microRNA-150 inhibits human CD133-positive liver cancer stem cells through negative regulation of the transcription factor c-Myb

MicroRNAs (miRNAs) have been implicated in the maintenance of the cancer stem cell (CSC) phenotype via their ability to affect expression of genes and proteins that regulate cell proliferation and/or cell death. Thus, identification of CSC-related miRNAs would provide information for a better understanding of CSCs. Here, we compared the miRNA profiles of CD133(+) and CD133(-) primary hepatocellular carcinoma (HCC) subpopulations and found upregulation of 5 miRNAs in CD133(-) subpopulations, including hsa-miR-I50, which may be involved in maintenance of the CD133(+) liver CSC phenotype. We also show that miR-150 interacts with the 3'UTR of c-Myb mRNA and overexpression of miR-150 downregulates c-Myb protein levels. Furthermore, overexpression of miR-150 lead to a significant reduction of CD133(+) cells, accompanied by significant inhibition of cell growth and tumorsphere formation. In addition, overexpression of miR-150 induces cell cycle arrest and apoptosis in CD133(+) cells. Consistent with the outcome of cell cycle arrest and cell apoptosis, Western blotting results demonstrate that the cell cycle regulator cyclin D1 and cell survival regulator Bcl-2 are decreased in cells transfected with miR-150. Collectively, our findings demonstrate for the first time that miR-150 may be involved in liver CSC self-renewal, potentially via modulation of the downstream target c-Myb.