The complete preventive effect of homologous tumor vaccines – Based on a 5-year experimental study in mice

By using a frozen-thaw method, we developed homologous and heterologous cell-based tumor vaccines, which were derived from mouse H22 hepatoma, S180 sarcoma and human A549 lung carcinoma, SK-OV-3 ovarian, and SMMC-7721 hepatoma cell lines. The prophylactic and therapeutic effects of those vaccines were evaluated in mice challenged with live H22 or S180 cells. The result demonstrated that homologous vaccines and heterologous vaccines had no therapeutic effect on tumor growth. However, homologous vaccines showed a complete prevention against live H22 and S180 cell challenge and they could stimulate cross-immune response of anti-tumor in mice. Furthermore, these tumor-free mice immunized with homologous vaccines showed full protection against the repeat challenge every 3 months for 5 years. The study also revealed that tumor-free female, not male, mice transferred anti-tumor ability to some of their offsprings. Heterologous vaccines exhibited no protective effect on tumor development. Immunological analysis discovered that activities of CTLs and NK were enhanced and the levels of IL-2, IL-12 and IFN-γ were significantly increased. Our results demonstrated that homologous tumor vaccines could elicit complete cross-protection against the lethal challenge of tumor cells through enhancing cell-mediated immune response, which lasted for 5 years in mice. These observations may provide a new vaccine strategy for tumor prevention.