WT1, WTX and CTNNB1 mutation analysis in 43 patients with sporadic Wilms' tumor

Wilms' tumor (WT) is a heterogeneous neoplasia characterized by a number of genetic abnormalities, involving tumor suppressor genes, oncogenes and genes related to the Wnt signaling pathway. Somatic biallelic inactivation of WT1 is observed in 5-10% of sporadic WT. Somatic mutations in exon 3 of CTNNB1, which encodes β-catenin, were initially observed in 15% of WT. WTX encodes a protein that negatively regulates the Wnt/β-catenin signaling pathway and mediates the binding of WT1. In this study, we screened germline and somatic mutations in selected regions of WT1, WTX and CTNNB1 in 43 WT patients. Mutation analysis of WT1 identified two single-nucleotide polymorphisms, one recurrent nonsense mutation (p.R458X) in a patient with proteinuria but without genitourinary findings of Denys-Drash syndrome (DDS) and one novel missense mutation, p.C428Y, in a patient with Denys-Drash syndrome phenotype. WT1 SNP rs16754A>G (R369R) was observed in 17/43 patients, and was not associated with significant difference in age at diagnosis distribution, or with 60-month overall survival rate. WTX mutation analysis identified five sequence variations, two synonymous substitutions (p.Q1019Q and p.D379D), a non-synonymous mutation (p.F159L), one frameshift mutation (p.157X) and a novel missense mutation, p.R560W. Two sequence variations in CTNNB1 were identified, p.T41A and p.S45C. Overall survival of bilateral cases was significantly lower (p=0.005). No difference was observed when survival was analyzed among patients with WT1 or with WTX mutations. On the other hand, the survival of two patients with the CTNNB1 p.T41A mutation was significantly lower (p=0.000517) than the average.