miR-589-5p inhibits MAP3K8 and suppresses CD90 cancer stem cells in hepatocellular carcinoma.

Background: Cancer stem cells (CSCs) are important in the tumorigenesis and progression of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) play crucial roles regulating CD133 and EpCAM CSCs in HCC, although it is unclear whether miRNAs regulate CD90 CSCs in HCC.

Methods: The miRNA profiles of CD90 and CD90 HCC cells were analyzed using a miRNA microarray and quantitative real-time PCR (qRT-PCR). CSC characteristics were examined by qRT-PCR and Western blot of pluripotency-associated genes, clone and sphere formation assay, transwell migration assay, and nude mice tumorigenicity assay. miR-589-5p mimic transfection was used to overexpress miR-589-5p in vitro. The CD90 and miR-589-5p expressions of HCC samples were detected by immunohistochemistry and qRT-PCR, respectively.

Results: miR-589-5p and miR-33b-5p were down-regulated in CD90 cells. Overexpression of miR-589-5p suppressed CD90 CSC characteristics such as Oct4, Sox2 and Nanog expression, a high likelihood of forming cell spheres, high invasiveness and high tumorigenicity. Luciferase reporter assays demonstrated that miR-589-5p directly binds to the 3'-untranslated region of mitogen-activated protein kinase kinase kinase 8 (MAP3K8) mRNA, and exogenous miR-589-5p down-regulated MAP3K8 expression. In addition, siRNA inhibition of MAP3K8 also suppressed CD90 CSC characteristics, even in the absence of miR-589-5p overexpression. In HCC tissues, miR-589-5p expression was inversely correlated with CD90 expression, and high CD90 expression and low miR-589-5p expression were positively correlated with vascular invasion and recurrence and significantly decreased disease-free and overall survival by clinical analysis.

Conclusion: In HCC, miR-589-5p down-regulates the stemness characteristics of CD90 CSCs in part by silencing MAP3K8. CD90 and miR-589-5p expression predict HCC outcomes and might be novel molecular targets for HCC treatment.