GLS and cancer: By sharp contrast, inhibition of glutaminolysis by CB-839, a selective inhibitor of glutaminase-1 (GLS1), dramatically suppressed the survival of A549 and H1299 cells under Glc-/Gln+ condition (Fig. 2a, b and Supplementary Fig. S2b, c), indicating that cancer cells preferentially utilize glutamine as an energy source for survival upon glucose deprivation.