Influence of tumor promoter on binding and release of fibronectin added to human lung fibroblasts.

The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) did not alter the binding and release kinetics of externally added 125I-labeled plasma fibronectin to human lung fibroblasts in culture. Cell layer-bound plasma fibronectin was found to be chased into the medium at the same rate in tumor-promoter-treated as in non-treated cells. Unlabeled fibronectin accumulated to a much higher degree in the medium when tumor promoter was present. We conclude that TPA does not interfere with the fibronectin receptor on substrate-attached fibroblasts, but may influence intracellular fibronectin before it is bound to the extracellular matrix.