Intercellular contacts and the organization of actin filaments in cultured epithelial FL cells are altered by growth on type I collagen and treatment with 12-O-tetradecanoylphorbol-13-acetate through the modulation of interactions between cells and the substratum.

We have investigated the effects of various types of collagen and a tumor-promoting phorbol ester on intercellular contacts and the organization of actin in human amnion epithelial FL cells and mouse fibroblast 3T3-A31 cells. Our purpose was to investigate how modulation of interactions between cells and the substratum leads to alterations in intercellular contacts and organization of actin filaments. When cells were cultured on dishes coated with a solution containing type I collagen, but not type IV, changes were induced in the morphology of FL cells and their intercellular contacts. Type I collagen also caused changes in the organization of their actin filaments, although no such effects were observed with 3T3-A31 cells. In contrast, 12-O-tetradecanoylphorbol-13-acetate (TPA) caused morphological changes, dissociation of groups of cells, and reorganization of actin filaments in cultures of FL and 3T3-A31 cells. It also disrupted the sites of adhesion of FL cells to the substratum. Both type I collagen and TPA rapidly induced spreading of FL cells in the absence of serum. However, cis-hydroxyproline, known to inhibit secretion of collagen, did not suppress the TPA-induced dissociation of groups of FL cells. These results suggest that the interactions with type I collagen of epithelial FL cells, but not of fibroblastic 3T3-A31 cells, tend to disorganize cellular morphology, intercellular contacts, and actin filaments in ways similar to, but not directly related to, the effects of TPA.