Abstract 5293: In vitro modeling of tumor-derived endothelial cell derivation
Authors: Elster Jennifer D. , McGuire Terence F. , Prochownik Edward V. 
Published: August 2012

Abstract
Background: Tumor growth beyond a few millimeters in size requires the development of a neovasculature. In addition to providing a portal for the systemic dissemination of metastatic cells, this allows the tumor bed to overcome the severe hypoxia, acidosis, and nutrient deprivation that otherwise limits tumor growth. Early research presumed the development of genetically and functionally normal tumor vasculature from normal host tissue. Anti-angiogenic agents were thus developed to inhibit tumor blood supply with the hope that the presumed normal tumor vascular endothelial cells (EC's), would be less inclined to develop drug resistance. Thus far, however, the experience with these agents has been one of only incremental improvement in patient survival. We have previously demonstrated that tumor cells can differentiate, in vivo, into an EC phenotype and form functional tumor vasculature. Formation of these “tumor derived endothelial cells” (TDEC's) offers a partial explanation for the disappointing clinical results of the angiogenesis inhibitors and suggests a new, complementary, therapeutic target. Objectives: To develop an in vitro system that would recapitulate the tumor cell to EC transition seen in vivo. We hypothesize that manipulation of culture conditions to mimic the tumor microenvironment would result in a switch to an EC phenotype. Design/Methods: A variety of human cancer cell lines (H460 lung cancer, PC3 prostate cancer, OVCAR-8 ovarian cancer) were cultured in 1% O2 in low glucose DMEM supplemented with EC-specific growth factors. The cells were assayed for EC-specific proteins and transcripts with western blotting, immunofluorescence, flow cytometry, and rtPCR. Functionality was quantified by the uptake of acetylated-LDL and the ability to vascularize tumor xenografts. Results: Human cancer cell lines exposed to hypoxia and EC-specific growth factors increase expression of a variety of EC-specific proteins including von Willebrand's factor, ESAM, and VE-Cadherin, while down regulating the epithelial specific cytokeratins. Inclusion of a twenty percent minority of these in vitro-derived TDEC's in a tumor inoculum results in an increase in both tumor growth rate and vascular density. These in vitro-derived TDEC's are also found within the tumor neo-vasculature. Conclusions: We have developed culture conditions that can, within a span of only five days, induce many of the same phenotypic and functional characteristics of the TDEC's isolated from tumor xenografts grown for nearly two months. Furthermore, these cells are able to act as functional endothelial cells in vivo. Potential uses for this system include the ability to study the mechanistic underpinnings of the tumor cell to TDEC transition and to identify pharmacologic inhibitors of this transition.
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 5293. doi:1538-7445.AM2012-5293