Добірка наукової літератури з теми "BRAFV600E oncogene"

10059 Background: Circulating tumor DNA (ctDNA) analysis has been promoted as a less-invasive surrogate assay for tumor-tissue based tumor oncogene analysis. Here, we associate detection of BRAF mutant ctDNA with PFS and OS in patients with tissue-confirmed BRAFV600 mutant melanoma enrolled in S1320, a randomized phase 2 clinical trial of continuous versus intermittent dosing of dabrafenib and trametinib. Methods: Patients with BRAFV600 melanoma received continuous therapy with dabrafenib and trametinib for 8 weeks after which patients were randomized 1:1 to proceed with intermittent treatment on a 3-week-off, 5-week-on schedule or to continue with continuous therapy. Pre-treatment blood samples were interrogated using the Guardant 360 ctDNA assay for all exons of 30 known oncogenes including BRAF and for all exons with known oncogenic mutations in the COSMIC database in 40 additional oncogenes. Clinical responses were assessed at 8-week intervals by RECIST v1.1 and PFS and OS estimates were compared using log-rank test in patients with detectable versus undetectable BRAFV600 mutant ctDNA,. Results: Somatic BRAFV600E or BRAFV600K ctDNA was detected in 34 of 50 patients with baseline (before lead-in cycle 1) blood samples available for analysis including 16 of 23 (70%) patients randomized to continuous dosing, 15 of 21 (71%) randomized to intermittent dosing, and 3 of 6 (50%) who were not randomized due to disease progression at 8 weeks or other factors. Four additional patients had other detectable somatic mutations but no detectable BRAFV600 ctDNA at baseline, and 12 patients had no detectable somatic ctDNA mutations at baseline. Detection of BRAFV600 ctDNA was associated with baseline disease stage (p = 0.008). There was no difference in the overall response rate based on baseline ctDNA detection. Detection of ctDNA at baseline was associated with worse PFS (median BRAFV600 ctDNA positive = 5.8; 95% CI: 4.2-9.6 months, BRAFV600 ctDNA negative = 21.4 mos; 95% CI 10.4-NA; measured from registration to lead-in cycle 1, p = 0.001) and OS (BRAFV600 ctDNA positive = 17.8 mos; 95% CI 9.76-NA, BRAFV600 ctDNA negative = not reached; 95% CI NA-NA, p = 0.0021). Conclusions: The absence of detectable BRAFV600 ctDNA at baseline is associated with improved PFS and OS in patients receiving treatment with dabrafenib and trametinib. Clinical trial information: NCT02196181.

Childhood papillary thyroid carcinoma (PTC) diagnosed after the Chernobyl accident in Belarus displayed a high frequency of gene rearrangements and low frequency of point mutations. Since 2001, only sporadic thyroid cancer occurs in children aged up to 14 years but its molecular characteristics have not been reported. Here, we determine the major oncogenic events in PTC from non-exposed Belarusian children and assess their clinicopathological correlations. Among the 34 tumors, 23 (67.6%) harbored one of the mutually exclusive oncogenes: 5 (14.7%) BRAFV600E, 4 (11.8%) RET/PTC1, 6 (17.6%) RET/PTC3, 2 (5.9%) rare fusion genes, and 6 (17.6%) ETV6ex4/NTRK3. No mutations in codons 12, 13, and 61 of K-, N- and H-RAS, BRAFK601E, or ETV6ex5/NTRK3 or AKAP9/BRAF were detected. Fusion genes were significantly more frequent than BRAFV600E (p = 0.002). Clinicopathologically, RET/PTC3 was associated with solid growth pattern and higher tumor aggressiveness, BRAFV600E and RET/PTC1 with classic papillary morphology and mild clinical phenotype, and ETV6ex4/NTRK3 with follicular-patterned PTC and reduced aggressiveness. The spectrum of driver mutations in sporadic childhood PTC in Belarus largely parallels that in Chernobyl PTC, yet the frequencies of some oncogenes may likely differ from those in the early-onset Chernobyl PTC; clinicopathological features correlate with the oncogene type.

BRAF (v-raf murine sarcoma viral oncogene homolog B) inhibitors elicit a transient anti-tumor response in ∼80% of BRAFV600-mutant melanoma patients that almost uniformly precedes the emergence of resistance. Here we used a mouse model of melanoma in which melanocyte-specific expression of BrafV618E (analogous to the human BRAFV600E mutation) led to the development of skin hyperpigmentation and nevi, as well as melanoma formation with incomplete penetrance. Sleeping Beauty insertional mutagenesis in this model led to accelerated and fully penetrant melanomagenesis and synchronous tumor formation. Treatment of BrafV618E transposon mice with the BRAF inhibitor PLX4720 resulted in tumor regression followed by relapse. Analysis of transposon insertions identified eight genes including Braf, Mitf, and ERas (ES-cell expressed Ras) as candidate resistance genes. Expression of ERAS in human melanoma cell lines conferred resistance to PLX4720 and induced hyperphosphorylation of AKT (v-akt murine thymoma viral oncogene homolog 1), a phenotype reverted by combinatorial treatment with PLX4720 and the AKT inhibitor MK2206. We show that ERAS expression elicits a prosurvival signal associated with phosphorylation/inactivation of BAD, and that the resistance of hepatocyte growth factor-treated human melanoma cells to PLX4720 can be reverted by treatment with the BAD-like BH3 mimetic ABT-737. Thus, we define a role for the AKT/BAD pathway in resistance to BRAF inhibition and illustrate an in vivo approach for finding drug resistance genes.

Background: The incidence of thyroid cancer is increasing worldwide at an alarming rate. BRAFV600E mutation is described to be associated with a worse prognostic of thyroid carcinomas, as well as extrathyroidal invasion and increased mortality. Objective: To our knowledge, there are no reported studies neither from Morocco nor from other Maghreb countries re- garding the prevalence of BRAFV600E mutation in thyroid carcinomas. Here we aim to evaluate the frequency of BRAFV600E oncogene in Moroccan thyroid carcinomas. Methods: In this Single-Institution retrospective study realized in the Anatomic Pathology and Histology Service in the Mil- itary Hospital of Instruction Mohammed V ‘HMIMV’ in Rabat, we report, using direct genomic sequencing, the assessment of BRAFV600E in 37 thyroid tumors. Results: We detected BRAFV600E mutation exclusively in Papillary Thyroid Carcinomas ‘PTC’ with a prevalence of 28% (8 PTC out 29 PTC). Like international trends, Papillary Thyroid Carcinomas ’PTC’ is more frequent than Follicular Thyroid Carcinomas ‘FTC’ and Anaplastic Thyroid Carcinomas ‘ATC’ (29 PTC, 7 FTC and 1 ATC). Conclusion: Our finding gives to the international community the first estimated incidence of this oncogene in Morocco showing that this prevalence falls within the range of international trends (30% to 90%) reported in distinct worldwide ge- ographic regions. Keywords: Biomarker; BRAFV600E; Thyroid cancer; Morocco.

Background: The B-Raf proto-oncogene (BRAFV600E) gene mutation has been identified in a variety of malignancies, but no evidence of the efficacy of vemurafenib treatment in BRAFV600E mutant breast cancer (BC) has been reported. Case Presentation: We reported a 60-year-old woman with confirmed triple-negative BC with BRAFV600E mutation. Progression-free survival (PFS) for first-line chemotherapy was 7 months. The patient received vemurafenib and albumin-bound paclitaxel as second-line therapy, exhibiting regression of some pulmonary metastatic lesions with concomitant progression of other lesions, and achieved 4.4 months of PFS. Genetic testing of the progressed pulmonary lesion revealed the BRAFV600E mutation, and acquired new mutations and AR amplification. The patient ultimately died of multiple organ failure and achieved 12 months of overall survival. Conclusions: The BRAFV600E mutation may be a potential prognostic factor and therapeutic target for BC.

Histopathological changes in the fusion oncogene-driven papillary thyroid carcinomas (PTCs) from children and adolescents exposed to Chernobyl fallout have been extensively studied. However, characteristics of the radiogenic BRAFV600E-positive PTCs, whose proportion is growing with time, are not well described yet. We analyzed the relationship between the BRAFV600E status (determined immunohistochemically with the VE1 antibody) and the clinicopathological features of 247 radiogenic and 138 sporadic PTCs from young Ukrainian patients aged ≤28 years. The frequency of BRAFV600E was increasing with patient age, consistently remaining lower in radiogenic PTCs. In both etiopathogenic groups, the BRAFV600E-positive PTCs more frequently had a dominant papillary growth pattern, smaller tumor size, higher Ki67 labeling index, and a frequency of the major indicators of tumor invasiveness that is lower than or equal to that of the BRAFV600E-negative tumors. Comparison of the BRAFV600E-positive PTCs across the groups found a virtual absence of differences. In contrast, the BRAFV600E-negative radiogenic PTCs displayed less frequent dominant papillary and more frequent solid growth patterns, lower Ki67 labeling index, and higher invasiveness than the BRAFV600E-negative sporadic tumors. Thus, BRAFV600E is not associated with a more aggressive course of PTC in young patients regardless of etiology. The major clinicopathological differences between the radiogenic and sporadic PTCs are observed among the BRAFV600E-negative tumors.

Vemurafenib is a selective inhibitor of overactive BRAF oncogene with a substitution of lysine for glutamic acid at residue 600 (BRAFV600E), a mutation expressed in approximately 50% of all melanomas. We report a case of a patient with metastatic melanoma treated with vemurafenib, who subsequently presented with a biopsy-proven conventional renal cell carcinoma (RCC). We observed an initial complete regression of the mass while on vemurafenib. This was unexpected, given that vemurafenib is a specific inhibitor of BRAFV600E and most RCCs do not harbour this mutation.

Abstract Regulatory T cells (Tregs) are critical mediators of tumor immune suppression. While Tregs are found in established tumors, little is known about the kinetics and dynamics of Treg accumulation and the factors promoting it during oncogene-driven tumorigenesis. The present studies characterize Treg response kinetics and conversion dynamics during early tumor development in a model of autochthonous, tamoxifen-inducible BrafV600E Pten−/− melanoma. While microscopic skin dysplasia appeared 16 days following tumor induction, FoxP3+ Treg frequency and absolute numbers accumulated by day 26, coinciding with locally-invasive neoplasm development. BrafV600E inhibition with PLX4720 prevented Treg accumulation, suggesting that oncogenic Braf controls this process. Following adoptive transfer of CD4+ T cells specific to TRP-1, antigen-specific FoxP3+ Tregs preferentially accumulated in tumor-induced skin and draining lymph nodes (dLNs), as compared to tumor-free counterparts. In contrast, depleting Tregs prior to transfer abrogated the TRP-1-specific Treg response, suggesting a predominant role for natural Tregs. Furthermore, we observed an increase in chemokine (C-C motif) ligand 17 (Ccl17) and Ccl2 prior to Treg influx to tumor-induced skin. Oncogenic Braf regulated expression of Ccl17 and Ccl2, both of which mediated Treg migration in vitro. We are currently investigating the putative role of Ccl17/2-Ccr4 chemotactic axis in Treg recruitment to sites of Braf-driven tumorigenesis in vivo.

Deregulated extracellular signal-regulated kinase (ERK) signaling drives cancer growth. Normally, ERK activity is self-limiting by the rapid inactivation of upstream kinases and delayed induction of dual-specificity MAP kinase phosphatases (MKPs/DUSPs). However, interactions between these feedback mechanisms are unclear. Here we show that, although the MKP DUSP5 both inactivates and anchors ERK in the nucleus, it paradoxically increases and prolongs cytoplasmic ERK activity. The latter effect is caused, at least in part, by the relief of ERK-mediated RAF inhibition. The importance of this spatiotemporal interaction between these distinct feedback mechanisms is illustrated by the fact that expression of oncogenic BRAFV600E, a feedback-insensitive mutant RAF kinase, reprograms DUSP5 into a cell-wide ERK inhibitor that facilitates cell proliferation and transformation. In contrast, DUSP5 deletion causes BRAFV600E-induced ERK hyperactivation and cellular senescence. Thus, feedback interactions within the ERK pathway can regulate cell proliferation and transformation, and suggest oncogene-specific roles for DUSP5 in controlling ERK signaling and cell fate.

Papillary thyroid carcinoma (PTC) is the most frequent histological subtype of thyroid cancers (TC), and BRAFV600E genetic alteration is found in 60% of this endocrine cancer. This oncogene is associated with poor prognosis, resistance to radioiodine therapy, and tumor progression. Histological follow-up by anatomo-pathologists revealed that two-thirds of surgically-removed thyroids do not present malignant lesions. Thus, continued fundamental research into the molecular mechanisms of TC downstream of BRAFV600E remains central to better understanding the clinical behavior of these tumors. To study PTC, we used a mouse model in which expression of BRAFV600E was specifically switched on in thyrocytes by doxycycline administration. Upon daily intraperitoneal doxycycline injection, thyroid tissue rapidly acquired histological features mimicking human PTC. Transcriptomic analysis revealed major changes in immune signaling pathways upon BRAFV600E induction. Multiplex immunofluorescence confirmed the abundant recruitment of macrophages, among which a population of LYVE-1+/CD206+/STABILIN-1+ was dramatically increased. By genetically inactivating the gene coding for the scavenger receptor STABILIN-1, we showed an increase of CD8+ T cells in this in situ BRAFV600E-dependent TC. Lastly, we demonstrated the presence of CD206+/STABILIN-1+ macrophages in human thyroid pathologies. Altogether, we revealed the recruitment of immunosuppressive STABILIN-1 macrophages in a PTC mouse model and the interest to further study this macrophage subpopulation in human thyroid tissues.

Nella terapia genica (GT) delle cellule staminali e progenitrici ematopoietiche (HSPC), la mutagenesi inserzionale può portare all'attivazione dell'oncogene, aumentando il rischio di leucemia nei pazienti. Inoltre, le HSPC umane che esprimono hBRAFV600E, se trapiantate in topi immunodepressi, inducono un fallimento letale del midollo osseo (BM) anche in piccole quantità. Questo fenotipo aggressivo è dovuto all'attivazione della senescenza, caratterizzata da un blocco del ciclo cellulare e da un fenotipo secretorio associato alla senescenza, che colpisce anche le cellule bystander non mutate. Pertanto, è fondamentale analizzare l'attivazione dell'oncogene nelle HSPC, in quanto rappresenta un rischio che precede la trasformazione maligna. Per studiare il destino delle cellule senescenti in presenza o in assenza di un sistema immunitario attivo, abbiamo trapiantato topi NSG o immunocompetenti (WT) con HSPC di topo (m) trasdotte con vettori lentivirali che esprimono mBrafV600E, una versione troncata all'N-terminale (mBraf-trunc), o GFP come controllo. Nei topi recipienti NSG, l'espressione di mBraf-trunc e mBrafV600E ha causato una letalità dose-dipendente e una ridotta cellularità, quest'ultima risultante in un fenotipo più aggressivo. A differenza del modello umanizzato, solo le cellule linfoidi esprimenti mBrafV600E sono risultate compromesse, ma non le cellule bystander. Analisi trascrizionali hanno mostrato l'aumento di espressione dei geni inibitori del ciclo cellulare Cdkn2d e Cdk2ap2, ma non Cdkn2a o Cdkn1a. Gli hallmarks di cui è aumentata l'espressione sono stati il TNFα signaling, le vie dello stress ossidativo e l'apoptosi. I processi downregolati sono stati la biogenesi dei ribosomi, la segnalazione dell'interferone e la risposta immunitaria innata (MHC di classe II) e adattativa. Invece, nei topi recipienti WT, abbiamo osservato una ridotta letalità (solo il 60%) e una completa eliminazione delle cellule che esprimono l'oncogene nei topi mBrafV600E sopravvissuti, suggerendo che la competenza immunologica dei riceventi promuove una più efficiente eliminazione delle cellule senescenti. L'analisi trascrizionale ha mostrato una soppressione immunitaria simile a quella avvenuta negli NSG, ma gli hallmarks espressi erano legati alla regolazione del ciclo cellulare, al checkpoint G2/M, ai bersagli di E2F, alla replicazione del DNA e ai processi di riparazione nelle cellule B. Questo suggerisce che le cellule B stanno potenzialmente sfuggendo alla senescenza e tornano al ciclo cellulare. Questo studio aspira a identificare biomarcatori specie-specifici o universali per studi GT preclinici e clinici e a riconoscere i fattori che determinano la resilienza/cancellazione delle cellule senescenti, suggerendo strategie per la loro eliminazione.
In hematopoietic stem and progenitor cell (HSPC) gene therapy (GT), insertional mutagenesis may result in oncogene activation, increasing the risk of leukemia in patients. Moreover, hBRAFV600E-expressing human HSPCs transplanted into immune-deficient mice, even in small numbers, induce lethal bone marrow (BM) failure. This aggressive phenotype is due to the engagement of senescence, characterized by cell cycle blockade and a senescence-associated secretory phenotype, affecting also non-mutated bystander cells. Thus, it is fundamental to describe oncogene activation in HSPCs, since it poses risks before the malignant transformation. To investigate the fate of senescent cells in the presence or absence of an active immune system, we transplanted NSG or immune-competent (WT) mice with mouse (m) HSPCs transduced with lentiviral vectors expressing mBrafV600E, an N-truncated version (mBraf-trunc), or GFP as control. In NSG recipients, mBraf-trunc and mBrafV600E expression caused dose-dependent lethality and reduced cellularity, the latter resulting in a more aggressive phenotype. As opposed to the humanized model, only mBrafV600E-lymphoid cells were impaired, but not bystander cells. Transcriptional profiling showed upregulated cell cycle inhibitor genes Cdkn2d and Cdk2ap2, not Cdkn2a or Cdkn1a. Hallmarks upregulated were TNFα signaling, oxidative stress pathways, and apoptosis. Downregulated processes were ribosome biogenesis, interferon signaling, and innate (MHC class II) and adaptive immune response. Instead, in WT recipients, we observed reduced lethality (only 60%) and complete clearance of oncogene-expressing cells in the surviving mBrafV600E mice, suggesting that the immunological competence of recipients promotes a more efficient clearance of senescent cells. Transcriptional analysis showed similar immune suppression to NSG, but upregulated hallmarks were related to cell cycle, G2/M checkpoint, E2F targets, DNA replication, and repair processes in B cells. This suggests that B cells are potentially escaping senescence and returning to the cell cycle. This study aspires to identify species-specific or universal biomarkers for pre-clinical and clinical GT studies and to recognize factors determining the resilience/clearance of senescent cells, suggesting strategies for their elimination.

This thesis examines the concept that human naevi are permanently arrested via the oncogene-induced senescence and investigates the role of p53 function in melanocyte responses to oncogenic mitogen-activated protein kinase (MAPK) pathway activity. We demonstrate that a panel of common markers of senescence are collectively unable to distinguish melanocytes from naevi and melanoma, questioning the proposition that naevi are composed of senescent cells. We also examined the signalling pathways involved in the oncogene-induced senescence of cultured melanocytes and found that levels of p53 rapidly diminished in response to ectopic BRAFV600E, an activator of MAPK activity and major oncogenic driver of melanoma. Importantly, we confirmed that p53-downregulation is transcriptional and we identified potential p53 regulators via whole-genome microarray analyses. We next sought to establish whether p53 is upregulated in response to MAPK pathway inhibition (a first-line therapy for patients with BRAFV600-mutant advanced melanoma). Initially, we analysed isogenic, colorectal cancer cell models and found that p53-loss diminished the sensitivity of these cancer cells to the MAPK inhibitor, trametinib. Although, sensitivity to trametinib was not significantly altered by p53-loss in the melanoma cells, our data suggest that melanoma cells do not potently induce p53 accumulation in response to MAPK inhibition.

Une des propriétés majeures de la thyroïde est de capter l’iode de la circulation sanguine grâce à la présence d’un transporteur d’iodure (NIS pour Natrium Iodide Symporter). Cette capacité d’accumulation d’iode par les thyrocytes joue un rôle clé dans la synthèse des hormones thyroïdiennes ainsi dans le diagnostic et le traitement des cancers de la thyroïde. Cependant, en raison d’une diminution ou de l’absence de l’expression du NIS dans certaines tumeurs et métastases, des patients deviennent réfractaires à la radiothérapie métabolique et présentent une radiorésistance, causant ainsi un problème de santé publique.L’oncogène BRAFV600E, un puissant activateur de La voie MAP kinase, est détecté dans 40 - 60% des cancers thyroïdiens de type papillaires (CPT) qui représentent 80% de la totalité des cancers thyroïdiens. La mutation BRAFV600E est associée aux tumeurs thyroïdiennes les plus agressives. Cependant l’inhibition pharmacologique de la voie MAP kinase induite constitutivement par l’oncogène BRAFV600E ne permet pas, à elle seule, de rétablir l’expression du NIS chez des patients atteints d’un cancer de la thyroïde muté BRAFV600E. Ceci suggère que d’autres mécanismes compensatoires peuvent contribuer à la radiorésistance. Une étude récente menée sur un modèle murin a montré que la régulation négative du NIS par l’oncogène BRAFV600E est médiée par la voie du TGF beta. Une autre a montré que l’expression du NIS serait dépendante de l’état redox de la cellule, suggérant un rôle des espèces réactives de l’oxygène (ROS). Dans les cellules les ROS peuvent être produites par les NADPH oxydases (NOX/DUOX). La thyroïde en exprime trois : DUOX2 nécessaire à la synthèse des hormones thyroïdiennes ainsi que DUOX1 et NOX4 dont le rôle physiologique reste inconnu. NOX4, surexprimé dans les CPTs, a été montré être un nouvel effecteur clé de la voie du TGF beta dans d’autres cancers.Dans mon projet de thèse, je me suis intéressée à l’étude du rôle de NOX4 dans la régulation négative du NIS dans les CPT mutés BRAFV600E. L’étude du mécanisme, réalisée à partir de deux lignées humaines issues de cancers papillaires mutés pour BRAF (BCPAP et 8505C), a permis d’établir que l’oncogène BRAFV600E contrôle l’expression de NOX4 au niveau transcriptionnel via la voie TGF-beta/Smad3. Ces résultats ont été validés sur une lignée de rat exprimant de manière conditionnelle BRAFV600E ainsi que sur des thyrocytes humains en culture primaire. De manière importante, l’utilisation d’antioxydants tels que le N-acetyl cystéine (NAC) ou l’inhibition spécifique de l’expression de NOX4 par ARN interférence permet de réinduire l’expression du NIS. Ces résultats qui montrent que les ROS produites par NOX4 inhibent l’expression du transporteur de l’iode (NIS) établissent un lien entre l’oncogène BRAFV600E et NOX4. Une analyse comparative de l'expression de NOX4 effectuée à partir de 500 cancers papillaires de la thyroïdes mutés ou non pour BRAF (données TCGA) confirme que NOX4 est significativement augmenté dans les cancers porteurs de la mutation BRAF et que ceci est corrélé à une diminution de l’ARNm du NIS. Par ailleurs, le niveau de NOX4 est inversement corrélé au score de différenciation thyroïdien, suggérant que NOX4 pourrait être impliqué dans le processus de dédifférenciation. Cette étude ouvre une nouvelle opportunité pour l’optimisation de l’utilisation de la radiothérapie métabolique dans le traitement des cancers thyroïdiens réfractaires à l’iode I131 et présente NOX4 comme une cible thérapeutique potentielle
One of the major properties of the thyroid is iodine uptake from the bloodstream through an iodide transporter (NIS for Natrium Iodide Symporter). This capacity plays a key role in the thyroid hormones synthesis, but also in both diagnosis and treatment of thyroid cancer. However, due to a decrease or absence of the NIS expression in some tumors and metastases, patients become refractory to the metabolic radiotherapy and present a radioresistance, which cause a public health problem.The BRAFV600E oncogene, a potent activator of the MAP kinase pathway, is detected in 40-60% of papillary thyroid cancer (PTC), which represent 80% of total thyroid cancers. The BRAFV600E mutation is associated with the more aggressive thyroid tumors. However, the pharmacological inhibition of the MAP kinase pathway, constitutively induced by the BRAFV600E oncogene, is not able to restore alone the expression of NIS in patients with BRAFV600E mutated thyroid cancer. This suggests that other compensatory mechanisms may contribute to the radioresistance. A recent study in a mouse model demonstrated that downregulation of NIS by BRAFV600E oncogene is mediated through the TGF beta activation. An other showed that the expression of NIS is dependent on the redox status of the cell, suggesting a role for the reactive oxygen species (ROS). In cells, ROS can be produced by the NADPH oxidases (NOX/DUOX). The Thyroid gland expresses three of them: DUOX2, which is necessary for the thyroid hormones synthesis, but also DUOX1 and NOX4 whose the physiological role remains unknown. NOX4, which is overexpressed in the PTCs, has been shown to be a new key effector of the TGF beta pathway.In my thesis project, I was interested in studying the role of NOX4 in the negative regulation of NIS in BRAFV600E mutated CPT. The study of the mechanism, made from two human cell lines derived from BRAF-mutated papillary thyroid cancers (BCPAP and 8505C), has revealed that the oncogene BRAFV600E controls the expression of NOX4 at the transcriptional level via the TGF-beta/Smad3 pathway. These results were validated on both a rat thyroid cell line conditionnaly expressing BRAFV600E and on human thyrocytes in primary culture. Importantly, the use of antioxidants such as N-acetyl cysteine (NAC) or specific inhibition of NOX4 expression by RNA interference allow reinduction of NIS expression. These results, which show that ROS produced by NOX4 inhibit the expression of iodine transporter (NIS), establish a link between the oncogene BRAFV600E and NOX4. A comparative analysis of the NOX4 expression, made from 500 papillary thyroid cancers mutated or not for BRAF (TCGA data), confirms that NOX4 is significantly increased in BRAF-mutated cancers and that this is correlated with a decrease of NIS mRNA. Furthermore, the level of NOX4 is inversely related to thyroid differentiation score, suggesting that NOX4 might be involved in the dedifferentiation process. This study opens a new opportunity for optimizing the use of metabolic radiotherapy in the treatment of thyroid cancers refractory to radioiodine I131and makes NOX4 as a potential therapeutic target

La radiothérapie métabolique à l'iode radioactif est la pierre angulaire du traitement des métastases à distance des cancers différenciés de la thyroïde. Cette thérapie est basée sur l'expression à la membrane basale des thyrocytes du transporteur de l'iode appelé NIS pour « Natrium Iodide Symporter ». La mutation BRAFV600E est présente dans 45 à 60 % des cancers papillaires de la thyroïde qui représentent 80% des cancers thyroïdiens. La présence de cette mutation est associée aux tumeurs thyroïdiennes les plus agressives avec un faible niveau ou une absence d'expression du NIS. La perte de la captation d'iode radioactif se traduit par la résistance à la radiothérapie métabolique constituant un enjeu majeur pour le traitement des patients atteints de ce cancer. L'une des approches pour le traitement des patients réfractaires à la radiothérapie métabolique consiste à augmenter l'absorption de l'iode.Au niveau transcriptionnel, notre équipe a déjà montré, à travers une analyse comparative qui porte sur environ 500 PTCs de la base de données TCGA, que NOX4 est fortement exprimée dans les PTCs-BRAFV600E comparativement aux PTCs-BRAFwt. Néanmoins, au niveau protéique, aucun lien n'a été établie entre la mutation BRAFV600E et NOX4 dans les tumeurs malignes et non malignes (BRAFV600E/BRAFwt). Dans mon projet de thèse, nous illustrons pour la première fois une corrélation positive entre la présence de la mutation BRAFV600E et la surexpression de la protéine NOX4 dans les tissus tumoraux PTCs. La surexpression de NOX4 est associée au caractère agressif des tumeurs. De plus, nous avons montré que 60% des C-PTCs infiltrant surexpriment NOX4 indépendamment du statut mutationnel de BRAF, ce qui suggère que NOX4 pourrait être considérée comme un co-marqueur potentiel de l'agressivité des PTCs. De manière intéressante la protéine NOX4 était également surexprimée dans les maladies thyroïdiennes non malignes (les Basedow, goitres et hyperplasies) avec différentes localisations subcellulaires, suggérant un rôle de NOX4 dans la progression vers la malignité thyroïdienne.Par ailleurs, sur le plan mécanistique, notre équipe a précédemment montré que BRAFV600E contrôle l'expression de NOX4 sous l'effet de TGF-β /SMAD3 et que les ERO dérivées de NOX4 contribuent à la répression du NIS. L'inhibition de NOX4 favorise la réactivation du NIS. Cette réversibilité suggère une contribution à un mécanisme épigénétique. CHD4, une sous-unité du complexe du remodelage NuRD, joue un rôle important dans la répression des gènes. Elle est fortement exprimée dans les PTCs dans lequel elle est associée à un mauvais pronostic. Dans cette étude, nous avons montré que la voie TGF-β/SMAD3 régule l'expression de la protéine CHD4. Cette dernière coopère avec les DNMTs dans la répression du NIS dans plusieurs lignées thyroïdiennes tumorales mutées pour BRAFV600E. Par ailleurs, nous montrons que CHD4 répond aux dommages oxydatifs à l'ADN induites par les ERO dérivés de NOX4. En effet, l'inhibition de NOX4 ou de son partenaire fonctionnel p22phox, induit une diminution du recrutement de CHD4 à la chromatine. Ce recrutement est dépendant d'OGG1 et MSH6, deux protéines impliquées dans la réparation des dommages oxydatifs à l'ADN. Cette étude identifie CHD4 en tant que nouvelle cible thérapeutique dans les tumeurs thyroïdiennes réfractaires à la radiothérapie métabolique
Metabolic radiotherapy with radioiodine is the cornerstone of the treatment of distant metastases of differentiated thyroid cancers. This therapy depends on the expression at the basal membrane of thyrocytes of the Natrium Iodide Symporter 'NIS'. BRAFV600E mutation is present in 45 to 60% of papillary thyroid carcinomas, which represent 80% of thyroid cancers. The presence of this mutation is associated with the most aggressive thyroid tumors with low levels or absence of NIS expression. The loss of radioactive iodine uptake translates into resistance to metabolic radiotherapy, constituting a major issue for the treatment of patients with this cancer. One approach for treating patients refractory to metabolic radiotherapy is to increase iodine uptake.At the transcriptional level, our team has already shown, through a comparative analysis concerning approximately 500 PTCs from the TCGA database, that NOX4 was strongly expressed in PTCs-BRAFV600E compared to PTCs-BRAFwt. However, at the protein level, no link has been established between the BRAFV600E mutation and NOX4 in malignant and non-malignant tumors (BRAFV600E/BRAFwt). In my thesis project, we illustrate for the first time a positive correlation between the presence of BRAFV600E mutation and the overexpression of NOX4 protein in PTC tumor tissues. The overexpression of NOX4 was associated with an aggressive nature of tumors. Furthermore, we showed that 60% of infiltrating C-PTCs overexpress NOX4 independently of BRAF mutational status, suggesting that NOX4 could be considered as a potential co-marker of PTC aggressiveness. Interestingly, NOX4 protein was also overexpressed in non-malignant thyroid diseases (Basedow, goiters, and hyperplasias), with different subcellular localizations, suggesting a role for NOX4 in progression to thyroid malignancy.Furthermore, on a mechanistic level, our team has previously shown that BRAFV600E controls the expression of NOX4 under the effect of TGF-β/SMAD3 and that NOX4-derived ROS contribute to the repression of NIS. Inhibition of NOX4 promotes reactivation of the NIS. This reversibility suggests a contribution to an epigenetic mechanism. CHD4, a subunit of the NuRD remodeling complex, plays an essential role in gene repression. it was found to be strongly expressed in PTCs, in which it was associated with a poor prognosis. In this study, we showed that the TGF-β/SMAD3 pathway regulates the expression of CHD4 protein. The latter cooperates with DNMTs in repressing NIS in several thyroid tumor cells lines mutated for BRAFV600E. Furthermore, we showed that CHD4 responds to oxidative DNA damage induced by NOX4-derived ROS. Indeed, inhibition of NOX4 or its functional partner p22phox reduces the recruitment of CHD4 to chromatin. This recruitment depends on OGG1 and MSH6, two proteins involved in oxidative DNA damage repair. This study identifies CHD4 as a new therapeutic candidate in radioiodine-refractory thyroid cancers

Cutaneous melanoma, the most aggressive form of skin cancer, remains one of the most difficult to treat human malignancies. 40-50% of melanomas are characterized by the expression of oncogenic BRAF, with BRAFV600E being the most represented mutation. The well-known BRAFV600E-induced resistance to therapy remains an obstacle to the succesfull treatment and highlights the urgent need of in-depht studies to increase our knowledge on biochemical and molecular characteristics of this cancer in order to develop novel effective and longlasting therapeutic strategies. Autophagy and ER stress are pro-survival mechanisms, strongly linked to each other, involved in melanoma development, progression and chemoresistance. In the first part of this Ph.D project we show that BRAFV600E induces a chronic ER stress status increasing basal cell autophagy. BRAFV600E-mediated p38 activation stimulates both IRE1/ASK1/JNK and PERK/ATF4/TRB3 pathways. Bcl-XL/Bcl-2 phosphorylation by active JNK releases Beclin1 whereas TRB3 inhibits mTor, together resulting in an increase in cell basal autophagy. Furthermore, we demonstrate that chemical chaperones relieve the BRAFV600E-mediated chronic ER stress status, consequently reducing basal autophagic activity resulting in re-sensitization of melanoma cells to apoptosis. Although the immunosurveillance constantly reduces the risk of cancer development, melanoma and other tumours evolved effective strategies to efficiently evade this control. On the other hand, it is now known that chemotherapeutic agents, such as mitoxantrone (MTX) and doxorubicine (DOXO), are able to induce cancer cell death pathways involving the immune system. The immunogenic cell death (ICD) process involves the emission of so-called DAMPs (damage-associated molecular patterns) from dying cancer cells, able to activate the immune system against the tumour. The combined activity of pro-death drugs and the immune system results in a most effective eradication of the tumour. In the second part of this Ph. D project we show that MTX and DOXO are able to induce cell death and stimulate, at the same time, the release/exposure of the four strictly required DAMPs, in melanoma cell lines: i) exposure of the endoplasmic reticulum (ER) resident protein calreticulin (CRT) on cell membrane; ii) ATP secretion; iii) type I IFNs production and iv) HMGB1 secretion. Importantly, the presence of oncogenic BRAF does not interfere with ICD induction. We further investigated the role of the ER stress in the exposure of CRT, concluding that this mechanism is not involved, at least in our model. Altogether, on one hand these results suggest that enhanced basal autophagy, typically observed in BRAFV600E melanomas, is a consequence of a chronic ER stress status, which ultimately results in the chemoresistance of such tumours, therefore targeted therapies that attenuate ER stress may represent a novel and more effective therapeutic strategy for BRAF mutant melanoma. On the other hand, our result suggest that exploiting the ability of chemotherapeutical compounds such as MTX and DOXO to stimulate the release/exposure of ICD-related DAMPs might represents a feasible route in the developing of a valid and alternative strategy for the treatment of cutaneous melanoma. Therefore it is necessary to deepen the understanding and the potentiality of this therapeutic strategy by using in vivo models.

Melanoma, the most lethal form of skin cancer, arises from altered cells in the melanocyte lineage, but the mechanisms by which these cells progress to melanoma are unknown. To understand the early cellular events that contribute to melanoma formation, we examined melanocytes in melanoma-prone zebrafish strains expressing BRAFV600E, the most common oncogenic form of the BRAF kinase that is mutated in nearly 50% of human melanomas. We found that, unlike wild-type melanocytes, melanocytes in transgenic BRAFV600Eanimals were binucleate and tetraploid. Furthermore, melanocytes in p53-deficient transgenic BRAFV600Eanimals exhibited 8N and greater DNA content, suggesting bypass of a p53-dependent arrest that stops cell cycle progression of tetraploid melanocytes. These data implicate tetraploids generated by increased BRAF pathway activity as contributors to melanoma initiation. Previous studies have used artificial means of generating tetraploids, raising the question of how these cells arise during actual tumor development. To gain insight into the mechanism by which BRAFV600E generates binucleate, tetraploid cells, we established an in vitro model by which such cells are generated following BRAFV600E expression. We demonstrate thatBRAFV600E-generated tetraploids arise via cytokinesis failure during mitosis due to reduced activity of the small GTPase RhoA. We also establish that oncogene-induced centrosome amplification in the G1/S phase of the cell cycle and subsequent increase in the activity of the small GTPase Rac1, partially contribute to this phenotype. These data are of significance as recent studies have shown that aneuploid progeny of tetraploid cells can be intermediates in tumor development, and deep sequencing data suggest that at least one third of melanomas and other solid tumors have undergone a whole genome doubling event during their progression. Taken together, our melanoma-prone zebrafish model and in vitro data suggest a role for BRAFV600E-inducedtetraploidy in the genesis of melanomas. To our knowledge, this is the first in vivo model showing spontaneous rise of tetraploid cells that can give rise to tumors. This novel role of the BRAF oncogene may contribute to tumorigenesis in a broader context.

L’histiocytose langerhansienne (HL) est la plus fréquente des histiocytoses, liée à l’accumulation de cellules pathologiques de phénotype langerhansien. La découverte de la mutation somatique BRAFV600E dans environ 50% des cas à ouvert un nouveau champ d’investigation pour tirer bénéfice de ce statut moléculaire pour la prise en charge des patients.Tout d’abord, nous avons montré l’efficacité des inhibiteurs de BRAF sans rapporter de résistance dans les formes actives d’HL, en particulier dans les formes multisystémiques avec atteinte des organes à risque (MS OR+) du nourrissons, confirmant le rôle driver de cette mutation dans l’HL. Toutefois, après l’arrêt du traitement administré durant 2 à 6 mois, de nombreuses récidives ont été constatées.Ensuite, nous avons montré que pour les enfants atteints d’HL, la mutation BRAFV600E était significativement associée aux formes MS OR+, retrouvée dans 87,8% de ces cas. Comparés aux patients non mutés BRAF, les patients avec la mutation BRAFV600E présentaient un taux de résistance plus élevé à la chimiothérapie de première ligne velbé - corticoïde (21,9% contre 3,3%), un taux plus élevé de réactivation à 5 ans (42,8% contre 28,1%) et un taux de séquelles supérieur (27,9% contre 12,6%).Par ailleurs, nous avons montré que, pour les HL BRAFV600E mutées, la quantification de BRAFV600E dans l’ADN libre circulant par PCR digitale en gouttelette était un biomarqueur pertinent pour les cas d’HL MS OR+ et les présentations résistantes au traitement de première ligne.Enfin, après un criblage de points chauds mutationnels d’une série d’échantillons tissulaires d’HL ayant permis de mettre en évidence un cas avec la mutation somatique PIK3CAE542K, 9 couples d’échantillons tumeur/constitutionnel ont été étudiés par séquençage d’exome. Cela nous a permis de mettre en évidence une mutation récurrente (n=2) de BRAF au niveau du site d’épissage 5’ (donneur) de l’intron 12. Selon l’analyse de l’ARN, cette mutation conduirait à l’insertion de 3 acides aminés (LLR) dans le domaine kinase de la protéine mutée, dont l’analyse fonctionnelle est en cours
Langerhans cell histiocytosis (LCH) is the most common type of histiocytosis owing to accumulation of pathologic CD1a+ CD207+ histiocytes. The identification of BRAFV600E in more than half of patients with LCH has launched a new field of investigation to study potential patient’s management benefits and implications from this molecular status.First, in BRAFV600E mutated LCH, we reported the effectiveness of BRAF inhibitors. Efficacy with no resistance to vemurafenib was reported in all cases with active LCH disease, especially for multi-system LCH with risk organ (MS RO+) involvement, confirming the driver status of this mutation in LCH. However, after discontinuation of this treatment administered during 2-6 months, many recurrences were observed.Then, we showed that children with BRAFV600E mutated LCH manifested more severe disease, comprised 87.8% of patients with MS RO+ involvement. Compared to patients with wild-type BRAF, patients with BRAFV600E more commonly displayed resistance to combined vinblastine and corticosteroid therapy (21.9% vs. 3.3%), showed a higher 5-year reactivation rate (42.8% vs. 28.1%) and had more long-term permanent consequences (27.9% vs. 12.6%).Moreover, we showed that BRAFV600E quantification in circulating cell-free DNA by droplet digital PCR is a relevant biomarker to monitor response to therapy for MS RO+ LCH and RO- LCH children who failed to respond to first line chemotherapy.Finally, after the screening of LCH biopsy (n=86) for the BRAF, KRAS, NRAS and PI3KCA most common mutations, leading to highlight one case with the PIK3CAE542K somatic mutation, 9 paired tumor-normal samples from children with LCH were analyzed by whole exome sequencing. Data showed a new BRAF recurrent mutation (n=2) in the 5′ splice sites of the intron 12. According to RNA analysis, this mutation would lead to the insertion of 3 amino acids (LLR) in the smaller N-terminal lobe of the BRAF kinase domain. Functional analysis is ongoing

Malignant melanoma is among the most aggressive cancers and its incidence is increasing worldwide. Although targeted therapies and immunotherapy have improved the survival of patients with metastatic melanoma in the last few years, available treatments are still unsatisfactory showing an urgent need to identify new therapeutic targets. While the role of BRAF-MEK1/2-ERK1/2 pathway in melanoma is well-established, the involvement of the MEK5-ERK5 signaling remains poorly explored. The Hedgehog signaling is an important pathway in melanoma, that has been shown to be required for growth, recurrence and metastasis of melanoma xenografts in mice. Several studies have shown that numerous oncogenic inputs positively modulate the activity of the HH pathway. In this study, we investigated the function of ERK5 signaling in melanoma, its regulation by oncogenic BRAF and its interplay with the HH pathway. We show that ERK5 is consistently expressed and active in human melanoma cells. Genetic silencing of ERK5 and pharmacological inhibition of the MEK5-ERK5 pathway drastically reduce the growth of melanoma cells harboring wild type (wt) or mutated BRAF (V600E), in vitro and in vivo. We also found that oncogenic BRAF positively regulates expression, phosphorylation and nuclear localization of ERK5. Importantly, BRAF enhances ERK5 kinase and transcriptional transactivator activities. Nevertheless, combined pharmacological inhibition of BRAF-V600E and MEK5 is required to decrease nuclear ERK5, that is critical for the regulation of cell proliferation. Accordingly, combination of MEK5 or ERK5 inhibitors with BRAF-V600E inhibitor Vemurafenib is more effective than single treatments in reducing the tumor growth of BRAF-V600E melanoma cells and xenografts. Moreover, we have also identified the existence of an interplay between the HH pathway and ERK5. By chemical and genetic inhibition of ERK5, we demonstrate that ERK5 positively modulates the HH pathway, increasing transcriptional activity and protein levels of the GLIs transcription factors, the final effectors of HH signaling. These data support a key role of ERK5 pathway for melanoma growth in vitro and in vivo and suggest that targeting ERK5, alone or in combination with BRAF-MEK1/2 inhibitors or HH pathway inhibitors, might represent a novel approach for melanoma treatment.