Fig. 7. Cooperative cytotoxicity of IR in combination with the cPKC-specific inhibitor PKC-412. A, proliferation was assessed 48 h after treatment with PKC-412 (200 nM) and IR (2 Gy) or both in combination. B, cytosolic extracts from untreated cells (CTL) or from cells treated for 18 h with PKC-412 (200 nM), IR (5 Gy), or both in combination (PKC-412+IR) were probed using the monoclonal anti-cytochrome c antibody. C, caspase-9 activity was determined 18 h after treatment using the caspase-9-specific peptide substrates (Ac-LEHD-pNA) in cellular extracts derived from control cells (CTL) or from cells treated with PKC-412 (200 nM), IR (5 Gy), or both in combination.