Fig. 5.

PP2 and trastuzumab inhibit the formation of ER-c-Src-HER2 and partially restore tamoxifen sensitivity. a BT474 cells were treated with PP2 (10 μM) for 4 h and subjected to immunoprecipitation and immunoblotting as indicated. b MTT assays in BT474 cells treated with PP2 (10 μM) for 4 h and then treated with 17β-E2 (10 nmol/L) and/or tamoxifen (1 μmol/L) for 48 h. *P < 0.05. c BT474 cells were treated with trastuzumab (10 μg/ml) for 4 h and subjected to immunoprecipitation and immunoblotting as indicated. d MTT assays in BT474 cells treated with trastuzumab (10 μg/ml) for 4 h and then treated with vehicle (CON), 17β-E2 (E2) (10 nmol/L), tamoxifen (TAM) (1 μmol/L) or combination treatment (E2/TAM) for 48 h. *P < 0.05. e Western blot analysis of c-Cbl protein in BT474 cells treated with tamoxifen (TAM) (1 μmol/L), TAM (1 μmol/L) combined with PP2 (10 μM), or TAM (1 μmol/L) combined with trastuzumab (10 μg/ml)