[A DNA vaccine encoding the extracellular domain of porcine endoglin induces antitumor immunity in a mouse colon carcinoma model].

BACKGROUND & OBJECTIVE: Endoglin is a marker of tumor angiogenesis. Increasing evidences proved that passive immunotherapy with anti-endoglin monoclonal antibody can effectively inhibit tumor growth, and xenogeneic homologous DNA vaccine can inhibit cross antitumor immunity. This study was to explore the inhibitory effect of a DNA vaccine encoding the extracellular domain of porcine endoglin (ppEDG) on tumor growth in a mouse colon carcinoma model.

METHODS

ppEDG was used as a DNA vaccine to actively immunize the colon carcinoma-bearing mice. Tumor volume and survival rate of the mice were observed in 3-day intervals. Microvessel density (MVD) was detected by immunohistochemistry; antibodies against self-endoglin were detected by Western blot and ELISA; the B cells that secrete auto-antibodies against self-endoglin were detected by ELISPOT assay.

RESULTS

Eighteen days after tumor cell inoculation, the tumor volume was significantly smaller in ppEDG-immunized group than in empty plasmid (e-p) group and normal saline (NS) group (P<0.05), and the survival time was significantly longer in ppEDG-immunized group than in the control groups (P<0.001). MVD was significantly lower in ppEDG-immunized group than in e-p group and NS group (19.2+/-4.5 vs. 76.9+/-14.4 and 81.4+/-16.9, P<0.001). The antibodies against self-endoglin were identified in ppEDG-immunized group; the major subtypes were IgG(1) and IgG(2b). The auto-antibody-producing B cells were much more in ppEDG-immunized group than in e-p group and NS group (82.5+/-14.1 vs. 3.6+/-1.3 and 4.7+/-2.0, P<0.001).

CONCLUSION

ppEDG DNA vaccine could induce the production of auto-antibodies against self-endoglin, which further inhibit angiogenesis and growth of colon carcinoma.