MicroRNA-325-3p contributes to colorectal carcinoma by targeting cytokeratin 18

Colorectal carcinoma (CRC) is one of the most common malignant tumors. The present study aimed to investigate a non-invasive molecular marker that can evaluate the diagnosis and potential molecular mechanism of CRC. Microarray assays and reverse transcription-quantitative PCR analysis demonstrated that microRNA (miR)-325-3p expression was significantly increased in both tissues and serum samples of patients with CRC. In addition, miR-325-3p expression in the tissues and serum was significantly associated with differentiation, TNM stage and lymph node metastasis. The results of the dual-luciferase reporter assay and western blot analysis revealed that cytokeratin 18 (CK18) is a target gene of miR-325-3p. Furthermore, treatment with transforming growth factor (TGF)-β increased miR-325-3p expression in a time-dependent manner. Conversely, TGF-β decreased CK18 expression at 48 and 72 h. Western blot analysis demonstrated that TGF-β1 significantly decreased the expression of the epithelial marker, CK18, and increased the expression of the mesenchymal markers, α-SMA and vimentin. Notably, these effects were reversed following inhibition of miR-325-3p expression. Taken together, the results of the present study suggest that miR-325-3p is a key regulator of TGF-β-induced CK18 downregulation. Thus, elevated levels of miR-325-3p is an important factor affecting epithelial-to-mesenchymal transition, and is likely to be a molecular marker in the progression of CRC and act as a potential therapeutic target.