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Genomic aberrations in human hepatocellular carcinomas of differing etiologies
1Department of Clinical Oncology, Sir Y. K. Pao Centre for Cancer, The Chinese University of Hong Kong, Shatin, New Territories, Special Administrative Region.
Abstract:
We sought to assess whether genetic abnormalities in hepatocellular carcinoma differed in geographic locations associated with different risk factors. Comparative genomic hybridization (CGH) was applied to the genome-wide chromosomal analysis in 83 tumor samples from four different geographic origins. Samples were obtained from regions that differed in aflatoxin exposure: China (Hong Kong with low aflatoxin exposure and Shanghai with moderate aflatoxin exposure), Japan, and the United States (negligible aflatoxin exposure). Cases from Hong Kong and Shanghai were all hepatitis B virus (HBV) related, those from Japan were hepatitis C virus related, and those from the United States were HBV negative. In parallel, the mutational pattern of the whole p53 gene (exons 1-11) was also investigated in these cases. CGH revealed a complex pattern of chromosomal gains and losses, with the commonest aberration in each geographic location being chromosome 1q copy number gain (38-60%). Shanghai cases displayed the highest number of total aberrations per sample, with significant copy losses on 4q (75%), 8p (70%), and 16q (65%). Hepatitis C virus-related samples from Japan had a characteristically high incidence of 11q13 gain. p53 mutation(s) was detected in 23% of Hong Kong cases, 40% of Shanghai, 31% of Japan, but only 6% of the United States cases. The "aflatoxin-associated" codon 249 mutation was, however, identified only in samples from China (13% Hong Kong and 20% Shanghai). This finding, together with the highly aberrant pattern of genetic changes detected in the Shanghai series, is suggestive of the genotoxic effects of aflatoxin being more broadly based. It is also likely that there is a synergistic effect of HBV infection and high aflatoxin exposure in promoting hepatocellular carcinoma development. It appears from our CGH study that individual risk factors are indeed associated with distinct genetic aberrations, although changes in 1q gain appear common to all.