Numb, an endocytic adaptor, is a known cell fate determinant that participates in asymmetric cell division. The present study aimed to explore the potential roles of Numb in hepatocarcinogenesis. Numb expression was investigated in hepatocellular carcinomas (HCC) with reverse transcription-quantitative polymerase chain reaction and immunohistochemical examination; its association with the prognosis of HCC patients was analyzed. In addition, the effects of Numb deletion on proliferation of HCC cells and its relevant molecules were evaluated in Huh7 and HepG2 cells. Numb overexpression was observed in 62% of adjacent non-tumor tissues and 46% of tumor tissues. Overexpression of Numb in HCC was associated with histological grade, portal vein invasion and the number of tumors (P=0.001, 0.022 and 0.034 respectively). Multivariate analysis revealed that Numb expression was an independent prognostic indicator of HCC patients. Methylation of the Numb promoter contributed to hepatocarcinogenesis. In vitro assays demonstrated that Numb silencing resulted in inhibition of cell proliferation, induction of apoptosis, down-regulation of cyclin-dependent protein kinase 4 (CDK4) and S-phase kinase-associated protein 2 (SKP2), and upregulation of Bcl-2 homologous antagonist/killer (BAK) and cyclin-dependent kinase inhibitor 1 (p21). The present study suggests that downregulation of Numb inhibits colony formation and cell proliferation, induces apoptosis of HCC cells and independently predicts the poor prognosis of HCC patients. Thus, Numb has a potential role in the development and progression of HCC.
Abstract. Aplysia ras homolog I (ARHI) acts as a tumor suppressor in certain cancer cells. However, the role of ARHI in colon cancer development has not previously been reported. The present study aimed to investigate the functional role of ARHI in colon cancer focusing on the aspect of metastasis. Furthermore, the molecular mechanism underlying its function was explored. The present study detected the expression of ARHI in a human colon epithelial cell line and colon cancer cell lines using reverse transcription-quantitative polymerase chain reaction and western blotting analysis. It was demonstrated that ARHI expression was significantly downregulated in colon cancer cell lines compared with the normal colon epithelial cell line (P<0.05). An ARHI-pcDNA3.1 plasmid was transfected into HCT116 cells to overexpress ARHI. The number of invaded cells and the adhesive ability were significantly decreased in the ARHI overexpression group compared with the control group, as determined by cell invasion and adhesion assays (P<0.05). Furthermore, ARHI overexpression led to increased mRNA and protein expression levels of E-cadherin, and decreased mRNA and protein expression levels of N-cadherin and vimentin. Wnt/β-catenin signaling was suppressed in HCT116 cells overexpressing ARHI. Lithium chloride, a wnt/β-catenin signaling activator, was able to attenuate the effect of ARHI on HCT116 cell invasion and adhesion. In addition, the effect of ARHI on epithelial-mesenchymal transition (EMT) in HCT116 cells was reversed by the activation of wnt/β-catenin signaling. In conclusion, the present study provided novel evidence that ARHI could inhibit colon cancer cell invasion and adhesion through suppressing EMT, and these effects were achieved, at least partially, via the suppression of the wnt/β-catenin signaling pathway. The present findings may help in developing novel therapeutic approaches for colon cancer.
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