Possible involvement of CD133 in the appearance of cancer stem cells in hepatoma cells

Recent evidences in stem cell biology suggest that tumors contain a hierarchy of heterogeneous cell population in which cancer stem cells (CSCs) exist in the top and confer the maintenance ability of tumor formation on transformed cells. In this study, to elucidate the relationship between the expression level of CD133 and appearance of CSCs in hepatoma cells, we performed the expression analysis of CD133, which is a stem cell-specific cell surface marker and is utilized for detection of CSCs in various tumors. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemical analyses indicated that CD 133positive cells existed with high frequency in aflatoxin Bsub(1)-induced rat hepatoma K2 and human hepatoma Huh7 cells. Down-regulation of CD133 in Huh7 cells with the micro-interfering RNA (miRNA) suppressed the expression of ATP-binding cassette transporter ABCG2 gene, which is specifically expressed in stem cells and implicated in cell growth and multidrug resistance of tumors. Thus, these results suggest that the deregulated expression of CD133 in hepatoma cells takes part in the generation of CSCs at least in part.