Upregulation of MicroRNA 18b Contributes to the Development of Colorectal Cancer by Inhibiting CDKN2B

ABSTRACT

MicroRNAs (miRNAs) exhibit aberrant expression in the initiation and progression of a variety of human cancers, including colorectal cancer (CRC). However, the exact mechanisms are not well defined. miRNA expression profiles were characterized by microarrays in CRC samples, and miRNA 18b (miR-18b) was increased significantly in tumor tissues. The expression of miR-18b was confirmed in the CRC cell lines SW480 and HCT116 and 44 clinical specimens by quantitative real-time PCR (qRT-PCR). Multiple linear regression analysis showed a strong correlation of miR-18b expression with lymph node and distant metastasis. Overexpression of miR-18b promoted cell proliferation by facilitating cell cycle progression, and knockdown of miR-18b significantly suppressed migration in CRC cells. CDKN2B was identified as a target of miR-18b by high-throughput RNA sequencing and bioinformatics. After transfection with a miR-18b mimic, expression of CDKN2B was reduced significantly in CRC cells, and the effect was restored when a miR-18b inhibitor was transfected. A luciferase assay indicated miR-18b directly binds to the 3′ untranslated region (UTR) of CDKN2B. Expression of CDKN2B was downregulated in patient cancer tissues and negatively correlated with miR-18b. In a model of ectopic expression of miR-18b and CDKN2B, CDKN2B overexpression antagonized the effects of miR-18b in vitro and in vivo. The data show that miR-18b is involved in CRC carcinogenesis through targeting CDKN2B.

KEYWORDS:

• microRNA 18b
• microRNA array
• colorectal cancer
• CDKN2B
• high-throughput RNA sequencing

ACKNOWLEDGMENTS

This project was supported by a grant from the National Natural Science Foundation of China (no. 81270468).

M.Y. and M.W. designed the project and wrote the manuscript. Y.L., X.Y., and J.Z. contributed to all experiments. Y.L. was mainly responsible for acquisition and analysis of data and writing the manuscript. M.C. carried out animal experiments. M.W. and L.L. conducted the experiments and data analysis. X.Y. and J.L. collected human tissue samples. We all read and gave our approval to the final version of the manuscript.

There were no conflicts of interest involved in this study.