Role of the HBx oncoprotein in carbonic anhydrase 9 induction

Tereza Holotnakova (1) , Lucia Tylkova (2) , Martina Takacova (3) , Juraj Kopacek (3) , Juraj Petrik (4) , Silvia Pastorekova (3) , Jaromir Pastorek (3)

1 Institute of Virology, Slovak Academy of Sciences
2 Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences
3 Institute of Virology, Slovak Academy of Sciences
4 Scottish National Blood Transfusion Service

Carbonic anhydrase 9 (CA9), as one of the most hypoxia-responsive genes, has been associated almost exclusively with hypoxic tumours. Its principal role is in pH regulation which helps tumour 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 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.

Mots clés: Medicine

Tereza Holotnakova, Lucia Tylkova, Martina Takacova, Juraj Kopacek, Juraj Petrik, et al.. Role of the HBx oncoprotein in carbonic anhydrase 9 induction. Journal of Medical Virology, 2009, 82 (1), pp.32. ⟨10.1002/jmv.21671⟩. ⟨hal-00541152⟩