CD133 expression in osteosarcoma and derivation of CD133+ cells

Cluster of differentiation 133 (CD133) is recognized as a stem cell marker for normal and cancerous tissues. Using cell culture and real-time fluorescent polymerase chain reaction, CD133 expression was analyzed in osteosarcoma tissue and Saos-2 cell lines. In addition, cancer stem cell-related gene expression in the Saos-2 cell line was determined to explore the mechanisms underlying tumorigenesis and high drug resistance in osteosarcoma. CD133(+) cells were found to be widely distributed in various types of osteosarcoma tissue. Following cell culture, cells entered the G(2)/M and S cell cycle stages from G(0)/G(1). Levels of CD133(+) cells decreased to normal levels rapidly over the course of cell culture. Colony forming efficiency was higher in the CD133(+) compared with the CD133(-) subpopulation of Saos-2 cells. Expression levels of stem cell-related genes, including multidrug resistance protein 1 (MDR1) and sex determining region Y-box 2 (Sox2) in the CD133(+) subpopulation of cells were found to be significantly higher compared with the CD133(-) subpopulation. These observations indicate that CD133(+) Saos-2 cells exhibit stem cell characteristics, including low abundance, quiescence and a high potential to undergo differentiation, as well as expression of key stem cell regulatory and drug resistance genes, which may cause osteosarcoma and high drug resistance.