Abstract 1596: Human choriocarcinomas: Placental growth factor-dependent preclinical tumor models

Abstract Choriocarcinomas are an aggressive form of cancer that develops in the uterus from tissue that would normally become the placenta. Choriocarcinomas are a trophoblastic gestational disease and the tumors are highly angiogenic. Human placental growth factor (hPlGF) is an angiogenic growth factor that promotes the growth of blood vessels in the placenta. hPlGF levels can be higher under pathological conditions such as cancer. Some human tumor specimens have higher PlGF levels than normal tissue, thus hPlGF is a target for anti-angiogenic therapy. The human choriocarcinoma cell lines BeWo, JAr, and JEG-3 were evaluated as preclinical models of hPlGF overexpression. The levels of hVEGF-A and hPlGF secreted by the choriocarcinomas and 11 human and mouse cancer cell lines in culture were measured by ELISA. The choriocarcinomas secreted higher levels of hPlGF and lower levels of hVEGF-A than 10/11 other cancer cell lines. The hPlGF serum levels in mice bearing subcutaneous choriocarcinoma tumors correlated with tumor volume and reached >2,000 pg/ml. By comparison, no hPlGF was detected in the serum of mice bearing H460 non-small lung carcinoma, HT29 colon carcinoma or MOLM-13 acute myeloid leukemia xenograft tumors. Although choriocarcinoma cells secreted both hPlGF and hVEGF-A in culture, serum levels of hVEGF-A in mice bearing choriocarcinoma xenografts were undetectable or <50 pg/ml at the time points serum was collected indicating that angiogenic factor secretion by the cells in culture was not the same in vivo. JEG-3 tumors grew faster than JAr tumors following the subcutaneous implantantion of 1×106 cells into nude mice. BeWo tumors grew the slowest and had the highest serum PlGF levels. Immunohistochemical methods confirmed expression of hPlGF in the choriocarcinoma xenografts. Studies involving double immunofluorescence on the xenograft tumors are ongoing to investigate endothelial cell and pericyte interactions and stromal involvement in the tumors. sFLT01, a novel fusion protein that neutralizes PlGF and VEGF-A, was added to choriocarcinoma cells in culture and administered to mice bearing choriocarcinoma xenografts in efficacy studies. Exposure of JAr and JEG-3 cells in culture to sFLT01 resulted in a phenotypic change whereby the cells produced less hPlGF and no significant hVEGF-A. In vivo, sFLT01 (25 mg/kg, IP injection, 2x per week) slowed tumor growth in JAr and JEG-3 tumors and increased median survival by 5-30 days compared to vehicle controls. These results indicate that human choriocarcinoma xenograft models are a valuable research tool for evaluating anti-angiogenic agents that target hPlGF. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1596. doi:10.1158/1538-7445.AM2011-1596