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-150, 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.