Abstract
Oncolytic measles virus (MV) induces cell fusion and cytotoxicity in a CD46 dependent manner. Development of fully retargeted oncolytic MVs would improve tumor selectivity. The urokinase receptor (uPAR) is a tumor and stromal target overexpressed in multiple malignancies. MV-H glycoproteins fully retargeted to either human or murine uPAR were engineered and their fusogenic activity was determined. Recombinant human (MV-h-uPA) and murine (MV-m-uPA) uPAR retargeted MVs expressing eGFP were rescued and characterized. Viral expression of chimeric MV-H was demonstrated by RT-PCR and Western Blot. In vitro viral replication was comparable to MV-GFP control. Receptor and species specificity of MV-uPAs were demonstrated in human and murine cells with different levels of uPAR expression. Removal of the ATF ligand from MV-uPA -by Factor Xa treatment- ablated MV-uPA’s functional activity. Cytotoxicity was demonstrated in uPAR expressing human and murine cells. MV-h-uPA efficiently infected human endothelial cells and capillary tubes in vitro. Intravenous administration of MV-h-uPA delayed tumor growth and prolonged survival in the MDA-MB-231 breast cancer xenograft model. Viral tumor targeting was confirmed by immunohistochemistry. MV-m-uPA transduced murine mammary tumors (4T1) in vivo, after intratumor administration. MV-m-uPA targeted murine tumor vasculature after systemic administration, as demonstrated by dual (CD31 and MV-N) staining of tumor capillaries in the MDA-MB-231 model. In conclusion, MV-uPA is a novel oncolytic MV associated with potent and specific antitumor effects and tumor vascular targeting. This is the first retargeted oncolytic MV able to replicate in murine cells and target tumor vasculature in an uPAR dependent manner.
