Putative Tumor Suppressor Gene Loci onChromosome 20q in Intrahepatic Cholangiocellular Carcinoma that were Found by Microsatellite Marker Analysis

ABSTRACT

PURPOSE: Intrahepatic cholangiocellular carcinoma (ICC) is the second most common malignant tumor in the liver, and it arises from epithelial cells in the intrahepatic bile duct. While the reported risk factors include liver fluke infection, hepatolithiasis and sclerosing cholangitis, the genetic mechanisms involved in the development of ICC are not well understood, and only a few cytogenetic studies of ICC have been published. We recently found genetic imbalance on chromosome 20q in ICC with using Comparative Genomic Hybridization. So, we tried to find gene loci on chromosome 20q. (ED note what kind of loci were you looking for) METHODS: We used 16 fresh frozen ICC tumor tissues and the paired normal liver tissues for DNA extraction. A set of primers for 10 microsatellite loci on chromosome 20q13-qter, based on an updated GeneMap99 and Ensemble, was purchased from Research Genetics. The markers selected for testing exhibited high levels of heterozygosity and relatively uniform distributions. Loss of heterozygosity (LOH) was analyzed by an automatic DNA analyzer. Using the Ensemble Web site, mining of putative tumor suppressor genes were developed between microsatellite markers that showed LOH. RESULTS: In one case, microsatellite instability (MSI) was found in all the markers except D20S196, and MSI was found in only one marker, d20S196, in another case. (Ed note check this and it wasn't clear.) The most frequent region which have LOH on chromosome 20q13-qter was on D20S109 and D20S196, and their invidence was 12.5%. (ED note the last part of the sentence makes no sense at all. You have to rewrite it.) D20S174, D20S107, D20S170, D20S96 and D20S119 were 6.3% and D20S836, D20S886 and D20S were 0%. (ED note this sentence also makes no sense. They were 6% and 0% of what?) We found eight genes between D20S109 and D20S196 PTPN1, QSNf41 HUMAN, CT175 HUMAN, PARD6B, BCAS4, TMSL6, ADNP and DPM1. Among these, PTPN1, PARD6B and BCAS4 are well known oncogenes, so the other five genes are thought to be putative tumor suppressor genes. CONCLUSION: Using this approach, we identified two distinctive allelic losses defined by microsatellite markers as follows; D20S109 and D20S196. We identified five genes which can make contribution to the development or progression of intrahepatic cholangiocellular carcinoma. Further study will be carried out to confirm these genes have a critical role in the development or progression of intrahepatic cholangiocellular carcinoma using immunohistochemical study or other molecular biology work.