Project description:RNAseq data of 2 NRAS mutant melanoma cell lines (D04, mm415), melanocytes with NRAS mutation (PHMq61), melanocytes harboring an empty vector (PHMe) and untreated melanocytes (PHM). D04 cells (samples 6-11) treated with non targeting control ASOs, or ASOs that target the lncRNA 'TRASH'
Project description:Preclinical and clinical data implicate the transcriptional co-activator YAP1 in resistance to multiple targeted therapies, including BRAF and MEK inhibitors. However, tumor subtypes driven by YAP1 activity and associated vulnerabilities are poorly defined. Here, we show particularly high YAP1 activity in the MITFlow/AXLhigh subset of melanoma cell lines and patient tumors characterized by resistance to MAPK pathway inhibition and broad receptor tyrosine kinase activity. To uncover genetic dependencies of melanoma cells with high YAP1 activity, we used a genome-wide CRISPR/Cas9 functional screen and identified SLC35B2, the 3′-phosphoadenosine-5′-phosphosulfate transporter of the Golgi apparatus, as an essential gene for YAP1-mediated drug resistance. SLC35B2 expression correlates with tumor progression, and its loss decreases heparan sulfate expression, reduces receptor tyrosine kinase activity, and sensitizes resistant melanoma cells to BRAF inhibition in vitro and in vivo. Thus, SLC35B2 is a target in YAP1-driven BRAF mutant melanoma for overcoming drug resistance to MAPK pathway inhibitors.
Project description:Metastatic melanoma is either intrinsically resistant or rapidly acquires resistance to targeted therapy treatments, such as MAPK inhibitors. A leading cause of resistance to targeted therapy is a dynamic transition of melanoma cells from a proliferative to a highly invasive state, a phenomenon called phenotype switching. Mechanisms regulating phenotype switching represent potential targets for improving treatment of melanoma patients. Using a drug screen targeting chromatin regulators in patient-derived 3D MAPK inhibitor-resistant melanoma cell cultures, we discovered that PARP inhibitors restore sensitivity to MAPK inhibitors, independent of DNA damage repair pathways. Integrated transcriptomic, proteomic, and epigenomic analyses demonstrated that PARP inhibitors induce lysosomal autophagic cell death, accompanied by enhanced mitochondrial lipid metabolism that ultimately increases antigen presentation and sensitivity to T-cell cytotoxicity. Moreover, transcriptomic and epigenetic rearrangements induced by PARP inhibition reversed EMT-like phenotype switching, which redirected melanoma cells toward a proliferative and MAPK inhibitor-sensitive state. The combination of PARP and MAPK inhibitors synergistically induced cancer cell death both in vitro and in vivo in patient-derived xenograft models. Therefore, this study provides a scientific rationale for treating melanoma patients with PARP inhibitors in combination with MAPK inhibitors to abrogate acquired therapy resistance.
Project description:The tumor suppressive miR-29 family of microRNAs is encoded by two clusters, miR-29b1~a and miR-29b2~c, and is regulated by several oncogenic and tumor suppressive stimuli. Here we investigated whether oncogenic MAPK hyperactivation regulates miR-29 abundance and how this signaling axis impacts melanoma development. Using mouse embryonic fibroblasts and human melanocytes, we found that oncogenic MAPK signaling stimulates p53-independent and p53-dependent transcription of pri-miR-29b1~a and pri-miR-29b2~c, respectively. Expression analyses revealed that while pri-miR-29a~b1 remains elevated, pri-miR-29b2~c levels decrease during melanoma progression. Using a rapid mouse modeling platform, we showed that inactivation of miR-29 in vivo accelerates the development of frank melanomas and decreases overall survival. We identified MAFG as a relevant miR-29 target that has oncogenic potential in melanocytes and is required for growth of melanoma cells. Our findings suggest that MAPK-driven miR-29 induction constitutes a tumor suppressive barrier by targeting MAFG, which is overcome by attenuation of miR-29b2~c expression.
Project description:Current therapeutic management of advanced melanoma patients largely depends on their BRAF mutation status. However, the vast heterogeneity of the tumors hampers the success of therapies targeting the MAPK/ERK pathway alone. Dissecting this heterogeneity will contribute to identifying key players in the oncogenic progression to tailor more effective therapies. We performed a comprehensive molecular and phenotypic characterization of a panel of patient-derived BRAFV600E-positive melanoma cell lines. Transcriptional profiling was used to identify groups of coregulated genes whose expression relates to an increased migratory potential and a higher resistance. A decrease in sensitivity to MAPK/ERK pathway inhibition with vemurafenib or trametinib corresponded with an increasing quiescence and migratory properties of the cells. This was accompanied by the loss of transcriptional signatures of melanocytic differentiation, and the gain of stem cell features that conferred highly-resistant/mesenchymal-like cells with increased xenobiotic efflux capacity. Nevertheless, targeting of the implicated ABC transporters did not improve the response to vemurafenib, indicating that incomplete BRAF inhibition due to reduced drug uptake is not a main driver of resistance. Rather, indifference to MAPK/ERK pathway inhibition arose from the activation of compensatory signaling cascades. The PI3K/AKT pathway in particular showed a higher activity in mesenchymal-like cells, conferring a lower dependency on MAPK/ERK signaling and supporting stem-like properties that could be reverted by dual PI3K/mTOR inhibition with dactolisib. In case of MAPK/ERK independency, therapeutic focus may be shifted to the PI3K/AKT pathway to overcome late-stage resistance in melanoma tumors that have acquired a mesenchymal phenotype.
Project description:Long non-coding RNAs (lncRNAs) comprise a diverse class of gene expression regulators with emerging roles in many biological processes including cancer. Here we show that the expression of the lncRNA Hedgehog Interacting Protein Antisense 1 (HHIP-AS1) is a hallmark feature of human SHH-driven tumors. Importantly, loss of HHIP-AS1 leads to reduced tumor growth in SHH-driven tumors in vitro and in vivo. Our results demonstrate the power of cross-entity transcriptome-wide comparisons to identify novel epigenetic–regulatory lncRNA circuitries underlying human cancers.
Project description:Metastatic melanoma is either intrinsically resistant or rapidly acquires resistance to targeted drugs such as MAPK inhibitors (MAPKi). Here, using a drug screen targeting chromatin regulators in patient-derived 3D melanoma cell cultures, we discovered that PARP inhibitors are capable of restoring MAPKi sensitivity. This synergy was found to be independent of DNA damage repair pathways and was effective both in vitro and in vivo in patients-derived xenografts. Strikingly, through integrated transcriptomic, proteomic and epigenomic analysis, we discovered that PARPi induces lysosomal autophagy which was accompanied by enhanced mitochondrial lipid metabolism that, ultimately, increased antigen presentation and sensitivity to T-cell cytotoxicity. Moreover, we also found that PARP inhibitors regulated EMT-like phenotype switching by dampening the mesenchymal phenotype via transcriptomic and epigenetic rearrangements. This, in turn, redirected melanoma cells towards a proliferative and, thus, MAPKi-sensitive state. Our study provides a scientific rational for treating patients with PARPi in combination with MAPKi to annihilate acquired therapy resistance.
Project description:Therapeutic targeting of BRAFV600E has shown a significant impact on progression-free and overall survival in advanced melanoma, but only a fraction of patients benefit from these treatments, suggesting that additional signaling pathways involved in melanoma growth/survival need to be identified. In fact MAPK and PI3K/mTOR signaling pathways are constituively activated in most cancers, including melanoma, to sustain the melanoma growth/survival. A large panel of melanoma were characterized for resistance/susceptibility to different inhibitors targeting MAPK and PI3K/mTOR signaling pathways and the synergistic effect of combinatorial treatments affecting both pathways. These effects were evaluated in terms of cell viability (MTT), apoptosis (Annexin V-PI), caspase 3/7 activity and subG1 cell fraction, highlighting a hierarchy in the combination effects. Further, a smaller panel of melanoma cell lines, were treated with inhibitors singularly and in combination to test the effects on the expression of principal proteins involved in these two pathways. Gene expression profile was performed to analyse the gene modulation induced by inhibitors to identify new strategies to fight melanoma resistance.
Project description:Extracellular signal regulated kinases, ERK1 and ERK2 are often considered as redundant due to their high homology, large number of overlapping substrates, and ability to substitute for each other in genetically engineered mouse models. We have investigated the individual contribution of ERK1 and ERK2 to the survival of human melanoma cell lines driven by oncogenic BRAF. ERK2, but not ERK1 activity, was crucial to drive survival and maintain transcriptional output of the MAPK pathway. Furthermore, we found that ERK2 DEF-domain interactions were crucial for transcriptional regulation and survival in some cells, but not in others, whereas ERK2-substrate interactions at the D-docking motif were largely dispensable. We used microarrays to examine the global impact of gene expression by imhibiting different nodes of MAPK pathway.
Project description:One third of BRAF-mutant metastatic melanoma patients treated with combined BRAF and MEK inhibition progress within six months. Treatment options for these patients remain limited. Here we analyse twenty BRAFV600 mutant melanoma metastases derived from 10 patients treated with the combination of debrafenib and trametinib for resistance mechanisms and genetic correlates of response. Resistance mechanisms are identified in 9/11 progressing tumors and MAPK reactivation occurred in 9/10 tumors, commonly via BRAF amplification and mutations activating NRAS and MEK2. Our data confirming that MEK2C125S, but not the synonymous MEK1C121S protein confers resistance to combination therapy, highlight the functional differences between these kinases and the preponderance of MEK2 mutations in combination therapy-resistant melanomas. Exome sequencing did not identify additional progression-specific resistance candidates. Nevertheless, most melanomas carried additional oncogenic mutations at baseline (e.g. RCA1 and AKT3) that activate the MAPK and P13K pathways and are thus predicted to diminish response to MAPK inhibitors. Total RNA obtained from fresh frozen melanoma tumors treated with a combination of dabrafenib and trametinib