HGF upregulates and modifies subcellular distribution of proteins in coloncancer cell enterocytic differentiation

Hepatocyte growth factor (HGF) and its receptor, c-Met, are involved in cel l transformation. To study their role in intestinal cell differentiation, w e used Caco-2 colon cancer cells, which differentiate spontaneously into en terocytes during culture. Cells grown continuously in the presence of HGF r eached confluence more quickly than control cells. Markers of enterocytic d ifferentiation, such as alkaline phosphatase and sucrase-isomaltase activit ies, adhesion molecules, and structural proteins such as E-cadherin, villin , and F-actin were upregulated by HGF throughout the 35 days of culture, an d actin fibers were reorganized. HGF also stimulated expression and tyrosin e phosphorylation of c-Met and Gab-1 as well as protein kinase C (PKC)-alph a expression. PKC-alpha has been shown to be involved in intestinal differe ntiation. We therefore investigated the possibility that increases in PKC-a lpha protein levels were responsible for the HGF-promoted events. We did th is by incubating cells with Go-6976, an inhibitor of PKC-alpha and -beta1, concomitantly with HGF. This inhibitor abolished the HGF-induced increase i n villin levels before, but not after, confluence. Thus HGF accelerates Cac o-2 cell differentiation and stimulates the metabolic and structural events accompanying this process. These HGF-promoted events may be mediated partl y by Gab-1, and the effects of HGF on villin before confluence seem to invo lve PKC.