Figure 2.
β-catenin siRNA suppression of IGF-I-promoted β-catenin and cyclin D1 mRNA expression in OL-1 cells. Panel A. Schematic of the time course of the β-catenin siRNA experiment. OL-1 cells were treated with β-catenin siRNA (5 nM of each 5′ and 3′ end β-catenin siRNA) or a negative control siRNA (10 nM) for 24 hr. Medium was then replaced with low insulin SFM, and cells were incubated with or without 100 ng/ml of IGF-I for an additional 24 hr. Panel B. Quantification of β-catenin (βCat) mRNA abundance, as well as that of MBP, PLP, HDAC11 (HD11) and cyclin D1 (cycD1), in cells pre-treated with β-catenin siRNA. *, P < 0.05, compared to cells treated with control siRNA (neg siRNA). Panel C. Quantification of β-catenin and cyclin D1 mRNA abundance in IGF-I-treated cells that were pre-transfected with β-catenin siRNA or control siRNA (neg siRNA). mRNA abundance is expressed as a percentage of their non-IGF-I-treated controls (open columns), and values represent mean ± SE of 3–5 samples. *, P < 0.01; **, P < 0.001; compared to non-IGF-I treated controls. ^, P < 0.001; compared to IGF-I treated cells that were pre-transfected with negative control siRNA. Panel D. The number of Ki67+ proliferating cells in IGF-I-treated cells that were pre-transfected with β-catenin siRNA or control siRNA (neg siRNA). Values represent mean ± SE from 3–5 samples. *, P<0.02; **, P<0.001, compared to their respective non-IGF-I treated controls; ^, P<0.01, compared to IGF-I treated cells that were pre-transfected with control siRNA.