Figure 2

Treatment of human breast cancer cells with secreted Frizzled-related protein 1 (sFRP1) reduces proliferation and impairs canonical wingless and integration site growth factor signaling and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. (a) One thousand to 5,000 cells of the indicated cell lines were seeded in a 96-well plate, and proliferation was measured in a YOPRO assay after 3 days of treatment with sFRP1 conditioned medium (CM) or control CM. (b) T47D cells were treated for 3 days with 30 μg/mL purified sFRP1 or phosphate-buffered saline, and cell numbers were measured in an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay. The results represent the mean of three experiments (± standard error). *p < 0.05, **p < 0.005, unpaired Student t test, comparison to corresponding control-treated cell line. (c) The indicated human breast cancer cell lines were treated for 2 hours with concentrated sFRP1 CM, and cell lysates were analyzed by SDS-PAGE/immunoblotting for active β-catenin, total β-catenin, p-ERK1/2, and ERK1/2 (upper panel). The results were quantified using ImageQuant (lower panel).