SLC16A1 and cancer: The MCT1 and MCT4 isoforms are at the center of the mutually beneficial lactate transport between the hypoxic, i.e., glycolytic, and the oxidative, i.e., lactate-consuming, cancer cells (Warburg and reverse-Warburg effects) [34], as well as in the lactate shuttle between glycolytic astrocytes and oxidative neurons in the brain [35].