Abstract 4544: Novel TDA technology and high content imaging as complementary assay platforms to identify VEGFR-2 inhibitors.
Authors: Kelvin Lam, Edward Esposito, Deanna Navaroli, Ryan Clinton, Kerrin Beovich, Norman Garceau
Journal: Cancer Research (2013)

Abstract Vascular endothelial growth factor (VEGF) is potent mitogen for endothelial cells that signals through VEGF Receptor-type2 (VEGFR-2)/Flk-1/KDR. Binding of VEGF to VEGFR-2, a membrane bound receptor tyrosine kinase of the VEGF-receptor family, leads to receptor dimerization, protein kinase activation, trans-autophosphorylation, and initiation of signaling pathways stimulating angiogenesis. In adults, angiogenesis normally occurs during wound healing to restore blood flow post injury and during menstruation and pregnancy. Angiogenesis is also involved in several pathological disease states such as rheumatoid arthritis, psoriasis, diabetic retinopathy and cancer. While physiological angiogenesis involves interplay between pro- and anti-angiogenic factors, the ability to inhibit pathological angiogenesis has therapeutic potential. Inhibitors of VEGFR-2 provide targeted treatments for tumor growth as well as abnormal neovascularization related diseases. The caveat of traditional biochemical VEGFR-2 assays is that only the catalytic domain of the receptor is used to identify hits. One strategy to identify true novel inhibitors against membrane associated proteins is to screen these targets in a more physiological environment, where lipid-protein and protein-protein interactions are included in the assay. We achieved this goal by docking the entire cytoplasmic domain of the receptor on a liposome. Template Directed Assembly (TDA) is a screening technology designed to accomplish this objective. TDA technology utilizes recombinant VEGFR-2 cytoplasmic domain tagged with polyhistidine at the juxtamembrane position and docked to the liposome via the nickel residues. The lipids in TDA are able to diffuse within the surface of the liposome and, therefore, proteins can diffuse to form oligomeric complexes such as homo- or hetero-dimers formation. To compliment the TDA biochemical screen, we are implementing an image based high content screen (HCS) utilizing human umbilical vein endothelial cells (HUVECs) that express native VEGFR-2. The HCS screen is designed to identify potent and specific inhibitors of VEGFR-2 as assessed by a reduction in the proliferation marker Ki67. We are currently (1) validating the TDA assay with known VEGFR-2 inhibitors (2) screening a focus small molecule library to identify novel hits (3) testing the primary hits against a kinase selectivity panel and (4) designing and developing a VEGFR2 cell-based HCS assay to confirm the primary hits. The hit to lead program will be guided by using both physiologically relevant biochemical-based and cell-based assays. The combination of our novel TDA screening platform and the HCS assay technology permits us to identify unique VEGFR-2 inhibitors. Citation Format: Kelvin Lam, Edward Esposito, Deanna Navaroli, Ryan Clinton, Kerrin Beovich, Norman Garceau. Novel TDA technology and high content imaging as complementary assay platforms to identify VEGFR-2 inhibitors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4544. doi:10.1158/1538-7445.AM2013-4544