儿童肾母细胞瘤WT1基因突变四例报道

Four new cases with WT1 gene mutations in Chinese patients with Wilms＇ tumor

目的研究儿童肾母细胞瘤患者WT1基因的突变类型及突变频率。方法应用聚合酶链反应（PCR）扩增出54例儿童肾母细胞瘤患者WT1基因全部10个外显子及其相邻内含子序列，经纯化后进行PCR产物直接测序。结果4例患者WT1基因分别存在3个杂合无义突变及1个纯合错义突变。例1患者WT1基因7号外显子第1006位碱基A—T杂合突变，造成第336号氨基酸由赖氨酸转变为终止密码子，即K336X。例2患者WT1基因9号外显子第1168位碱基C—T杂合突变，造成第390号氨基酸由精氨酸转变为终止密码子，即R390X。例3患者WT1基因6号外显子第814位碱基G—T杂合突变，造成第272号氨基酸由谷氨酸转变为终止密码子，即E272X。例4患者WT1基因10号外显子第1228位碱基A—G纯合突变，造成第410号氨基酸由丝氨酸转变为甘氨酸，即S410G。结论散发的中国儿童。肾母细胞瘤患者册1基因外显子突变的发生率与国外报道相近，检测到的4例突变患者中3例为无义突变、1例为错义突变。

Objective Wilms＇ tumor （WT） is the most common malignant renal tumor in childhood. The WT1 gene located at llp13 was identified in 1990 as a tumor suppressor gene important in the development in WT. The WT1 gene consists of 10 exons, with exons 1 to 6 encoding an N-terminal proline- and glutamine-rich transactivational domain, and exons 7 to 10 eneoding a C-terminal zinc-finger domain involved in DNA binding. In China we know little about the frequency and genotype of WT1 mutations in Chinese WT patients. This study aimed to determine the frequency and genotype of WT1 mutations in children with nonsyndromic WT in China. Methods We collected peripheral blood of WT patients treated in Beijing Children＇s Hospital. Cenomic DNA of 54 WT patients was isolated from blood samples. All coding WT1 exons and their flanking intronic sequences were amplified by PCR method. The amplified PCR products from all individuals were then subjected to automatic DNA sequencing. Results Four different constitutional WT1 mutations were identified in four children. Three mutations are predicted to produce truncated protein. One mutation is missense. Of the four mutations, three had not been reported before. Patient 1 had a 1006 A 〉 T transition in exon 7, which caused 336Lys to become a stop codon （K336X）. DNA sequence analyses in patient 2 indicated the point mutations in exon 9 which was a 1168 C 〉 T substitution and caused ^390Arg to become a stop codon （R390X）. It indicated a point mutations in exon 6 in patient 3 which was a 814 G 〉 T substitution and resuited in 272 Glu to become a stop codon （E272X）. In patient 4 there was a homozygous mutation in exon 10. The mutation was a 1228 A 〉 G substitution and resulted in ^410Ser to become a Gly codon （S410G）. Conclusion Constitutional WT1 mutations occur at a low frequency （7.4%） in Chinese patients with Wilms＇ Tumor. It is similar to the results of overseas study. Four WT1 gene mutations were confirmed, three were nonsense, one was missense.