, τAlbFa, under physiologically relevant circumstances. Our analysis also implies that concentration differences of unbound Fa are the driving force of intra-cardiac Fa transfer; an active, energy requiring transport mechanism is not necessarily involved. Membrane-associated proteins may facilitate Fa transfer in the boundary zones containing albumin by modulating the membrane reaction rate parameter, dAlb, and, hence, the contribution of the contact pathway to intra-cardiac Fa transfer.
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Kim, Joon Sung, Se-Hong Kim, Seong Hoon Lim, Sun Im, Bo Young Hong, Jeehae Oh, and Youngkook Kim. "Degeneration of the Inferior Cerebellar Peduncle After Middle Cerebral Artery Stroke." Stroke 50, no. 10 (October 2019): 2700–2707. http://dx.doi.org/10.1161/strokeaha.119.025723.
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Background and Purpose— Deafferentation of the cortico-ponto-cerebellar pathway has been proposed as a key mechanism of crossed cerebellar diaschisis. Although the cerebellum receives afferent stimuli from both cortico-ponto-cerebellar and spinocerebellar pathways, evidence on whether spinocerebellar deafferentation contributes to a hypofunctional cerebellum is lacking. Therefore, we aimed to determine whether changes in the spinocerebellar pathway occur after middle cerebral artery stroke. Methods— Twenty-three patients admitted to our inpatient rehabilitation facility and 23 age-matched healthy controls were retrospectively enrolled. Patients’ functional ambulation category was determined and the Medical Research Council muscle scale test of the lower limb muscles was performed at admission and discharge. The fractional anisotropy (FA) values of the corticospinal tract and the inferior cerebellar peduncle (ICP), as the final route of the dorsal spinocerebellar pathway, were compared between the groups. The FA laterality indices of the ICP and corticospinal tract were calculated as follows: (FA affected −FA unaffected )/(FA affected +FA unaffected ). Pearson correlation analysis and multivariate linear regression models were used to determine the associations between the FA laterality indices and ambulatory function. Results— The FAs of the corticospinal tract and ICP were lower in the patient group than in the control group. The FA laterality index of the corticospinal tract was not correlated with the functional ambulation category or Medical Research Council muscle scale score at admission or discharge. The FA laterality index of the ICP at the pontomedullary junction was positively correlated with the functional ambulation category and Medical Research Council muscle scale scores of all hemiplegic lower limb muscles at admission and discharge. The FA laterality index of the ICP at the pontomedullary junction was independently associated with the functional ambulation category according to the multivariate regression models. Conclusions— ICP degeneration occurs in the subacute and early chronic phase of middle cerebral artery stroke. The lower FA laterality index of the ICP was indicative of poorer ambulatory and lower limb function.
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Sertorio, Mathieu, Surya Amarachintha, Andrew Wilson, and Qishen Pang. "Fancd2 Deficiency Impairs Autophagy Via Deregulating The Ampk/Foxo3a/Akt Pathway." Blood 122, no. 21 (November 15, 2013): 3713. http://dx.doi.org/10.1182/blood.v122.21.3713.3713.
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Abstract Fanconi anemia (FA) is a genetic disease characterized by bone narrow failure and high risk of malignancy. The disease is due to a deficiency in the FA DNA repair pathway. Impaired function of the FA pathway leads to a decrease in survival, self-renewal and function of hematopoietic stem cells (HSCs). Previous reports have shown that FOXO3a directs a protective autophagy program for HSCs. Autophagy is an intracellular degradation system that enables cell to survive during stress like nutriment deprivation or oxidative stress by recycling damage proteins and organelles like mitochondria. Our laboratory has shown that FA-deficient cells are hypersensitive to oxidative stress and that FANCD2/FOXO3a interaction directs anti-oxidative response and cell survival. The FANCD2/FOXO3a axis could play a role in the protective autophagy activity in HSCs. For these reasons, we decided to study autophagy in the context of FANCD2-deficient (FA-D2) human lymphoblast cells exposed to oxidative stress. Interestingly, we observed an impaired activation of autophagy in the FA-D2 cells, detected by LC3-II immunoblot and flow cytometry, compared to FANCD2-corrected (control) cells. We found an increased necroapoptosis as soon as 1 hour after H2O2 treatment in FA-D2 cells. Paradoxically, we observed a profound decrease in the activity of the mTORC1 complex (as determined by S6 and S6k1 phosphorylation) in FA-D2 cells. In order to explain this autophagy deregulation, we determined the activation of AKT known to up-regulate mTORC1 activity. AKT activation (monitored by phospho-ser473) was significantly decreased in FA-D2 cells compared to control cells. Consequently, FOXO3a was over-activated in FA-D2 cells after H2O2 treatment. Consistently, we found markedly increased activation of AMPK known to initiate and sustain FOXO3a activation. Since AKT controls the expression of p62/SQSTM1, a protein involved in autophagy by addressing the damaged proteins/organelles to autophagic vesicles, we next examined the level of p62 in FA-D2 cells. In contradiction with the impaired autophagy in FA-D2 cells, we observed a decrease of p62 protein compared to corrected cells. To ensure that p62 protein decrease was not due to autophagy activity, we examined p62 transcription and found that the level of p62 mRNA was significantly decreased in FA-D2 cells. Our study thus identifies a deregulated AMPK/FOXO3a/AKT pathway in FA hematopoietic cells, and reveals an impaired autophagy process in which over-activated AMPK initiates FOXO3a activation that in turn inactivates AKT leading to down-regulation of p62. Thus, impaired autophagy may play a causal role in the hypersensitivity of FA-deficient cells to oxidative stress. Disclosures: No relevant conflicts of interest to declare.
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Kolinjivadi, Arun Mouli, Wayne Crismani, and Joanne Ngeow. "Emerging functions of Fanconi anemia genes in replication fork protection pathways." Human Molecular Genetics 29, R2 (May 18, 2020): R158—R164. http://dx.doi.org/10.1093/hmg/ddaa087.
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Abstract Germline mutations in Fanconi anemia (FA) genes predispose to chromosome instability syndromes, such as FA and cancers. FA gene products have traditionally been studied for their role in interstrand cross link (ICL) repair. A fraction of FA gene products are classical homologous recombination (HR) factors that are involved in repairing DNA double-strand breaks (DSBs) in an error-free manner. Emerging evidence suggests that, independent of ICL and HR repair, FA genes protect DNA replication forks in the presence of replication stress. Therefore, understanding the precise function of FA genes and their role in promoting genome stability in response to DNA replication stress is crucial for diagnosing FA and FA-associated cancers. Moreover, molecular understanding of the FA pathway will greatly help to establish proper functional assays for variants of unknown significance (VUS), often encountered in clinics. In this short review, we discuss the recently uncovered molecular details of FA genes in replication fork protection pathways. Finally, we examine how novel FA variants predispose to FA and cancer, due to defective replication fork protection activity.
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Li, Landing, Winnie Tan, and Andrew J. Deans. "Structural insight into FANCI–FANCD2 monoubiquitination." Essays in Biochemistry 64, no. 5 (July 29, 2020): 807–17. http://dx.doi.org/10.1042/ebc20200001.
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Abstract The Fanconi anemia (FA) pathway coordinates a faithful repair mechanism for DNA damage that blocks DNA replication, such as interstrand cross-links. A key step in the FA pathway is the conjugation of ubiquitin on to FANCD2 and FANCI, which is facilitated by a large E3 ubiquitin ligase complex called the FA core complex. Mutations in FANCD2, FANCI or FA core complex components cause the FA bone marrow failure syndrome. Despite the importance of these proteins to DNA repair and human disease, our molecular understanding of the FA pathway has been limited due to a deficit in structural studies. With the recent development in cryo-electron microscopy (EM), significant advances have been made in structural characterization of these proteins in the last 6 months. These structures, combined with new biochemical studies, now provide a more detailed understanding of how FANCD2 and FANCI are monoubiquitinated and how DNA repair may occur. In this review, we summarize these recent advances in the structural and molecular understanding of these key components in the FA pathway, compare the activation steps of FANCD2 and FANCI monoubiquitination and suggest molecular steps that are likely to be involved in regulating its activity.
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&NA;. "FA pathway repairs chemoʼs damage to cancer cells." Oncology Times UK 7, no. 3 (March 2010): 4. http://dx.doi.org/10.1097/01.otu.0000398566.79064.ee.
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Suzuki, Naoya, Asuka Hira, Akira Niwa, Megumu Saito, Keitaro Matsuo, Tatsutoshi Nakahata, Minoru Takata, and Miharu Yabe. "Mesodermal Development From Reprogrammed Fanconi Anemia Cells Is Affected by ALDH2 Enzymatic Activity." Blood 120, no. 21 (November 16, 2012): 648. http://dx.doi.org/10.1182/blood.v120.21.648.648.
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Abstract Abstract 648 Introduction Fanconi anemia (FA) is a genome instability disorder with clinical characteristics including progressive bone marrow failure (BMF), developmental abnormalities, and increased occurrence of leukemia and cancer. To date 15 genes have been implicated in FA, and their products form a common DNA repair network often referred to as “FA pathway”. Following DNA damage or replication stress, the FA pathway is activated, leading to the monoubiquitination of FANCD2 and FANCI proteins (the ID complex). The monoubiquitinated ID complex is loaded on damaged chromatin with subnuclear foci formation, and mediates homologous recombination. Since cells derived from FA patients are hypersensitive to treatments that induce DNA interstrand cross-links (ICLs), the FA pathway has been considered to function in ICL repair. However, it still remains unclear what type of endogenous DNA damage is repaired through the FA pathway and is the cause of phenotypes in FA patients. Recent studies have suggested that cells deficient in the FA pathway are also sensitive to formaldehyde and acetaldehyde. Aldehydes may create DNA adducts including ICLs or protein DNA crosslinking. These results raise a possibility that the FA pathway prevents BMF by mitigating genotoxicity due to endogenous aldehydes. It has been known that ALDH2 deficiency resulting from Glu487Lys substitution (A allele) is prevalent in East Asian populations. While the Glu487 form (G allele) is proficient in aldehyde catabolism, even the GA heterozygote displayed strongly reduced catalysis because ALDH2 is a tetrameric enzyme and the variant form can suppress the activity in a dominant negative manner. Therefore some Japanese FA patients are expected to be deficient in ALDH2, providing an opportunity to test role of ALDH2 and aldehyde metabolism in human FA patients. Results and discussion In FA fetus, p53/p21 axis has already activated in fetal liver (Ceccaldi, Cell stem cell, 2012), indicating the possibility that hematopoietic defects in FA patients originates from an earlier developmental stage. Since human hematopoietic system originates from embryonic mesoderm, we set out to estimate the role of ALDH2 and FANCA pathway during early embryogenesis. For this, we reprogrammed somatic cells from a patient with ALDH2 GA genotype and observed their in vitro mesodermal differentiation. We first introduced reprogramming factors into fibroblasts by episomal vectors, and obtained colonies which are morphologically compatible with human induced pluripotent stem cells (iPSCs). These iPSC-like cells (designated as FA-iPLCs) showed close similarity to conventional ES/iPSCs regarding marker gene expressions and differentiation ability into three germ layers. We obtained gene-complemented FA-iPLCs (designated as cFA-iPLCs) for control study. To evaluate the impact of ALDH2 activity on iPSC- or iPLC-derived mesodermal differentiation, we next adapted the previously reported serum-free monolayer culture system. Both FA- and cFA-iPLCs showed similar differentiation manners with conventional embryonic stem cells and iPSCs, and percentages of KDR+ mesodermal progenitors including KDR+CD34+ common hemoangiogenic progenitors were comparable. Notably, ALDH2 agonist Alda1 did increase only FA-iPLC-derived mesodermal progenitors but not cFA-iPLCs. These data supported the hypothesis that mesodermal development towards hematopoietic cells in human can be affected by ALDH2 activity in the absence of FA pathway. To confirm the hypothesis, next we set out to assess whether the variation in ALDH2 affects symptoms in Japanese FA patients. Strikingly, we found that progression of BMF was strongly accelerated in heterozygous carrier of the variant A allele compared to homozygous GG patients. Furthermore we looked at occurrence of leukemia and/or myelodysplasia and the somatic developments. Interestingly, these were not significantly difference between patients with each variation of ALDH2, indicating the possibility that aldehydes affect only in early hematopoietic development, not other mesodermal tissues. Overall, our results from FA-iPLCs and clinical study indicate that the variation in ALDH2 affects the occurrence of bone marrow failure in FA patients, and that hematopoietic defect in FA patients is caused by aldehydes in early mesodermal developmental stage. Disclosures: No relevant conflicts of interest to declare.
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Guo, T., G. Cao, Y. Li, Z. Zhang, J. E. Nör, B. H. Clarkson, and J. Liu. "Signals in Stem Cell Differentiation on Fluorapatite-Modified Scaffolds." Journal of Dental Research 97, no. 12 (July 11, 2018): 1331–38. http://dx.doi.org/10.1177/0022034518788037.
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Previously, we reported that the fluorapatite (FA)–modified polycaprolactone (PCL) nanofiber could be an odontogenic/osteogenic inductive tissue-engineering scaffold by inducing stem cell differentiation and mineralization. The present study aimed to explore which of the signal pathways affected this differentiation and mineralization process. The Human Signal Transduction PathwayFinder RT2 Profiler PCR Array was used to analyze the involvement of potential signal transduction pathways during human dental pulp stem cell (DPSCs) osteogenic differentiation induced by FA-modified PCL nanofiber scaffolds. Based on the results, perturbation studies of the signaling pathways hedgehog, insulin, and Wnt were performed. Moreover, the autophagy process was studied, as indicated by the expression of the microtubule-associated protein 1 light chain 3A/B-II (LC3-II) and the cell osteogenic phenotypic changes. In a comparison of the cells grown on PCL + FA scaffolds and those on PCL-only scaffolds, the transcript expression of BMP2, BMP4, FOXA2, PTCH1, WNT1, and WNT2 (PCR array–labeled signal proteins of the hedgehog pathway); CEBPB, FASN, and HK2 (PCR array–labeled signal proteins of the insulin pathway); and CCND1, JUN, MYC, TCF7, and WISP1 (PCR array–labeled signal proteins of the Wnt pathway) doubled at day 14 when obvious cell osteogenic differentiation occurred. Phenotypically, in all the perturbation groups at day 14, ALP activity, OPN, and autophagy marker LC3-II expression were coincidently decreased. Consistently, no positive alizarin red staining or von Kossa staining was observed in the specimens from these perturbation groups at day 28. The results showed that when obvious cell differentiation occurred at day 14 on PCL + FA control groups, the inhibition of the hedgehog, insulin, and Wnt pathways significantly decreased DPSC osteogenic differentiation and mineralization. The osteogenic differentiation of DPSCs grown on FA-modified PCL scaffolds appeared to be positively modulated by the hedgehog, insulin, and Wnt signal pathways, which were coordinated with and/or mediated by the cell autophagy process.
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Yarde, Danielle N., Lori A. Hazlehurst, Vasco A. Oliveira, Qing Chen, and William S. Dalton. "Bortezomib Enhances Melphalan Response by Altering Fanconi Anemia (FA)/BRCA Pathway Expression and Function." Blood 108, no. 11 (November 16, 2006): 840. http://dx.doi.org/10.1182/blood.v108.11.840.840.
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Abstract The FA/BRCA pathway is involved in DNA damage repair and its importance in oncogenesis has only recently been implicated. Briefly, 8 FA/BRCA pathway family members facilitate the monoubiquitination of FANCD2. Upon monoubiquitination, FANCD2 translocates to the DNA repair foci where it interacts with other proteins to initiate DNA repair. Previously, we reported that the FA/BRCA pathway is upregulated in multiple myeloma cell lines selected for resistance to melphalan (Chen, et al, Blood 2005). Further, reducing FANCF in the melphalan resistant 8226/LR5 myeloma cell line partially reversed resistance, whereas overexpressing FANCF in the drug sensitive 8226/S myeloma line conferred resistance to melphalan. Others have reported, and we have also verified, that bortezomib enhances melphalan response in myeloma cells; however, the mechanism of enhanced melphalan activity in combination with bortezomib has not been reported. Based on our observation that the FA/BRCA pathway confers melphalan resistance, we hypothesized that bortezomib enhances melphalan response by targeting FA/BRCA DNA damage repair pathway genes. To investigate this hypothesis, we first analyzed FA/BRCA gene expression in 8226/S and 8226/LR5 cells treated with bortezomib, using a customized microfluidic card (to detect BRCA1, BRCA2, FANCA, FANCC, FANCD2, FANCE, FANCF, FANCG, FANCL, RAD51 and RAD51C) and q-PCR. Interestingly, we found that low dose (5nM) bortezomib decreased many FA/BRCA pathway genes as early as 2 hours, with maximal decreases seen at 24 hours. Specifically, 1.5- to 2.5-fold decreases in FANCA, FANCC, FANCD2, FANCE and RAD51C were seen 24 hours post bortezomib exposure. Moreover, pre-treatment of myeloma cells with low dose bortezomib followed by melphalan treatment revealed a greater than 2-fold reduction in FANCD2 gene expression levels. We also found that melphalan treatment alone enhanced FANCD2 protein expression and activation (monoubiquitination), whereas the combination treatment of bortezomib followed by melphalan decreased activation and overall expression of FANCD2 protein. Taken together, these results suggest that bortezomib enhances melphalan response in myeloma by targeting the FA/BRCA pathway. Further understanding of the role of the FA/BRCA pathway in determining melphalan response may allow for more customized and effective treatment of myeloma.
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Williams, Stacy A., James B. Wilson, Allison P. Clark, Alyssa N. Mitson-Salazar, Allen E. Bale, Nigel J. Jones, and Gary M. Kupfer. "Functional and Physical Interaction Between the Mismatch Repair and the FA-BRCA Pathways." Blood 116, no. 21 (November 19, 2010): 3370. http://dx.doi.org/10.1182/blood.v116.21.3370.3370.
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Abstract Abstract 3370 Introduction: Fanconi anemia (FA) is a rare genetic disorder characterized by bone marrow failure, an increased risk for cancer and leukemia, and congenital abnormalities. Thirteen FA genes have been identified that when mutated result in hypersensitivity to DNA crosslinking agents. Therefore, components of the FA-BRCA pathway are thought to function in the repair of DNA interstrand crosslinks (ICLs). The monoubiquitylation and chromatin localization of two FA proteins, FANCD2 and FANCI, is considered the hallmark of FA pathway activation. It has been reported that FANCJ interacts with the mismatch repair (MMR) complex MutLα and we have previously shown that FANCD2 binds several mismatch repair proteins in vivo and that MSH2 is required for the monoubiquitylation of FANCD2 and FANCI. Interestingly, mismatch repair deficiency is also associated with leukemia in humans and a defect in hematopoietic repopulation in mouse models, suggesting a possible functional overlap between the FA-BRCA and MMR pathways. Methods: Cell lines used: HeLa, FA-A cell line GM6914 and corrected cell line GM6914 + Flag-FANCA, FA-D2 cell line PD20 and corrected cell lines PD20+Flag-FANCD2 and PD20+FANCD2 K561R, human endometrial adenocarcinoma cell line HEC59 (MSH2-deficient) and corrected cell line HEC59+Ch2, and human colon carcinoma cell line HCT116 (MLH1-deficient) and corrected cell line HCT116+Ch3. Cells were treated with the crosslinking agents mitomycin C (MMC), cisplatin (CDDP), or the alkylating agent temozolomide (TMZ). FANCD2 foci formation was assessed using immunofluorescence. Immunoprecipitation was used to demonstrate interactions between FANCD2, MSH2, and MLH1. Survival assays were performed by crystal violet staining and extraction. Chromosome breakage analysis was performed using metaphase spreads. FANCD2 RNAi flies, spel1-/- flies (MSH2-deficient), and double mutants were treated with diepoxybutane (DEB) and assessed for survival and mutagenicity. Mismatch binding EMSAs were performed using Cy5-labeled matched and mismatched 29-mers. Result: FANCD2 foci formation and chromatin loading is greatly diminished in MSH2-deficient cells, while cells lacking MLH1 show no effect, indicating a requirement for MSH2 in the activation of the FA-BRCA pathway and a possible downstream role for MLH1 in ICL repair. Human and mouse cells lacking MSH2 or human cells lacking MLH1 display increased sensitivity to mitomycin C and cisplatin as compared to their corrected counterparts as well as increased radial formation upon treatment with MMC. Studies in both human cell lines and Drosophila mutants indicate an epistatic relationship between FANCD2 and MSH2 with regards to survival, chromosome breakage, and mutagenicity after treatment with crosslinking agents. MSH2 is required for the interaction between FANCD2 and MLH1, but surprisingly, presence of MLH1 appears to enhance the interaction between FANCD2 and MSH2. Furthermore, the interaction between MSH2 and MLH1 after treatment with MMC is reduced in multiple FA cell lines. FA cell lines also display hypersensitivity to alkylating agents such as temozolomide. These results have led us to examine FA cell lines for a defect in mismatch repair through mismatch binding EMSAs and plasmid-based assays. Conclusion: These data suggest that mismatch repair proteins play a key role in the activation of the FA-BRCA pathway. Conversely, FA proteins appear to be required for interactions between mismatch repair factors and may also be involved in the repair of DNA mismatches, suggesting significant crosstalk between the FA and MMR pathways. Understanding this complex interplay could lead to the development of new therapies for the treatment of patients both with FA and cancer. Disclosures: No relevant conflicts of interest to declare.
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Shain, Kenneth H., Liang Nong, Danielle Yarde, Vasco Oliveira, and William S. Dalton. "Selected Resistance to Topoisomerase II Inhibitors Correlates with the Over Expression of FANCF In a Fanconi Anemia/BRCA DNA Repair Pathway Independent Manner." Blood 116, no. 21 (November 19, 2010): 3372. http://dx.doi.org/10.1182/blood.v116.21.3372.3372.
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Abstract Abstract 3372 Enhanced expression of the Fanconi Anemia (FA)/BRCA DNA repair pathway correlates with melphalan-resistance in multiple myeloma (MM) cell lines. Continued investigation demonstrated a bortezomib sensitive RelB/p50-mediated regulation of the FA/BRCA pathway contributed to the observed melphalan resistance.(Yarde et al 2009) The FA/BRCA pathway represents a co-dependent DNA damage response pathway involving thirteen loss of function complementation groups cloned from FA patients. The key functional event of this pathway is the interdependent mono-ubiquitination (Ub) of FANCD2 and FANCI (ID complex) by the E3 Ub-ligase activity of the FA core complex a multimer consisting of 8 FA (FANCA, B, C, E, F, G, L and M) and three non-FA proteins (FAAP100, FAAP24 and HES1). Formation of the core complex and mono-Ub of the ID complex appears to revolve around the flexible adapter protein FANCF. Nuclear localization of the core complex components requires binding of FANCA/G and FANCC/E subcomplexes to the C- terminal domain (CTD) and NTD domains of FANCF, respectively. This complex associates with FANCM:FAAP24 at sites of interstand crosslinks (ICL) via the FANCM-binding domain of FANCF, culminating in ID complex mono-Ub, recruitment of BRCA1, BRCA2/FANCD1, FANCJ and FANCN, and homologous recombination (HR) repair. Reduced function of this pathway has been associated with increased genomic instability, cancer susceptibility, and increased sensitivity to DNA cross-linking agents in FA. However, as predicted by the role of the FA/BRCA pathway in DNA repair, enhanced expression of the FA/BRCA pathway has been shown to play an important role in resistance to agents requiring HR for ICL repair. We next examined expression of this pathway in models of resistance to DNA damaging agents not predicted to utilize FA/BRCA activity. We screened 8226/Dox40 doxorubicin resistant and 8226/MR20 mitoxantrone resistant MM cell lines for expression of the 12 FA/BRCA pathway members with quantitative PCR (qPCR) using customized micro-fluidic cards. Interestingly, in these models of topoisomerase (topo) II inhibitor resistance qPCR demonstrated a 2.6 (p<0.05) and 1.7 (p<0.05) fold over expression of FANCF mRNA relative to drug sensitive RPMI8226 cells. Importantly, mRNA expression of other the eleven FA/BRCA pathway constituents was not increased relative to sensitive cells. To further characterize the relationship between FANCF and doxorubicin resistance, we examined mRNA and protein expression of FANCF in RMPI8226, 8226/Dox6 and 8226/Dox40 MM cell lines (representing progressive levels of doxorubicin resistance). FANCF qPCR demonstrated a 2 and 4.7 fold increased in mRNA expression in the 8226/Dox6 and 8226/Dox40 cell lines, respectively (p= 0.103 and p= 0.034) suggesting that increasing expression of FANCF correlated with increasing dox resistance. A similar doxorubicin resistance- dependent increase in FANCF protein was demonstrated by Western blot analysis of these cell lines. Consistent with mRNA results, FANCD2 or FANCG protein levels remained unchanged in the doxorubicin resistant versus sensitive cell lines These observations suggest that FANCF may contribute to topoII inhibitor-mediated DNA double strand break repair, a process that primarily thought to involve non-homologous end joining (NHEJ) independent of the FA/BRCA pathway. To determine if FANCF expression alone could facilitate doxorubicin resistance, pQCXIP-control or pQCXIP-FANCF constructs were expressed in RPMI8226 sensitive MM cells. MTT assays demonstrated a greater than 2 fold resistance to doxorubicin in FANCF over expressing cells at 48 and 96 hours (IC50: 1.33 ×10−6 and 5.3×10−9M) as compared to control cells (3.26×10−6 and 1.13×10−8M). Taken together, these results indicate that the flexible adaptor protein FANCF may participate in doxorubicin resistance independently of other FA/BRCA members. However, future studies will be needed to elucidate the nature of FANCF in doxorubicin resistance. Disclosures: No relevant conflicts of interest to declare.
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Vinciguerra, Patrizia, Susana Godinho, Kalindi Parmar, David Pellman, and Alan D'Andrea. "Cytokinesis Failure in Fanconi Anemia Pathway Deficient Murine Hematopoietic Stem Cells." Blood 114, no. 22 (November 20, 2009): 495. http://dx.doi.org/10.1182/blood.v114.22.495.495.
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Abstract Abstract 495 Fanconi Anemia (FA) is a rare recessive chromosomal-instability disorder characterized by congenital malformations, a high predisposition to cancer, and progressive bone marrow failure. FA is genetically heterogeneous and, to date, thirteen FA genes have been identified (FANCA, -B, -C, -D1, -D2, -E, -F, -G, -I, -J, -L, -M, -N). The thirteen encoded FA proteins cooperate in a common DNA repair pathway active during the Synthesis (S) phase of the cell cycle. DNA damage detected during replication results in the monoubiquitination of two FA proteins, FANCD2 and FANCI, that translocate into chromatin-associated DNA repair foci where they colocalize with downstream components of the pathway. Partial colocalization with BLM, the RecQ helicase mutated in Bloom's syndrome, has also been described. How disruption of this pathway leads to bone marrow failure is a critical unanswered question. Interestingly, FA cells also have abnormalities that suggest a defect in mitosis, including micronuclei and multinucleation. The objectives of this study were to 1) investigate the role of the FA pathway in normal mitosis and 2) determine whether defects in this function underlie the bone marrow failure of FA patients. For this study, we used HeLa cells transiently or stably knocked down for FA genes, FA patient derived cell lines and hematopoietic stem cells from Fanconi mice models generated in our laboratory (Fancd2-/- and Fancg-/-). First, a polyclonal antibody was raised against FANCI and, together with an anti-FANCD2 antibody, used to investigate the localization of the FANCD2-I complex throughout the cell cycle by immunostaining. FANCI and FANCD2 colocalized to discrete foci on condensed chromosomes in a population of cells in Mitosis (M) phase, consistent with results of Chan et al. (Replication stress induces sister-chromatid bridging at fragile site loci in mitosis. Nat Cell Biol. 2009;11:753-760), Naim and Rosselli (The FANC pathway and BLM collaborate during mitosis to prevent micro-nucleation and chromosome abnormalities. Nat Cell Biol. 2009;11:761-768). These foci were dependent on an intact FA pathway, but did not localize at centromeres and did not increase when the spindle assembly checkpoint was challenged. By immunofluorescence, we showed an increase in the presence of Hoechst positive DNA bridges and PICH positive / BLM positive DNA bridges (Hoechst positive and negative) in anaphase and telophase of FA deficient cells compared to FA proficient cells. This increase of DNA bridges between separating sister chromatids in FA deficient cells correlated with an increase of multinucleated cells. Multinuclearity, scored by immunostaining for microtubules and Hoechst staining for DNA, was the result of cytokinesis failure as observed by live cell imaging. Furthermore, inhibition of apoptosis increased the number of binucleated cells, suggesting that cytokinesis failure led to apoptosis. Importantly, an increase in binucleated cells was also observed in the hematopoietic stem cells population from Fancd2-/- and Fancg-/- mice, compared to wild-type sibling mice, and this increase correlated with elevated apoptosis in those cells. Based on these new findings, we conclude that the Fanconi pathway is required for normal mitosis and hypothesize that apoptosis induced by cytokinesis failure of hematopoietic stem cells may cause the bone marrow failure commonly found in FA patients. Disclosures: No relevant conflicts of interest to declare.
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Lehto, Jemina, Anna Huguet Ninou, Dimitrios Chioureas, Jos Jonkers, and Nina M. S. Gustafsson. "Targeting CX3CR1 Suppresses the Fanconi Anemia DNA Repair Pathway and Synergizes with Platinum." Cancers 13, no. 6 (March 22, 2021): 1442. http://dx.doi.org/10.3390/cancers13061442.
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The C-X3-C motif chemokine receptor 1 (CX3CR1, fractalkine receptor) is associated with neoplastic transformation, inflammation, neurodegenerative diseases and aging, and the small molecule inhibitor KAND567 targeting CX3CR1 (CX3CR1i) is evaluated in clinical trials for acute systemic inflammation upon SARS-CoV-2 infections. Here we identify a hitherto unknown role of CX3CR1 in Fanconi anemia (FA) pathway mediated repair of DNA interstrand crosslinks (ICLs) in replicating cells. FA pathway activation triggers CX3CR1 nuclear localization which facilitates assembly of the key FA protein FANCD2 into foci. Interfering with CX3CR1 function upon ICL-induction results in inability of replicating cells to progress from S phase, replication fork stalling and impaired chromatin recruitment of key FA pathway factors. Consistent with defective FA repair, CX3CR1i results in increased levels of residual cisplatin-DNA adducts and decreased cell survival. Importantly, CX3CR1i synergizes with platinum agents in a nonreversible manner in proliferation assays including platinum resistant models. Taken together, our results reveal an unanticipated interplay between CX3CR1 and the FA pathway and show for the first time that a clinical-phase small molecule inhibitor targeting CX3CR1 might show benefit in improving responses to DNA crosslinking chemotherapeutics.
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Cheung, Ronald S., Maria Castella, and Toshiyasu Taniguchi. "Disparate Requirements for the Phosphorylation of Distinct Sites on the Fanconi Anemia Group I Protein." Blood 124, no. 21 (December 6, 2014): 358. http://dx.doi.org/10.1182/blood.v124.21.358.358.
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Abstract Fanconi Anemia (FA) is a blood disorder characterized by bone marrow failure, predisposition to hematologic malignancy and sensitivity to interstrand crosslinking agents. Patients with FA carry inherited mutations in any one of at least 16 known Fanconi Anemia Group (FANC) proteins that coordinate to function in a DNA repair pathway (the FA pathway). The activation of this pathway centers on two of these, Fanconi Anemia Group D2 protein (FANCD2) and Fanconi Anemia Group I protein (FANCI), which must undergo both phosphorylation and ubiquitination in order for the pathway to function properly. The latter is catalyzed by the FA core complex ubiquitin ligase, which is composed of 8 other FANC proteins. Previous studies suggest that, in response to DNA damage, FANCI is phosphorylated at multiple sites within its evolutionarily conserved SQ cluster domain (SCD). This process is essential for activation of the canonical FA pathway. Failure of FANCI to phosphorylate inhibits FANCD2 ubiquitination, FANCD2 foci formation and cellular resistance to interstrand crosslinkers. However, while FANCI phosphorylation is important for the FA pathway to function, little is known about how this phosphorylation is regulated. Studies on the regulation of FANCI phosphorylation have largely been limited to chicken DT40 cells. Furthermore, the detection of FANCI phosphorylation has been restricted to an electrophoretic mobility-based method, which provides little information on the biology of specific phosphorylation sites. The objective of our work is to better understand the precise regulation of FANCI SCD phosphorylation, in human cells, at sites that have been established to be functionally significant. By performing mass spectrometry on immunoprecipitated human FANCI protein, we established that the human FANCI SCD is indeed phosphorylated on at least two sites. Each of these sites have been found, through mutagenesis studies, to be involved in FA pathway activation. These two sites have also been implicated, through structural studies, in promoting a stable interaction between FANCI and FANCD2. Using this information, we designed immunogenic phospho-peptides to generate antibodies that specifically detect the phosphorylation of each of these two sites. We used these FANCI phospho-antibodies, together with genetically manipulated human cell culture systems, to study factors that modulate FANCI phosphorylation in the context of the human FA pathway. We first established that these antibodies can be used for both immunoblot and immunofluorescence applications. With immunoblot analysis of cells treated with mitomycin C, we made the interesting observation that the phosphorylation of one of the FANCI sites occurred predominantly in the non-ubiquitinated form of the protein, while the other site was phosphorylated predominantly in the ubiquitinated form. This suggested that the phosphorylation of two distinct FANCI sites occurs at different steps of FA pathway activation. By performing siRNA depletion and biochemical experiments in cultured human cells, we found that the phosphorylation of both sites is at least partially dependent on the Ataxia Telangiectasia and Rad 3 related (ATR) kinase. Surprisingly, we found that only one of these sites could be phosphorylated without prior FANCI/D2 ubiquitination. Phosphorylation of the other site was dependent on both FANCI/D2 ubiquitination and the FA core complex. Therefore, contrary to previous models, we found that both ubiquitination-dependent and -independent phosphorylation sites exist within the FANCI SCD. Different FANCI phosphorylation sites that contribute to FA pathway activation therefore have disparate requirements for their phosphorylation. Until now, studies on the regulation of FANCI phosphorylation have been limited by the lack of available phospho-specific FANCI antibodies. By developing antibodies that can specifically detect the phosphorylation of distinct sites within the functionally important SCD of FANCI, we have established new and critical reagents that provide additional insight into how the human FA pathway is activated. Our results suggest a novel model of FA pathway activation that involves a dynamic interplay between FANCI phosphorylation and FANCI/D2 ubiquitination, and reveal that activation of the FA pathway by FANCI phosphorylation is more complex a process than previously thought. Disclosures No relevant conflicts of interest to declare.