Single-cell Analysis Reveals a LAMB3-dependent Immunosuppressive Environment in Gallbladder Neck/Cystic Duct Carcinoma.

[BACKGROUND & AIMS] Gallbladder cancer (GBC) originating from the fundus/body (GBC) and neck/cystic duct (GBC) exhibits distinct clinical outcomes. Location-associated heterogeneity is intricately linked to oncogenic properties and multicellular interactions within the tumor microenvironment (TME).

[METHODS] Single-cell transcriptomic analysis was performed on 569,736 cells derived from 38 GBC and 17 GBC samples. Whole-exome sequencing (WES) was employed to identify genomic alterations in malignant epithelial cells. Additionally, TCGA datasets, multiplex immunohistochemistry, scTCR-seq, spatial transcriptomics, and functional assays were integrated to investigate subtype-specific differences.

[RESULTS] The cellular atlas revealed distinct TME patterns. Hallmarked by TP53 mutations and robust antigen presentation, GBC tumors were enriched with plasma cells (P = 0.009), CXCL13 T cells (P = 0.046), CXCL9 macrophages (P = 0.042), and proliferative immune cells (P = 0.015), constituting an immune-activated TME. Conversely, stem-like GBC tumor cells fostered an angiogenic, immunosuppressive milieu, enriched with endothelial cells (P = 0.02), SPP1 macrophages (P = 0.006), MYH11 vCAFs (P = 0.029), and GZMKNR4A2CD8 T cells (P = 0.028). Notably, elevated LAMB3 in GBC tumor cells emerged as a central immune regulator, driving macrophage infiltration and T-cell dysfunction to establish an immunosuppressive niche.

[CONCLUSION] This study underscores the profoundly immunosuppressive microenvironment in gallbladder cancer originating from the neck/cystic duct (GBC), highlights the role of LAMB3 tumor cells in immune modulation, and identifies LAMB3 as a potential therapeutic target for GBC.

[IMPACT AND IMPLICATIONS] By delineating distinct tumor microenvironment (TME) landscapes between gallbladder cancers (GBC) originating from the fundus/body (GBC) and those from the neck/cystic duct (GBC), this study provides compelling evidence for site-specific precision therapeutic strategies. We demonstrate that GBC tumors are highly enriched with established biomarkers predictive of immunotherapy responsiveness-including elevated tumor mutational burden (TMB), robust PD-L1 and interferon-γ signatures, and abundant CXCL13 T cells, plasma cells, and CXCL9 macrophages-indicating these patients are optimal candidates for immunotherapeutic interventions. Conversely, GBC tumors exhibit a profoundly immunosuppressive TME orchestrated by LAMB3 tumor cells. Targeting LAMB3 therefore represents a promising approach to overcome immune resistance in patients with GBC.