Anti-tumor angiogenesis effect of genetic fusion vaccine encoding murine beta-defensin 2 and tumor endothelial marker-8 in a CT-26 murine colorectal carcinoma model.

ABSTRACT

Tumor endothelial marker 8 (TEM8) is an endothelial-specific marker that is upregulated during tumor angiogenesis. We previously demonstrated that DNA-based vaccine encoding xenogeneic TEM8 can potentiate anti-angiogenesis immunotherapy of malignancy; nevertheless, it remains to be improved in minimizing immune tolerance. Recently, it has been reported that murine beta-defensin 2 (MBD2) is chemotactic for immature dendritic cells and plays a pivotal role in breaking immune tolerance. Herein, we constructed a genetic fusion vaccine encoding murine TEM8 and MBD2 to investigate whether the novel vaccine preferentially elicits therapeutic antitumor immune responses and suppresses cancerous angiogenesis in mouse models. The anti-angiogenesis effect was determined by microvessel density (MVD) using immunohistochemical staining. The efficacy of the fusion vaccine was primarily assessed by detecting cytotoxic T lymphocyte activity ((51)Cr-release assay). Enzyme-linked immunosorbent spot (ELISpot) assay was used to detect TEM8-specific INF-γ production, and the activity of CTL was further verified by a depletion of CD8(+) T cells via anti-CD8 monoclonal antibody. Our results showed that the DNA fusion vaccine possessed an enhanced therapeutic antitumor immunity through anti-angiogenesis in BALB/c mice inoculated with CT26 cells, and this effect was generally attributed to stimulation of an antigen specific CD8(+) T-cell response against mTEM8. In conclusion, our study demonstrated that the fusion vaccine based on mTEM8 and MBD2 induced autoimmunity against endothelial cells, resulting in deceleration of tumor growth, and could be potential therapeutical application in clinic.