Survivin is a 16 kDa anti-apoptotic protein highly expressed during fetal development and cancer cell malignancy. Survivin binds and inhibits caspase-3, controlling the checkpoint in the G2/M-phase of the cell cycle by inhibiting apoptosis and promoting cell division. This regulatory process requires the phosphorylation of survivin at Thr34 by p34 cdc2 kinase. Gene targeting using a Thr34 phosphorylation-defective survivin mutant, as well as antisense survivin, have been shown to inhibit tumor growth.