Figure 1. c-Jun is regulated by Smad2, Smad3 and Smad4 in the canonical TGFβ-regulated pathway in breast and prostate cancer cells. (A–C) Cell lysates from PC-3U cells transiently transfected with non-targeting control siRNA (CTRL siRNA) or siRNA specific for Smad4 (A) Smad2 (B) or Smad3 (C) specific siRNA were subjected to immunoblotting for Smad4, Smad2, and Smad3, respectively, and total c-Jun. Actin served as internal control. (D and E) RNA isolated from PC-3U cells and Smad4 homozygous null MDA-MB-468 cells (MD468) treated with TGFβ, as indicated, were subjected to qRT-PCR, to analyze mRNA expression of c-Jun (D) and Snail1 (E). The cell lysates derived from PC-3U cells and MD468 cells treated with TGFβ, were subjected to immunoblotting to determine the amounts of total c-Jun, Snail1 and Smad4 proteins (F). Actin served as internal control.