Abstract 4565: Forced expression of GITRL in cancer cells enhances adenovirus-mediated in situ vaccination

Abstract

Abstract Our approach involves a platform of killing cancer using more potent oncolytic viruses-based immunotherapy strategies. These replication competent adenoviruses are targeted to the Rb pathway to generate tumor-selectivity. The second generation of these therapeutic agents, Delta-24-RGD, was successfully translated to the clinical setting and is currently been tested in Phase I studies in several institutions in the USA and in Europe for the treatment of patients suffering from recurrent gliomas. Preliminary data from these clinical trials showed that 10 to 15% of Delta-24-RGD-treated tumors undergo complete regression. Agonistic treatments targeting co-stimulatory tumor necrosis factor receptor superfamily (TNFRSF), such as GITR (CD357), have been shown to enhance the proliferation and activation of T cells. Moreover, in preclinical tumor efficacy studies, these agonistic signals have shown potent tumoricidal activity. Different from antibodies, co-stimulatory ligands can be easily incorporated into replication competent oncolytic adenoviruses. Infection of cancer cells with these armed viruses will lead to the expression in their cell membranes of the co-stimulatory molecule that will directly interact with the tumor infiltrating lymphocytes to amplify and enhance the anti-tumor T-cell activity. In this study, we have developed an armed Delta-24-RGD carrying the cDNA of the mouse GITRL, Delta-24-GREAT. Treatment of glioma-bearing mice with intracranial injection of Delta-24-GREAT increased mice survival (P < 0.0001, long-rank test) and inhibited lung cancer growth in subcutaneous models. Infection of the tumor elicited an inflammatory response increasing the populations of CD4+ and CD8+ T cells versus treated controls. Importantly, 2 weeks after the adenovirus treatment a subset of brain hemispheric cells were positive for GITRL. In addition, co-culture experiments with tumor cells infected with viruses and splenocytes isolated from treated glioma-bearing mice demonstrated a response against the cancer cells as assessed by ELISA analyses of IFN-γ. Demonstrating the generation of anti-tumor memory, the surviving animals did not show evidence of tumor growth after re-challenging with GL261 glioma cell implantation in the contralateral hemisphere. However, survivors of GL261 tumors did not survive after the re-challenge was performed by intracranial implantation of B16/F10 melanoma cells, strongly indicating that the immune response was specific for GL261 glioma antigens. This is the first study with an oncolytic adenovirus expressing GITRL and our results strongly indicate that oncolytic adenoviruses armed with molecules of the TNFRSF may be of future clinical interest for the treatment of patients with cancer. Citation Format: Yisel A. Rivera-Molina, Francisco Puerta Martinez, Teresa Nguyen, Hong Jiang, Xuejun Fan, Rehnuma Shifat, Mohammad Belayat Hossain, Verlene K. Henry, Caroline C. Carrillo, Candelaria Gomez-Manzano, Juan Fueyo. Forced expression of GITRL in cancer cells enhances adenovirus-mediated in situ vaccination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4565. doi:10.1158/1538-7445.AM2017-4565