Enhanced therapeutic effects against murine colon carcinoma induced by a Colon 26/Ag85A-CD226 tumor cell vaccine.

Genetically modified tumor cells represent one of the most effective cancer vaccine strategies. In the present study, we describe our approach for inducing an immune response against a colon carcinoma in BALB/c mice, using a Colon 26 tumor cell line expressing Ag85A and CD226. We investigated whether CD226 plays a promotive role for Ag85A against Colon 26 colon carcinoma. The therapeutic efficacy was investigated. The cytotoxic T lymphocyte (CTL) and natural killer (NK) cell cytotoxicity were assessed. Dynamic changes in interferon (IFN)-γ levels in the spleen and the number of IFN-γ-producing CD4+ or CD8+ T cells in the spleen or mesenteric lymph nodes were detected by enzyme-linked immunoabsorbent assay or flow cytometry. Extended survival times, delayed appearances of tumors, and reduced tumor volumes were achieved by preventive vaccination with the Colon 26/Ag85A-CD226 tumor cell vaccine. NK cell or CTL cytotoxicity in the spleens of mice immunized with the Colon 26/Ag85A-CD226 tumor cell vaccine was significantly higher than that in the other treatment groups. The numbers of CD4+ IFN-γ+ and CD8+ IFN-γ+ T cells were both significantly increased in mice immunized with the Colon 26/Ag85A-CD226 tumor cell vaccine in both the spleen and mesenteric lymph nodes. Our results indicated that the tumor vaccine expressing Ag85A and CD226 induced more intensive antitumor immunity than tumor vaccine expressing Ag85A or CD226 only. Moreover, the results suggest that Ag85A and CD226 play a synergistic antitumor effect and CD226 could be used as a genetic adjuvant to enhance the effects of Ag85A vaccine against murine colon carcinoma.