5-HT induces PTHrP and Runx2 mRNA in breast cancer cells. A: PTHrP and Runx2 mRNA measured by quantitative real-time RT-PCR. MCF10A, a nontransformed ductal mammary epithelial cell line, was used as a reference so that all of the breast cancer cell lines could be compared on a single scale. T47D, MDA-MB-231, and MCF7 breast cancer epithelial cell lines were treated with control medium or 5-HT (2 × 10−4 M, 48 h, n = 6, ***P < 0.001). B: concentration (left) and time dependence (right) of PTHrP and Runx2 mRNA induction by 5-HT in MDA-MB-231 cells. CI, confidence interval. Abscissa is labeled with medium 5-HT concentrations (2 × −7 to 2 × 10−3 M) or time (h after addition of 5-HT). Concentration-response was measured at 48 h, and the time course experiment was done with a concentration of 2 × 10−4 M (n = 4 at each point).