A fatty acid oxidation-dependent metabolic shift regulates the adaptation of BRAF-mutated melanoma to MAPK inhibitors

Purpose: Treatment of BRAFV600E-mutant melanomas with mitogen-activated protein kinase inhibitors (MAPKi) results in significant tumor regression, but acquired resistance is pervasive. To understand non-mutational mechanisms underlying the adaptation to MAPKi and to identify novel vulnerabilities of melanomas treated with MAPKi, we focused on the initial response phase during treatment with MAPKi. Experimental Design: By screening proteins expressed on the cell surface of melanoma cells, we identified the fatty acid transporter CD36 as the most consistently upregulated protein upon short-term treatment with MAPKi. We further investigated the effects of MAPKi on fatty acid metabolism using in vitro and in vivo models and analyzing patients9 pre- and on-treatment tumor specimens. Results: Melanoma cells treated with MAPKi displayed increased levels of CD36 and of peroxisome proliferator-activated receptor α (PPARα)-mediated and carnitine palmitoyltransferase 1A (CPT1A)-dependent fatty acid oxidation (FAO). While CD36 is a useful marker of melanoma cells during adaptation and drug-tolerant phases, the upregulation of CD36 is not functionally involved in FAO changes that characterize MAPKi-treated cells. Increased FAO is required for BRAFV600E-mutant melanoma cells to survive under the MAPKi-induced metabolic stress prior to acquiring drug resistance. The upfront and concomitant inhibition of FAO, glycolysis and MAPK synergistically inhibits tumor cell growth in vitro and in vivo. Conclusions: Thus, we identified a clinically relevant therapeutic approach that has the potential to improve initial responses and to delay acquired drug resistance of BRAFV600E-mutant melanoma.