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Role of the HBx oncoprotein in carbonic anhydrase 9 induction
Author(s) -
Holotnakova Tereza,
Tylkova Lucia,
Takacova Martina,
Kopacek Juraj,
Petrik Juraj,
Pastorekova Silvia,
Pastorek Jaromir
Publication year - 2010
Publication title -
journal of medical virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 121
eISSN - 1096-9071
pISSN - 0146-6615
DOI - 10.1002/jmv.21671
Subject(s) - hbx , biology , transfection , gene , hepatitis b virus , microbiology and biotechnology , hypoxia inducible factors , hepatocellular carcinoma , transcription factor , gene expression , transcription (linguistics) , cancer research , virology , virus , genetics , linguistics , philosophy
Carbonic anhydrase 9 (CA9), as one of the most hypoxia‐responsive genes, has been associated almost exclusively with hypoxic tumors. Its principal role is in pH regulation which helps tumor cells overcome intracellular acidosis and survive extended periods of time with low oxygen. Hypoxia‐inducible factor 1 (HIF‐1) is the main transcriptional activator of CA9. Hepatitis B virus X protein (HBx) has been shown to increase the transcriptional activity of HIF‐1. HBx is often expressed from the gene integrated in the hepatocytes infected persistently and contributes significantly to alterations in host gene expression that can lead to the development of hepatocellular carcinoma (HCC) associated with Hepatitis B virus (HBV). The aim of this study was to determine the effect of HBx on expression of CA9. Transient transfection of HBx led to an increase in the expression of CA9 as assessed by RT‐PCR and Western blotting. HBx was able to increase CA9 promoter activity significantly in several cell lines. The effect was mediated via HIF‐1 and a functional HRE element located −10/−3 bp upstream of the CA9 transcription initiation site. These data suggest that CA9 may be involved in the development of HCC by contributing to the survival of hepatocytes infected with HBV in liver tissue with fibrosis. J. Med. Virol. 82:32–40, 2010. © 2009 Wiley‐Liss, Inc.