Overexpression of SIRT1 promotes breast cancer cell growth in vitro and in vivo. (A) Western blot analysis of SIRT1 expression in MDA-MB- 231 and MCF-7 cell lines with or without stably overexpressed SIRT1. (B) Cell viability assay (C) Colony formation assay (D) Cell cycle analysis in MDA- MB-231 and MCF-7 cells with or without stably overexpressed SIRT1 (Data were presented as means±SEM. *p<0.05, **p<0.01, Student's t-test. Cell viability analysis with n=6; the rest analyzed with n=3). (E) Cell apoptosis (F) Cell migration ability in MDA-MB-231-SIRT1 and MDA-MB-231-Vector cells (Data were presented as means±SEM. **p<0.01, NS=no significance, Student's t-test. n=3). (G) In vivo tumor formation assay of MDA-MB-231-SIRT1 and MDA-MB-231-Vector breast cancer cells. At the end of the experiment, the tumors were dissected from mice. Volumes and weights of tumors between two groups were analyzed (Data were presented as means±SEM. **p<0.01, ***p< 0.001, Student's t test). (H) Representative IHC staining of SIRT1 and Ki67 in xenograft tumors between two groups (Bar=100 μm).