INVOLVEMENT OF THE ALPHA-ISOENZYME OF PROTEIN-KINASE-C IN THE GROWTH-INHIBITION INDUCED BY PHORBOL ESTERS IN MH1C1 HEPATOMA-CELLS

MH1C1 rat hepatoma cells express the alpha isoenzyme as the only phorb ol-ester sensitive isoform of protein kinase C (PKC). In this cell lin e, phorbol 12-myristate 13-acetate (PMA) induced a marked, dose-depend ent growth inhibition. The administration of the PKC inhibitor stauros porine was able to mimic the effect of the phorbol ester on cell growt h in a dose-dependent fashion, whereas the PKC activator arachidonic a cid stimulated cell proliferation. Exposure of cells to an antisense o ligonucleotide specific for alpha PKC caused a significant impairment of cell growth. These data suggest that the alpha PKC activity is requ ired for proliferation of MH1C1 cells. (C) 1994 Academic Press, Inc.