Articles de revues : « Leukaemia, Stem cells, Hypoxia, HIF »

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Gezer, Deniz, Amelie V. Guitart, Milica Vukovic, Chithra Subramani, Karen Dunn, Patrick Pollard, Peter J. Ratcliffe, Tessa L. Holyoake et Kamil Kranc. « HIF-1α Is Not Essential For The Establishment Of MLL-Leukaemic Stem Cells ». Blood 122, n^o 21 (15 novembre 2013) : 3767. http://dx.doi.org/10.1182/blood.v122.21.3767.3767.

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Abstract Haematopoietic stem cells (HSCs) reside in hypoxic niches in the bone marrow (BM) and sustain long-life haematopoiesis. HSCs are largely quiescent, self-renew, undergo apoptosis and generate progenitor cells, which differentiate to multiple blood lineages. The strict regulation of the balance between these fate decisions is essential for haematopoiesis and their dysregulation in HSCs and progenitor cells can result in leukaemic transformation. HSCs and leukemic stem cells (LSCs) are suggested to share the same niche and are in need to adapt to hypoxic conditions. Hypoxia-inducible-factor-1α (HIF-1α) is a key mediator of cellular responses to hypoxia and is important for the maintenance of HSC functions under stressful conditions. Furthermore, in chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML) HIF-1α is essential for LSC maintenance and ablation or knockdown of HIF-1α leads to exhaustion of established LSCs. The aim of this study was to investigate the requirement for HIF-1α in the generation of pre-LSCs and the establishment of LSCs. To investigate the role of HIF-1α in the generation of pre-LSCs we retrovirally transduced haematopoietic stem and progenitor cells (HSPCs) from either WT or HIF1-αfl/fl Vav-iCre with MLL-ENL retroviruses. Next we performed serial re-plating assays under normoxic and hypoxic conditions to generate pre-LSCs. Surprisingly, WT and HIF-1α deficient HSPCs generated comparable numbers of colonies in normoxia and hypoxia (Fig. 1a). In addition no significant difference was found in the immunophenotypic profile of colonies (Figure 1b). Furthermore, microscopic examination indicated that colonies of all genotypes were dense consistent with their transformed shape (Fig. 1c). WT and HIF-1α-deficient pre-LSCs cultured under normoxia and hypoxia had similar cloning efficiency, which is known to directly correlate with the numbers of LSCs in vivo (Fig. 2). These results indicate that HIF-1α is dispensable for the generation of pre-LSCs. To test the role of HIF-1α in establishment of LSCs from pre-LSCs we transplanted pre-LSCs into lethally irradiated mice together with support BM and monitored the mice for disease development. No significant difference was found in disease latency (Fig. 3a) or frequency of LSCs in peripheral blood, bone marrow or spleens (Fig. 3b) indicating that pre-LSCs lacking HIF-1α can efficiently generate LSCs that cause aggressive AML. In conclusion, we provide genetic evidence that HIF-1α is dispensable for the generation of pre-LSCs and the establishment of LSCs from pre-LSCs. These surprising findings, together with published results indicating that HIF-1α is essential for maintenance of LSCs, imply that HIF-1α has different roles at different stages of leukaemic transformation. Further studies are required to explain the distinct roles of HIF-1α in different stages of leukaemogenesis. Disclosures: Ratcliffe: RedOx: Founder Other. Holyoake:Novartis: Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees.

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Tomita, Mariko, Gregg L. Semenza, Canine Michiels, Takehiro Matsuda, Jun-Nosuke Uchihara, Taeko Okudaira, Yuetsu Tanaka, Naoya Taira, Kazuiku Ohshiro et Naoki Mori. « Activation of hypoxia-inducible factor 1 in human T-cell leukaemia virus type 1-infected cell lines and primary adult T-cell leukaemia cells ». Biochemical Journal 406, n^o 2 (13 août 2007) : 317–23. http://dx.doi.org/10.1042/bj20070286.

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HTLV-1 (human T-cell leukaemia virus type 1) is the causative agent for ATL (adult T-cell leukaemia). HTLV-1 Tax can activate the PI3K (phosphoinositide 3-kinase)/Akt signalling pathway, which is responsible for survival of HTLV-1-infected T-cells. HIFs (hypoxia-inducible factors) are transcriptional regulators that play a central role in the response to hypoxia. Overexpression of HIF-1α in many cancers is associated with a poor response to treatment and increased patient mortality. Our objectives in the present study were to investigate whether HIF-1 was activated in HTLV-1-infected T-cells and to elucidate the molecular mechanisms of HIF-1 activation by focusing on the PI3K/Akt signalling pathway. We detected a potent pathway that activated HIF-1 in the HTLV-1-infected T-cells under a normal oxygen concentration. Enhanced HIF-1α protein expression and HIF-1 DNA-binding activity were exhibited in HTLV-1-infected T-cell lines. Knockdown of HIF-1α by siRNA (small interfering RNA) suppressed the growth and VEGF (vascular endothelial growth factor) expression of the HTLV-1-infected T-cell line. HIF-1 protein accumulation and transcriptional activity were enhanced by Tax, which was inhibited by dominant-negative Akt. Importantly, mutant forms of Tax that are defective in activation of the PI3K/Akt pathway failed to induce HIF-1 transcriptional activity. The PI3K inhibitor LY294002 suppressed HIF-1α protein expression, HIF-1 DNA-binding and HIF-1 transcriptional activity in HTLV-1-infected T-cell lines. In primary ATL cells, HIF-1α protein levels were strongly correlated with levels of phosphorylated Akt. The results of the present study suggest that PI3K/Akt activation induced by Tax leads to activation of HIF-1. As HIF-1 plays a major role in tumour progression, it may represent a molecular target for the development of novel ATL therapeutics.

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Choi, Jong Ho, Yun Bin Lee, Jieun Jung, Seong Gyu Hwang, IL-Hoan Oh et Gi Jin Kim. « Hypoxia Inducible Factor-1αRegulates the Migration of Bone Marrow Mesenchymal Stem Cells via Integrinα4 ». Stem Cells International 2016 (2016) : 1–11. http://dx.doi.org/10.1155/2016/7932185.

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Although hypoxic environments have been known to regulate the migratory ability of bone marrow-derived mesenchymal stem cells (BM-MSCs), which is a critical factor for maximizing the therapeutic effect, the underlying mechanisms remain unclear. Therefore, we aimed to confirm the effect of hypoxia-inducible factor-1α(HIF-1α) on the migration of BM-MSCs and to analyze the interaction between HIF-1αand integrin-mediated signals. Hypoxia-activated HIF-1αsignificantly increased BM-MSC migration. The expression of integrinα4was decreased in BM-MSCs by increased HIF-1αunder hypoxia, whereas the expression of Rho-associated kinase 1 (ROCK1) and Rac1/2/3 was increased. After downregulation of HIF-1αby YC-1, which is an inhibitor of HIF-1α, BM-MSC migration was decreased via upregulation of integrinα4and downregulation of ROCK1 and Rac1/2/3. Knockdown of integrinα4by integrinα4siRNA (siITGA4) treatment increased BM-MSC migration by upregulation of ROCK1, Rac1/2/3, and matrix metalloproteinase-2 regardless of oxygen tension. Moreover, siITGA4 treatment increased HIF-1αexpression and augmented the translocation of HIF-1αinto the nucleus under hypoxia. Taken together, the alternative expression of HIF-1αinduced by microenvironment factors, such as hypoxia and integrinα4, may regulate the migration of BM-MSCs. These findings may provide insights to the underlying mechanisms of BM-MSC migration for successful stem cell-based therapy.

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Bernard, Olivier, Florence Jeny, Yurdagül Uzunhan, Elisabetta Dondi, Rahma Terfous, Rabab Label, Angela Sutton et al. « Mesenchymal stem cells reduce hypoxia-induced apoptosis in alveolar epithelial cells by modulating HIF and ROS hypoxic signaling ». American Journal of Physiology-Lung Cellular and Molecular Physiology 314, n^o 3 (1 mars 2018) : L360—L371. http://dx.doi.org/10.1152/ajplung.00153.2017.

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Distal lung diseases, such as pulmonary fibrosis or acute lung injury, are commonly associated with local alveolar hypoxia that may be deleterious through the stimulation of alveolar epithelial cell (AEC) apoptosis. In various murine models of alveolar injury, administration of allogenic human mesenchymal stem cells (hMSCs) exerts an overall protective paracrine effect, limiting lung inflammation and fibrosis. However, the precise mechanisms on lung cells themselves remain poorly understood. Here, we investigated whether hMSC-conditioned medium (hMSC-CM) would protect AECs from hypoxia-induced apoptosis and explored the mechanisms involved in this cytoprotective effect. Exposure of rat primary AECs to hypoxia (1.5% O2 for 24 h) resulted in hypoxia-inducible factor (HIF)-1α protein stabilization, partly dependent on reactive oxygen species (ROS) accumulation, and in a twofold increase in AEC apoptosis that was prevented by the HIF inhibitor 3-(5′-hydroxymethyl-2′-furyl)-1-benzyl-indazole and the antioxidant drug N-acetyl cysteine. Incubation of AECs with hMSC-CM significantly reduced hypoxia-induced apoptosis. hMSC-CM decreased HIF-1α protein expression, as well as ROS accumulation through an increase in antioxidant enzyme activities. Expression of Bnip3 and CHOP, two proapoptotic targets of HIF-1α and ROS pathways, respectively, was suppressed by hMSC-CM, while Bcl-2 expression was restored. The paracrine protective effect of hMSC was partly dependent on keratinocyte growth factor and hepatocyte growth factor secretion, preventing ROS and HIF-1α accumulation.

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Eliasson, Pernilla M., et Jan-Ingvar Jönsson. « A Hypoxic Niche in the Mouse Bone Marrow Diminishes Proliferation and Differentiation of Hematopoietic Stem Cells ». Blood 112, n^o 11 (16 novembre 2008) : 4777. http://dx.doi.org/10.1182/blood.v112.11.4777.4777.

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Abstract In the bone marrow hematopoietic stem cells (HSCs) reside in specialized niches in close contact with stromal cells and endosteal osteoblasts. It is thought that this environment is hypoxic in nature, where HSCs are maintained in a quiescent state to prevent their depletion. Hypoxia stabilizes the transcription factor HIF-1α which triggers angiogenesis as well as genes slowering the cell cycle, promoting cell survival, and leading to a decrease in cellular metabolism. In this study, hypoxic effects of the maintenance of Lin−Sca1+c-kit+* (LSK) cells derived from mouse bone marrow and the involvement of the transcription factor hypoxia inducible factor 1 α (HIF-1α) were investigated. Hypoxic culture conditions led to an increase in numbers of primitive colony-forming progenitor cells and a preferential expansion of immature blast-like appearing cells. Concurrently, the immature c-kit Sca-1 phenotype was better maintained in hypoxia compared to ambient oxygen levels. Moreover, hypoxia decreased the proliferation of HSCs as measured by CFSE or PKH26 staining. This was confirmed by cell cycle analysis, and hypoxic cultivation decreased the percentage of cells in S-phase whereas cells in G0/G1 phase increased. Cells infected with a constitutively active form of HIF-1α showed the same pattern as cells cultured in hypoxia. To verify that the effect is HIF-1α mediated, we silenced HIF-1α in LSK cells with shRNA. The decrease in proliferation in hypoxic cultivation of cells infected with shRNA against HIF-1α was markedly diminished, indicating that HIF-1α play an important role in controlling proliferation of hematopoietic stem cells. These results suggest that a major function of hypoxia is to counteract proliferation and possibly differentiation, thereby sustaining maintenance. Furthermore, hypoxic culture conditions may have beneficial clinical implications for ex vivo purposes and may improve the yields of stem cells. In our ongoing-studies, we are investigating whether HIF-1α and hypoxia is an absolute prerequisite for the proper maintenance of HSCs in the bone marrow.

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Hu, Cheng-Jun, Sangeeta Iyer, Aneesa Sataur, Kelly L. Covello, Lewis A. Chodosh et M. Celeste Simon. « Differential Regulation of the Transcriptional Activities of Hypoxia-Inducible Factor 1 Alpha (HIF-1α) and HIF-2α in Stem Cells ». Molecular and Cellular Biology 26, n^o 9 (1 mai 2006) : 3514–26. http://dx.doi.org/10.1128/mcb.26.9.3514-3526.2006.

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ABSTRACT Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factors (HIFs), HIF-1α and HIF-2α. The HIF-1α and HIF-2α subunits are structurally similar in their DNA binding and dimerization domains but differ in their transactivation domains, implying they may have unique target genes and require distinct transcriptional cofactors. Our previous results demonstrated that HIF-1α and HIF-2α regulate distinct target genes. Here, we report that HIF-2α is not transcriptionally active in embryonic stem (ES) cells, as well as possible inhibition by a HIF-2α-specific transcriptional repressor. Using DNA microarray analysis of hypoxia-inducible genes in wild-type (WT), Hif-1α − / − , and Hif-2α − / − ES cells, we show that HIF-1α induces a large number of both confirmed and novel hypoxia-inducible genes, while HIF-2α does not activate any of its previously described targets. We further demonstrate that inhibition of HIF-2α function occurs at the level of transcription cofactor recruitment to endogenous target gene promoters. Overexpression of WT and, notably, a DNA-binding-defective HIF-2α mutant restores endogenous HIF-2α protein activity, suggesting that ES cells express a HIF-2α-specific corepressor that can be titrated by overexpressed HIF-2α protein. HIF-2α repression may explain why patients with mutations in the VHL tumor suppressor gene display cancerous lesions in specific tissue types.

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Tang, Di, Junhui Zhang, Tiantian Yan, Jingyu Wei, Xupin Jiang, Dongxia Zhang, Qiong Zhang, Jiezhi Jia et Yuesheng Huang. « FG-4592 Accelerates Cutaneous Wound Healing by Epidermal Stem Cell Activation via HIF-1α Stabilization ». Cellular Physiology and Biochemistry 46, n^o 6 (2018) : 2460–70. http://dx.doi.org/10.1159/000489652.

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Background/Aims: Regional hypoxia promptly develops after trauma because of microvascular injury and increased oxygen consumption. This acute hypoxia plays a positive role in early skin wound healing. One of the mechanisms underlying the beneficial effects of acute hypoxia on wound healing may be increased hypoxia-inducible factor-1 (HIF-1α) expression. HIF-1α may affect the wound-healing process through many aspects, including angiogenesis, metabolism, and extra-cellular matrix synthesis and remodelling. Epidermal stem cells (EpSCs) are important participants in wound repair; however, whether these cells are regulated by hypoxia is unclear. This study aimed to elucidate the regulatory mechanism by which hypoxia acts on EpSCs. Methods: CCK8 assays, western blots and live cell station observation were employed to compare the viability, proliferation and motility of EpSCs cultured under normoxic conditions (21% O2) with those cultured under hypoxic conditions (2% O2). Moreover, we used FG-4592 (a prolyl hydroxylase inhibitor that stabilizes HIF-1α in normoxia), KC7F2 (a selective inhibitor of HIF-1α transcription) and siRNA against HIF-1α to regulate HIF-1α expression. Results: Acute hypoxia caused EpSCs to switch from a quiescent state to an activated state with higher viability and motility, as well as an earlier proliferation peak. We demonstrated that the HIF-1 signalling pathway mediated hypoxia-induced activation of EpSCs. Finally, the in vivo experiments showed that exogenous FG-4592 effectively accelerates wound healing, shortens healing times and even induces epidermal hyperplasia. Conclusion: This study demonstrated that both hypoxia and exogenous FG-4592 improve EpSC proliferation and motility by stabilizing HIF-1α, and its results suggest that HIF-1α is an important target through which wound healing can be accelerated and that FG-4592 is a promising new drug for wound repair.

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Chang, Yao-Lung, Shuenn-Dyh Chang, An-Shine Chao, Martin Sieber, Chia-Lung Tsai et Po-Jen Cheng. « Effect of Hypoxia on Glucose Transporter 1 and 3 Gene Expression in Placental Mesenchymal Stem Cells Derived from Growth-Restricted Fetuses ». Genes 13, n^o 5 (25 avril 2022) : 752. http://dx.doi.org/10.3390/genes13050752.

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(1) Background: Glucose is transferred from maternal blood to the fetus by glucose transporters. What is the effect of hypoxia on the gene expression of placenta glucose transporter 1 (GLUT1) and glucose transporter 3 (GLUT3) in growth-restricted fetus is interesting. (2) Methods: The gene expression of GLUT1 and GLUT3 and the protein expression of HIF-1α were evaluated under nonhypoxic conditions and after 4 and 8 h under hypoxic conditions in placental mesenchymal stem cells derived from monochorionic twin pregnancies with selective intrauterine growth restriction. (3) Results: The gene expressions of GLUT1 and GLUT3 under hypoxia conditions were higher in placental mesenchymal stem cells derived from appropriate-for-gestational-age fetuses than in those from selective intrauterine growth-restricted fetuses. However, the protein expression of hypoxia induced factor-1 α (HIF-1α) at hypoxia condition was not lower in placenta mesenchymal stem cells from selective intrauterine growth-restricted fetuses than in placental mesenchymal stem cells from appropriate-for-gestational-age fetuses. (4) Conclusions: Hypoxia-induced upregulation of GLUT1 and GLUT3 expression was decreased in placental mesenchymal stem cells from selective intrauterine growth-restricted fetuses but not due to decreased HIF-1α expression. Selective growth-restricted fetuses have less capacity for hypoxia-induced upregulation of placental glucose transport.

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Chang, Yao-Lung, Shuenn-Dyh Chang, An-Shine Chao, Martin Sieber, Chia-Lung Tsai et Po-Jen Cheng. « Effect of Hypoxia on Glucose Transporter 1 and 3 Gene Expression in Placental Mesenchymal Stem Cells Derived from Growth-Restricted Fetuses ». Genes 13, n^o 5 (25 avril 2022) : 752. http://dx.doi.org/10.3390/genes13050752.

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(1) Background: Glucose is transferred from maternal blood to the fetus by glucose transporters. What is the effect of hypoxia on the gene expression of placenta glucose transporter 1 (GLUT1) and glucose transporter 3 (GLUT3) in growth-restricted fetus is interesting. (2) Methods: The gene expression of GLUT1 and GLUT3 and the protein expression of HIF-1α were evaluated under nonhypoxic conditions and after 4 and 8 h under hypoxic conditions in placental mesenchymal stem cells derived from monochorionic twin pregnancies with selective intrauterine growth restriction. (3) Results: The gene expressions of GLUT1 and GLUT3 under hypoxia conditions were higher in placental mesenchymal stem cells derived from appropriate-for-gestational-age fetuses than in those from selective intrauterine growth-restricted fetuses. However, the protein expression of hypoxia induced factor-1 α (HIF-1α) at hypoxia condition was not lower in placenta mesenchymal stem cells from selective intrauterine growth-restricted fetuses than in placental mesenchymal stem cells from appropriate-for-gestational-age fetuses. (4) Conclusions: Hypoxia-induced upregulation of GLUT1 and GLUT3 expression was decreased in placental mesenchymal stem cells from selective intrauterine growth-restricted fetuses but not due to decreased HIF-1α expression. Selective growth-restricted fetuses have less capacity for hypoxia-induced upregulation of placental glucose transport.

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Carcelén, María, Carlos Velásquez, Veronica Vidal, Olga Gutierrez et Jose L. Fernandez-Luna. « HIF2α Upregulates the Migration Factor ODZ1 under Hypoxia in Glioblastoma Stem Cells ». International Journal of Molecular Sciences 23, n^o 2 (11 janvier 2022) : 741. http://dx.doi.org/10.3390/ijms23020741.

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Background: Glioblastoma (GBM) remains a major clinical challenge due to its invasive capacity, resistance to treatment, and recurrence. We have previously shown that ODZ1 contributes to glioblastoma invasion and that ODZ1 mRNA levels can be upregulated by epigenetic mechanisms in response to hypoxia. Herein, we have further studied the transcriptional regulation of ODZ1 in GBM stem cells (GSCs) under hypoxic conditions and analyzed whether HIF2α has any role in this regulation. Methods: We performed the experiments in three primary GSC cell lines established from tumor specimens. GSCs were cultured under hypoxia, treated with HIF regulators (DMOG, chetomin), or transfected with specific siRNAs, and the expression levels of ODZ1 and HIF2α were analyzed. In addition, the response of the ODZ1 promoter cloned into a luciferase reporter plasmid to the activation of HIF was also studied. Results: The upregulation of both mRNA and protein levels of HIF2α under hypoxia conditions correlated with the expression of ODZ1 mRNA. Moreover, the knockdown of HIF2α by siRNAs downregulated the expression of ODZ1. We found, in the ODZ1 promoter, a HIF consensus binding site (GCGTG) 1358 bp from the transcription start site (TSS) and a HIF-like site (CCGTG) 826 bp from the TSS. Luciferase assays revealed that the stabilization of HIF by DMOG resulted in the increased activity of the ODZ1 promoter. Conclusions: Our data indicate that the HIF2α-mediated upregulation of ODZ1 helps strengthen the transcriptional control of this migration factor under hypoxia in glioblastoma stem cells. The discovery of this novel transcriptional pathway identifies new targets to develop strategies that may avoid GBM tumor invasion and recurrence.

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Yoshida, Kozue, Keita Kirito, Kenneth Kaushansky et Norio Komatsu. « Thrombopoietin (TPO) Regulates HIF-1α Level through Generation of Mitochondrial Reactive Oxygen Species (ROS). » Blood 106, n^o 11 (16 novembre 2005) : 3145. http://dx.doi.org/10.1182/blood.v106.11.3145.3145.

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Abstract Hypoxia inducible factor (HIF)-1 is a master transcriptional regulator for adaptation of cells to hypoxia. In addition to hypoxic responses, HIF-1 also plays an important role in the development of hematopoietic stem cells. Genetic deletion of β subunit of HIF-1 causes impairment of hematopoiesis. Culture of hematopoietic stem cells under hypoxic condition induces elevation of HIF-1α , another subunit of HIF-1, and subsequently enhances the growth of these cells. In our previous work we found that thrombopoietin (TPO), an important and non-redundant cytokine required for normal stem cell development, induces HIF-1α elevation in the TPO-dependent human leukemic cell line UT-7/TPO and in Sca-1+/c-kit+/Gr-1- cells (Kirito, K. et.al. Blood 2005). Under normoxic conditions HIF-1α is hydroxylated on proline residues by prolyl hydroxylase (PHD), which leads to its recognition by the von Hippel-Lindau tumor suppressor protein (pVHL), leading to degradation of HIF-1α . Hypoxia inhibits PHD function, blocking ubiquitination of HIF-1α , stabilizing the protein. We found that TPO controls stability of HIF-1α even under normoxic conditions. However, the mechanism by which TPO controls the stability of the protein remains unclear. Recently, several groups have reported that mitochondrial ROS play crucial roles in stabilization of HIF-1α in response to hypoxia. Disruption of mitochondrial function, either by interfering RNA against complex III of the mitochondrial electron transport chain or genetic elimination of cytochrome c, completely abolished the hypoxia-induced HIF-1α response. Based on these findings we hypothesized that ROS might be involved in TPO-induced HIF-1α elevation. To examine our hypothesis, we first tested whether TPO induced ROS production in UT-7/TPO cells using 2′, 7′-dichlorofluorescein diacetate, a redox sensitive fluorescence dye, and found that the hormone clearly induced ROS production in these cells. Next, we analyzed whether TPO-induced ROS generation is required for accumulation of HIF-1α . Pre-treatment of UT-7/TPO cells with the ROS scavenger catalase completely blocked HIF-1α elevation after TPO treatment. Furthermore, diphenylene iodinium (DPI), an inhibitor for ROS generating flavoenzymes including mitochondrial respiratory complexes, also inhibited the effects of TPO on HIF-1α levels. These results indicate that TPO induced HIF-1α activation is mediated by ROS production. To study the molecular pathway(s) by which TPO affects ROS, we tested the effects of ROS blockade on several known TPO-responsive signaling molecules; neither DPI nor catalase affected the activation of JAK2, STAT5, p38-MAPK or p42/p44-ERK induced by TPO, although AKT activation was blocked. Moreover, LY294002, an inhibitor of PI3-kinase and its activation of AKT also blocked of the HIF-1α response to TPO. Finally, inhibition of mitochondrial function in UT-7/TPO cells with rotenone or oligomycin also inhibited TPO-dependent accumulation of HIF-1α without affecting Jak2 activation. In conclusion, we found that TPO regulates HIF-1α levels through activation of ROS generation within mitochondrial respiratory complexes. We speculate that TPO mimics hypoxia by induction of ROS generation at mitochondria and subsequent elevation of HIF-1α , and regulates important genes for metabolisms and survival of hematopoietic stem cells.

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Papale, Marco, Mariachiara Buccarelli, Cristiana Mollinari, Matteo A. Russo, Roberto Pallini, Lucia Ricci-Vitiani et Marco Tafani. « Hypoxia, Inflammation and Necrosis as Determinants of Glioblastoma Cancer Stem Cells Progression ». International Journal of Molecular Sciences 21, n^o 8 (11 avril 2020) : 2660. http://dx.doi.org/10.3390/ijms21082660.

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Tumor hypoxic microenvironment causes hypoxia inducible factor 1 alpha (HIF-1α) activation and necrosis with alarmins release. Importantly, HIF-1α also controls the expression of alarmin receptors in tumor cells that can bind to and be activated by alarmins. Human tumor tissues possess 1–2% of cancer stem cells (CSCs) residing in hypoxic niches and responsible for the metastatic potential of tumors. Our hypothesis is that hypoxic CSCs express alarmin receptors that can bind alarmins released during necrosis, an event favoring CSCs migration. To investigate this aspect, glioblastoma stem-like cell (GSC) lines were kept under hypoxia to determine the expression of hypoxic markers as well as receptor for advanced glycation end products (RAGE). The presence of necrotic extracts increased migration, invasion and cellular adhesion. Importantly, HIF-1α inhibition by digoxin or acriflavine prevented the response of GSCs to hypoxia alone or plus necrotic extracts. In vivo, GSCs injected in one brain hemisphere of NOD/SCID mice were induced to migrate to the other one in which a necrotic extract was previously injected. In conclusion, our results show that hypoxia is important not only for GSCs maintenance but also for guiding their response to external necrosis. Inhibition of hypoxic pathway may therefore represent a target for preventing brain invasion by glioblastoma stem cells (GSCs).

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Yang, Jinfu, Tao Tang, Feng Li, Wenwu Zhou, Jian Liu, Zhiping Tan, Wei Zheng, Yifeng Yang, Xinmin Zhou et Jianguo Hu. « Experimental Study of the Effects of Marrow Mesenchymal Stem Cells Transfected with Hypoxia-Inducible Factor-1αGene ». Journal of Biomedicine and Biotechnology 2009 (2009) : 1–10. http://dx.doi.org/10.1155/2009/128627.

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Objective.To construct the eukaryotic expression vector hypoxia-inducible factor 1α-pcDNA3.1and to investigate its transfective efficiency into mesenchymal stem cells (MSCs) in vitro and the expression of HIF-1αgene in MSCs.Methods.mRNA of Wistar Rats' myocardial cells was extracted, and cDNA was synthesized with Reverse Transcription Kit, HIF-1αwas amplified by polymerase chain reaction (PCR), and constructed intopcDNA3.1. Transfected HIF-1α-pcDNA3.1into MSCs by liposome mediated method. The expression of HIF-1αin the cells was detected by Western Blot Analysis and ELISA.Results.Eukaryotic expression vector HIF-1α-pcDNA3.1was constructed successfully. Analyzed by flow cytometer, The MSCs' surfaces mark were CD44+, SH3(CD73)+, CD34−, CD45−and the CD44+ cells and SH3(CD73)+ cells were 94.7% and 97.3%, respectively, showing the high purity of the cultured MSCs. After inducing, the cultured MSCs can differentiate into osteoblasts and adipocytes successfully. In HIF-1αgene transfected MSCs, the expression of HIF-1αmRNA and HIF-1αprotein were both increased obviously.Conclusion.HIF-1αwas cloned successfully. HIF-1α-pcDNA3.1can be transfected into MSCs by liposome-mediated method effectively and which resulting stable expression of HIF-1αin transfected MSCs.

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Kučera, Jan, Julie Netušilová, Stanislava Sladeček, Martina Lánová, Ondřej Vašíček, Kateřina Štefková, Jarmila Navrátilová, Lukáš Kubala et Jiří Pacherník. « Hypoxia Downregulates MAPK/ERK but Not STAT3 Signaling in ROS-Dependent and HIF-1-Independent Manners in Mouse Embryonic Stem Cells ». Oxidative Medicine and Cellular Longevity 2017 (2017) : 1–16. http://dx.doi.org/10.1155/2017/4386947.

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Hypoxia is involved in the regulation of stem cell fate, and hypoxia-inducible factor 1 (HIF-1) is the master regulator of hypoxic response. Here, we focus on the effect of hypoxia on intracellular signaling pathways responsible for mouse embryonic stem (ES) cell maintenance. We employed wild-type and HIF-1α-deficient ES cells to investigate hypoxic response in the ERK, Akt, and STAT3 pathways. Cultivation in 1% O2 for 24 h resulted in the strong dephosphorylation of ERK and its upstream kinases and to a lesser extent of Akt in an HIF-1-independent manner, while STAT3 phosphorylation remained unaffected. Downregulation of ERK could not be mimicked either by pharmacologically induced hypoxia or by the overexpression. Dual-specificity phosphatases (DUSP) 1, 5, and 6 are hypoxia-sensitive MAPK-specific phosphatases involved in ERK downregulation, and protein phosphatase 2A (PP2A) regulates both ERK and Akt. However, combining multiple approaches, we revealed the limited significance of DUSPs and PP2A in the hypoxia-mediated attenuation of ERK signaling. Interestingly, we observed a decreased reactive oxygen species (ROS) level in hypoxia and a similar phosphorylation pattern for ERK when the cells were supplemented with glutathione. Therefore, we suggest a potential role for the ROS-dependent attenuation of ERK signaling in hypoxia, without the involvement of HIF-1.

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Hofmann, Nicole A., Anna Ortner, Rodrigo Jacamo, Andreas Reinisch, Katharina Schallmoser, Rokhsareh Rohban, Margareta Frühwirth et al. « A Novel Role for Mesenchymal Stem/Progenitor Cells As Hypoxia Sensors During Initiation of Neo-Vasculogenesis in Vivo ». Blood 120, n^o 21 (16 novembre 2012) : 613. http://dx.doi.org/10.1182/blood.v120.21.613.613.

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Abstract Abstract 613 Background: Hypoxia is a major stimulus of neo-vasculogenesis. Under hypoxic conditions endothelial colony-forming progenitor cells (ECFCs) arrange tubular structures, which can connect to the pre-existing vasculature forming functional perfused vessels. The current view is that mesenchymal stem and progenitor cells (MSPCs) or their pericyte progeny are recruited subsequently to stabilize vessels. So far, clinical applications of endothelial progenitors to restore tissue oxygenation after ischemia, cardiovascular disease or stroke largely failed to meet medical needs. Based on previous work demonstrating patent vessel formation after MSPC/ECFC co-transplantation in vivo (Blood 2009), we hypothesized that MSPCs have a decisive role in the vasculogenic response to hypoxia. Here we show for the first time that ECFCs in hypoxic conditions in vivo strictly require the presence of functional MSPCs not only to stabilize but primarily to initiate neo-vasculogenesis by a hypoxia-inducible transcription factor (HIF)-dependent mechanism. Methods: Adult human ECFCs were isolated from blood and MSPCs from bone marrow aspirates and expanded under humanized culture conditions. Progenitor cell phenotype, long-term proliferation, HIF stabilization, wound repair as well as migratory and vasculogenic functions were monitored under severe hypoxia (1% O2), venous oxygen (5% O2) and standard ambient air culture conditions (20% O2). ECFC and MSPC crosstalk in vivo was studied in immune-deficient NSG mice (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) after subcutaneous transplantation in various extracellular matrices (matrigel, collagen/fibronectin, human platelet lysate gel). Cell type-specific chemical and genetic inhibition of HIF (YC-1, shRNA) was used to delineate the role of hypoxia sensing in MSPCs and ECFCs, respectively, during vasculogenesis in vivo. To determine if downstream target proteins of HIF-1α could substitute for MSPC presence during vasculogenesis, selected growth factors and cytokines were tested. Results: Progenitor proliferation and function in vitro were reduced with declining oxygen levels. ECFCs stabilized hypoxia-inducible factor-1α (HIF-1α) only at 1% O2, while MSPCs stabilized HIF-1α already at 5% O2. In an NSG mouse model, ECFCs transplanted into a hypoxic environment did not stabilize HIF-1α, while transplanted sole MSPCs or MSPCs in co-transplants showed strong nuclear HIF-1α stabilization 1 day after transplantation preceding any vessel formation or perfusion. In the absence of MSPCs, the majority of ECFCs underwent apoptosis within 24h in vivo. Inhibition of HIF-1α stabilization in MSPCs but not in ECFCs significantly abrogated vessel formation in vivo. Blocking the prominent HIF-1α down-stream target vascular endothelial growth factor (VEGF) resulted in the expected inhibition of neo-vasculogenesis. Interestingly, substitution of VEGF alone could not restore vessel formation, neither when injected together with sole ECFCs nor in a model where ECFCs were co-transplanted with HIF-depleted MSPCs. Substitution of a complex mixture of platelet-derived factors in vivo partly restored the vasculogenic function of HIF-depleted MSPCs. Conclusions: MSPCs react to a low oxygen environment by stabilizing HIF-1α earlier and more sensitively than ECFCs. MSPCs promote vessel formation at least in part by rescuing ECFCs from hypoxia-induced apoptosis in the initial phase of vasculogenesis by a HIF-dependent trophic mechanism. Surprisingly, therapeutic vasculogenesis can occur independently of endothelial HIF stabilization. These results argue in favor of MSPC/ECFC co-transplantation as a promising strategy for vascular regenerative therapy. The observation that VEGF alone could not compensate for the vasculogenic competence of pericyte precursors in vivo underlines the complexity of the hypoxia-induced cytokine network. The fact that hypoxia sensing in MSPCs but not in ECFCs is crucial to initiate vascular regeneration supports a shift of focus from endothelial cells to perivascular mesenchymal cells as a therapeutic target in anti-angiogenic therapy. Disclosures: No relevant conflicts of interest to declare.

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Menon, Alessandra, Pasquale Creo, Marco Piccoli, Sonia Bergante, Erika Conforti, Giuseppe Banfi, Pietro Randelli et Luigi Anastasia. « Chemical Activation of the Hypoxia-Inducible Factor Reversibly Reduces Tendon Stem Cell Proliferation, Inhibits Their Differentiation, and Maintains Cell Undifferentiation ». Stem Cells International 2018 (2018) : 1–13. http://dx.doi.org/10.1155/2018/9468085.

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Adult stem cell-based therapeutic approaches for tissue regeneration have been proposed for several years. However, adult stem cells are usually limited in number and difficult to be expanded in vitro, and they usually tend to quickly lose their potency with passages, as they differentiate and become senescent. Culturing stem cells under reduced oxygen tensions (below 21%) has been proposed as a tool to increase cell proliferation, but many studies reported opposite effects. In particular, cell response to hypoxia seems to be very stem cell type specific. Nonetheless, it is clear that a major role in this process is played by the hypoxia inducible factor (HIF), the master regulator of cell response to oxygen deprivation, which affects cell metabolism and differentiation. Herein, we report that a chemical activation of HIF in human tendon stem cells reduces their proliferation and inhibits their differentiation in a reversible and dose-dependent manner. These results support the notion that hypoxia, by activating HIF, plays a crucial role in preserving stem cells in an undifferentiated state in the “hypoxic niches” present in the tissue in which they reside before migrating in more oxygenated areas to heal a damaged tissue.

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Hu, Cheng-Jun, Li-Yi Wang, Lewis A. Chodosh, Brian Keith et M. Celeste Simon. « Differential Roles of Hypoxia-Inducible Factor 1α (HIF-1α) and HIF-2α in Hypoxic Gene Regulation ». Molecular and Cellular Biology 23, n^o 24 (15 décembre 2003) : 9361–74. http://dx.doi.org/10.1128/mcb.23.24.9361-9374.2003.

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ABSTRACT Transcriptional responses to hypoxia are primarily mediated by hypoxia-inducible factor (HIF), a heterodimer of HIF-α and the aryl hydrocarbon receptor nuclear translocator subunits. The HIF-1α and HIF-2α subunits are structurally similar in their DNA binding and dimerization domains but differ in their transactivation domains, implying they may have unique target genes. Previous studies using Hif-1α−/− embryonic stem and mouse embryonic fibroblast cells show that loss of HIF-1α eliminates all oxygen-regulated transcriptional responses analyzed, suggesting that HIF-2α is dispensable for hypoxic gene regulation. In contrast, HIF-2α has been shown to regulate some hypoxia-inducible genes in transient transfection assays and during embryonic development in the lung and other tissues. To address this discrepancy, and to identify specific HIF-2α target genes, we used DNA microarray analysis to evaluate hypoxic gene induction in cells expressing HIF-2α but not HIF-1α. In addition, we engineered HEK293 cells to express stabilized forms of HIF-1α or HIF-2α via a tetracycline-regulated promoter. In this first comparative study of HIF-1α and HIF-2α target genes, we demonstrate that HIF-2α does regulate a variety of broadly expressed hypoxia-inducible genes, suggesting that its function is not restricted, as initially thought, to endothelial cell-specific gene expression. Importantly, HIF-1α (and not HIF-2α) stimulates glycolytic gene expression in both types of cells, clearly showing for the first time that HIF-1α and HIF-2α have unique targets.

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Zhang, Lei, Hai-Yan Wang, Mu-Qiong Li, Xi-Xi Wang, Li Fan et Yu-Sheng Wang. « A Trojan horse biomimetic delivery system using mesenchymal stem cells for HIF-1α siRNA-loaded nanoparticles on retinal pigment epithelial cells under hypoxia environment ». International Journal of Ophthalmology 15, n^o 11 (18 novembre 2022) : 1743–51. http://dx.doi.org/10.18240/ijo.2022.11.03.

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AIM: To demonstrate the feasibility of mesenchymal stem cell (MSC)-mediated nano drug delivery, which was characterized by the “Trojan horse”-like transport of hypoxia-inducible factor-1α small interfering RNA (HIF-1α siRNA) between MSCs and retinal pigment epithelial cells (RPE) under hypoxia environment. METHODS: Plasmid and lentivirus targeting the human HIF-1α gene were designed and constructed. HIF-1α siRNA was encapsulated into poly(lactic-co-glycolic acid) nanoparticles (PLGA-NPs) through the water-in-oil-in-water (w/o/w) multiple emulsion technique. The effect of PLGA-NPs uptake on the expression of HIF-1α mRNA was tested in RPE cells by real-time quantitative polymerase chain reaction (qPCR) and additional transfected conditions were used as control, including lentivirus group, nude plasmid group and blank PLGA group. MSCs were transfected with the NPs and the transfection efficacy was evaluated by flow cytometry. Transwell co-culture system of transfected MSCs and RPE cells was constructed under hypoxia environment. The effects of MSC-loaded HIF-1α siRNA PLGA-NPs on proliferation, apoptosis, and migration of RPE cells were then evaluated. The effect of transfected MSCs on HIF-1α expression of RPE cells was analyzed by using qPCR at the time points 24h, 3d, and 7d. RESULTS: The average diameter of PLGA-NPs loaded with HIF siRNA was 314.1 nm and the zeta potential was -0.36 mV. The transfection efficiency of PLGA-NPs was 67.3%±5.2% into MSCs by using flow cytometry. Compared with the lentivirus group, the PLGA-NPs loaded with HIF-1α siRNA can effectively reduce the expression of HIF-1α mRNA up to 7d in RPE (0.63±0.05 at 7d, P<0.001). In the Transwell co-culture system of transfected MSCs and RPE, the abilities of proliferation (2.34±0.17, 2.40±0.28, 2.47±0.24 at 48h, F=0.23, P=0.80), apoptosis (14.83%±2.43%, 12.94%±2.19%, 12.39%±3.21%; F=0.70, P=0.53) and migration (124.5±7.78, 119.5±5.32, 130±9.89, F=1.33, P=0.33) of the RPE cells had no differences between MSC-loaded HIF-1α siRNA PLGA-NPs and other groups. The inhibition of PLGA on the HIF-1α mRNA expression in RPE cells could continue until the 7th day, the level of HIF-1α mRNA was lower than that of other groups (F=171.98, P<0.001). CONCLUSION: The delivery of PLGA-NPs loaded with HIF-1α siRNA carried by MSCs is found to be beneficial temporally for HIF-1α mRNA inhibition in RPE cells under hypoxia environment. The MSC-based bio-mimetic delivery of HIF-1α siRNA nanoparticles is a potential method for therapy against choroidal neovascularization.

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Suda, Toshio. « Metabolic Regulation of Hematopoietic Stem Cells During Stress ». Blood 120, n^o 21 (16 novembre 2012) : SCI—42—SCI—42. http://dx.doi.org/10.1182/blood.v120.21.sci-42.sci-42.

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Abstract Abstract SCI-42 Tissue homeostasis over the life of an organism relies on both self-renewal and multipotent differentiation of stem cells. Hematopoietic stem cells (HSCs) are sustained in a specific microenvironment known as the stem cell niche. Adult HSCs are kept quiescent during the cell cycle in the endosteal niche of the bone marrow. Normal HSCs maintain intracellular hypoxia, stabilize the hypoxia-inducible factor-1a (HIF-1a) protein, and generate ATP by anaerobic metabolism. In HIF-1a deficiency, HSCs became metabolically aerobic, lost cell cycle quiescence, and finally became exhausted. An increased dose of HIF-1a protein in VHL-mutated HSCs and their progenitors induced cell cycle quiescence and accumulation of HSCs in the bone marrow (BM), which were not transplantable. This metabolic balance promotes HSC maintenance by limiting the production of reactive oxygen species (ROS), but leaves HSCs susceptible to changes in redox status (1). We have performed the metabolomic analysis in HSCs. Upregulation of pyruvate dehydrogenase kinases enhanced the glycolytic pathway, cell cycle quiescence, and stem cell capacity. Thus, HSCs directly utilize the hypoxic microenvironment to maintain their slow cell cycle by HIF-1a-dependent metabolism. Downregulation of mitochondrial metabolism might be reasonable, since it reduces ROS generation. On the other hand, at the time of BM transplantation, HSCs activate oxidative phosphorylation to acquire more ATP for proliferation. Autophagy also energizes HSCs by providing amino acids during transplantation. ATG (autophagy-related) 7 is essential for transplantation and metabolic homeostasis. The relationship between mitochondrial heat shock protein, mortalin, and metabolism in HSCs will also be discussed. Disclosures: No relevant conflicts of interest to declare.

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Zhang, Huimin, Haiquan Lu, Lisha Xiang, John W. Bullen, Chuanzhao Zhang, Debangshu Samanta, Daniele M. Gilkes, Jianjun He et Gregg L. Semenza. « HIF-1 regulates CD47 expression in breast cancer cells to promote evasion of phagocytosis and maintenance of cancer stem cells ». Proceedings of the National Academy of Sciences 112, n^o 45 (28 octobre 2015) : E6215—E6223. http://dx.doi.org/10.1073/pnas.1520032112.

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Increased expression of CD47 has been reported to enable cancer cells to evade phagocytosis by macrophages and to promote the cancer stem cell phenotype, but the molecular mechanisms regulating CD47 expression have not been determined. Here we report that hypoxia-inducible factor 1 (HIF-1) directly activates transcription of the CD47 gene in hypoxic breast cancer cells. Knockdown of HIF activity or CD47 expression increased the phagocytosis of breast cancer cells by bone marrow-derived macrophages. CD47 expression was increased in mammosphere cultures, which are enriched for cancer stem cells, and CD47 deficiency led to cancer stem cell depletion. Analysis of datasets derived from thousands of patients with breast cancer revealed that CD47 expression was correlated with HIF target gene expression and with patient mortality. Thus, CD47 expression contributes to the lethal breast cancer phenotype that is mediated by HIF-1.

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Zhang, Chuanzhao, Debangshu Samanta, Haiquan Lu, John W. Bullen, Huimin Zhang, Ivan Chen, Xiaoshun He et Gregg L. Semenza. « Hypoxia induces the breast cancer stem cell phenotype by HIF-dependent and ALKBH5-mediated m6A-demethylation of NANOG mRNA ». Proceedings of the National Academy of Sciences 113, n^o 14 (21 mars 2016) : E2047—E2056. http://dx.doi.org/10.1073/pnas.1602883113.

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N6-methyladenosine (m6A) modification of mRNA plays a role in regulating embryonic stem cell pluripotency. However, the physiological signals that determine the balance between methylation and demethylation have not been described, nor have studies addressed the role of m6A in cancer stem cells. We report that exposure of breast cancer cells to hypoxia stimulated hypoxia-inducible factor (HIF)-1α- and HIF-2α–dependent expression of AlkB homolog 5 (ALKBH5), an m6A demethylase, which demethylated NANOG mRNA, which encodes a pluripotency factor, at an m6A residue in the 3′-UTR. Increased NANOG mRNA and protein expression, and the breast cancer stem cell (BCSC) phenotype, were induced by hypoxia in an HIF- and ALKBH5-dependent manner. Insertion of the NANOG 3′-UTR into a luciferase reporter gene led to regulation of luciferase activity by O2, HIFs, and ALKBH5, which was lost upon mutation of the methylated residue. ALKBH5 overexpression decreased NANOG mRNA methylation, increased NANOG levels, and increased the percentage of BCSCs, phenocopying the effect of hypoxia. Knockdown of ALKBH5 expression in MDA-MB-231 human breast cancer cells significantly reduced their capacity for tumor initiation as a result of reduced numbers of BCSCs. Thus, HIF-dependent ALKBH5 expression mediates enrichment of BCSCs in the hypoxic tumor microenvironment.

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Abaci, Hasan Erbil, Rachel Truitt, Eli Luong, German Drazer et Sharon Gerecht. « Adaptation to oxygen deprivation in cultures of human pluripotent stem cells, endothelial progenitor cells, and umbilical vein endothelial cells ». American Journal of Physiology-Cell Physiology 298, n^o 6 (juin 2010) : C1527—C1537. http://dx.doi.org/10.1152/ajpcell.00484.2009.

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Hypoxia plays an important role in vascular development through hypoxia-inducible factor-1α (HIF-1α) accumulation and downstream pathway activation. We sought to explore the in vitro response of cultures of human embryonic stem cells (hESCs), induced pluripotent stem cells (iPSCs), human endothelial progenitor cells (hEPCs), and human umbilical cord vein endothelial cells (HUVECs) to normoxic and hypoxic oxygen tensions. We first measured dissolved oxygen (DO) in the media of adherent cultures in atmospheric (21% O2), physiological (5% O2), and hypoxic oxygen conditions (1% O2). In cultures of both hEPCs and HUVECs, lower oxygen consumption was observed when cultured in 1% O2. At each oxygen tension, feeder-free cultured hESCs and iPSCs were found to consume comparable amounts of oxygen. Transport analysis revealed that the oxygen uptake rate (OUR) of hESCs and iPSCs decreased distinctly as DO availability decreased, whereas the OUR of all cell types was found to be low when cultured in 1% O2, demonstrating cell adaptation to lower oxygen tensions by limiting oxygen consumption. Next, we examined HIF-1α accumulation and the expression of target genes, including VEGF and angiopoietins ( ANGPT; angiogenic response), GLUT-1 (glucose transport), BNIP3, and BNIP3L (autophagy and apoptosis). Accumulations of HIF-1α were detected in all four cell lines cultured in 1% O2. Corresponding upregulation of VEGF, ANGPT2, and GLUT-1 was observed in response to HIF-1α accumulation, whereas upregulation of ANGPT1 was detected only in hESCs and iPSCs. Upregulation of BNIP3 and BNIP3L was detected in all cells after 24-h culture in hypoxic conditions, whereas apoptosis was not detectable using flow cytometry analysis, suggesting that BNIP3 and BNIP3L can lead to cell autophagy rather than apoptosis. These results demonstrate adaptation of all cell types to hypoxia but different cellular responses, suggesting that continuous measurements and control over oxygen environments will enable us to guide cellular responses.

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Xu, Na, Yajuan Xiao, Xuan Zhou, Lin Li, Fen Huang, Bing Xu et Liu Xiaoli. « Inhibition of Siah2 Ubiquitin Ligase By Vitamin K3 Attenuates Hypoxia and Blocks K562-R Cells Resistance ». Blood 124, n^o 21 (6 décembre 2014) : 5214. http://dx.doi.org/10.1182/blood.v124.21.5214.5214.

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Abstract Background and objective: Hypoxia has been shown to favor the self-renewal of murine and human hematopoietic stem cells. Hypoxia as a key feature of the “stem cell niches” in vivo, and studies found that hypoxia modified proliferation and differentiation of chronic myeloid leukemia (CML) stem cells.The E3 ubiquitin ligase Siah2 is an important regulator of the hypoxic response,which has been implicated in the regulation of the hypoxia response, as well as in the control of Ras, JNK/p38/NF-κB, MAPK signaling pathways. In the present study, we identified that SIAH2 induced k562 cells resistance to imatinib by hypoxia-inducible factor (HIF)-1a activated vascular epithelial growth factor (VEGF) pathway in hypoxia micro environment. In this study we show that SIAH2/Hif-1α induced K562 cell remain in G0 stage and resistance to imatinib, and we verified that vitamin K3 (SIAH2 inhibitor) reversed K562-R drug resistance in hypoxia microenvironment. Methods: We detected Siah2 expression levels in K562-wild type (K562-W) and K562-imatinib-resistance type (K562-R) cell lines by western blot analysis. Those two cell lines were further cultured for 24 h and 48 h under the condition of normal and hypoxia concentration of oxygen (1%, 5%), and treated K562-R with 0A5A15A30mM vitamin K3 for 72 hours in hypoxia concentration, explored cell cycle and apoptosis by flow cytometry (FCM) dyed by Annexin-V; analyzed the expression levels of Siah2, HIF-1α respectively by real-time PCR and western blot. Results: The protein of Siah2 and HIF-1α was significantly higher in K562-R compared with K562-w cells (P<0.01). Cell cycle analysis showed a 3% increase in K562-W G0/G1 cells in 1% O2 compared with normal O2, and 7% in K562-R. Under hypoxia condition, the cellular apoptotic ratio of K562-R was 5.46%, much less than 11.08% in K562-W cells. G0 cell proportion increased significantly with the long time Hypoxia (P<0.01); After being cultured in 1% oxygen concentration for 24 hours, we confirmed Siah2,HIF-1α were all up regulated in both cell lines, moreover, it was more obvious in K562-R cells. Siah2 protein expression increased along treated with vitamin K3 concentration (0, 5, 15, 30 mM) (P<0.05), on the contrary ,HIF-1α protein expression decreased with vitamin K3 concentration (P<0.05). the proportion of G0 cell was decreased in K562-R cells treated with Vitamin K3 (15mM)for 48h Under the condition of 1% oxygen concentration compared with control group (P=0.02). Conclusions: Hypoxia up-regulated of Siah2 and Hif-1α expression in K562-R, promoted cell apoptosis and arrested cells in G0 stage, and reduced cell sensitivity to Imatinib. Vitamin K3 could inhibit Siah2 and lowered Hif-1α in K562-R. These findings reveal an effective treatment for the identification of Siah2 inhibitors and would reverse TKI resistance for CML patients. Disclosures No relevant conflicts of interest to declare.

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Heirani-Tabasi, Asieh, Shirin Hamedakbari Toosi, Mahdi Mirahmadi et Mahmood Raeesolmohaddeseen. « Hypoxia-based Stem/Progenitor Cell Therapy : Focus on CXCR4/SDF-1 Axis ». Journal of Genes and Cells 3 (10 octobre 2017) : 64. http://dx.doi.org/10.15562/gnc.59.

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Cell therapy is becoming a promising approach to treat degenerative diseases. Homing of the transplanted cells is one of the continuous challenges being faced by the stem cell biologists. Chemokine receptors are one of the highly studied factors which are known to be crucial in controlling the cell/stem cell migration and targeted homing to the damaged tissues. The expression of chemokine receptors is dependent on a number of transcription factors and HIF-1α has been considered the crucial molecules controlling cellular migration and homing. Several studies have revealed that hypoxia conditions stabilize the HIF-1α which upregulate the CXCR4/SDF-1 expression and help in the improvement of tissue regeneration. Here, we review pivotal roles of HIF-1α /CXCR4/SDF-1 pathway in homing of progenitor/Stem cell which were affected by physical hypoxia as well as various hypoxia-mimicking agents.

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Ajdukovic, J. « HIF-1 — A BIG CHAPTER IN THE CANCER TALE ». Experimental Oncology 38, n^o 1 (22 mars 2016) : 9–12. http://dx.doi.org/10.31768/2312-8852.2016.38(1):9-12.

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Approximately 1.0–1.5% of the genome is transcriptionally regulated by hypoxia, and hypoxia-inducible factor (HIF)-1α is the transcription factor modulating many of these genes. Cancer cells are able to survive hypoxic environments and hypoxia itself can activate adaptive cellular responses that contribute to tumor progression. Many HIF-1α-mediated biological effects are beneficial for tumor progression, including metabolic shift toward glycolysis, inhibition of fatty acid β-oxidation, production of cellular reacreactive oxygen species and altering expression of tumor suppressor genes. HIF-1 promotes selective mitochondrial autophagy, resisand altering expression of tumor suppressor genes. HIF-1 promotes selective mitochondrial autophagy, resistance to T cell mediated lysis of cancer cells, induction of pluripotent cancer stem cells, epithelial-mesenchymal and epithelialmesenchymal-endothelial transitions beneficial for tumor growth and progression, loss of E-cadherin. HIF-1 also induces production of signal molecules and cytokines by carcinoma-associated fibroblasts and upregulation of certain microRNAs important for cancer progression. This minireview focuses on the HIF-1 promoting role in tumor initiation and progression and HIF-1 targeting. HIF-1 pathway downregulation seems to be promising in future cancer treatment.

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Wozny, Anne-Sophie, Arnaud Gauthier, Gersende Alphonse, Céline Malésys, Virginie Varoclier, Michael Beuve, Delphine Brichart-Vernos et al. « Involvement of HIF-1α in the Detection, Signaling, and Repair of DNA Double-Strand Breaks after Photon and Carbon-Ion Irradiation ». Cancers 13, n^o 15 (30 juillet 2021) : 3833. http://dx.doi.org/10.3390/cancers13153833.

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Hypoxia-Inducible Factor 1α (HIF-1α), which promotes cancer cell survival, is the main regulator of oxygen homeostasis. Hypoxia combined with photon and carbon ion irradiation (C-ions) stabilizes HIF-1α. Silencing HIF-1α under hypoxia leads to substantial radiosensitization of Head-and-Neck Squamous Cell Carcinoma (HNSCC) cells after both photons and C-ions. Thus, this study aimed to clarify a potential involvement of HIF-1α in the detection, signaling, and repair of DNA Double-Strand-Breaks (DSBs) in response to both irradiations, in two HNSCC cell lines and their subpopulations of Cancer-Stem Cells (CSCs). After confirming the nucleoshuttling of HIF-1α in response to both exposure under hypoxia, we showed that silencing HIF-1α in non-CSCs and CSCs decreased the initiation of the DSB detection (P-ATM), and increased the residual phosphorylated H2AX (γH2AX) foci. While HIF-1α silencing did not modulate 53BP1 expression, P-DNA-PKcs (NHEJ-c) and RAD51 (HR) signals decreased. Altogether, our experiments demonstrate the involvement of HIF-1α in the detection and signaling of DSBs, but also in the main repair pathways (NHEJ-c and HR), without favoring one of them. Combining HIF-1α silencing with both types of radiation could therefore present a potential therapeutic benefit of targeting CSCs mostly present in tumor hypoxic niches.

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Zhuo, Yi, Lei Wang, Lite Ge, Xuan Li, Da Duan, Xiaohua Teng, Miao Jiang et al. « Hypoxic Culture Promotes Dopaminergic-Neuronal Differentiation of Nasal Olfactory Mucosa Mesenchymal Stem Cells via Upregulation of Hypoxia-Inducible Factor-1α ». Cell Transplantation 26, n^o 8 (août 2017) : 1452–61. http://dx.doi.org/10.1177/0963689717720291.

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Olfactory mucosa mesenchymal stem cells (OM-MSCs) display significant clonogenic activity and may be easily propagated for Parkinson’s disease therapies. Methods of inducing OM-MSCs to differentiate into dopaminergic (DAergic) neurons using olfactory ensheathing cells (OECs) are thus an attractive topic of research. We designed a hypoxic induction protocol to generate DAergic neurons from OM-MSCs using a physiological oxygen (O2) level of 3% and OEC-conditioned medium (OCM; HI group). The normal induction (NI) group was cultured in O2 at ambient air level (21%). The role of hypoxia-inducible factor-1α (HIF-1α) in the differentiation of OM-MSCs under hypoxia was investigated by treating cells with an HIF-1α inhibitor before induction (HIR group). The proportions of β-tubulin- and tyrosine hydroxylase (TH)-positive cells were significantly increased in the HI group compared with the NI and HIR groups, as shown by immunocytochemistry and Western blotting. Furthermore, the level of dopamine was significantly increased in the HI group. A slow outward potassium current was recorded in differentiated cells after 21 d of induction using whole-cell voltage-clamp tests. A hypoxic environment thus promotes OM-MSCs to differentiate into DAergic neurons by increasing the expression of HIF-1α and by activating downstream target gene TH. This study indicated that OCM under hypoxic conditions could significantly upregulate key transcriptional factors involved in the development of DAergic neurons from OM-MSCs, mediated by HIF-1α. Hypoxia promotes DAergic neuronal differentiation of OM-MSCs, and HIF-1α may play an important role in hypoxia-inducible pathways during DAergic lineage specification and differentiation in vitro.

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Cui, Chun-Ping, Carmen Chak-Lui Wong, Alan Ka-Lun Kai, Daniel Wai-Hung Ho, Eunice Yuen-Ting Lau, Yu-Man Tsui, Lo-Kong Chan et al. « SENP1 promotes hypoxia-induced cancer stemness by HIF-1α deSUMOylation and SENP1/HIF-1α positive feedback loop ». Gut 66, n^o 12 (3 mars 2017) : 2149–59. http://dx.doi.org/10.1136/gutjnl-2016-313264.

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ObjectiveWe investigated the effect and mechanism of hypoxic microenvironment and hypoxia-inducible factors (HIFs) on hepatocellular carcinoma (HCC) cancer stemness.DesignHCC cancer stemness was analysed by self-renewal ability, chemoresistance, expression of stemness-related genes and cancer stem cell (CSC) marker-positive cell population. Specific small ubiquitin-like modifier (SUMO) proteases 1 (SENP1) mRNA level was examined with quantitative PCR in human paired HCCs. Immunoprecipitation was used to examine the binding of proteins and chromatin immunoprecipitation assay to detect the binding of HIFs with hypoxia response element sequence. In vivo characterisation was performed in immunocompromised mice and stem cell frequency was analysed.ResultsWe showed that hypoxia enhanced the stemness of HCC cells and hepatocarcinogenesis through enhancing HIF-1α deSUMOylation by SENP1 and increasing stabilisation and transcriptional activity of HIF-1α. Furthermore, we demonstrated that SENP1 is a direct target of HIF-1/2α and a previously unrecognised positive feedback loop exists between SENP1 and HIF-1α.ConclusionsTaken together, our findings suggest the significance of this positive feedback loop between HIF-1α and SENP1 in contributing to the increased cancer stemness in HCC and hepatocarcinogenesis under hypoxia. Drugs that specifically target SENP1 may offer a potential novel therapeutic approach for HCC.

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Cowden Dahl, Karen D., Sarah E. Robertson, Valerie M. Weaver et M. Celeste Simon. « Hypoxia-inducible Factor Regulates αvβ3 Integrin Cell Surface Expression ». Molecular Biology of the Cell 16, n^o 4 (avril 2005) : 1901–12. http://dx.doi.org/10.1091/mbc.e04-12-1082.

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Hypoxia-inducible factor (HIF)-deficient placentas exhibit a number of defects, including changes in cell fate adoption, lack of fetal angiogenesis, hypocellularity, and poor invasion into maternal tissue. HIF is a heterodimeric transcription factor consisting of α and β aryl hydrocarbon receptor nuclear translocator or ARNT) subunits. We used undifferentiated trophoblast stem (TS) cells to characterize HIF-dependent adhesion, migration, and invasion. Arnt-/- and Hifα-/- TS cells exhibit reduced adhesion and migration toward vitronectin compared with wild-type cells. Furthermore, this defect is associated with decreased cell surface expression of integrin αvβ3 and significantly decreased expression of this integrin in focal adhesions. Because of the importance of adhesion and migration in tumor progression (in addition to placental development), we examined the affect of culturing B16F0 melanoma cells in 1.5% oxygen (O2). Culturing B16F0 melanoma cells at 1.5% O2 resulted in increased αvβ3 integrin surface expression and increased adhesion to and migration toward vitronectin. Together, these data suggest that HIF and O2 tension influence placental invasion and tumor migration by increasing cell surface expression of αvβ3 integrin.

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Chilov, D., G. Camenisch, I. Kvietikova, U. Ziegler, M. Gassmann et R. H. Wenger. « Induction and nuclear translocation of hypoxia-inducible factor-1 (HIF-1) : heterodimerization with ARNT is not necessary for nuclear accumulation of HIF-1alpha ». Journal of Cell Science 112, n^o 8 (15 avril 1999) : 1203–12. http://dx.doi.org/10.1242/jcs.112.8.1203.

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Hypoxia-inducible factor-1 (HIF-1) is a master regulator of mammalian oxygen homeostasis. HIF-1 consists of two subunits, HIF-1alpha and the aryl hydrocarbon receptor nuclear translocator (ARNT). Whereas hypoxia prevents proteasomal degradation of HIF-1alpha, ARNT expression is thought to be oxygen-independent. We and others previously showed that ARNT is indispensable for HIF-1 DNA-binding and transactivation function. Here, we have used ARNT-mutant mouse hepatoma and embryonic stem cells to examine the requirement of ARNT for accumulation and nuclear translocation of HIF-1alpha in hypoxia. As shown by immunofluorescence, HIF-1alpha accumulation in the nucleus of hypoxic cells was independent of the presence of ARNT, suggesting that nuclear translocation is intrinsic to HIF-1alpha. Co-immunoprecipitation of HIF-1alpha together with ARNT could be performed in nuclear extracts but not in cytosolic fractions, implying that formation of the HIF-1 complex occurs in the nucleus. A proteasome inhibitor and a thiol-reducing agent could mimic hypoxia by inducing HIF-1alpha in the nucleus, indicating that escape from proteolytic degradation is sufficient for accumulation and nuclear translocation of HIF-1alpha. During biochemical separation, both HIF-1alpha and ARNT tend to leak from the nuclei in the absence of either subunit, suggesting that heterodimerization is required for stable association within the nuclear compartment. Nuclear stabilization of the heterodimer might also explain the hypoxically increased total cellular ARNT levels observed in some of the cell lines examined.

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Roitbak, Tamara, Lu Li et Lee Anna Cunningham. « Neural Stem/Progenitor Cells Promote Endothelial Cell Morphogenesis and Protect Endothelial Cells against Ischemia via HIF-1α-Regulated VEGF Signaling ». Journal of Cerebral Blood Flow & ; Metabolism 28, n^o 9 (14 mai 2008) : 1530–42. http://dx.doi.org/10.1038/jcbfm.2008.38.

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Vascular cells provide a neural stem/progenitor cell (NSPC) niche that regulates expansion and differentiation of NSPCs within the germinal zones of the embryonic and adult brain under both physiologic and pathologic conditions. Here, we examined the NSPC—endothelial cell (NSPC/EC) interaction under conditions of ischemia, both in vitro and after intracerebral transplantation. In culture, embryonic mouse NSPCs supported capillary morphogenesis and protected ECs from cell death induced by serum starvation or by transient oxygen and glucose deprivation (OGD). Neural stem/progenitor cells constitutively expressed hypoxia-inducible factor 1α (HIF-1α) transcription factor and vascular endothelial growth factor (VEGF), both of which were increased approximately twofold after the exposure of NSPCs to OGD. The protective effects of NSPCs on ECs under conditions of serum starvation and hypoxia were blocked by pharmacological inhibitors of VEGF signaling, SU1498 and Flt-1-Fc. After intracerebral transplantation, NSPCs continued to express HIF-1α and VEGF, and promoted microvascular density after focal ischemia. These studies support a role for NSPCs in stabilization of vasculature during ischemia, mediated via HIF-1α-VEGF signaling pathways, and suggest therapeutic application of NSPCs to promote revascularization and repair after brain injury.

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Junsheng, Mu, Tian Kun, Zhou Fan et Bo Ping. « Myocardial Patch Formation by Three-Dimensional Culture of Bone Marrow Mesenchymal Stem Cells with 3-Hydroxybutyrate-Co-4-Hydroxybutyrate Under Hypoxia ». Journal of Biomaterials and Tissue Engineering 10, n^o 7 (1 juillet 2020) : 922–29. http://dx.doi.org/10.1166/jbt.2020.2353.

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Herein we researched the effects of a hypoxic microenvironment on bone marrow mesenchymal stem cells (BM-MSCs) on poly 3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB-co-4HB)] and present a theoretical basis for development of cell transplantation. Mouse bone marrow mesenchymal stem cells were isolated by whole bone marrow culture and surface antigens were analyzed by flow cytometry of passage 5 cells. P(3HB-co-4HB) and bone marrow mesenchymal stem cells were prepared as stem cell patches randomly divided into normoxia (control, 20% oxygen) and hypoxia (3% oxygen) groups. After 24 h, the patch was used for experiments. Cell proliferation was determined by CCK-8 assays. Adhesion, survival, and growth of cells on patches were observed by scanning electron microscopy. Expression of hypoxia-inducible factor-1α (HIF-1α) was tested by real-time quantitative PCR and western blotting. At 2 weeks after addition of cardiomyocyte differentiation inducer 5-azacytidine, cardiac troponin T (cTnT) expression was detected by immunofluorescence. After 24 h, the proliferation of the hypoxic group was considerably greater compared with the normoxic group (n = 12,P < 0 05). SEM demonstrated that the number of viable cells in the hypoxic group was higher than that in the normoxic group. Adhesion between cells and the patch was firm and cell morphology was normal in the hypoxic group. Significant upregulation of HIF-1α mRNA was observed by real-time quantitative PCR after 12 h (P < 0 05). HIF-1αprotein expression in the hypoxia group was considerably higher than that in the normoxia group. cTnT expression in the hypoxic group was more pronounced than that in the normoxic group. Our results show that a hypoxic microenvironment promotes the adhesion, survival, proliferation, and myocardial differentiation of bone marrow mesenchymal stem cells on a P(3HB-co-4HB) patch, which may be mediated by the HIF-1α; pathway.

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Nishikawa, Masahiro, Akihiro Inoue, Yoshihiro Ohtsuka, Saya Ozaki, Shirabe Matsumoto, Satoshi Suehiro, Hajime Yano et al. « CBMS-04 SIGNIFICANT ROLE OF HYPOXIA IN THE EXPRESSION AND FUNCTION OF OSTEOPONTIN IN CD44-HIGHLY EXPRESSED GLIOMA STEM-LIKE CELLS IN TUMOR PROGRESSION OF GLIOBLASTOMA ». Neuro-Oncology Advances 1, Supplement_2 (décembre 2019) : ii5. http://dx.doi.org/10.1093/noajnl/vdz039.024.

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Abstract The poor prognosis of glioblastoma multiforme (GBM) may be due to the surviving glioma stem-like cells (GSCs) in the tumor periphery after tumor resection. We demonstrated that CD44-expressed GSCs existed much more in the tumor periphery of high invasive (HI) type GBM than low invasive (LI) type GBM. The HI type was significantly associated with worse outcome, but how GSCs with high CD44 expression relate to tumor progression remains unknown. In this study, we investigated effects of hypoxia on CD44-directed signal pathways, leading to tumor invasion and proliferation in GBM. We focused on the CD44 ligand osteopontin (OPN) because it is known hypoxia affects the interaction of CD44 and OPN which promotes stemness and proliferation of cancer stem cells. We examined mRNA expressions of hypoxia inducible factor (HIF)-1a, HIF-2a, CD44 and OPN in tumor tissues of GBM and investigated effects of hypoxia (1%O2:severe or 5%O2:moderate) on the expression of these molecules using cultured GSCs that were established from tumor tissues showing high CD44 expression in the periphery of GBMs. In addition, we analyzed the effects of OPN on invasive, migratory and proliferative activities of GSCs under the hypoxic conditions. OPN was much higher expressed in the tumor periphery of LI type GBM than HI type GBM. Severe hypoxia significantly increased the expressions of HIF-1a and CD44 but did not OPN. On the other hands, moderate hypoxia promoted the expressions of HIF-2a and OPN. Knockdown of HIF-2a significantly inhibited OPN expression. In addition, the more OPN was expressed in the cultured GSCs under moderate hypoxia, the more the GSCs proliferated and decreased their invasive and migratory activities. In conclusion, GSCs existing in the tumor periphery of GBM can migrate or proliferate by changing CD44-directed signal pathways. Moderate hypoxia promoted HIF-2a/OPN/CD44 pathway, resulting in phenotypic transition to high proliferative tumors.

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Wei, Lingling, Lijie Zhang, Longyan Yang, Xin Wang, Chunhua Zhao et Dong Zhao. « Protective Effect of Mesenchymal Stem Cells on Isolated Islets Survival and Against Hypoxia Associated With the HIF-1α/PFKFB3 Pathway ». Cell Transplantation 31 (janvier 2022) : 096368972110731. http://dx.doi.org/10.1177/09636897211073127.

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Islets have a high demand for oxygen and most of them will die of hypoxia injury before and after transplantation. Hypoxic damage is one of the key factors associated with islet graft dysfunction. Mesenchymal stem cells (MSCs) have multiple functions and can enhance the therapeutic effect of islet transplantation. In this study, islets were cultured together with or without MSCs derived from umbilical cord (hUC-MSCs) under normal and hypoxic conditions. The effect of hUC-MSCs on the survival and function of isolated islets was detected by immunofluorescence and ELISA. Hypoxia-inducible factor 1 alpha (HIF-1α) and PFKFB3 mRNA and protein expression in different conditions were tested by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blot. The islets co-cultured with hUC-MSCs have improved viability and function compared with islets cultured alone. The mRNA transcription of HIF-1α in the co-cultured group increased. The protein expression of PFKFB3 increased with the increase of HIF-1α. This study found that hUC-MSCs could protect islets from dysfunction caused by hypoxia, and HIF-1α/PFKFB3 played an important role in hypoxic resistance, suggesting a potential strategy to improve the outcome of islet transplantation.

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Chaparro, Alejandra, Mauricio Lozano, Dominique Gaedechens, Carolina López, Daniela Albers, Marcela Hernández, Andrés Pascual, José Nart et Carlos E. Irarrazabal. « Exploring the Expression of Pro-Inflammatory and Hypoxia-Related MicroRNA-20a, MicroRNA-30e, and MicroRNA-93 in Periodontitis and Gingival Mesenchymal Stem Cells under Hypoxia ». International Journal of Molecular Sciences 23, n^o 18 (7 septembre 2022) : 10310. http://dx.doi.org/10.3390/ijms231810310.

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Hypoxia associated with inflammation are common hallmarks observed in several diseases, and it plays a major role in the expression of non-coding RNAs, including microRNAs (miRNAs). In addition, the miRNA target genes for hypoxia-inducible factor-1α (HIF-1α) and nuclear factor of activated T cells-5 (NFAT5) modulate the adaptation to hypoxia. The objective of the present study was to explore hypoxia-related miRNA target genes for HIF-1α and NFAT5, as well as miRNA-20a, miRNA-30e, and miRNA-93 expression in periodontitis versus healthy gingival tissues and gingival mesenchymal stem cells (GMSCs) cultured under hypoxic conditions. Thus, a case-control study was conducted, including healthy and periodontitis subjects. Clinical data and gingival tissue biopsies were collected to analyze the expression of miRNA-20a, miRNA-30e, miRNA-93, HIF-1α, and NFAT5 by qRT-PCR. Subsequently, GMSCs were isolated and cultured under hypoxic conditions (1% O2) to explore the expression of the HIF-1α, NFAT5, and miRNAs. The results showed a significant upregulation of miRNA-20a (p = 0.028), miRNA-30e (p = 0.035), and miRNA-93 (p = 0.026) in periodontitis tissues compared to healthy gingival biopsies. NFAT5 mRNA was downregulated in periodontitis tissues (p = 0.037), but HIF-1α was not affected (p = 0.60). Interestingly, hypoxic GMSCs upregulated the expression of miRNA-20a and HIF-1α, but they downregulated miRNA-93e. In addition, NFAT5 mRNA expression was not affected in hypoxic GMSCs. In conclusion, in periodontitis patients, the expression of miRNA-20a, miRNA-30e, and miRNA-93 increased, but a decreased expression of NFAT5 mRNA was detected. In addition, GMSCs under hypoxic conditions upregulate the HIF-1α and increase miRNA-20a (p = 0.049) expression. This study explores the role of inflammatory and hypoxia-related miRNAs and their target genes in periodontitis and GMSCs. It is crucial to determine the potential therapeutic target of these miRNAs and hypoxia during the periodontal immune–inflammatory response, which should be analyzed in greater depth in future studies.

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Cheloni, Giulia, Michele Tanturli, Ignazia Tusa, Ngoc Ho DeSouza, Yi Shan, Antonella Gozzini, Fréderic Mazurier, Elisabetta Rovida, Shaoguang Li et Persio Dello Sbarba. « Targeting chronic myeloid leukemia stem cells with the hypoxia-inducible factor inhibitor acriflavine ». Blood 130, n^o 5 (3 août 2017) : 655–65. http://dx.doi.org/10.1182/blood-2016-10-745588.

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Key Points The HIF inhibitor ACF suppresses TKI-insensitive CML stem cells. The FDA-approved drug ACF may represent a novel treatment to prevent CML relapse and, in combination with TKIs, improve remission.

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Teti, Gabriella, Stefano Focaroli, Viviana Salvatore, Eleonora Mazzotti, Laura Ingra’, Antonio Mazzotti et Mirella Falconi. « The Hypoxia-Mimetic Agent Cobalt Chloride Differently Affects Human Mesenchymal Stem Cells in Their Chondrogenic Potential ». Stem Cells International 2018 (2018) : 1–9. http://dx.doi.org/10.1155/2018/3237253.

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Adult stem cells are a promising cell source for cartilage regeneration. They resided in a special microenvironment known as the stem-cell niche, characterized by the presence of low oxygen concentration. Cobalt chloride (CoCl2) imitates hypoxia in vitro by stabilizing hypoxia-inducible factor-alpha (HIF-1α), which is the master regulator in the cellular adaptive response to hypoxia. In this study, the influence of CoCl2 on the chondrogenic potential of human MSCs, isolated from dental pulp, umbilical cord, and adipose tissue, was investigated. Cells were treated with concentrations of CoCl2 ranging from 50 to 400 μM. Cell viability, HIF-1α protein synthesis, and the expression of the chondrogenic markers were analyzed. The results showed that the CoCl2 supplementation had no effect on cell viability, while the upregulation of chondrogenic markers such as SOX9, COL2A1, VCAN, and ACAN was dependent on the cellular source. This study shows that hypoxia, induced by CoCl2 treatment, can differently influence the behavior of MSCs, isolated from different sources, in their chondrogenic potential. These findings should be taken into consideration in the treatment of cartilage repair and regeneration based on stem cell therapies.

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Xu, Na, Xiaozhen Xiao, Yajuan Xiao, Xuan Zhou, Guanlun Gao, Fen Huang, Dan Xu, Hongsheng Zhou, Bing Xu et Liu Xiaoli. « The E3 Ubiquitin Ligases Siah2 Contributes To Imatinib Resistance In Chronic Myeloid Leukemia In Hypoxia Condition ». Blood 122, n^o 21 (15 novembre 2013) : 2530. http://dx.doi.org/10.1182/blood.v122.21.2530.2530.

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Abstract Background and Objective Severe hypoxia has been shown to favor the self-renewal of human hematopoietic stem cells. Recent studies demonstrate that hypoxia via hypoxia-inducible factor (Hif-1a) can modify the proliferation and differentiation of CML stem cells. The ubiquitin E3 ligase SIAH2 is an important regulator of the hypoxic response as it leads to the ubiquitin/proteasomal degradation of prolyl hydroxylases such as PHD3, which in turn increases the stability of Hif-1a. The Hif-1a has been linked to chemosensitivity while the underlying molecular mechanism remains elusive. Therefore, we comprehensively analysed SIAH2 and Hif-1a role in determining chemosensitivity via signal molecule vascular epithelial growth factor (VEGF) pathway. Methods We tested the level of Siah2, Hif-1a and VEGF in Imatinb-sensitive CML Patients (n=15) and insensitive CML patients(n=10) by real-time reverse transcription PCR and western blot analysis. K562-wild type (K562-W) and K562-imatinib-resistance type (K562-R) cell were cultured for 24h and 48h under the condition of normal and hypoxia concentration of oxygen (1%). Knockdown of SAIH2 by RNA interference ,Cell viability and IC50 under 1% concentration oxygen were tested by cck-8;detected cell cycle and apoptosis by flow cytometry (FCM) ; analyzed the expression levels of Siah2, Hif-1a and VEGF respectively by real-time PCR and western blot. Results The level of mRNA and protein of SIAH2 ,Hif-1a and VEGF were significantly higher in IM- resistant CML patients compared to IM sensitive CML patients, respectively (P<0.05). The similar results were observed in K562-R and K562-W cells(P<0.01). Under 21%,1% oxygen concentration cultured for 24h ,the IC50 of K562-W and K562-R cells was no significant difference (P<0.05),but there was significant difference after cultured for 48h Cell cycle analysis showed that more G0/G1 cells in K562-R than K562-W after cultured for 48h under hypoxia condition(P<0.05). After being cultured in 1% oxygen concentration for 48 hours, we confirmed SIAH2, Hif-1a and VEGF were up-regulated in both cell lines, moreover, it was more obvious in K562-R cells. In SIAH2-sh K562-R cells, the apoptosis was higher than K562-R cells obviously under 1% oxygen concentration for 48 hours(P<0.05);the level of Hif-1a Hardly monitored, and the level of VEGF was also lower. Conclusions There were higher level of SIAH2, Hif-1a and VEGF in IM-resistant CML patients. Under hypoxia condition, K562 cells were likely to improve their resistance to Imatinib .After we Knockdown SAIH2, K562-R Cell apoptosis rate increased significantly, along with low level Hif-1a and VEGF. It indicated that in hypoxia micro-environment, Siah-2 might be one of the critical molecules that induce Imatinib-resistance in CML in the way of maintaining leukemic cell survival and stimulating them into quiescence phase. Disclosures: No relevant conflicts of interest to declare.

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Martin, Anthony R., Cyril Ronco, Luc Demange et Rachid Benhida. « Hypoxia inducible factor down-regulation, cancer and cancer stem cells (CSCs) : ongoing success stories ». MedChemComm 8, n^o 1 (2017) : 21–52. http://dx.doi.org/10.1039/c6md00432f.

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In cancers, hypoxia inducible factor 1 (HIF-1) is an over-expressed transcription factor, which regulates a large set of genes involved in tumour vascularization, metastases, and cancer stem cells (CSCs) formation and self-renewal.

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Niechi, Ignacio, Atenea Uribe-Ojeda, José Ignacio Erices, Ángelo Torres, Daniel Uribe, José Dellis Rocha, Pamela Silva, Hans G. Richter, Rody San Martín et Claudia Quezada. « Adenosine Depletion as A New Strategy to Decrease Glioblastoma Stem-Like Cells Aggressiveness ». Cells 8, n^o 11 (30 octobre 2019) : 1353. http://dx.doi.org/10.3390/cells8111353.

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Glioblastoma is the brain tumor with the worst prognosis. This is mainly due to a cell subpopulation with an extremely aggressive potential, called glioblastoma stem-like cells (GSCs). These cells produce high levels of extracellular adenosine, which are increased even more under hypoxic conditions. Under hypoxia, adenosine signaling is related to HIF-2α expression, enhancing cell aggressiveness. Adenosine can be degraded using recombinant adenosine deaminase (ADA) to revert its pathological effects. The aim of this study was to degrade adenosine using ADA in order to decrease malignancy of GSCs. Adenosine depletion was performed using recombinant ADA. Migration and invasion were measured by transwell and matrigel-coated transwell assay, respectively. HIF-2α-dependent cell migration/invasion decreased in GSCs treated with ADA under hypoxia. MRPs-mediated chemoresistance and colony formation decreased in treatment with ADA. In conclusion, adenosine depletion using adenosine deaminase decreases GSCs aggressiveness.

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Chakraborty, Damayanti, Wei Cui, Gracy X. Rosario, Regan L. Scott, Pramod Dhakal, Stephen J. Renaud, Makoto Tachibana et al. « HIF-KDM3A-MMP12 regulatory circuit ensures trophoblast plasticity and placental adaptations to hypoxia ». Proceedings of the National Academy of Sciences 113, n^o 46 (2 novembre 2016) : E7212—E7221. http://dx.doi.org/10.1073/pnas.1612626113.

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The hemochorial placenta develops from the coordinated multilineage differentiation of trophoblast stem (TS) cells. An invasive trophoblast cell lineage remodels uterine spiral arteries, facilitating nutrient flow, failure of which is associated with pathological conditions such as preeclampsia, intrauterine growth restriction, and preterm birth. Hypoxia plays an instructive role in influencing trophoblast cell differentiation and regulating placental organization. Key downstream hypoxia-activated events were delineated using rat TS cells and tested in vivo, using trophoblast-specific lentiviral gene delivery and genome editing. DNA microarray analyses performed on rat TS cells exposed to ambient or low oxygen and pregnant rats exposed to ambient or hypoxic conditions showed up-regulation of genes characteristic of an invasive/vascular remodeling/inflammatory phenotype. Among the shared up-regulated genes was matrix metallopeptidase 12 (MMP12). To explore the functional importance of MMP12 in trophoblast cell-directed spiral artery remodeling, we generated an Mmp12 mutant rat model using transcription activator-like nucleases-mediated genome editing. Homozygous mutant placentation sites showed decreased hypoxia-dependent endovascular trophoblast invasion and impaired trophoblast-directed spiral artery remodeling. A link was established between hypoxia/HIF and MMP12; however, evidence did not support Mmp12 as a direct target of HIF action. Lysine demethylase 3A (KDM3A) was identified as mediator of hypoxia/HIF regulation of Mmp12. Knockdown of KDM3A in rat TS cells inhibited the expression of a subset of the hypoxia–hypoxia inducible factor (HIF)-dependent transcripts, including Mmp12, altered H3K9 methylation status, and decreased hypoxia-induced trophoblast cell invasion in vitro and in vivo. The hypoxia-HIF-KDM3A-MMP12 regulatory circuit is conserved and facilitates placental adaptations to environmental challenges.

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Xu, Wei, Ruijun Xu, Zhikun Li, Yi Wang et Ruixi Hu. « Hypoxia changes chemotaxis behaviour of mesenchymal stem cells via HIF-1α signalling ». Journal of Cellular and Molecular Medicine 23, n^o 3 (9 janvier 2019) : 1899–907. http://dx.doi.org/10.1111/jcmm.14091.

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Kozal, Karolina, et Anna Krześlak. « The Role of Hypoxia-Inducible Factor Isoforms in Breast Cancer and Perspectives on Their Inhibition in Therapy ». Cancers 14, n^o 18 (17 septembre 2022) : 4518. http://dx.doi.org/10.3390/cancers14184518.

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Hypoxia is a common feature associated with many types of cancer. The activity of the hypoxia-inducible factors (HIFs), the critical element of response and adaptation to hypoxia, enhances cancer hallmarks such as suppression of the immune response, altered metabolism, angiogenesis, invasion, metastasis, and more. The HIF-1α and HIF-2α isoforms show similar regulation characteristics, although they are active in different types of hypoxia and can show different or even opposite effects. Breast cancers present several unique ways of non-canonical hypoxia-inducible factors activity induction, not limited to the hypoxia itself. This review summarizes different effects of HIFs activation in breast cancer, where areas such as metabolism, evasion of the immune response, cell survival and death, angiogenesis, invasion, metastasis, cancer stem cells, and hormone receptors status have been covered. The differences between HIF-1α and HIF-2α activity and their impacts are given special attention. The paper also discusses perspectives on using hypoxia-inducible factors as targets in anticancer therapy, given current knowledge acquired in molecular studies.

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Han, Myung-Kwan, Charlie Mantel, Ying Guo, Wen Tao et Hal E. Broxmeyer. « Role of SIRT1 in Proliferation and Self-Renewal of Mouse Embryonic Stem Cells. » Blood 106, n^o 11 (16 novembre 2005) : 520. http://dx.doi.org/10.1182/blood.v106.11.520.520.

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Abstract A detailed understanding of regulation of self-renewal and ex-vivo expansion of embryonic stem cells is vital to ensure their safe and efficient use for differentiation to hematopoietic cells to be used in various therapeutic methodologies. The maintenance of murine embryonic stem (mES) cell self-renewal is regulated by leukemia inhibitory factor (LIF)-dependent activation of signal transducer and activator of transcription 3 (STAT3) and LIF-independent mechanisms including Nanog, BMP2/4, and Wnt signaling. Here we describe a novel role for the NAD-dependent protein deacetylase, SIRT1, in regulation of mES cell proliferation and self-renewal. SIRT1 mRNA expression in mES cells was induced by LIF through hypoxia-independent activation of hypoxia inducing factor-1α (HIF-1α. We cloned the 2 kb 5′-flanking region of the mouse SIRT1 gene and fused it to the luciferase gene. Overexpression of HIF-1α markedly enhanced SIRT1 promoter activity and a dominant-negative isoform, HIF-1α completely suppressed it. We demonstrated that two putative HIF-1α response element in the SIRT1 gene 5′-flanking region (-216 to -146) is essential for this SIRT1 induction. The two promoter regions, containing HIF-1-binding sequences, were regulated directly by HIF-1 α. These results suggest that HIF-1 enhances transactivation of the SIRT1 gene in mES cells that maintain their undifferentiated state with LIF, implying that stimulation of the SIRT1 promoter by HIF-1 may be responsible for induction of the SIRT1 gene. HIF-1α activation was blocked by the reversible phosphatidylinositol 3-OH kinase (PI3K) inhibitor, LY294002, as well as a more specific inhibititory class I(A) PI3K via regulated expression of dominant negative Deltap85, indicating that PI3K signaling is important for the hypoxia-independent HIF activity. We also demonstrate that SIRT1 deacetylates p53 at Lys 379 and then exports p53 to the cytoplasm, which results in inhibition of p53 transcriptional activity on p21. Inhibition of SIRT1 expression by siRNA translocated p53 to the nucleus and recovered p53 transactivational activity, suggesting that the deacetylated form of p53 at Lys 379 cannot access the p21 promoter and activate p21 transcription. To our knowledge, this is the first description of an influence of SIRT1 on p53 nuclear translocation via its deacetylation activity on p53. Surprisingly, we also found that N-terminal deleted p73 (DeltaNp73), a p53 family member, binds to p53 binding sites on the nanog promoter in normal mES cells, while p53 binds to p53 binding sites on the nanog promoter only in SIRT1-deficient mES cells. We then cloned the 2 kb 5′-flanking region of the mouse nanog gene and fused it to the luciferase gene. Overexpression of DeltaNp73 enhanced nanog promoter activity, but additional overexpression of p53 with DeltaNp73 abolished DeltaNp73-induced enhancement of nanog promoter activity. These data suggest that SIRT1 may regulate binding of two transcription factors, p53 and DeltaNp73, to the p53 binding site of the nanog promoter and turn on/off the nanog gene, which may eventually determine ES cell fate to self-renewal or differentiation. Upon long term inhibition of SIRT1 by SIRT1 siRNA retroviral infection, we observed a reduction in cell proliferation rate, whereas long term overexpression of SIRT by retroviral vector containing SIRT1 gene enhanced cell proliferation. Our results suggest SIRT1 controls self-renewal and proliferation of mES cells by regulation of p53 localization through deacetylation of p53.

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Yu, Qin, Jie Lin, Lizhen Liu, Peipei Li, XiaoBo Xuan, Yan Wang, YanPing Duan et Hui Dong. « Research of HIF-1 Mediated SDF-1/CXCR4 Axis on the Directional Migration and Neural Differentiation of Mesenchymal Stem Cells ». Blood 116, n^o 21 (19 novembre 2010) : 4699. http://dx.doi.org/10.1182/blood.v116.21.4699.4699.

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Abstract Abstract 4699 Introduction: Mesenchymal stem cells (MSCs) are under study as therapeutic delivery agents that assist in the repair of damaged tissues. At present, the mechanisms of targeted therapy of MSCs are known to relate with the hypoxia-inducible factor-1 (HIF-1) and its regulated biological axis stromal cell-derived factor-1/chemokine receptor 4 (SDF-1/CXCR4). SDF-1 and CXCR4 have a wide distribution in various cells and tissues, which plays an important role in the development of immune system, circulatory system and central nervous system. We thus inferred that SDF-1/CXCR4 may participate in the differentiation as well as the migration of stem cells. Our research aims to explore the effect of HIF-1α and its mediated SDF-1/CXCR4 axis on the directional migration and neural differentiation of MSCs, which may lead to a break in the efficiency and target distribution of MSCs therapy. Method: (1) Influence of hypoxia, CXCR4 antagonist (AMD3100) and SDF-1α on the proliferation of rat Mesenchymal Stem Cells (rMSCs): rMSCs were isolated from bone marrow of rats, and expanded in vitro. The growth feature of rMSCs exposed to hypoxia (PO2=1%) or normoxia was identified by growth curve, while the effect of AMD3100 (5ug/ml) and SDF-1α (10ng/ml and 100ng/ml) on the proliferation ability of rMSCs was detected by cell counting kit-8. (2) Effect of hypoxia on the expression of HIF-1α, CXCR4 and SDF-1α: Firstly, we used RT-PCR, western blotting and flow cytometry to detect the expression of HIF-1α and CXCR4 mRNA and protein levels in rMSCs which treated with hypoxia for 0h, 6h, 12h, 24h, 48h and 72h. Secondly, HIF-1α, SDF-1α mRNA and protein level in the hippocampus of rats which suffered hypoxia- ischemia for 1d, 3d, 5d, 7d, 14d and 21d were also detected by the same assays. (3) Research of HIF-1α and SDF-1/CXCR4 axis on the migration of rMSCs: We first detected the change of CXCR4 mRNA and protein levels in rMSCs treated with AMD3100 (5ug/ml) and SDF-1α (10ng/ml) by RT-PCR, western blotting and flow cytometry, and then studied SDF-1/CXCR4 axis on the migration of rMSCs using Transwell assay. (4) Effect of HIF-1α and SDF-1/CXCR4 axis on the differentiation of rMSCs: protein level of NSE and GFAP as well as positive rate of neural-induced rMSCs which have been pretreated with AMD3100 (5ug/ml) were detected by western blotting and immunocytochemistry. Results: Persistent hypoxia promoted the proliferation of rMSCs, while AMD3100 and SDF-1α at the concentration mentioned above had no effect. Compared to normal control, the protein expression of HIF-1α in rMSCs increased in hypoxic condition while the mRNA of HIF-1α did not change. Furthermore, the mRNA and protein level of CXCR4 both increased in rMSCs exposed to hypoxia for 6h and 12h, and the results confirmed by flow cytometry. We found HIF-1α mRNA was stably expressed in hippocampus, and increased significantly in hypoxia-ischemia brain damaged (HIBD) rats in a time dependent manner, which reached the peak on 7d. As expected, SDF-1α mRNA in hippocampus of HIBD rats was higher than that of normal control group, which reached the peak on 7d (P<0.01) and stably expressed till 21d, while the protein level is mainly in concordance. Moreover, CXCR4 mRNA was extremely up-regulated in rMSCs treated with SDF-1α (10ng/ml), however, in 5 ug/ml AMD3100 treated rMSCs, which decreased markedly (P<0.01), and the results were confirmed by western blotting and flow cytometry assays (P<0.05). Transwell assay manifested that SDF-1α had obvious chemotaxis to rMSCs. Protein level and positive cell number of NSE and GFAP were extremely down-regulated in rMSCs which pretreated with 5ug/ml AMD3100. Conclusion: Increased expression of HIF-1α led to the up-regulation of SDF-1/CXCR4 axis, and rMSCs displayed chemotaxis migration ascribed to the receptor-ligand interactions of SDF-1α and CXCR4, suggesting that HIF-1 and its mediated SDF-1/CXCR4 axis are of great significant on the directional migration of rMSCs. We also showed that CXCR4 antagonisation reduced the neural differentiation capabilities of rMSCs, thus suggested that SDF-1/CXCR4 axis may deeply involve in the neural differentiation of rMSCs. Disclosures: No relevant conflicts of interest to declare.

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Qi, Yanmei, Xiaoxiang Tian, Jie Liu, Yaling Han, Alan M. Graham, M. Celeste Simon, Josef M. Penninger, Peter Carmeliet et Shaohua Li. « Bnip3 and AIF cooperate to induce apoptosis and cavitation during epithelial morphogenesis ». Journal of Cell Biology 198, n^o 1 (2 juillet 2012) : 103–14. http://dx.doi.org/10.1083/jcb.201111063.

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Apoptosis is an essential step in cavitation during embryonic epithelial morphogenesis, but its mechanisms are largely unknown. In this paper, we used embryonic stem cell–differentiated embryoid bodies (EBs) as a model and found that Bnip3 (Bcl-2/adenovirus E1B 19-kD interacting protein), a BH3-only proapoptotic protein, was highly up-regulated during cavitation in a hypoxia-dependent manner. Short hairpin RNA silencing of Bnip3 inhibited apoptosis of the core cells and delayed cavitation. We show that the Bnip3 up-regulation was mediated mainly by hypoxia-inducible factor (HIF)–2. Ablation of HIF-2α or HIF-1β, the common β subunit of HIF-1 and -2, suppressed Bnip3 up-regulation and inhibited apoptosis and cavitation. We further show that apoptosis-inducing factor (AIF) cooperated with Bnip3 to promote lumen clearance. Bnip3 silencing in AIF-null EBs nearly blocked apoptosis and cavitation. Moreover, AIF also regulated Bnip3 expression through mitochondrial production of reactive oxygen species and consequent HIF-2α stabilization. These results uncover a mechanism of cavitation through hypoxia-induced apoptosis of the core cells mediated by HIFs, Bnip3, and AIF.

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ITOH, MAI, YUKI OKUHASHI, YUSUKE TAKAHASHI, YURI SONODA, SALWA MOHAMMAD, TATSUYA SAITO, ERIKA SHIRATORI et SHUJI TOHDA. « Hypoxia Up-regulates HIF Expression While Suppressing Cell Growth and NOTCH Activity in Leukaemia Cells ». Anticancer Research 39, n^o 8 (31 juillet 2019) : 4165–70. http://dx.doi.org/10.21873/anticanres.13575.

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Forristal, Catherine E., Falak Helwani, Sally Martin, Bianca Nowlan, Ingrid G. Winkler, Andrew Zannettino et Jean-Pierre Levesque. « Hypoxia Inducible Factor (HIF)-2α Enhances Proliferation Of Malignant Hematopoietic Cells In The Hypoxic Malignant Bone Marrow ». Blood 122, n^o 21 (15 novembre 2013) : 2895. http://dx.doi.org/10.1182/blood.v122.21.2895.2895.

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Abstract Hypoxia and hypoxia-inducible factors (HIFs) are implicated in the regulation of normal and malignant hematopoiesis. HIF-1α stabilization makes leukemia stem cells and normal HSC dormant and is necessary to maintain their self-renewal potential. In sharp contrast, HIF-2α, which shares 60% homology with HIF-1a, promotes proliferation of renal clear carcinoma and embryonic stem cells by enhancing expression of oct-4, sox2 and activating c-myc. In this study, we investigated the role of hypoxia and HIF-2α in leukemia. In normal mouse and human bone marrow (BM), HIF-2α mRNA expression was observed predominantly in non-hematopoietic stromal cells, while hematopoietic cells displayed low to undetectable levels. In contrast, HIF-2α mRNA and protein were detected in the BM of moribund NOD/SCID mice engrafted with 3 different human ALL, and in cultured human ALL and AML cell lines, suggesting that HIF-2α is abnormally expressed in leukemic cells. To investigate the potential roles of HIF-2α in leukemic cells, we cloned human HIF-2α cDNA into the MXIE retroviral vector. In a 1st model the GM-CSF-dependent mouse pre-leukemic cell line FDCP1, which does not express HIF-2α, was retrovirally transduced with HIF-2α. HIF-2α provided a significant proliferative advantage to FDCP1 cells in hypoxic or normoxic cultures and reduced GM-CSF dependency. We next transplanted retrovirally transduced FDCP1 cells into non-irradiated syngeneic DBA/2 mice. All recipients of FDCP1 transduced with HIF-2α-MXIE vector succumbed to leukemia by week 28 post-transplantation. In sharp contrast, mice receiving FDCP1 transduced with empty MXIE vector, displayed a leukemia penetrance of only 15% by week 45 (Fig. 1a; p=0.0001 log rank, hazard ratio = 12.28).Fig. 1Percent survival of recipients of (a) FDCP1 cells retrovirally transduced with HIF-2α-MXIE vector or MXIE control empty vector, (b) vavBcl2 HSC transduced with HIF-2α-MXIE vector or MXIE empty vector, and (c) HL60 cells transduced with HIF-2α knocked-down or scrambled control lentiviral vectors.Fig. 1. Percent survival of recipients of (a) FDCP1 cells retrovirally transduced with HIF-2α-MXIE vector or MXIE control empty vector, (b) vavBcl2 HSC transduced with HIF-2α-MXIE vector or MXIE empty vector, and (c) HL60 cells transduced with HIF-2α knocked-down or scrambled control lentiviral vectors. In a 2nd model, HSC from vavBcl2 transgenic mice were transduced with human HIF-2α-containing or empty MXIE retroviral vectors and subsequently transplanted into lethally irradiated wild-type recipients. Transduction of vavBcl2 HSC with HIF-2α resulted in the outgrowth of HIF-2α-expressing B cells which was not observed in recipients of vavBcl2 HSC transduced with empty vector. Consequently recipients of HIF-2α transduced vavBcl2 HSC succumbed more rapidly to spontaneous lymphoma compared to controls (Fig. 1b; p=0.036 log rank, hazard ratio = 2.971, MXIE median survival = 56 weeks, HIF2α median survival = 41 weeks). Finally, HIF-2α was knocked-down in human leukemia cell lines U937 and HL60 using a shRNA lentiviral vector. HIF-2α knock-down resulted in a 2-fold decrease in proliferation in vitro. We next transplanted HL60-HIF-2a shRNA and HL60-scrambled shRNA cells into NOD/SCID/ IL2Rγ-/- (NSG) mice for each group. Notably, all recipients of HL60-HIF-2a shRNA cells succumbed to leukemia significantly later than recipients of HL60-scrambled shRNA cells (Fig. 1c; p=<0.027 Log-rank, hazard ratio = 0.1918, Scrambled median survival = 5 weeks, HIF-2α knock down median survival = 6 weeks). Together these data suggest that expression of HIF-2α in malignant hematopoietic cells provides a proliferative advantage in the hypoxic malignant BM enabling them to proliferate in the hypoxic leukemic BM while the proliferation of normal HSC, which do not express HIF-2α, is blocked by hypoxia-stabilized HIF-1α. Disclosures: No relevant conflicts of interest to declare.

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Lee, Sang Hun, Min Hee Kim et Ho Jae Han. « Arachidonic acid potentiates hypoxia-induced VEGF expression in mouse embryonic stem cells : involvement of Notch, Wnt, and HIF-1α ». American Journal of Physiology-Cell Physiology 297, n^o 1 (juillet 2009) : C207—C216. http://dx.doi.org/10.1152/ajpcell.00579.2008.

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Recent investigations suggest that hypoxia increases the release of fatty acids, which participate in the regulation of cytokine synthesis and cell growth. Therefore, in this study, we examined the effect of arachidonic acid (AA) on hypoxia-induced vascular endothelial growth factor (VEGF) expression and its related signaling pathways in mouse embryonic stem (ES) cells. Hypoxia increased the level of [3H]AA release and VEGF expression. AA treatment concurrent with hypoxia further increased the PGE2 production and VEGF expression level, which was inhibited by the suppression of cPLA2 and cyclooxygenase 2 (COX-2) pathways. Hypoxia increased the level of Notch-1 and Wnt-1/β-catenin expression, which was blocked by the inhibition of COX-2, and inhibition of Notch-1 by γ-secretase inhibitor blocked Wnt-1 activation. Moreover, the hypoxia-induced increase of hypoxia-inducible factor 1α (HIF-1α) expression induced Notch-1 activation and was regulated by Wnt-1 activation. The expression of each signaling molecule induced an increase in VEGF expression that was greater in hypoxia with AA than in hypoxia alone. The inhibition of VEGF expression using VEGF-targeted small interfering RNA decreased the hypoxia-induced increase in cell cycle regulatory protein expression, DNA synthesis, and cell number, suggesting that hypoxia-induced VEGF expression stimulates proliferation of mouse ES cells. In conclusion, AA potentiates hypoxia-induced VEGF expression in mouse ES cells through the Notch-1, Wnt-1, and HIF-1α pathways.

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Lekli, Istvan, Narasimman Gurusamy, Diptarka Ray, Arpad Tosaki et Dipak K. Das. « Redox regulation of stem cell mobilizationThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research. » Canadian Journal of Physiology and Pharmacology 87, n^o 12 (décembre 2009) : 989–95. http://dx.doi.org/10.1139/y09-102.

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A growing body of evidence supports the role of redox signaling in the mechanisms of hematopoietic stem cell mobilization and homing. Cytokines and adhesion molecules control stem cell mobilization through a redox-regulated process. The FoxO–SirT network appears to be intimately involved in redox-regulated stem cell homeostasis, whereas the process of stem cell differentiation is regulated by redox effector factor-1 (Ref-1) protein. Lack of oxygen (hypoxia), specifically controlled hypoxia, can stimulate the growth of the stem cells in their niche, and hypoxia-inducible factor (HIF)-1α appears to play a significant role in their maintenance and homing mechanism.

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Articles de revues sur le sujet « Leukaemia, Stem cells, Hypoxia, HIF »

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