Metabolic symbiosis between cancer cells and CAFs requires that the cells express a subtype of monocarboxylate transporter 1 (MCT1), which contributes to the uptake of lactate provided by CAFs expressing MCT4.30 Cancer shows a high metabolic heterogeneity; MCT4-expressing tumor cells produce and secrete lactate from glycolysis, while MCT1-expressing cancer cells import lactate via MCT1 and perform oxidative phosphorylation.31 Cancer cells synthesize pyruvate from lactate, providing the tricarboxylic acid cycle with intermediate metabolites. Here, SLC16A1 is linked to cancer.