Cancer stem cells (CSCs) form a very rare population within tumors and possess the ability to proliferate and self-renew indefinitely. The cluster of differentiation (CD) 133+ ovarian CSCs (OCSCs) have been identified recently and their clinical implications are about to be clarified. In this context, we use the CD133 antigen as a marker of OCSCs in OVCAR3 cells and show that microRNAs (miRNAs) are aberrantly expressed in this subpopulation. The OCSCs in the OVCAR3 cell line were identified by the monoclonal mouse anti-CD133-1 antibody (clone CD133). Microarray and real-time reverse transcription-polymerase chain reaction (RT-PCR) analyses were used to identify miRNAs with altered expression in CD133+ cells. The expression levels of dysregulated miRNAs, namely, miR-204, miR-206, miR-223, miR-9, miR-100, and miR-200c, were examined using TaqMan PCR. The RNA and protein levels of stem cell-specific genes were examined by real-time RT-PCR and western blot analyses. Our results of microarray and real-time RT-PCR analyses revealed distinct miRNA expression profiles between CD133+ and CD133− OVCAR3 cells. The expression of stem cell-specific genes, namely, Oct3/4, Sox2, and Nanog, was higher in CD133+ cells than in CD133− cells while that of FoxD3, was lower in CD133+ cells than in CD133− cells. In conclusion, our data indicate that CD133 expression defines a tumor-initiating subpopulation of cells in the OVCAR3 cell line. The overall miRNA expression profile of CD133+ OVCAR3 cells was clearly distinct from that of CD133− OVCAR3 cells, indicating that miRNAs are involved in the development of this neoplasia and may serve as pertinent chemotherapeutic targets.

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