Abstract 5333: Relationship of osteosarcoma surface marker expression to human mesenchymal stem cells undergoing osteoblastic differentiation

Abstract

Abstract Osteosarcoma (OS) is the most common primary malignant bone tumor in children and young adults, but it is unknown at what point, in the pathway of differentiation between a human mesenchymal stem cell (hMSC) and a mature osteoblast (OB), OS originates. Identifying the cell of origin is crucial in understanding the molecular pathogenesis of OS. These studies are hampered by the fact that the various steps in the differentiation of human MSC into its more differentiated progenitors are poorly characterized. In this study, hMSCs were derived from the freshly obtained bone marrow of patients as well as purchased through ATCC. Flow cytometry was used to detect the surface expression phenotype of MSC markers, where CD34 and CD45 were negative and CD44, CD73, CD90, and CD105 were positive. The hMSCs were characterized and all demonstrated multilineage differentiation capacity into adipocytes, chondroblasts, and osteoblasts, which was confirmed by Oil Red O, Alcian Blue, and Alizarin Red S stains, respectively. Osteoblasts were further characterized by measuring osteocalcin protein levels using ELISA. RNA was extracted from hMSCs and OB derived from the same patient and gene expression measured by microarray on the Affymetrix Gene 1.0 ST array. A list of differentially expressed genes was generated, which were narrowed to only include surface markers. Antibodies corresponding to surface markers were used for ELISA and flow cytometry on hMSCs and OBs, to confirm the change in gene expression with differentiation. Further studies will include flow cytometry to define intermediate stages in the differentiation pathway from hMSCs to OBs and their capacity to differentiate into the various mesenchymal lineages. It has been possible to derive hMSC with pluripotent differentiation capacity from patient bone marrows. These will be utilized to define the patterns of differentiation and ultimately relate to osteosarcoma to help define its progenitor cell. It is hoped that a clearer understanding of the progenitor cell of OS will help find prognostic factors and molecular therapeutic targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5333. doi:10.1158/1538-7445.AM2011-5333