Sequential WT1 and CTNNB1 mutations and alterations of beta-catenin localisation in intralobar nephrogenic rests and associated Wilms tumours: two case studies.
BACKGROUND
Intralobar nephrogenic rests (ILNRs) are precursor lesions for Wilms tumours and are associated with WT1 gene mutations. ILNR-associated Wilms tumours have a co-clustering of WT1 and beta-catenin (CTNNB1) mutations and unique histological features characterised by a stromal-predominant histology.


OBJECTIVE
To determine the order in which WT1 and CTNNB1 mutations occur to understand the ILNR-Wilms tumour sequence.


METHODS
Of nine Wilms tumours with WT1 and CTNNB1 mutations, three ILNRs lesions in two Wilms tumours were available for analysis of WT1 and CTNNB1 mutations using microdissection. Immunohistochemistry was also performed to investigate how the mutations in beta-catenin alter the localisation in Wilms tumour development.


RESULTS
WT1 mutations were present in the ILNRs, however CTNNB1 mutations were absent. Immunohistochemistry for WT1 confirmed inactivation of WT1 in both ILNRs and Wilms tumours. Both the ILNRs and the associated Wilms tumours had similar immunostaining patterns for beta-catenin in the blastemal and epithelial components. Although rhabdomyoblasts were not included in ILNRs, the associated Wilms tumours showed rhabdomyogenic differentiation with a positive beta-catenin nuclear staining.


CONCLUSIONS
The results suggest that CTNNB1 mutation is a later event in Wilms tumourigenesis. CTNNB1 mutations might be associated with rhabdomyogenesis.
Fukuzawa
Ryuji
R
Cancer Genetics Laboratory, Department of Biochemistry, University of Otago, Dunedin, New Zealand. ryuji.fukuzawa@stonebow.otago.ac.nz
Heathcott
Rosemary W
RW
More
Helen E
HE
Reeve
Anthony E
AE
D001483:Base Sequence; D018450:Disease Progression; D006801:Humans; D007124:Immunoenzyme Techniques; D007680:Kidney Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D042282:Microdissection; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000379:methods; D011379:Prognosis; D016019:Survival Analysis; D025721:WT1 Proteins / Q000235:genetics*; D009396:Wilms Tumor / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051176:beta Catenin / Q000235:genetics* / Q000378:metabolism
C495270:CTNNB1 protein, human; D009363:Neoplasm Proteins; D025721:WT1 Proteins; D051176:beta Catenin