RANK/RANKL/OPG signaling in bone graft integration in oncologic patients

Abstract

Introduction: Bone grafting is frequently required in oncologic patients after tumor resection, management of pathological fractures, or reconstruction following metastatic bone destruction. Successful graft integration depends on a tightly regulated balance between bone resorption and bone formation, processes controlled primarily by the receptor activator of nuclear factor kappa-B (RANK), its ligand RANKL, and the decoy receptor osteoprotegerin (OPG). In malignancy-associated bone disease, this regulatory axis is often disrupted, resulting in excessive osteoclast activation and structural instability. The objective of this study was to elucidate the molecular mechanisms through which imbalance of the RANK/RANKL/OPG signaling pathway affects bone graft integration in oncologic patients. Material and methods: A structured narrative literature review was conducted using 10 peerreviewed articles published between 2016 and 2026. Data were collected from biomedical databases including ScienceDirect, PubMed Central, BioMed Central, and related scientific sources. Experimental studies, translational research, and clinical investigations evaluating alterations in RANK, RANKL, and OPG expression in primary bone tumors and bone metastases were analyzed. Particular emphasis was placed on molecular signaling pathways, cytokine-mediated regulation, and their implications for bone remodeling and graft incorporation. Results: Malignant cells and tumor-associated stromal elements promote increased RANKL expression while suppressing OPG production, leading to enhanced osteoclastogenesis. This imbalance accelerates bone resorption, degrades extracellular matrix integrity, and weakens mechanical stability at the graft-host interface. Pro-inflammatory cytokines such as interleukin-6 (Il6) and tumor necrosis factor-α (TNF-α) further stimulate osteoclast differentiation and amplify osteolytic activity. Sustained bone turnover interferes with osteoblast-mediated mineralization and delays graft incorporation. Emerging evidence indicates that targeted modulation of the RANK/RANKL/OPG pathway may reduce pathological bone resorption and create a more favorable microenvironment for graft integration. Furthermore, disruption of this signaling balance alters cellular communication within the bone niche, prolonging catabolic remodeling and increasing the risk of incomplete graft stabilization. Conclusion: Dysregulation of the RANK/RANKL/OPG axis represents a central biochemical mechanism contributing to impaired bone graft integration in oncologic patients. Improved understanding of this pathway may support the development of molecularly guided therapeutic strategies aimed at enhancing reconstructive outcomes and long-term graft stability.