To counteract the influences of intracellular acidification on cancer cell function, cancer cells are equipped with well-developed acid extruders (e.g., Na+/HCO3−-cotransporters, Na+/H+-exchangers, H+-ATPases and MCTs) that remove acid equivalents and lactate from the cytosol, thus increasing extracellular acidity. This evidence concerns the gene SLC4A4 and cancer.