Pre-S2 deletion mutants of hepatitis B virus could have an important role in hepatocarcinogenesis in Asian children

Abstract

Although many studies on the risk factors and their carcinogenesis in adult hepatocellular carcinoma (HCC) have been reported, they remain poorly understood in childhood HCC. A retrospective study of 42 HCC cases in Asian children was conducted. Hepatitis B virus (HBV)-DNA in HCC tissues was detected in 36 of 42 (86%) cases tested, while no hepatitis C virus (HCV)-RNA was detectable in any of HCCs. Twenty of 36 (56%) HCC cases were accompanied by cirrhosis. Surprisingly, very high prevalence of the HBV pre-S deletion mutant was recognized in 27 of 30 (90%) HCCs examined. They occurred most frequently in pre-S2 (20/27, 74%) followed by pre-S1 (5/27, 18.5%), and both pre-S1/S2 (2/27, 7.4%). Interestingly, the pre-S2 mutant consistently appeared with deletion at nt 4-57 in all of the 20 cases with the pre-S2 mutant (100%) and within this locus in the two cases with both pre-S-1/S2 mutants. Type II ground-glass hepatocytes in non-tumorous livers were seen in 15 of the 22 HCCs with the pre-S2 deletion mutant (68%). This hotspot mutation in the pre-S2 was further confirmed by complete genomic sequence of HBV in a Japanese boy who eventually developed HCC. Our result strongly suggests that HBV is a major contributor to the development of HCC in Asian children. The HBV pre-S2 deletion mutant at nt 4-57 which has a CD8 T-cell epitope could be responsible for the emergence and aggressive outcome of childhood HCC. Determination of this hotspot mutation in the pre-S2 region could be a useful index for predicting the clinical outcome of HCC development.

Figure 1

Map of hepatitis B virus (HBV) pre‐S deletion mutant identified in childhood hepatocellular carcinoma (HCC). Numbers of nucleotide positions are based on the HBV‐VT101 isolate (accession no: AB112063).

Figure 2

Clinical course of a Japanese boy (#IF801) who eventually developed hepatocellular carcinoma (HCC) (A) and his sister (B). ‘a’, ‘a’ determinant domain in the S gene; AFP, alpha‐fetoprotein; ALT, alanine aminotransferase; CAH, chronic active hepatitis on biopsy; CP, core promoter; IFN, interferon; m, mutant; PC, precore; Shosaikoto, Kampo medicine; w, wild type.

Figure 3

Liver histology of a Japanese boy (#IF801) showing moderately differentiated hepatocellular carcinoma (HCC) with a trabecular pattern (A). Scattered large regenerative nodules with fatty metamorphosis (arrows) suggesting pre‐neoplastic changes in non‐cancerous liver were observed (B). Scattered clusters of ground‐glass hepatocyte (GGH) were present in the non‐cancerous liver (C). By immunohistochemical staining using serial sections, these GGHs were strongly reactive for hepatitis B surface antigen (HBsAg) and formed a localization pattern corresponding to type I and type II GGHs (D).

Figure 4

Alignment of nucleotide sequence in pre‐S1/S2 regions that showed deletions. Slash indicates nucleotide deletion. Number indicates nucleotide site of the defined hepatitis B virus (HBV) genome. –Years for each isolate corresponds to the age in years at which HBV was recovered.