Expression of an exogenous human Oct-4 promoter identifies tumor-initiating cells in osteosarcoma.
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.
Levings
Padraic P
PP
Department of Orthopaedics and Rehabilitation, University of Florida College of Medicine, Gainesville, Florida 32611, USA.
McGarry
Sean V
SV
Currie
Thomas P
TP
Nickerson
David M
DM
McClellan
Steven
S
Ghivizzani
Steven C
SC
Steindler
Dennis A
DA
Gibbs
C Parker
CP
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
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