Abstract 2514: Activity of a novel Foxp3-tumor cell vaccine in a murine model of renal cell carcinoma

Abstract

Abstract Renal cell carcinoma (RCC) is the most common type of kidney cancer in adults and represents 80% of the cases. Treatment options for patients with advanced disease are limited. Targeted molecular therapies have shown survival benefit but most patients develop therapy resistance overtime. Preclinical and clinical studies indicate that immunotherapies are effective and may play a role in the treatment of advanced RCC. However, the response rate is ∼ 20%, with a limited number of patients achieving durable remission. A major barrier to vaccine therapy is the presence of immunosuppressive cell populations including regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs). In the current study, we designed a tumor cell and Tregs dual-targeting vaccine by inducing Foxp3 expression in tumor cells, and tested this vaccine along with an unmodified vaccine in an orthotopic murine model of RCC, RENCA. We observed that both RENCA cell vaccine and RENCA Foxp3 cell vaccine prevented tumor growth in 6 out 10 animals. Interestingly, in an intervention setting, the RENCA Foxp3 tumor cell vaccine was superior to the RENCA tumor cell vaccine with a significant anti-tumor activity (45% inhibition of tumor weights) (p<0.01). Moreover, RENCA Foxp3 tumor cell vaccine reduced the number of tumor infiltrating Tregs (42% reduction, p<0.05) and Treg Foxp3 expression both in peripheral blood and tumor infiltrates. In summary, our results suggest that a strategy targeting Tregs along with vaccine therapy or a dual targeting vaccine strategy may be beneficial in established RCC. We also observed that suppressive myeloid cell (SMCs) populations dominate the established tumor microenvironment and we are currently testing the combination of the dual-targeting vaccine with a SMC-targeting agent. Citation Format: Li Shen, Ashley Orillion, Remi Adelaiye, Eric Ciamporcero, Swathi Ramakrishnan, Roberto Pili. Activity of a novel Foxp3-tumor cell vaccine in a murine model of renal cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2514. doi:10.1158/1538-7445.AM2015-2514