Fang Z L, Ling R, Wang S S, Nong J, Huang C S, Harrison T J
University Department of Medicine, Royal Free Hospital School of Medicine, London, United Kingdom.
J Med Virol. 1998 Sep;56(1):18-24. doi: 10.1002/(sici)1096-9071(199809)56:1<18::aid-jmv4>3.0.co;2-q.
The development of primary liver cancer frequently is associated with persistent HBV infection, and tumours may arise in individuals who are anti-HBe positive. However, it is unclear whether viruses with an HBeAg-negative phenotype are associated with tumour development or are selected, during seroconversion, after chromosomal integration of wild-type viral DNA. In order to investigate the temporal evolution of the HBV genome in such individuals, the polymerase chain reaction was used to amplify HBV DNA from tumour tissue and serum of 14 patients from Guangxi, China with hepatocellular carcinoma. Comparison of nucleotide and amino acid sequences of the precore and proximal core region of HBV from the two sites in each patient produced evidence of divergence following integration in the tumour, but in most cases, HBeAg-negativity could not be explained by precore mutations. Sequences from the core promoter region were therefore examined and mutations were found in the majority, which are believed to upregulate transcription of the core (and pregenomic) RNA but to downregulate precore mRNA. To determine whether this finding merely reflected sequence variation among geographical isolates of HBV, the same region of HBV DNA from asymptomatic controls was sequenced and these mutations were found to be rare. We hypothesise that HBV with the core promoter mutations replicates at higher levels than the wild type, with the consequence that more integrations occur into the hepatocyte chromosomes during the early stages of infection. These hepatocytes may expand clonally and be targets for further mutagenic events leading to tumour development.
原发性肝癌的发生常与持续性乙肝病毒（HBV）感染相关，且肿瘤可能出现在抗HBe阳性个体中。然而，尚不清楚具有HBeAg阴性表型的病毒是否与肿瘤发生相关，或者在血清转换期间，野生型病毒DNA染色体整合后是否被选择。为了研究此类个体中HBV基因组的时间演变，采用聚合酶链反应从中国广西14例肝细胞癌患者的肿瘤组织和血清中扩增HBV DNA。对每位患者两个部位的HBV前核心区和近端核心区的核苷酸和氨基酸序列进行比较，结果显示肿瘤中整合后出现了序列分歧，但在大多数情况下，HBeAg阴性不能用前核心区突变来解释。因此，对核心启动子区域的序列进行了检测，发现大多数存在突变，这些突变被认为会上调核心（和前基因组）RNA的转录，但下调前核心mRNA。为了确定这一发现是否仅仅反映了HBV地理分离株之间的序列变异，对无症状对照的HBV DNA相同区域进行了测序，发现这些突变很少见。我们推测，具有核心启动子突变的HBV比野生型复制水平更高，其结果是在感染早期更多地整合到肝细胞染色体中。这些肝细胞可能会克隆性扩增，并成为导致肿瘤发生的进一步诱变事件的靶点。
