Abstract B50: A novel immunocompetent murine model for replicating oncolytic adenoviral therapy

Oncolytic adenoviruses are able to replicate selectively in cancerous but not normal human cells and are under investigation as potential cancer therapeutics. Unfortunately, mice are poor model systems for therapy with replication competent adenoviruses because murine cells are generally unable to produce infectious viral progeny. In order to model oncolytic adenovirus treatment, researchers have used human tumor xenografts that support viral replication in immunodeficient mice. Because xenografts require an immunodeficient host, xenograft model systems do not reflect a host9s adaptive immune response against the virus and cannot model the potential for an immunostimulatory virus to induce an anti-tumor immune response. Using the tumor-selective oncolytic adenovirus TAV-255 previously developed in our laboratory, we find that the murine lung adenocarcinoma cell line LKR-13 supports adenoviral infection and generates infectious viral progeny. Western blotting showed that LKR-13 cells express the coxsackie and adenovirus receptor (CAR) to allow viral infection, and that infected cells express the viral protein E1A. MTT assays, crystal violet staining, and clonogenic assays showed that TAV-255 kills LKR-13 cells in a dose-dependent and time-dependent manner with similar potency and latency of infection as a panel of human cancer cell lines, with more than 50% cell death of murine LKR-13 cells and various human cancer cells (T1, 882 and A549) within 6 days of infection at a multiplicity of infection of 10. It produces infectious progeny from LKR-13 cells at titres similar to other human cancer cell lines. Other tested murine cancer cell lines do not share these features; for example, the CT-26 colon cancer cell line does not express CAR and is resistant TAV-255 infection, while the murine sarcoma cell line F244 is readily infected by adenovirus and produces the viral protein E1A but does not produce infectious progeny. Based on these in-vitro findings, we investigated LKR-13 cells as an in-vivo model system for replicating oncolytic adenoviruses. The LKR-13 cell line is derived from 129/Sv mice, and using fully immunocompetent 129/s4 mice, subcutaneous injection of 5x106 LKR-13 cells led to tumor formation in all injected mice. Intratumoral injection of 3x107 plaque forming units of TAV-255 in established tumors (greater than 200 mm3) caused a significant reduction in tumor growth: Eight days after treatment, tumors in mice treated with TAV-255 were 339 mm3 +/- 26 mm3 (n=3), and tumors in mice treated with PBS were 578 mm3 +/- 49 mm3 (n=5) (p=0.013). This model system represents the first fully immunocompetent mouse model for cancer treatment with replicating oncolytic adenoviruses, and will be useful to study the therapeutic effect of oncolytic adenoviruses in general and particularly immunostimulatory viruses designed to evoke an anti-tumor immune response. Citation Format: Lingzhi Zhang, Farah Hedjran, Christopher Larson, Min Yan, Tony Reid. A novel immunocompetent murine model for replicating oncolytic adenoviral therapy. [abstract]. In: Proceedings of the AACR Special Conference: The Translational Impact of Model Organisms in Cancer; Nov 5-8, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(11 Suppl):Abstract nr B50.