2935 - Anti-Tumor Responses of Icaritin Combined Radiotherapy Treatment and Its Immune Mechanisms

M. Cao^1,2, Z. Wang^1,3, D. Hu^1,3, B. Xiang^1,3, X. Wang^1,3, Y. Wang¹, W. Liao¹, S. Zhang¹, J. Lang¹, and Y. Zhao¹; ¹Department of Radiation Oncology, Sichuan Cancer Hospital & Institute, Sichuan Cancer Center; Cancer Hospital affiliate to University of Electronic Science and Technology of China, Chengdu, China, ²Chengdu University of Traditional Chinese Medicine, Chengdu, China, ³School of Medicine, University of Electronic Science and Technology of China, Chengdu, China

Purpose/Objective(s): Radiotherapy played pivotal roles in curing cancer itself as well as shaping tumor immune microenvironment. Recent studies have been focused on combined strategies to magnify tumor control with local radiotherapy. Icaritin is a prenylflavonoid derivative from plants of the Epimedium genus, recently been implicated as a novel immune-modulator in cancer treatment. Here we investigated the anti-tumor potential of icaritin combined radiotherapy and its immune mechanisms. Materials/

Methods: Mice were inoculated with MC38 (murine colon adenocarcinoma) or LLC (murine lung adenocarcinoma) cell line and treated with radiotherapy (6 Gy × 3) and icaritin (intraperitoneal, 200mg, qd) to evaluate anti-tumor responses in vivo. Tumor volume and mice survival were compared in each group (control, RT, icaritin and RT + icaritin). Tumor infiltrating immune cells were analyzed by flowcytometry and RNA-seq. Cell viability were used to evaluated tumor growth inhibition in vitro with a cell counting kit among groups (control, RT, icaritin and RT + icaritin).
Results: RT combined with icaritin significantly dampened tumor growth and prolonged animal survival in MC38 and LLC model (p < 0.001). Mechanistically, RT combined with icaritin decreased both MC38 and LLC cell viability in vitro, and orchestrated tumor immune microenvironmental changes in vivo. The number of CD8+ T cells, especially cytotoxic IFN?⁺CD8⁺ were significantly increased both in peripheral blood and tumor. Besides, the expression level of PD-L1 and CD40 were upregulated in dendritic cells in combined treatment group (CD11b⁺CD11c⁺MHCII⁺). GO analysis of the infiltrated immune cells RNA sequencing indicated the activation of apoptosis, ROS signaling in combined treatment group. Tumor growth was restored after aCD8, aGr-1 depletion in combined treatment group, highlighting the roles of cytotoxic T lymphocytes and dendritic cells in this process.
Conclusion: RT combined with icaritin ignite anti-tumor immunity through promoting IFN?⁺CD8⁺ cytotoxic T lymphocytes and antigen presenting function in dendritic cells. Combined therapy may have potential for enhanced tumor control in clinics.