Decrease of endogenous WT1 abundance by overexpression of zinc finger domain in breast cancer cells. (a) Northern blot: total RNAs were isolated from the stable transfectants of MCF-7 cells with either pcDNA3 control (CON) or the zinc finger domain lacking the lysine–threonine–serine insert (ZF - KTS) of Wilms' tumor 1 suppressor gene (WT1) expression plasmids as indicated, and were analyzed with WT1 and β-actin probes. Overexpressed WT1–ZF, endogenous WT1 (FL WT1) or β-actin RNA is indicated. (b) Western immunoblot: whole cell extracts were prepared from the stable transfectants of MCF-7 cells or MDA468 cells with either pcDNA3 control or ZF - KTS expression plasmids, and were analyzed by western blot with either anti-WT1 and β-actin antibodies. Overexpressed WT1–ZF, endogenous WT1 (FL WT1) and β-actin proteins are indicated.