Vaccine-induced anti-HER2 antibody treatment of established human breast tumor xenografts in mice suppresses tumor growth. (A) Schema for the passive transfer of vaccine-induced antibodies to treat established BT474M1 human breast tumor xenografts in NOD.CB17-Prkdcscid/J mice. (B) Mean tumor volume ± standard error (mm3) for AdGFP-VIA-treated (solid squares) and AdHER2-VIA-treated (open squares) mice is presented as a time course from day 14 (initiation of HER2-VIA or GFP-VIA injections) through day 39 (tumor harvest). *P <0.05, **P <0.001. (C) Schema for the passive transfer of vaccine-induced antibodies to treat established HCC1569 human breast tumor xenografts in NOD.CB17-Prkdcscid/J mice. (D) Mean fold-change in tumor growth of implanted HCC1569 cells for the mice treated with HER2-VIA or PBS for days 8 through 20. **P <0.001. (E) Effect of vaccine-induced anti-HER2 antibodies (HER2-VIA) and trastuzumab on human breast cancer cell proliferation. HER2-positive cells (BT474 or SKBR3) were treated with 3 µl pooled mice crude serum in 100 µl culture medium for 3 days and cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoliumbromide assay. Trastuzumab (Herceptin) (10 µg/ml) was used as a positive control and sera from mice receiving Ad-LacZ vaccine (VIA-SHAM) or saline (untreated) were used as negative controls. Proliferation is plotted relative to the growth of cells in the untreated condition. Error bars represent standard deviation. Data are representative of four experiments. P <0.001.