Simultaneous Targeting of Multiple Angiogenic Pathways in Cancer

Tumor cells exhibit uncontrolled proliferation, which is supported and accelerated by a constant supply of nutrients carried by blood vessels. Tumor angiogenesis, the formation of new blood vessels, besides its contribution to tumor growth, also allows the dissemination of tumor cells into distant organs. In addition to the hematogenous routes, the tumor cells metastasize through lymphatic vasculature as well. Tumor-associated lymphangiogenesis, the formation of new lymphatic vessels, is a key process in this regard. Multiple growth factor pathways regulate angiogenesis and lymphangiogenesis. Among the most important vascular growth factors implicated in this regulation are vascular endothelial growth factors (VEGFs) and angiopoietin growth factors (Angs). It has been shown that targeting VEGF/VEGFR-2 pathway could inhibit tumor growth. Many studies during the last decade have demonstrated that attenuating VEGFR-3 function inhibits primary tumor growth and also metastasis. Selective antibodies against Ang2 were shown to inhibit tumor growth and metastasis in different tumor models in mice. However, the question regarding whether combining different therapeutic methods, namely anti-VEGFR-2, anti-VEGFR-3 and anti-Ang2, will have additive benefits in comparison to single-agent therapies still remains. We aimed to test the inhibitory effects of simultaneous targeting of all VEGF pathways and Ang2 on primary tumor growth in human lung carcinoma xenografts in immunodeficient mice. To achieve this, we used soluble VEGF – trap (Aflibercept), VEGF-C/D – trap and antibodies against Ang2. Our results show that triple therapy significantly improves the inhibition of primary tumor growth in comparison to monotherapies and dual therapies. Combination of all 3 treatments also improved the reduction of intra-tumor blood vessels and lymphatic vessels. The effects of triple targeting on controlling metastasis, however, was not significant in orthotopic breast cancer model, mainly due to great variation in tumor growth in this model. However, a clear trend of reduced metastasis in several organs (liver, kidneys) was observed. Overall, this study suggests that attenuating all VEGF pathways and Ang2 could improve the inhibitory effects of anti-angiogenic treatments