Project description:Rapid resistance to BRAF inhibitors in BRAFV600-mutant metastatic melanoma has produced an urgent need for new treatment options. BRAF inhibitor resistance commonly involves reactivation of mitogen-activated protein kinase (MAPK) signaling and yet inhibition of downstream kinases has not circumvented resistance, partly because MAPK is regulated via a complex network of feedback mechanisms that influence pathway rebound. To examine the transcriptome responses of melanoma cells to MAPK inhibition, a panel of 11 BRAFV600-mutant melanoma cell lines were treated with control (DMSO), 100nM dabrafenib alone (i.e BRAF inhibitor monotherapy) or 100nM dabrafenib + 10nM trametinib (i.e combination BRAF + MEK inhibition) for 24h.
Project description:BRAF, one of three RAF serine/threonine kinases (ARAF, BRAF and CRAF), plays a major role in the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signaling pathway, which mediates cellular responses to growth signals. Recently a high frequency (~60%-70%) of activating BRAF mutations (predominantly V600E) has been reported in malignant melanoma. In order to identify the downstream effects of BRAF signaling on melanoma cell growth and gene expression, cDNA microarray analysis was carried out following BRAF siRNA or MEK1/2 inhibitor (U0126) treatment. Keywords: time series, siRNA time series, siRNA, drug treatment
Project description:BRAF, one of three RAF serine/threonine kinases (ARAF, BRAF and CRAF), plays a major role in the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signaling pathway, which mediates cellular responses to growth signals. Recently a high frequency (~60%-70%) of activating BRAF mutations (predominantly V600E) has been reported in malignant melanoma. In order to identify the downstream effects of BRAF signaling on melanoma cell growth and gene expression, cDNA microarray analysis was carried out following BRAF siRNA or MEK1/2 inhibitor (U0126) treatment. Keywords: time series, siRNA
Project description:Combining PD-L1 blockade with inhibition of oncogenic mitogen-activated protein kinase (MAPK) signaling may result in long-lasting responses in patients with advanced melanoma. This phase 1, open-label, dose-escalation and -expansion study (NCT02027961) investigated safety, tolerability and preliminary efficacy of durvalumab (anti–PD-L1) combined with dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor) for patients with BRAF-mutated melanoma (cohort A, n=26), or durvalumab and trametinib given concomitantly (cohort B, n=20) or sequentially (cohort C, n=22) for patients with BRAF-wild type melanoma. Adverse events and treatment discontinuation rates were more common than previously reported for these agents given as monotherapy. Objective responses were observed in 69.2% (cohort A), 20.0% (cohort B) and 31.8% (cohort C) of patients, with evidence of improved tumor immune infiltration and durable responses in a subset of patients with available biopsy samples. In conclusion, combined MAPK inhibition and anti–PD-L1 therapy may provide treatment options for patients with advanced melanoma.
Project description:Fifty percent of cutaneous melanomas are driven by activated BRAFV600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAFV600E mutant melanoma cell lines of varying levels of resistance to MAPK pathway inhibition we identified the combination PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ERBB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and RTK mutational status. Layered over base-line resistance was substantial upregulation of many ERBB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ERBB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes. 12 BRAF mutant melanomas and 4 melanomas with WT BRAF were exposed plx4720 treatment to evaluate their responses after 8 hours of treatment. 5 of the 12 BRAF mutant melanomas responses were also evaluated in response to the treatment of lapatinib alone, masitinib alone, the combination of lapatinib with plx4720, or the combination of masitinib with plx4720. All samples were run in at least triplicate.
Project description:BRAF V600 mutation influences cellular signaling pathways for melanoma development. Here, we show that mutated BRAF plays an essential role in the adaptive stress response following activation of general control non-derepressible 2 (GCN2) kinase. In parallel with GCN2, BRAF ensures ATF4 induction by utilizing mTOR and eIF4B as downstream regulators during nutrient stress and BRAF-targeted, therapeutic stress. Upon pharmacological BRAF inhibition, this signaling pathway exhibits temporal resistance, compared with the MEK-ERK pathway, thereby enabling transient induction of ATF4 under GCN2 activation. Notably, the prevention of GCN2 activation, using a chemical inhibitor that we identified, produces synergistic cell killing with BRAF inhibition. Thus, oncogenic BRAF can collaborate with the GCN2–ATF4 pathway, promoting stress adaptation for cell survival.
Project description:BRAF V600 mutation influences cellular signaling pathways for melanoma development. Here, we show that mutated BRAF plays an essential role in the adaptive stress response following activation of general control non-derepressible 2 (GCN2) kinase. In parallel with GCN2, BRAF ensures ATF4 induction by utilizing mTOR and eIF4B as downstream regulators during nutrient stress and BRAF-targeted, therapeutic stress. Upon pharmacological BRAF inhibition, this signaling pathway exhibits temporal resistance, compared with the MEK-ERK pathway, thereby enabling transient induction of ATF4 under GCN2 activation. Notably, the prevention of GCN2 activation, using a chemical inhibitor that we identified, produces synergistic cell killing with BRAF inhibition. Thus, oncogenic BRAF can collaborate with the GCN2–ATF4 pathway, promoting stress adaptation for cell survival.
Project description:The implementations of targeted molecular therapies and immunotherapy in melanoma vastly improved the therapeutic outcome in patients with limited efficacy of surgical intervention. Nevertheless, a large fraction of melanoma patients still remains refractory or acquires resistance to these new forms of treatment, illustrating a need for improvement. Here we report that the clinically relevant combination of MAP kinase inhibitors Dabrafenib and Trametinib synergizes with RIG-I agonist-induced immunotherapy to kill BRAF-mutated human and mouse melanoma cells. Kinase inhibition did not compromise the agonist-induced innate immune response of the RIG-I pathway in host immune cells. In a melanoma transplantation mouse model, the triple therapy outperformed the individual therapies. Our study suggests that targeted activation of RIG-I with its synthetic ligand 3pRNA could vastly improve tumor control in a substantial fraction of melanoma patients receiving MAP kinase inhibitors.
Project description:The implementations of targeted molecular therapies and immunotherapy in melanoma vastly improved the therapeutic outcome in patients with limited efficacy of surgical intervention. Nevertheless, a large fraction of melanoma patients still remains refractory or acquires resistance to these new forms of treatment, illustrating a need for improvement. Here we report that the clinically relevant combination of MAP kinase inhibitors Dabrafenib and Trametinib synergizes with RIG-I agonist-induced immunotherapy to kill BRAF-mutated human and mouse melanoma cells. Kinase inhibition did not compromise the agonist-induced innate immune response of the RIG-I pathway in host immune cells. In a melanoma transplantation mouse model, the triple therapy outperformed the individual therapies. Our study suggests that targeted activation of RIG-I with its synthetic ligand 3pRNA could vastly improve tumor control in a substantial fraction of melanoma patients receiving MAP kinase inhibitors.
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.