== DNA was extracted from 85l serum by Pronase digestion followed by phenol/chloroform extraction
== DNA was extracted from 85l serum by Pronase digestion followed by phenol/chloroform extraction. is the favoured site for the deletion mutations, especially in HCC cases. Further prospective studies are required to confirm the role of these mutations in the development of HCC. == INTRODUCTION == Chronic hepatitis B virus (HBV) infection is the most important aetiology of hepatocellular carcinoma (HCC) in Asia (Beasleyet al., 1981). However, the mechanisms of oncogenesis are obscure. Recently, viral factors associated with the development of HCC have become a major focus for research. The common precore mutation (G1896A) and mutations in enhancer II (C1653T) and the basal core promoter (T1753V and the double mutations A1762T and G1764A) have been reported to be associated with the development of HCC (Liuet al., 2006;Tanakaet al., 2006;Chenet al., 2006a;Yuenet al., 2008). Perhaps the most convincing association is with virus with double mutations in the basal core promoter (BCP) (Hsiaet al., 1996;Fanget al., 1998,2002;Baptistaet al., 1999;Kaoet al., 2003). A recent prospective study TPN171 of a cohort of 2258 hepatitis B surface antigen (HBsAg)-positive individuals in Long An county, Guangxi, China showed that BCP double mutations are an aetiological factor of HCC (Fanget al., 2008). Mutations in the BCP may also result in amino acid substitutions in the X protein and the A1762T, G1764A mutations result in two, L130M and V131I; however, these changes decrease the ability of the protein to transactivate transcription, at least as far as expression of the viral precore and pregenomic RNAs are concerned (Liet al., 1999). HBV can be divided into eight genotypes (designated by capital letters A to H) based on an intergroup divergence of 8 % or more in the complete nucleotide sequence (Okamotoet al., 1988;Arauz-Ruizet al., 2002) and these display remarkable geographical variation. Genotypes B and C are predominant in Asia (Yuet al., 2005) and have TPN171 been reported to have clinical relevance (Kao, 2002). However, the precise role of these two genotypes in the development of HCC remains controversial (Chanet al., 2004;Yuet al., 2005;Sumiet al., 2003;Yuenet al., 2008). The association between HBV genotype C and HCC may not TPN171 be attributable to genotype per se but rather to the high prevalence ITGA11 of BCP double mutations in patients with genotype C (Yuenet al., 2004). The emergence of persistently infected individuals of HBV with deletions in the pre-S region has been recognized for many years (Santantonioet al., 1992) and the mutations have been reported to be more common in genotypes B and C than in other HBV genotypes (Huyet al., 2003). Although there is increasing evidence of association of these mutations with severe liver disease (Taiet al., 2002;Huyet al., 2003), their clinical significance is rather obscure, especially their association with HCC. A recent study from Taiwan reported that the combination of pre-S deletion mutations and BCP double mutations, rather than either alone, was associated with the development of HCC (Chenet al., 2006a). Several subsequent studies also reported that pre-S deletions are associated with the development of HCC. However, this association is not convincing without exclusion of the confounding effect of BCP double mutations (Choiet al., 2007;Linet al., 2007;Gaoet al., 2007). The occurrence of pre-S deletions and BCP mutations is associated with HBV genotype (Sugauchiet al., 2003) and both are of higher prevalence in genotype C than in other genotypes (Kaoet al., 2003;Sugauchiet al., 2003). It is possible that the association between pre-S deletions and HCC may be not attributable to pre-S deletions per se but rather to the high prevalence of BCP double mutations in genotype C. The aim of this study was to determine whether the association of pre-S deletions with the development of HCC is independent.