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
Processing time: 176 Days and 22.2 Hours
ARTICLE HIGHLIGHTS
Research background

Gastric cancer (GC) is a common type of malignant tumor with poor prognosis and presents a serious threat to human health. In February 2018 , the latest statistics from the Chinese National Cancer Center showed that although the overall incidence of GC is declining, it remains second in terms of incidence among all malignancies in China, just below lung cancer. At present, there is no efficient early diagnosis and curative treatment strategy for GC. As precision medicine is the future direction in cancer therapy, it is important to identify an early diagnostic or therapeutic biomarker of GC.

Research motivation

To explore the expression pattern, biological function and potential mechanism of miRNA (miR)-320a in GC, and to determine whether miR-320a functions as an early diagnostic or therapeutic biomarker in GCaccording to its expression and biological functions.

Research objectives

miR-320a mimic and inhibitor were transfected into GC cells for bidirectional regulation of the expression level of miR-320a. The effect of miR-320a on cell viability, migration, invasion and apoptosis was determined through a series of functional experiments. These results would provide scientific evidence for clinical treatment of GC.

Research methods

Quantitative real-time polymerase chain reaction (PCR) and Western blotting were performed to determine the levels of related factors. Methylation-specific PCR was applied for analysis of methylation status of the miR-320a promoter CpG islands in GC cell lines and tissues. CCK8, flow cytometry, Transwell invasion and wound healing assays were performed to determine the effect of miR-320a on cell behavior. Dual luciferase assay was performed to identify whether pre-B-cell leukemia homeobox (PBX) 3 was the target gene of miR-320a. TargetScanHuman7.1, miRDB, microrna.org and MethPrimer were used for bioinformatics analysis. Student’s t test (two-tailed) and analysis of variance (ANOVA) were used for statistical analysis.

Research results

miR-320a was downregulated in GC, and its expression deficiency was partly due to hypermethylation of the promoter CpG islands. miR-320a overexpression inhibited cell viability, migration and invasion, and induced apoptosis through targeting PBX3 in GC cells. miR-320a functioned as a tumor suppressor in vitro. However, its biological effect in a preclinical model should be further determined.

Research conclusions

miR-320a was downregulated in GC tissues and cells, and its abnormal expression was related to GC cell behavior. We confirmed that miR-320a overexpression inhibited cell viability, migration and invasion, and induced apoptosis in GC cells. miR-320a deficiency showed the opposite results. Consistent with previous research, miR-320a functioned as a tumor suppressor. miR-320a could be a biomarker for GC diagnosis and treatment. We found that miR-320a downregulation in GC was due to the elevated methylation level of the miR-320a promoter CpG islands. The elevation was partly reversed by 5-Aza-2’-deoxycytidine and trichostatin A. In addition, PBX3 was firstly identified as the target gene of miR-320a in GC.

Research perspectives

For future research, we will focus on the related signaling pathways through which miR-320a regulates GC cell biological behaviors. Screening for related signaling pathways of GC will be performed using the Cancer Genome Atlas database, followed by related factor detection using Western blotting and quantitative real-time PCR. Activator and inhibitor for target signaling will be applied to GC cells, and cell viability, cell cycle, cell migration, invasion and apoptosis will be determined.