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Title: Role of hypoxia-inducible factor-{alpha} in hepatitis-B-virus X protein-mediated MDR1 activation

Abstract

The transition from chemotherapy-responsive cancer cells to chemotherapy-resistant cancer cells is mainly accompanied by the increased expression of multi-drug resistance 1 (MDR1). We found that hepatitis-B-virus X protein (HBx) increases the transcriptional activity and protein level of MDR1 in a hepatoma cell line, H4IIE. In addition, HBx overexpression made H4IIE cells more resistant to verapamil-uptake. HBx stabilized hypoxia-inducible factor-1{alpha} (HIF-1{alpha}) and induced the nuclear translocation of C/EBP{beta}. Reporter gene analyses showed that HBx increased the reporter activity in the cells transfected with the reporter containing MDR1 gene promoter. Moreover, the luciferase reporter gene activity was significantly inhibited by HIF-1{alpha} siRNA but not by overexpression of C/EBP dominant negative mutant. These results imply that HBx increases the MDR1 transporter activity through the transcriptional activation of the MDR1 gene with HIF-1{alpha} activation, and suggest HIF-1{alpha} for the therapeutic target of HBV-mediated chemoresistance.

Authors:
 [1];  [1];  [1];  [2];  [3]
  1. BK21 Project Team, College of Pharmacy, Chosun University, Gwangju 501-759, South Korea (Korea, Republic of)
  2. College of Pharmacy, Pusan National University, Busan 609-735, South Korea (Korea, Republic of)
  3. BK21 Project Team, College of Pharmacy, Chosun University, Gwangju 501-759, South Korea (Korea, Republic of). E-mail: kwkang@chosun.ac.kr
Publication Date:
OSTI Identifier:
20991371
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 357; Journal Issue: 2; Other Information: DOI: 10.1016/j.bbrc.2007.04.012; PII: S0006-291X(07)00725-5; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ANOXIA; CHEMOTHERAPY; DRUGS; GENES; HEPATITIS; HEPATOMAS; LUCIFERASE; MUTANTS; PROMOTERS; TRANSLOCATION; VIRUSES

Citation Formats

Han, Hyo-Kyung, Han, Chang Yeob, Cheon, Eun-Pa, Lee, Jaewon, and Kang, Keon Wook. Role of hypoxia-inducible factor-{alpha} in hepatitis-B-virus X protein-mediated MDR1 activation. United States: N. p., 2007. Web. doi:10.1016/j.bbrc.2007.04.012.
Han, Hyo-Kyung, Han, Chang Yeob, Cheon, Eun-Pa, Lee, Jaewon, & Kang, Keon Wook. Role of hypoxia-inducible factor-{alpha} in hepatitis-B-virus X protein-mediated MDR1 activation. United States. doi:10.1016/j.bbrc.2007.04.012.
Han, Hyo-Kyung, Han, Chang Yeob, Cheon, Eun-Pa, Lee, Jaewon, and Kang, Keon Wook. Fri . "Role of hypoxia-inducible factor-{alpha} in hepatitis-B-virus X protein-mediated MDR1 activation". United States. doi:10.1016/j.bbrc.2007.04.012.
@article{osti_20991371,
title = {Role of hypoxia-inducible factor-{alpha} in hepatitis-B-virus X protein-mediated MDR1 activation},
author = {Han, Hyo-Kyung and Han, Chang Yeob and Cheon, Eun-Pa and Lee, Jaewon and Kang, Keon Wook},
abstractNote = {The transition from chemotherapy-responsive cancer cells to chemotherapy-resistant cancer cells is mainly accompanied by the increased expression of multi-drug resistance 1 (MDR1). We found that hepatitis-B-virus X protein (HBx) increases the transcriptional activity and protein level of MDR1 in a hepatoma cell line, H4IIE. In addition, HBx overexpression made H4IIE cells more resistant to verapamil-uptake. HBx stabilized hypoxia-inducible factor-1{alpha} (HIF-1{alpha}) and induced the nuclear translocation of C/EBP{beta}. Reporter gene analyses showed that HBx increased the reporter activity in the cells transfected with the reporter containing MDR1 gene promoter. Moreover, the luciferase reporter gene activity was significantly inhibited by HIF-1{alpha} siRNA but not by overexpression of C/EBP dominant negative mutant. These results imply that HBx increases the MDR1 transporter activity through the transcriptional activation of the MDR1 gene with HIF-1{alpha} activation, and suggest HIF-1{alpha} for the therapeutic target of HBV-mediated chemoresistance.},
doi = {10.1016/j.bbrc.2007.04.012},
journal = {Biochemical and Biophysical Research Communications},
number = 2,
volume = 357,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}
  • The smallest protein of hepatitis B virus, HBX, has been implicated in the development of liver diseases by interfering with normal cellular processes. Its role in cell proliferation has been unclear as both pro-apoptotic and anti-apoptotic activities have been reported. We showed molecular evidence that HBX induced apoptosis in HepG2 cells. A Bcl-2 Homology Domain 3 was identified in HBX, which interacted with anti-apoptotic but not pro-apoptotic members of the Bcl-2 family of proteins. HBX induced apoptosis when transfected into HepG2 cells, as demonstrated by both flow cytometry and caspase-3 activity. However, HBX protein may not be stable in apoptoticmore » cells triggered by its own expression as only its mRNA or the fusion protein with the glutathione-S-transferase was detected in transfected cells. Our results suggested that HBX behaved as a pro-apoptotic protein and was able to induce apoptosis.« less
  • In response to cellular hypoxia, cardiomyocytes adapt to consume less oxygen by shifting ATP production from mitochondrial fatty acid {beta}-oxidation to glycolysis. The transcriptional activation of glucose transporters and glycolytic enzymes by hypoxia is mediated by hypoxia-inducible factor 1 (HIF-1). In this study, we examined whether HIF-1 was involved in the suppression of mitochondrial fatty acid {beta}-oxidation in hypoxic cardiomyocytes. We showed that either hypoxia or adenovirus-mediated expression of a constitutively stable hybrid form (HIF-1{alpha}/VP16) suppressed mitochondrial fatty acid metabolism, as indicated by an accumulation of intracellular neutral lipid. Both treatments also reduced the mRNA levels of muscle carnitine palmitoyltransferasemore » I which catalyzes the rate-limiting step in the mitochondrial import of fatty acids for {beta}-oxidation. Furthermore, adenovirus-mediated expression of HIF-1{alpha}/VP16 in cardiomyocytes under normoxic conditions also mimicked the reduction in the DNA binding activity of peroxisome proliferator-activated receptor {alpha} (PPAR{alpha})/retinoid X receptor (RXR), in the presence or absence of a PPAR{alpha} ligand. These results suggest that HIF-1 may be involved in hypoxia-induced suppression of fatty acid metabolism in cardiomyocytes by reducing the DNA binding activity of PPAR{alpha}/RXR.« less
  • Several metal ions that are carcinogenic affect cellular iron homeostasis by competing with iron transporters or iron-regulated enzymes. Some metal ions can mimic a hypoxia response in cells under normal oxygen tension, and induce expression of HIF-1{alpha}-regulated genes. This study investigated whether 12 metal ions altered iron homeostasis in human lung carcinoma A549 cells as measured by an activation of IRP-1 and ferritin level. We also studied hypoxia signaling by measuring HIF-1{alpha} protein levels, hypoxia response element (HRE)-driven luciferase reporter activity, and Cap43 protein level (an HIF-1{alpha} responsive gene). Our results show the following: (i) Ni(II), Co(II), V(V), Mn(II), andmore » to a lesser extent As(III) and Cu(II) activated the binding of IRP-1 to IRE after 24 h, while the other metal ions had no effect; (ii) 10 of 12 metal ions induced HIF-1{alpha} protein but to strikingly different degrees. Two of these metal ions, Al(III) and Cd(II), did not induce HIF-1{alpha} protein; however, as indicated below, only Ni(II), Co (II), and to lesser extent Mn(II) and V(V) activated HIF-1{alpha}-dependent transcription. The combined effects of both [Ni(II) + As(III)] and [Ni(II) + Cr(VI)] on HIF-1{alpha} protein were synergistic; (iii) Addition of Fe(II) with Ni(II), Co(II), and Cr(VI) attenuated the induction of HIF-1{alpha} after 4 h treatment; (iv) Ni(II), Co(II), and Mn(II) significantly decrease ferritin level after 24 h exposure; (v) Ni(II), Co(II), V(V), and Mn(II) activated HRE reporter gene after 20 h treatment; (vi) Ni(II), Co(II), V(V), and Mn(II) increased the HIF-1-dependent Cap43 protein level after 24 h treatment. In conclusion, only Ni (II), Co (II), and to a lesser extent Mn(II) and V(V) significantly stabilized HIF-1{alpha} protein, activated IRP, decreased the levels of ferritin, induced the transcription of HIF-dependent reporter, and increased the expression of Cap43 protein levels (HIF-dependent gene). The mechanism for the significant stabilization and elevation of HIF-1{alpha} protein which drives these other parameters was previously shown by us and others to involve a loss of cellular Fe as well as inhibition of HIF-1{alpha}-dependent prolyl hydroxylases which target the binding of VHL ubiquitin ligase and degrade HIF-1{alpha}. Even though there were small effects of some of the other metals on IRP and HIF-1{alpha}, downstream effects of HIF-1{alpha} activation and therefore robust hypoxia signaling were only observed with Ni(II), Co(II), and to much lesser extents with Mn(II) and V(V) in human A549 lung cells. It is of interest that the metal ions that were most effective in activating hypoxia signaling were the ones that were poor inducers of metallothionein protein and also decreased Ferritin levels, since both of these proteins can bind metal ions and protect the cell against toxicity in human lung cells. It is important to study effects of these metals in human lung cells since this represents a major route of human environmental and occupational exposure to these metal ions.« less
  • Transgenic mice expressing the full-length HCV coding sequence were crossed with mice that express the HBV X gene-encoded regulatory protein HBx (ATX mice) to test the hypothesis that HBx expression accelerates HCV-induced liver pathogenesis. At 16 months (mo) of age, hepatocellular carcinoma was identified in 21% of HCV/ATX mice, but in none of the single transgenic animals. Analysis of 8-mo animals revealed that, relative to HCV/WT mice, HCV/ATX mice had more severe steatosis, greater liver-to-body weight ratios, and a significant increase in the percentage of hepatocytes staining for proliferating cell nuclear antigen. Furthermore, primary hepatocytes from HCV, ATX, and HCV/ATXmore » transgenic mice were more resistant to fas-mediated apoptosis than hepatocytes from nontransgenic littermates. These results indicate that HBx expression contributes to increased liver pathogenesis in HCV transgenic mice by a mechanism that involves an imbalance in hepatocyte death and regeneration within the context of severe steatosis.« less
  • The hypoxia-inducible factor (HIF) is recognized as the master regulator of hypoxia response. HIF-α subunits expression are tightly regulated. In this study, our data show that ts20 cells still expressed detectable E1 protein even at 39.5° C for 12 h, and complete depletion of E1 protein expression at 39.5° C by siRNA enhanced HIF-1α and P53 protein expression. Further inhibition of E1 at 39.5 °C by siRNA, or E1 inhibitor Ube1-41 completely blocked HIF-1α degradation. Moreover, immunoprecipitations of co-transfection of HA-ubiquitin and FLAG–HIF–1α plasmids directly confirmed the involvement of ubiquitin in the hypoxic degradation of HIF-1α. Additionally, hypoxic HIF-1 α degradation is independent ofmore » HAF, RACK1, sumoylation or nuclear/cytoplasmic localization. Taken together, our data suggest that constitutive HIF-1α protein degradation in hypoxia is absolutely ubiquitination-dependent, and unidentified E3 ligase may exist for this degradation pathway. - Highlights: • HIF-1α protein is constitutively degraded in hypoxic conditions. • Requirement of ubiquitination for HIF-1α degradation in hypoxia. • Hypoxic HIF-1α degradation is independent of HAF, RACK1, sumoylation or nuclear/cytoplasmic localization.« less