FIGURE 1.

IRS1 expression levels are increased by β-catenin signaling in epithelial cells and IRS1 is expressed in the majority of CRC cell lines. A, Western blot and B, Northern blot analyses of parental rat kidney epithelial cell line RK3E and transformed cell lines derived from RK3E cells by transduction of a stabilized mutant of β-catenin (S33Y), wild-type γ-catenin (WTγ), c-MYC, GLI, and G12V mutant KRAS. C, Western blot analysis of IRS1 expression in rat intestinal epithelial cell line IEC18 after transduction of activated β-catenin (S33Y) or empty vector (NEO). D, Western blot analysis of IRS1 expression in selected colorectal carcinoma cell lines. In all panels, equal loading is demonstrated by immunoblotting for β-actin or ethidium bromide staining of 28 S ribosomal RNA, respectively.