Abstract 2335: API 31510 - a novel anti-angiogenic modulator of endothelial cells and the tumor microenvironment
Authors: Walshe Tony E. , Bourdelais Justin J. , Vishnudas Vivek , Sarangarajan Rangaprasad , Narain Niven R. 
Published: August 2012

Abstract
Progression of tumor size greater than 2-5mm in size requires induction of angiogenesis to supply the tumor with oxygen and nutrients. Angiogenesis occurs due to intra-tumoral cell release of endothelial mitogenic factors in response to hypoxia or genetic mutation. There are currently numerous endogenous proteins in clinical development as therapeutic anti-angiogenesis targets e.g. VEGF and PlGF. Herein, we have investigated a novel anti-angiogenic agent API 31510 currently subject of late stage clinical trials in skin cancers and a Phase I for solid tumors. Human umbilical vein endothelial cell (HUVEC) fate decisions that modulate the angiogenic phenotype were examined in the presence of 100 µM or 1500 µM 31510 or excipient and compared to untreated control cells. Endothelial cell fate assays for apoptosis, proliferation, migration and 3-D tube formation within matrigel were performed. Morphological & flow cytometric analysis of annexin V/propidium iodide positive cells revealed an increase in HUVEC apoptosis in the presence of 1500 µM 31510, compared to excipient or control cells. Concomitant with increased cell death due to 31510, HUVEC cell counts were significantly decreased in the presence of 1500 µM 31510. To assess the potential effects of 31510 on endothelial migration, we examined HUVEC migration 5 hours post-wound generation, in an endothelial scratch assay. Both 31510 and excipient significantly impaired HUVEC migration at both 100 and 1500 µM concentration, demonstrating anti-migratory activity of both the excipient and 31510. In order to determine if the 31510 anti-tumor activity is due to effects on endothelial sprouting angiogenesis, we examined endothelial tube formation in 3-D matrigel cultures over time. Addition of 1500 µM excipient in both the gel and overlying media impaired tube formation compared to control. Moreover, addition of 1500 µM 31510 further impaired HUVEC tube formation compared to both excipient and control untreated cells. These effects were noted as early as 24 hours after seeding and up to 96 hours in culture. Moreover, histological analyses from excised tumors from pre-clinical animal models in melanoma, SCC, liver cancer, and pancreatic cancer confirm a hallmark downregulation in angiogenic signaling and infrastructure. Anti-tumor activity of 31510 is likely due, at least is part, to inhibition of tumor recruitment of local blood supply for neo-vessel formation. Taken together, these studies reveal that 31510 alters endothelial migration, proliferation, apoptosis and tube formation. These studies strongly support a role for API 31510 as a novel anti-angiogenic agent that limits the angiogenic capacity of endothelial cells while modulating tumor angiogenesis.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2335. doi:1538-7445.AM2012-2335