POSTN⁺ CAF–SPP1⁺ macrophage crosstalk is associated with immune exclusion and poor prognosis in lung adenocarcinoma
TL;DR
A spatially organized POSTN⁺ CAF–SPP1⁺ macrophage niche that may contribute to stromal remodeling, CD8⁺ T-cell exclusion, and potentially reduced immunotherapy benefit in LUAD is defined.
Abstract
Lung adenocarcinoma (LUAD) is a highly lethal malignancy in which the tumor microenvironment (TME) plays an important role in disease progression and therapeutic resistance. However, the spatial organization and molecular basis of stromal–immune interactions in LUAD remain incompletely understood. We integrated bulk RNA sequencing, single-cell RNA sequencing, spatial transcriptomics, multiplex immunofluorescence, and in vitro functional assays to characterize TME heterogeneity and investigate mechanisms associated with stromal barrier formation and immune exclusion in LUAD. POSTN⁺ cancer-associated fibroblasts (CAFs) and SPP1⁺ macrophages were enriched in LUAD, showed marked spatial colocalization, and were associated with an immune-excluded spatial pattern characterized by limited effector T-cell infiltration. Cell–cell communication analysis identified SPP1-centered signaling from SPP1⁺ macrophages to POSTN⁺ CAFs, with CD44 emerging as a prominent receptor candidate and integrin-related receptor pairs suggested as additional candidate branches. In vitro experiments showed that TAM-like macrophage-conditioned medium activated CAF-like HFL-1 cells, increased POSTN, FN1, and COL1A1 expression, enhanced fibroblast adhesion and collagen gel contraction, and restricted primary CD8⁺ T-cell migration across CAF-like stromal barriers. These effects were attenuated by SPP1 neutralization or CD44 knockdown. In addition, CAF-derived C3 was implicated in a feedback loop that may reinforce the SPP1⁺/CD206⁺ macrophage-like phenotype. Pan-cancer analyses further showed that this stromal–myeloid program was conserved across multiple solid tumor types and was associated with poor overall survival, while exploratory cross-cancer immunotherapy analysis suggested a potential association with reduced response to immune checkpoint blockade. These findings further define a spatially organized POSTN⁺ CAF–SPP1⁺ macrophage niche that may contribute to stromal remodeling, CD8⁺ T-cell exclusion, and potentially reduced immunotherapy benefit in LUAD. The TAM-derived SPP1–CD44 axis and CAF-derived C3 feedback loop may provide a framework for biomarker development and therapeutic targeting in immune-excluded solid tumors.