Mucosal melanomas are a rare subtype of melanoma, arising in mucosal tissues, which have a very poor prognosis due to the lack of effective targeted therapies.,This study aimed to better understand the molecular landscape of these cancers and find potential new therapeutic targets.,Whole-exome sequencing was performed on mucosal melanomas from 19 patients and 135 sun-exposed cutaneous melanomas, with matched peripheral blood samples when available.,Mutational profiles were compared between mucosal subgroups and sun-exposed cutaneous melanomas.,Comparisons of molecular profiles identified 161 genes enriched in mucosal melanoma (P<0.05).,KIT and NF1 were frequently comutated (32%) in the mucosal subgroup, with a significantly higher incidence than that in cutaneous melanoma (4%).,Recurrent SF3B1 R625H/S/C mutations were identified and validated in 7 of 19 (37%) mucosal melanoma patients.,Mutations in the spliceosome pathway were found to be enriched in mucosal melanomas when compared with cutaneous melanomas.,Alternative splicing in four genes were observed in SF3B1-mutant samples compared with the wild-type samples.,This study identified potential new therapeutic targets for mucosal melanoma, including comutation of NF1 and KIT, and recurrent R625 mutations in SF3B1.,This is the first report of SF3B1 R625 mutations in vulvovaginal mucosal melanoma, with the largest whole-exome sequencing project of mucosal melanomas to date.,The results here also indicated that the mutations in SF3B1 lead to alternative splicing in multiple genes.,These findings expand our knowledge of this rare disease.
Treatment of advanced melanoma has been improved with the advent of the BRAF inhibitors.,However, a limitation to such treatment is the occurrence of resistance.,Several mechanisms have been identified to be responsible for the development of resistance, either MEK-dependent or MEK-independent.,In order to overcome resistance due to reactivation of MEK signaling, MEK inhibitors are being clinically developed with promising results.,However, also in this case resistance inevitably occurs.,It has been recently reported that ErbB3, a member of the EGFR receptor family, may be involved in the establishment of drug resistance.,Three melanoma cell lines were tested: LOX IMVI (BRAF V600E), MST-L (BRAF V600R) and WM266 (BRAF V600D).,Phosphorylation of Receptor Tyrosine Kinases (RTKs) was assessed by an RTK array.,Western blot analysis was performed on total protein extracts using anti-ErbB3, anti-AKT and anti-ERK 1/2 antibodies.,The expression of neuregulin after vemurafenib treatment was assessed by Real Time PCR and Western blotting.,The growth inhibitory effects of vemurafenib, GSK1120212b and/or anti-ErbB3 mAbs were evaluated by in vitro colony formation assays.,In the present study we demonstrate that ErbB3 is the main RTK undergoing rapidly hyperphosphorylation upon either treatment with a BRAF inhibitor or with a MEK inhibitor in a panel of melanoma cell lines harboring a variety of V600BRAF mutations and that this results in a strong activation of phospho-AKT.,Importantly, ErbB3 activation is fully abrogated by the simultaneous use of anti-ErbB3 monoclonal antibodies, which are also shown to potently synergize with BRAF inhibitors in the inactivation of both AKT and ERK pathways and in the inhibition of melanoma cell growth.,We show that upregulation of phospho-ErbB3 is due to an autocrine loop involving increased transcription and production of neuregulin by melanoma cells.,On the basis of these results, we propose that initial co-treatment with BRAF and/or MEK inhibitors and anti-ErbB3 antibodies should be pursued as a strategy to reduce the ErbB3-dependent feedback survival mechanism and enhance duration of clinical response.