Role of b-Catenin Wingless/Wnt Pathway in Liver Carcino

人类肝癌可分为两大类，分别以-catenin激活和基因组不稳定性为特征。我们研究了b-连环蛋白激活和基因组不稳定性在小鼠肝癌发生的顺序步骤中的作用。通过PCR和测序筛选，对大量来自c-myc、TGF-、E2F-1、c-myc/TGF-和c-myc/E2F-1转基因小鼠的癌前和癌性肝脏病变进行-catenin突变和缺失分析。免疫组化（IHC）检测-catenin的活化。RAPD方法用于评估相同病变的总体基因组不稳定性。通过微卫星分析确定受基因组改变影响的染色体位点。甲胎蛋白（AFP）的表达通过免疫组化检测作为预后指标。来自转基因小鼠系的肝脏肿瘤可分为两类。第一类，最好的例子是c-myc/E2F-1 hcc，其特征是在相对稳定的基因组和低AFP水平存在的情况下-catenin激活频率高。第2类，以c-myc/TGF- hcc为代表，其-catenin激活率较低，但基因组不稳定，1、2、4、6、7、9、12、14、x染色体的杂合性反复丧失。基因组不稳定在早期发育不良阶段就很明显，并伴随AFP表达升高。数据表明-catenin激活和基因组不稳定性决定了小鼠肝脏肿瘤发展过程中的两个主要遗传事件，与人类hcc相似。这些转基因小鼠为阐明人类HCC的分子基础提供了合适的遗传系统。

Human liver cancer can be divided into two broad categories that are characterized by activation of -catenin and genomic instability, respectively. We investigated the role of b-catenin activation and genomic instability in the sequential steps of mouse hepatocarcinogenesis. A large collection of preneoplastic and neoplastic liver lesions from c-myc, TGF- , E2F-1, c-myc/TGF- and c-myc/E2F-1 transgenic mice was analyzed for -catenin mutations and deletions by PCR and sequencing screening. Activation of -catenin was investigated by immunohistochemistry (IHC). The RAPD method was used to assess the overall genomic instability in the same lesions. Chromosomal loci affected by genomic alterations were determined by microsatellite analysis. Expression of alpha-fetoprotein (AFP) was determined by IHC as a prognostic marker. Liver tumors from the transgenic mouse lines could be divided in two categories. The first category, best exemplified by c-myc/E2F-1 HCCs, was characterized by high frequency of -catenin activation in the presence of a relatively stable genome and low AFP levels. The second category, represented by c-myc/TGF- HCCs, displayed low rate of -catenin activation but extensive genomic instability with recurrent loss of heterozygosity at chromosomes 1, 2, 4, 6, 7, 9, 12, 14, X. The genomic instability was evident from early dysplastic stage and occurred concomitantly with elevated expression of AFP. The data indicate that -catenin activation and genomic instability define two major genetic events during development of mouse liver tumors, similar to those described for human HCCs. These transgenic mice provide suitable genetic systems for elucidating the molecular basis of human HCC.