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胃上皮的基因组变化。然而，我们关注的是胃癌的变化，因为我们没有发现后者的典型变化。利用寡核苷酸微阵列技术对34个人胃癌细胞系中50k个SNP位点的基因拷贝数变化进行了详尽的评估。在26个细胞系中发现了26个纯合缺失位点。拷贝数扩增更为常见，在20个细胞系的31个位点中发现了高度扩增，至少在两个细胞系中发现了超过5个拷贝。这些基因座中约有一半以前未在胃癌中报道过。在这些区域所含的基因中，选取10个基因进行拷贝数扩增和4个基因进行杂合性损失（LOH）检测。采用激光显微解剖法从人胃癌标本中分离出癌组织，采用实时荧光定量PCR和微卫星标记评价分析基因的变化，发现这些基因在人胃癌组织中也很常见。通过临床资料对比，拷贝数扩增和LOH多见于淋巴结转移或血管侵犯的晚期病例。本研究中发现的与胃癌相关的基因可能在胃癌发生中起作用。此外，I/II期病例中频繁的LOH与较短的总生存期显著相关。测定某些基因的LOH可能有助于区分高危患者。

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.