Analysis of the numerical aberration of chromosome 17 and 18 on frozen section of gastric adenocarcinomas

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This study was designed to facilitate understanding of the process of gastric cancer progression by clarifying numerical changes of chromosomes 17 and 18 on gastric cancer sections. For DNA hybridization, we chose two chromosome-specific alpha-centromeric probes : one for chromosome 17 on whose short arm, tumor suppressor gene p53 located and the other for chromosome 18 on whose long arm tumor suppressor gene DCC located. In addition, to know the relationship between the numerical changes of these chromosomes and allelic loss of p53 and DCC,PCR-LOH was done using microsatelite polymorphism located at or linked to these genes.In order to dissolve technical problems, we first compared the results of hybridization done by using frozen sections, and by formalin-fixed paraffin-embedded sections. We confirmed that the hybridization was not less efficient when formalin-fixed paraffin-embedded tissues were used than when frozen sections were used. Second, we compared two detection methods, i.e … More ., fluorescence detection and peroxidase detection. By the former method, the specimen had disadvantage of fading of fluorescences, however because virtually no background staining, the enumeration was easier than when peroxidase detection was applied. Thus finally we chose fluorescence in situ hybridization (FISH) on formalin-fixed paraffin-embedded section as the regular detection tmethod.The 33 tumors which had allelic imbalance of p53 by PCR-LOH,and 20 tumors which had allelic imbalance of DCC were examined by FISH for numerical aberrations of chromosomes 17 and 18, respectively. FISH for chromosome 17 was successful in 28 tumors and for chromosome 18 in 18 tumors. Polysomy 17 was found in 14 and polysomy 18 in 7. No monosomy 17 was found, however monosomy 18 was found in 2 tumors. By PCR-LOH,the distinction of allelic imbalance due to numerical aberrations from those due to the selective physical deletion of genetic loci was impossible, although it is easy to detect numerical chromosomal aberrations by FISH.In this study it is shown that FISH is a useful tool to clarify chromosomal changes on formalin-fixed paraffin-embedded specimen. Less