The mitogen-activated protein kinase pathway plays a critical role in regulating immunological properties of BRAF mutant cutaneous melanoma cells.

The advent of drugs targeting the mitogen-activated protein kinase (MAPK) pathway has markedly changed the treatment of advanced-stage melanoma harboring BRAF mutations. However, drug resistance, through mechanisms not well elucidated, often occurs. A better understanding of how melanoma-derived immunologically active molecules change in response to MAPK inhibition of BRAF mutated (BRAF(V600E)) and BRAF wild type (BRAF(WT)) melanomas could help identify promising treatment combinations of small molecule inhibitors and immunotherapy. To this aim, we treated 13 BRAF(WT) and 13 BRAF(V600E) mutated human melanoma cell lines with either a specific BRAF(V600E) inhibitor or an MEK1/2 inhibitor and analyzed changes in the secretion of 42 selected cytokines, chemokines, and growth factors. We also measured changes in the expression levels of immunologically relevant melanoma cell surface markers. The BRAF(WT) melanomas showed minimal changes in response to the inhibitors, whereas the BRAF(V600E) cell lines showed, on average, a significant decrease in IFN alpha 2, interleukin-7, Fractalkine, GCSF, GRO, TGF alpha 2, interleukin-8, and VEGF, as well as a reduction in pERK and pMEK protein levels, upon MAPK pathway blockade. BRAF inhibition in BRAF(V600E) cell lines also resulted in significant changes in the expression of several surface markers including upregulation of beta(2)-microglobulin as well as a decrease in MIC A/B and TRAIL-R2. These results indicate that MAPK pathway inhibition leads to changes in the immunological properties of mutant BRAF(V600E) melanoma cells and lends support for future studies aimed at designing effective treatment strategies that combine BRAF and MEK inhibition with immunotherapy. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.