scholarly journals Role of Hepatitis B Virus Large Surface Protein in Promoting Activation of Nuclear SREBPs via ER Stress: Implications for Hepatocellular Carcinoma

2019 ◽  
Vol 11 (2) ◽  
pp. 13
Author(s):  
Subir Ghosh
Keyword(s):  
Hepatocellular Carcinoma ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Regulatory Element ◽  
Regulatory Elements ◽  
Protein Activity ◽  
Atp Citrate Lyase ◽  
Citrate Lyase ◽  
B Virus

One of the most common fatal malignancies in the world is Hepatocellular carcinoma (HCC) and hepatitis B virus (HBV) infection has been identified as a leading risk factor for HCC. Studies have suggested that during infection the large surface viral protein of HBV (LS protein) is targeted to the endoplasmic reticulum (ER) of the host liver cell, where its accumulation causes ER stress leading to HCC. The LS protein is also believed to stimulate the lipogenic activity of the ATP citrate lyase (ACL) enzyme, leading to excessive synthesis of lipids required for the rapidly dividing liver tumor cell. Here, I propose a hypothesis linking viral LS protein-induced ER stress to generation of the mature transcriptionally active nuclear form of sterol regulatory element-binding protein (nSREBP). nSREBP translocates to the nucleus and binds to sterol regulatory elements (SRE) present in the ATP citrate lyase (ACL) gene promoter, thereby elevating ACL transcription levels and overproduction of the ACL enzyme protein. Inhibition of LS protein activity in the ER may provide a therapeutic strategy in treating HBV induced HCC.

scholarly journals Activation of ATP Citrate Lyase by mTOR Signal Induces Disturbed Lipid Metabolism in Hepatitis B Virus Pre-S2 Mutant Tumorigenesis

2014 ◽  
Vol 89 (1) ◽  
pp. 605-614 ◽  
Author(s):  
Chiao-Fang Teng ◽  
Han-Chieh Wu ◽  
Wen-Chuan Hsieh ◽  
Hung-Wen Tsai ◽  
Ih-Jen Su
Keyword(s):  
Lipid Metabolism ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Atp Citrate Lyase ◽  
Biphasic Pattern ◽  
Citrate Lyase ◽  
B Virus ◽  
Stress Dependent

ABSTRACTThe development of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) has been found to be associated with disturbed lipid metabolism. To elucidate the role of lipid metabolism in HBV tumorigenesis, we investigated the dynamic pattern of lipid metabolism in HBV pre-S2 mutant-induced tumorigenesis. Lipid and gene expression profiles were analyzed in anin vitroculture system and in transgenic mouse livers harboring HBV pre-S2 mutant. The pre-S2 mutant transgenic livers showed a biphasic pattern of lipid accumulation, starting from mild fatty change in early (1 month) transgenic livers, which subsided and then, remarkably, increased in HCC tissues. This biphasic pattern was synchronized with ATP citrate lyase (ACLY) activation. Further analyses revealed that the pre-S2 mutant initiated an endoplasmic reticulum (ER) stress-dependent mammalian target of rapamycin (mTOR) signalling cascade. The pre-S2 mutant-induced mTOR signal activated the sterol regulatory element binding transcription factor 1 (SREBF1) to upregulate ACLY, which then activated the fatty acid desaturase 2 (FADS2), mediated through ACLY-dependent histone acetylation. Such an ER stress-dependent mTOR signal cascade also is important for the proliferation of hepatocytesin vitroand is further validated in HBV-related HCC tissues.IMPORTANCEAberrations of lipid metabolism frequently occur in chronic HBV infection. Our results provide a potential mechanism of disturbed lipid metabolism in HBV pre-S2 mutant-induced tumorigenesis, which should be valuable for the design of HCC chemoprevention in high-risk HBV carriers.

scholarly journals Pre-S2 Mutant-Induced Mammalian Target of Rapamycin Signal Pathways as Potential Therapeutic Targets for Hepatitis B Virus-Associated Hepatocellular Carcinoma

2017 ◽  
Vol 26 (3) ◽  
pp. 429-438 ◽  
Author(s):  
Chiao-Fang Teng ◽  
Han-Chieh Wu ◽  
Woei-Cherng Shyu ◽  
Long-Bin Jeng ◽  
Ih-Jen Su
Keyword(s):  
Hepatocellular Carcinoma ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Mammalian Target Of Rapamycin ◽  
Hbv Infection ◽  
Target Of Rapamycin ◽  
Signal Pathways ◽  
Type Ii ◽  
B Virus

Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC). Pre-S2 mutant represents an HBV oncoprotein that is accumulated in the endoplasmic reticulum (ER) and manifests as type II ground glass hepatocytes (GGHs). Pre-S2 mutant can induce ER stress and initiate multiple ER stress-dependent or -independent cellular signal pathways, leading to growth advantage of type II GGH. Importantly, the mammalian target of rapamycin (mTOR) signal pathways are consistently activated throughout the liver tumorigenesis in pre-S2 mutant transgenic mice and in human HCC tissues, leading to hepatocyte proliferation, metabolic disorders, and HCC tumorigenesis. In this review, we summarize the pre-S2 mutant-induced mTOR signal pathways and its implications in HBV-related HCC tumorigenesis. Clinically, the presence of pre-S2 mutant exhibits a high resistance to antiviral treatment and carries a high risk of HCC development in patients with chronic HBV infection. Targeting at pre-S2 mutant-induced mTOR signal pathways may thus provide potential strategies for the prevention or therapy of HBV-associated HCC.

Hepatitis B virus small envelope protein promotes HCC angiogenesis via ER stress signaling to upregulate VEGFA expression

2021 ◽  
Author(s):  
Shu-Xiang Wu ◽  
Shuang-Shuang Ye ◽  
Yu-Xiang Hong ◽  
Yan Chen ◽  
Biao Wang ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Endoplasmic Reticulum ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Viral Protein ◽  
Unfolded Protein ◽  
B Virus ◽  
Protein Response ◽  
Hcc Cells

Hepatocellular carcinoma (HCC) is a hypervascular tumor and accumulating evidence has indicated that stimulation of angiogenesis by HBV may contribute to HCC malignancy. The small protein of hepatitis B virus surface antigen (HBsAg), SHBs, is the most abundant HBV viral protein and has a close clinical association with HCC, however, whether SHBs contributes to HCC angiogenesis remains unknown. This study reports that forced expression of SHBs in HCC cells promoted xenograft tumor growth and increased the microvessel density (MVD) within the tumors. Consistently, HBsAg was also positively correlated with MVD count in HCC patients’ specimens. The conditioned media from the SHBs-transfected HCC cells increased the capillary tube formation and migration of human umbilical vein endothelial cells (HUVECs). Intriguingly, overexpression of SHBs increased VEGFA expression at both mRNA and protein levels. A higher VEGFA expression level was also observed in the xenograft tumors transplanted with SHBs-expressing HCC cells and in HBsAg-positive HCC tumor tissues as compared to their negative controls. As expected, in the culture supernatants, the secretion of VEGFA was also significantly enhanced from HCC cells expressing SHBs, which promoted HUVECs migration and vessel formation. Furthermore, all the three unfolded protein response (UPR) sensors IRE1α, PERK and ATF6 associated with endoplasmic reticulum (ER) stress were found activated in the SHBs-expressing cells and correlated with VEGFA protein expression and secretion. Taken together, these results suggest an important role of SHBs in HCC angiogenesis and may highlight a potential target for preventive and therapeutic intervention of HBV-related HCC and its malignant progression. IMPORTANCE Chronic hepatitis B virus infection is one of the important risk factors for the development and progression of hepatocellular carcinoma (HCC). HCC is characteristic of hypervascularization even at early phases of the disease due to overexpression of angiogenic factors like vascular endothelial growth factor-A (VEGFA). However, a detailed mechanism in the HBV-induced angiogenesis remains to be established. In this study, we demonstrate for the first time that the most abundant HBV viral protein, i.e. small surface antigens (SHBs) can enhance the angiogenic capacity of HCC cells by upregulation of VEGFA expression both in vitro and in vivo . Mechanistically, SHBs induced endoplasmic reticulum (ER) stress which consequently activated unfolded protein response (UPR) signaling to increase VEGFA expression and secretion. This study suggests that SHBs plays an important pro-angiogenic role in HBV-associated HCC and may represent a potential target for anti-angiogenic therapy in the HCC.

scholarly journals A novel negative cis-regulatory element on the hepatitis B virus S-(+)-strand

1999 ◽  
Vol 80 (10) ◽  
pp. 2673-2683 ◽  
Author(s):  
Markus Wagner ◽  
Michael Alt ◽  
Peter Hans Hofschneider ◽  
Matthias Renner
Keyword(s):  
Gene Expression ◽  
Steady State ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Regulatory Element ◽  
Regulatory Elements ◽  
Luciferase Gene ◽  
B Virus ◽  
Luciferase Mrna ◽  
Steady State Levels

Hepatitis B virus (HBV) has a double-stranded DNA genome. The minus-strand contains coding regions for all known HBV proteins and most of the cis-regulatory elements. Little is known about transcription from the S-(+)-strand and its regulation. Thus, the presence of regulatory elements located on the S-(+)-strand was investigated by inserting nt 1038–1783 of HBV in both orientations between the human cytomegalovirus (HCMV) promoter and a luciferase gene. Transfection experiments revealed that the plasmid containing this HBV DNA fragment in an orientation allowing expression from the S-(+)-strand (antisense) led to inhibition of luciferase gene expression compared to the plasmid containing this sequence in an orientation that allows gene expression from the L-(−)-strand (sense). Deletion analyses delimit the sequence essential for the inhibitory effect to a 150 bp region that also carries part of the enhancerII/core promoter complex. However, the possible influence of this regulatory element has been excluded in various experiments. The repressing HBV sequence acts in an orientation- and position-dependent manner; no inhibition was observed when this DNA element was inserted upstream of the HCMV promoter or downstream of the luciferase gene. Northern blot analyses revealed reduced luciferase mRNA steady-state levels in cells transfected with constructs containing the essential HBV sequence in antisense orientation compared to plasmids containing this sequence in sense orientation. Since nuclear run-on experiments showed similar transcription initiation rates with these plasmids, the diminished luciferase mRNA steady-state levels must be due to altered stabilities, suggesting that nt 1783–1638 of HBV encode an RNA-destabilizing element.

scholarly journals Naturally Occurring Hepatitis B Virus Mutations Leading to Endoplasmic Reticulum Stress and Their Contribution to the Progression of Hepatocellular Carcinoma

2019 ◽  
Vol 20 (3) ◽  
pp. 597 ◽  
Author(s):  
Yu-Min Choi ◽  
So-Young Lee ◽  
Bum-Joon Kim
Keyword(s):  
Hepatocellular Carcinoma ◽  
Endoplasmic Reticulum ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Clinical Outcomes ◽  
Hbv Infection ◽  
Stress Induction ◽  
Naturally Occurring ◽  
B Virus

Hepatitis B virus (HBV) infection is a global health problem that causes a wide range of pathological outcomes, including cirrhosis and hepatocellular carcinoma (HCC). Endoplasmic reticulum (ER) stress induction by HBV infection has been implicated in liver carcinogenesis and disease progression with chronic inflammation via enhanced inflammation, oxidative stress-mediated DNA damage, and hepatocyte proliferation. In the natural course of HBV infection, the accumulation of naturally occurring mutations in the HBV genome can generate several mutant types of HBV-encoded proteins, including three different proteins in the S ORF (SHBs, MHBs, and LHBs) and HBcAg in the C ORF, which could contribute to enhanced ER stress in infected hepatocytes mainly via increased ER accumulation of mutant proteins. However, it seems that there may be distinct capacity and pathway in ER stress-induction and distinct resulting clinical outcomes between HBV variants. In addition, the role of HBxAg mutations in ER stress remains unknown. However, it has been reported that HBxAg itself could exert ER stress in infected cells, resulting in HCC generation in chronic HBV patients. To date, review papers regarding ER stress-mediated HBV mutation have been limited into a specific mutation type: preS2 deletion. So, in this review, we will discuss details about various mutation types in all four regions of the HBV genome (preS1, preS2, S, and C) related to ER stress and their distinct ER stress mechanisms and clinical outcomes in terms of mutation types.

Role of environmental factors in the etiology of hepatocellular carcinoma

2010 ◽  
Vol 151 (28) ◽  
pp. 1132-1136 ◽  
Author(s):  
István Tornai
Keyword(s):  
Hepatocellular Carcinoma ◽  
Hepatitis B Virus ◽  
Environmental Factors ◽  
Hepatitis B ◽  
Hepatitis A ◽  
Virus Hepatitis ◽  
B Virus

A krónikus vírushepatitisek jelentik ma a legismertebb okokat a hepatocellularis carcinoma (HCC) kialakulásában. A krónikus B- és C-vírus-hepatitis a májrákok körülbelül 40-50%-át okozza. A nyugati típusú társadalmakban a HCC előfordulása folyamatosan növekvő tendenciát mutat. Az alkohol számít a környezeti tényezők közül a legfontosabbnak, bár az alkoholfogyasztás a legtöbb országban csökken. Ez aláhúzza az egyéb környezeti tényezők fontosságát is. Az elfogyasztott alkoholmennyiséggel egyenes arányban növekszik a cirrhosis és a következményes HCC gyakorisága nőkben és férfiakban egyaránt. A kémiai anyagok közül a legismertebb a Kínában és Afrikában elterjedt aflatoxin, amely a gabonaféléket szennyező mycotoxin. Hasonló területeken endémiás, mint a hepatitis B-vírus, együtt szinergista hatást fejtenek ki. A dohányzás is egyértelműen bizonyított hepatocarcinogen hatással rendelkezik. Ez is jelentősen fokozódik, ha alkoholfogyasztással vagy vírushepatitisszel társul. Társadalmilag talán a legfontosabb az elhízás, a következményes nem alkoholos zsírmáj, illetve steatohepatitis és a 2-es típusú cukorbetegség, amelyek prevalenciája egyre fokozódik. Feltehetően ezek állnak a növekvő HCC-gyakoriság hátterében. Az inzulinrezisztencia és az oxidatív stressz képezik a legfontosabb patogenetikai lépéseket a májsejtkárosodásban. További fontos rizikótényező az orális fogamzásgátlók elterjedt használata. Egyes foglalkozások esetén a tartós szervesoldószer-expozíció is növeli a HCC rizikóját. Védelmet jelenthetnek az antioxidánsok, a szelén, a gyógyszerek közül a statinok és a feketekávé-fogyasztás.

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