Expression of CD133 confers malignant potential by regulating metalloproteinases in human hepatocellular carcinoma

Background 82 Aims: Although CD133 expression is identified as a cancer stem cell marker of hepatocellular carcinoma (HCC), the detailed characteristics of HCC cells expressing CD133 remain unclear. Methods: We examined the malignant characteristics of CD133-expressing HCC cells. Results: CD133-expressing cells could be detected with low frequency in 5 HCC tissues. We derived two different HCC cell lines by (1) transfection of CD133 siRNA in PLC/PRF/5 cells (CD133si-PLC/PRF/5), and (2) by a magnetic cell sorting method that allowed to divide Huh7 cells into two CD133 positive (+) and negative (-) groups. CD133 knockdown in PLC/PRF/5 cells resulted in a decrease of the mRNA and protein expressions of matrix metalloproteinase (MMP)-2 and a disintegrin and metalloproteinase (ADAM)9. We next examined the malignant characteristics related to decreasing MMP-2 and ADAM9 in HCC cells. In CD133si-PLC/PRF/5 cells and CD133 Huh7 cells, invasiveness and vascular endothelial growth factor (VEGF) production, which are both related to the activity of MMP-2, were inhibited compared to CD133-expressing HCC cells. We previously demonstrated that ADAM9 protease plays critical roles in the shedding of MHC class I-related chain A (MICA) which regulates the sensitivity of tumor cells to natural killer cells (NK). Decreasing ADAM9 expression in CD133si-PLC/PRF/5 cells and CD133 Huh7 cells resulted in an increase in membrane-bound MICA and a decrease in soluble MICA production. Both CD133si-PLC/PRF/5 cells and CD133 Huh7 cells were susceptible to NK activity, depending on the expression levels of membrane-bound MICA, but CD133-expressing HCC cells were not. Conclusion: These results demonstrate that CD133 expression in HCC cells confers malignant potential which may contribute to the survival of HCC cells. (c) 2010 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.