Dual Effect of Taxifolin on ZEB2 Cancer Signaling in HepG2 Cells.

Polyphenols, secondary metabolites of plants, exhibit different anti-cancer and cytoprotective properties such as anti-radical, anti-angiogenic, anti-inflammation, or cardioprotective. Some of these activities could be linked to modulation of miRNAs expression. MiRNAs play an important role in posttranscriptional regulation of their target genes that could be important within cell signalling or preservation of cell homeostasis, e.g., cell survival/apoptosis. We evaluated the influence of a non-toxic concentration of taxifolin and quercetin on the expression of majority human miRNAs via Affymetrix GeneChip™ miRNA 3.0 Array. For the evaluation we used two cell models corresponding to liver tissue, Hep G2 and primary human hepatocytes. The array analysis identified four miRNAs, miR-153, miR-204, miR-211, and miR-377-3p, with reduced expression after taxifolin treatment. All of these miRNAs are linked to modulation of ZEB2 expression in various models. Indeed, ZEB2 protein displayed upregulation after taxifolin treatment in a dose dependent manner. However, the modulation did not lead to epithelial mesenchymal transition. Our data show that taxifolin inhibits Akt phosphorylation, thereby diminishing ZEB2 signalling that could trigger carcinogenesis. We conclude that biological activity of taxifolin may have ambiguous or even contradictory outcomes because of non-specific effect on the cell.

MiRNA-206 inhibits proliferation of renal clear cell carcinoma by targeting ZEB2.

OBJECTIVE: The purpose of this study was to investigate the effect of microRNA-206 on the malignant progression of renal clear cell carcinoma (RCC). In addition, whether microRNA-206 could regulate ZEB2 expression and the underlying mechanisms was also explored. PATIENTS AND METHODS: Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed to examine microRNA-206 level in 46 tumor tissue specimens and adjacent ones of RCC patients. Also, the relationship between microRNA-206 expression and clinical indicators of RCC was analyzed. The negative control (NC) and microRNA-206 mimics were transfected into RCC cell lines, and the transfection efficiency was verified by qRT-PCR. The effects of microRNA-206 on the proliferation and apoptosis of RCC cells were analyzed by cell counting kit-8 (CCK-8), clone formation, and flow cytometry assays. Finally, the regulation of microRNA-206 on the downstream gene ZEB2 was indicated by Western Blot and cell recovery experiments. RESULTS: qRT-PCR results showed that the expression level of microRNA-206 in tumor tissue samples of RCC patients was remarkably lower than that in adjacent normal tissues, and the difference was statistically significant. Meanwhile, compared with patients with high expression of microRNA-206, the pathological stage of patients with low expression of microRNA-206 was higher, and the overall survival rate was lower. In the RCC cell lines (Caki-1 and Caki-2), the cell proliferation ability of the microRNA-206 overexpression group was remarkably weakened, while the cell apoptosis rate was oppositely enhanced when compared with the NC group. In addition, this study demonstrated that ZEB2 expression was remarkably increased in RCC cells as well as tissues and was negatively correlated with microRNA-206 expression. At the same time, microRNA-206 mimics was found remarkably reduced in the expression of proteins in ZEB2-related signaling pathway, including ZEB2, ß-catenin, cyclinD1, c-Myc, MMP-2, and MMP-9. In the cell reverse experiment, the overexpression of ZEB2 was found to be able to counteract the impact of microRNA-206 mimics on RCC cell proliferation and apoptosis and thus, participated in the malignant progression of RCC. CONCLUSIONS: This study revealed that microRNA-206 was remarkably associated with the pathological stage and poor prognosis of RCC patients. In addition, microRNA-206 might inhibit the malignant progression of RCC by regulating the targeted ZEB2.