Once melanomas have progressed with acquired resistance to mitogen-activated protein kinase (MAPK)-targeted therapy, mutational heterogeneity presents a major challenge.,We therefore examined the therapy phase before acquired resistance had developed and discovered the melanoma survival oncogene MITF as a driver of an early non-mutational and reversible drug-tolerance state, which is induced by PAX3-mediated upregulation of MITF.,A drug-repositioning screen identified the HIV1-protease inhibitor nelfinavir as potent suppressor of PAX3 and MITF expression.,Nelfinavir profoundly sensitizes BRAF and NRAS mutant melanoma cells to MAPK-pathway inhibitors.,Moreover, nelfinavir is effective in BRAF and NRAS mutant melanoma cells isolated from patients progressed on MAPK inhibitor (MAPKi) therapy and in BRAF/NRAS/PTEN mutant tumors.,We demonstrate that inhibiting a driver of MAPKi-induced drug tolerance could improve current approaches of targeted melanoma therapy.,•MITF is a driver of a reversible non-mutational drug-tolerance phase in melanoma•Drug repositioning identifies nelfinavir mesylate as a suppressor of MITF expression•Nelfinavir sensitizes BRAF and NRAS mutant melanoma to MAPK inhibitor treatment•A nelfinavir combination therapy overcomes NRAS-driven acquired resistance,MITF is a driver of a reversible non-mutational drug-tolerance phase in melanoma,Drug repositioning identifies nelfinavir mesylate as a suppressor of MITF expression,Nelfinavir sensitizes BRAF and NRAS mutant melanoma to MAPK inhibitor treatment,A nelfinavir combination therapy overcomes NRAS-driven acquired resistance,Smith et al. discover PAX3-mediated overexpression of MITF as a reversible resistance mechanism to MAPK-pathway inhibition in BRAF mutant melanomas and identify nelfinavir, which inhibits this mechanism and sensitizes not only BRAF mutant but also BRAF and NRAS mutant melanoma cells to MAPK-pathway inhibitors.
The management of melanoma has evolved due to improved understanding of its molecular drivers.,To augment the current understanding of the prevalence, patterns, and associations of mutations in this disease, the results of clinical testing of 699 advanced melanoma patients using a pan-cancer next generation sequencing (NGS) panel of hotspot regions in 46 genes were reviewed.,Mutations were identified in 43 of the 46 genes on the panel.,The most common mutations were BRAFV600 (36%), NRAS (21%), TP53 (16%), BRAFNon-V600 (6%), and KIT (4%).,Approximately one-third of melanomas had >1 mutation detected, and the number of mutations per tumor was associated with melanoma subtype.,Concurrent TP53 mutations were the most frequent event in tumors with BRAFV600 and NRAS mutations.,Melanomas with BRAFNon-V600 mutations frequently harbored concurrent NRAS mutations (18%), which were rare in tumors with BRAFV600 mutations (1.6%).,The prevalence of BRAFV600 and KIT mutations were significantly associated with melanoma subtypes, and BRAFV600 and TP53 mutations were significantly associated with cutaneous primary tumor location.,Multiple potential therapeutic targets were identified in metastatic unknown primary and cutaneous melanomas that lacked BRAFV600 and NRAS mutations.,These results enrich our understanding of the patterns and clinical associations of oncogenic mutations in melanoma.