| Research Abstract |
Both loss of heterozygosity (LOH) and replication error (RER) are considered to be phenotypes of genomic instability. In order to unveil a role of genomic instability in hepatocarcinogenesis, frequencies of LOH and RER were simultaneously determined in hepatocellular carcinoma (HOC), surrounding non-tumorous liver tissues (SL) and liver tissues with chronic viral hepatitis avoid of cancer (NC) by referencing peripheral white blood cells from the same donor. The frequencies were analyzed using 18 microsatellite markers spreading all over the genome in 11 HCC and SL, and 10 NC.LOH was significantly frequent in HCC compared to that in SL or NC (P=0.0l, P=0.00l, respectively), and observed at particular microsatellite loci, D2S123, D8S1106, D9S266, D15S165, and D16S748. In contrast, RER was detected at random loci, and its occurrence rate was increased only a little through hepatocarcinogenesis. Frequencies of LOH and RER were not significantly but tended to be higher in SL than in NC.HBV
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infection had a tendency being associated with the instability than HCV infection especially as LOH in HCC (P=0.04). These data suggest that LOR is closely associated with the multistep process of liver carcinogenesis especially under HBV infection, but RER is hardly associated with HCC development even under HCV infection.
Hepatocellular carcinoma (HOC) mainly arises from the liver with chronic inflammation viewed as precancerous steps. Because telomere reduction reflects replicative history in somatic cells, we analyzed the possibility that liver tissues surrounding HOC consist of the cells carrying substantial reduction of telomere. We studied 15 HOC and surrounding non-cancerous liver tissues (SL) obtained by surgical resection, and 10 laparoscopically obtained needle biopsy specimens of the liver with chronic inflammation including no overt HOC (CI). Five liver tissues without chronic liver diseases (ND) were also examined as a control. Extracted genomic DNAs were blotted on a nylon membrane, and probed at first with radio-labeled d(TTAGGG)_3 and re- probed with radio-labeled d(CCT)_7. The intensity due to d(TTAGGG)_3 was divided by that of d(CCT)_7. The ratio was defined as telomeric repeats content (TC). Dilution experiments reproducibly revealed almost the same TC value in the range from 12.5ng to 200ng of blotted genomic DNAs. The reduction rate of telomere length through aging estimated by regression analysis of TC was 0.62 %/year in peripheral blood leukocytes (PBL) from 41 normal volunteers. Concomitant analyses of TC and average telomere length in 32 various tissues revealed that both values were significantly correlated (r=0.45, P=0.009). In order to compare TC in the liver with respect to chronic inflammation, the value was divided by TC in PBL from the same donor. The ratio was defined as relative TC (RTC). There was a statistically significant decrease of RTC in CI comparing with in ND (P=0.03). Furthermore, RTC in SL was significantly lower than that in CI (P=0.02). The reduction was not associated with histology activity index. In contrast, RTC in HOC indicated higher or lower than that in the corresponding SL, and was not associated with an extent of invasion to the portal vein. These observations suggest that RTO value in liver tissues may digitally indicate a replicative history of hepatocyte under chronic inflammation, and a risk of HOC development. Less
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