Abstract 3558: uPAR mediated endothelial targeting by oncolytic measles virus

Abstract

Background: The urokinase receptor (uPAR) is over-expressed in tumor cells as well as in tumor endothelium and plays a critical role in tumor neovascularization. We have recently rescued an oncolytic measles virus fully retargeted against human uPAR (MV-h-uPA). The aim of this study was to further characterize the endothelial targeting capabilities of MV-h-uPA over MV-GFP.

Methods: In vitro cytotoxicity assays were performed in unstimulated and stimulated HUVEC, and the effects of both viruses were analyzed. The effects of MV-GFP and MV-h-uPA on actively forming vs. established capillaries was investigated using the matrigel tube formation assay. Endothelial to tumor transfer of MV-uPA or MV-GFP was investigated in breast, colon cnd kidney cancer cell lines expressing RFP by overlaying infected HUVEC on tumor cell monolayers. The mechanisms/kinetics of viral transfer from HUVEC to tumor cells was characterized. Microvessel density of tumors treated with MV-h-uPA was quantitated by immunohistochemistry using an antibody against CD31.

Results: MV-h-uPA and MV-GFP induced cytotoxicity at 24, 48 and 72 hours in stimulated HUVECs. MV-h-uPA replicated more efficiently in growth factor stimulated, compared to resting HUVECs. Interestingly, MV-h-uPA, but not MV-GFP successfully infected actively forming (angiogenic) HUVEC capillaries, as assessed by mean fluorescence quantification of GFP expression of infected capillaries. On the other hand, the non-targeted MV-GFP predominantly infected already established HUVEC capillaries (infected 24 hours after tubes were formed), an effect not observed with MV-h-uPA. Importantly, MV-h-uPA did not induce vascular disrupting effects in HUVEC capillaries. MV-h-uPA was successfully transferred from infected endothelial cells to tumor cells. This effect was mediated by heterofusion, as chemical inhibition of virus induced fusion at different time points during co-culture completely blocked EC to TC transfer. Heterofusion occurred as early as 4 hours after endothelial cell overlay into tumor cell cultures. EC to TC viral transfer resulted in significant tumor cell cytotoxicity.

Conclusion: The above results demonstrate the improved ability of uPAR retargeted oncolytic measles virus to infect, replicate and successfully infect angiogenic endothelial cells, as well as successful EC to TC transfer in vitro, resulting in tumor cell cytotoxicity. Vascular targeting by oncolytic MVs may result in improved tumor cell delivery in vivo, and enhanced antitumor effects.

Citation Format: Marcela M. Toro Bejarano, Yuqi Jing, Krisztina Kovacs, Jaime Merchan. uPAR mediated endothelial targeting by oncolytic measles virus. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3558. doi:10.1158/1538-7445.AM2015-3558