title: Hepatitis B virus precore mutants in serum and liver of Southern African Blacks with hepatocellular carcinoma.
abstract: OBJECTIVE
  The aim of this study was to sequence the precore region of HBV isolated from serum and tumorous and non-tumorous liver tissue from patients with hepatocellular carcinoma to identify mutations that might play a role in malignant transformation.
  
  
  METHODS
  HBV DNA was extracted from 62 sera, 14 tumorous and 12 non-tumorous liver tissue samples of patients with hepatocellular carcinoma, amplified by the polymerase chain reaction and sequenced directly.
  
  
  RESULTS
  Thirty-nine patients were HBeAg-negative and 23 HBeAg-positive. Missense mutations were present predominantly in HBeAg-negative sera. The most common missense mutation, a guanine to thymine transversion, occurred at nucleotide 1862 in the bulge of the encapsidation signal; it was more prevalent in HBeAg-negative (10/39) than in HBeAg-positive patients (1/23) (p = 0.03). Mutations known to prevent HBeAg synthesis were detected in seven sera; five with an 1896 stop-codon mutation, one with an 1817 nonsense mutation, and one with a frameshift mutation caused by an insertion between 1838 and 1839. Missense mutations and deletions were present more often in tumorous tissue derived from HBsAg-negative patients. In the tumours missense mutations occurred at position 1862 and 1899, and the deletions affected direct repeat 1 and/or the encapsidation signal and included the x gene stop-codon.
  
  
  CONCLUSIONS
  The 1862 mutation, and other missense mutations and deletions detected in the precore gene, may disrupt HBV DNA replication and/or signal peptide cleavage leading to HBeAg-negativity. Disruption of viral replication may promote integration of unencapsidated replicative intermediates and hence contribute to hepatocarcinogenesis.
authors.affiliation: Medical Research Council, Department of Medicine, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Kramvis
authors.forename: M C
authors.initials: MC
authors.lastname: Kew
authors.forename: S
authors.initials: S
authors.lastname: Bukofzer
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D044383:Black People; D006528:Carcinoma, Hepatocellular / Q000097:blood / Q000473:pathology / Q000821:virology*; D018388:Codon, Terminator; D004279:DNA, Viral / Q000032:analysis* / Q000097:blood; D006147:Guanine; D006513:Hepatitis B e Antigens / Q000097:blood / Q000737:chemistry / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008099:Liver / Q000473:pathology / Q000821:virology*; D008113:Liver Neoplasms / Q000097:blood / Q000473:pathology / Q000821:virology*; D008969:Molecular Sequence Data; D009154:Mutation; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017384:Sequence Deletion; D013019:South Africa; D013941:Thymine
chemical_list: D018388:Codon, Terminator; D004279:DNA, Viral; D006513:Hepatitis B e Antigens; D006147:Guanine; D013941:Thymine