Clinical and Translational Research
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Jul 26, 2020; 8(14): 2917-2929
Published online Jul 26, 2020. doi: 10.12998/wjcc.v8.i14.2917
Identification of APEX2 as an oncogene in liver cancer
Ru Zheng, Heng-Liang Zhu, Bing-Ren Hu, Xiao-Jiao Ruan, Hua-Jie Cai
Ru Zheng, Bing-Ren Hu, Xiao-Jiao Ruan, Hua-Jie Cai, Department of General Surgery, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, Zhejiang Province, China
Heng-Liang Zhu, Department of General Surgery, Shenzhen University General Hospital, Shenzhen 518107, Guangdong Province, China
Author contributions: Cai HJ conceived and designed the study; Zheng R conducted the experiments and data analysis; Zhu HL performed the statistical analysis; Hu BR and Ruan XJ wrote the manuscript; all authors reviewed and approved the final manuscript.
Supported by Wenzhou Science and Technology Bureau, No. Y20180147.
Institutional review board statement: This study was reviewed and approved by the Ethics Committee of the First Affiliated Hospital of Wenzhou Medical University.
Informed consent statement: Patients were not required to give informed consent to this study because the analysis used anonymous clinical data and the confidentiality of the patients was preserved.
Conflict-of-interest statement: All authors have no conflict of interests to declare.
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: Hua-Jie Cai, MD, Associate Chief Physician, Department of General Surgery, The First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang Street, Ouhai District, Wenzhou 325000, Zhejiang Province, China. huajie.cai@outlook.com
Received: April 17, 2020
Peer-review started: April 17, 2020
First decision: May 26, 2020
Revised: May 27, 2020
Accepted: June 12, 2020
Article in press: June 12, 2020
Published online: July 26, 2020
ARTICLE HIGHLIGHTS
Research background

Hepatocellular carcinoma (HCC) is a most malignant tumor; the deficiency of drugs is a critical factor for poor prognosis. Thus, the identification of novel drug targets is significant. APEX1 was reported as a tumor promoter in HCC. However, the expression and clinical significance of APEX2 in HCC are still unclear.

Research motivation

This study was to evaluate the role of APEX2 in HCC and identify the potential mechanisms associated with APEX2.

Research objectives

This study aimed to evaluate the levels of APEX2 in the HCC, the association between APEX2 and patients’ prognosis, and the potential regulatory mechanisms of APEX2.

Research methods

We performed pan-cancer analysis about APEX1 and APEX2 in TIMER, and included the GEO datasets to confirm the APEX2 expression in liver tumor and adjacent normal tissues. Then, the clinical significance of APEX2 was confirmed with the Kaplan-Meier method. Next, we conducted the gene enrichment analysis of APEX2 with the GSEA method, and subjected the KEGG pathways to show the potential signaling pathways. The correlation between APEX2 and other genes was detected in the GEPIA2 tool. For in vitro studies, we performed qPCR to analyze the level of relative gene expression. Then, the knockdown assay was conducted using small interfering RNA. The cell viability was tested with CCK-8. The promoter activity was detected by dual-luciferase reporter assay.

Research results

The pan-cancer analysis showed that APEX1 and APEX2 were over-expressed in some cancers, especially in HCC. GSE14520, GSE64041 and GSE22058 datasets analysis confirmed that APEX2 was over-expressed in HCC. And the 5-year survival analysis showed that the patients with higher APEX2 expression had a lower survival rate, even in those with AJCC-T1 in the early stage. We also confirmed the poor prognosis prediction of APEX2 in the liver cancers with or without hepatitis virus infection. The gene enrichment analysis showed that APEX2 was enriched in the regulation of chromosome segregation and DNA replication. And the most significant pathways associated with APEX2 were cell cycle pathways and MYC target. The Pearson correlation analysis showed that APEX2 was positively correlated with CCNB1 and MYC. The over-expression of APEX2 in HCC was also confirmed in the liver cancer cell lines and normal LO2 liver cells. And knockdown of APEX2 could inhibit the cell viability of HCCLM3 cells, and decrease CCNB1 and MYC expression and promoter activity.

Research conclusions

Our findings confirmed the over-expression of APEX2 in the HCC, which could serve as a poor prognostic marker. The mechanism regulation analysis identified that APEX2 was closely involved in the biological process of chromosome segregation and DNA replication, which was positively associated with pro-oncogenic pathways.

Research perspectives

In this study, we identified APEX2 as an oncogenic gene in HCC, the clinical significance of which was also confirmed with the public tumor database. And in the next work, the association between APEX2 and clinical-pathological features should be included to further evaluate the clinical significance of APEX2. Another critical task is to study the regulation of APEX2 in the cell cycle, and the analysis of the signaling pathways involving APEX2 in HCC.