Project description:Adaptive resistance to targeted therapy such as BRAF inhibitors represents in melanoma a major drawback to this otherwise powerful treatment. Some of the underlying molecular mechanisms have recently been described: hyperactivation of the BRAF-MAPK pathway, of the AKT pathway, of the TGFβ/EGFR/PDGFRB pathway, or the low MITF/AXL ratio. Nevertheless, the phenomenon of early resistance is still not clearly understood. In this report, we show that knockdown of neural crest-associated gene ID3 increases the melanoma sensitivity to vemurafenib short-term treatment. In addition, we observe an ID3-mediated regulation of cell migration and of the expression of resistance-associated genes such as SOX10 and MITF. In sum, these data suggest ID3 as a new key actor of melanoma adaptive resistance to vemurafenib and as a potential drug target. Molecular mechanisms that are responsible for the development of human skin epithelial cells are not completely understood so far. As a consequence, the efficiency to establish a pure skin epithelial cell population from human induced pluripotent stem cells (hiPSC) remains poor. Using an approach including RNA interference and high-throughput imaging of early epithelial cells, we could identify candidate kinases which are involved in skin epithelial differentiation. Among them, we found HIPK4 to be an important inhibitor of this process. Indeed, its silencing increased the amount of generated skin epithelial precursors, increased the amount of generated keratinocytes and improved growth and differentiation of organotypic cultures, allowing for the formation of a denser basal layer and stratification with the expression of several keratins. Our data bring substantial input in the regulation of human skin epithelial differentiation and for improving differentiation protocols from pluripotent stem cells.
Project description:Adaptive resistance to targeted therapy such as BRAF inhibitors represents in melanoma a major drawback to this otherwise powerful treatment. Some of the underlying molecular mechanisms have recently been described: hyperactivation of the BRAF-MAPK pathway, of the AKT pathway, of the TGFβ/EGFR/PDGFRB pathway, or the low MITF/AXL ratio. Nevertheless, the phenomenon of early resistance is still not clearly understood. In this report, we show that knockdown of neural crest-associated gene ID3 increases the melanoma sensitivity to vemurafenib short-term treatment. In addition, we observe an ID3-mediated regulation of cell migration and of the expression of resistance-associated genes such as SOX10 and MITF. In sum, these data suggest ID3 as a new key actor of melanoma adaptive resistance to vemurafenib and as a potential drug target.
Project description:The development of drug resistance is a major limiting factor to the efficacy of BRAF inhibitor therapy for melanoma. The goal of this study was to identify and characterize pathways that contribute to adaptive drug resistance to BRAF inhibitors.
Project description:Despite the successful use of drugs targeting the MAPK signaling pathway and immunotherapy in melanoma, the majority of patients with metastatic disease still undergo disease progression indicating a gradual development of therapy resistance. In the present study, microarray analyses were performed on BRAF inhibitor sensitive melanoma cells A375 and corresponding vemurafenib (PLX4032) - resistant cells A375_X1 to describe changes in the transcriptome that might play a role in drug resistance. For each cell line the microarray experiment was performed in duplicates.
Project description:NRAS-mutant melanoma is currently a challenge to treat. This is due to an absence of inhibitors directed against NRAS, along with acquired and adaptive resistance of this tumor type to inhibitors in the MAPK pathway. Inhibitors to MEK (mitogen-activated protein kinase kinase) have shown some promise for this tumor type. In this work we explored the use of MEK inhibitors for NRAS-mutant melanoma, and at the same time investigated the impact of the brain micro-environment, specifically astrocytes, on the response of a melanoma brain metastatic cell line to MEK inhibition. This led to the surprising finding that astrocytes enhance the sensitivity of melanoma tumors to MEK inhibitors (MEKi). We show that MEKi cause an upregulation of the transcription factor ID3, but this is blocked by conditioned media from astrocytes. We show that silencing ID3 enhances the sensitivity of melanoma to MEK inhibitors, thus mimicking the effect of the brain microenvironment. Moreover, we report that ID3 is a client protein of the chaperone HSP70, and that HSP70 inhibition causes ID3 to misfold and accumulate in a detergent-insoluble fraction in cells. We show that HSP70 inhibitors synergize with MEK inhibitors against NRAS-mutant melanoma, and that this combination significantly enhances the survival of mice in two different models of NRAS-mutant melanoma. These studies highlight ID3 as a mediator of adaptive resistance, and support the combined use of MEK and HSP70 inhibitors for the therapy of NRAS-mutant melanoma.
Project description:Melanoma patients receiving drugs targeting BRAFV600E and MKK1/2 invariably develop resistance and continue progression, limiting the efficacy of treatment. As an alternative to continuous dosing schedules, intermittent treatment strategies involving intervening periods of drug withdrawal have been proposed to delay resistance. The efficacy of this treatment strategy has been supported by preclinical findings and several clinical case reports. The beneficial effect of intermittent treatment has been attributed to “drug addiction”, in which the cell viability of resistant cells is compromised during periods of drug removal, presumably due to MAPK pathway hyperactivation. However, the cellular and molecular responses to intermittent treatment are still incompletely understood. Here, we investigate effects of intermittent treatment with the BRAFV600E inhibitor, encorafenib, in a metastatic melanoma cell line engineered to express genes conferring resistance to BRAF inhibition. We show that intermittent treatment shows superior growth suppression compared to continuous treatment for resistant cells that substantially reactivate the MAPK pathway. While drug addiction is clearly observable in these cells, it fails to account for the advantageous effects of intermittent treatment. Instead, growth suppression can mainly be explained by resensitization as most cell death is observed upon readdition of drug following periods of drug removal. Gene expression analysis shows that a unique and reversible transcriptional state is induced in intermittently treated cells following periods of drug removal. Thus, we conclude that the beneficial effects of intermittent treatment in our model are best explained by adaptive, non-mutational changes in transcription which confer drug resensitization.
Project description:Our aim is to analyze the genome of human melanoma cell lines and short term culture from human melanoma samples in order to identify genes that confer drug resistance to clinically relevant targeted therapies. We will perform whole-exome sequencing, copy number variation analysis and methylome analysis in a collection of human melanoma cell lines and short term culture that will be then screened for drug sensitivity/resistance through a library of clinically relevant drugs and drug combinations. By the combined analysis of the genomic lesion and the drug sensitivity/resistance profile of different cell lines, we will look for genes whose mutation is associated to the sensitivity or resistance to a specific drug in different samples.
Project description:aCGH of human melanoma cell lines comparing parental (drug sensitve) vs isogenic drug resistant-derived subline Two condition experiment: two BRAF-V600E mutant cell lines (drug sensitive - parental baseline) vs two derived sublines after chronic exposure to the MEK inhibitor trametinib (drug resistant) are compared
Project description:Transcriptional co-acticvators inhibition is proving to be a powerful mean against cancer cells that shown a novel hallmarks named transcriptional addiction. This dependecy on co-activars activity lays on their presence in clusters of enhancer regulatory regions called Super-enhancers (SEs) that establish high level of expression of genes important for cancer phisiology such as oncogenes and master transcription factors of the cellular lineage of origin. Among these co-activators in SEs is the kinase CDK7 of the basal transcription factor TFIIH. Here, using a large panel of melanoma cell lines, we observed an overall dependency of melanoma cells in CDK7 activity by inhibiting its function through the drug THZ1. However, by chronically exposing melanoma cells to THZ1, they univocally become resistant, switching phenotype toward a mesenchymal-like state. By comparing the transcriptome of artificial resistant and untreated cells in culture, we observed upregulation of the transcription factor GATA6 which control indeed a small regulon that includes genes involved in multi-drug resistance (MDR).