Z-VAD is a competitive, irreversible, and broad-spectrum caspase inhibitor that inhibits all caspases except caspase-2, against which it is less effective. This compound reduces radiation-induced apoptosis and can induce autophagy and necrosis in radiation-treated xenografts of MDA-MB-231 and H460 in mice. When combined with radiation, Z-VAD significantly delays tumor growth and exhibits substantial anti-angiogenic effects in cancer xenografts.