Potential Role of CD133 Expression in the Susceptibility of Human Liver Cancer Stem-Like Cells to TRAIL

Hepatocellular carcinoma (HCC) is one of the most common malignancies, with a poor prognosis and high recurrence rate. In the present study, we identified CD133, one of the markers of cancer stem cells, as a novel molecular target of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In four human HCC cell lines established from primary HCC tumors, we found that CD133-high human liver cancer stem-like cells (CD133(hi)) derived from the SNU-475 cell line were highly susceptible to TRAIL compared to other HCC cell lines with a small population of CD133. CD133(hi) SNU-475 cells showed upregulation of TRAIL receptor DR5 and stemness-related genes such as c-Myc and ABC transporters compared to their CD133-low (CD133(lo)) cells. Hypersensitivity of CD133(hi) cells to TRAIL was associated with c-Myc-mediated upregulation of DR5 and downregulation of c-FLIP(L) in the cells. Knockdown of CD133 expression in CD133(hi) cells resulted in the downregulation of c-Myc, and depletion of c-Myc caused a decrease in the cell surface expression of DR5 and an increase in the expression of c-FLIP(L) and, consequently, attenuated TRAIL-induced cytotoxicity and apoptosis of CD133(hi) cells. These results suggest that TRAIL may provide a new strategy for CD133(hi) CSCs of HCC-targeted therapies and, potentially, for therapies of other CD133-expressing types of cancer.