[Cell adhesion in rat fibroblasts: effect of tumor promoters].

In a study performed on transformed (SGS/3A) and normal syngeneic rat cells (FG/2) to identify the molecular mechanisms which regulate cell adhesion and contact inhibition in cell transformation, we investigated the effects of tumor promoters on cell to cell adhesion of rat fibroblasts. As tumor promoters we used 12-tetradecanoyl-phorbole-13-acetate (TPA) and the melittin, a polypeptide from bee venom, both substances capable of stimulating the neoplastic transformation. The intercellular adhesion assay consists in determining the percent of single cells labeled with 3H-L-leucine adhering to a confluent monolayer of unlabeled cells at different incubation times. The increase of cell-cell adhesion caused by TPA and melittin confirms what we have constantly observed in other experiments, i.e. that neoplastic cells SGS/3A always have a higher intercellular adhesion capacity than corresponding normal syngenic cells FG/2. Since one of the effects of the tumor promoters is also induction of a reversible alteration of the cytoskeleton, it is likely that their action on intercellular adhesion is regulated by a mechanism analogous to that proposed for explaining the increased intercellular adhesion observed after treatment with antimicrotubular compounds.