1. ¹Fred A Litwin Centre for Cancer Genetics, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
2. ²Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada
3. ³Department of Surgery, University of Toronto, Toronto, Ontario, Canada
4. ⁴University Muskuloskeletal Oncology Unit, Mount Sinai Hospital, Toronto, Ontario, Canada
5. ⁵Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ontario, Canada
6. ⁶Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada

Correspondence: Professor IL Andrulis, PhD, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Rm984, 600 University Ave., Toronto, Ontario, Canada M5G 1X5. E-mail: andrulis@mshri.on.ca

Received 10 November 2003; Revised 22 June 2004; Accepted 28 July 2004; Published online 1 October 2004.

Abstract

A number of genes are implicated in the initiation and progression of osteosarcoma; however, cytogenetic and comparative genomic hybridization studies indicate the involvement of additional unidentified genes. An examination of gene expression profiles in 22 high-grade osteosarcoma tumor specimens from 15 patients (including paired primary and metastatic samples from five patients) indicated that von Willebrand factor (vWF) mRNA expression may increase during tumor progression. vWF, a large glycoprotein previously considered to be expressed exclusively by endothelial cells and megakaryocytes, is involved in platelet aggregation and adhesion to the subendothelial matrix, processes critical to hematogenous tumor cell metastasis to the lung. Analysis of paired primary and metastatic osteosarcoma tumor samples from 10 patients revealed an increase in vWF gene expression in metastases (P=0.005). Immunohistochemistry showed that, in addition to the endothelial cells, vWF protein was also detected in osteosarcoma cells in vivo in 13 of 29 tumor specimens as well as in SAOS2, an osteosarcoma cell line. The tumor cell staining correlated positively with high vWF expression in the sample (P=0.006). Although vascular endothelial cells contribute to the vWF mRNA detected in the tumor samples, there was neither any correlation between vascular density (VD) and vWF mRNA expression nor between VD and clinical outcome. These findings suggest that vWF expression is deregulated in osteosarcoma tumors, potentially contributing to metastasis.