Adipocyte-Tumor Interactions in the Bone Marrow Niche: Implications for Metastasis and Therapy.

Bone metastases continue to be a major cause of morbidity and mortality in patients with advanced cancers, driven by the dynamic remodeling of the bone marrow niche. Traditionally viewed as passive space-fillers, bone marrow adipocytes (BMAs) are now recognized as active regulators of tumor growth, therapeutic resistance, and skeletal pathology. BMAs comprise a significant portion of the adult marrow space, particularly in aging and obesity, and facilitate metastatic colonization through various mechanisms. These include metabolic coupling, where adipocyte-derived fatty acids fuel tumor oxidative phosphorylation; the secretion of adipokines such as leptin and IL-6, which promote epithelial-to-mesenchymal transition, invasion, and immune evasion; regulation of osteoclastogenesis via RANKL expression; and the release of extracellular vesicles that reprogram cancer cell metabolism. Clinical and experimental studies show that BMA expansion correlates with increased tumor burden and poorer outcomes in breast, prostate, lung cancers, and multiple myeloma. Additionally, BMAs actively promote therapeutic resistance through metabolic rewiring and drug sequestration. Experimental models, ranging from in vitro co-cultures to in vivo patient-derived xenografts, demonstrate the complex roles of BMAs and also reveal important translational gaps. Despite promising preclinical approaches such as metabolic inhibitors, PPARγ modulation, adipokine blockade, and lifestyle changes, no therapies directly targeting BMAs have yet reached clinical practice. This review compiles current evidence on the biology of BMAs, their tumor-promoting interactions, and potential therapeutic strategies, while also highlighting unresolved questions about BMA heterogeneity, lipid flux, and immunometabolic crosstalk. By revealing how bone marrow adipocytes actively shape the metastatic niche through metabolic, endocrine, and immunological pathways, this review highlights their potential as novel biomarkers and therapeutic targets for improving the management of bone metastases.