Progestin regulation of EGF-receptor mRNA accumulation in T-47D human breast cancer cells.

Incubation of T-47D human breast cancer cells with the synthetic progestin, medroxyprogesterone acetate (MPA), resulted in a time and dose-dependent increase in epidermal growth factor-receptor (EGF-R) mRNA. Concentrations of MPA as low as 1 nM resulted in a greater than five fold increase in EGF-R mRNA. A significant increase (2-3 fold) in EGF-R mRNA was apparent 12 hr after exposure to MPA and a further increase was seen 12-48 hr after addition of MPA to the cultures. From these studies it is concluded that the increased EGF binding in progestin-treated T-47D cells results at least in part from increased EGF-R gene expression. We believe this is the first report of a steroid hormone modulating expression of this growth factor receptor gene.