Carnosine helps cancer cells to evade immune surveillance by regulating intracellular pH

Cancer cells often rely on glycolysis for energy metabolism. Increased glycolysis leads to the increased production of lactate and H+ ions, which should hypothetically lower intracellular pH. However, we find that tumor cells combat intracellular over-acidification by synthesizing carnosine, especially under hypoxic conditions, which allows them to control lysosome-dependent galectin-9 expression and evade T cell-mediated immune surveillance.