Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Oncol. Jul 15, 2016; 8(7): 532-542
Published online Jul 15, 2016. doi: 10.4251/wjgo.v8.i7.532
MicroRNA-320 family is downregulated in colorectal adenoma and affects tumor proliferation by targeting CDK6
Toshihiro Tadano, Yoichi Kakuta, Shin Hamada, Yosuke Shimodaira, Masatake Kuroha, Yoko Kawakami, Tomoya Kimura, Hisashi Shiga, Katsuya Endo, Atsushi Masamune, Seiichi Takahashi, Yoshitaka Kinouchi, Tooru Shimosegawa
Toshihiro Tadano, Yoichi Kakuta, Shin Hamada, Yosuke Shimodaira, Masatake Kuroha, Yoko Kawakami, Tomoya Kimura, Hisashi Shiga, Katsuya Endo, Atsushi Masamune, Tooru Shimosegawa, Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan
Seiichi Takahashi, Community Gastroenterology (Iwaki Kyoritsu Hospital), Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan
Yoshitaka Kinouchi, Health Administration Center, Center for the Advancement of Higher Education, Tohoku University, Sendai 980-8574, Japan
Author contributions: Takahashi S, Kinouchi Y and Shimosegawa T designed the research; Tadano T, Shimodaira Y, Kuroha M, Kawakami Y, Kimura T, Shiga H and Endo K performed the experiments; Kakuta Y, Hamada S and Masamune A analyzed data; Tadano T and Kakuta Y wrote the paper.
Institutional review board statement: This study was reviewed and approved by the ethics committee and the institutional review board at the Tohoku University Hospital (No. 2014-1-818).
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Toshihiro Tadano, MD, Division of Gastroenterology, Tohoku University Graduate School of Medicine, 1-1 Seiryo, Aoba, Sendai, 980-8574, Japan. md465719@med.tohoku.ac.jp
Telephone: +81-22-7177171 Fax: +81-22-7177177
Received: February 15, 2016
Peer-review started: February 17, 2016
First decision: March 9, 2016
Revised: March 19, 2016
Accepted: April 7, 2016
Article in press: April 12, 2016
Published online: July 15, 2016
Abstract

AIM: To investigate the microRNA (miRNA) expression during histological progression from colorectal normal mucosa through adenoma to carcinoma within a lesion.

METHODS: Using microarray, the sequential changes in miRNA expression profiles were compared in colonic lesions from matched samples; histologically, non-neoplastic mucosa, adenoma, and submucosal invasive carcinoma were microdissected from a tissue sample. Cell proliferation assay was performed to observe the effect of miRNA, and its target genes were predicted using bioinformatics approaches and the expression profile of SW480 transfected with the miRNA mimics. mRNA and protein levels of the target gene in colon cancer cell lines with a mimic control or miRNA mimics were measured using qRT-PCR and Western blotting. The expression levels of miRNA and target gene in colorectal tissue samples were also measured.

RESULTS: Microarray analysis identified that the miR-320 family, including miR-320a, miR-320b, miR-320c, miR-320d and miR-320e, were differentially expressed in adenoma and submucosal invasive carcinoma. The miR-320 family, which inhibits cell proliferation, is frequently downregulated in colorectal adenoma and submucosal invasive carcinoma tissues. Seven genes including CDK6 were identified to be common in the results of gene expression array and bioinformatics analyses performed to find the target gene of the miR-320 family. We confirmed that mRNA and protein levels of CDK6 were significantly suppressed in colon cancer cell lines with miR-320 family mimics. CDK6 expression was found to increase from non-neoplastic mucosa through adenoma to submucosal invasive carcinoma tissues and showed an inverse correlation with miR-320 family expression.

CONCLUSION: MiR-320 family affects colorectal tumor proliferation by targeting CDK6, plays important role in its growth, and is considered to be a biomarker for its early detection.

Keywords: CDK6, Colorectal cancer, MiR-320 family, Colorectal adenoma, Laterally spreading type

Core tip: We investigated for the first time the sequential changes of miRNA expression profiles in colonic lesions from matched samples; histologically, non-neoplastic mucosa, adenoma, and submucosal invasive carcinoma were microdissected from a tissue sample. We have shown that the miR-320a, miR-320b, miR-320c, miR-320d are downregulated from colorectal adenoma and miR-320e is downregulated from colorectal submucosal carcinoma tissue and the miR-320 family suppresses tumor proliferation by targeting CDK6. The miR-320 family may play an important role in the growth of colorectal tumors and can be considered as a biomarker for the early detection of colorectal tumors.