Abstract 598: EMT and nectin-1 mediate sensitivity to HSV-1 oncolysis in human HCC cell lines

Abstract

Abstract Background: Oncolytic viral therapy mediated by herpes simplex virus 1 (HSV-1) is an emerging and promising cancer therapy. The entry of HSV-1 into cells is mediated in part by cell surface co-receptors. One of these co-receptors, nectin-1, is highly expressed in epithelial cells. Nectin-1 is localized to adherens junctions (AJs) where it interacts with E-cadherin through their respective peripheral membrane proteins, afadin and catenin. The loss of E-cadherin is a hallmark of epithelial-to-mesenchymal transition (EMT) and results in the disassembly of AJs. Here, we investigate the effects of EMT on cell surface nectin-1 expression, HSV infection and viral oncolysis. Methods: Western blot analysis was performed to determine E-cadherin expression in human HCC cell lines. Cytotoxicity to HSV-1 KOS strain was assessed by MTT analysis. KOS replication was assessed by a single-step burst assay, while viral infectivity was examined using the mutant bM24-BAC#3 virus which encodes GFP. Cell surface levels of nectin-1 and herpesvirus entry mediator (HVEM) were determined by flow cytometry and the role of nectin-1 in HSV-1 infectivity was further assessed using a nectin-1 neutralizing antibody. Results: Four of the human HCC cell lines were epithelial and four were mesenchymal. KOS oncolysis resulted in 50% cell death in the epithelial cell lines at multiplicities of infection (MOIs) 2-3 log orders less than the mesenchymal HCC cell lines. This difference was not attributed to cell growth rates as determined by population doubling times or to viral replication as assessed by burst assay. Instead, the epithelial cell lines had higher rates of infectivity which were attributed to greater cell surface expression of nectin-1 and not HVEM. Finally, blocking of nectin-1 with a neutralizing antibody inhibited viral oncolysis in all four epithelial HCC cell lines. Conclusions: EMT in human HCC cells results in the loss of nectin-1 cell surface expression and resistance to HSV-1 oncolysis. E-cadherin and nectin-1 are markers of sensitivity to HSV-1 oncolysis in human HCC cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 598.