Abstract 6118: Spatially resolved SEED (stromal-enriched metastatic decider) niches integrate tumor, stromal, and immune ecosystems to enable lymph node dissemination in LUAD

Abstract Purpose: Lung adenocarcinoma (LUAD) displays substantial intratumoral heterogeneity, but the precise primary-tumor subregions that give rise to lymph-node metastasis remain unclear. We aimed to identify metastasis-competent SEED regions and characterize their microenvironmental context using paired single-cell-resolution spatial transcriptomics. Methods: Formalin-fixed tissues from 17 LUAD patients were profiled using the 10x Genomics Xenium 5K panel, generating paired datasets from primary tumors and matched lymph-node metastases. Spatial and transcriptional integration was performed using Seurat and SpatialData, and metascores and differential expression analyses were computed with Scanpy. Results: Integrated primary-lymph node analysis revealed a recurrent tumor-cell cluster whose transcriptional state aligned most closely with lymph-node profiles, representing a metastasis-competent SEED population. SEED regions showed elevated metascores and enrichment of invasion and hypoxia-associated programs, including robust HIF1A upregulation. The surrounding microenvironment was spatially distinct: fibroblasts immediately adjacent to seed clusters exhibited high POSTN expression, forming a dense stromal shell, while CXCR4-high B-cell aggregates accumulated peritumorally. In contrast, T-cell distribution remained relatively uniform across regions, indicating that SEED-associated remodeling was driven by specific stromal and B-cell interactions rather than general immune infiltration. Together, these spatially coordinated patterns delineate a niche in which HIF1A-high tumor cells interface with POSTN-rich fibroblasts and CXCR4-expressing B cells to support metastatic competence. Conclusions: Paired single-cell spatial mapping identifies discrete metastasis-prone SEED niches within LUAD primary tumors. These niches are defined by HIF1A-high tumor cells embedded in a POSTN-rich stromal compartment and surrounded by CXCR4-high B-cell aggregates. This spatial ecosystem provides a mechanistic framework for how only specific primary-tumor regions acquire the capacity for lymph-node dissemination and suggests niche-level targets for metastasis interception. Citation Format: Junghan Oh, Hoyeon Jeong, Yoon La Choi, Donggun Lee, Misook Lee. Spatially resolved SEED (stromal-enriched metastatic decider) niches integrate tumor, stromal, and immune ecosystems to enable lymph node dissemination in LUAD [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6118.