Cytokine Networks Reprogramming the Osteo-Immune Microenvironment in Cancer Bone Metastasis

Bone metastasis is a major clinical challenge and is frequently associated with resistance to immunotherapy and progressive skeletal destruction. Although cytokines are recognized as key regulators of both immune responses and bone remodeling, their integrated roles in the bone metastatic niche remain incompletely understood. Here, we propose a conceptual framework in which cytokine-driven osteo-immune reprogramming shapes the bone microenvironment into a state that supports tumor persistence. Within this framework, cytokines can be categorized into three functional groups-immune-dominant mediators, osteo-immune regulators, and divergent factors-whose context-dependent activities collectively coordinate immune suppression and osteoclastic bone destruction. Rather than acting independently, these cytokines form interconnected networks that establish reinforcing interactions, thereby stabilizing an immunologically cold and therapy-resistant niche. This integrated perspective suggests that immune resistance in bone metastasis does not arise solely from tumor-intrinsic properties, but emerges from dynamic crosstalk in the osteo-immune axis. The spatiotemporal regulation of cytokine signaling likely defines stage-specific vulnerabilities, providing opportunities for therapeutic intervention. Targeting cytokine networks in combination with immune checkpoint inhibitors and bone-modifying agents may represent a rational strategy to disrupt pathogenic osteo-immune circuits. A deeper understanding of the reprogramming of the bone microenvironment by cytokines will be essential for enabling durable immunotherapeutic responses in patients with bone metastatic disease.