BGN Secreted by Cancer-Associated Fibroblasts Promotes Esophageal Squamous Cell Carcinoma Progression via Activation of TLR4-Mediated Erk and NF-κB Signaling Pathways

Esophageal squamous cell carcinoma (ESCC) is associated with poor prognosis due to aggressive invasion and therapy resistance. Cancer-associated fibroblasts (CAFs) are key stromal components that promote tumor progression; however, their specific roles in ESCC remain unclear. Using a direct co-culture model of ESCC cell lines (TE-9, -10, and -15) and mesenchymal stem cells (MSCs) to generate CAF-like cells, we identified biglycan (<i>BGN</i>) as a significantly upregulated gene in CAF-like cells via cDNA microarray analysis. Public single-cell RNA sequencing data also demonstrated elevated <i>BGN</i> expression in CAF clusters. We confirmed that CAF-like cells exhibited elevated BGN expression and secretion at both the mRNA and protein levels. Recombinant human BGN enhanced ESCC cell proliferation and migration by activating Erk and NF-κB signaling pathways, effects abrogated by TLR4 blockade. Furthermore, BGN promoted CAF marker expression in MSCs, M2-like macrophage polarization, and enhanced proliferation and migration abilities in both cell types. Immunohistochemical analysis of 66 ESCC tissues revealed that high stromal BGN expression correlated with greater tumor invasion, lymphatic invasion, and shorter disease-free survival. These findings indicate that CAF-derived BGN promotes ESCC progression via TLR4-mediated signaling and modulates stromal cell behavior, highlighting its potential as a prognostic biomarker and therapeutic target.