• Yiying Wu, Yi Song, Yao Xiong, Xiaodong Wang, Ke Xu, Bin Han, Yang Bai, Li Li, Yuanyuan Zhang, and Liming Zhou.
• Department of Pharmacology, School of Pharmacy, Chengdu Medical College, Chengdu, China.
• Cell. Physiol. Biochem. 2017 Jan 1; 43 (3): 945-958.

Background/AimsMicroRNA-21 (miR-21) has been demonstrated to play an important role in carcinogenesis; however, its mechanism of action in colorectal cancer (CRC) has not been fully elucidated. The aim of the present study was to explore the oncogenic function of miR-21 and its molecular mechanism in CRC.MethodsA total of 105 paired tumor and tumor-adjacent normal tissue specimens from CRC patients and two CRC cell lines (HCT-116 and SW480) were studied. The protein and mRNA expression levels of PTEN and miR-21 were examined using western blot analysis and real-time reverse transcription-PCR (qRT-PCR). Furthermore, we transfected CRC cells with different combinations of ectopic-expression vector or shRNA expression vector of miR-21 and phosphatase and tensin homolog (PTEN) to modulate the expression levels of miR-21 and PTEN respectively, and then analyzed the phenotypic alterations of CRC cells. Tumorigenesis was also evaluated by xenografting HCT-116 cells into nude mice.ResultsIn this study, we showed that miR-21 expression was significantly up-regulated in CRC compared to that in normal tissues. Patients with advanced Tumor-Node-Metastasis (TNM) stage, lymph node metastasis, local invasion and higher serum carcinoembryonic antigen (CEA) levels displayed significantly high expression of miR-21. The PTEN protein level in CRC tissues and cells was inversely correlated with miR-21 expression. Furthermore, the transfection of CRC cells with pre-miR-21 could inhibit apoptosis and promote cellular proliferation, invasion, cell cycle progression and growth of xenografts in nude mice, whereas the transfection of miR-21-specific shRNA resulted in the opposite phenomena. In addition, silencing or elevating PTEN protein could partially reverse the effect of miR-21-specific shRNA or pre-miR-21 on apoptosis, cell cycle distribution, and invasion of CRC cells. Moreover, over-expression or knockdown of miR-21 altered the protein expression of PTEN and phosphorylated Akt (p-AKT).ConclusionmiR-21 can modulate the malignant phenotypes such as proliferation, anti-apoptosis, cell cycle progression and invasion of CRC cells by down-regulating PTEN protein expression. The results of study might improve our understanding of the regulatory mechanism of miR-21 and provide useful targets and approaches for the clinical diagnosis and therapy of CRC.© 2017 The Author(s). Published by S. Karger AG, Basel.

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