Studies on genomic instability of gastric cancer

尽管发病率下降，胃癌仍然是全球癌症死亡的主要原因。最近，在新西兰的三个FGC激酶中，发现了E-cadherin基因的种系突变，为了确定E-cadherin基因的种系突变是否也是日本FGC的易感性的原因，我们对来自14个日本家族性胃癌（FGC）激酶的16个患者的E-cadherin基因的所有外显子进行了PCR-单链构象多态性分析。然而，未检测到生殖系突变，表明在日本病例中，由E-dacherin基因突变引起的FGC易感性并不常见。p14 ^是通过选择性剪接过程产生的，该过程用位于外显子Ia上游&gt; 15kb的外显子Ib取代p16 ^的第一个外显子Ia，已被证明具有生长抑制剂的功能。<ARF><1NK4a>我们检测了11个胃癌细胞系p14 ^基因的mRNA表达、纯合性缺失、突变和启动子甲基化。<ARF>在7个弥漫型细胞系中，有5个未检测到mRNA表达。所有肠细胞系显示正常水平的表达，除了一个具有低水平的表达。在3个无表达的细胞系中，3个（MKN 45、NUGC-2和NUGC-4）和1个（KATO III）分别显示p14 α基因的纯合缺失和甲基化。<ARF>在8个无纯合缺失的细胞系中，p14 ^基因的整个编码区均未发现突变。<ARF>结果表明，弥漫型胃癌细胞系中p14 ^基因的纯合缺失或甲基化失活率（5/7，71.4%）高于肠型胃癌细胞系（0/4，P = 0.022）。<ARF>我们还分析了62例原发性胃癌p14 ^启动子区域的甲基化状态，弥漫型胃癌的甲基化频率（15/33，45.5%）高于肠型胃癌（7/28，25%）。<ARF>因此，p14 ^改变可能参与弥漫型胃癌的发生。<ARF>

Despite a decreasing incidence, gastric cancer remains a major cause of cancer death worldwide. Recently, in three FGC kindreds in New Zealand, germ-line mutations of the E-cadherin gene were found. To determine whether or not nerm-line mutation of the E-cadherin gene is also responsible for the predisposition to Japanese FGC, we analyzed all of the exons of E-cadherin by PCR-single-strand conformational polymorphism analysis in 16 patients from 14 Japanese familial gastric cancer(FGC)kindreds. However, no germ-line mutation was detected, suggesting that a predisposition to FGCs by E-dacherin gene mutation is infrequent in Japanese cases.p 14^<ARF>, generated through an alternative splicing process that replaces the first exon, Ia, of p16^<1NK4a> with exon Ib, located > 15kb upstream of exon Ia, has been shown to function as a growth suppressor. We examined 11 gastric cancer cell lines for mRNA expression, homozygous deletion, mutation, and promoter methylation of the p 14^<ARF> gene. No mRNA expression was detected in 5 of the 7 diffuse-type cell lines. All intestinal cell lines displayed normal levels of expression except for one with a low level of expression. Of the 3 cell lines without expression, 3(MKN45, NUGC-2, and NUGC-4)and 1(KATO III)displayed homozygous deletion and methylation of the p 14^<ARF> gene, respectively. No mutation was found in the whole coding region of the p 14^<ARF> gene in 8 cell lines without homozygous deletion. Our results indicate that the p 14^<ARF> gene is more frequently inactivated by homozygous deletion or methylation in diffuse-type gastric cancer cell lines(5/7, 71.4%)than in intestinal ones(0/4, P=0.022). When we also analyzed 62 primary gastric cancers for the methylation status of the p 14^<ARF> promoter region, the methylation frequency tended to be higher in diffuse-type gastric cancers(15/33, 45.5%)than in intestinal ones(7/28, 25%). Thus, p 14^<ARF> alterations might be involved in diffuse-type gastric carcinogenesis.