Bilateral Wilms Tumor and Early Presentation in Pediatric Patients Is Associated with the Truncation of the Wilms Tumor 1 Protein

Center for Transplant and Renal Research, Westmead Millennium Institute, The University of Sydney, New South Wales, Australia.
The Journal of pediatrics (Impact Factor: 3.79). 02/2013; 163(1). DOI: 10.1016/j.jpeds.2012.12.080
Source: PubMed


To investigate the frequency of constitutional Wilms tumor 1 gene (WT1) abnormalities in children with bilateral Wilms tumor (WT) and the age of tumor onset in patients with a mutation.

Study design:
Eight patients with bilateral WT were studied. High-resolution melting and direct sequencing were used to screen for the WT1 gene. Western blotting was performed to determine whether the identified mutations were associated with expressed truncated WT1 protein.

The median age of tumor onset in patients with a mutation in the WT1 was lower (10 months) than in those without a mutation (39 months). Three novel heterozygous nonsense mutations were identified in exon 8 in peripheral blood from 3 individuals, whereas all 3 tumor tissues lacked the wild-type allele. All mutations led to a premature stop codon with truncation of the WT1 protein. In 1 patient, a truncated form of WT1 protein was identified, suggesting that development of the WT may have resulted from expression of an abnormal protein. Four distinct silent single-nucleotide polymorphisms (SNPs) were detected. All 3 patients with a pathogenic WT1 mutation had 2 synonymous SNPs, whereas only 1 of the remaining 5 patients had a single synonymous SNP (P < .05).

Bilateral WT are associated with early presentation in pediatric patients and a high frequency of WT1 nonsense mutations in exon 8. Silent SNPs may also be involved in the development of WT.

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    ABSTRACT: Background: Bilateral Wilms tumours (BWTs) occur by germline mutation of various predisposing genes; one of which is WT1 whose abnormality was reported in 17-38% of BWTs in Caucasians, whereas no such studies have been conducted in East-Asians. Carriers with WT1 mutations are increasing because of improved survival. Methods: Statuses of WT1 and IGF2 were examined in 45 BWTs from 31 patients with WT1 sequencing and SNP array-based genomic analyses. The penetrance rates were estimated in WT1-mutant familial Wilms tumours collected from the present and previous studies. Results: We detected WT1 abnormalities in 25 (81%) of 31 patients and two families, which were included in the penetrance rate analysis of familial Wilms tumour. Of 35 BWTs from the 25 patients, 31 had small homozygous WT1 mutations and uniparental disomy of IGF2, while 4 had large 11p13 deletions with the retention of 11p heterozygosity. The penetrance rate was 100% if children inherited small WT1 mutations from their fathers, and 67% if inherited the mutations from their mothers, or inherited or had de novo 11p13 deletions irrespective of parental origin (P=0.057). Conclusions: The high incidence of WT1 abnormalities in Japanese BWTs sharply contrasts with the lower incidence in Caucasian counterparts, and the penetrance rates should be clarified for genetic counselling of survivors with WT1 mutations.
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