PROS1 and neoplasm: Furthermore, HIF-1α also inhibits the apoptosis of tumor cells by down-regulating the levels of the anti-apoptotic proteins Bcl2 (e.g., IL-6/STAT3/Bcl2 pathway),54,55 an inhibitor of apoptosis protein-2 (IAP-2)55 and lowering the levels of cleaved caspase-3 and the pro-apoptotic proteins Bcl2 associated X protein (BAX).56