Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Feb 14, 2021; 27(6): 470-486
Published online Feb 14, 2021. doi: 10.3748/wjg.v27.i6.470
Demethylation of miR-34a upregulates expression of membrane palmitoylated proteins and promotes the apoptosis of liver cancer cells
Fu-Yong Li, Ting-Yong Fan, Hao Zhang, Yu-Min Sun
Fu-Yong Li, Department of Interventional Radiology, Jinan City People's Hospital, Jinan 271100, Shandong Province, China
Ting-Yong Fan, Department of Radiation Oncology, Shandong Cancer Hospital affiliated to Shandong University, Jinan 250117, Shandong Province, China
Hao Zhang, Department of Endoscopy, Shandong Cancer Hospital affiliated to Shandong University, Jinan 250117, Shandong Province, China
Yu-Min Sun, Department of Cardiology, Jinan City People's Hospital, Jinan 271100, Shandong Province, China
Author contributions: Li FY conceived the idea; Fan TY conducted the analyses; Zhang H and Sun YM provided the data; All authors contributed to the writing and revisions.
Institutional review board statement: The study was reviewed and approved by the Shandong Cancer Hospital affiliated to Shandong University.
Conflict-of-interest statement: All the Authors have no conflict of interest related to the manuscript.
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 NonCommercial (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: Ting-Yong Fan, MD, Chief Physician, Department of Radiation Oncology, Shandong Cancer Hospital affiliated to Shandong University, No. 440 Jiyan Road, Jinan 250117, Shandong Province, China. fantcwq50216@163.com
Received: October 20, 2020
Peer-review started: October 20, 2020
First decision: December 8, 2020
Revised: December 21, 2020
Accepted: December 29, 2020
Article in press: December 29, 2020
Published online: February 14, 2021
Abstract
BACKGROUND

Liver cancer is a common cancer and the main cause of cancer-related deaths worldwide. Liver cancer is the sixth most common cancer in the world. Although miR-34a and palmitoyl membrane palmitoylated protein (MPP2) are reportedly involved in various cell processes, their precise roles in liver cancer are still unclear.

AIM

To investigate the expression of micro RNA 34a (miR-34a), methylation of the miR-34a promoter and the expression of MPP2 in liver cancer cells and their related mechanisms.

METHODS

Together, 78 cases of liver cancer tissues and 78 cases of adjacent tissues were collected. The methylation degree of miR-34a promoter in liver cancer/ paracancerous tissue and liver cancer cells/normal liver cells, and the expression levels of miR-34a and MPP2 in the above samples were detected. Demethylation of liver cancer cells or transfection of liver cancer cells with miR-34a mimetic was performed. The MPP2 overexpression vector was used to transfect liver cancer cells, and the changes in proliferation, invasion, apoptosis, migration, and other biological functions of liver cancer cells after the above interventions were observed. Double luciferase reporter genes were used to detect the targeting relationship between miR-34a and MPP2.

RESULTS

Clinical samples showed that the expression levels of miR-34a and MPP2 in liver cancer tissues were lower than those in the normal tissues. The methylation degree of miR-34a promoter region in liver cancer cells was higher than that in normal liver cells. After miR-34a demethylation/mimetic transfection/MPP2 overexpression, the apoptosis of liver cancer cells was increased; the proliferation, invasion and migration capabilities were decreased; the expression levels of caspase 3, caspase 9, E-cadherin, and B-cell lymphoma 2 (Bcl-2)-associated X protein were increased; and the expression levels of Bcl-2, N-cadherin, and β-catenin were decreased. Double luciferase reporter genes confirmed that MPP2 is targeted by miR-34a. Rescue experiments showed that small interfering MPP2 could counteract the promoting effect of miR-34a demethylation on apoptosis and the inhibitory effect on cell proliferation, invasion, and migration.

CONCLUSION

miR-34a demethylation upregulates the expression level of MPP2 in liver cancer cells and promotes the apoptosis of liver cancer cells. miR-34a demethylation is a potential method for liver cancer treatment.

Keywords: Liver cancer, miR-34a, Membrane palmitoylated proteins, Methylation, Cell apoptosis, Caspase 3

Core Tip: This study confirmed the relationship of microRNA 34a (miR-34a) hypermethylation with membrane palmitoylated protein (MPP2) expression by investigating the changes of biological function and MPP2 expression level of liver cancer cells after miR-34a demethylation. miR-34a can inhibit the occurrence of liver cancer by upregulating MPP2, and its demethylation in liver cancer cells is a potential method of liver cancer treatment. In essence, miR-34a methylation is located upstream of its binding site with p53. Therefore, it is valuable to study the role of miR-34a methylation/demethylation on the expression level of upstream regulatory factors such as p53, and to explore its function in the future.