Antitumor activity of the new selective protein kinase C inhibitor 4'-N-benzoyl staurosporine on murine and human tumor models

CGP 41251 (4'-N-benzoyl staurosporine, CAS 120685-11-2) has been shown to exert increased selectivity for the inhibition of protein kinase C (PKC) activity. In the present study the effect of CGP 41251 formulated in gelucire as an antitumor agent was studied in various types of murine and human tumor models. When administered at a dose of 75 mg/kg 3 times daily for 9 days, CGP 41251 prolonged the life span of the mice bearing B16 melanoma (ILS = 36%). CGP 41251, administered orally at doses of 25-225 mg/kg once daily for 9 days, however, did not show distinct efficacy in four kinds of murine tumor models (B16 melanoma, colon 26, colon 38 and M5076). In s.c.inoculated human tumor xenograft models, CGP 41251, administered orally at a dose of 200 mg/kg once daily for 4 weeks showed a broad antitumor spectrum. CGP 41251 inhibited the growth of gastric cancer (H-55), colorectal cancer (H-26), breast cancer (H-31) and lung cancer (H-74 and LC-376) with inhibition rates of 58-80%. In a histopathologic study, increase in central necrosis and condensed nuclei and vacuolar degeneration were observed, but there was no structural destruction by the treatment of CGP 41251. In addition, CGP 41251 decreased the number of PCNA (proliferating cell nuclear antigen) immunoreactive cells in human tumor cells H-55, H-26 and H-74. These results indicate that CGP 41251 shows a broad antitumor spectrum against human tumors, and it is suggested that CGP 41251 is a promising oral antitumor agent which has a novel mechanism of action.