Spatial organisation of tumor-infiltrating B-cells informs immune checkpoint inhibitor response in Claudin 18.2-expressing gastric cancer
Joseph J. Zhao, Choong-kun Lee, Allison S.Y. Chan, Steven Blum, Chang Li, Haoran Ma, Wenyi Luo, Supriya Srivastava, Huey Yew Jeffrey Lum, Sheng Cong Norbert Tay, Woo Sun Kwon, Sejung Park, Craig Ryan Joseph, Li Yen Chong, Minkyu Jung, Shruti Sridhar, Aurelien Pelissier, Nilay Bhatt, Jia-Ying Joey Lee, Yichen Dai, Lit-Hsin Loo, Angie Lay Keng Tan, Takeshi Hagihara, Felicia Wee, Daryl K. A. Chia, Kevin M. S. Sim, Ming Teh, Izuma Nakayama, Jierui Xu, Matthew Chau Hsien Ng, Robert Walsh, Joe Poh Sheng Yeong, Anand D. Jeyasekharan, Heike I. Grabsch, Jimmy Bok-Yan So, Wei Peng Yong, Ignacio Vazquez-Garcia, Lloyd Bod, Samuel J. Klempner, Kohei Shitara, Yelena Janjigian, Patrick Tan, María Rodríguez Martínez, Sun Young Rha, Raghav SundarAbstract
Purpose: Claudin 18.2 (CLDN18.2), a tight junction protein normally expressed in gastric epithelium and rendered accessible during malignant transformation, has emerged as a key therapeutic target. Here, we seek to characterize the immune microenvironment of CLDN18.2-expressing gastric cancer and identify immune features associated with CLDN18.2 expression status. Patients and Methods: Tumor immune features were profiled in 103 patients with HER2-neg/low advanced GC treated with first-line immune checkpoint inhibitor (ICI) using multiplex immunohistochemistry (7,423,483 cells across 2,315 regions of interest [ROIs]). Findings were validated in five published whole-transcriptome sequencing/microarray cohorts (1,521 samples), including the CheckMate 649 phase 3 trial. Spatial architecture was assessed by cellular neighborhood analysis. Digital spatial profiling (DSP) was performed on 480 ROIs from a CLDN18.2-annotated tissue microarray (75 patients). Results: CLDN18.2high tumors showed reproducible enrichment of humoral pathways, with higher CD20+ B-cell density and enrichment of B-cell/plasma-cell signatures. CLDN18.2 status alone was not associated with survival on first-line ICI therapy; in CLDN18.2low tumors, B-cell enrichment was associated with ICI benefit, unlike CLDN18.2high tumors. Spatial analyses indicated that CLDN18.2high tumors preferentially harbored tumor-infiltrating B-cells, rather than tertiary lymphoid structure/lymphoid aggregate–like neighborhoods, and this tumor-compartment localization was associated with diminished ICI benefit. DSP confirmed that CD20+ B-cell enrichment was most pronounced within tumor regions, alongside compartment-specific activation of humoral and extra-follicular response programs and interferon-associated and remodeling signatures. Conclusions: CLDN18.2high GC exhibits a humoral-enriched microenvironment with increased tumor-infiltrating B-cells and spatial immune organization associated with reduced ICI benefit. Spatial and humoral-state biomarkers may inform ongoing CLDN18.2-directed combination trials.