Abstract
Staurosporine is a microbial anti-fungal alkaloid having potent inhibitory activity on protein kinase C and is a non 12-O-tetradecanoylphorbol-13-acetate-type tumor promoter in two-stage carcinogenesis experiments in mouse skin. Effects of staurosporine and its structurally related compounds K-252a, KT5720 and KT5822 on prostaglandin E2 production, release of arachidonic acid from membrane phospholipids, and uptake of [35S]methionine into intracellular proteins were examined in rat peritoneal macrophages. Among the four compounds, only staurosporine stimulated the production of prostaglandin E2 and release of arachidonic acid at concentrations of 1 ng/ml and 10 ng/ml. The uptake of [35S]methionine into cellular proteins, estimated to be 120 kDa and 125 kDa molecular mass, was also stimulated by staurosporine treatment, and the uptake was increased in parallel with the increase in prostaglandin E2 production. At higher concentrations (100 ng/ml and 1000 ng/ml), staurosporine inhibited prostaglandin E2 production and did not induce the specific protein synthesis. Other compounds neither stimulated prostaglandin E2 production nor induced specific protein synthesis. K-252a inhibited prostaglandin E2 production at concentrations above 10 ng/ml. These results suggest that the staurosporine-induced proteins might participate in the tumor promotion or at least in the staurosporine-induced stimulation of prostaglandin E2 production.