| Objective:Hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH) are benign focal lesions occuring in normal or nearly normal liver. HCA has been found to be neoplastic, characterized by alterations in a few molecular pathways. The clonality status of FNH remains to be clarified, and its pathogenesis is largely unknown. In the current study, a comprehensive observation was carried out on FNH and HCA for loss of heterrozygosity (LOH) using 57 microsatellite markers, where allelic imbalances had been associated to HCC development. Possible roles of the genetic alterations in hepatotocarcinogenesis were evaluatedMethods:5 classical FNH lesions,9 HCAs and 18 well-differentiated HCCs (Edmondson grade I or II) were used in this study. A total number of 57 microsatellite markers were examined. The sequences were amplified through polymerase-chain reaction, and LOH were visualized on denatured polyacrylamide gels by silver staining. Expression of P-catenin was assessd in 9 HCAs by immunohistochemistry.Results:All of the 18 HCCs were found in livers with chroni hepatitis B and cirrhosis, with coinfection of hepatitis C virus found in one of the cases. LOH was demonstrated in all of the HCCs examined. Numbers of loci revealed in each case ranged from 0 to 12, with their average being 4. Among the 57 loci,33 (58%) showed allelic imbalances in HCCs, with highly frequent (≥30%) LOH detected in 6 loci located on 6q,8p, 11p,16q and 17p.Liver cell dysplasia (small-cell change, SCC) was observed in 2 out of 9 HCAs examined. A memebranous, rather than cytoplasmic or nuclear, immunoreactivity was demonstrated in all of the HCA. LOH was also detected in these lesions. Numbers of loci with LOH in each HCA lesion ranged from 1 to 5, with their average being 3. Sixteen loci (28%) were affected, with 8, on 11p,13q and 17p, showing highly frequent imbalances.LOH was not found in the 5 FNH lesions as detected as a whole. However, foci of altered hepatocytes (FAH) and nodules of altered hepatocytes (NAH) composed mainly of clear cells were identified in these lesions. NAH were found to occupy majority of the larger nodules, sizing>1 mm in diameter, within FNH. NAH were microdissected from an FNH lesion showing many well-circumscribed larger nodules. A total number of 25, NAH were obtained, and amplification was successful for most of the 57 loci in 13 of them. Numbers of loci ranged from one to 6, with their average being 4. Twenty-one loci (37%) were affected, with 6, located on 8p, 11p,13q and 17p, showing highly frequent LOH.NAH, HCA and HCC were found to be different in their LOH profiles, with LOH detected in highest frequencies at the loci D8S298 (70%), D11S1301 (75%) and D6S1008 (50%), respectively. Distribution pattern of LOH in NAH was largely similar to that in HCA. However,8p was affected more frequently in the former than in the latter lesion. In addition, they were also shown to be different in the 16q alterations, with 5 of the 7 loci affected in NAH and only one in HCA.Conclusions:Allelic imbalances were found in well-differentiated HCC, with highly frequent LOH detected on chromosomal arms 6q,8p, 11p,16q and 17p. LOH was also identified in HCA, but it affected fewer loci than in HCC samples, detected in high frequencies at the loci on 11p, 13q and 17p. No LOH was found in whole FNH lesions, which is in agreement with its polyclonality as demonstrated previously. However, frequent occurrences of FAH and NAH were demonstrated within the lesions. The microsatellite sequences from the microdissected NAH were also examined. LOH was detected in all of the lesions at lest at one locus, indicating their monoclonalality. Chromosomal arms 8p, 11p,13q and 17p were affected in NAH in high frequencies, the distribution pattern being largely similar to HCA. Different LOH profiles were found in different NAH, indicating that they developed independently. These data hint that the nodular pattern characterized by classical FNH may reflect the clustered occurrence within the lesion.
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