Engineering TAG72-CAR T cells as a therapeutic strategy in the hen - a spontaneous, preclinical model for ovarian cancer

Abstract Ovarian cancer (OvCa) is the fifth leading cause of cancer-related deaths among women and in the metastatic setting has only an 18% 5-year survival, illustrating the need for new therapeutic strategies to effectively treat the disease. Approximately 90% of epithelial ovarian cancers express tumor-associated glycoprotein 72 (TAG72), thus making it an effective target for the development of chimeric antigen receptor (CAR)-engineered T cell therapies. Our previous studies have demonstrated efficacy of TAG72-CAR T cells in reducing tumor growth and improving survival using in vivo human tumor xenograft mouse models; however, these models are limited in their ability to capture the effects of the immune system and the tumor microenvironment on the impact of CAR T cell therapy. Thus, we have established a novel spontaneous OvCa model using the hen to preclinically evaluate our TAG72-CAR T cell therapy. Hens are one of the only spontaneous preclinical animal models for OvCa, because naturally occurring chicken ovarian tumors pathologically resemble and behave similar to human ovarian tumors. However, to date, the use of the hen as a preclinical model has been directed towards prevention strategies versus targeted therapies for the disease. In this study, we designed and tested a chicken TAG72-CAR construct in an epHIV7 lentivirus backbone under the EF1a promoter that contains all the major CAR domains specific to chickens for the transduction of chicken peripheral blood mononuclear cells. After optimizing the production of CAR T cells, we further characterized their effector function by investigating various cell surface markers, targeted-killing capabilities, and activation/exhaustion marker expression. We observed a greater killing capacity within a 24-hour exposure period to ovarian cancer cells, such as human immortalized ovarian tumor cells (OVCAR3), displaying the target antigen compared to the later time exposures of 48 hours and/or 72 hours. The activation and exhaustion surface markers analyzed throughout the experiments support the high killing capacities earlier in exposure, with elevated activation and exhaustion occurring at later time points. In this study, chicken TAG72-CAR T cells were successfully generated, characterized, and tested as a therapeutic approach for treating OvCa in the hen, and will be further used to evaluate their in vivo efficacy in the hen model. The ability to test therapeutic strategies in an in vivo model that biologically and physiologically parallels the disease in women allows for the improvement of OvCa diagnosis and prognosis. Citation Format: Emily L. Cauble, Eric Lee, Cody Cullen, Saul J. Priceman, Lorna R. Rodriguez, Lindsey S. Treviño. Engineering TAG72-CAR T cells as a therapeutic strategy in the hen - a spontaneous, preclinical model for ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1792.