Lipid metabolism-associated immune gene LPL promotes M1 macrophage polarization and inhibits breast cancer progression.

Background: Breast cancer (BRCA) ranks among the most frequently diagnosed malignancies worldwide. Immune infiltration plays a critical role in tumor progression and therapeutic response. However, the precise mechanisms underlying immune infiltration in BRCA remain incompletely understood.

Methods: Machine learning (support vector machine-recursive feature elimination and least absolute shrinkage and selection operator regression) and weighted gene co-expression network were utilized to screen hub genes. An immune infiltration assessment was carried out via TIMER and CIBERSORT. The prognostic and survival of risk model and immune infiltration-associated hub genes were analyzed through Kaplan-Meier survival analysis, Cox regression, and ROC curve evaluation. Cell functional assays and xenograft models in vivo were utilized to examine lipoprotein lipase (LPL) function. The impact of LPL on macrophage polarization was evaluated using THP-1-derived macrophages and immunohistochemistry analysis of immune infiltration (CD4, CD8, and F4/80) in vivo.

Results: 10 hub immune regulators were identified in BRCA, which were associated with lipid metabolism. Hub genes and a prognostic risk model exhibited high predictive accuracy for BRCA patient survival and prognosis. Overexpression of LPL inhibited BRCA cell proliferation, migration, and invasion while promoting M1-like macrophage polarization. In vivo, LPL overexpression significantly suppressed tumor growth and enhanced immune cell infiltration, as indicated by the elevation of CD4 + and F4/80 + cells along with a decline in CD8 + macrophage abundance.

Conclusion: This study identifies a novel lipid metabolism-related gene signature and demonstrates that LPL overexpression modulates macrophage polarization and inhibits BRCA progression.