In BC and GBM, a metabolic symbiosis also exists between tumor subpopulations in the oxygenated and hypoxic regions of the tumor, wherein hypoxic cells metabolise glucose to secrete lactate (through lactate transporter MCT4) which in turn is internalized by the oxygenated cells via MCT1 to produce energy through OXPHOS (254–259). This evidence concerns the gene SLC16A1 and neoplasm.