Antennapedia (Antp)-SMCC-cytochrome c conjugate (5 μg/mL) activates caspase-dependent apoptosis of HeLa cells. The Antp-SMCC-cytochrome c conjugate reduces the clonogenic survival of Hela cells, and inhibits clonogenic survival. ANTP-SmacN7 fusion protein can transduce and accumulate in cells, while SmacN7 alone cannot. ANTP-SmacN7 fusion proteins have a radiation-sensitising effect on EC109 cells. ANTP-SmacN7 combined with radiation does not promote further increases in caspase-3 protein expression, it increases the levels of cleaved caspase-3.