Abstract 2660: CXCL9/10 is critical for immunotherapeutic efficacy by recruiting and activating T lymphocytes in tumor microenvironment

Abstract Background: Tumor immunotherapies targeting PD- (L) 1 exhibit anti-tumor efficacy in only about 20% of patients with a variety of cancers. Literature has demonstrated that “hot tumor” which contains high T lymphocytes in tumor microenvironment exhibits a better response to immunotherapies than “cold tumor”. Therefore, we hypothesize that T lymphocyte-recruited factors play the roles determining the immunotherapeutic efficacy, including CXCL9, 10, and 11, which are located in human chromosome 4 with consistent co-expression and protein structure. Aims: The aim of this study is to investigate whether CXCL9/10 is critical in determining the anti-PD- (L) 1 immunotherapeutic efficacy. Methods: GEPIA, cBioPortal, and Kaplan-Meier Plotter were used to investigate the gene expression, co-expression, and immunotherapeutic association for CD274 (PD-L1), ICAM1, and CXCL9/10 in lung, colon, and liver cancers. qPCR and flow cytometry were used to detect the gene expression in tumor cells and T lymphocytes, particularly comparing the differences between LL/2 and CT26 cells whereas LL/2 is immunotherapy-resistant and CT26 is immunotherapy-sensitive. CD8+ T cell transwell assay and qPCR were used to measure the function of CXCL10 on CD8+ T cell migration and activation, whereas IFNγ and IL-2 as the activation markers. Results: We found that CXCL9/10 overexpressed in a variety of tumors, including lung, colon, and liver tumors with a correlation with PD-L1. However, PD-L1 was not overexpressed in most tumors. High PD-L1 and CXCL10 are basically associated with better survival rates in tumor patients receiving immunotherapies. Correlation analysis revealed that IRF-1 and STAT1 were correlated with PD-L1 and CXCL10 expression in lung cancer. Since literature has indicated that LL/2-derived syngeneic tumor exhibits immunotherapy-resistant and CT26 exhibits immunotherapy-sensitive, we further compared the gene expression between them. We found that IFNA, IFNG, CXCL10, and PD-L1 all expressed higher levels in CT26 cells than LL/2. Moreover, we found that T lymphocytes specifically expressed high CXCR3, a receptor of CXCL9/10, including CD4+ T and CD8+ T cells by flow cytometry. As expected, CD8+ T cells can be recruited in a transwell assay by IFNα and CXCL9. In addition, we found that IFNα induced CXCL10 expression in monocytes and CXCL10 increased activation markers IFNγ and IL-2 in CD4+ T and CD8+ T cells. Conclusions: This study revealed that CXCL9/10 expression is correlated with PD-L1 in tumors, resulting in better immunotherapeutic efficacy. The evidence demonstrated that CT26 intrinsically exhibited higher IFNs and CXCL9/10 compared to LL/2. Therefore, CXCL9/10 potentially recruits and activates CD8+ T cells to tumor microenvironment, transferring “cold tumor” to “hot tumor”. This study indicates that CXCL9/10 is critical for immunotherapeutic efficacy. Citation Format: Chun-Chia Cheng, Jungshan Chang, Zong-Lin Sie, Ai-Sheng Ho, Cheng-Liang Peng, Chun-Chao Chang. CXCL9/10 is critical for immunotherapeutic efficacy by recruiting and activating T lymphocytes in tumor microenvironment abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2660.