[The inhibitory effect of a third generation retinoid, R8605, on protein kinase C activity in vitro]

R8605 is a newly synthesized compound of the third generation retinoids produced by the Institute of Materia Medica. It exhibited in vitro inhibitory effects on the diolein and TPA (12-O-tetradecanoylphorbol-13-acetate) induced activation of Protein Kinase C (PKC) from rat brain and also showed inhibitory effects on the calcium/phospholipid-independent phosphorylation of protamine by PKC. The IC50 values were 65, 70, 100/mumol/L respectively. It is suggested that the inhibition of PKC activity by R8605 is related to the inhibition of tumor promotion.