Anti-Tumor Angiogenic Effect Of Immunotherapy With Vaccine Based On The Recombinant Chicken FGFR-1 In Mice

It is generally believed that the growth and metastases of a tumor are angiogenesis-dependent and thus that anti-angiogenic therapy, which targets genetically stable endothelial cells as a strategy for cancer therapy, is highly warranted. At present, basic fibroblast growth factor (bFGF) has been shown to be one of the most important angiogenic growth factors for tumor angiogenesis. bFGF conducts its biological function through interaction with its high-affinity receptor, fibroblast growth factor receptor-1(FGFR-1), which is markedly expressed both in active endothelial cell and in many different forms of tumor and plays an important role in tumor angiogenesis and tumor growth. Thus, it is logical to consider using FGFR-1-mediated anti-angiogenesis as a target of immune therapy for tumor treatment, which could suppress angiogenesis and further inhibited tumor growth by block the bFGF/FGFR-1 signal transduction. Studies suggested that passive immunotherapy with a monoclonal antibody FGFR-1-mediated anti-angiogenesis could inhibit tumor growth, but the blocker may be involved some side-effects. Moreover, much recent evidence has also confirmed that xenogeneic homologous molecules can induce cross-reaction against self homologous molecules. Furthermore, other findings have also demonstrated that antiangiogenic therapy combined with chemotherapy could more effectively inhibited tumor growth without overt toxicity than either therapy alone. So the antiangiogenic therapy in solid tumors should be used as a new approach for cancer therapy with active immunity or combined with chemotherapy agents.To test this notion, in the first part, we recombined the extracellular domain of chicken FGFR-1(cFR) protein vaccine and a mouse FGFR-1 (mFR) protein vaccine as a homologous control. We found that immunotherapy with cFR vaccine was effective at both protective and therapeutic antitumor immunization in two mouse tumor models. The tumor volume was significantly smaller and the survival time was significantly longer in cFR-1-immunized group than those in control groups. Auto-antibodies against mouse FGFR-1 were found in sera of mice immunized with cFR in Western blotting analysis and ELISA assay. Anti-FGFR-1 antibody producing B cells (APBCs)were were observed in all cFR-immunized mice, which detectable by ELISPOT. The endothelial deposition of autoantibodies was found within tumor tissues from cFR-immunized mice, which were detected by immunofluorescent staining.The antitumor activity and production of autoantibodies against FGFR-1 could be abrogated by depletion of CD4+T lymphocytes. The antitumor activity was also induced by the adoptive transfer of the purified immunoglobulins was apparently inhibited within the tumors. The microvessel density, which stained with antibodies reactive to CD31, was also significantly less in the cFR-1-immunized mice than in controls.In the second part, we evaluated primarily the antitumor activities of low-dose gemcitabine combined with a recombinant cFR vaccine in a mouse colon adenocaicinoma model. We found that low-dose gemcitabine or cFR vaccine treatment resulted in the inhibition of tumor growth to a certain extent. Remarkably, the combination therapy results in apparent decreases in tumor volume, microvessel density and tumor cell proliferation, and an increase in apoptosis without obvious side-effects as compared with either therapy alone or normal control groups. Moreover, the low-dose gemcitabine did not inhibit the host cross-immune response, but it potentiated anti-tumor effects as was demonstrated in the synergistic indexes of tumor volume, MVD, apoptosis and proliferation, and the presence of both auto-antibodies and the APBCs in the cFR-1-immunized mice.Taken together, these findings demonstrates that the mechanism of antitumor effects may be related to the autoantibodies against mouse self-FGFR-1 induced by cFR1 immunizaton could block the bFGF/FGFR-1 signal transduction, may involve CD4+ T lymphocytes, and further inhibited tumor growth by mediated anti-angiogenesis. The combination therapy strategy effectively and synergistically suppressed tumor growth via inhibition of tumor angiogenesis without systemic toxicity, which the low-dose gemcitabine did not inhibit the hose immune response. Moreover, no overt toxicity was found in all of the mice. Our study may provide an alternative strategy for treatment of tumor angiogenesis and needs further investigation.