Fig. 1
Autocrine action of 5-HT in MDA-MB-231 human breast cancer cell proliferation and its mediation through 5-HT7 receptor. a, b The mRNA (a) and protein (b) expression levels of TPH1 expression in TNBCs (MDA-MB-231, HCC-1395, and Hs578T) and hormone-responsive breast cancer cells (MCF-7 and T47D). The bar graph represents relative densities of TPH1 (TPH1 mRNA/GAPDH or TPH1 protein/β-Actin) normalized versus those in MCF-7 cells. Results are the means of three independent experiments. *P < 0.05 vs. MCF-7 cells. c 5-HT secretion in TNBCs, hormone-responsive breast cancer cells and MCF-10A human normal breast cells was measured by ELISA. *P < 0.05 vs. MCF-10A cells, # P < 0.05 vs. T47D cells. d Transfection of MDA-MB-231 cells with TPH1 siRNA suppressed proliferation. The bands underneath the bar graph represent TPH1 mRNA expressions detected by PCR. *P < 0.05 vs. non-target (NT) siRNA-transfected controls. e Comparison of cell proliferation induced by 5-HT in MDA-MB-231 and MCF-7 human breast cancer cells. *P < 0.05 vs. vehicle-treated controls. f 5-HT-treated MDA-MB-231 proliferation was examined in the presence of cyanopindolol (CYPD), LY310762, cinanserin (CISN), or SB269970. *P < 0.05 vs. vehicle-treated controls. # P < 0.05 vs. 5-HT-treated cells. g MDA-MB-231 cell proliferation in the presence of serum was inhibited by 5-HT7 antagonist. *P < 0.05 vs. vehicle-treated controls. h, i The mRNA expression determined by real time PCR (h) and protein expression (i) of 5-HT7 receptors in TNBCs (MDA-MB-231, HCC-1395, and Hs 578 T), hormone-responsive breast cancer cells (MCF-7 and T47D), and MCF-10A normal breast cells. *P < 0.05 vs. T47D cells. j Effect of 5-HT on MCF-10A cell proliferation. k Effect of 5-HT receptor-downstream signaling inhibitors on 5-HT-stimulated cell proliferation. *P < 0.05 vs. vehicle-treated controls. # P < 0.05 vs. 5-HT-treated cells