GLS and melanoma: To test whether G6PD mutant melanoma cells were sensitive to glutaminase inhibition, we cultured G6PD mutant and control melanoma cells in vehicle (DMSO) or CB-839, a glutaminase inhibitor (40); 1 nM CB-839 did not significantly affect the growth of A375 control melanoma cells and 10 nM CB-839 only modestly reduced their growth (Fig. 5A).