Thyroid hormone protects hepatocytes from HBx-induced carcinogenesis by enhancing mitochondrial turnover

• Published in: Oncogene Vol. 36; no. 37; pp. 5274 - 5284
• Main Authors: Chi, H-C, Chen, S-L, Lin, S-L, Tsai, C-Y, Chuang, W-Y, Lin, Y-H, Huang, Y-H, Tsai, M-M, Yeh, C-T, Lin, K-H
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 14.09.2017; Nature Publishing Group
• Subjects: 13/51; 14/1; 14/34; 14/63; 38/109; 631/67/1504/1610; 631/67/2327; 64/60; 96/1; Animals; Apoptosis; Autophagy; Carcinogenesis; Carcinogenesis - genetics; Carcinogenesis - metabolism; Carcinogenesis - pathology; Carcinoma, Hepatocellular - genetics; Carcinoma, Hepatocellular - metabolism; Cell Biology; Complications and side effects; Data processing; Development and progression; DNA Damage; DNA microarrays; Fatty liver; Genetic aspects; HBX protein; Health aspects; Hep G2 Cells; Hepatitis; Hepatitis B; Hepatocellular carcinoma; Hepatocytes; Hepatocytes - metabolism; Hepatocytes - pathology; Hepatoma; Hormones; Human Genetics; Humans; Internal Medicine; Liver cancer; Liver cells; Liver diseases; Liver Neoplasms - genetics; Liver Neoplasms - metabolism; Liver Neoplasms, Experimental - genetics; Liver Neoplasms, Experimental - metabolism; Male; Medicine; Medicine & Public Health; Mice; Mice, Transgenic; Mitochondria; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial biogenesis; Oncology; original-article; Parkin protein; Phagocytosis; Prevention; Protein Kinases - genetics; Protein Kinases - metabolism; PTEN protein; PTEN-induced putative kinase; Reactive oxygen species; Rodents; Signal Transduction; Steatosis; Thyroid; Thyroid gland; Thyroid hormones; Trans-Activators - biosynthesis; Trans-Activators - genetics; Transgenic mice; Triiodothyronine; Triiodothyronine - metabolism; Tumors; Ubiquitin-protein ligase; Taiwan
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2017.136

Infection by hepatitis B virus (HBV) accounts for 50–80% of hepatocellular carcinoma (HCC) development worldwide, in which the HBV-encoded X protein (HBx) has critical role in the induction of carcinogenesis. Several studies have shown that thyroid hormone (TH) suppresses HCC development and protects hepatocytes from HBx-induced damage, thus it is of interest to examine whether TH can protect hepatocytes from HBx-induced carcinogenesis. By treating HBx- transgenic mice with or without TH, we confirmed the protective effects of TH on HBx-induced hepatocarcinogenesis, which was achieved via reduction of reactive oxygen species (ROS) inflicted DNA damage. We further found that TH induced biogenesis of mitochondria (MITO) and autophagy of HBx-targeted MITO simultaneously, consequently leading to suppression of HBx-promoted ROS and carcinogenesis. Using microarray data analysis, this protective effect of TH was found to be mediated via activation of PTEN-induced kinase 1 (PINK1) in hepatocytes. PINK1, in turn, activated and recruited Parkin, an E3 ligase, to ubiquitinate MITO-associated HBx protein and trigger selective mitophagy. The pathological significance of the TH/PINK1 pathway in liver protection was confirmed by the concomitant decrease in expression of both TR and PINK1 in matched HCC tumor tissues and negatively correlated with aggressive progression of cancer and poor prognosis. Our data indicate that TH/PINK1/Parkin pathway has a critical role in protecting hepatocytes from HBx-induced carcinogenesis. Notably, several liver-targeting therapeutic derivatives of TH facilitating prevention or therapy of steatosis have been identified. Furthermore, our proof-of-concept experiments suggest that application of T 3 constitutes an effective novel therapeutic or preventive option for HCC. Thus, the utilization of the agonists of TRs could be the meaningful strategy in liver relative diseases, ranging from simple hepatic steatosis to HCC.