Prevention of tumor promoter-mediated inhibition of preadipocyte differentiation by dexamethasone.

A clonal cell line of murine fibroblast (ST 13) undergoes a terminal differentiation into adipose cells in culture. A tumor promoter, 12-O-tetradecanoyl phorbol 13-acetate (TPA), reversibly inhibited the differentiation of ST 13 preadipocytes. The inhibition of differentiation was accompanied by changes in cell morphology and growth properties and by suppression of cellular insulin binding activity. Dexamethasone (DXM) could prevent the inhibition by TPA of preadipocyte differentiation, concomitant with prevention of the morphological changes and an increase in insulin binding activity. TPA-induced plasminogen activator (PA) secretion and DXM-mediated inhibition of PA activity could not be correlated with inhibition/prevention-of-inhibition of differentiation.