Droufakou S, Deshmane V, Roylance R, Hanby A, Tomlinson I, Hart I R
Richard Dimbleby Department of Cancer Research/Imperial Cancer Research Fund, Rayne Institute, St. Thomas' Hospital, London, United Kingdom.
Int J Cancer. 2001 May 1;92(3):404-8. doi: 10.1002/ijc.1208.
The cell-cell adhesion receptor gene E-cadherin (CDH1) is expressed by epithelial cells, in which it mediates adhesion and morphogenesis. Invasive lobular carcinoma (ILC) characteristically infiltrates diffusely as single cells; by immunohistochemistry, many of these tumours lack E-cadherin expression. In the present study we investigated various ways in which loss of function of the E-cadherin gene could occur in ILCs, namely, promoter methylation, mutation and allelic loss. We analysed 22 ILCs and found 12 (55%) E-cadherin-negative samples by immunohistochemical analysis. Methylation-specific polymerase chain reaction (PCR) showed that 17/22 (77%) of these tumours had methylation of the CDH1 promoter, including 11/12 (91%) of the E-cadherin-negative tumours. All 16 exons of E-cadherin (including intron-exon boundaries) were amplified from chromosomal DNA and screened for mutations by conformation-sensitive gel electrophoresis (CSGE). Bands with altered mobility were analysed by direct sequencing. We identified five frameshift mutations, which resulted in downstream stop codons and one splice site mutation in six different tumours (29%). Loss of heterozygosity (LOH) was assessed using microsatellite markers, and 9/18 (50%) informative tumours showed LOH. We conclude that most ILCs show genetic or epigenetic changes affecting the E-cadherin gene and that many of these tumours lack E-cadherin expression. In all cases in which there was loss of expression, this was consistent with biallelic inactivation of CDH1 by promoter methylation, mutation or allelic loss in any combination.
细胞间黏附受体基因E-钙黏蛋白（CDH1）由上皮细胞表达，在这些细胞中它介导黏附和形态发生。浸润性小叶癌（ILC）的特征是作为单个细胞弥漫性浸润；通过免疫组织化学检测，许多此类肿瘤缺乏E-钙黏蛋白表达。在本研究中，我们调查了ILC中E-钙黏蛋白基因功能丧失可能发生的各种方式，即启动子甲基化、突变和等位基因缺失。我们分析了22例ILC，通过免疫组织化学分析发现12例（55%）样本E-钙黏蛋白呈阴性。甲基化特异性聚合酶链反应（PCR）显示，这些肿瘤中有17/22（77%）存在CDH1启动子甲基化，其中包括11/12（91%）的E-钙黏蛋白阴性肿瘤。从染色体DNA中扩增E-钙黏蛋白的所有16个外显子（包括内含子-外显子边界），并通过构象敏感凝胶电泳（CSGE）筛选突变。对迁移率改变的条带进行直接测序分析。我们在6个不同肿瘤（29%）中鉴定出5个移码突变，这些突变导致下游终止密码子以及1个剪接位点突变。使用微卫星标记评估杂合性缺失（LOH），18例信息充分的肿瘤中有9例（50%）显示出LOH。我们得出结论，大多数ILC显示出影响E-钙黏蛋白基因的遗传或表观遗传变化，并且这些肿瘤中有许多缺乏E-钙黏蛋白表达。在所有表达缺失的病例中，这与CDH1通过启动子甲基化、突变或等位基因缺失的任何组合导致的双等位基因失活一致。
