Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Mar 27, 2021; 13(3): 343-361
Published online Mar 27, 2021. doi: 10.4254/wjh.v13.i3.343
BIR repeat-containing ubiquitin conjugating enzyme (BRUCE) regulation of β-catenin signaling in the progression of drug-induced hepatic fibrosis and carcinogenesis
Chrystelle L Vilfranc, Li-Xiao Che, Krushna C Patra, Liang Niu, Olugbenga Olowokure, Jiang Wang, Shimul A Shah, Chun-Ying Du
Chrystelle L Vilfranc, Li-Xiao Che, Krushna C Patra, Chun-Ying Du, Department of Cancer Biology, University of Cincinnati, Cincinnati, OH 45267, United States
Liang Niu, Department of Environmental and Public Health Sciences, University of Cincinnati, Cincinnati, OH 45267, United States
Olugbenga Olowokure, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, United States
Jiang Wang, Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH 45267, United States
Shimul A Shah, Department of Surgery, University of Cincinnati, Cincinnati, OH 45267, United States
Author contributions: Vilfranc CL, Che LX, Shah SA and Du CY performed study concept and design; Vilfranc CL and Che LX performed acquisition of data, analysis and interpretation of data; Vilfranc CL performed drafting of the manuscript, revision of the manuscript with important intellectual contribution; Che LX performed RNA-seq transcriptome analysis and edited the manuscript; Patra KC performed intellectual contribution, technical and material support, analysis and interpretation of data; Niu L support with RNA-seq analysis; Olowokure O performed study concept, intellectual contribution; Wang J performed intellectual contribution, histopathological design, analysis and interpretation of clinical data; Shah SA performed intellectual contribution, mentorship to CLV; Du CY performed critical revision of the manuscript, obtained funding, study supervision and manuscript revisions.
Supported by NIH (Du CY), No. R21CA241025-01; NIH (Du CY), No. RO1CA158323; NCI RO1 Diversity Supplement (Du CY), No. R01CA158323-05S; National Center for Advancing Translational Sciences of the National Institutes of Health (Du CY), No. 2UL1TR001425-05A1; University of Cincinnati Center for Environmental Genetics-NIH/NIEHS Award (Du CY), No. P30 ES006096; Pathways to Cancer Therapeutics T32 (Du CY and Vilfranc CL), No. CA117846-12.
Institutional animal care and use committee statement: All animal experiments were performed in accordance with guidelines approved by our Institutional Animal Care and Use Committee.
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
Data sharing statement: No additional data are available.
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:
Corresponding author: Chun-Ying Du, PhD, Associate Professor, Department of Cancer Biology, University of Cincinnati, 3125 Eden Avenue Room # 3216, Cincinnati, OH 45267, United States.
Received: December 12, 2020
Peer-review started: December 12, 2020
First decision: January 7, 2021
Revised: January 15, 2021
Accepted: March 8, 2021
Article in press: March 8, 2021
Published online: March 27, 2021
Research background

BIR repeat-containing ubiquitin-conjugating enzyme (BRUCE) is a known ubiquitin conjugase/Ligase hybrid that has been shown to inhibit apoptosis, regulate efficient DNA repair, and most recently promote tumor suppression in the liver. Our group previously showed that upon liver injury with diethylnitrosamine (DEN), loss of hepatic BRUCE promoted fibrosis and exacerbated hepatocellular carcinoma (HCC) development in mice.

Research motivation

About 80% of HCCs develop in fibrotic or cirrhotic livers, demonstrating the importance of understanding liver fibrosis as a factor contributing to hepatic malignancy. Identifying mechanisms that can regulate both fibrosis and HCC development simultaneously provides the possibility of opening therapeutic windows for treating fibrosis and HCC. Considering that over 50% of human HCCs have aberrant β-catenin mutations, targeting the Wnt/β-catenin has shown much promise. The key upstream regulators of this pathway that suppress fibrosis and HCC development remain elusive.

Research objectives

The objective of this study was to evaluate the mechanisms of BRUCE in inhibiting hepatic fibrosis and HCC upon liver injury induction.

Research methods

Male C57/BL6/J control mice [loxp/Loxp; albumin-cre (Alb-cre)-] and BRUCE Alb-Cre KO mice (loxp/Loxp; Alb-Cre+) were injected with a single dose of DEN at postnatal day 15. Mice were sacrificed at various time points to examine liver disease progression and liver biopsies were used in the analyses of the proposed mechanism.

Research results

Based on the exacerbation of fibrosis and HCC phenotypes observed in the liver-specific BRUCE knockout (LKO) mice that we previously reported, we hypothesized that, “the onset of fibrosis and tumorigenesis are likely earlier events in LKO mice”. In the present study, we found that upon DEN-induction, BRUCE LKO livers developed fibrosis as early as after 6 mo of exposure. Additionally, the LKO mice developed tumors as early as 8-months after exposure compared to the WT tumor onset after 10 mo of DEN exposure. Furthermore, we observed increased accumulation of β-catenin, including its activity in LKO liver samples. The phosphorylation of β-catenin was determined by measuring nuclear levels of total β-catenin, and Ser-675 phosphorylated β-catenin. Additionally, the activity of protein kinase A (PKA), one of the upstream kinases that phosphorylates β-catenin at Ser-675, was found to be increased in both BRUCE-deficient mouse livers and a human liver cancer cell line. More importantly, BRUCE and PKA were found to be colocalized in the cytoplasm of hepatocytes.

Research conclusions

In conclusion, this study further demonstrated BRUCE’s liver tumor suppressive function, by identifying the early onset of tumorigenesis in LKO mice. Furthermore, the current study elucidated a novel role of BRUCE in the negative regulation of PKA activity in order to negatively regulate β-catenin stabilization and activity. Together, BRUCE’s regulation of β-catenin through PKA, is a likely mechanism used to suppress hepatic diseases, such as fibrosis and HCC.

Research perspectives

While further investigation is warranted, this study revealed the novel role of BRUCE in hepatic regulation of β-catenin upon liver injury. Further establishing BRUCE’s regulation of PKA activity can possibly provide more promising therapeutic approaches for treating liver disease patients with aberrant expression of BRUCE and β-catenin.