Inactive Wnt/beta-catenin pathway in conventional high-grade osteosarcoma.

Abstract

Osteosarcoma is the most common malignant bone tumour, with a peak incidence in children and young adolescents, suggesting a role of rapid bone growth in its pathogenesis. The Wnt/beta-catenin pathway plays a crucial role in skeletal development and is indispensable for osteoblasts' lineage determination. Previous studies suggesting an oncogenic role for the Wnt/beta-catenin pathway in osteosarcoma were based on cytoplasmic staining of beta-catenin or the detection of one component of this pathway. However, those approaches are inappropriate to address whether the Wnt/beta-catenin pathway is functionally active. Therefore, in this study, we examined nuclear beta-catenin expression in 52 human osteosarcoma biopsies, 15 osteoblastomas (benign bone tumours), and four human osteosarcoma cell lines by immunohistochemistry. Furthermore, we modulated Wnt/beta-catenin pathway activity using a GIN (GSK3beta inhibitor) and evaluated its effect on cell growth and osteogenic differentiation. Absence of nuclear beta-catenin staining was found in 90% of the biopsies and all osteosarcoma cell lines, whereas strong nuclear beta-catenin staining was observed in all osteoblastomas. Wnt-luciferase activity was comparable to the negative control in all osteosarcoma cell lines. GIN stimulated the Wnt/beta-catenin pathway, as shown by translocation of beta-catenin into the nucleus and increased Wnt-luciferase activity as well as mRNA expression of AXIN2, a specific downstream target gene. Stimulation of the Wnt/beta-catenin pathway by GIN significantly reduced cell proliferation in the cell lines MG-63 and U-2-OS and enhanced differentiation in the cell lines HOS and SJSA-1, as shown by an increase in alkaline phosphatase (ALP) activity and mineralization. In contrast with the oncogenic role of the Wnt/beta-catenin pathway in osteosarcoma as previous studies suggested, here we demonstrate that this pathway is inactivated in osteosarcoma. Moreover, activation of the Wnt/beta-catenin pathway inhibits cell proliferation or promotes osteogenic differentiation in osteosarcoma cell lines. Our data suggest that loss of Wnt/beta-catenin pathway activity, which is required for osteoblast differentiation, may contribute to osteosarcoma development.

• Authors: Yongping Cai, Alexander B Mohseny, Marcel Karperien, Pancras C W Hogendoorn, Gengyin Zhou, Anne-Marie Cleton-Jansen
• Journal: The Journal of pathology (J Pathol) Vol. 220 Issue 1 Pg. 24-33 (Jan 2010) ISSN: 1096-9896 [Electronic] England
• PMID: 19882675 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DKK1 protein, human
• Hedgehog Proteins
• Intercellular Signaling Peptides and Proteins
• Neoplasm Proteins
• Recombinant Proteins
• Wnt Proteins
• Wnt3 Protein
• beta Catenin
• GSK3B protein, human
• Glycogen Synthase Kinase 3 beta
• Gsk3b protein, mouse
• Glycogen Synthase Kinase 3

Topics

• Animals
• Bone Neoplasms (metabolism, pathology, physiopathology)
• Cell Differentiation (physiology)
• Cell Proliferation
• Glycogen Synthase Kinase 3 (antagonists & inhibitors, physiology)
• Glycogen Synthase Kinase 3 beta
• Hedgehog Proteins (physiology)
• Humans
• Intercellular Signaling Peptides and Proteins (metabolism)
• Mice
• Neoplasm Proteins (metabolism, physiology)
• Osteoblasts (pathology)
• Osteosarcoma (metabolism, pathology, physiopathology)
• Recombinant Proteins (pharmacology)
• Reverse Transcriptase Polymerase Chain Reaction (methods)
• Signal Transduction (drug effects, physiology)
• Tumor Cells, Cultured
• Wnt Proteins (pharmacology, physiology)
• Wnt3 Protein
• beta Catenin (metabolism)