Effects of the new selective protein kinase C inhibitor 4'-N-benzoyl staurosporine on cell cycle distribution and growth inhibition in human small cell lung cancer cells.

CGP 41251 (4'-N-benzoyl staurosporine, CAS 120685-11-2) exerts increased selectivity for Ca(2+)- and phospholipid-dependent protein kinase C inhibition. In this study, the effects of CGP 41251 on cell cycle distribution and growth inhibition were examined in SBC3 human small cell lung cancer (SCLC) cell line. CGP 41251 caused the inhibition of cell proliferation and at 1.0 mumol/l showed almost complete effect. In early S phase synchronized SBC3 cells, CGP 41251 at 1.0 mumol/l did not inhibit an initial progression from early S to G2 phase, but it blocked a process from G2/M to G1 phase completely. After removal of nocodazole block, CGP 41251 at 1.0 mumol/l caused DNA re-replication and induction of polyploidy. In nude mice xenograft, CGP 41251 at a dose of 200 mg/kg showed statistically significant inhibition against this tumor with a T/C value of 21.4%. Histopathologically, expansion of central necrosis was observed by the administration of CGP 41251. These results in SBC3 cells indicated that CGP 41251 showed antitumor activity through the inhibition of cell cycle progression from G2/M to G1 phase, and through induction of cells with higher DNA content.