Treatment with mANT2 shRNA enhances antitumor therapeutic effects induced by MUC1 DNA vaccination

In this study, we developed a combination therapy (pcDNA3/hMUC1+mANT2 shRNA) to enhance the efficiency of MUC1 DNA vaccination by combining it with mANT2 short hairpin RNA (shRNA) treatment in immunocompetent mice. mANT2 shRNA treatment alone increased the apoptosis of BMF cells (B16F1 murine melanoma cell line coexpressing an MUC1 and Fluc gene) and rendered BMF tumor cells more susceptible to lysis by MUC1-associated CD8(+) T cells. Furthermore, combined therapy enhanced MUC1 associated T-cell immune response and antitumor effects, and resulted in a higher cure rate than either treatment alone (pcDNA3/hMUC1 or mANT2 shRNA therapy alone). Human MUC1 (hMUC1)-loaded CD11c(+) cells in the draining lymph nodes of BMF-bearing mice treated with the combined treatment were found to be most effective at generating hMUC1-associated CD8(+)IFNγ(+) T cells. Furthermore, the in vitro killing activities of hMUC1-associated cytotoxic T cells (CTLs) in the combined therapy were greater than in the respective monotherapies. Cured animals treated with the combined treatment rejected a rechallenge by BMF cells, but not a rechallenge by B16F1-Fluc cells at 14 days after treatment, and showed MUC1 antigen-associated immune responses. These results suggest that combined therapy enhances antitumor activity, and that it offers an effective antitumor strategy for treating melanoma.