(A) Dose dependent degradation of cIAP-1: Cells were treated with SM-164 or SM-173 for 6 hrs, followed by immunoblotting. (B-D) Caspase activation: UMSCC-1 (B), UMSCC-17B (C), and UMSCC-12 and -74B (D) cells were treated with SM-164, radiation or both, and subjected to caspase activity assay for caspases-8, -9, -2, and -3 (for UMSCC-1). Mean ± SEM (n=3) (*, p<0.05; **, p<0.01).