Genomic imbalances pinpoint potential oncogenes and tumor suppressors in Wilms tumors.

BACKGROUND: Wilms tumor (WT) has a not completely elucidated pathogenesis. DNA copy number alterations (CNAs) are common in cancer, and often define key pathogenic events. The aim of this work was to investigate CNAs in order to disclose new candidate genes for Wilms tumorigenesis. RESULTS: Array-CGH of 50 primary WTs without pre-chemotherapy revealed a few recurrent CNAs not previously reported, such as 7q and 20q gains, and 7p loss. Genomic amplifications were exclusively detected in 3 cases of WTs that later relapsed, which also exhibited an increased frequency of gains affecting a 16.2 Mb 1q21.1-q23.2 region, losses at 11p, 11q distal, and 16q, and WT1 deletions. Conversely, aneuploidies of chromosomes 13 and 19 were found only in WTs without further relapse. The 1q21.1-q23.2 gain associated with WT relapse harbours genes such as CHD1L, CRABP2, GJA8, MEX3A and MLLT11 that were found to be over-expressed in WTs. In addition, down-regulation of genes encompassed by focal deletions highlighted new potential tumor suppressors such as CNKSR1, MAN1C1, PAQR7 (1p36), TWIST1, SOSTDC1 (7p14.1-p12.2), BBOX and FIBIN (11p13), and PLCG2 (16q). CONCLUSION: This study confirmed the presence of CNAs previously related to WT and characterized new CNAs found only in few cases. The later were found in higher frequency in relapsed cases, suggesting that they could be associated with WT progression.

Temporal blastemal cell gene expression analysis in the kidney reveals new Wnt and related signaling pathway genes to be essential for Wilms' tumor onset.

Wilms' tumors (WTs) originate from metanephric blastema cells that are unable to complete differentiation, resulting in triphasic tumors composed of epithelial, stromal and blastemal cells, with the latter harboring molecular characteristics similar to those of the earliest kidney development stages. Precise regulation of Wnt and related signaling pathways has been shown to be crucial for correct kidney differentiation. In this study, the gene expression profile of Wnt and related pathways was assessed in laser-microdissected blastemal cells in WTs and differentiated kidneys, in human and in four temporal kidney differentiation stages (i.e. E15.5, E17.5, P1.5 and P7.5) in mice, using an orthologous cDNA microarray platform. A signaling pathway-based gene signature was shared between cells of WT and of earliest kidney differentiation stages, revealing genes involved in the interruption of blastemal cell differentiation in WT. Reverse transcription-quantitative PCR showed high robustness of the microarray data demonstrating 75 and 56% agreement in the initial and independent sample sets, respectively. The protein expression of CRABP2, IGF2, GRK7, TESK1, HDGF, WNT5B, FZD2 and TIMP3 was characterized in WTs and in a panel of human fetal kidneys displaying remarkable aspects of differentiation, which was recapitulated in the tumor. Taken together, this study reveals new genes candidate for triggering WT onset and for therapeutic treatment targets.

Anthropomorphic measurements and event-free survival in patients with favorable histology Wilms tumor: a report from the Children's Oncology Group.

PURPOSE: We retrospectively examined the effect of body weight and body mass index (BMI) on event-free survival (EFS) of children with Wilms tumor treated on National Wilms Tumor Study-5 (NWTS-5). PATIENTS AND METHODS: Eligible study participants: stages I-IV favorable histology Wilms tumor with immediate nephrectomy; height and weight recorded at diagnosis, and loss of heterozygosity for chromosomes 1p and 16q assessed. RESULTS: A total of 1,532 patients were included in the analysis. The median follow-up was 4.9 years. 493 patients were less than 2 years of age and 1039 were 2 years of age or older. In both age groups there were more patients than expected with a weight or body mass index (BMI) less than the 10 per thousand or greater than the 90 per thousand. There was no relationship of weight-for-age or BMI-for-age and EFS in univariate analyses (P = 0.28, log-rank test for both comparisons). A Cox proportional hazards model, stratified by risk/treatment groups, showed that, among patients less than 2 years of age, low or high weight-for-age was not predictive of EFS (P = 0.16). Similarly, a Cox proportional hazards model, stratified by risk/treatment groups, showed that among patients greater than 2 years of age, low or high body mass index for age was not predictive of EFS (P = 0.58). CONCLUSIONS: There was no evidence that anthropomorphic data obtained at diagnosis for patients with favorable histology stages I-IV Wilms tumor was predictive for EFS in the setting of current treatment regimens. There were more patients with lower or higher weight/BMI than expected.

Complex patterns of chromosome 9 alterations including the p16INK4a locus in Wilms tumours.

BACKGROUND: Previous data implicating genetic and epigenetic events on chromosome 9, including the CDKN2A/2B locus, as molecular predictors of Wilms tumour relapse, have been conflicting. AIMS: To clarify this using genome-wide and focused molecular genetic analysis. METHODS: Microarray-based comparative genomic hybridisation (aCGH) using genome-wide coverage was applied to 76 favourable histology Wilms tumours. Additional investigation of the 9p21 locus was carried out using loss of heterozygosity (LOH) and fluorescence in situ hybridisation (FISH), as well as immunohistochemistry for CDKN2A/p16(INK4a) on a paediatric renal tumour tissue microarray. RESULTS: Approximately half of the tumours were found to show chromosome 9 copy number changes. Those cases which harboured alterations comprised at least four distinct patterns: gain of the entire chromosome, loss of 9p, gain of 9q34, or a more complex combination of gains/losses. None of these tumour groups showed any statistically significant correlation with clinicopathological variables. Deletion mapping of 9p by LOH revealed several regions of overlap, including the CDKN2A/2B locus in 4/34 (11.8%) tumours, which was confirmed to represent hemizygous deletions by FISH. CDKN2A/p16(INK4a) protein expression was predominantly negative in Wilms tumours as assessed by immunohistochemistry on a tissue array, reflecting the expression pattern in normal kidney. However, 38/236 (16.1%) non-anaplastic Wilms tumours, 4/9 (44.4%) anaplastic Wilms tumours, 5/7 (71.4%) rhabdoid tumours of the kidney, and 4/10 (40%) clear cell sarcomas of the kidney showed nuclear CDKN2A/p16(INK4a )immunoreactivity. CONCLUSIONS: These data reveal the complex nature of genetic alterations on chromosome 9 in Wilms tumours, but do not provide evidence for their involvement in or association with treatment failure.

Analysis by array CGH of genomic changes associated with the progression or relapse of Wilms' tumour.

Despite aggressive salvage regimens, approximately half of all children who suffer a Wilms' tumour recurrence will die of their disease. Although there are increasing data on molecular genetic prognostic factors present in the tumour at diagnosis, there is little information regarding the molecular events that occur with Wilms' tumour progression and relapse. In the present study, microarray-based comparative genomic hybridization (aCGH) analysis has been carried out on 58 Wilms' tumour samples, which included 38 untreated primary and 20 recurrent tumours. A higher degree of copy number changes was observed in the recurrent tumours (33.0% genomic clones) than in the primary tumour (21.2%). Paired analysis highlighted the acquisition of 15q gain with high levels of IGF1R expression in the tumour recurrence in two cases. The most statistically significant abnormality acquired between diagnosis and relapse was loss of 17p. One case that experienced 17p loss was classified as favourable histology at diagnosis, but exhibited diffuse anaplasia at recurrence and had a homozygous TP53 deletion. Another instructive case with a constitutional 11p13 deletion presented with bilateral tumours and suffered two subsequent recurrences in the left kidney. A somatic WT1 mutation was found only in the right kidney tumour, while the constitutional 11p13 deletion was the only abnormality detected in the initial left kidney tumour by aCGH. The two subsequent relapses in the left kidney contained an accumulation of additional genetic alterations, including an independent WT1 mutation.

Array CGH profiling of favourable histology Wilms tumours reveals novel gains and losses associated with relapse.

Despite the excellent survival of Wilms tumour patients treated with multimodality therapy, approximately 15% will suffer from tumour relapse, where response rates are markedly reduced. We have carried out microarray-based comparative genomic hybridisation on a series of 76 Wilms tumour samples, enriched for cases which recurred, to identify changes in DNA copy number associated with clinical outcome. Using 1Mb-spaced genome-wide BAC arrays, the most significantly different genomic changes between favourable histology tumours that did (n = 37), and did not (n = 39), subsequently relapse were gains on 1q, and novel deletions at 12q24 and 18q21. Further relapse-associated loci included losses at 1q32.1, 2q36.3-2q37.1, and gain at 13q31. 1q gains correlated strongly with loss of 1p and/or 16q. In 3 of 11 cases with concurrent 1p(-)/1q(+), a breakpoint was identified at 1p13. Multiple low-level sub-megabase gains along the length of 1q were identified using chromosome 1 tiling-path arrays. One such recurrent region at 1q22-q23.1 included candidate genes RAB25, NES, CRABP2, HDGF and NTRK1, which were screened for mRNA expression using quantitative RT-PCR. These data provide a high-resolution catalogue of genomic copy number changes in relapsing favourable histology Wilms tumours.

Treatment with nephrectomy only for small, stage I/favorable histology Wilms' tumor: a report from the National Wilms' Tumor Study Group.

PURPOSE: Children younger than 24 months with small (< 550 g), favorable histology (FH) Wilms tumors (WTs) were shown in a pilot study to have an excellent prognosis when treated with nephrectomy only. PATIENTS AND METHODS: A study of nephrectomy only for the treatment of selected children with FH WT was undertaken. Stringent stopping rules were designed to insure closure of the study if the true 2-year relapse-free survival rate was 90% or lower. RESULTS: Seventy-five previously untreated children younger than 24 months with stage I/FH WTs for which the surgical specimen weighed less than 550 g were treated with nephrectomy only. Three patients developed metachronous, contralateral WT 1.1, 1.4, and 2.3 years after nephrectomy, and eight patients relapsed 0.3 to 1.05 years after diagnosis (median, 0.4 years; mean, 0.51 years). The sites of relapse were lung (n = 5) and operative bed (n = 3). The 2-year disease-free (relapse and metachronous contralateral WT) survival rate was 86.5%. The 2-year survival rate is 100% with a median follow-up of 2.84 years. The 2-year disease-free survival rate (excluding metachronous contralateral WT) was 89.2%, and the 2-year cumulative risk of metachronous contralateral WT was 3.1%. CONCLUSION: Children younger than 24 months treated with nephrectomy only for a stage I/FH WT that weighed less than 550 g had a risk of relapse, including the development of metachronous contralateral WT, of 13.5% 2 years after diagnosis. All patients who experienced relapse on this trial are alive at this time. This approach will be re-evaluated in a clinical trial using a less conservative stopping rule.

16q loss of heterozygosity and microsatellite instability in Wilms' tumor.

BACKGROUND/PURPOSE: Wilms' tumor is the most common renal malignancy of childhood. Loss of heterozygosity (LOH) at 16q is seen in about 17% of cases and has been associated with a poor prognosis. To more precisely define the pattern of 16q deletion exhibited by Wilms' tumor, the authors performed a detailed LOH analysis of 96 specimens using polymorphic microsatellite repeat markers. The authors also evaluated the neoplasms for the presence of microsatellite instability (MSI). METHODS: A total of 96 DNA samples were studied using polymerase chain reaction-based LOH analyses amplifying polymorphic microsatellite repeat markers. Screening for MSI using 2 additional genetic markers also was carried out. RESULTS: The authors found 16q LOH in 14 of the specimens evaluated. Comprehensive analysis of these LOH-positive specimens showed a region of loss spanning 16p11.2-q22.1 and a separate distal region of LOH at 16q23.2-24.2. The distal region of deletion is very small, estimated to be approximately 2.4 megabases. In addition to the observed LOH, 2 specimens were found to consistently exhibit MSI, which has not been reported previously in Wilms' tumor. CONCLUSIONS: The smallest consensus region of deletion in our analysis of Wilms' tumor 16q LOH measures 2.4 megabases at 16q23.2-q24.2. Additionally, MSI was present in a subset of tumor specimens suggesting that defects in DNA mismatch repair may contribute to the pathogenesis of Wilms' tumor.

High telomerase reverse transcriptase (hTERT) messenger RNA level correlates with tumor recurrence in patients with favorable histology Wilms' tumor.

Telomerase is a reverse transcriptase that maintains chromosome ends, compensating for the progressive loss of DNA that occurs during replication. High telomerase enzyme activity is an unfavorable prognostic feature for several types of cancers. We investigated whether telomerase level predicts outcome for patients with the pediatric renal malignancy Wilms' tumor. In a case-cohort study of 78 patients with favorable histology Wilms' tumor, we compared tumor telomerase levels in patients with and without eventual recurrence. Three measures of telomerase were used: (a) telomerase enzyme activity; (b) expression of hTR, the RNA component of telomerase; and (c) mRNA expression of hTERT, the gene that encodes the catalytic component of the enzyme. Of the evaluable samples, 81% had detectable telomerase activity, 97% had detectable hTERT transcript, and 100% had detectable hTR. Weak correlations were observed between telomerase activity and hTR level (r = 0.34, P = 0.02) and between telomerase activity and hTERT mRNA level (r = 0.32, P = 0.04). Of the variables assessed, only hTERT mRNA expression correlated with outcome. The median hTERT mRNA level in tumors with recurrence was higher than that in tumors without recurrence (1.42 versus 0.97 units, P = 0.023, Wilcoxon). Univariate analysis of hTERT mRNA level as a continuous variable suggested that each unit increase in hTERT mRNA level increased the risk of recurrence (RR) by a factor of 1.66 [95% confidence interval (CI), 1.2-2.3; P < 0.005]. Compared with tumors with hTERT mRNA levels of 0-1 units, tumors with hTERT mRNA levels of 1-2 units had a RR of 2.72 (95% CI, 0.91-8.13; P = 0.074), and tumors with hTERT mRNA levels >2 units had a RR of 6.40 (95% CI, 1.49-27.67, P = 0.013). Multivariate analysis of hTERT mRNA level as a predictor of recurrence, adjusted for tumor stage and age at diagnosis, revealed a RR of 1.48 (95% CI, 0.9-2.6; P = 0.16). Measurement of hTERT mRNA level may, therefore, enable clinicians to identify a population of patients at high risk for recurrence and to adjust their therapy accordingly. A larger study will be necessary to determine whether hTERT expression is an independent prognostic indicator. Further biological investigation is warranted to discern whether the link between high hTERT expression and unfavorable prognosis is causative or correlative.

Frequent hypomethylation in Wilms tumors of pericentromeric DNA in chromosomes 1 and 16.

Rearrangements in the pericentromeric heterochromatin of chromosome 1 or 16 are often found in many types of cancers, including Wilms tumors, and have been suggested to contribute to oncogenesis or tumor progression. The oncogenic potential of these rearrangements has been ascribed to the resulting chromosome arm imbalances affecting the dosage of tumor suppressor genes or protooncogenes. Because DNA hypomethylation has been linked to rearrangements in the pericentromeric regions of chromosome 1 and 16 in two types of non-cancer cell populations, we examined methylation of normally highly methylated satellite DNA sequences in these regions in Wilms tumors. Hypomethylation was found to be frequent in juxtacentromeric (satellite 2) sequences and, especially, in centromeric (satellite alpha) sequences of chromosome 1. Hypomethylation of satellite 2 DNA of chromosome 16 showed a high degree of concordance with that of satellite 2 DNA of chromosome 1. We discuss the relationship of this satellite DNA hypomethylation in Wilms tumors to chromosome aberrations, as determined by assays for loss of heterozygosity.

Comparative genomic hybridization and its application to Wilms' tumorigenesis.

Eighty sporadic Wilms' tumor samples were analyzed by comparative genomic hybridization (CGH) to identify chromosomal regions involved in the etiology of the disease. Twenty percent of the samples showed chromosomal gains or losses. The majority of chromosomal gains and losses were similar to those identified through molecular and cytogenetic studies. Gains were observed on chromosomes 1q, 7q, 8, and 12, whereas losses were found on chromosomes 1p, 4p, 4q, 7p, 16q, 18q, 21q, and 22q. Other genetic aberrations identified in this study included deletions of chromosomes 5p and 15q, as well as gains of discrete loci on chromosomes 3p and 3q. These latter regions have not been previously implicated in Wilms' tumorigenesis and may contain novel genes relevant to the development and/or progression of this disease.

ETV6-NTRK3 gene fusions and trisomy 11 establish a histogenetic link between mesoblastic nephroma and congenital fibrosarcoma.

Congenital mesoblastic nephroma (CMN) is an infantile spindle cell tumor of the kidney that is subdivided into "classical" and "cellular" forms based on the degree of cellularity and mitotic activity. The histogenesis of CMN remains obscure, but relationships to other pediatric renal neoplasms have been proposed. However, cellular CMN is virtually identical histologically to congenital fibrosarcoma (CFS), a malignant tumor of fibroblasts in children of the same age group. Moreover, cytogenetic studies have reported common trisomies in CFS and cellular CMN, particularly of chromosome 11. We show here that t(12;15)(p13;q25)-associated ETV6-NTRK3 gene fusions described in CFS are also present in cellular CMN. ETV6-NTRK3 chimeric transcripts were detected in 8 of 9 cellular CMNs and 2 of 2 mixed CMNs. In contrast, all of the four classical CMNs tested were negative, as were cases of Wilms' tumor and clear cell sarcoma of the kidney. Moreover, we found trisomy 11 only in cellular or mixed CMNs with the ETV6-NTRK3 gene fusion. Our studies indicate that classical and cellular CMN have different genetic features and support the concept that cellular CMN is histogenetically related to CFS. They also provide insight into potential mechanisms involved in the transformation of the classical into the cellular form of CMN.

Comparison between single-dose and divided-dose administration of dactinomycin and doxorubicin for patients with Wilms' tumor: a report from the National Wilms' Tumor Study Group.

PURPOSE: The National Wilms' Tumor Study (NWTS)-4 was designed to evaluate the efficacy, toxicity, and cost of administration of different regimens for the treatment of Wilms' tumor (WT). PATIENTS AND METHODS: Between August 6, 1986 and September 1, 1994, 1,687 previously untreated children less than 16 years of age with stages I to II/favorable histology (FH) or stage I/anaplastic histology WT (low-risk [LR] group) or stages III to IV/FH WT or stages I to IV/clear cell sarcoma of the kidney (high-risk [HR] group) were randomized to treatment that included vincristine and either divided-dose (standard [STD]) courses (5 days) or single-dose (pulse-intensive [PI]) treatment with dactinomycin. HR patients also received either STD courses (3 days) or PI treatment with doxorubicin. RESULTS: The 2-year relapse-free survival (RFS) rates for LR patients were 91.3% for 544 randomized to treatment with PI and 91.4% for 556 randomized to treatment with STD chemotherapy (P = .988). The 2-year RFS rates for HR patients were 87.3% for 299 randomized to treatment with PI and 90.0% for 288 randomized to treatment with STD chemotherapy (P = .865). CONCLUSION: We conclude that patients treated with PI combination chemotherapy for LR or HR WT or clear cell sarcoma of the kidney have equivalent 2-year RFS to those treated with STD regimens. PI drug administration is recommended as the new standard based on demonstrated efficacy, greater administered dose-intensity, less severe hematologic toxicity, and the requirement for fewer physician and hospital encounters.

Germline WT1 mutations in Wilms' tumor patients: preliminary results.

We conducted a comparative study of the prevalence of germline WT1 mutations in patients with Wilms' tumor. Patients in Group 1 have familial Wilms' tumor, bilateral disease, associated urogenital anomalies, and/or second cancers. Those in Group 2 are unilateral, sporadic Wilms' patients without other associated conditions. Patients with aniridia or Denys-Drash syndrome are known to have WT1 alterations, and are excluded from this study. Preliminary results on 96 subjects show that the overall germline WT1 mutation frequency is low (< 5%). The work to date establishes the feasibility of identifying patients with germline WT1 mutations and, in the future, offering genetic predisposition testing to at-risk relatives. However, genetic predisposition testing of children for WT1 mutations raises many ethical, legal, and psychosocial issues; research is needed to evaluate risks and benefits.

Wilms tumor.

Wilms tumor is the most common primary malignant renal tumor of childhood, representing about six percent of all childhood cancers in the United States. Developments in surgery, radiation therapy, and chemotherapy have led to a dramatic change in the prognosis for most patients, and Wilms tumor has become a paradigm for multimodal treatment of a pediatric malignant solid tumor. The authors review the progress made in the diagnosis and management of children with Wilms tumor.

Loss of heterozygosity for chromosomes 16q and 1p in Wilms' tumors predicts an adverse outcome.

We have prospectively analyzed Wilms' tumors from 232 patients registered on the National Wilms' Tumor Study for loss of heterozygosity (LOH) on chromosomes 11p, 16q, and 1p. These chromosomal aberrations were found in 70 (33%), 35 (17%), and 21 (12%) of the informative cases, respectively. LOH for two of these regions occurred in only 25 cases, and only one tumor harbored LOH at all three sites. There was no statistically significant association between LOH at any of the three regions and either the stage or histological classification of the tumor. Patients with tumor-specific LOH for chromosome 16q had relapse rates 3.3 times higher (P = 0.01) and mortality rates 12 times higher (P < 0.01) than patients without LOH for chromosome 16q. These differences remained when adjusted for histology or for stage. Patients with LOH for chromosome 1p had relapse and mortality rates three times higher than those for patients without LOH for chromosome 1p, but these results were not statistically significant. In contrast, LOH for chromosome 11p had no effect on measures of outcome. These molecular markers may serve to further stratify Wilms' tumor patients into biologically favorable and unfavorable subgroups, allowing continued use of the clinical trial mechanism in the study of Wilms' tumor.

Relaxation of imprinted genes in human cancer.

Genomic imprinting, or parental allele-specific expression of genes, has been demonstrated at the molecular level in insects and mice but not in man. Imprinting as a potential mechanism of human disease is suggested by paternal uniparental disomy of 11p15 in Beckwith-Wiedemann syndrome and by maternal uniparental disomy of 15q11-12 in Prader-Willi syndrome. Beckwith-Wiedemann syndrome is characterized by multiorgan overgrowth and predisposition to embryonal tumours such as Wilms' tumour of the kidney. A loss of heterozygosity of 11p15 is also frequently found in a wide variety of tumours, including Wilms' tumour and lung, bladder, ovarian, liver and breast cancers; 11p15 also directly suppresses tumour growth in vitro. Two genes in this band, H19 and insulin-like growth factor-II (IGF2) undergo reciprocal imprinting in the mouse, with maternal expression of H19 (ref. 13) and paternal expression of IGF2 (ref. 14). Here we find that both of these genes show monoallelic expression in human tissues and, as in mouse, H19 is expressed from the maternal allele and IGF2 from the paternal allele. In contrast, 69% of Wilms' tumours not undergoing loss of heterozygosity at 11p showed biallelic expression of one or both genes, suggesting that relaxation or loss of imprinting could represent a new epigenetic mutational mechanism in carcinogenesis.

A third Wilms' tumor locus on chromosome 16q.

Loss of heterozygosity studies have been used to identify chromosomal regions which are frequently deleted and thus indicate areas which may harbor tumor suppressor genes. As a result, both the WT1 gene located in chromosome 11p13 and an unidentified gene(s) within chromosome 11p15 have been implicated in Wilms' tumorigenesis. Cytogenetic and linkage studies suggest that additional non-chromosome 11 sites are involved in Wilms' tumor. Because these sites may also involve loss of heterozygosity, loci on 33 autosomal arms were screened for allele loss in a series of Wilms' tumors. We found that in addition to loss on chromosome 11p (11 of 25 informative tumors) there was significant loss on chromosome 16q (9 of 45 informative tumors), while the total frequency of allele loss excluding these loci was low (9 of 426 total informative loci). These data indicate that losses of both chromosome 11p and 16q alleles are nonrandom events and suggest that 16q is the location of a third tumor suppressor gene underlying Wilms' tumorigenesis. The parental origin of the lost chromosome 16q allele was determined in eight sporadic tumors. Alleles of paternal and of maternal origin were each lost in four sporadic tumors indicating that, unlike chromosome 11p, alleles of either parental origin are lost on 16q.