Abstract Tumor reactive (TR) CD8 T cells in the liver have been studied in the setting of both immunotherapy and cellular therapy with the predominant dogma that these cells have equivalent functionality in the liver as compared to other organ sites. Herein, we detail that TR+ CD8 T cells are functionally impaired in the liver immune microenvironment in mice with liver tumors.TR+ CD8 T cells were studied in BALB/c and C57BL/6 mice injected intrahepatic, intravenous, and subcutaneously with either a colon (CT26) or a melanoma (B16F10) cancer cell line to create intrahepatic, pulmonary and subcutaneous tumors, respectively. Additionally, an ⍺CD8 antibody with IgG control was used to conduct functional studies. Samples were analyzed using flow cytometry and liver weights were measured. A high frequency of TR+ CD8 T cells were found in the liver in mice with intrahepatic tumors. Despite ~70% of CD8 T cells being tumor reactive in intrahepatic tumors, liver tumor growth kinetics were faster than subcutaneous tumors. Higher proportion of the TR+ CD8 T cells were found to be exhausted in the liver tumor by flow cytometry. Functional depletion of the CD8 T cells caused a fivefold higher tumor growth in the subcutaneous model but in contrast had no effect on intrahepatic tumors. In conclusion, despite the high frequency of “killer” tumor reactive T cells in the liver, the growth kinetics of the liver tumors, flow cytometry as well as functional studies demonstrate the impairment of TR+ CD8 T cells in the liver. We aim to dissect the mechanisms mediating intrahepatic TR CD8+ T cell exhaustion in primary liver tumors as well as metastatic models. Additionally, we aim to determine significant costimulatory molecules specific to intrahepatic exhaustion which could lead to better therapeutic models. Citation Format: Rajiv S. Trehan, Marlaine Soliman, Xin Wang, Patrick Huang, Noemi Kedei, Xiao Bin Zhu, Matthias Seifert, Mohamed-Reda Benmebarek, Amran Nur, Firouzeh Korangy, Chi Ma, Tim F. Greten. Impairment of tumor reactive CD8 T cells in liver cancer [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(6_Suppl):Abstract nr 3970.

Functional tumor-specific CD8+ T cells are essential for an effective anti-tumor immune response and the efficacy of immune checkpoint inhibitor therapy. In comparison to other organ sites, we found higher numbers of tumor-specific CD8+ T cells in primary, metastatic liver tumors in murine tumor models. Despite their abundance, CD8+ T cells in the liver displayed an exhausted phenotype. Depletion of CD8+ T cells showed that liver tumor-reactive CD8+ T failed to control liver tumors but was effective against subcutaneous tumors. Similarly, analysis of single-cell RNA sequencing data from patients showed a higher frequency of exhausted tumor-reactive CD8+ T cells in liver metastasis compared to paired primary colon cancer. High-dimensional, multi-omic analysis combining proteomic CODEX and scRNA-seq data revealed enriched interaction of SPP1+ macrophages and CD8+ tumor-reactive T cells in profibrotic, alpha-SMA rich regions in the liver. Liver tumors grew less in Spp1-/- mice and the tumor-specific CD8+ T cells were less exhausted. Differential pseudotime trajectory inference analysis revealed extrahepatic signaling promoting an intermediate cell (IC) population in the liver, characterized by co-expression of VISG4, CSF1R, CD163, TGF-βR, IL-6R, SPP1. scRNA-seq of a third data set of premetastatic adenocarcinoma showed that enrichment of this population may predict liver metastasis. Our data suggests a mechanism by which extrahepatic tumors facilitate the formation of liver metastasis by promoting an IC population inhibiting tumor-reactive CD8+ T cell function.