Abstract 2661: Identification of a novel morphology of tertiary lymphoid structure in patients with hepatocellular carcinoma treated with neoadjuvant immune checkpoint blockade

Abstract Background: Tertiary lymphoid structures (TLS) are ectopic lymphoid follicles that arise in non-lymphoid tissue. TLS may contribute to response to immune checkpoint blockade (ICB) in solid tumors, but understanding of the life cycle of these structures, particularly the circumstances of their resolution and the functional contribution of this stage to the adaptive immune response, remains incomplete. Methods: We employed a multi-omics approach to evaluate TLS in the tumors of patients with hepatocellular carcinoma (HCC) treated with neoadjuvant ICB (n = 19) and untreated controls (n = 14). TLS density was assessed by immunohistochemistry and correlated with pathologic response, relapse free survival, and overall survival. Imaging mass cytometry was used to characterize distinct TLS morphologies in areas of tumor regression bed and viable tumor. Individual TLS from treated tumors were microdissected and characterized by T cell receptor (TCR) and immunoglobulin heavy chain (IGH) sequencing, and TCR clonotypes identified in TLS were further characterized by comparison against matched single cell RNA and TCR sequencing of peripheral blood and TIL. Results: Intratumoral TLS density was significantly increased in HCC tumors treated with neoadjuvant ICB compared to untreated controls (p = 0.05). Tumors with major or complete pathologic response to treatment had significantly higher intratumoral TLS density compared to tumors with partial pathologic response (p = 0.000246) and non-response (p = 0.0129). In the treatment group, patients with tumors in the top tertile of intratumoral TLS density had significantly longer relapse free survival (p = 0.021 by log-rank test). In the regression bed of treated tumors, an involuted TLS morphology was identified which was notable for dispersion of the B cell germinal center, retention of a T cell zone enriched for T-DC interactions, and increased expression of markers of T cell memory. In a subset of patients, immune repertoire sequencing demonstrated increased TCRβ clonality and BCR somatic hypermutation at involuted TLS. Highly expanded T cell clonotypes identified in TLS were found in the GZMK+ and GZMB+ CD8 T effector memory clusters in matched single cell data. Conclusions: These data suggest that in HCC tumors treated with neoadjuvant ICB, treatment may induce formation of intratumoral TLS, which are associated with superior pathologic response and relapse free survival. An involuted TLS morphology is identified in tumor regression bed with features consistent with dissolution of the B cell germinal center, persistent antigen presentation to T cells, and increased T cell memory formation. Taken together, these findings suggest a potential role for late-stage TLS in supporting consolidation of the intratumoral T cell repertoire after elimination of viable tumor. Citation Format: Daniel H. Shu, Won Jin Ho, Luciane T. Kagohara, Alexander Girgis, Sarah M. Shin, Ludmila Danilova, Jae W. Lee, Dimitrios N. N. Sidiropoulos, Sarah Mitchell, Kabeer Munjal, Kathryn Howe, Kayla J. Bendinelli, Hanfei Qi, Guanglan Mo, Janelle Montagne, Tamara Y. Lopez-Vidal, Qingfeng Zhu, Amanda L. Huff, Xuan Yuan, Alexei Hernandez, Erin M. Coyne, Neeha Zaidi, Daniel J. Zabransky, Logan L. Engle, Aleksandra Ogurtsova, Marina Baretti, Daniel Laheru, Jennifer N. Durham, Hao Wang, Robert Anders, Elizabeth M. Jaffee, Elana J. Fertig, Mark Yarchoan. Identification of a novel morphology of tertiary lymphoid structure in patients with hepatocellular carcinoma treated with neoadjuvant immune checkpoint blockade [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 2661.