Effects of rAAV/ TRE/HSVtk/Tet-On on MCF-7 cells in the presence of GCV followed by the induction of Dox. MCF-7 cells were transduced with various doses of rAAV/TRE/HSVtk/Tet-On. Twenty-four hours after transduction, the rAAV+Dox+GCV group (blank bar) cells were exposed to 3.0 μg/ml GCV and 1.0 μg/ml Dox while the rAAV+Dox group (black bar) cells with 1.0 μg/ml Dox and the rAAV+GCV group (hatched bar) cells with 3.0 μg/ml GCV. After 3 days, the survival rate was calculated as described in Materials and Methods. Data showed that the survival rate of the rAAV+Dox+GCV group cells was different from that of the other two groups cells. Values are expressed as means ± SD.