<p>Breast cancer (BC) represents a leading cause of cancer-related mortality among women, with glycolysis and immunomodulation playing pivotal roles in its progression. This study, by integrating bioinformatics analyses and in vitro and in vivo experiments, elucidates the mechanism of action of the mitochondrial protein BNIP3 in BC. The results demonstrate that BNIP3 is aberrantly overexpressed in BC tissues and cell lines, and is significantly associated with poor prognosis. Silencing BNIP3 can suppress glycolysis in vitro and in vivo (by reducing lactate production and glucose uptake) and inhibit tumor growth. Immune infiltration analysis reveals that high BNIP3 expression induces an immunosuppressive microenvironment, characterized by a reduction in CD8⁺ T cells, an increase in M2 macrophages, a decrease in tumor mutation burden (TMB), and downregulation of immune checkpoints. Drug sensitivity analysis suggests that tumors with high BNIP3 expression are sensitive to IGF-1R/p53 inhibitors, while those with low expression respond to mTOR inhibitors. In summary, BNIP3 promotes BC progression by driving glycolysis and an immunosuppressive microenvironment, and can serve as an independent prognostic biomarker and a potential therapeutic target.</p>