Project description:Aberrant activation of the mitogen-activated protein kinase (MAPK) cascade promotes oncogenic transcriptomes. Despite efforts to inhibit oncogenic kinases, such as BRAFV600E, tumor responses in patients can be heterogeneous and limited by drug resistance mechanisms. Here, we describe patient tumors that acquired COP1 or DET1 mutations after treatment with the BRAFV600E inhibi-tor vemurafenib. COP1 and DET1 constitute the substrate adaptor of the E3 ubiquitin ligase CRL4COP1/DET1, which targets transcription factors, including ETV1, ETV4, and ETV5, for pro-teasomal degradation. MAPK-MEK-ERK signaling prevents CRL4COP1/DET1 from ubiquitinating ETV1, ETV4, and ETV5, but the mechanistic details are still being elucidated. We found that pa-tient mutations in COP1 or DET1 inactivated CRL4COP1/DET1 in melanoma cells, stabilized ETV1, ETV4, and ETV5, and conferred resistance to inhibitors of the MAPK pathway. ETV5, in partic-ular, enhanced cell survival and was found to promote the expression of the pro-survival gene BCL2A1. Indeed, the deletion of pro-survival BCL2A1 re-sensitized COP1 mutant cells to vemu-rafenib treatment. These observations indicate that the post-translational regulation of ETV5 by CRL4COP1/DET1 modulates transcriptional outputs in ERK-dependent cancers, and its inactivation contributes to therapeutic resistance.
Project description:Aberrant activation of the mitogen-activated protein kinase (MAPK) cascade promotes oncogenic transcriptomes. Despite efforts to inhibit oncogenic kinases, such as BRAFV600E, tumor responses in patients can be heterogeneous and limited by drug resistance mechanisms. Here, we describe patient tumors that acquired COP1 or DET1 mutations after treatment with the BRAFV600E inhibi-tor vemurafenib. COP1 and DET1 constitute the substrate adaptor of the E3 ubiquitin ligase CRL4COP1/DET1, which targets transcription factors, including ETV1, ETV4, and ETV5, for pro-teasomal degradation. MAPK-MEK-ERK signaling prevents CRL4COP1/DET1 from ubiquitinating ETV1, ETV4, and ETV5, but the mechanistic details are still being elucidated. We found that pa-tient mutations in COP1 or DET1 inactivated CRL4COP1/DET1 in melanoma cells, stabilized ETV1, ETV4, and ETV5, and conferred resistance to inhibitors of the MAPK pathway. ETV5, in partic-ular, enhanced cell survival and was found to promote the expression of the pro-survival gene BCL2A1. Indeed, the deletion of pro-survival BCL2A1 re-sensitized COP1 mutant cells to vemu-rafenib treatment. These observations indicate that the post-translational regulation of ETV5 by CRL4COP1/DET1 modulates transcriptional outputs in ERK-dependent cancers, and its inactivation contributes to therapeutic resistance
Project description:Aberrant activation of the mitogen-activated protein kinase (MAPK) cascade promotes oncogenic transcriptomes. Despite efforts to inhibit oncogenic kinases, such as BRAFV600E, tumor responses in patients can be heterogeneous and limited by drug resistance mechanisms. Here, we describe patient tumors that acquired COP1 or DET1 mutations after treatment with the BRAFV600E inhibi-tor vemurafenib. COP1 and DET1 constitute the substrate adaptor of the E3 ubiquitin ligase CRL4COP1/DET1, which targets transcription factors, including ETV1, ETV4, and ETV5, for pro-teasomal degradation. MAPK-MEK-ERK signaling prevents CRL4COP1/DET1 from ubiquitinating ETV1, ETV4, and ETV5, but the mechanistic details are still being elucidated. We found that pa-tient mutations in COP1 or DET1 inactivated CRL4COP1/DET1 in melanoma cells, stabilized ETV1, ETV4, and ETV5, and conferred resistance to inhibitors of the MAPK pathway. ETV5, in partic-ular, enhanced cell survival and was found to promote the expression of the pro-survival gene BCL2A1. Indeed, the deletion of pro-survival BCL2A1 re-sensitized COP1 mutant cells to vemu-rafenib treatment. These observations indicate that the post-translational regulation of ETV5 by CRL4COP1/DET1 modulates transcriptional outputs in ERK-dependent cancers, and its inactivation contributes to therapeutic resistance.
Project description:Gene expression profiling was performed to access the changes in gene expression in melanomas from Pdk1-inactivated Brafv600E::Pten-/- mice. The expression profiles of the BrafV600E::Pten-/-::Pdk1-/- were compared to the BrafV600E::Pten-/-::Pdk+/+ genotypes. The analysis has identified several important signaling pathways in Pdk1-dependent melanomagenesis. Melanoma tumors from the BrafV600E::Pten-/-::Pdk1+/+ and BrafV600E::Pten-/-::Pdk1-/- genotypes were harvested and mRNA from each group was pooled to enable four biologically replicates analysis.
Project description:Gene expression profiling was performed to access the changes in gene expression in melanomas from Pdk1-inactivated Brafv600E::Pten-/- mice. The expression profiles of the BrafV600E::Pten-/-::Pdk1-/- were compared to the BrafV600E::Pten-/-::Pdk+/+ genotypes. The analysis has identified several important signaling pathways in Pdk1-dependent melanomagenesis.
Project description:Therapeutic targeting of BRAFV600Eand of MEK 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. To this end, we used whole genome microarray analysis to identify differentially expressed genes in a set of neoplastic clones, isolated from a single melanoma metastasis, and characterized by mututally exclusive expression of BRAFV600E or NRASQ61R. By this approach we identified two genes, SEMA6A and Mical-1 belonging to the semaphorin-plexin signaling pathway and higly expressed, at mRNA and protein level, in BRAF-mutant neoplastic clones. Real-time PCR, Western blot analysis and immunohistochemistry confirmed the preferential expression of SEMA-6A and Mical-1 in BRAFV600E neoplastic cells from melanoma clones, primary and metastatic cell lines and tissue sections from melanoma lesions. SEMA6A depletion, by specific RNA-interference experiments, led to cytoskeletal remodeling, loss of stress fibers, generation of actin-rich protrusion, and cell death, whereas SEMA6A overexpression, in NRASQ61R clones, promoted invasiveness. Mical-1 depletion, by siRNA, in BRAFV600E melanomas, did not alter the actin cytoskeleton organization but caused a strong NDR phosphorylation and NDR-dependent apoptosis. Overall, these results suggest that the SEMA and MICAL pathways contribute to promote survival of BRAFV600E melanomas.