Identification and characterization of cancer stem cells in ovarian yolk sac tumors.

Recent evidence supports the cancer stem cell theory, that is, that malignant tumors arise from cells termed cancer stem cells or tumor-initiating cells that have the ability to self-renew and are responsible for maintaining the tumor. Cells with marked tumor-initiating capacity have recently been identified in a number of solid tumors. CD133 (PROM1, human prominin-1) has been used as a marker to detect stem cells (progenitor cells) and cancer stem cells (tumor-initiating cells) in various tissues. Ovarian yolk sac tumors (YSTs) are rare and highly malignant. The present study was designed to evaluate the tumor-forming ability of CD133(+) cells in ovarian YST cell lines and to examine the characteristics of CD133(+) cells, such as cell growth and invasiveness. Our data suggest ovarian YST to be maintained by a rare fraction of cancer stem-like cells that express the cell surface marker CD133.