SLC16A1 and neoplasm: Monocarboxylate transporters 1/2 (MCT1/2) transport exogenous lactate from the tumor microenvironment into cells to modulate cellular function, while lactate dehydrogenase A (LDHA) enables endogenous lactate production by tumor cells.[22, 39] To elucidate the source of lactate regulating GSC stemness and proliferation, we used the MCT1/2 inhibitor AR‐C155858 and the LDHA inhibitor (R)‐GNE‐140.