| Abstract: |
Melanoma patients with BRAFV 600E-mutant tumors display striking responses to BRAF inhibitors (BRAFi); however, almost all invariably relapse with drug-resistant disease. Here, we report that microRNA-125a (miR-125a) expression is upregulated in human melanoma cells and patient tissues upon acquisition of BRAFi resistance. We show that miR-125a induction confers resistance to BRAFV 600E melanoma cells to BRAFi by directly suppressing pro-apoptotic components of the intrinsic apoptosis pathway, including BAK1 and MLK3. Apoptotic suppression and prolonged survival favor reactivation of the MAPK and AKT pathways by drug-resistant melanoma cells. We demonstrate that miR-125a inhibition suppresses the emergence of resistance to BRAFi and, in a subset of resistant melanoma cell lines, leads to partial drug resensitization. Finally, we show that miR-125a upregulation is mediated by TGFβ signaling. In conclusion, the identification of this novel role for miR-125a in BRAFi resistance exposes clinically relevant mechanisms of melanoma cell survival that can be exploited therapeutically. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd |
