Studies on genomic instability of gastric cancer

尽管发病率在下降，胃癌仍然是世界范围内癌症死亡的主要原因。最近，在新西兰的三个FGC种类中，发现了e -钙粘蛋白基因的种系突变。为了确定E-cadherin基因的nerline突变是否也是日本家族性胃癌易感性的原因，我们采用pcr -单链构象多态性分析方法分析了来自14种日本家族性胃癌（FGC）的16例患者的E-cadherin所有外显子。然而，没有检测到种系突变，表明E-dacherin基因突变对FGCs的易感性在日本病例中并不常见。p14 ^<ARF>通过另一种剪接过程产生，该剪接过程将p16^<1NK4a>的第一个外显子Ia替换为位于Ia外显子上游> 15kb的外显子Ib，已被证明具有生长抑制因子的功能。我们检测了11种胃癌细胞系p14 ^<ARF>基因的mRNA表达、纯合缺失、突变和启动子甲基化。7株扩散型细胞系中有5株未检测到mRNA的表达。除一株表达水平较低外，其余肠细胞系均表现出正常表达水平。在未表达的3株细胞系中，3株（MKN45、NUGC-2和NUGC-4）和1株（KATO III）分别表现出p14 ^<ARF>基因的纯合缺失和甲基化。8株细胞系p14 ^<ARF>基因全编码区未发现突变，未发现纯合缺失。我们的研究结果表明，p14 ^<ARF>基因在扩散型胃癌细胞株中（5/ 7,71.4%）比在肠道细胞株中（0/4,p =0.022）更频繁地因纯合缺失或甲基化而失活。我们还分析了62例原发性胃癌的p14 ^<ARF>启动子区的甲基化状态，发现弥漫性胃癌的甲基化频率（15/33,45.5%）往往高于肠癌（7/28,25%）。因此，p14 ^<ARF>的改变可能参与了弥漫性胃癌的发生。

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.