Hallmark discoveries in the biology of Wilms tumour

The modern study of Wilms tumour was prompted nearly 50 years ago, when Alfred Knudson proposed the 'two-hit' model of tumour development. Since then, the efforts of researchers worldwide have substantially expanded our knowledge of Wilms tumour biology, including major advances in genetics - from cloning the first Wilms tumour gene to high-throughput studies that have revealed the genetic landscape of this tumour. These discoveries improve understanding of the embryonal origin of Wilms tumour, familial occurrences and associated syndromic conditions. Many efforts have been made to find and clinically apply prognostic biomarkers to Wilms tumour, for which outcomes are generally favourable, but treatment of some affected individuals remains challenging. Challenges are also posed by the intratumoural heterogeneity of biomarkers. Furthermore, preclinical models of Wilms tumour, from cell lines to organoid cultures, have evolved. Despite these many achievements, much still remains to be discovered: further molecular understanding of relapse in Wilms tumour and of the multiple origins of bilateral Wilms tumour are two examples of areas under active investigation. International collaboration, especially when large tumour series are required to obtain robust data, will help to answer some of the remaining unresolved questions.

A Gradual Transition Toward Anaplasia in Wilms Tumor Through Tolerance to Genetic Damage

Patients with Wilms tumor (WT) in general have excellent survival, but the prognosis of patients belonging to the subgroup of WT with diffuse anaplasia (DA) is poor due to frequent resistance to chemotherapy. We hypothesized that DA WT cells might undergo changes, such as acquiring a persistent tolerance to DNA damage and copy number aberrations (CNAs), which could eventually lead to their resistance to chemotherapy treatment. Tissue sections from chemotherapy-treated DA WTs (n = 12) were compared with chemotherapy-treated nonanaplastic WTs (n = 15) in a tissue microarray system, enabling analysis of 769 tumor regions. All regions were scored for anaplastic features and immunohistochemistry was used to quantify p53 expression, proliferation index (Ki67), and DNA double-strand breaks (γH2AX). CNAs were assessed by array-based genotyping and TP53 mutations using targeted sequencing. Proliferation index and the frequency of DNA double-strand breaks (γH2AX dot expression) increased with higher anaplasia scores. Almost all (95.6%) areas with full-scale anaplasia had TP53 mutations or loss of heterozygosity, along with an increased amount of CNAs. Interestingly, areas with wild-type TP53 with loss of heterozygosity and only one feature of anaplasia (anaplasia score 1) also had significantly higher proliferation indices, more DNA double-strand breaks, and more CNAs than regions without any anaplastic features (score 0); such areas may be preanaplastic cell populations under selective pressure for TP53 mutations. In conclusion, we suggest that chemoresistance of DA WTs may be partly explained by a high proliferative capability of anaplastic cells, which also have a high burden of double-stranded DNA breaks and CNAs, and that there is a gradual emergence of anaplasia in WT.

Gene expression-based dissection of inter-histotypes, intra-histotype and intra-tumor heterogeneity in pediatric tumors

Intra-tumor heterogeneity (ITH) fosters tumor evolution, resistance to therapy, and relapse. Recently, many evidence have been accumulated on the occurrence of genetic ITH in pediatric cancers. With this study we aimed to address the downstream effects that genetic and epigenetic ITH, and tumor-microenvironment interactions may produce within a tumor mass. To this aim, we investigated by high-throughput gene expression multiple samples of 5 hepatoblastomas, 5 neuroblastomas, 5 rhabdomyosarcomas, and 5 Wilms tumors. Principal component analysis, single sample hallmark gene sets analysis, and weighted gene co-expression network analysis were performed on gene expression data. We observed that the different tumors clustered by histotype, and then by case, and in addition, a variable degree of ITH was visible in all the investigated cases. The ITH highlighted in this study can represent a challenge in tumor treatment since we demonstrated that different druggable hallmarks and targets may be heterogeneously present within the same tumor mass, and this can potentially lead to therapeutic failure. Despite this heterogeneity, we could highlight some commonalities among the different histotypes investigated, supporting the feasibility to move in the clinic from a histotype-driven to a target-driven, sometimes agnostic, approach at least in some cases.

The pathophysiology of bilateral and multifocal Wilms tumors: What we can learn from the study of predisposition syndromes

Approximately 5% of patients with Wilms tumor present with synchronous bilateral disease. The development of synchronous bilateral Wilms tumor (BWT) is highly suggestive of a genetic or epigenetic predisposition. Patients with known germline predisposition to Wilms tumor (WT1 variants, Beckwith Wiedemann spectrum, TRIM28 variants) have a higher incidence of BWT. This Children's Oncology Group (COG)-International Society for Pediatric Oncology (SIOP-) HARMONICA initiative review for pediatric renal tumors details germline genetic and epigenetic predisposition to BWT development, with an emphasis on alterations in 11p15.5 (ICR1 gain of methylation, paternal uniparental disomy, and postzygotic somatic mosaicism), WT1, TRIM28, and REST. Molecular mechanisms that result in BWT are often also present in multifocal Wilms tumor (multiple separate tumors in one or both kidneys). We identify priority areas for international collaborative research to better understand how predisposing genetic or epigenetic factors associate with response to neoadjuvant chemotherapy, oncologic outcomes, and long-term renal function outcomes.

Outcome of SIOP patients with low- or intermediate-risk Wilms tumour relapsing after initial vincristine and actinomycin-D therapy only - the SIOP 93-01 and 2001 protocols

PURPOSE

Society of International Pediatric Oncology - Renal Tumor Study Group (SIOP-RTSG) treatment recommendations for relapsed Wilms tumour (WT) are stratified by the intensity of first-line treatment. To explore the evidence for the treatment of patients relapsing after vincristine and actinomycin-D (VA) treatment for primary WT, we retrospectively evaluated rescue treatment and survival of this patient group.

PATIENTS AND METHODS

We included 109 patients with relapse after VA therapy (no radiotherapy) for stage I-II primary low- or intermediate-risk WT from the SIOP 93-01 and SIOP 2001 studies. Univariate Cox regression analysis was performed to study the effect of relapse treatment intensity on event-free survival (EFS) and overall survival (OS). Relapse treatment intensity was classified into vincristine, actinomycin-D, and either doxorubicin or epirubicin (VAD), and more intensive therapies (ifosfamide/carboplatin/etoposide [ICE]/≥ 4 drugs/high-dose chemotherapy with haematopoietic stem cell transplantation [HD HSCT]).

RESULTS

Relapse treatment regimens included either VAD, or cyclophosphamide/carboplatin/etoposide/doxorubicin (CyCED), or ICE backbones. Radiotherapy was administered in 62 patients and HD HSCT in 15 patients. Overall, 5-year EFS and OS after relapse were 72.3% (95% confidence interval [CI]: 64.0-81.6%) and 79.3% (95% CI: 71.5-88.0%), respectively. Patients treated with VAD did not fare worse when compared with patients treated with more intensive therapies (hazard ratio EFS: 0.611 [95% CI: 0.228-1.638] [p-value = 0.327] and hazard ratio OS: 0.438 [95% CI: 0.126-1.700] [p-value = 0.193]).

CONCLUSION

Patients with relapsed WT after initial VA-only treatment showed no inferior EFS and OS when treated with VAD regimens compared with more intensive rescue regimens. A subset of patients relapsing after VA may benefit from less intensive rescue treatment than ICE/CyCED-based regimens and deserve to be pinpointed by identifying additional (molecular) prognostic factors in future studies.

Analysis of the mutational status of SIX1/2 and microRNA processing genes in paired primary and relapsed Wilms tumors and association with relapse

Whereas 90% of patients with Wilms tumor (WT) reach cure, approximately half of patients developing a recurrent tumor die of the disease. Therefore, to disclose events leading to recurrence represents a clinical need. To study paired primary/recurrent tumor samples, being aware of the intra-tumoral heterogeneity, might help finding these answers. We previously suggested that mutations in SIX1 and DROSHA underlie WT recurrence. With the aim to better investigate this scenario, we collected 19 paired primary/recurrent tumors and 10 primary tumors from relapsing patients and searched for mutations in the SIX1/2 genes and microRNA processing genes (miRNAPGs). We found SIX1 mutation in one case, miRNAPGs mutations in seven cases, and the co-occurrence of SIX1 and miRNAPG mutations in one case. We could observe that, whereas in primary tumors the mutations could be heterogeneously present, in all cases they were positively selected and homogeneously present in the recurrent disease, as also indicated by a "moderate" and "almost perfect" agreement (according to the Landis and Koch classification criteria) between paired samples. Analysis of SIX1/2 genes and miRNAPGs in 50 non-relapsing WTs disclosed SIX2 mutation in one case and miRNAPGs mutations in seven. A borderline statistically significant association was observed between miRNAPGs mutations and the occurrence of relapse (p value: 0.05). These data suggest that SIX1 and miRNAPGs mutations may provide an advantage during tumor progression to recurrence and can represent oncogenic drivers in WT development.

Prognostic Factors for Wilms Tumor Recurrence: A Review of the Literature

Simple Summary

A Wilms tumor is a childhood kidney tumor. In high-income countries, 90% of patients with this tumor survive. However, the tumor recurs in 15% of patients. It is important to identify the patients at risk of recurrence in order to adjust treatment in such a way that recurrence may potentially be prevented. However, we are currently unable to determine precisely which patients are at risk of recurrence. Therefore, we present an overview of factors that influence the risk of recurrence, also known as prognostic factors. These factors range from patient-, tumor- and treatment-related characteristics to geographic and socioeconomic factors. In addition to these factors, biological markers, such as genetic alterations, should be studied more intensively as these markers may be able to better identify patients at risk of tumor recurrence.

Abstract

In high-income countries, the overall survival of children with Wilms tumors (WT) is ~90%. However, overall, 15% of patients experience tumor recurrence. The adverse prognostic factors currently used for risk stratification (advanced stage, high risk histology, and combined loss of heterozygosity at 1p and 16q in chemotherapy-naïve WTs) are present in only one third of these cases, and the significance of these factors is prone to change with advancing knowledge and improved treatment regimens. Therefore, we present a comprehensive, updated overview of the published prognostic variables for WT recurrence, ranging from patient-, tumor- and treatment-related characteristics to geographic and socioeconomic factors. Improved first-line treatment regimens based on clinicopathological characteristics and advancing knowledge on copy number variations unveil the importance of further investigating the significance of biological markers for WT recurrence in international collaborations.

Unmet needs for relapsed or refractory Wilms tumour: Mapping the molecular features, exploring organoids and designing early phase trials - A collaborative SIOP-RTSG, COG and ITCC session at the first SIOPE meeting

Wilms tumour (WT) accounts for about 6% of all childhood cancers and overall survival of WT is about 90% in international protocols. However, for WT subgroups with much poorer prognoses, i.e. typically high-risk (unfavorable) histology and/or relapse, there is an unmet need to better understand the biology of WT and to translate biological findings into clinics through early phase clinical trials that evaluate innovative therapies. The main challenges are the small numbers of children suitable for early phase trials, the genetic heterogeneity of WT and the low number of somatic mutations that are currently considered 'druggable'. Accordingly, a joint meeting between clinical and biology experts from the international cooperative groups of the Renal Tumour Study Group of the International Society of Paediatric Oncology, the Renal Tumour Committee of the Children's Oncology Group and the European Innovative Therapies for Children with Cancer consortium and parents representatives was organised during the first SIOPE meeting in Prague, 2019. We reviewed WT molecular features, ongoing/planned early phase trials and explored available knowledge on organoid technology. The key messages were: (1) relapsed WT should undergo whenever possible thorough molecular characterization and be enrolled in protocols or trials with systematic data collecting and reporting; (2) WT displays few known 'actionable' targets and currently no novel agent has appeared promising; (3) we need to improve the enrolment rate of WT candidates in early phase trials especially for the relatively small subgroup of relapses with an adverse prognostic signature; (4) despite some agnostic early phase trials existing, development of WT-focused trials are warranted; (5) growing organoids with parallel testing of drug panels seems feasible and may direct individual treatment and encourage clinical researchers to incorporate the most promising agents into early phase trials.

Publisher Correction: The UMBRELLA SIOP-RTSG 2016 Wilms tumour pathology and molecular biology protocol

In the version of this article initially published online it was not open access, this has now been corrected.

The UMBRELLA SIOP-RTSG 2016 Wilms tumour pathology and molecular biology protocol

On the basis of the results of previous national and international trials and studies, the Renal Tumour Study Group of the International Society of Paediatric Oncology (SIOP-RTSG) has developed a new study protocol for paediatric renal tumours: the UMBRELLA SIOP-RTSG 2016 protocol (the UMBRELLA protocol). Currently, the overall outcomes of patients with Wilms tumour are excellent, but subgroups with poor prognosis and increased relapse rates still exist. The identification of these subgroups is of utmost importance to improve treatment stratification, which might lead to reduction of the direct and late effects of chemotherapy. The UMBRELLA protocol aims to validate new prognostic factors, such as blastemal tumour volume and molecular markers, to further improve outcome. To achieve this aim, large, international, high-quality databases are needed, which dictate optimization and international harmonization of specimen handling and comprehensive sampling of biological material, refine definitions and improve logistics for expert review. To promote broad implementation of the UMBRELLA protocol, the updated SIOP-RTSG pathology and molecular biology protocol for Wilms tumours has been outlined, which is a consensus from the SIOP-RTSG pathology panel.

Genetic and epigenetic analyses guided by high resolution whole-genome SNP array reveals a possible role of CHEK2 in Wilms tumour susceptibility

Wilms tumour (WT), the most frequent malignant childhood renal tumour, shows a high degree of genetic and epigenetic heterogeneity. Loss of imprinting on chromosome 11p15 is found in a large fraction of cases and mutations in a few genes, including WT1, CTNNB1, WTX, TP53 and, more recently, SIX1, SIX2 and micro RNA processing genes (miRNAPGs), have been observed. However, these alterations are not sufficient to describe the entire spectrum of genetic defects underlying WT development. We inspected data obtained from a previously performed genome-wide single nucleotide polymorphism (SNP) array analysis on 96 WT samples. By selecting focal regions commonly involved in chromosomal anomalies, we identified genes with a possible role in WT development, based on the prior knowledge of their biological relevance, including MYCN, DIS3L2, MIR562, HACE1, GLI3, CDKN2A and CDKN2B, PALB2, and CHEK2. The MYCN hotspot mutation c.131C>T was detected in seven cases (7.3%). Full sequencing of the remaining genes disclosed 16 rare missense variants and a splicing mutation. Most of these were present at the germline level. Promoter analysis of HACE1, CDKN2A and CDKN2B disclosed partial methylation affecting HACE1 in a consistent fraction of cases (85%). Interestingly, of the four missense variants identified in CHEK2, three were predicted to be deleterious by in silico analyses, while an additional variant was observed to alter mRNA splicing, generating a functionally defective protein. Our study adds additional information on putative WT genes, and adds evidences involving CHEK2 in WT susceptibility.

Immunomodulation in a Treatment Program Including Pre- and Post-Operative Interleukin-2 and Chemotherapy for Childhood Osteosarcoma

Aims and Background

The treatment applied in our Institution to children with localized osteosarcoma between 1991 and 1999 consisted of four interleukin 2 (IL-2) courses (9 x 106 IU/mL/daily x 4), alternated with pre- and post-operative polichemotherapy. The aims of the present study were to quantify the modifications of some immunological parameters induced by IL-2 and to verify whether polychemotherapy could reduce them. An additional aim was to assess whether any correlation between the immune modifications and the clinical outcome could be found.

Patients and Methods

We evaluated in 18 consecutive patients the following changes, induced in blood by each IL-2 course: number of lymphocyte subpopulations and natural killer (NK) cells, lymphokine activated killer (LAK) and NK activities.

Results

Chemotherapy did not influence the modifications of the number of NK and CD4+ cells and of the LAK and NK activities, induced by each of the four courses of IL-2. The magnitudo of the NK activity and the peak of the NK absolute counts significantly correlated with the clinical outcome.

Conclusions

The results show that the use of IL-2 permitted a repeated immune activation despite the intensive chemotherapy. Furthermore, although the limited number of cases precludes any definitive conclusion, the results suggest a possible role of the NK cells in the control of osteosarcoma.

Retrospective Analysis of Ploidy in Primary Osseous and Extraosseous Ewing Family Tumors in Children

Aims

To restrospectively study the DNA content in a series of childhood Ewing Family Tumors (EFT), and to investigate its prognostic value.

Methods

The study was performed on a series of 27 EFTs (osseous Ewing's sarcoma, 18 cases; extraos-sous Ewing's sarcoma, 2; peripheral neuroepithelioma, 4; Askin Rosai tumors, 3). Ploidy was investigated using both flow cytometry (FCM) and image cytometry (ICM) on tumor cell suspensions from formalin-fixed paraffin-embedded specimens or fresh frozen tissue obtained from the primary tumor at diagnosis.

Results

Ploidy was evaluable by FCM in all cases, and by ICM in 23/27. When fresh frozen tissue and paraffin-embedded samples from the same tumor were available for analysis, they yielded equal results. The rate of agreement between FCM and ICM was 82%. The majority of cases were diploid, and in the present series aneuploidy seemed to be associated with a poor outcome.

Conclusions

These results suggest that aneuploidy could be an indicator of a bad prognosis in EFT; however, the small number of cases precludes any conclusion of statistical value. Larger restrospective studies on ploidy using archival material could be performed and their reliability is supported by the concordance of results from fresh and formalin-fixed tissue.

Factors possibly affecting prognosis in children with Wilms' tumor diagnosed before 24 months of age: A report from the Associazione Italiana Ematologia Oncologia Pediatrica (AIEOP) Wilms Tumor Working Group

BACKGROUND

Children with Wilms' tumor (WT) aged under 24 months (infants) have a better prognosis than older patients. Our aim was to study the epidemiology of this age group, with focus on the modality of diagnosis, tumor size, and association with malformations/syndromes, seeking to understand if any of these factors might be related to prognosis.

PATIENTS AND METHODS

Infants diagnosed with WT between 2003 and February 2010 were evaluated. A query form was used to collect data on the modality of WT diagnosis (symptomatic or incidental), tumor volume, maximum diameter, site, and stage.

RESULTS

Data were collected for 117 of 124 WT infants registered. Twenty-four cases had an incidental diagnosis (ID) of renal mass, usually arising from an abdominal ultrasound performed for other reasons, and 93 had been diagnosed based on clinical signs/symptoms. The incidental cohort displayed unifocal disease, mean tumor diameter 5.52 cm, mean tumor volume 84.30 ml, and 14 patients showed associated malformations. Symptomatic patients had mean maximum tumor diameter of 10.18 cm, mean tumor volume of 451.18 ml, and six had associated malformations.

CONCLUSIONS

Our study showed that 20% of the infants had an ID of WT; they had a relatively smaller nonmetastatic tumor and a higher rate of malformations than infants of the symptomatically diagnosed group, but we did not detect any difference in age at diagnosis between the two groups. Conversely, we found a significant difference in the 5-year event-free survival rate (P = 0.018) between infants under 1 year (96%), more frequently associated with congenital malformations, and infants 1-2 years (80%).

Chromosomal anomalies at 1q, 3, 16q, and mutations of SIX1 and DROSHA genes underlie Wilms tumor recurrences

Approximately half of children suffering from recurrent Wilms tumor (WT) develop resistance to salvage therapies. Hence the importance to disclose events driving tumor progression/recurrence. Future therapeutic trials, conducted in the setting of relapsing patients, will need to prioritize targets present in the recurrent lesions. Different studies identified primary tumor-specific signatures associated with poor prognosis. However, given the difficulty in recruiting specimens from recurrent WTs, little work has been done to compare the molecular profile of paired primary/recurrent diseases. We studied the genomic profile of a cohort of eight pairs of primary/recurrent WTs through whole-genome SNP arrays, and investigated known WT-associated genes, including SIX1, SIX2 and micro RNA processor genes, whose mutations have been recently proposed as associated with worse outcome. Through this approach, we sought to uncover anomalies characterizing tumor recurrence, either acquired de novo or already present in the primary disease, and to investigate whether they overlapped with known molecular prognostic signatures.

Among the aberrations that we disclosed as potentially acquired de novo in recurrences, some had been already recognized in primary tumors as associated with a higher risk of relapse. These included allelic imbalances of chromosome 1q and of chromosome 3, and CN losses on chromosome 16q. In addition, we found that SIX1 and DROSHA mutations can be heterogeneous events (both spatially and temporally) within primary tumors, and that their co-occurrence might be positively selected in the progression to recurrent disease. Overall, these results provide new insights into genomic and genetic events underlying WT progression/recurrence.

Whole transcriptome sequencing identifies BCOR internal tandem duplication as a common feature of clear cell sarcoma of the kidney

Purpose

Clear cell sarcoma of the kidney (CCSK) is a rare pediatric renal tumor that is frequently difficult to distinguish among other childhood renal tumors due to its histological heterogeneity. This work evaluates genetic abnormalities carried by a series of CCSK samples by whole transcriptome sequencing (WTS), to identify molecular biomarkers that could improve the diagnostic process.

Methods

WTS was performed on tumor RNA from 8 patients with CCSK. Bioinformatic analysis, with implementation of a pipeline for detection of intragenic rearrangements, was executed. Sanger sequencing and gene expression were evaluated to validate BCOR internal tandem duplication (ITD).

Results

WTS did not identify any shared SNVs, Ins/Del or fusion event. Conversely, analysis of intragenic rearrangements enabled the detection of a breakpoint within BCOR transcript recurrent in all samples. Three different in-frame ITD in exon15 of BCOR, were detected. The presence of the ITD was confirmed on tumor DNA and cDNA, and resulted in overexpression of BCOR.

Conclusion

WTS coupled with specific bioinformatic analysis is able to detect rare genetic events, as intragenic rearrangements. ITD in the last exon of BCOR is recurrent in all CCSK samples analyzed, representing a valuable molecular marker to improve diagnosis of this rare childhood renal tumor.

Retina-derived POU domain factor 1 coordinates expression of genes relevant to renal and neuronal development

Retina-derived POU domain Factor 1 (RPF-1), a member of POU transcription factor family, is encoded by POU6F2 gene, addressed by interstitial deletions at chromosome 7p14 in Wilms tumor (WT). Its expression has been detected in developing kidney and nervous system, suggesting an early role for this gene in regulating development of these organs. To investigate into its functions and determine its role in transcriptional regulation, we generated an inducible stable transfectant from HEK293 cells. RPF-1 showed nuclear localization, elevated stability, and transactivation of promoters featuring POU consensus sites, and led to reduced cell proliferation and in vivo tumor growth. By addressing the whole transcriptome regulated by its induction, we could detect a gross alteration of gene expression that is consistent with promoter occupancy predicted by genome-wide Chip-chip analysis. Comparison of bound regulatory regions with differentially expressed genes allowed identification of 217 candidate targets. Enrichment of divergent octamers in predicted regulatory regions revealed promiscuous binding to bipartite POUS and POUH consensus half-sites with intervening spacers. Gel-shift competition assay confirmed the specificity of RPF-1 binding to consensus motifs, and demonstrated that the Ser-rich region upstream of the POU domain is indispensable to achieve DNA-binding. Promoter-reporter activity addressing a few target genes indicated a dependence by RPF-1 on transcriptional response. In agreement with its expression in developing kidney and nervous system, the induced transcriptome appears to indicate a function for this protein in early renal differentiation and neuronal cell fate, providing a resource for understanding its role in the processes thereby regulated.

The clinical phenotype of YWHAE-NUTM2B/E positive pediatric clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) although uncommon, is the second most frequent renal malignancy of childhood. Until now, the sole recurrent genetic aberration identified in CCSKs is t(10;17)(q22;p13), which gives rise to a fusion transcript of YWHAE and NUTM2B/E. So far, the clinical relevance of this fusion transcript is unknown. The aim of this descriptive study was to determine the clinical phenotype of t(10;17)(q22;p13) positive CCSKs. Snap-frozen tissues, formalin-fixed paraffin-embedded tissues or RNA previously extracted from CCSK samples throughout European, North-American and Japanese study groups were screened by RT-PCR for the YWHAE-NUTM2B/E transcript. Clinical characteristics, tumor characteristics, and outcome of patients with and without the fusion transcript were studied. The cohort comprised 51 previously published cases to which were added 139 internationally collected CCSK samples. RNA from 57 of these additionally collected cases was of sufficient quality to be successfully screened for the YWHAE-NUTM2B/E transcript. In total, seven of the 108 cases harbored the fusion transcript. Patients with tumors containing the fusion transcript were relatively young (median age 10 months), had associated low median tumor volumes and stage I disease was not observed in these patients. Two of seven patients relapsed and one of seven patients died of disease. Ranges of values were not overtly different between patients with and without the fusion transcript; however, the number of fusion transcript positive cases turned out to be too small to permit reliable statistical analysis. The current study did not identify an explicit clinical phenotype of CCSK cases harboring the YWHAE-NUTM2B/E fusion transcript.

Constitutional de novo deletion of the FBXW7 gene in a patient with focal segmental glomerulosclerosis and multiple primitive tumors

Multiple primary malignant neoplasms are rare entities in the clinical setting, but represent an important issue in the clinical management of patients since they could be expression of a genetic predisposition to malignancy. A high resolution genome wide array CGH led us to identify the first case of a de novo constitutional deletion confined to the FBXW7 gene, a well known tumor suppressor, in a patient with a syndromic phenotype characterized by focal segmental glomerulosclerosis and multiple primary early/atypical onset tumors, including Hodgkin's lymphoma, Wilms tumor and breast cancer. Other genetic defects may be associated with patient's phenotype. In this light, constitutional mutations at BRCA1, BRCA2, TP53, PALB2 and WT1 genes were excluded by performing sequencing and MLPA analysis; similarly, we ruled out constitutional abnormalities at the imprinted 11p15 region by methylation specific -MLPA assay. Our observations sustain the role of FBXW7 as cancer predisposition gene and expand the spectrum of its possible associated diseases.

Abstract 3268: Gene expression associated to relapsing disease in Wilms tumor indicates a more differentiated phenotype unveiling a distinct transformation process for patients with a higher risk of relapse

Wilms Tumor (WT), originating through perturbation of developmental processes in embryonic kidney, is the most frequent pediatric genitourinary malignancy. Despite its overall survival rate has reached 90%, several patients develop relapses and, among them, approximately 50% will suffer of fatal disease. Hence, reduction of the relapse burden is key to improve WT outcome, and incorporation of novel prognostic markers is currently explored to achieve this goal. Chromosomal alterations and gene expression signatures in WT cohorts are thus examined to identify patients with risk disease.

By evaluating gene expression profiles of 58 untreated primary tumor tissues from patients enrolled in the AIEOP multicenter protocol, we could identify four WT subtypes displaying enrichment for genes that were differentially expressed, and divergent clinical outcome. These patterns were validated against a previously published large WT cohort, confirming the accuracy of the prediction. A correlation analysis based on the expression of WT1, which deregulation is a crucial event in this disease, allowed us to verify known WT1 targets and to identify novel potential effectors implicated in this disease. However, although the majority or primary tumors from relapsing patients (7 out of 11) features lower WT1 level and increased 11p13 copy number (CN) losses, its expression did not significantly correlate with specific pathological parameters, confirming its poor prognostic impact as an independent disease predictor.

Therefore, in order to reliably associate the risk of recurrence to a specific gene signature, we performed class comparison analysis of primary tumors between relapsing and non-relapsing patients. Unexpectedly, the pattern of genes up-regulated in relapsing tumors showed a negative enrichment of genes expressed in early embryonic kidney structures, such as the metanephric and cap mesenchyme, and a positive enrichment for genes expressed in nephrogenic structures developed upon mesenchymal-to-epithelial transition. These findings underscore the clinical heterogeneity of the disease and indicate that disruption of post-inductive renal processes occurs in high-risk WTs. Moreover, a few transcripts mapping at chromosome 1q21-44, with CN gain or allelic imbalance in 5/11 relapsing vs. 6/47 non-relapsing tumors, were found up-regulated in these patients. Remarkably, a few genes known to be implicated in metastatic disease in adult cancers, including SPP1, MUC1, MYC, CLDN1, and MAOA, showed up-regulation in relapsing WTs. Overall, our data suggests a gene signature associated to naive primary recidivant tumors, to be exploited as a potential predictor of disease at higher risk of relapse.

Citation Format: Antonio Fiorino, Loris De Cecco, Beatrice Gamba, Edoardo Marchesi, Paola Collini, Andrea Pession, Marilina Nantron, Maurizio Bianchi, Filippo Spreafico, Silvana Canevari, Paolo Radice, Daniela Perotti. Gene expression associated to relapsing disease in Wilms tumor indicates a more differentiated phenotype unveiling a distinct transformation process for patients with a higher risk of relapse. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3268. doi:10.1158/1538-7445.AM2015-3268

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.

Osteopathia striata with cranial sclerosis, Wilms’ tumor and the WTX gene

Osteopathia striata with cranial sclerosis (OSCS, OMIM#300373) is an X-linked dominant sclerosing bone dysplasia that shows a distinct phenotype in females and males. In 2009, Zandra Jenkins et al found that germline mutations in the FAM123B/WTX/AMER1 gene, mapped to chromosome Xq11.2, cause both the familial and sporadic forms of OSCS. Intriguingly, the WTX gene was already known as a putative tumor suppressor gene, since in 2007 Rivera et al had reported inactivating WTX mutations in Wilms’ tumor (WT), the most frequent renal tumor of childhood. Here we review the heterogeneous clinical presentation of OSCS patients and the involvement of WTX anomalies in OSCS and in WT.

Is Wilms tumor a candidate neoplasia for treatment with WNT/β-catenin pathway modulators?--A report from the renal tumors biology-driven drug development workshop

The European Network for Cancer Research in Children and Adolescents consortium organized a workshop in Rome, in June 2012, on "Biology-Driven Drug Development Renal Tumors Workshop" to discuss the current knowledge in pediatric renal cancers and to recommend directions for further research. Wilms tumor is the most common renal tumor of childhood and represents a success of pediatric oncology, with cure rates of more than 85% of cases. However, a substantial minority (∼25%) responds poorly to current therapies and requires "high-risk" treatment or relapse. Moreover, the successfully treated majority are vulnerable to the late effects of treatment, with nearly one quarter reporting severe chronic health conditions by 25 years of follow-up. Main purposes of this meeting were to advance our understanding on the molecular drivers in Wilms tumor, their heterogeneity and interdependencies; to provide updates on the clinical-pathologic associations with biomarkers; to identify eligible populations for targeted drugs; and to model opportunities to use preclinical model systems and prioritize targeted agents for early phase clinical trials. At least three different pathways are involved in Wilms tumor; this review represents the outcome of the workshop discussion on the WNT/β-catenin pathway in Wilms tumorigenesis.

Quantitative DNA methylation analysis improves epigenotype-phenotype correlations in Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is a rare disorder characterized by overgrowth and predisposition to embryonal tumors. BWS is caused by various epigenetic and/or genetic alterations that dysregulate the imprinted genes on chromosome region 11p15.5. Molecular analysis is required to reinforce the clinical diagnosis of BWS and to identify BWS patients with cancer susceptibility. This is particularly crucial prenatally because most signs of BWS cannot be recognized in utero. We established a reliable molecular assay by pyrosequencing to quantitatively evaluate the methylation profiles of ICR1 and ICR2. We explored epigenotype-phenotype correlations in 19 patients that fulfilled the clinical diagnostic criteria for BWS, 22 patients with suspected BWS, and three fetuses with omphalocele. Abnormal methylation was observed in one prenatal case and 19 postnatal cases, including seven suspected BWS. Seven cases showed ICR1 hypermethylation, five cases showed ICR2 hypomethylation, and eight cases showed abnormal methylation of ICR1 and ICR2 indicating paternal uniparental disomy (UPD). More cases of ICR1 alterations and UPD were found than expected. This is likely due to the sensitivity of this approach, which can detect slight deviations in methylation from normal levels. There was a significant correlation (p < 0.001) between the percentage of ICR1 methylation and BWS features: severe hypermethylation (range: 75–86%) was associated with macroglossia, macrosomia, and visceromegaly, whereas mild hypermethylation (range: 55–59%) was associated with umbilical hernia and diastasis recti. Evaluation of ICR1 and ICR2 methylation by pyrosequencing in BWS can improve epigenotype-phenotype correlations, detection of methylation alterations in suspected cases, and identification of UPD.

Loss of heterozygosity analysis at different chromosome regions in Wilms tumor confirms 1p allelic loss as a marker of worse prognosis: a study from the Italian Association of Pediatric Hematology and Oncology

PURPOSE

The specific aims of the AIEOP-TW-2003 protocol included prospectively investigating a possible association of tumor loss of heterozygosity with outcomes in children treated for Wilms tumor.

MATERIALS AND METHODS

We analyzed 125 unilateral favorable histology Wilms tumors registered between 2003 and 2008 in the Italian cooperative protocol for microsatellite markers mapped to chromosomes 1p, 7p, 11q, 16q and 22q.

RESULTS

The 3-year disease-free survival and overall survival probabilities were 0.87 (95% CI 0.81-0.93) and 0.98 (95% CI 0.96-1.0), respectively. Loss of heterozygosity at 1p was significantly associated with a worse disease-free survival (probability 0.67 for patients with and 0.92 for those without 1p loss of heterozygosity, p = 0.0009), as confirmed also by multivariate analysis adjusting for tumor stage and patient age at diagnosis. There was no difference in disease-free survival probability among children with loss of heterozygosity in the other chromosomal regions tested. The worse outlook for children older than 2 years at diagnosis did not seem to be influenced by the loss of heterozygosity patterns considered.

CONCLUSIONS

Chromosome 1p loss of heterozygosity seems to be a risk factor for nonanaplastic Wilms tumor, possibly regardless of other clinical factors. Our findings were uninformative regarding loss of heterozygosity in the other chromosomal regions tested.

WTX R353X mutation in a family with osteopathia striata and cranial sclerosis (OS-CS): case report and literature review of the disease clinical, genetic and radiological features

Osteopathia striata with cranial sclerosis (OS-CS) or Horan-Beighton syndrome is a rare X-linked dominant inherited bone dysplasia, characterized by longitudinal striations of long bones and cranial sclerosis. Patients can be asymptomatic or present with typical facial dysmorphism, sensory defects, internal organs anomalies, growth and mental retardation, depending on the severity of the disease. WTX gene (Xq11) has been recently identified as the disease causing gene. Aim of this article is to present the case of a 6 year old girl initially evaluated for bilateral hearing loss. Patient's head CT scan pointed out sclerosis of skull base and mastoid cells, and abnormal middle-ear ossification. Clinical examination of the patient and her mother were suspicious for OS-CS. The diagnosis was confirmed by X-rays examination showing typical longitudinal striation. Genetic analysis allowed the identification of maternally transmitted heterozygous nonsense c.1057C>T (p.R353X) WTX gene mutation. We also provide a systematic review of currently available knowledge about clinical, radiologic and genetic features typical of the OS-CS.

Abstract 1423: Transcription induced by the POU6F2-encoded RPF-1 and genome-wide screening of promoter occupancy unveil a potential regulatory role in kidney embryogenesis

Wilms Tumor (WT, or nephroblastoma), a tumor of embryonic origin, is the most frequent genitourinary tumor in childhood. Current view of this malignancy point out to a common origin with the fetal developing kidney. Undifferentiated mesenchymal cell types and differentiated immature structures are in fact present in WTs, whose gene expression tend to overlap with the early nephrogenesis transcriptome. Remarkably, several factors guiding the development of kidney are overexpressed in WT specimens. WT is also characterized by alterations at several genomic loci and 20% patients exhibit LOH at chr7p. We were able to identify the smallest overlapping region at 7p14 encoding the POU6F2 gene, of the POU family of transcription factors regulating developmental and biological processes. Moreover, expression of POU6F2 mouse homolog was shown during nephrogenesis. These finding may be indicative of a role for this gene in kidney development, and since perturbation of this process contribute to WT, we addressed whether the Retina-derived POU domain Factor-1 (RPF-1, product of POU6F2) is a bonafide transcription factor participating in the transcriptional program that drive nephrogenesis. By addressing RPF-1 protein-DNA interaction we could confirm functional interaction with consensus octamers for POU proteins. Following its induction in human embryo kidney (HEK293) stable transfectants, the pattern of transcriptional targets regulated was evaluated and about 750 genes showed significant modulation (p&lt;0.01) by its expression. Further, genome-wide localization of RPF-1 bound promoter regions via ChIP-chip enabled identification of loci in approximately 1,700 genes. Overlapping with the transcriptome showed a set of 367 genes directly modulated through its expression. Motif analysis at their loci indicated the presence of degenerate POU octameric sequences in &gt;80% genes, suggesting for RPF-1 a low specificity in its binding to DNA. Top biological processes emerging from functional annotation analysis of direct transcriptional targets included kidney, metanephron, tube and ureteric bud development, primary germ layer formation, cell fate commitment, and neurogenesis as well. Axonal guidance, ephrin signalling, and transcription were top canonical functions clustered by gene ontology. Accordingly, regulators of nephrogenesis, such as EYA1, PDGFD, SLIT2 and ROBO2, myogenic differentiator MEF2C, neurite regulator MAP2, and GATA2 stem cell differentiator, are all regulated through promoter featuring closely spaced octamers. Overall, our results suggest a direct implication of RPF-1 into the transcriptional program guiding kidney development, and perturbation of its function during embryogenesis may contribute to the development of nephroblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1423. doi:1538-7445.AM2012-1423

Genomic profiling by whole-genome single nucleotide polymorphism arrays in Wilms tumor and association with relapse

Despite the excellent survival rate of Wilms tumor (WT) patients, only approximately one-half of children who suffer tumor recurrence reach second durable remission. This underlines the need for novel markers to optimize initial treatment. We investigated 77 tumors using Illumina 370CNV-QUAD genotyping BeadChip arrays and compared their genomic profiles to detect copy number (CN) abnormalities and allelic ratio anomalies associated with the following clinicopathological variables: relapse (yes vs. no), age at diagnosis (≤ 24 months vs. >24 months), and disease stage (low stage, I and II, vs. high stage, III and IV). We found that CN gains at chromosome region 1q21.1-q31.3 were significantly associated with relapse. Additional genetic events, including allelic imbalances at chromosome arms 1p, 1q, 3p, 3q, and 14q were also found to occur at higher frequency in relapsing tumors. Interestingly, allelic imbalances at 1p and 14q also showed a borderline association with higher tumor stages. No genetic events were found to be associated with age at diagnosis. This is the first genome wide analysis with single nucleotide polymorphism (SNP) arrays specifically investigating the role of genetic anomalies in predicting WT relapse on cases prospectively enrolled in the same clinical trial. Our study, besides confirming the role of 1q gains, identified a number of additional candidate genetic markers, warranting further molecular investigations.

Clinical and molecular description of a Wilms tumor in a patient with tuberous sclerosis complex

We report on a girl affected with tuberous sclerosis, carrying a germline de novo TSC2 mutation, c.4934-4935delTT, leading to a p.F1645CfsX7, who developed a unilateral Wilms tumor (WT). Molecular investigation of the tumor biopsy at diagnosis revealed the loss of the constitutional wild-type TSC2 allele, and loss of heterozygosity for the WT1 gene. Deletion of the WTX gene was also present, but it involved the functionally inactive X chromosome. No mutation affecting the remaining WT1 and WTX alleles, as well as the CTNNB1 gene was found. Pathological examination of the surgical specimen documented the presence of diffuse anaplasia and p53 immunoreactivity. To the best of our knowledge, this is the second report of a patient with tuberous sclerosis who developed a WT, and it represents the first case in which a detailed clinical and molecular description is provided.

Severe polyuria and polydipsia in hyponatremic-hypertensive syndrome associated with Wilms tumor

The combination of hyponatremia and renovascular hypertension is known as hyponatremic-hypertensive syndrome (HHS) and so rarely described in children but associated with various kinds of occlusions of the renal artery. We describe two children who presented HHS with severe hypokalemia, polyuria, and polydipsia associated with Wilms tumor, which required treatment with an angiotensin-converting enzyme inhibitor before nephrectomy. All HHS signs and symptoms resolved only following surgical resection of the tumor, allowing chemotherapy to be given.

A novel WT1 mutation in a 46,XY boy with congenital bilateral cryptorchidism, nystagmus and Wilms tumor

The WT1 gene plays a crucial role in urogenital and gonadal development. Germline WT1 alterations have been described in a wide spectrum of pathological conditions, including kidney diseases, genital abnormalities and Wilms tumor (WT), frequently occurring in combination. We report on a novel WT1 nonsense mutation (c.1105C>T), introducing a premature stop codon in exon 8 (p.Q369X), in a young XY male patient who presented with bilateral cryptorchidism, nystagmus, mild proteinuria and WT, but no sign of severe nephropathy. Although the majority of congenital urogenital abnormalities are not due to constitutional defects of the WT1 gene, our findings provide a rational for considering WT1 mutational analysis as one of the screening options in newborns with congenital defects of the urogenital tract due to the associated high risk of WT.

Molecular evidence of the independent origin of multiple Wilms tumors in a case of WAGR syndrome

BACKGROUND

This study investigated the genetic events leading to tumorigenesis in a patient affected with WAGR syndrome who developed multiple distinct Wilms tumors (WTs).

PROCEDURE AND RESULTS

At 1 year of age, the child developed two synchronous bilateral WTs that were resected by partial nephrectomy. Histologically, these tumors were fetal rhabdomyomatous nephroblastomas. Immunohistochemical study revealed the absence of nuclear expression of WT1 protein, while beta-catenin protein was expressed at nuclear level by the large majority of tumor cells. Molecular investigations of WT1 gene and exon 3 of beta-catenin (CTNNB1) gene detected no mutations. At 4 years of age, 28 months after the chemotherapy completion, a third WT was diagnosed in the left kidney, and surgically removed before any further chemotherapy. Nine months after surgery, a metastasis was detected in the left lung. Both the third renal tumor and the lung metastasis showed a blastema-predominant morphology. Immunohistochemistry confirmed the lack of expression of WT1 protein, while beta-catenin protein was expressed at nuclear level by the large majority of tumor cells. Molecular analysis of the third renal tumor and the lung metastasis revealed a 4 bp deletion in exon 7 of WT1 gene, leading to a frameshift of the reading frame and to a premature stop of the translation (c.925_928delACTC, p.T309LfsX71); no mutations in the exon 3 of the beta-catenin gene were documented.

CONCLUSIONS

These data demonstrate that multiple WTs can arise as a consequence of different genetic events in a patient with genetic predisposition, such as WAGR syndrome.

Treatment of high-risk relapsed Wilms tumor with dose-intensive chemotherapy, marrow-ablative chemotherapy, and autologous hematopoietic stem cell support: experience by the Italian Association of Pediatric Hematology and Oncology

BACKGROUND

We evaluated an intensified chemotherapy strategy in children with Wilms tumor who relapsed with high-risk features.

PROCEDURES

From January 2001 to June 2006, we treated 20 consecutive children with reinduction chemotherapy (using ifosfamide/carboplatin/etoposide in 15/20 cases), with (n = 15) or without (n = 5) subsequent high-dose chemotherapy and hematopoietic stem cell support, surgery where feasible, and radiation therapy. The median time to relapse was 10 months after nephrectomy. All but two children initially received doxorubicin as first-line therapy.

RESULTS

All patients were assessed for outcome: 13 are currently alive, 12 of them in remission a median 25 months since their relapse, one with progressing tumor. The treatment was unsuccessful in eight children: the disease progressed during reinduction in three, and relapsed in five. There was one toxic death. All transplanted patients engrafted to a neutrophil count >0.5 x 10(3)/microl after a median 11 days, and to an unsustained platelet count >25,000/microl after a median of 13 days. Three-year disease-free and overall survival rates were 56 +/- 12% and 55 +/- 13%, respectively. Neither recurrence within 12 months of nephrectomy nor extra-lung recurrence negatively affected outcome. A survival advantage was demonstrated in patients without disease evidence prior to transplant.

CONCLUSION

A disease-free survival rate nearing 50% is a realistic target in children with high-risk recurrent Wilms tumor. The benefit of autologous hematopoietic stem cell transplantation for consolidation deserves to be investigated in a randomized, controlled study.

Functional inactivation of the WTX gene is not a frequent event in Wilms' tumors

For many years the precise genetic etiology of the majority of Wilms' tumors has remained unexplained. Recently, the WTX gene, mapped to chromosome Xq11.1, has been reported to be lost or mutated in approximately one-third of Wilms' tumors. Moreover, in female cases, the somatically inactivated alleles were found to invariantly derive from the active chromosome X. Consequently, WTX has been proposed as a 'one-hit' tumor suppressor gene. To provide further insights on the contribution of WTX to the development of the disease, we have examined 102 Wilms' tumors, obtained from 43 male and 57 female patients. Quantitative PCR analyses detected WTX deletions in 5 of 45 (11%) tumors from males, whereas loss of heterozygosity at WTX-linked microsatellites was observed in 9 tumors from 50 informative females (19%). However, in the latter group, using a combination of HUMARA assay and bisulfite-modified DNA sequencing, we found that the deletion affected the active chromosome X only in two cases (4%). Sequence analyses detected an inactivating somatic mutation of WTX in a single tumor, in which a strongly reduced expression of the mutant allele respect to the wild-type allele was observed, a finding not consistent with its localization on the active chromosome X. Overall, a functional somatic nullizygosity of the WTX gene was ascertained only in seven of the Wilms' tumors included in the study (approximately 7%). Our findings indicate that previously reported estimates on the proportion of Wilms' tumors due to WTX alterations should be reconsidered.

Distinct methylation changes at the IGF2-H19 locus in congenital growth disorders and cancer

Background

Differentially methylated regions (DMRs) are associated with many imprinted genes. In mice methylation at a DMR upstream of the H19 gene known as the Imprint Control region (IC1) is acquired in the male germline and influences the methylation status of DMRs 100 kb away in the adjacent Insulin-like growth factor 2 (Igf2) gene through long-range interactions. In humans, germline-derived or post-zygotically acquired imprinting defects at IC1 are associated with aberrant activation or repression of IGF2, resulting in the congenital growth disorders Beckwith-Wiedemann (BWS) and Silver-Russell (SRS) syndromes, respectively. In Wilms tumour and colorectal cancer, biallelic expression of IGF2 has been observed in association with loss of methylation at a DMR in IGF2. This DMR, known as DMR0, has been shown to be methylated on the silent maternal IGF2 allele presumably with a role in repression. The effect of IGF2 DMR0 methylation changes in the aetiology of BWS or SRS is unknown.

Methodology/Principal Findings

We analysed the methylation status of the DMR0 in BWS, SRS and Wilms tumour patients by conventional bisulphite sequencing and pyrosequencing. We show here that, contrary to previous reports, the IGF2 DMR0 is actually methylated on the active paternal allele in peripheral blood and kidney. This is similar to the IC1 methylation status and is inconsistent with the proposed silencing function of the maternal IGF2 allele. Beckwith-Wiedemann and Silver-Russell patients with IC1 methylation defects have similar methylation defects at the IGF2 DMR0, consistent with IC1 regulating methylation at IGF2 in cis. In Wilms tumour, however, methylation profiles of IC1 and IGF2 DMR0 are indicative of methylation changes occurring on both parental alleles rather than in cis.

Conclusions/Significance

These results support a model in which DMR0 and IC1 have opposite susceptibilities to global hyper and hypomethylation during tumorigenesis independent of the parent of origin imprint. In contrast, during embryogenesis DMR0 is methylated or demethylated according to the germline methylation imprint at the IC1, indicating different mechanisms of imprinting loss in neoplastic and non-neoplastic cells.

Different mechanisms cause imprinting defects at the IGF2/H19 locus in Beckwith-Wiedemann syndrome and Wilms' tumour

The parent of origin-dependent expression of the IGF2 and H19 genes is controlled by the imprinting centre 1 (IC1) consisting in a methylation-sensitive chromatin insulator. Deletions removing part of IC1 have been found in patients affected by the overgrowth- and tumour-associated Beckwith-Wiedemann syndrome (BWS). These mutations result in the hypermethylation of the remaining IC1 region, loss of IGF2/H19 imprinting and fully penetrant BWS phenotype when maternally transmitted. We now report that 12 additional cases with IC1 hypermethylation have a similar clinical phenotype but showed neither a detectable deletion nor other mutation in the local vicinity. Likewise, no IC1 deletion was detected in 40 sporadic non-syndromic Wilms' tumours. A detailed analysis of the BWS patients showed that the hypermethylation variably affected the IC1 region and was generally mosaic. We observed that all these cases were sporadic and in at least two families affected and unaffected members shared the same maternal IC1 allele but not the abnormal maternal chromosome epigenotype. Furthermore, the chromosome with the imprinting defect derived from either the maternal grandfather or maternal grandmother. Overall, these results indicate that methylation-imprinting defects at the IGF2-H19 locus can result from inherited mutations of the IC and have high recurrence risk or arise independently from the sequence context and generally not transmitted to the progeny. Despite these differences, the epigenetic abnormalities are usually present in the patients in the mosaic form and probably acquired by post-zygotic de novo methylation. Distinguishing between these two groups of cases is important for genetic counselling.

[Cesarean section, techniques and skin suture materials]

AIM

The aim of the study was to compare the outcome, complications and costs of three skin suture techniques after Caesarean section.

METHODS

The study sample was 310 women who underwent caesarean section between 2003 and 2007. The sample was divided into three groups: an intradermal suture with non-reabsorbable thread was applied in 98; metallic clips were placed in 90; 2-octyl-cyanoacrylate (2-OCA) glue was used for wound closure in 112. The sutures were checked at 4 days and 2 months after the operation to determine cosmetic outcome, patient compliance, strength of incision closure, allergic reactions, suture infection, and total cost of each technique.

RESULTS

No substantial differences in strength of incision closure or cosmetic outcome between the techniques were found. Compliance was better in the group that received 2-OCA, while the total cost of suture alone was lower in the group that received the non-reabsorbable intradermal suture.

CONCLUSION

The results suggests that following Caesarean section according to Stark, skin suture with 2-OCA glue has the advantage of greater patient compliance, while intradermal thread suture is less costly with a cosmetic outcome comparable to that of the other two techniques.

The murine Pou6f2 gene is temporally and spatially regulated during kidney embryogenesis and its human homolog is overexpressed in a subset of Wilms tumors

We have previously suggested the transcription factor gene POU6F2 as a novel tumor suppressor involved in Wilms tumor (WT) predisposition. Since WT arises from pluripotent embryonic renal precursors, in this study we analyzed the expression of the murine homolog Pou6f2 during kidney embryogenesis and compared it to that of Wt1, the homolog of WT1, a known WT related gene involved in mesenchyme to epithelium conversion. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) performed for Pou6f2 on kidney specimens from embryos, pups, and adult mice, showed that the Pou6f2 mRNA was more abundant in the earliest analyzed phase of kidney organogenesis (E13) than in more advanced fetal stages and in adult animal. In situ RT-PCR demonstrated that Pou6f2 expression parallels the centripetal differentiation of renal morphogenesis. In addition, in E18 kidney, most structures exhibiting Pou6f2 expression stained positively in immunohistochemistry for the Wt1 protein. Finally, quantitative real-time RT-PCR revealed an overexpression (>/=80 times) of POU6F2 compared with normal kidney in 5 of 22 (23%) WTs. The finding of a highly regulated temporal and spatial Pou6f2 expression during renal organogenesis, of its coexpression with Wt1 and of POU6F2 overexpression in a subset of WTs are consistent with a role of POU6F2 in kidney development and provide further support to its involvement in WT.