HER-2 overexpression inhibits transforming growth factor (TGF)-β1 target gene induction in the luminal MCF-7 and ZR-75-1 breast cancer cells. (a) Northern blot analysis of CTGF and PAI-1 expression. The membrane contained total RNA from the indicated CN and H2 cells treated with either diluent control (0 h) or 2 ng/ml TGF-β1 (8 or 24 h). (b) HER-2 overexpression prevents p15INK4B induction in MCF-7 and ZR-75-1 cells by TGF-β1. Western blot analysis of total cellular extracts prepared after treatment with diluent control (0 h) or 2 ng/ml TGF-β1 (8, 24 or 52 h). Bottom panels are the same membranes re-probed with an antibody to cdk4.