Deletion of WT1 and WIT1 Genes and Loss of Heterozygosity on Chromosome 11p in Wilms Tumors in Japan

Six of 39 sporadic Wilms tumors had gross homozygous or hemizygous WT1 and WIT1 deletions. Two Wilms tumor-aniridia-genitourinary abnormalities-mental retardation syndrome patients had total hemizygous WT1 and WIT1 deletions in both constitutional and nonsporadic type tumor cells. Four of the 8 tumors with WT1 and WIT1 deletions showed loss of constitutional heterozygosity (LOH) for markers limited to the 11p13 region. Seven of 19 Wilms tumors with neither WT1 nor WIT1 deletions also had LOH on 11p; 4 in the 11p15–11p13 region, one in the 11p15 and possibly also 11p13 regions, and two solely in the 11lp15 region. Thus, 15 of the 41 Wilms tumors (37%) had WT1 and WIT1 deletions or LOH on 11p, and only 2 of the 27 tumors whose nonneoplastic normal tissues were available for study showed LOH limited to the 11p15 region. None of the 7 non-Wilms childhood renal tumors showed WT1 or WIT1 deletions, or LOH on 11p. These data suggest that Japanese Wilms tumors may be characterized by a higher incidence of the gross WT1 deletion and a lower incidence of LOH limited to the 11p15 region than the Caucasian counterparts. These moleculargenetic features may be contributing to the lower incidence of Wilms tumors in Japanese children than in Caucasian ones.     

The IGF signalling pathway in Wilms tumours - A report from the ENCCA Renal Tumours Biology-driven drug development workshop

It is hypothesised that Wilms tumour (WT) results from aberrant renal development due to its embryonic morphology, associated undifferentiated precursor lesions (termed nephrogenic rests) and embryonic kidney-like chromatin and gene expression profiles. From the study of overgrowth syndrome-associated WT, germline dysregulation was identified in the imprinted region at 11p15 affecting imprinted genes IGF2 and H19. This is also detected in ~70% sporadic cases, making this the most common somatic molecular aberration in WT. This review summarises the critical discussion at an international workshop held under the auspices of The European Network for Cancer Research in Children and Adolescents (ENCCA) consortium, where the potential for drug development to target IGF2 and the WT epigenome was debated. Here, we consider current cancer treatments which include targeting the IGF pathway and the use of methylation agents alone or in combination with other drugs in clinical trials of paediatric cancers. Finally, we discuss the possibility of the use of these drugs to treat patients with WT.     

Frequency and heritability of WT1 mutations in nonsyndromic Wilms' tumor patients: a UK Children's Cancer Study Group Study.

PURPOSE: Constitutional WT1 mutations in patients with Wilms' tumor (WT) have specifically been associated with genitourinary abnormalities, such as cryptorchidism and hypospadias. We sought to ascertain the frequency and heritability of constitutional WT1 mutations in nonsyndromic WT patients. PATIENTS AND METHODS: Constitutional DNA from 282 patients treated at seven United Kingdom Children's Cancer Study Group centers was screened for WT1 mutations using heteroduplex analysis. Bidirectional sequencing was used to confirm the mutation and to analyze the corresponding parental DNA samples. RESULTS: Five different constitutional WT1 mutations were identified in six children. Mutations in four patients were confirmed to be de novo, and all five mutations are predicted to produce truncated protein. The WT1 mutation group had a young median age at diagnosis of 13.8 months, compared with 34.9 months in the group in whom no WT1 mutations were found; four were female and two were male; and all tumors were of favorable histology. The three tumors with known histologic subtype were stromal-predominant. Contrary to expectation, four of six mutations occurred in children with unilateral tumors without any associated genitourinary abnormality. CONCLUSION: Constitutional WT1 mutations occur with a low frequency (2.1%; 95% CI, 0.8% to 4.6%) in nonsyndromic WT patients. Most mutations occurred in children with unilateral WT without associated genitourinary abnormalities, creating difficulties in identifying individuals with germline mutations on phenotype alone. Two factors that may indicate that an individual is carrying a germline WT1 mutation are an early age of onset and stromal-predominant histology of the WT.     

A high incidence of WT1 abnormality in bilateral Wilms tumours in Japan,and the penetrance rates in children with WT1 germline mutation

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.     

Upregulation of Wilms' tumour gene 1 (WT1) in uterine sarcomas

AimOverexpression of Wilms’ tumour gene (WT1) has been proven in several tumours. Previous research of our group on the cell cycle of uterine leiomyosarcoma (LMS) and carcinosarcoma (CS) suggested a possible role for WT1. We therefore intended to further explore the expression pattern of WT1 in uterine sarcomas.Methods27 CS, 38 LMS, 15 endometrial stromal sarcomas (ESS) and seven undifferentiated sarcomas (US) were collected. WT1 expression was evaluated by immunohistochemistry (IHC) in 87 samples, by RT-PCR (m-RNA expression) in 23 random selected samples and by Western blotting in 12 samples, separating cytoplasmic and nuclear proteins. A pilot study to detect mutations (exons 7–10) was performed on eight samples.ResultsIHC showed WT1 positivity in 12/27 CS, 29/38 LMS, 7/15 ESS and 4/7 US. All-but-one sample had a positive RT-PCR. All Western blottings were positive with more cytoplasmic expression in 9/12 cases. No mutations were found.ConclusionsWT1 is overexpressed in uterine sarcomas. Since increased levels of mRNA determine the biological role, WT1 might contribute to uterine sarcoma tumour biology.     

Stratification of Wilms tumor by genetic and epigenetic analysis

Somatic defects at five loci, WT1, CTNNB1, WTX, TP53 and the imprinted 11p15 region, are implicated in Wilms tumor, the commonest childhood kidney cancer. In this study we analysed all five loci in 120 Wilms tumors. We identified epigenetic 11p15 abnormalities in 69% of tumors, 37% were H19 epimutations and 32% were paternal uniparental disomy (pUPD). We identified mutations of WTX in 32%, CTNNB1 in 15%, WT1 in 12% and TP53 in 5% of tumors. We identified several significant associations: between 11p15 and WTX (P=0.007), between WT1 and CTNNB1 (P less than 0.001), between WT1 and pUPD 11p15 (P=0.01), and a strong negative association between WT1 and H19 epimutation (P less than 0.001). We next used these data to stratify Wilms tumor into three molecular Groups, based on the status at 11p15 and WT1. Group 1 tumors (63%) were defined as 11p15-mutant and WT1-normal; a third also had WTX mutations. Group 2 tumors (13%) were WT1-mutant. They either had 11p15 pUPD or were 11p15-normal. Almost all had CTNNB1 mutations but none had H19 epimutation. Group 3 tumors (25%) were defined as 11p15-normal and WT1-normal and were typically normal at all five loci (P less than 0.001). We also identified a novel clinical association between H19 epimutation and bilateral disease (P less than 0.001). These data provide new insights into the pattern, order, interactions and clinical associations of molecular events in Wilms tumor.     

Detection of submicroscopic chromosomal deletions in aniridia patients using fluorescence in-situ hybridization and a panel of cosmids covering the wt1 gene

A series of cosmids have been isolated from a human chromosome 11-specific cosmid library using the human Wilms tumour predisposition gene cDNA, WT33. Seven overlapping cosmids were isolated which cover the genomic sequence of WT1 and in situ hybridisation shows that they all localise to the p13 region of chromosome 11. Chromosomes from patients with aniridia and Wilms tumour, and a small subband deletion in 11p13, were analysed and no hybridisation signal was seen on the deletion chromosomes. These cosmids, therefore, can be used to analyse chromosomes from patients with sporadic aniridia for submicroscopic deletions. Aniridia patients who show normal hybridisation patterns on both chromosomes need no longer be screened for Wilms tumours.     

Genetic and epigenetic alterations on the short arm of chromosome 11 are involved in a majority of sporadic Wilms' tumours

Wilms' tumour is one of the most common solid tumours of childhood. 11p13 (WT1 locus) and 11p15.5 (WT2 locus) are known to have genetic or epigenetic aberrations in these tumours. In Wilms' tumours, mutation of the Wilms tumour 1 (WT1) gene at the WT1 locus has been reported, and the WT2 locus, comprising the two independent imprinted domains IGF2/H19 and KIP2/LIT1, can undergo maternal deletion or alterations associated with imprinting. Although these alterations have been identified in many studies, it is still not clear how frequently combined genetic and epigenetic alterations of these loci are involved in Wilms' tumours or how these alterations occur. To answer both questions, we performed genetic and epigenetic analyses of these loci, together with an additional gene, CTNNB1, in 35 sporadic Wilms' tumours. Loss of heterozygosity of 11p15.5 and loss of imprinting of IGF2 were the most frequent genetic (29%) and epigenetic (40%) alterations in Wilms' tumours, respectively. In total, 83% of the tumours had at least one alteration at 11p15.5 and/or 11p13. One-third of the tumours had alterations at multiple loci. Our results suggest that chromosome 11p is not only genetically but also epigenetically critical for the majority of Wilms' tumours.     

Inactivation of the remaining allele of the WT1 gene in a Wilms' tumour from a WAGR patient.

A candidate gene (WT1) has recently been described for the 11p13 tumour-suppressor gene involved in the development of Wilms' tumour. This gene encodes a zinc finger protein which can bind to a specific DNA sequence. We have found a 226 base deletion in the mRNA from a unilateral Wilms' tumour, which would cause a frameshift that completely deletes the zinc finger domain. The tumour developed in a patient suffering from the WAGR syndrome, who had a constitutional 11p13 deletion, and so the 226 base deletion represents the inactivation of the remaining WT1 allele in the tumour. This provides further direct evidence that loss of function of WT1 is an essential step in the development of Wilms' tumour.     

Characteristics and outcome of children with Beckwith-Wiedemann syndrome and Wilms' tumor: a report from the National Wilms Tumor Study Group.

PURPOSE: Children with Beckwith-Wiedemann syndrome (BWS) are at increased risk for developing Wilms' tumor (WT). We reviewed the National Wilms Tumor Study Group (NWTSG) records to assess clinical characteristics and outcome of patients with WT and BWS. METHODS: In the NWTSG, treating clinicians were asked to report, for each enrolled patient, whether the patient had BWS. Between 1980 and 1995, 4,669 patients were treated on two consecutive NWTSG protocols (NWTS 3 and NWTS 4). We retrospectively reviewed the clinical characteristics and treatment outcomes of BWS patients compared with patients with WT without BWS. RESULTS: Fifty-three children enrolled onto NWTS 3 and 4 were reported to have BWS. BWS patients were more likely to present with lower-stage tumors (P =.0001), with more than half (27 of 53) presenting with stage I disease. The overall treatment outcomes for the BWS patients were nearly identical to those without BWS, with overall survival at 4 years from diagnosis at 89% and 90%, respectively. Overall, 21% of the patients with BWS had bilateral disease, either at diagnosis (nine of 53) or as metachronous contralateral recurrence (two of 53). BWS patients enrolled onto NWTS 4 had smaller tumors than those enrolled onto NWTS 3 (P =.02), a trend not seen in the non-BWS patients. CONCLUSION: Like children without BWS, children with BWS and WT have an excellent prognosis with modern treatment regimens. There is a high risk of bilateral disease, and increasingly smaller tumors are being detected. This suggests that a national trial assessing the role of ultrasound screening followed by nephron-sparing surgery for some patients may be appropriate.     

Characteristics and outcomes of children with the Wilms tumor-Aniridia syndrome: a report from the National Wilms Tumor Study Group.

PURPOSE: Children with the rare Wilms tumor (WT)-aniridia (WAGR) syndrome have not had systematic evaluation of their clinical and pathologic features. We compared demographics, disease characteristics, and treatment outcomes in a large cohort of WT patients who did or did not have the WAGR syndrome. PATIENTS AND METHODS: Clinical and pathology records were reviewed for 8,533 patients enrolled between 1969 and 2002 by the National Wilms Tumor Study Group. RESULTS: Sixty-four patients (0.75%) had the WAGR syndrome. For WAGR and non-WAGR patients, respectively, the average birth weights (2.94 and 3.45 kg), median ages at diagnosis (22 and 39 months), and the percentages with bilateral disease (17% and 6%), metastatic disease (2% and 13%), favorable histology (FH) tumors (100% and 92%), and intralobar nephrogenic rests (ILNR; 77% and 22%) all differed. Survival estimates for WAGR and non-WAGR patients were 95% +/- 3% and 92% +/- 0.3% at 4 years but 48% +/- 17% and 86% +/- 1.0%, respectively, at 27 years from diagnosis. Five late deaths in WAGR patients were from end-stage renal disease (ESRD). CONCLUSION: The excess of bilateral disease, ILNR-associated FH tumors of mixed cell type, and early ages at diagnosis in WAGR patients all fit the known phenotypic spectrum of constitutional deletion of chromosome 11p13. Despite a favorable response of their WT to treatment, WAGR patients have a high risk of ESRD as they approach adulthood. The renal pathology associated with this apparent late manifestation of WT1 deletion, and the explanation for the abnormally low birth weights in patients with del 11p13, have yet to be determined.     

Identification and characterisation of constitutional chromosome abnormalities using arrays of bacterial artificial chromosomes

Constitutional chromosome deletions and duplications frequently predispose to the development of a wide variety of cancers. We have developed a microarray of 6000 bacterial artificial chromosomes for array-based comparative genomic hybridisation, which provides an average resolution of 750 kb across the human genome. Using these arrays, subtle gains and losses of chromosome regions can be detected in constitutional cells, following a single overnight hybridisation. In this report, we demonstrate the efficiency of this procedure in identifying constitutional deletions and duplications associated with predisposition to retinoblastoma, Wilms tumour and Beckwith-Wiedemann syndrome.     

Long-term outcome of molecular subgroups of GIST patients treated with standard-dose imatinib in the BFR14 trial of the French Sarcoma Group

BackgroundThe added value of tumoural genomic profiles to conventional clinico-biological factors to predict progression-free survival (PFS) and overall survival (OS) was prospectively investigated in patients with advanced gastrointestinal stromal tumours (GIST) treated in the BFR14 study.MethodsOf the 434 included patients, mutational analysis was performed in 322 patients. Survival analysis was performed in patients with validated mutational status.ResultsMutational status was validated in 228 patients. We identified 196 patients with tumours harbouring 200 KIT alterations (exon 11: 173 patients, exon 9: 22 patients, exon 17: 3 patients, exon 13: 2 patients; 4 patients had double KIT mutations), 6 patients with PDGFRA mutations and 26 patients with wild-type (WT) GIST genotype. On a median follow-up of 73 months, median PFS/OS were 12.3/54.9 months for WT GIST, 12.6/55 months for KIT exon 9, and 39.4 months/not reached (69.1% at 5 years) for KIT exon 11. Tumour size, female gender, KIT exon 11 mutations and CD34 positivity were independent prognostic factors for a higher PFS. A higher OS was predicted by performance status (PS) <2, low neutrophil and normal lymphocyte counts, KIT exon 11 mutations, non-advanced tumour and female gender. KIT exon 11 mutations at codons 557–558 showed better tumour response (p=0.028) but shorter PFS (p=0.0176).ConclusionsIn GIST patients, presence of a KIT exon 11 mutation is an independent prognostic factor for PFS and OS, along with gender, PS, tumour size, lymphocyte and neutrophil counts. Subsets of exon 11 mutations are associated with significantly different response patterns and PFS.     

Evidence for susceptibility genes to familial Wilms tumour in addition to WT1, FWT1 and FWT2

Three loci have been implicated in familial Wilms tumour: WT1 located on chromosome 11p13, FWT1 on 17q12-q21, and FWT2 on 19q13. Two out of 19 Wilms tumour families evaluated showed strong evidence against linkage at all three loci. Both of these families contained at least three cases of Wilms tumour indicating that they were highly likely to be due to genetic susceptibility and therefore that one or more additional familial Wilms tumour susceptibility genes remain to be found.     

Loss of heterozygosity at 7p in Wilms' tumour development

Chromosome 7p alterations have been implicated in the development of Wilms' tumour (WT) by previous studies of tumour cytogenetics, and by our analysis of a constitutional translocation (t(1;7)(q42;p15)) in a child with WT and radial aplasia. We therefore used polymorphic microsatellite markers on 7p for a loss of heterozygosity (LOH) study, and found LOH in seven out of 77 informative WTs (9%). The common region of LOH was 7p15-7p22, which contains the region disrupted by the t(1;7) breakpoint. Four WTs with 7p LOH had other genetic changes; a germline WT1 mutation with 11p LOH, LOH at 11p, LOH at 16q, and loss of imprinting of IGF2. Analysis of three tumour-associated lesions from 7p LOH cases revealed a cystic nephroma-like area also having 7p LOH. However, a nephrogenic rest and a contralateral WT from the two other cases showed no 7p LOH. No particular clinical phenotype was associated with the WTs which showed 7p LOH. The frequency and pattern of 7p LOH demonstrated in our studies indicate the presence of a tumour suppressor gene at 7p involved in the development of Wilms' tumour.     

Evaluation of nuclear unrest and p53 immunostaining in Wilms' tumor

BackgroundNuclear unrest is a term applied to Wilms’ tumors (WT) that show nuclear abnormalities close to anaplasia but without abnormal mitoses. p53 is claimed to be associated with anaplasia and poor prognosis. This study was undertaken to evaluate the clinical significance of nuclear unrest and p53 immunostaining in Wilms’ tumor.Material and methodsThis is a retrospective study of 63 patients who presented at NCI with Wilms’ tumors, and underwent preoperative chemotherapy followed by nephrectomy. Histopathologic assessment and p53 immunohistochemistry were done.ResultsWT with nuclear unrest grade III closely resembled anaplastic tumors and both of them (group 1) constituted 19% of cases. Group 1 constituted 29% of cases showing blastema dominant morphology compared to 9.4% of cases without blastema dominant morphology with significant statistical difference (p = 0.047). Almost 83% of cases that achieved 1st complete remission were stages I, II and III, while 17% were stages IV and V with significant statistical difference (p < 0.001). Stage affected the 3-year relapse-free-survival (RFS) significantly (p = 0.014) as it was more in stages I, II and III than in stages IV and V (75.4% versus 50%). Blastema dominant morphology and high risk state significantly lowered the 3-year overall survival (OS) into 54.8% in comparison to 80.9% for cases with non-blastema dominant morphology (p = 0.042). Regarding p53 immunohistochemistry, group 1 tumors showed positive p53 more than group 2 with significant statistical difference (p = 0.014). p53 Positive immunostaining was significantly associated with high risk nephroblastoma (p = 0.004).ConclusionTumor stage and blastema dominant morphology are potent prognostic factors. p53 is linked to blastema dominant morphology. WT with nuclear unrest grade III closely resembles anaplastic WT. It may be appropriate to group tumors with nuclear unrest grade III with anaplastic histology regarding treatment stratification.     

Risk factors for local recurrence in Wilms tumour and the potential influence of biopsy – The United Kingdom experience

RationaleThe UKW3 trial compared biopsy/pre-operative chemotherapy versus immediate nephrectomy and afforded the opportunity to examine the influence of percutaneous retroperitoneal biopsy and other factors on local and distant relapse of Wilms tumour (WT).MethodsPatients with unilateral WT (stages I–IV) excluding metachronous relapse or early progressive disease were eligible. Metastatic and ‘inoperable’ tumours were biopsied electively. ‘Local’ was defined as relapse within the abdomen, except for liver metastases considered as ‘distant’ relapse, together with other haematogenous routes. Uni- and multivariable analyses estimated the risk factors for relapse.ResultsOverall, 285/635 (44.9%) patients had a biopsy. With a median follow-up of 10.1 years, 35 (5.5%) patients experienced a ‘local’, 15 a combined (2.4%) and 60 (9.4%) a ‘distant’ relapse. On univariate analysis, biopsy, anaplasia and tumour size were associated with an increased risk of local relapse. On multivariable analysis, anaplasia and tumour size remained significant for local relapse whereas the elevated risk of biopsy (hazards ratio (HR) = 1.80: 95% confidence interval (CI) 0.97–3.32, p = 0.060) was marginal. Age, anaplasia, tumour size, lymph nodes metastases and stage, but not biopsy, were individually associated with increased risk of distant relapse but only age and anaplasia remained significant following multivariable analysis.ConclusionsThe UKW3 trial provides some reassurance that biopsy should not automatically lead to ‘upstaging’ of WT. Further assessment of this controversial area is required. Comparison of local relapse rates in a multinational trial in which the United Kingdom (UK) continued the practice of routinely biopsying all patients in contrast to the standard European approach will afford this opportunity and is planned.     

Gene expression analysis of blastemal component reveals genes associated with relapse mechanism in Wilms tumour

Wilms tumour (WT) is a paediatric kidney tumour, composed of blastemal, epithelial and stromal cells, with a relapse rate of approximately 15%. Long-term survival for patients with relapse remains approximately 50%. Current clinical and molecular research is directed towards identifying prognostic factors to define the minimal and intensive therapy for successful treatment of children with low and high risk of relapse, respectively. Blastemal component presents a high level of aggressiveness and responsiveness to chemotherapy. To identify molecular prognostic markers that are predictive of chemotherapy sensitivity in tumour relapse, blastemal-enriched samples from stage III and IV WT, from patients with relapse or without relapse, were analysed for 4608 human genes immobilised on a customised cDNA platform. These analyses revealed 69 differentially expressed genes, and the top nine genes were further evaluated by qRT-PCR in the initial WT samples. TSPAN3, NCOA6, CDO1, MPP2 and MCM2 were confirmed to be down-regulated in relapse WT, and TSPAN3 and NCOA6 were also validated in an independent sample group. Protein expression of MCM2 and NCOA6 were observed in 38% (13 out of 34) and 28% (9 out of 32), respectively, of independent stage III and IV WT blastema samples, without association with relapse. However, a significant association between MCM2 positive staining and chemotherapy as first treatment suggests the involvement of MCM2 with drug metabolism in WT blastemal cells.