3177 - Targeting CD244 Enhances Radiotherapy Response through Modulation of Tumor Immune Microenvironment
Presenter(s)
J. Zhou1, L. Feng2, W. Wen3, Y. Xu4, J. Yu5, and D. Chen5; 1Department of Radiation Oncology and Shandong Provincial Key Laboratory of Radiation Oncology, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, 2Shandong Cancer Hospital and Institute, Jinan, China/Shandong, China, 3Department of Radiation Oncology and Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, 4Shandong Cancer Hospital and Institute, Jinan, Shandong, China, 5Department of Radiation Oncology and Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
Purpose/Objective(s):
To investigate the impact of CD244 on tumor immune microenvironment (TIME) after radiotherapy (RT) and the potential combination strategy of targeting CD244 and RT in cancer therapy. We hypothesize CD244 deletion/blockade will affect TIME remodeling and enhance RT response.Materials/Methods:
1*106 MC38 cells were subcutaneously engrafted in wild type (WT) and CD244–/– mice on C57BL/6 background. Single fraction RT of 15 Gy dose treatment was applied when tumor volume was ~150mm3. Single-cell suspensions were prepared from tumors and forwarded to fluorescence-activated cell sorting (FACS) analysis. Tumor infiltrating CD45+ cells were sorted for single-cell RNA sequencing (scRNA-seq) on day 10 after RT. WT mice were treated with 2.5 mg/kg isotype control or anti-CD244 monoclonal antibody (mAb) on day 4, 7 ,10 and 13 after RT. In CD8+ T cell-specific depletion experiments, tumor bearing mice also received 10 mg/kg anti-CD8 mAb on day -1, 2, 6, 9 after RT.Results:
FACS data showed dynamic tumor-infiltrating immune cells and heterogenous expression of CD244 on myeloid cells and T cells after RT. The number of M-MDSCs and PMN-MDSCs in the RT group increased obviously on day 4 after RT. CD244 expression on M-MDSCs decreased while PMN-MDSCs increased. CD244 expression on CD8+ T cells decreased on day 4 while increased on day 10, illustrating TIME shifting toward an exhausted state. CD244 deletion significantly delayed MC38 tumor growth. scRNA-seq data showed increased infiltrating monocytes and macrophages (Mono-Mac) in CD244–/– mice. Exhausted CD8+ T cells were affected obviously by CD244 deletion, especially Tex2 subsets with strong cytotoxicity. FACS analysis confirmed the increased infiltration of M-MDSC, and the high secretion of IFN-? and TNF-a from CD8+ T cells in CD244–/– mice. CD244 deletion had synergistic anti-cancer effects with RT. scRNA-seq data showed increased tumor-infiltrating Mo-Macro and Tex2 cells in CD244–/– + RT group compared to WT + RT group. FACS analysis verified increased CD8+ T cells with high IFN-? and TNF-a in CD244–/– + RT group. Anti-CD8 mAb treatment alleviated the effects of CD244 deletion to RT sensitivity, demonstrating the roles of CD8+ T cells in synergistic effect. Aniti-CD244 mAb treatment also showed anti-tumor effects in MC38 bearing WT mice and potentiated sensitivity to RT. FACS analysis showed decreased myeloid cells and increased CD8+ T cells in anti-CD244 + RT group, compared to RT group. The CD244 expression on CD8+ T cells decreased obviously after anti-CD244 mAb treatment. Anti-CD8 mAb also abrogated the synergistic anti-tumor effects of CD244 blockade with RT.Conclusion:
Radiotherapy induces dynamic CD244 expression: subsequent upregulation on CD8+ T cells correlates with T cell exhaustion. High CD244 plays immunosuppressive roles in anti-cancer immune response in TIME. CD244 deletion/blockade represents a method to remodel TIME and is a promising strategy to promote RT response in anti-cancer therapy.