The effects of EGFR knockdown on steady-state levels of the indicated proteins and phosphoproteins by using phosphospecific antibodies. (A) Western blot analysis with the indicated phosphospecific antibodies showing the effects of EGFR knockdown on EGFRY992, PI3K-p85Y508, and AktT308 in rBT474 and rSKBR3 cells. (B) Western blot analysis of cleaved PARP product in rBT474 and rSKBR3 cells transfected with EGFR siRNA. Scrambled siRNA sequences (NSC) served as controls. Steady-state actin protein served as a control for equal loading of protein. Western blot data shown in A and B are representative of three independent experiments. (C) Effects of siRNA-mediated knockdown of EGFR on tumor cell growth in rBT474 and rSKBR3 cell lines. Results represent the mean ± standard error of triplicate samples and are representative of three independent experiments. P < 0.018 (rBT474) and P < 0.021 (rSKBR3).