Abstract: ObjectiveTo investigate the influence of wild-type PTEN gene on chemo-sensitivity of Epirubicin in breast cancer cell lines MCF-7 and ZR-75-1. MethodsThe wild-type PTEN gene was transfected into human breast cancer cell line MCF-7 and ZR-75-1 by recombinant adenoviruses (Ad-PTEN). The expression of PTEN gene mRNA was analyzed by RT-PCR and the PTEN protein was identified by Western blot. The effect of Epirubicin alone or combined with Ad-PTEN on cell survival rate was measured by CCK-8 test. ResultsAdenovirus-mediated PTEN gene transfer system obviously increased the expression of PTEN mRNA and protein in cells. After treatment with Ad-PTEN, the chemosensitivity of breast cancer cells to Epirubicin increased about two folds in MCF-7 cells and ten folds in ZR-75-1 cells. ConclusionThe synergism of Ad-PTEN to epirubicin obviously increased the cytotoxicity on breast cancer cell lines.