Suppression of calphobindin I (CPB I) production in carcinoma of uterine cervix and endometrium.

Calphobindin I (CPB I) is a member of the family of Ca(2+)-dependent phospholipid binding proteins collectively termed as annexins. CPB I (Annexin V) has recently been shown to be an endogenous inhibitor of protein kinase C, a key enzyme in the cellular signal transduction and its inhibition by CPB I is presumed to be related ultimately to carcinogenesis. We therefore examined the level of production of CPB I in uterine cancer cells. Immunohistochemical analysis, northern blot, and in situ hybridization showed that the production of CPB I was markedly suppressed at the level of transcription in both cervical and endometrial carcinoma cells when compared to their normal counterparts. Decrease in production of CPB I may lead to dysregulated activation of protein kinase C and, accordingly, may be involved in a disorder of cell differentiation, proliferation, and carcinogenesis.