Saito Tsuyoshi, Oda Yoshinao, Kawaguchi Ken-ichi, Tanaka Kazuhiro, Matsuda Shuichi, Tamiya Sadafumi, Iwamoto Yukihide, Tsuneyoshi Masazumi
Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan.
Lab Invest. 2002 Jan;82(1):97-103. doi: 10.1038/labinvest.3780399.
We screened for genetic alterations of adenomatous polyposis coli (APC) and beta-catenin genes in 17 frozen specimens from 12 cases of sporadic desmoid tumors and then subdivided these cases into two groups according to the results of mutational analysis. We further examined mRNA expression of beta-catenin and cyclin D1 by TaqMan PCR and compared the mRNA expression within both groups. Single-strand conformation polymorphism analysis followed by DNA direct sequencing revealed beta-catenin mutation in 3 of 12 cases (6 of 17 specimens), whereas no APC missense mutations in the mutation cluster region were found. TaqMan PCR revealed extremely higher mRNA expression of beta-catenin and cyclin D1 in desmoid tumors, compared with those of normal skeletal muscles. In the beta-catenin mutated group, cyclin D1 mRNA expression was significantly higher than that of the beta-catenin wild-type group (p = 0.0120, Mann-Whitney U test). In addition, in the beta-catenin mutated group, beta-catenin mRNA expression was also significantly higher than that of the beta-catenin wild-type group (p = 0.0036, Mann-Whitney U test). All cases of desmoid tumors showed detectable beta-catenin nuclear expression immunohistochemically. These results suggest that a continuously elevated beta-catenin protein level caused by the beta-catenin mutation itself may have a stronger power that can transactivate transcription in vivo. Furthermore, the results provide a possible association between higher beta-catenin mRNA expression and mutated beta-catenin in sporadic desmoid tumors. This may suggest that the beta-catenin gene may be up-regulated by mutated or continuously elevated beta-catenin protein, that is, the beta-catenin gene may also be one of the targeted genes in the APC-beta-catenin-Tcf pathway.
我们对12例散发性硬纤维瘤的17份冷冻标本进行了腺瘤性息肉病大肠杆菌（APC）和β-连环蛋白基因的基因改变筛查，然后根据突变分析结果将这些病例分为两组。我们进一步通过TaqMan PCR检测β-连环蛋白和细胞周期蛋白D1的mRNA表达，并比较两组内的mRNA表达。单链构象多态性分析后进行DNA直接测序，发现12例中有3例（17份标本中的6份）存在β-连环蛋白突变，而在突变簇区域未发现APC错义突变。TaqMan PCR显示，与正常骨骼肌相比，硬纤维瘤中β-连环蛋白和细胞周期蛋白D1的mRNA表达极高。在β-连环蛋白突变组中，细胞周期蛋白D1的mRNA表达明显高于β-连环蛋白野生型组（p = 0.0120，Mann-Whitney U检验）。此外，在β-连环蛋白突变组中，β-连环蛋白的mRNA表达也明显高于β-连环蛋白野生型组（p = 0.0036，Mann-Whitney U检验）。所有硬纤维瘤病例免疫组化均显示可检测到β-连环蛋白核表达。这些结果表明，由β-连环蛋白突变本身导致的β-连环蛋白蛋白水平持续升高可能具有更强的体内转录激活能力。此外，结果提示散发性硬纤维瘤中β-连环蛋白mRNA表达升高与β-连环蛋白突变之间可能存在关联。这可能表明β-连环蛋白基因可能被突变的或持续升高的β-连环蛋白蛋白上调，即β-连环蛋白基因也可能是APC-β-连环蛋白-Tcf通路中的靶基因之一。
