QRT-PCR analysis and activation of caspase-3/7 and -8 in cilengitide-treated cells. U87ΔEGFR cells were treated with 0.5 μM cilengitide for 16 h with the colorimetric protease assay kit. For the activity of caspase-8, the relative absorbance (RA) of U87ΔEGFR cell clusters were higher than control (0.27 ± 0.01 RA vs. 0.36 ± 0.01 RA, respectively; P < 0.05) (a). Cilengitide-induced apoptosis was also detected with the CellEvent™ Caspase-3/7 Green Detection Reagent. The RFU of U87ΔEGFR cell clusters were higher than control (35.4 ± 0.78 RFU vs. 16.5 ± 0.5 RFU, respectively; P < 0.05) (b). Immunoblot analysis revealed that caspases 3 and 8 were processed in all examined cell lines following treatment with cilengitide in a concentration- (c) and time-dependent manner (d).