Basic Study
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 14, 2019; 25(46): 6713-6727
Published online Dec 14, 2019. doi: 10.3748/wjg.v25.i46.6713
Aberrant methylation of secreted protein acidic and rich in cysteine gene and its significance in gastric cancer
Shuai Shao, Nuo-Ming Zhou, Dong-Qiu Dai
Shuai Shao, Nuo-Ming Zhou, Dong-Qiu Dai, Department of Gastrointestinal Surgery, the Fourth Affiliated Hospital of China Medical University, Shenyang 110032, Liaoning Province, China
Author contributions: Dai DQ designed this study; Shao S and Zhou NM performed the research and conducted the data analysis; Shuai S wrote the article; All authors read and approved the final version.
Supported by the Natural Science Foundation of Liaoning Province, No. 201602817.
Institutional review board statement: The data of gastric cancer we analyzed in this research are all from The Fourth Affiliated Hospital of China Medical University. And our research had been approved by The Fourth Affiliated Hospital of China Medical University Clinical Research Ethics Committee.
Conflict-of-interest statement: All authors declare that there is no conflict of interest related to this study.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that 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, Chief Doctor, Professor, Surgical Oncologist, Department of Gastroenterological Surgery, the Fourth Affiliated Hospital of China Medical University, 4 Chongshan Road, Shenyang 110032, Liaoning Province, China. daidq63@163.com
Telephone: +86-24-62043110 Fax: +86-24-62043110
Received: August 13, 2019
Peer-review started: August 13, 2019
First decision: September 10, 2019
Revised: September 28, 2019
Accepted: October 22, 2019
Article in press: October 22, 2019
Published online: December 14, 2019
Processing time: 122 Days and 22 Hours
Abstract
BACKGROUND

Aberrant methylation in DNA regulatory regions could downregulate tumor suppressor genes without changing the sequences. However, our knowledge of secreted protein acidic and rich in cysteine (SPARC) and its aberrant methylation in gastric cancer (GC) is still inadequate. In the present research, we performed fundamental research to clarify the precise function of methylation on SPARC and its significance in GC.

AIM

To investigate promoter methylation and the effects of the SPARC gene in GC cells and tissues and to evaluate its clinical significance.

METHODS

Plasmids that overexpressed the SPARC gene were transfected into human GC BGC-823 cells; non-transfected cells were used as a control group (NC group). Quantitative real-time polymerase chain reaction and western blotting (WB) were then used to detect the expression of SPARC. Methylation-specific polymerase chain reaction was executed to analyze the gene promoter methylation status. Cell viability was measured by the cell counting kit-8 assay. The migration and invasion ability of cells were detected by scratch assays and transwell chamber assays, respectively. Cell cycle events and apoptosis were observed with a flow cytometer.

RESULTS

The expression of SPARC mRNA in GC tissues and cells was significantly lower and showed differing degrees of hypermethylation, respectively, than that in normal adjacent tissues and control cells. Treatment with 5-Aza-2’-deoxycytidine (5-Aza-Cdr) was able to restore the expression of SPARC and reverse promoter hypermethylation. Overexpression of the SPARC gene significantly inhibited proliferation, migration, and invasion of GC cells, while also causing cell cycle arrest and apoptosis; the NC group exhibited the opposite effects.

CONCLUSION

This study demonstrated that SPARC could function as a tumor suppressor and might be silenced by promoter hypermethylation. Furthermore, in GC cells, SPARC inhibited migration, invasion, and proliferation, caused cell cycle arrest at the G0/G1 phase, and promoted apoptosis.

Keywords: Gastric cancer; Secreted protein acidic and rich in cysteine; Hypermethylation; Clinicopathological features; Tumor suppressor gene

Core tip: We identified four gastric cancer (GC) cell lines and 66 paired tissues using quantitative real-time polymerase chain reaction, western blotting, and methylation-specific polymerase chain reaction. Correlation analysis between expression and clinicopathological features revealed that low expression levels of secreted protein acidic and rich in cysteine (SPARC) and high levels of methylation in GC tissues were associated with poor clinical features and a poor prognosis (high TNM stage and poor differentiation grade). The restoration of SPARC suppressed GC cell proliferation, migration, and invasion, arrested the cell cycle, and increased apoptosis. Our study found that SPARC represents a potential target for treating GC individuals.