Background
After BRAF, NRAS is the most commonly mutated oncogene in melanoma. However therapies targeting NRAS remain elusive. In BRAF-mutant melanoma cells, BRAF inhibitors suppress glycolysis, and induce mitochondrial metabolism, through expression of MITF and PGC1a. We hypothesised that addition of a mitochondrial inhibitor (PENAO) would enhance the efficacy of the MEK inhibitor trametinib in NRAS-mutant melanoma models.
Materials and Methods
The responses of NRAS-mutant melanoma cells, to MAPK pathway and mitochondrial inhibition, were investigated by assessing: cell proliferation; lactate production; glucose uptake; gene expression profiles of metabolic regulators and extracellular flux analysis. An IPC298 NRAS-mutant melanoma xenograft model was used to study the inhibitors in vivo.
Results
In NRAS-mutant melanoma cells, MEK and ERK inhibition resulted in reduced glucose uptake and lactate production; and increased MITF and PGC1a expression. In NRAS-mutant melanoma cells, the addition of PENAO to trametinib enhanced the effect on cellular proliferation. Extracellular flux analysis showed a reduction in extracellular acidification rate following trametinib; reduced oxygen consumption rate after PENAO and a reduction in both parameters with the combination. In vivo, the addition of PENAO was well tolerated but did not enhance the anti-proliferative effect of trametinib.
Conclusion
In NRAS-mutant melanoma cells, MAPK pathway inhibition results in metabolic reprogramming similar to changes observed in BRAF-mutant melanoma cells. The addition of PENAO to trametinib results in altered metabolic reprogramming and enhances anti-proliferative activity in vitro. Further studies to investigate differences between the in vitro and in vivo models are currently underway.