Antigen-specific immunotherapy for murine lung metastatic tumors expressing human papillomavirus type 16 E7 oncoprotein

An important goal of cancer immunotherapy is to prevent and treat tumor metastasis. We have previously reported a recombinant vaccinia-based vaccine (Sig/E7/LAMP-I) that demonstrated significant anti-tumor effect in a subcutaneous tumor challenge model. In this study, we investigated the potency of the Sig/E7/LAMP-I vaccine in preventing and treating metastatic tumors. A tumor metastasis model was generated by injecting human papillomavirus type 16 (HPV-16) E6/E7 expressing tumor cells, designated TC- 1, into the tail vein of syngeneic C57BL/6 mice. All the naive mice injected with 1 x 10⁶ TC-I cells developed tumors confined exclusively to the lungs within 1 month. For in vivo tumor prevention experiments, mice were vaccinated with Sig/E7/LAMP-I followed by tumor challenge. While tumor growth was observed in all of the mice (10/10) in the control groups, 8 of 10 vaccinated mice (80%) remained tumor-free 2 months post-tumor challenge. For in vivo treatment experiments, mice were first inoculated with TC-I cells and then vaccinated with Sig/E7/LAMP-I. Treatment with Sig/E7/LAMP-I was effective in eliminating preexisting tumor cells in 4 of 5 vaccinated mice. Most importantly, treatment with Sig/E7/LAMP-I resulted in regression of fully established lung tumors in 50% (5/10) of vaccinated mice. Our data suggest that the Sig/E7/LAMP-I vaccine is effective in controlling the hematogenous spread of TC-I tumor cells. In addition, the TC-I lung metastasis model can be used to test the efficacy of various E6/E7-specific vaccines and immunotherapeutic strategies.