Dexamethasone increases the synthesis and secretion of a partially active fibronectin in rat hepatoma cells

After treatment with dexamethasone, rat hepatoma-tissue culture cells show a markedly enhanced adhesion to the substratum and increased cell- to-cell interaction. In addition, there is a profound change in the production of secretory glycoproteins. Although the relative synthesis and secretion of a gelatin-binding, fibronectinlike glycoprotein is increased threefold, we do not think this protein is responsible for the improved adhesion properties of the cells because the hepatoma cells do not bind normal fibronectin and because the HTC-produced fibronectin is neither bound by fibroblasts nor has it any affinity for ganglioside-containing phospholipid vesicles. Therefore, these hepatoma cells represent a unique system for studying the regulation of fibronectin synthesis by glucocorticoids. Furthermore, analyses of primary fetal rat hepatocytes have shown that these cells, unlike normal adult hepatocytes, synthesize and secrete fibronectin, which is structurally related to the HTC-cell protein. The comparison of this protein with fibronectin from normal cells will allow a structural characterization of the functional defect in the fibronectin synthesized by transformed cells.