Glucocorticoid receptor binding in proliferating and differentiating cells: modulation by a tumour promoting agent

The effects of the tumour-promoting agent, phorbol 12-myristate 13-acetate, on dexamethasone binding and protein kinase C in proliferating and differentiating murine erythroleukemic cells were investigated. Concentration dependent changes in steroid binding were observed in proliferating and differentiating cells treated with phorbol 12-myristate 13-acetate for 2h or 24h. Ligand binding in differentiating cells was consistently lower than in proliferating cells. Reduced expression of protein kinase C was observed in differentiating cells as compared with proliferating cells; the amount of enzyme protein was reduced on treatment of cells with phorbol ester.