SLC16A1 and cancer: One example of the many effectors of metabolic re-wiring in cancer is the monocarboxylate transporter (MCT) family (including MCT1, MCT2, MCT3 and MCT4), which are transmembrane proteins that mediate the bi-directional transport of lactate (as well as other substrates such as pyruvate, short-chain fatty acids and ketones) in and out of cells.3 MCTs allow the removal of excess lactate produced from increased glycolytic activity, which occurs even under aerobic conditions, thus preventing intracellular acidification.