Basic Study
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Oncol. Oct 15, 2019; 11(10): 842-856
Published online Oct 15, 2019. doi: 10.4251/wjgo.v11.i10.842
MicroRNA-320a suppresses tumor progression by targeting PBX3 in gastric cancer and is downregulated by DNA methylation
Yong-Shuang Li, Ying Zou, Dong-Qiu Dai
Yong-Shuang Li, Ying Zou, Dong-Qiu Dai, Department of Gastrointestinal Surgery, the Fourth Affiliated Hospital of China Medical University, Shenyang 110032, Liaoning Province, China
Author contributions: Li YS and Zou Y contributed equally to this work and should be considered as co-first authors; Li YS and Dai DQ designed the study; Li YS and Zou Y collected and analyzed the data; Li YS and Zou Y performed the experiments; all authors contributed to writing, reviewing or revising the paper; Li YS and Dai DQ submitted the final manuscript and all authors read and approved the final version; all authors agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Supported by the Natural Science Foundation of Liaoning Province, No. 201602817.
Institutional review board statement: Institutional review board approval of our hospital was obtained for this study.
Conflict-of-interest statement: All authors declare that they have no conflicts of interest.
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/
Corresponding author: Dong-Qiu Dai, MD, PhD, Professor, Department of Gastrointestinal Surgery, The Fourth Affiliated Hospital of China Medical University, No. 4 Chongshan East Road, Shenyang 110032, Liaoning Province, China. daidq63@163.com
Telephone: +86-24-62043110Fax: +86-24-62043110
Received: April 23, 2019
Peer-review started: May 7, 2019
First decision: June 4, 2019
Revised: June 19, 2019
Accepted: July 26, 2019
Article in press: July 28, 2019
Published online: October 15, 2019
Abstract
BACKGROUND

Ectopic expression of miRNAs promotes tumor development and progression. miRNA (miR)-320a is downregulated in many cancers, including gastric cancer (GC). However, the mechanism underlying its downregulation and the role of miR-320a in GC are unknown.

AIM

To determine expression and biological functions of miR-320a in GC and investigate the underlying molecular mechanisms.

METHODS

Quantitative real-time polymerase chain reaction (PCR) was used to determine expression of miR-320a in GC cell lines and tissues. TargetScanHuman7.1, miRDB, and microRNA.org were used to predict the possible targets of miR-320a, and a dual luciferase assay was used to confirm the findings. Western blotting was used to detect the protein levels of pre-B-cell leukemia homeobox 3 (PBX3) in GC cells and tissue samples. Cell Counting Kit-8 proliferation, Transwell, wound healing, and apoptosis assays were performed to analyze the biological functions of miR-320a in GC cells. Methylation-specific PCR was used to analyze the methylation level of the miR-320a promoter CpG islands. 5-Aza-2’-deoxycytidine (5-Aza-CdR) and trichostatin A (TSA) were used to treat GC cells.

RESULTS

miR-320a expression was lower in GC cell lines and tissues than in the normal gastric mucosa cell line GES-1 and matched adjacent normal tissues. miR-320a overexpression suppressed GC cell proliferation, invasion and migration, and induced apoptosis. PBX3 was a target of miR-320a in GC. The methylation level of the miR-320a promoter CpG islands was elevated and this was partly reversed by 5-Aza-CdR and TSA.

CONCLUSION

miR-320a acts as a tumor suppressor and inhibits malignant behavior of GC cells, partly by targeting PBX3. DNA methylation is an important mechanism associated with low expression of miR-320a.

Keywords: Gastric cancer, miRNA-320a, DNA methylation, Pre-B-cell leukemia homeobox 3, Tumor suppressor

Core tip: miRNA (miR)-320a functioned as a tumor suppressor and was downregulated in gastric cancer (GC). miR-320a overexpression suppressed proliferation, migration and invasion, and induced apoptosis through targeting Pre-B-cell leukemia homeobox 3 in GC cells. miR-320a depletion showed the opposite results. The potential mechanism of miR-320a deficiency in GC was the increased methylation level of the miR-320a promoter CpG islands.