Figure 4. Inhibition of mTOR by rapamycin blocks Her2-mediated up-regulation of MDM2.

(A) MCF-7 cells were serum-starved and pre-treated with rapamycin (50 nM) for four hours, and then treated with Heregulin-beta (HRG; 25 ng/mL) for 24 hours. Cells were lysed and subjected to western blot analysis. (B) Serum-starved H1299 cells were pre-treated with rapamycin (50 nM) or LY294002 (20 µM) for four hours, and then treated with Heregulin-beta (25 ng/mL) for 24 hours. Cell lysates were subjected to western blot analysis.