FOXP3 and hepatocellular carcinoma: Although Mct1, but not Mct3, was predominantly expressed in the Hepa1-6 KO cells (Figure S14B), KD of Mct1 failed to affect the extracellular lactate concentration and the Foxp-3+ Treg cell proportion under co-culture condition, suggesting the essential roles of MCT4 in lactate transporting within HCC cells (Figures S14C–S14E).