Single-cell analysis reveals a LAMB3-dependent immunosuppressive environment in gallbladder neck/cystic duct carcinoma.

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

METHODSSingle-cell transcriptomic analysis was performed on 569,736 cells derived from 38 GBCF/B and 17 GBCN/CD samples. Whole-exome sequencing (WES) was used 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.

RESULTSThe cellular atlas revealed distinct TME patterns. Hallmarked by TP53 mutations and robust antigen presentation, GBCF/B 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 GBCN/CD 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 GZMK+NR4A2+CD8+ T cells (p = 0.028). Notably, elevated LAMB3 in GBCN/CD tumor cells emerged as a central immune regulator, driving macrophage infiltration and T-cell dysfunction to establish an immunosuppressive niche.

CONCLUSIONSThis study underscores the profoundly immunosuppressive microenvironment in gallbladder cancer originating from the neck/cystic duct (GBCN/CD), highlights the role of LAMB3+ tumor cells in immune modulation, and identifies LAMB3 as a potential therapeutic target for GBCN/CD.

IMPACT AND IMPLICATIONSBy delineating distinct TME landscapes between GBC originating from the fundus/body (GBCF/B) and those from the neck/cystic duct (GBCN/CD), this study provides compelling evidence for site-specific precision therapeutic strategies. We demonstrate that GBCF/B tumors are highly enriched with established biomarkers predictive of immunotherapy responsiveness-including elevated tumor mutational burden, 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, GBCN/CD 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 GBCN/CD.