One such example is the symbiosis between well and poorly-oxygenated cancer cell populations (Figure 1): at the hypoxic, nutrient-poor/normoxic, nutrient-rich interface, lactate is released by glycolytic cancer cells through MCT4, and taken up by oxidative cancer cells through MCT1, where it fuels oxidative phosphorylation, thus sparing glucose for glycolytic cancer cells (84). This evidence concerns the gene SLC16A1 and cancer.