Constitutive expression of Wnt/β-catenin target genes promotes proliferation and invasion of liver cancer stem cells

Wnt/beta-catenin is an important signaling pathways involved in the tumorgenesis, progression and maintenance of cancer stem cells (CSCs). In the present study, the role of Wnt/beta-catenin signaling in CSC-mediated tumorigenesis and invasion in liver CSCs was investigated. A small population of cancer stem-like side population (SP) cells (3.6%) from liver cancer samples were identified. The cells were highly resistant to drug treatment due to the enhanced expression of drug efflux pumps, such as ABC subfamily G member 2, multidrug resistance protein 1 and ATP-binding cassette subfamily B member 5. Furthermore, using TOPflash and reverse transcription-quantitative polymerase chain reaction analysis, Wnt/beta-catenin signaling and the transcriptional regulation of Wnt/beta-catenin target genes including dickkopf Wnt signaling pathway inhibitor 1, axis inhibition protein 2 and cyclin D1 were observed to be markedly upregulated in liver cancer SP cells. As a consequence, SP cells possessed infinite cell proliferation potential and the ability to generating tumor spheres. In addition, upon reducing Wnt/beta-catenin signaling, the rates of proliferation, tumor sphere formation and tumor invasion of SP cells were markedly reduced. Therefore, these data suggest that Wnt/beta-catenin signaling is a potential therapeutic target to reduce CSC-mediated tumorigenicity and invasion in liver cancer.