SLC16A1 and neoplasm: This finding is underpinned by cell-specific expression of the monocarboxylate transporters 1 and 4 (MCT1/4), where MCT1 and MCT4 are expressed mostly on tumour and stromal cells respectively and mediate lactate/pyruvate influx (MCT1) and lactate efflux (MCT4)28,31,32.