title: Expression of an exogenous human Oct-4 promoter identifies tumor-initiating cells in osteosarcoma.
abstract: We explored the nature of the tumor-initiating cell in osteosarcoma, a bone malignancy that predominately occurs in children. Previously, we observed expression of Oct-4, an embryonal transcriptional regulator, in osteosarcoma cell cultures and tissues. To examine the relationship between Oct-4 and tumorigenesis, cells from an osteosarcoma biopsy (OS521) were stably transfected with a plasmid containing the human Oct-4 promoter driving a green fluorescent protein (GFP) reporter to generate the transgenic line OS521Oct-4p. In culture, only approximately 24% of the OS521Oct-4p cells were capable of activating the transgenic Oct-4 promoter; yet, xenograft tumors generated in NOD/SCID mice contained approximately 67% GFP(+) cells, which selectively expressed the mesenchymal stem cell-associated surface antigens CD105 and ICAM-1. Comparison of the tumor-forming capacity of GFP-enriched and GFP-depleted cell fractions revealed that the GFP-enriched fractions were at least 100-fold more tumorigenic, capable of forming tumors at doses of <300 cells, and formed metastases in the lung. Clonal populations derived from a single Oct-4/GFP(+) cell were capable of forming tumors heterogeneous for Oct-4/GFP expression. These data are consistent with the cancer stem cell model of tumorigenesis in osteosarcoma and implicate a functional link between the capacity to activate an exogenous Oct-4 promoter and tumor formation. This osteosarcoma tumor-initiating cell appears highly prolific and constitutes a majority of the cell population in a primary xenograft tumor, which may provide a biological basis for the particular virulence of this type of cancer.
authors: Department of Orthopaedics and Rehabilitation, University of Florida College of Medicine, Gainesville, Florida 32611, USA.
authors: Padraic P
authors: PP
authors: Levings
authors: Sean V
authors: SV
authors: McGarry
authors: Thomas P
authors: TP
authors: Currie
authors: David M
authors: DM
authors: Nickerson
authors: Steven
authors: S
authors: McClellan
authors: Steven C
authors: SC
authors: Ghivizzani
authors: Dennis A
authors: DA
authors: Steindler
authors: C Parker
authors: CP
authors: Gibbs
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D045744:Cell Line, Tumor; D000071063:Endoglin; D005260:Female; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008856:Microscopy, Fluorescence; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D050814:Octamer Transcription Factor-3 / Q000235:genetics*; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000032:analysis; D012513:Sarcoma, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D014162:Transfection
chemical_list: D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D050814:Octamer Transcription Factor-3; D011956:Receptors, Cell Surface; D018799:Intercellular Adhesion Molecule-1; D049452:Green Fluorescent Proteins