| Summary: | 博士 === 國防醫學院 === 生命科學研究所 === 93 === Abstract
Liver cancer is the sixth most common cancer worldwide especially in tropical Africa and south-east Asia. In Taiwan, hepatocellular carcinoma (HCC) is the leading cause of cancer-related mortality in the past decades. For revealing therapeutic and diagnostic targets in HCC treatment, we decided to search and clone cancer genes involved in HCC tumorgenesis. In our laboratory, we previously reported genome-wide loss of heterozygosity (LOH) analysis in HCC genome and revealed 33 minimal deletion regions (MDRs). To further identify putative tumor suppressor genes (TSGs), a homozygous deletion (HD) screening in HCC cell lines was processed by scanning the MDRs. A novel 1-cM (1.8Mb) homozygous deletion (HD) on 13q12.11 was identified in a HCC cell line, SK-Hep-1, and confirmed by high-density genetic markers and Southern blotting analysis. After increasing microsatellite marker density on 13q12.11 for LOH analysis, the frequency of this HD region is 52% in 48 HCC patients. Interestingly, the occurrence of LOH in 13q12.11 HD region is significantly associated with early-onset HCC patients by Mann-Whitney test (P=0.023). Since the HD region is a gene-rich area, 76 transcripts were predicted in the HD by the combination of prediction in NCBI, EnsEMBL and Vega databases. Firstly, 17 known or predicted genes were selected to analyze the information of transcripts, blast the sequence in various databases, and then compare the expression of these 17 candidates in more than 20 HCC tissue pairs. Ten of these genes exhibited down-regulation in HCC tissue were applied to assay their function of tumor suppression including cell growth, migration and anchorage independent growth (AIG) assays. Finally, MPP8, IL17D and TG737 were showed to inhibit the colony formation in AIG assay and GJB2 was identified to control both cell growth and migration. Our results and previous genetic studies provided lines of evidence to support that the HD region on 13q12.11 is a novel tumor suppressor locus for HCC. The results of gene expression analysis and functional assays identified TG737, IL17D, MPP8 and GJB2 are potential TSGs in the HD region.
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