Spatial atlas of gastric cancer reveals macrophage-driven stromal activation via ICAM1⁺ smooth muscle cells

Stromal remodeling constitutes a hallmark of gastric cancer (GC) progression, yet the intercellular signaling networks orchestrating this process remain incompletely understood. Single-cell RNA sequencing (scRNA-seq) data from 172,763 cells (GSE167297: n = 30,365; OMIX001073: n = 142,398) were integrated with spatial transcriptomic profiles from 10 GC samples (GSE251950). The analyses encompassed single-cell integration, spatial deconvolution, spatial architecture reconstruction, identification of tertiary lymphoid structures (TLSs), and inference of intercellular communication networks. Clinical relevance was evaluated through survival analyses across multiple independent public cohorts. Key computational findings were validated using multiplex immunofluorescence staining, quantitative real-time PCR, and transwell co-culture migration assays. A single-cell–resolved spatial atlas of the GC tumor microenvironment (TME) was constructed. Spatial–cellular integration revealed aberrant immune cell redistribution, with enrichment of CD4⁺CXCL13⁺TOX2⁺ and CD8_Trm-ZNF683⁺ T cells in paratumor regions, indicating potential roles in immune surveillance and tumor restraint. Spatial architecture delineated six distinct microenvironmental niches: C0 (immune-active, TLS-enriched), C1 (dendritic cell-dominant, immunoregulatory), C2 (immune–stromal interface), C3/C4 (epithelial-rich tumor cores), and C5 (stromal-supportive). TLSs were predominantly localized within the immune-active C0 niche, representing mature immune hubs. Within the stromal C5 niche, a coordinated stromal activation mechanism was identified, mediated by a macrophage–smooth muscle cell (SMC)–fibroblast axis driven by synergistic macrophage-derived ITGB2–ICAM1 and OSM–OSMR signaling. Immunofluorescence co-localization and qPCR assays confirmed elevated expression of OSM, OSMR, ITGB2, and ICAM1 in tumor tissues. Functionally, Functionally, transwell co-culture assays demonstrated that macrophage-derived OSM and ITGB2 were associated with enhanced SMCs proliferation and migratory capacity, while silencing either molecule significantly attenuated this effect. This dual signaling axis promoted ICAM1⁺ SMC proliferation and activation through PI3K/Akt pathway engagement and extracellular matrix (ECM) remodeling, resulting in extensive stromal reorganization and a pro-tumorigenic microenvironment. Across multiple cohorts, concurrent activation of ITGB2 and OSM pathways was associated with significantly poorer overall survival compared with activation of either pathway alone, underscoring the prognostic and therapeutic relevance of this interaction. This study reconstructs the GC spatial architecture at single-cell resolution, and reveals a previously unrecognized macrophage-driven stromal activation program mediated by convergent ITGB2–ICAM1 and OSM–OSMR signaling. ICAM1⁺ SMCs emerge as key effectors and potential targets for stromal-directed therapy.