Basic Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 14, 2020; 26(42): 6599-6613
Published online Nov 14, 2020. doi: 10.3748/wjg.v26.i42.6599
Reactive oxygen species-induced activation of Yes-associated protein-1 through the c-Myc pathway is a therapeutic target in hepatocellular carcinoma
Yuri Cho, Min Ji Park, Koeun Kim, Sun Woong Kim, Wonjin Kim, Sooyeon Oh, Joo Ho Lee
Yuri Cho, Min Ji Park, Koeun Kim, Sun Woong Kim, Wonjin Kim, Department of Internal Medicine, CHA Gangnam Medical Center, CHA University School of Medicine, Seoul 06135, South Korea
Sooyeon Oh, Department of Internal Medicine, Chaum Life Center, CHA University School of Medicine, Seoul 06062, South Korea
Joo Ho Lee, Department of Internal Medicine, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam 13496, Bundang gu, South Korea
Author contributions: Cho Y designed and wrote the review, performed the literature research and interpretation and wrote the manuscript; Park MJ and Kim K performed the experiments and interpretation; Kim SW, Kim W, Oh S, Lee JH contributed to the review design, literature research, and supervised the review; all authors finally approved the manuscript.
Supported by the Research Supporting Program of the Korean Association for the Study of the Liver and The Korean Liver Foundation in 2017; and the National Research Foundation of Korea grant funded by the Korea government, No. 2018R1C1B6001102.
Institutional review board statement: All the experiments using human tissues were approved by the Bundang CHA Medical Center Institutional Review Board (CHAMC 2018-02-037). All the human tissues were provided by the Bundang CHA Biobank of Bundang CHA Medical Center. For the gene expression analyses, 88 surgically resected frozen HCC tissue samples and 88 nontumor liver tissue samples were analyzed. Cases were prospectively and consecutively identified at Bundang CHA Medical Center between 2012 and 2018.
Institutional animal care and use committee statement: The in vivo study protocol was approved by the Institutional Animal Care and Use Committee (IACUC-180027) of CHA University. All the in vivo surgical procedures were performed under anesthesia with 2,2,2-tribromoethanol, and all efforts were made to minimize suffering.
Conflict-of-interest statement: The authors declare that they do not have anything to disclose regarding any funding or conflict of interest with respect to this manuscript.
Data sharing statement: Dataset is available from the corresponding author at yuricho@cha.ac.kr.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
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: Yuri Cho, MD, PhD, Assistant Professor, Department of Internal Medicine, CHA Gangnam Medical Center, CHA University School of Medicine, No. 569 Nonhyon-ro, Gangnam-gu, Seoul 06135, South Korea. yuricho@cha.ac.kr
Received: June 26, 2020
Peer-review started: June 26, 2020
First decision: August 22, 2020
Revised: August 27, 2020
Accepted: September 23, 2020
Article in press: September 23, 2020
Published online: November 14, 2020
Processing time: 139 Days and 22.8 Hours
Abstract
BACKGROUND

The Hippo signaling pathway regulates organ size by regulating cell proliferation and apoptosis with terminal effectors including Yes-associated protein-1 (YAP-1). Dysregulation in Hippo pathway has been proposed as one of the therapeutic targets in hepatocarcinogenesis. The levels of reactive oxygen species (ROS) increase during the progression from early to advanced hepatocellular carcinoma (HCC).

AIM

To study the activation of YAP-1 by ROS-induced damage in HCC and the involved signaling pathway.

METHODS

The expression of YAP-1 in HCC cells (Huh-7, HepG2, and SNU-761) was quantified using real-time polymerase chain reaction and immunoblotting. Human HCC cells were treated with H2O2, which is a major component of ROS in living organisms, and with either YAP-1 small interfering RNA (siRNA) or control siRNA. To investigate the role of YAP-1 in HCC cells under oxidative stress, MTS assays were performed. Immunoblotting was performed to evaluate the signaling pathway responsible for the activation of YAP-1. Eighty-eight surgically resected frozen HCC tissue samples and 88 nontumor liver tissue samples were used for gene expression analyses.

RESULTS

H2O2 treatment increased the mRNA and protein expression of YAP-1 in HCC cells (Huh-7, HepG2, and SNU-761). Suppression of YAP-1 using siRNA transfection resulted in a significant decrease in tumor proliferation during H2O2 treatment both in vitro and in vivo (both P < 0.05). The oncogenic action of YAP-1 occurred via the activation of the c-Myc pathway, leading to the upregulation of components of the unfolded protein response (UPR), including 78-kDa glucose-regulated protein and activating transcription factor-6 (ATF-6). The YAP-1 mRNA levels in human HCC tissues were upregulated by 2.6-fold compared with those in nontumor tissues (P < 0.05) and were positively correlated with the ATF-6 Levels (Pearson’s coefficient = 0.299; P < 0.05).

CONCLUSION

This study shows a novel connection between YAP-1 and the UPR through the c-Myc pathway during oxidative stress in HCC. The ROS-induced activation of YAP-1 via the c-Myc pathway, which leads to the activation of the UPR pathway, might be a therapeutic target in HCC.

Keywords: Hepatocellular carcinoma; Yes-associated protein-1; C-Myc; Reactive oxygen species; Unfolded protein response; Activating transcription factor-6

Core Tip: We found a novel connection between Yes-associated protein-1 (YAP-1) and the unfolded protein response (UPR) through the c-Myc pathway during oxidative stress in hepatocellular carcinoma (HCC). As the Hippo pathway and c-Myc pathway share many important functions, including the regulation of growth, death and survival in cells and the regulation of stress resistance and life spans in organisms, we speculate that the interaction between YAP-1 and c-Myc is a point of convergence that allows HCC proliferation. The reactive oxygen species-induced activation of YAP-1 via the c-Myc pathway, which leads to the activation of the UPR pathway, might be a therapeutic target in HCC.