Abstract 1515: Tertiary lymphoid structures restrain cancer evolution by supporting stem-like CD8+ T cells for sustained anti-tumor immunity

Abstract Currently, our understanding of the mechanism underlying the immune response on extending the survival of patients with aggressive tumors remains limited. In this study, we generated multi-regional genomic and transcriptional data coupled with digital pathology from 28 long-term survivors (LTSs) and 34 stage-matched short-term survivors, with intrahepatic cholangiocarcinoma (iCCA). Our investigation unveiled that mature tertiary lymphoid structures (TLSs) within the tumors of LTSs exerted significant immune pressure on the tumor, leading to the restriction in generating clonal mutations and increased subclonal diversity. Employing single-cell profiling, we identified significant enrichment of IgM+ naïve B cells and TCF7+ stem-like CD8+ T cells in TLS-positive tumors. Spatial profiling further highlighted that TCF7+ stem-like CD8+ T cells preferentially localized in TLS, facilitating reduced vulnerability to unfavorable environmental factors. Functionally, TCF7+ stem-like CD8+ T cells displayed strong capacity to differentiate into effector subsets while maintaining a diverse T-cell receptor repertoire. Mechanistically, we identified that naïve B cells promote activation and differentiation of stem-like CD8+ T cells within the TLS niche through IgM-FcμR axis, which primed these T cells for enhanced anti-tumor immunity. In summary, our findings underscore that TLS plays a pivotal role in orchestrating enduring and effective anti-tumor immunity, which yield strong immune stress on cancer evolution and ultimately contributing to better prognosis of patients. Citation Format: Pengxiang Wang, Chi Zhou, Zhiting Wei, Yue Wang, Yuli Gao, Fangliangzi Meng, Jian Zhou, Jia Fan, Qi Liu, Yunfan Sun. Tertiary lymphoid structures restrain cancer evolution by supporting stem-like CD8+ T cells for sustained anti-tumor immunity [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 1515.