Exhaustive Studies on Genomic Changes in Gastric Cancer and Precancerous COnditions

本研究的最初目的是研究胃癌和癌前病变上皮细胞的基因组变化。然而，我们关注的是胃癌的变化，因为我们找不到后者的典型变化。应用覆盖50k个SNP基因座的寡核苷酸芯片，对34个人胃癌细胞系的基因拷贝数变化进行了详尽的分析。在26个细胞系中发现26个基因座纯合子缺失。拷贝数扩增的频率更高，在总共20个细胞系中的31个座位上发现了高级别扩增，至少有两个细胞系的拷贝数超过5个。其中约有一半的基因座以前没有在胃癌中报道过。其中10个基因用于拷贝数扩增，4个基因用于杂合性缺失(LOH)检测。用激光显微切割技术从人胃癌组织中分离癌组织，用实时定量聚合酶链式反应和微卫星标记分析基因的变化，发现这些基因在人胃癌组织中也是常见的。与临床资料比较，有淋巴结转移或血管侵犯的晚期患者更易出现拷贝数扩增和杂合性缺失。目前研究发现的那些与胃癌相关的基因可能在胃癌的发生中起作用。此外，在I/II期病例中，频繁的杂合性缺失与较短的总生存期显著相关。某些基因杂合性缺失的检测可能有助于鉴别高危患者。

The original aim of this study was to investigate genomic changes in gastric cancer and precancerous gastric epithelium. However, we focused on the changes in gastric cancer because we could not find changes typical to the latter. Changes in the copy number of genes were exhaustively evaluated with oligonucleotide microarray that covered 50k SNP loci in 34 human gastric cancer cell lines. Homozygous deletion was found at 26 loci in a total of 26 cell lines. Copy number amplification was found much more often, and high-grade amplification, more than five copies in at least two cell lines, was found at 31 loci in a total of 20 cell lines. About one half of these loci were not previously reported in gastric cancer. Among the genes contained in these regions, 10 genes and 4 genes were selected for the examination of copy number amplification and that of loss of heterozygosity (LOH), respectively. Cancer tissue was separated from human gastric cancer specimens by using laser microdissection, and the changes in the genes were analyzed with quantitative real-time PCR and evaluation of microsatellite markers, which were found to be frequent also in human gastric cancer tissues. By comparing with clinical data, copy number amplification and LOH were more frequently found in advanced cases with lymph node metastasis or vascular invasion. Those genes the association of which with gastric cancer was found in the current study may play a role in gastric carcinogenesis. In addition, frequent LOH in cases at Stage I/II was significantly associated with shorter overall survival. Determination of LOH of certain genes may be useful in differentiating high-risk patients.