Over-expressed miRNA-200b ameliorates ulcerative colitis-related colorectal cancer in mice through orchestrating epithelial-mesenchymal transition and inflammatory responses by channel of AKT2

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Our study was to explore the potential role of miRNA-200b in modulating tumorigenesis in the model of ulcerative colitis-related colorectal cancer (UCRCC) and, further, to decipher the underlying mechanisms associated with this effect. In this study, we examined a greater number of polyps or adenomas, a higher grade of epithelial dysplasia accompanied with a decrease in survival ratio in azoxymethane (AOM)/dextran sulfate sodium (DSS) model mice compared to mice treated with over-expressed miRNA-200b. Surprisingly, enforced miRNA-200b expression significantly suppressed AOM/DSS-induced up-regulation of oncologic markers including β-catenin and CD133. Independent of this, treatment with miRNA-200b obviously attenuated inflammatory responses, as indicated by down-regulating tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β) and blockade of AKT2-mediated NF-κB/IL-6/STAT3 signaling pathway. Furthermore, a simultaneous shift in epithelial-mesenchymal transition (EMT) markers such as E-cadherin and N-cadherin were observed to be increased and decreased, respectively. Coupled with the associated influence of over-expressed miRNA-200b were change in colorectal cell morphology shown by Transmission electron microscope (TEM) and a decrease in expression of rho-kinase2 (ROCK2) together with AKT2 phosphorylation (p-AKT2). Moreover, mice which were transfected with negative control of miRNA-200b possessed results that were in line with that obtained from AOM/DSS model mice. Additionally, we demonstrated that the 3′untranslated region (UTR) of AKT2 was a direct target of miRNA-200b through bioinformatics analysis and dual-luciferase assay. Collectively, these findings suggest that miRNA-200b's contribution to tumor-suppressing program was correlated with EMT and inflammatory responses in a AKT2-dependent manner.

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