Rottlerin Induces a Transformed Phenotype in Human Keratinocytes

Abstract

PKCδ plays a fundamental role in cell cycle control. Consistent with its proposed tumour suppressor function, ras transfection of the human keratinocyte cell line HaCaT results in a loss of PKCδ expression mediated by TGFα (Exp. Cell Res., 219, 299, 1995). To get more insight into the role of PKCδ in keratinocytes, we investigated the effects of Rottlerin, a specific inhibitor of protein kinase Cδ, in HaCaT cells. After Rottlerin treatment, HaCaT cells lost their cobble-stone morphology and displayed a spindle-shaped, fibroblastic phenotype. Additionally, the establishment of cell–cell contacts was prevented. This was caused by an internalization of E-cadherin and β-catenin as assessed by immunofluorescence. A similar phenotype was observed in the presence of a neutralizing anti-E-cadherin antibody. Rottlerin-treated HaCaT cells proliferated like transformed cells in a three-dimensional cell culture system. We therefore conclude that PKCδ is involved in mediating cell–cell contacts via E-cadherin and hence regulates differentiation in HaCaT cells.