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RUNX2 expression in developing human bones and various bone tumors
Masato Sugawara1, Noriko Kato, Takashi Tsuchiya
1Departments of Pathology Orthopaedic Surgery, Yamagata University School of Medicine, Yamagata, Japan.
Abstract:
The heterozygous germline mutation of runt-related protein 2 (RUNX2) causes cleidocranial dysplasia. To clarify the involvement of RUNX2 in human osteogenesis, fetal bones and various bone tumors were immunohistochemically examined. During both membranous and endochondral ossification in the fetus (n= 8), RUNX2 was expressed not only in osteoblastic cells but also in surrounding mesenchymal cells and early stage chondrocytes. Such an expression pattern was recapitulated in bone tumors: RUNX2 was unequivocally expressed in osteosarcoma (n= 20) and fibrous dysplasia (n= 10), regardless of the site of occurrence, cell morphology or amount of neoplastic osteoid. RUNX2 expression was limited to less differentiated cells in chondrogenic tumors (n= 20). We further analyzed whether RUNX2 expression was regulated by bone morphogenetic protein-2 (BMP-2), which is critical for osteoblastic differentiation. With real-time polymerase chain reaction, the RUNX2 mRNA level was correlated with BMP-2 mRNA level, and both levels were significantly higher in three osteosarcoma cell lines than in three chondrosarcoma cell lines. With treatment of recombinant BMP-2, the RUNX2 mRNA level was significantly altered in these cell lines. RUNX2 expression is constitutive in developing and neoplastic human osteogenesis, and is most likely to be regulated by BMP-2.
Insights
Runt-related protein 2 (RUNX2) is crucial for human osteogenesis, found in developing bone cells and tumors. Bone morphogenetic protein-2 (BMP-2) likely regulates RUNX2 expression, impacting bone development and disease.
Area of Science:
- Molecular Biology
- Developmental Biology
- Oncology
Background:
- Cleidocranial dysplasia is linked to heterozygous germline mutations in runt-related protein 2 (RUNX2).
- Understanding RUNX2's role in human osteogenesis is critical for bone development and pathology.
- RUNX2 is a key transcription factor in bone formation.
Purpose of the Study:
- To investigate the expression patterns of RUNX2 in fetal human bone development.
- To examine RUNX2 expression in various human bone tumors.
- To explore the regulatory relationship between RUNX2 and bone morphogenetic protein-2 (BMP-2).
Main Methods:
- Immunohistochemical analysis of fetal bones (n=8) and bone tumors (osteosarcoma n=20, fibrous dysplasia n=10, chondrogenic tumors n=20).
- Real-time polymerase chain reaction (PCR) to assess RUNX2 and BMP-2 mRNA levels in cell lines.
- Treatment of osteosarcoma and chondrosarcoma cell lines with recombinant BMP-2.
Main Results:
- RUNX2 was expressed in osteoblastic and mesenchymal cells, and early chondrocytes during fetal ossification.
- Consistent RUNX2 expression was observed in osteosarcoma and fibrous dysplasia, irrespective of tumor characteristics.
- RUNX2 expression in chondrogenic tumors was restricted to less differentiated cells.
- RUNX2 mRNA levels correlated with BMP-2 mRNA levels, higher in osteosarcoma than chondrosarcoma cell lines.
- Recombinant BMP-2 treatment significantly altered RUNX2 mRNA levels in cell lines.
Conclusions:
- RUNX2 expression is constitutive during human osteogenesis, both in development and neoplastic processes.
- BMP-2 is a likely regulator of RUNX2 expression in human bone formation.
- RUNX2's role extends to bone tumor pathogenesis, with distinct expression patterns in different tumor types.
