Rottlerin induces a transformed phenotype in human keratinocytes

PKC delta plays a fundamental role in cell cycle control. Consistent with i ts proposed tumour suppressor function, res transfection of the human kerat inocyte cell. line HaCaT results in a loss of PKC delta expression mediated by TGF alpha (Exp. Cell Res., 219, 299, 1995). To get more insight into th e role of PKC delta in keratinocytes, we investigated the effects of Rottle rin, a specific inhibitor of protein kinase C delta, in HaCaT cells. After Rottlerin treatment, HaCaT cells lost their cobblestone morphology and disp layed a spindle-shaped, fibroblastic phenotype, Additionally, the establish ment of cell-cell contacts was prevented. This was caused by an internaliza tion of E-cadherin and beta -catenin as assessed by immunofluorescence. A s imilar phenotype was observed in the presence of a neutralizing anti-E-cadh erin antibody. Rottlerin-treated HaCaT cells proliferated like transformed cells in a three-dimensional cell culture system. We therefore conclude tha t PKC delta is involved in mediating cell-cell contacts via E-cadherin and hence regulates differentiation HaCaT cells. (C) 2001 Academic Press.