Integration of Mechanical and Soluble Signaling in Tumor Angiogenesis

Northeast Ohio Medical University, Rootstown OH

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Abstract

? DESCRIPTION (provided by applicant): Solid tumors require angiogenesis for the growth and metastasis. Although conventional anti-angiogenesis modalities targeting VEGF and other soluble factors were promising in pre-clinical studies, they were unsuccessful in clinics as the tumors become refractory to anti-VEGF treatments. Further, the irregular and leaky tumor vasculature poses an obstacle to efficient delivery of anti-cancer drugs to the tumor. This R15 AREA application addresses both of these problems by focusing on novel mechanotransduction pathway in tumor angiogenesis to induce vascular normalization and to efficiently deliver anti-cancer drugs. We have recently found that TRPV4 expression is reduced in tumor-derived endothelial cells (TEC) which exhibited high Rho activity and abnormal angiogenesis in vitro, and that overexpression of TRPV4 significantly inhibited Rho activity and normalized angiogenesis by TEC in vitro. Further, we demonstrated that TRPV4KO tumors exhibited a greater fraction of hyper-dilated (malformed) and leaky vessels with poor pericyte coverage indicating the immature nature of these vessels. Intriguingly, we found that TRPV4KO tumors exhibit increased VEGFR2 expression compared to WT tumors which suggest that a cross-talk may occur between mechanical and growth factor signaling in tumor angiogenesis. Importantly, our preliminary results revealed that TRPV4 modulates the expression and phosphorylation of p190RhoGAP, which was shown to regulate Rho activity as well as VEGFR2 expression in EC. These findings are of significant clinical importance since mechanosensing of tumor microenvironment by EC is critical for abnormal vessel formation in tumor and to our knowledge, mechanosensitive ion channels have not been explored as potential targets for tumor angiogenesis/vascular normalization therapy. Thus, our working hypothesis is that endothelial TRPV4 channel act as a mechanosensor of ECM stiffness and regulates tumor angiogenesis through the integration of mechanical (Rho) and soluble (VEGF) signaling via modulation of p190RhoGAP. We plan to test this hypothesis in the following specific aims 1) Define the molecular mechanisms by which TRPV4 integrates mechanical (Rho) and soluble (VEGF) signaling in endothelial cells and 2) Determine the role of endothelial TRPV4 in regulation of VEGFR2 expression, tumor angiogenesis and vessel maturity in vivo, using a mice in which TRPV4 is specifically deleted in endothelial cells (TRPV4ECKO mice). Overall, this R15 project offers a unique opportunity to understand mechanotransduction mechanisms in tumor angiogenesis and develop novel mechanotransduction based vascular normalization (anti-angiogenic) therapies for the treatment of cancer. Finally, we believe that support from an AREA grant will not only enhance the cancer research environment at NEOMED (which is focused on areas such as cardiovascular, metabolic and skeletal biology), but will also provide opportunities for graduate and medical students to be exposed and engaged in cancer research.