The therapeutic effects of AR and MEK inhibitors on in vivo tumor growth and cellular proliferation. (A) Fold change in tumor volume is shown for each in vivo treatment group using MDA-MB-453 xenograft model. CTL: control group; FLU: flutamide; PD: PD0325901. *P < 0.01 for the combination therapy group vs. control or monotherapy groups using Mann-Whitney U test. Error bars: ± 2 SEM. (B) Representative image of xenograft tumors in flutamide monotherapy and combination therapy groups. (C) Immunohistochemistry (IHC) was used to measure the proliferation index in a control xenograft tumor. Staining was carried out using a Ki-67 rabbit polyclonal antibody. Original magnification, ×60. (D) IHC was used to measure Ki-67 proliferation index in a xenograft tumor treated with the combination therapy. Original magnification, ×60. (E) Tumor proliferation indices using Ki-67 nuclear staining for the xenograft experiments. *P < 0.05 for monotherapy groups vs. control and **P < 0.05 for combination therapy vs. monotherapy groups. Error bars: ± 2 SEM.