br Bazedoxifene inhibited the expression

3.5. Bazedoxifene inhibited the expression of estrogen receptor, p-STAT3
To investigate the mechanism by which bazedoxifene inhibited breast cancer, we studied the expression of proteins after bazedoxifene was applied to treat breast cancer cells. Fig. 5A shows that T47D, BT474 and MCF7 Protease Inhibitor Cocktail had strong basal expression of estrogen receptor, while 4T1, MDA-MB-468 and MDA-MB-231 cells had no basal estrogen re-
was much less than in 4T1, MDA-MB-468 and MDA-MB-231 cells [20]. Previous reports have indicated that bazedoxifene inhibited MCF7 cell growth and functioned as a pure estrogen receptor antagonist [21]. In addition to MCF7, we also studied the mechanism by which baze-doxifene inhibited estrogen receptor-positive breast cancer cells in BT474 and T47D. Western blot (Fig. 5B, C, and D) showed that baze-doxifene downregulated the expression of estrogen receptor in all three estrogen receptor positive breast cancer cells, consistent with other findings [21,22]. Fig. 5B also showed that bazedoxifene dose-depen-dently inhibited the expression of p-P70S6K, survivin, c-Myc and Bcl-2
in MCF7 cells.
At present, there are few published studies about the inhibitory
Fig. 1. Bazedoxifene inhibited cell viability of breast cancer cells and exhibited synergistic effects with paclitaxel treatment. (A) Breast cancer cells were treated with bazedoxifene at the indicated concentrations in triplicate for 48 h and processed for MTT assay to analyze cell viability (*, P < .05; **, P < .01; ***, P < .001). (B) MCF7, MDA-MB-231 and 4T1 cells were treated with bazedoxifene or/and paclitaxel at the indicated concentration in triplicate for 48 h and processed for MTT assay to analyze cell viability (*, P < .05; **, P < .01; ***, P < .001).
effect of bazedoxifene on TNBC and its mechanism. As shown in Fig. 5E,
F, G, bazedoxifene dose-dependently inhibited the expression of p-STAT3 (Y705) without suppressing total STAT3 in MDA-MB-231, MDA-
3.6. Bazedoxifene alone or combined with paclitaxel suppressed tumor growth of breast cancer in vivo
Studies have found that bazedoxifene can inhibit MCF7 mouse xe-nografts. To explore the inhibitory effect of bazedoxifene on trans-planted tumors of triple-negative breast cancer in mice, we implanted 4T1 and MDA-MB-231 cells to establish mouse xenograft tumor models. Fig. 6A, B and C show data from 4T1 transplantation in the mouse mammary fat pad model; Fig. 6D, E and F show data from MDA-MB-231 transplantation in the mouse mammary fat pad model. As shown in Fig. 6A and D, tumor volume treated by bazedoxifene was significantly decreased compared with the tumor size in vehicle control group, in-dicating that bazedoxifene could suppress TNBC growth in vivo. Con-sistent with cell viability, cell proliferation and apoptosis experiments, Fig. 6D also showed that the combination of bazedoxifene and pacli-taxel significantly inhibited the growth of TNBC in vivo more than monotherapy. Fig. 6B and E showed that bazedoxifene inhibited the 
increase of tumor weight, and bazedoxifene combined with paclitaxel was more effective in inhibiting tumor growth than either drug alone.
and MDA-MB-231 cells, but did not affect the expression of STAT3, and upregulated the expression of cleaved caspase-3, thereby inhibiting the growth of these breast cancer cells in vivo.
4. Discussion
In this study, we found that bazedoxifene dose-dependently in-hibited the cell viability of both estrogen receptor positive breast cancer cells and TNBC cells, as well as TNBC tumor growth in vivo. Combinational treatment of bazedoxifene along with the conventional chemotherapeutic agent paclitaxel synergistically impeded cell viabi-lity, colony formation, and cell migration and induced apoptosis far more significantly than single drugs alone. Western blotting revealed that bazedoxifene could inhibit the expression of estrogen receptor and downstream signaling molecules such as cyclin D1, p-P70S6K, survivin,