Overexpression of protein kinase C β1 in the SW480 colon cancer cell line growth suppression

Using a retroviral vector system we have established derivatives of the E8 subclone of the human colon cancer cell line SW480 that stably overproduce a full-length rat cDNA encoding the β1 isoform of protein kinase C (PKCβ1). In contrast to vectrol control cells, when treated with the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA), the overexpressing cell lines displayed a striking increase in doubling time, and a decrease in saturation density. Western blot analysis indicated that treatment with TPA was also associated with translocation and partial down-regulation of the exogenous PKCβ1 in the over-expressor cell lines. These results extend previous evidence that PKCβ1 can inhibit the growth of the HT29 human colon cancer cell line. The HT29 cells have a normal c-k-ras oncogene but the SW480 cells used in the present study have an activating mutation in this oncogene. Thus PKCβ1 can function as a suppressor in both types of colon cancer cells