Overexpression of Protein Kinase C{{alpha}} in MCF-10A Human Breast Cells Engenders Dramatic Alterations in Morphology, Proliferation, and Motility

A nonmetastatic human mammary epithelial cell line (MCF-10A) was engineered to overproduce protein kinase Ca (PKCa) so as to investigate a role for this isoform in the metastatic phenotype. PKCa transfectants (clone 26a) expressed an 8-fold higher level of PKCa protein without compensatory alterations in other isoforms. Clone 26a proliferated slowly (accumulating in G 1 of the cell cycle) but exhibited pronounced increases in motility and adhesion. Elevated expression of cell cycle inhibitor p27 and focal adhesion proteins was observed, whereas Ecadherin expression decreased to undetectable levels. These observations were consistent with the morphology of PKCa transfectants (large, disaggregated, and flat, with lamellipodia and extensive actin fibers) and control cells (small, aggregated, and refractile). Treatment with PKC inhibitors or transfection of a dominant negative (dn) mutant of Rac1, but neither dn RhoA nor dn cdc42, reduced the motility of clone 26a, implicating PKCa catalytic activity and endogenous Rac1, respectively, in the PKCa-induced phenotype. Overall, PKCa overexpression suppresses proliferation while endowing MCF-10A cells with properties consistent with the metastatic phenotype.