韧带样型纤维瘤病Wnt通路中APC/β-catenin基因异常

Abnormalities of APC gene/β-catenin gene in Wnt pathway in desmoid-type fibromatosis

背景与目的:APC和β-caten in基因作为W nt通路上重要的成员,其异常在肿瘤的发生、发展过程中起着重要作用。本研究分析了韧带样型纤维瘤病中APC和-βcaten in基因突变,探讨W nt通路中APC/β-caten in基因异常在肿瘤发生中的作用。方法:采用PCR-DHPLC-Sequence的方法分析韧带样型纤维瘤病中APC和-βcaten in基因的突变,免疫组织化学EnV ision+两步法检测β-caten in、cyc linD1和c-myc蛋白的表达。结果:APC基因发生碱基置换突变,均为体系突变,突变率为26.1%(18/69),突变不产生截短APC蛋白。β-caten in基因发生碱基转换,突变率为18.8%(13/69),导致第3外显子的codon41处苏氨酸磷酸化位点转变为丙氨酸。-βcaten in蛋白异常表达阳性率为47.8%(33/69),在APC、β-caten in基因突变阳性和阴性病例间,其异常表达阳性率没有显著差异。β-caten in异常表达阳性病例的c-myc蛋白阳性率(69.7%,23/33)显著高于阴性病例的c-myc阳性率(22.2%,8/36),两者之间有正相关关系(Pearson's r=0.477),而cyc linD1的表达没有显示出这种相关性和差异。结论:韧带样型纤维瘤病中APC、β-caten in基因存在体系突变,β-caten in蛋白存在异常表达,可能引起c-myc表达增加。韧带样型纤维瘤病中W nt通路存在异常,可能在肿瘤发生中起重要作用。

Background and purpose： The APC gene and β-catenin gene play import roles in Wnt pathway and their abnormalities could be the cause for the tumorigenesis of desmoid-type fibromatosis. To investigate the disorder of Wnt signal transduction pathway in tumorigenesis, we studied the adenomatous polyposis coli （APC） gene and β-catenin gene mutations in desmoid-type fibromatosis. Methods： The APC and β-catenin gene mutations were analyzed using methods of denaturing high performance liquid chromatography and direct sequence after the PCR reaction. The proteins of β-catenin, cmyc, and cyctinD1 were detected using immunohistochemistry . Results： Somatic mutations of APC gene were found in 18 of 69（ 26.1% ） desmoid-type fibromatoses, all the mutations were substitution and could not result in truncated APC protein. Somatic mutations of β-catenin gene were detected in 13 of 69 （ 18.8% ） and the mutations al codon 41 in exon 3 involved threonine so that it is implicated in the degradation of β-eatenin. The abnormal expression of β-catenin protein was in the cytoplasm and nucleus （47.8%, 33/69） and had no significant correlation with the mutations of APC or β-catenin gene. The group with abnormal β-catenin expression showed a higher e-mye protein expression than those without, the difference was statistically significant. Neither c-myc protein nor eyclinDl protein expression showed difference or correlation with the abnormal expression of β-catenin protein. Conclusions： There are somatic mutations of APC and β-catenin gene in desmoidtype fibromatosis, abnormal expression of β-catenin protein increase can be observed in the cytoplasm and nucleus, and results in the higher expression of c-mye protein. The Wnt signaling pathway disorder in desmoid-type fibromatosis plays a critical role in tumorigenesis.