FGF4 drives tumor progression in triple-negative breast cancer via IL6/STAT3-mediated macrophage M2 polarization and immune suppression.

Abstract

Objective: This study investigates how Fibroblast Growth Factor 4 (FGF4) drives triple-negative breast cancer (TNBC) progression by modulating macrophage polarization through the IL6/STAT3 signaling axis, with a focus on immune suppression and tumor microenvironment remodeling.

Methods: TNBC transcriptomic datasets from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were analyzed to identify FGF4-associated pathways using differential gene expression analysis, Weighted Gene Co-expression Network Analysis (WGCNA), and immune infiltration profiling via Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT). Functional annotations (GO/KEGG) highlighted IL6/STAT3 as a key pathway. In vitro models with FGF4-overexpressing or knockdown TNBC cells were co-cultured with macrophages to assess IL6/STAT3 activation, M2 polarization markers (CD206, Arg1), and cytokine secretion (ELISA). Tumor cell behaviors (proliferation, migration, invasion) were quantified. In vivo orthotopic TNBC models in mice evaluated FGF4's impact on tumor growth, immune cell infiltration (flow cytometry), and STAT3 activity (Western blot).

Results: FGF4 was upregulated in TNBC and strongly correlated with M2 macrophage infiltration. In vitro, FGF4 activated IL6/STAT3 signaling, inducing macrophage polarization to an M2 phenotype with elevated IL-10/TGF-βsecretion and suppression of T cell proliferation. Conditioned media from M2 macrophages enhanced TNBC cell aggressiveness. In vivo, FGF4-overexpressing tumors showed higher weight and increased M2 markers, whereas FGF4 knockdown reduced tumor volume and enhanced CD8⁺ T cell infiltration.

Conclusion: FGF4 promotes TNBC progression by activating IL6/STAT3 to reprogram macrophages into immune-suppressive M2 effectors, fostering a tumor-permissive microenvironment. Targeting FGF4 may disrupt this crosstalk, offering a novel immunotherapeutic strategy for TNBC.