Allele-specific mutations involved in the pathogenesis of endemic gallbladder carcinoma in Chile.

Although gallbladder carcinoma is one of the most frequent neoplasms in Chile, there is limited information about the molecular changes involved in its pathogenesis. We investigated the incidence of ras gene mutations and loss of heterozygosity (LOH) at the following genes/loci: p53, DCC, rb, 5q 3p, 8p, and 9p. We precisely microdissected 194 relevant areas from paraffin-embedded microslides from 25 gallbladder carcinomas and their accompanying nonneoplastic lesions (which were present in 15 cases) from patients in Chile. The specimens were analyzed by PCR-based assays for LOH, and we designed a RFLP method for ras mutations and immunohistochemistry for p53 protein overexpression. We determined that LOH at p53 (91%), 9p (50%), 8p (44%) and DCC (31%) are frequent events and that LOH at p53, 9p, and DCC are early events, while ras mutations and LOH at 3p, rb, and 5q occurred occasionally. LOH at p53 occurred more frequently and earlier than protein overexpression. The mean number of mutations present in invasive carcinomas was 2.1, and in six cases, LOH at the p53 gene was the sole mutation detected. The same allele was lost in 61 (93%) of 71 nonneoplastic foci as in the corresponding invasive carcinomas for all four mutations studied. The odds of this occurring by chance are approximately 4 x 10(-15). Although clonality cannot be excluded, allelic loss appears to be highly directed, but the mechanism for allele-specific mutations remains to be determined.

尽管胆囊癌是智利中最常见的肿瘤之一，但有关其发病机理中涉及的分子变化的信息有限。我们研究了以下基因/基因座：p53，dcc，rb，5q 3p，8p，8p和9p，在以下基因/基因座上研究了RAS基因突变的发生率和杂合性丧失（LOH）。我们精确地从25个胆囊癌及其伴随的非肿瘤病变（在15例中存在于15例）中，精确地从石蜡包裹的微层中的194个相关区域来自辣椒的患者。通过基于PCR的LOH分析样品，我们设计了一种用于RAS突变和免疫组织化学的RFLP方法，用于p53蛋白过表达。我们确定在p53（91％），9p（50％），8p（44％）和DCC（31％）的LOH是频繁的事件，而在p53、9p和DCC处的LOH是早期事件，而RAS突变和LOH则是在3p时，RB和5Q偶尔发生。 p53处的LOH比蛋白质过表达更频繁，更早。浸润性癌中存在的平均突变数为2.1，在六例p53基因处的LOH是唯一突变。在71个非塑性灶中的61个（93％）中，同样的等位基因与所研究的所有四个突变的相应浸润性癌相同。偶然发生这种情况的几率约为4 x 10（-15）。尽管无法排除克隆性，但等位基因损失似乎是高度定向的，但是等位基因特异性突变的机制仍有待确定。