Vaccine-Based Immunotherapy Delays Murine Tumor Growth and Prevents Metastasis

Cancer persists as a leading cause of death globally, and metastatic disease contributes to a large proportion of cancer deaths. Tumor-specific vaccines may be viable immunotherapeutic options for eliminating malignant cells. Since endogenous retrovirus reactivation has been demonstrably linked to tumor metastasis, we propose a novel method to exploit these viral particles in murine tumor models. Methods: Two experiments were conducted. The first experiment included thirty C57BL/6 mice inoculated with MC38 tumor cells. When tumors were palpable, five mice were vaccinated with MC38 infected cells (infect-10), 4T1 cells, BT-20 cells, or 4T1 supernatant (MMTV), while ten mice served as unvaccinated controls. The second experiment included thirty-two BALB/c mice inoculated with 4T1 tumor cells. When tumors were palpable, nine mice were vaccinated with infect-10 cells, seven mice received BT-20 cells, nine mice received MMTV, and seven mice served as unvaccinated controls. Results: In C57BL/6 mice, tumors were significantly smaller (p = 0.019) in the infect-10 treatment group and notably smaller in the BT-20 and MMTV treatment groups compared to controls. In BALB/c mice, the MMTV treatment group had the smallest tumors, although this did not reach statistical significance (p = 0.1). However, lung metastasis was significantly reduced (p = 0.01) in the MMTV treatment group compared to controls. Conclusion: We demonstrate that infect-10 vaccination significantly reduces tumor mass in C57BL/6 mice. Most notably, MMTV vaccination significantly reduces lung metastasis in BALB/c mice. Taken together, we show promising data for future exploration into vaccines that mitigate tumor metastasis.