Abstract

Matrix metalloproteinase (MMP) family, in particular MMP-2, may play a key role in angiogenesis and tumor growth. It is conceivable that the breaking of immune tolerance of MMP-2 should be a useful approach to cancer therapy by active immunity. To test this concept, we constructed a plasmid DNA encoding chicken homologous MMP-2 (c-MMP-2) and control vectors. We found that the vaccine based on chicken homologous MMP-2 as a model antigen could induce both protective and therapeutic antitumor immunity. Autoantibodies against MMP-2 in sera of mice immunized with c-MMP-2 could be found by Western blotting analysis and ELISA assay. There was the deposition of autoantibodies within the tumor. IgG1 and IgG2b were substantially increased in response to c-MMP-2 immunization. The elevation of MMP-2 in the sera of tumor-bearing mice was abrogated with the vaccination of c-MMP-2. Transmigration of human endothelial cells and tumor cells through gelatin-coated filters was inhibited with immunoglobulins isolated from mice immunized with c-MMP-2. The gelatinase activity of MMP-2, including both latent MMP-2 (M(r) 72,000) and active MMP-2 (M(r) 66,000) derived from tumor tissues, was apparently inhibited by the vaccination with c-MMP-2. The antitumor activity and the inhibition of angiogenesis were acquired by the adoptive transfer of the purified immunoglobulins. The antitumor activity and production of autoantibodies against MMP-2 could be abrogated by the depletion of CD4(+) T lymphocytes. Angiogenesis was apparently inhibited within tumor, and chick CAMs angiogenesis was also inhibited. Thus, our findings may provide a vaccine strategy for cancer therapy through the induction of an autoimmune response against MMP-2 in a cross-reaction by the immunization with the single xenogeneic homologous MMP-2 gene and may be of importance in the additional exploration of the application of other xenogeneic homologous genes identified in human and other animal genome projects in cancer therapy.