PP1 or AZD0530 tyrosine kinase inhibitors had no effect on ERα protein degradation in MCF-7 cells.

In panels (A) and (B), ERα protein expression after 6-hour exposure to 100 nM fulvestrant in the presence of PP1 or AZD0530 was determined by Western blotting (A) and ELISA (B, mean±SEM of three or more independent experiments. Asterisks indicate statistical significance, p<0.05, to fulvestrant-only group). In panels (C) and (D), fulvestrant concentration was reduced as indicated, and ERα protein expression after 6-hour exposure in the presence of PP1 or AZD0530 was determined by Western blotting (C). Panel (D) shows a typical densitometric quantitation of the ERα protein band. Three independently performed experiments did not show statistically significant effects of PP1 or AZD0530.