Abstract B018: CCL24+ monocytes drives resistance to anti-PD-L1 blockade in hepatocellular carcinoma

Abstract Background: Immunotherapy has promising anti-tumor activity in patients with advanced Hepatocellular carcinoma (HCC). However, the objective response rate of PD-L1 blockade is limited. Therefore, there is an urgent need to explore resistance mechanisms in immunotherapy. Methods and Results: We used the anti-PD-L1 resistant trp53KO/c-mycOE mice to explore tumor immune microenvironment. Fresh isolated single cells were analysed by single-cell RNA sequencing (scRNA seq), TCR sequencing and Cytometry by Time-Of-Flight (CyTOF). Gene expression of the tumors samples was tested by bulk RNA sequencing. In vivo efficacy studies were executed in trp53KO/c-mycOE mice induced by hydrodynamic tail vein injection. The function of immune cells was evaluated by multiple flow cytometry. Results: We found although anti-PD-L1 treatment significantly improved T cells infiltration and TCR clonal expansion. These T cells exhibited highly exhausted status with highly exhausted markers (CD39, LAG3, PD-1) expression. Targeting the exhausted markers by specific antibodies cannot unleash the function of T cells, which suggested the persistent immunosuppressive microenvironment existed. Bulk RNA sequencing showed significantly activation of IFNG related pathway. scRNA seq exhibited increased monocytes ratio and the IFNG score prominently upregulated in monocytes after anti- PD-L1 treatment. Subclusters analysis showed that CCL24+ monocytes were increased remarkably after treatment. CCL24+ monocytes showed significant response to IFNG and these cells also significantly expressed IL10, VEGFA, ARG1 etc. Conclusion: Our data demonstrated anti-PD-L1 blockade induced IFNG related pathways and increased the CCL24+ monocytes infiltration. These cells maybe the potential targets mediating the resistant mechanisms for immunotherapy. Further exploration could facilitate the development of new combination therapies that synergistically enhance treatment efficacy for patients with HCC. Citation Format: HAIJING DENG, Grace Fu-Wan Sit, Jacinth Wing-Sum Cheu, Yan Zhang, Cindy Xinqi Liu, Yiling Chen, Zher Yee Ooi, Vincent Wai-Hin Yuen, Irene Oi-Lin Ng, Carmen Chak-Lui Wong. CCL24+ monocytes drives resistance to anti-PD-L1 blockade in hepatocellular carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr B018.