miR-194 inhibits liver cancer stem cell expansion by regulating RAC1 pathway.

Liver cancer stem cells (CSCs) contribute to tumorigenesis, progression, drug resistance and recurrence of hepatocellular carcinoma (HCC). However, the underlying mechanism for the propagation of liver CSCs remains unclear. Herein, we observed low expression of miR-194 in chemoresistant HCC cells. A remarkable decrease of miR-194 was detected in EpCAM or CD133-positive liver CSCs and CSC-enriched hepatoma spheres. Interference miR-194 facilitated liver CSCs expansion by enhancing the self-renewal of liver CSCs. While up-regulating miR-194 inhibited liver CSCs expansion by suppressing the self-renewal of liver CSCs. Furthermore, hepatoma cells with miR-194 overexpression performed more sensitivity to sorafenib treatment. Mechanistically, functional studies found that Ras-related C3 botulinum toxin substrate 1 (RAC1) was a direct target of miR-194. Overexpression of miR-194 inhibited the expression of RAC1 in liver CSCs. Special RAC1 siRNA diminished the discrepancy in liver CSC proportion and the self-renewal capacity between miR-194 overexpression hepatoma cells and control cells, which further confirmed that RAC1 was required in miR-194-inhibited liver CSCs expansion. More importantly, downregulated expression of miR-194 was a predictor of poor prognosis of HCC patients.