Determination frequency of mutations at x gene in the Enhancer II region of the hepatitis B virus in patients with HCC due to HBV

Introduction and Objectives: Hepatitis B virus (HBV) is known as a health problem around the world. The HBV has ORF x which codes the protein x (HBx). This gene, by inhibiting proteasome in the MHC I pathway, caused activating the replication and transcription of the virus genes as enhancers and promoters, that have a role in the development of HCC in the host cells. The mutations in this region are associated with the development of Hepatocellular carcinoma. Materials and Methods: In a retrospective study, 33 pathological samples from patients with HCC were examined for the presence of mutations at X region in the Enhancer II of the HBV. In this study, the mutations in 465 base pairs of HBx were identified by sequencing. Result: Out of the 33 patients with HCC cancer, 17 patients (51.1%) were positive for 465 bp specific product of HBx and 16 patients (48.5%) were negative. The average viral load in positive cases was (8.46±4.22) x105 and (5.34±2.41) x103, in negative samples for HBx respectively. The results of the sequencing showed that 9 mutations occurred in the HBx region and 3 mutations occurred in the Enhancer II region, including mutations C1632G, C1631G, C1630G, G1629A, C1628G, A1633T, A1647C, A1648G, and T1658A. Conclusion: The results showed that the highest frequency of mutations in the Enhancer II region were between 1636 and 1741 nucleotide sequences. Considering the analysis of the three-dimensional structure of the mutant forms, it is likely that mutation in these regions causes a change in the position of binding to tumor suppressing proteins. It may also play a role as a protein in hiding and escape the HBV virus from the immune system, and lost the immunogenic property.

Keywords:

Hepatitis B virus , HBx , Hepatocellular Cancer , Enhancer II