Phorbol ester stimulation of fibronectin-mediated cell adhesion.

Stimulation of Chinese hamster ovary cells with 12-O-tetradecanoyl 13-acetate increases the rate of adhesion to fibronectin-coated substratum. The EC50 of the phorbol ester that initiates the change in kinetics of adhesion is approximately 8 nM and is specific to those phorbol esters which activate protein kinase C. When compared to control cells, cells stimulated with active phorbol esters require a significantly lower amount of fibronectin to support their adhesion, and exhibit 50% adhesion inhibition by a log-fold higher concentration of PB1, a monoclonal antibody which specifically blocks fibronectin-mediated adhesion. These results indicate that stimulation of cells with phorbol esters results in a modification of the fibronectin receptor leading to an apparent increase in the interaction of the receptor with fibronectin.