Susceptibility of head and neck cancer to an attenuated model of the oncolytic vesicular stomatitis virus expressing suicide genes

Abstract

e14604 Background: The predominant loco-regional progression of head and neck squamous cell carcinoma (HNSCC) makes it suitable for testing oncolytic viruses. Recent work from several laboratories including ours has focused on developing vesicular stomatitis virus (VSV) as a replication-competent anticancer viral vector. Attenuated strains, such as M protein mutant VSV (M51R) are more likely to be promoted in clinical research. The major shortcoming of viral therapy is related to the large proportion of tumor cells remaining uninfected. We are addressing this limitation in two ways: the expression of the cytosine deaminase-uracil phosphoribosyltransferase (C:U) suicide gene by the rVSV vector, expected to produce a strong bystander effect and the exploitation of the radiosensitizing potential of the 5-FU chemo-drug produced intratumorally, as well as of the VSV virus itself. Methods: We determined the extent of defectiveness in interferon pathways and susceptibility to oncolytic VSV in a collection of HNSCC cell lines and in patient HN primary tumor cells. We employed gene array to screen for differences in gene expression in sensitive and resistant models. We have generated the rVSV-C:U and M51R-C:U viruses and we tested our collection of HNSCC cell models to infection with these viruses in the presence and absence of 5-FC. In vivo experiments were performed on a localized and on a metastatic SQ-20B model of HNSCC in nude mice. Results: 1) the primary patient HNC cells are more resistant than the HNC cell lines to the M51R-VSV; 2) the activation of IFN pathways and /or alterations of AKT pathway is contributing to resistance to VSVs. 3) Addition of the suicide gene to the attenuated VSV provided significantly more oncolytic effect in vitro and in vivo. The efficacy and the radiosensitizing potential of M51R- C:U on a nude mice model of HNSCC (SQ-20B) will be presented. Conclusions: M51R-VSV has increased efficiency and radiosensitizing effect on HNSCC models. We can define an optimal approach to testing VSV vectors for treatment of HNSCC, with a clinical trial in HNSCC patients as our next goal. Finally, we have important new information, both from cell lines and patient tissues, for proof-of-principle that cancers can down-regulate antiviral responses. No significant financial relationships to disclose.