Downregulation of miR‑181b inhibits human colon cancer cell proliferation by targeting CYLD and inhibiting the NF‑κB signaling pathway.

It has been reported that microRNA (miRNA/miR)‑181b plays an important role in regulating cellular proliferation, invasion and apoptosis in various tumors. However, the role of miR‑181b and its molecular mechanisms in colon cancer cells have not yet been elucidated. The present study thus aimed to investigate the mechanisms of miR‑181b targeting cylindromatosis (CYLD) to regulate the nuclear factor‑κB (NF‑κB) signaling pathway, and to determine its role in colon cancer cell proliferation and apoptosis. For this purpose, miR‑181b was overexpressed and silenced in the SW480 cell line. The cell proliferation and apoptotic rates were determined using a Cell Counting kit and colony formation assays, and Annexin V‑FITC staining, respectively. The expression levels of proteins associated with the NF‑κB signaling pathway and apoptosis were detected by western blot analysis. Furthermore, a dual luciferase assay was applied to confirm the interaction between miR‑181b and CYLD. CYLD was also overexpressed and silenced in the SW480 cell line using a CYLD overexpression plasmid and siRNA technology, respectively. Transfected cells were used for subsequent experiments. In addition, a nude mouse model was established to measure tumor volume and weight. Immunohistochemistry and a TUNEL assay were performed to detect the Ki67 levels and the cell apoptotic rate, respectively. Compared with the control group, miR‑181 silencing or CYLD overexpression significantly attenuated cell proliferation, invasion and migration, and notably increased the proportion of apoptotic cells. Furthermore, the expression levels of Bax and cleaved caspase‑3 were markedly increased, whereas those of Bcl‑2 were significantly decresaed (P<0.05). In addition, the protein expression levels of p‑p65/p65 and p‑IκBα/IκBα were significantly downregulated and upregulated, respectively (P<0.05). Consistent with the results obtained in vitro, in vivo experiments using a nude mouse model yielded similar findings. The aforementioned results indicated that miR‑181b downregulation inhibited human colon cancer cell proliferation by targeting CYLD to attenuate the activity of the NF‑κB signaling pathway.