Nephrogenic rests, nephroblastomatosis, and the pathogenesis of Wilms' tumor

Base Excision Repair Gene Polymorphisms and Wilms Tumor Susceptibility

Base excision repair (BER) is the main mechanism to repair endogenous DNA lesions caused by reactive oxygen species. BER deficiency is linked with cancer susceptibility and premature aging. Single nucleotide polymorphisms (SNPs) within BER genes have been implicated in various human malignancies. Nevertheless, a comprehensive investigation of their association with Wilms tumor susceptibility is lacking. In this study, 145 cases and 531 sex and age-matched healthy controls were recruited. We systematically genotyped 18 potentially functional SNPs in six core BER pathway genes, using a candidate SNP approach. Logistic regression was employed to evaluate odds ratio (OR) and 95% confidence interval (CI) adjusted for age and gender. Several SNPs showed protective effects against Wilms tumor. Significant associations with Wilms tumor susceptibility were shown for hOGG1 rs1052133 (dominant: adjusted OR = 0.66, 95% CI = 0.45-0.96, P = .030), FEN1 rs174538 (dominant: adjusted OR = 0.66, 95% CI = 0.45-0.95, P = .027; recessive: adjusted OR = 0.54, 95% CI = 0.32-0.93 P = .027), and FEN1 rs4246215 (dominant: adjusted OR = 0.55, 95% CI = 0.38-0.80, P = .002) polymorphisms. Stratified analysis was performed by age, gender, and clinical stage. Moreover, there was evidence of functional implication of these significant SNPs suggested by online expression quantitative trait locus (eQTL) analysis. Our findings indicate that common SNPs in BER genes modify susceptibility to Wilms tumor.

Ectopic nephrogenic rests in children: A series of 13 cases in a single institution

PURPOSE

Ectopic nephrogenic rests (ENR) are extremely rare, and their diagnosis and treatment have not yet been standardized. Our study aimed to analyze the clinical and pathological features of ENR in children and explore the optimal methods for diagnosis and treatment.

METHODS

A retrospective, single-center, case series study of 13 children with ENR was performed. Clinical manifestations, work-up, pathological features, and treatment methods were analyzed, and the postoperative status was evaluated at follow-up.

RESULTS

The study cohort included seven males and six females aged 1/4-19 months, who were divided into two subgroups: group 1 (pure ENR, cases 1-3) and group 2 (ENR associated with teratoma, cases 4-13). The patients commonly presented with a painless mass or an incidental finding in surgery. The ENR were detected in the lumbosacral and sacrococcygeal region (five cases), retroperitoneal area (five cases), testis (one case), gubernaculum testis (one case), and stomach (one case). Radiological findings showed a mixed-density mass or a mixed-signal-intensity lesion in group 2. All the patients underwent surgical resection, and all except two were event-free in a follow-up period of 2-154 months. Case 8 showed recurrence, and extended surgery was performed. Case 7 developed metastases and received chemotherapy.

CONCLUSIONS

ENR are rare among children and have no specific clinical manifestations, lab tests, and radiological features. Different treatment strategies may be adopted based on the diagnosis. Complete resection can generally be achieved, and the prognosis is excellent in most cases. However, relapse or metastasis may occur in a small subset of patients. Close follow-up is mandatory to detect recurrence and metastasis early.

MicroRNA‑199b promotes cell proliferation and invasion in Wilms' tumour by directly targeting Runt‑related transcription factor 3

Emerging evidence has demonstrated that the deregulation of microRNAs (miRNAs) contributes to Wilms' tumour (WT) malignant progression. Therefore, identifying the essential miRNAs for WT onset and progression may be a promising therapeutic method for patients with this disease. Dysregulation of miRNA‑199b (miR‑199b) serves significant roles in various types of human cancer. However, its expression patterns, possible functions and associated mechanisms in WT are largely unknown. In the present study, the expression of miR‑199b in WT tissues was detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis. The biological functions of miR‑199b overexpression in WT cells were determined using Cell counting kit‑8 and Transwell invasion assays. The mechanisms underlying the action of miR‑199b in WT cells were also investigated using bioinformatics analysis, a luciferase reporter assay, RT‑qPCR and western blot analysis. It was revealed that miR‑199b expression was upregulated in WT tissues. In addition, the downregulation of miR‑199b attenuated the proliferation and invasion of WT cells. Runt‑related transcription factor 3 (RUNX3) was mechanistically predicted as a potential target of miR‑199b. Subsequent experiments demonstrated that RUNX3 was a direct target gene of miR‑199b in WT. In addition, the downregulation of RUNX3 in the WT tissues was inversely correlated with the miR‑199b expression level. The recovered RUNX3 expression counteracted the oncogenic roles of miR‑199b in WT cells. Therefore miR‑199b may serve as an oncogene in WT progression by directly targeting RUNX3, thereby suggesting that the miR‑199b/RUNX3 axis may be a promising therapeutic target for patients with WT.

Recalling Cohnheim's Theory: Papillary Renal Cell Tumor as a Model of Tumorigenesis from Impaired Embryonal Differentiation to Malignant Tumors in Adults

We have suggested that papillary renal cell tumor (PRCT) of the kidney arises from nephrogenic rest-like lesions. To approve our hypothesis, we worked up 14 kidneys bearing papillary and 14 ones with conventional renal cell carcinoma (CRCC) histologically and found 42 papillary lesions in average per kidney bearing PRCT. PRCTs are characterized by loss of the Y chromosome and trisomy of chromosomes 7 and 17. The MET and HNF1B are localized to chromosome 7q31 and 17q21 and are frequently amplified in PRCT. We have analyzed the expression of the mutant MET in hereditary PRCTs and precursor lesions and found duplication and expression of the mutated allele. Because both genes are involved in early stage of nephron development, we have analyzed the expression of MET and HNF1B by immunohistochemistry in fetal kidneys, precursor lesions and PRCTs. We detected strong expression of MET and HNF1B in distal compartment of S-shaped body of fetal kidneys and in nephrogenic rest-like precursor lesions. Our finding suggests an association between expression of MET and HNF1B in precursor lesions and development of PRCT. We propose a model involving chromosomal clonal evolution and corresponding gene expression for development of PRCTs from embryonic rests due to impaired differentiation. Our model suggests that PRCT have a natural history distinct from that of most common CRCC.

Outcome of two patients with bilateral nephroblastomatosis/Wilms tumour treated with an add-on 13-cis retinoic acid therapy - Case report

Although the fate of nephrogenic rests varies, they are known to be precursors of Wilms tumour. Thus, nephrogenic rests require adequate treatment to prevent malignant transformation. We added 13-cis retinoic acid to the standard chemotherapy with vincristine and actinomycin-D in two patients with bilateral nephrogenic rests/nephroblastomatosis. Patient 1 also had a history of Wilms tumour. 46 (patient 1) and 81 (patient 2) months after end of treatment, both patients show stable conditions with no signs of relapse or progressive disease. Our observation supports further investigation of retinoic acid in patients with nephrogenic rests and nephroblastomatosis.

Wilms' Tumor Protein 1 and Enzymatic Oxidation of 5-Methylcytosine in Brain Tumors: Potential Perspectives

The patterns of 5-methylcytosine (5mC) and its oxidized derivatives, 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine (5caC) are reportedly altered in a range of cancers. Likewise, Wilms' Tumor protein 1 (WT1), a transcription factor essential for urogenital, epicardium, and kidney development exhibits aberrant expression in multiple tumors. Interestingly, WT1 directly interacts with TET proteins that catalyze the enzymatic oxidation of 5mC and exhibits high affinity for 5caC-containing DNA substrates in vitro. Here we review recent developments in the fields of Tet-dependent 5mC oxidation and WT1 biology and explore potential perspectives for studying the interplay between TETs and WT1 in brain tumors.

A blastema-predominant canine renal nephroblastoma with gingival metastasis: case report and literature review

Nephroblastomas are uncommon embryonal tumors in dogs. We report herein a blastema-predominant nephroblastoma with gingival metastasis in an 8-y-old Miniature Pinscher dog. Histologically, the mass was composed mainly of blastemal elements with minor epithelial and mesenchymal differentiation. Metastatic masses in the gingiva had histologic and immunohistochemical features similar to those of the primary renal nephroblastoma. Neoplastic cells were extensively positive for both vimentin and PAX8, and scattered positive for cytokeratin. Using the clinical staging of human Wilms tumor, we staged our case as stage IV with <4 mo of survival time. We summarized previous studies of canine renal and spinal nephroblastomas, and analyzed the correlations among clinical staging, histologic classification, and mean survival time of dogs with renal nephroblastomas. Clinical staging was significantly correlated with survival time, as shown in humans. In dogs, however, additional factors can potentially influence the outcome of treatment and disease development.

HMGA2 overexpression predicts relapse susceptibility of blastemal Wilms tumor patients

Wilms tumor (WT) is an embryonal malignant neoplasm of the kidney that accounts for 6-7% of all childhood cancers. WT seems to derive from multipotent embryonic renal stem cells that have failed to differentiate properly. Since mechanisms underlying WT tumorigenesis remain largely unknown, the aim of this study was to explore the expression of embryonic stem cell (ESC) markers in samples of WT patients after chemotherapy treatment SIOP protocol, as the gene expression patterns of ESC are like those of most cancer cells. We found that expression of ESC markers is heterogeneous, and depends on histological WT components. Interestingly, among ESC markers, HMGA2 was expressed significantly stronger in the blastemal component than in the stromal and the normal kidney. Moreover, two subsets of patients of WT blastemal type were identified, depending on the expression levels of HMGA2. High HMGA2 expression levels were significantly associated with a higher proliferation rate (p=0.0345) and worse patient prognosis (p=0.0289). The expression of HMGA2 was a stage-independent factor of clinical outcome in blastemal WT patients. Our multivariate analyses demonstrated the association between LIN28B-LET7A-HMGA2 expression, and the positive correlation between HMGA2 and SLUG expression (p=0.0358) in blastemal WT components. In addition, patients with a poor prognosis and high HMGA2 expression presented high levels of MDR3 (multidrug resistance transporter). Our findings suggest that HMGA2 plays a prominent role in the pathogenesis of a subset of blastemal WT, strongly associated with relapse and resistance to chemotherapy.

Nephrogenic rests in Wilms tumors treated with preoperative chemotherapy: The UK SIOP Wilms Tumor 2001 Trial experience

BACKGROUND

Nephrogenic rests (NRs) are abnormally persistent foci of embryonal cells, thought to be the precursor lesion of Wilms tumors (WTs). To date, their presence has not been systematically examined in WTs treated with preoperative chemotherapy.

METHODS

A systematic analysis of the data on NRs in WTs treated with preoperative chemotherapy obtained from the UK cohort of the International Society of Pediatric Oncology (SIOP) WT 2001 Trial. The study was based on central pathology review of full sets of slides from pathological specimens, with a median of 28 slides reviewed per case.

RESULTS

NRs were identified in 40% of unilateral WTs, including 25% perilobar nephrogenic rest (PLNR), 9% intralobar nephrogenic rest (ILNR), 5% both PLNR and ILNR, and 1% nephroblastomatosis, and in 93% of cases with bilateral lesions. ILNRs were associated with stromal histology and a younger age at diagnosis and found frequently in patients with congenital anomalies associated with WT1 mutation. PLNRs were found frequently in patients with overgrowth syndromes.

CONCLUSIONS

The prevalence of NRs in WTs after preoperative chemotherapy observed in SIOP UK WT 2001 Trial is similar to the previously published data on NRs not treated with preoperative chemotherapy. Their epidemiology supports at least two pathways to Wilms tumorigenesis.

The developmental programme for genesis of the entire kidney is recapitulated in Wilms tumour

Wilms tumour (WT) is an embryonal tumour that recapitulates kidney development. The normal kidney is formed from two distinct embryological origins: the metanephric mesenchyme (MM) and the ureteric bud (UB). It is generally accepted that WT arises from precursor cells in the MM; however whether UB-equivalent structures participate in tumorigenesis is uncertain. To address the question of the involvement of UB, we assessed 55 Wilms tumours for the molecular features of MM and UB using gene expression profiling, immunohistochemsitry and immunofluorescence. Expression profiling primarily based on the Genitourinary Molecular Anatomy Project data identified molecular signatures of the UB and collecting duct as well as those of the proximal and distal tubules in the triphasic histology group. We performed immunolabeling for fetal kidneys and WTs. We focused on a central epithelial blastema pattern which is the characteristic of triphasic histology characterized by UB-like epithelial structures surrounded by MM and MM-derived epithelial structures, evoking the induction/aggregation phase of the developing kidney. The UB-like epithelial structures and surrounding MM and epithelial structures resembling early glomerular epithelium, proximal and distal tubules showed similar expression patterns to those of the developing kidney. These observations indicate WTs can arise from a precursor cell capable of generating the entire kidney, such as the cells of the intermediate mesoderm from which both the MM and UB are derived. Moreover, this provides an explanation for the variable histological features of mesenchymal to epithelial differentiation seen in WT.

Wilms tumour in Beckwith-Wiedemann Syndrome and loss of methylation at imprinting centre 2: revisiting tumour surveillance guidelines

Beckwith-Wiedemann Syndrome (BWS) is an overgrowth syndrome caused by a variety of molecular changes on chromosome 11p15.5. Children with BWS have a significant risk of developing Wilms tumours with the degree of risk being dependent on the underlying molecular mechanism. In particular, only a relatively small number of children with loss of methylation at the centromeric imprinting centre (IC2) were reported to have developed Wilms tumour. Discontinuation of tumour surveillance for children with BWS and loss of methylation at IC2 has been proposed in several recent publications. We report here three children with BWS reported to have loss of methylation at IC2 on clinical testing who developed Wilms tumour or precursor lesions. Using multiple molecular approaches and multiple tissues, we reclassified one of these cases to paternal uniparental disomy for chromosome 11p15.5. These cases highlight the current challenges in definitively assigning tumour risk based on molecular classification in BWS. The confirmed cases of loss of methylation at IC2 also suggest that the risk of Wilms tumour in this population is not as low as previously thought. Therefore, we recommend that for now, all children with a clinical or molecular diagnosis of BWS be screened for Wilms tumour by abdominal ultrasonography until the age of eight years regardless of the molecular classification.

Induced Pluripotent Stem Cells Reduce Progression of Experimental Chronic Kidney Disease but Develop Wilms' Tumors

The therapeutic effect of induced pluripotent stem cells (iPSs) on the progression of chronic kidney disease (CKD) has not yet been demonstrated. In this study, we sought to assess whether treatment with iPSs retards progression of CKD when compared with bone marrow mesenchymal stem cells (BMSCs). Untreated 5/6 nephrectomized rats were compared with CKD animals receiving BMSCs or iPSs. Renal function, histology, immunohistochemistry, and gene expression were studied. Implanted iPSs were tracked by the SRY gene expression analysis. Both treatments minimized elevation in serum creatinine, significantly improved clearance, and slowed down progression of disease. The proteinuria was reduced only in the iPS group. Both treatments reduced glomerulosclerosis, iPSs decreased macrophage infiltration, and TGF-β was reduced in kidneys from the BMSC group. Both types of treatments increased VEGF gene expression, TGF-β was upregulated only in the iPS group, and IL-10 had low expression in both groups. The SRY gene was found in 5/8 rats treated with iPSs. These 5 animals presented tumors with histology and cells highly staining positive for PCNA and Wilms' tumor protein antibody characteristics of Wilms' tumor. These results suggest that iPSs may be efficient to retard progression of CKD but carry the risk of Wilms' tumor development.

Bilateral Wilms tumour: a review of clinical and molecular features

Wilms tumour (WT) is the most common paediatric kidney cancer and affects approximately one in 10 000 children. The tumour is associated with undifferentiated embryonic lesions called nephrogenic rests (NRs) or, when diffuse, nephroblastomatosis. WT or NRs can occur in both kidneys, termed bilateral disease, found in only 5-8% of cases. Management of bilateral WT presents a major clinical challenge in terms of maximising survival, preserving renal function and understanding underlying genetic risk. In this review, we compile clinical data from 545 published cases of bilateral WT and discuss recent progress in understanding the molecular basis of bilateral WT and its associated precursor NRs in the context of the latest radiological, surgical and epidemiological features.

miR-590 regulates WT1 during proliferation of G401 cells

Nephroblastoma (Wilms' tumor) is frequently associated with mortality in children. MicroRNAs (miRNAs) are important for tumor development serving as oncogenes or tumor suppressors. In the present study, miRNA-590 (miR-590) was identified to be upregulated in Wilms' tumor tissues compared with the normal adjacent tissues. Additionally, the levels of miR-590 were consistent with their clinical stage. Wilms' tumor 1 (WT1) was considered to be a tumor suppressor in certain tumor types, and it has been detected at low expression levels in various types of cancer with high cell proliferation and aggressive behavior. The expression levels of miR-590 were quantified using reverse transcription-quantitative polymerase chain reaction. Cell proliferation was measured using 5-ethynyl-20-deoxyuridine assays. The protein expression levels of WT1 were investigated by western blot analysis. To the best of our knowledge, the present study was the first to determine that WT1 was a target gene of miR-590 as miR-590 was able to negatively regulate WT1 expression level by binding to the specific target site within the 3′-untranslated region (3′-UTR) of WT1 in G401 cells. Additionally, overexpression of miR-590 promoted G401 cell proliferation which was consistent with the effect of small interfering RNA-WT1. Subsequently, the present study determined that the cell phenotype altered by miR-590 overexpression may be reversed by upregulation of WT1 in G401 cells. In conclusion, the observations indicated that miR-590 may function as an oncogene via targeting WT1 to induce G401 cell proliferation. These results may contribute to current understanding of the function of miR-590 in nephroblastoma.

Effects of bufalin on up-regulating methylation of Wilm's tumor 1 gene in human erythroid leukemic cells

OBJECTIVE

To explore the effects of bufalin on inhibiting proliferation, up-regulating methylation of Wilm' tumor 1 gene (WT1) as well as its possible mechanisms in human erythroid leukemic (HEL) cells.

METHODS

The HEL cells were treated with bufalin at various concentrations to observe cellular morphology, proliferation assay and cell cycle. The mRNA and protein expression levels of WT1 were detected by reverse transcription polymerase chain reaction (RT-PCR), Western blot and immunocytochemistry, DNA methylation of WT1 and protein expression levels of DNA methyltransferase 3a (DNMT3a) and DNMT3b were analyzed by methylation-specific PCR, and Western blot respectively.

RESULTS

The bufalin was effective to inhibit proliferation of HEL cells in a dose-dependent manner, their suppression rates were from 23.4%±2.1% to 87.2%±5.4% with an half maximal inhibit concentration (IC50) of 0.046 μmol/L. Typical apoptosis morphology was observed in bufalin-treated HEL cells. The proliferation index of cell cycle decreased from 76.4%±1.9% to 49.7%±1.3%. The expression levels of WT1 mRNA and its protein reduced gradually with increasing doses of bufalin, meanwhile, the methylation status of WT1 gene changed from unmethylated into partially or totally methylated. While, the expression levels of DNMT3a and DNMT3b protein gradually increased by bufalin treatment in a dose-dependent manner.

CONCLUSIONS

Bufalin can not only significantly inhibit the proliferation of HEL cells and arrest cell cycle at G0/G1 phase, but also induce cellular apoptosis and down-regulate the expression level of WT1. Our results provide the evidence of bufalin for anti-leukemia, its mechanism may involve in increasing WT1 methylation status which is related to the up-regulation of DNMT3a and DNMT3b proteins in erythroid leukemic HEL cells.

Renal myolipoosteoma: A distinctive lesion in a child

We describe a distinctive renal tumor, a myolipoosteoma (MLO), in an 11-year-old boy who presented with a 6-month history of slight right flank intermittent pain. A gross examination revealed a well-defined, 5.5 cm mass with bone-like consistency. The lesion histologically featured an admixture of mature adipose tissue, spindle cells, and bony components. No atypia, mitotic activity, or pleomorphisms were observed in the tumor. The spindle cells were smooth muscle actin (SMA) and desmin positive but HMB45 and Melan-A negative, indicating that they were of a muscular nature and differed from that of angiomyolipoma (AML). The patient had no evidence of recurrence or metastasis 56 months postoperatively. We speculate that the present tumor, which to the best of our knowledge differs from all previously described tumors, is of nephrogenic rest (NR) origin and has a favorable prognosis.

A novel morphological approach to gonads in disorders of sex development

Disorders of sex development are defined as congenital conditions with discordance between the phenotype, the genotype, the karyotype, and the hormonal profile. The disorders of sex development consensus classification established in 2005 are mainly based on chromosomal and biological data. However, histological anomalies are not considered. The aims of this study were to define the specific pathological features of gonads in various groups of disorders of sex development in order to clarify the nosology of histological findings and to evaluate the tumor risk in case of a conservative approach. One hundred and seventy-five samples from 86 patients with disorders of sex development were analyzed following a strict histological reading protocol. The term 'gonadal dysgenesis' for the histological analysis was found confusing and therefore excluded. The concept of 'dysplasia' was subsequently introduced in order to describe the architectural disorganization of the gonad (various degrees of irregular seminiferous tubules, thin albuginea, fibrous interstitium). Five histological types were identified: normal gonad, hypoplastic testis, dysplastic testis, streak gonad, and ovotestis. The analysis showed an association between undifferentiated gonadal tissue, a potential precursor of gonadoblastoma, and dysplasia. Dysplasia and undifferentiated gonadal tissue were only encountered in cases of genetic or chromosomal abnormality ('dysgenesis' groups in the disorders of sex development consensus classification). 'Dysgenetic testes', related to an embryonic malformation of the gonad, have variable histological presentations, from normal to streak. Conversely, gonads associated with hormonal deficiencies always display a normal architecture. A loss of expression of AMH and α-inhibin was identified in dysplastic areas. Foci of abnormal expression of the CD117 and OCT4 immature germ cells markers in dysplasia and undifferentiated gonadal tissue were associated with an increased risk of neoplasia. This morphological analysis aims at clarifying the histological classification and gives an indication of tumor risk of gonads in disorders of sex development.

Diagnostic utility of Wilms' tumour-1 protein (WT-1) immunostaining in paediatric renal tumours

Background & objectives:

Renal tumours constitute about 7 per cent of all neoplasms in children. It is important to differentiate Wilms’ tumour (commonest tumour) from non-Wilms’ tumours. The aim of this study was to evaluate the immunoexpression and diagnostic role of Wilms’ tumour-1 protein (WT1) in paediatric renal tumours.

Methods:

A total of 53 cases of renal tumours in children (below 18 yr) who underwent total nephrectomy were included in this retrospective study. WT1 immunostaining was done using mouse monoclonal WT1 antibody (clone: 6F-H2).

Results:

Of the 53 cases, 38 (72%) were of Wilms’ tumour. Non-Wilms’ group (15) included six cases of mesoblastic nephroma (MN), two each of clear cell sarcoma (CCSK), renal cell carcinoma (RCC) and peripheral neuroectodermal tumour (PNET) and one each of angiomyolipoma (AML), rhabdomyosarcoma (RMS) and malignant rhabdoid tumour (MRT). Proportion of WT1 positivity in Wilms’ tumour was 100 per cent in contrast to 26.7 per cent in non-Wilms’ tumours (P<0.001). Epithelial and blastemal components of Wilms’ tumour showed moderate (2+) nuclear and cytoplasmic staining in 80 (24/30) and 75 per cent (24/32) cases, respectively. MN, PNET, CCSK and AML were negative for WT1. RMS, RCC and MRT showed cytoplasmic staining, strongest in RMS. No significant association was seen between WT1 expression and NWTSG (National Wilms’ Tumor Study Group) stage.

Interpretation & conclusions:

WT1 helps to differentiate Wilms’ tumour from other paediatric renal tumours. It may help in differentiating the two subgroups of Wilms’ tumour which have distinct molecular pathogenesis and biological behaviour, however, further prospective studies are required for validation of this hypothesis.

Pathological classification of human iPSC-derived neural stem/progenitor cells towards safety assessment of transplantation therapy for CNS diseases

The risk of tumorigenicity is a hurdle for regenerative medicine using induced pluripotent stem cells (iPSCs). Although teratoma formation is readily distinguishable, the malignant transformation of iPSC derivatives has not been clearly defined due to insufficient analysis of histology and phenotype. In the present study, we evaluated the histology of neural stem/progenitor cells (NSPCs) generated from integration-free human peripheral blood mononuclear cell (PBMC)-derived iPSCs (iPSC-NSPCs) following transplantation into central nervous system (CNS) of immunodeficient mice. We found that transplanted iPSC-NSPCs produced differentiation patterns resembling those in embryonic CNS development, and that the microenvironment of the final site of migration affected their maturational stage. Genomic instability of iPSCs correlated with increased proliferation of transplants, although no carcinogenesis was evident. The histological classifications presented here may provide cues for addressing potential safety issues confronting regenerative medicine involving iPSCs.

Networks analysis of genes and microRNAs in human Wilms' tumors

Wilms' tumor (WT) is a common kidney cancer. To date, the expression of genes [transcription factors (TFs), target genes and host genes] and microRNAs (miRNAs/miRs) in WTs has captured the attention of biologists, while the regulatory association between the genes and miRNAs remains unclear. In the present study, TFs, miRNAs, target genes and host genes were considered as key factors in the construction of three levels of regulatory networks, namely, the differentially-expressed network, the related network and the global network. The four factors had three types of association, including the regulation of miRNAs by TFs, the targeting of the target genes by miRNAs and the location of miRNAs at host genes. The differentially-expressed network is the most important of the three networks, and only involves the differentially-expressed genes and miRNAs; with the exception of host genes, those elements all behave abnormally when a WT occurs, which suggests that the differentially-expressed network can accurately reveal the pathogenesis of WTs. E2F3, for example, is overexpressed in WTs, and it regulates hsa-let-7a, hsa-let-7a-1, hsa-miR-106b, among others. Meanwhile, E2F3 is targeted by hsa-miR-106b, hsa-miR-17 and hsa-miR-20a. If the regulatory network can be used to adjust those factors to a normal level, there may be a chance to cure patients with WTs. WT-associated factors were placed into the related network; this network is useful for understanding the regulatory pathways of genes and miRNA in WTs. The networks provide a novel perspective in order to study the inner interactions of genes and miRNAs. The present study provides authoritative data and regulatory pathway analysis in order to partially elucidate the pathogenesis of WT, and thus supplies biologists with a basis for future research.

Senescence Process in Primary Wilms' Tumor Cell Culture Induced by p53 Independent p21 Expression

Wilms tumor (WT) is an embryonal tumor occurring in developing kidney tissue. WT cells showing invasive cancer characteristics, also retain renal stem cell behaviours. In-vitro culture of WT is hampered by limited replicative potential. This study aimed to establish a longterm culture of WT cells to enable the study of molecular events to attempt to explain its cellular senescence. Methods: Primary cell cultures from fresh WT tumor specimen were established. Of 5 cultures tried, only 1 could be propagated for more than 7 passages. One culture, identified as PSU-SK-1, could be maintained > 35 passages and was then subjected to molecular characterization and evaluation for cancer characteristics. The cells consistently harbored concomitant mutations of CTNNB1 (Ser45Pro) and WT1 (Arg413Stop) thorough the cultivation. On Transwell invasion assays, the cells exhibited migration and invasion at 55% and 27% capability of the lung cancer cells, A549. On gelatin zymography, PSU-SK-1 showed high expression of the matrix metaloproteinase. The cells exhibited continuous proliferation with 24-hour doubling time until passages 28-30 when the growth slowed, showing increased cell size, retention of cells in G1/S proportion and positive β-galactosidase staining. As with those evidence of senescence in advanced cell passages, expression of p21 and cyclin D1 increased when the expression of β-catenin and its downstream protein, TCF, declined. There was also loss-of-expression of p53 in this cell line. In conclusion, cellular senescence was responsible for limited proliferation in the primary culture of WT, which was also associated with increased expression of p21 and was independent of p53 expression. Decreased activation of the Wnt signalling might explain the induction of p21 expression.

Imaging of Solid Kidney Tumours in Children

Eighteen children aged 6 months to 12 years with 20 solid renal tumours; 13 Wilms' tumours (WT), 2 clear cell sarcomas of the kidney, 1 malignant rhabdoid tumour of the kidney and 2 cases of bilateral nephroblastomatosis with Wilms' tumour underwent evaluation with US, CT and MR imaging. Contrast-enhanced CT and non-enhanced MR were equally accurate in determining the size and origin of the tumour but were unreliable in separation of stages I, II and III. US could only accurately assess the size of the tumours. MR characteristics varied somewhat between WTs and non-WTs but contrast-enhanced MR imaging might be useful for separation of WTs from nephroblastomatosis.

Establishment of a Conditionally Immortalized Wilms Tumor Cell Line with a Homozygous WT1 Deletion within a Heterozygous 11p13 Deletion and UPD Limited to 11p15

We describe a stromal predominant Wilms tumor with focal anaplasia and a complex, tumor specific chromosome 11 aberration: a homozygous deletion of the entire WT1 gene within a heterozygous 11p13 deletion and an additional region of uniparental disomy (UPD) limited to 11p15.5-p15.2 including the IGF2 gene. The tumor carried a heterozygous p.T41A mutation in CTNNB1. Cells established from the tumor carried the same chromosome 11 aberration, but a different, homozygous p.S45Δ CTNNB1 mutation. Uniparental disomy (UPD) 3p21.3pter lead to the homozygous CTNNB1 mutation. The tumor cell line was immortalized using the catalytic subunit of human telomerase (hTERT) in conjunction with a novel thermolabile mutant (U19dl89-97tsA58) of SV40 large T antigen (LT). This cell line is cytogenetically stable and can be grown indefinitely representing a valuable tool to study the effect of a complete lack of WT1 in tumor cells. The origin/fate of Wilms tumors with WT1 mutations is currently poorly defined. Here we studied the expression of several genes expressed in early kidney development, e.g. FOXD1, PAX3, SIX1, OSR1, OSR2 and MEIS1 and show that these are expressed at similar levels in the parental and the immortalized Wilms10 cells. In addition the limited potential for muscle/ osteogenic/ adipogenic differentiation similar to all other WT1 mutant cell lines is also observed in the Wilms10 tumor cell line and this is retained in the immortalized cells. In summary these Wilms10 cells are a valuable model system for functional studies of WT1 mutant cells.

Dermatoglyphics in kidney diseases: a review

Kidney diseases are becoming a major cause of global burden with high mortality and morbidity. The origins of most kidney diseases are known, but for some the exact aetiology is not yet understood. Dermatoglyphics is the scientific study of epidermal ridge patterns and it has been used as a non-invasive diagnostic tool to detect or predict different medical conditions that have foetal origin. However, there have been a limited number of studies that have evaluated a dermatoglyphic relationship in different kidney diseases. The aim of this review was to systematically identify, review and appraise available literature that evaluated an association of different dermatoglyphic variables with kidney diseases. This review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. The PubMed^® (Medline), POPLINE, Cochrane Library and Trip Database and grey literature sources such as OpenGrey, Google Scholar, and Google were searched to earliest date to 17 April 2014. Of the 36 relevant publications, 15 were included in the review. Of these studies, there are five case reports, seven case series and three comparative studies. Possible association of dermatoglyphics with Wilms tumor (WT) had been evaluated in two comparative studies and one case series that found fewer whorls and a lower mean total ridge count (TRC). Another study evaluated adult polycystic kidney disease (APCD) type III that revealed lower TRC means in all cases. All other case series and case reports describe dermatoglyphics in various kidney disease such as acro-renal-ocular syndrome, potter syndrome, kabuki makeup syndrome, neurofaciodigitorenal syndrome, syndactyly type V, ring chromosome 13 syndrome, trisomy 13 syndrome and sirenomelia. It is evident that whorl pattern frequency and TRC have been used widely to investigate the uncertainty related to the origin of several kidney diseases such as WT and APCD type III. However, small sample sizes, possibly methodological issues, and discrepancy in the make up between cases and control groups limits interpretation of any significant findings. Future studies with proper protocol, adequate cases, and control groups may provide stronger evidence to resolve uncertainty related to the aetiology of kidney diseases.

Wilms tumor: Successes and challenges in management outside of cooperative clinical trials

OBJECTIVE/BACKGROUND

Management of Wilms tumor (WT) in children depends on a multidisciplinary approach to treatment, and outcomes have significantly improved as reported by cooperative group clinical trials. Here, we review the clinical outcomes of patients with WT and identify challenges and barriers encountered in multidisciplinary management outside of cooperative clinical trials.

METHODS

We retrospectively reviewed the clinical records of 35 children with WT treated between April 2002 and June 2013 at the Children's Cancer Institute in Lebanon.

RESULTS

Upfront resection was performed in 23 cases. Biopsies were performed for Stage V tumors (n=4), those with unresectable tumors or inferior vena caval thrombus (n=5), and patients who had partial surgery performed elsewhere prior to presentation (n=2). One patient died due to toxicity prior to surgery. The tumor was Stage I in eight patients, Stage II in five patients, Stages III and IV in nine patients each, and bilateral (Stage V) in four patients. Adherence to The National Wilms Tumor Study-5 recommendations was adequate. At the time of analysis, 30 patients were free of disease and four patients had relapse-all having metastatic disease initially.

CONCLUSION

The National Wilms Tumor Study-5 therapy resulted in favorable outcomes in children with nonmetastatic Wilms tumor in the setting of a multidisciplinary approach to therapy and resolution of financial barriers to medical care. Upstaging due to prior intervention and lung radiation therapy to all those with computed tomography-detected lung nodules may both have resulted in overtreatment of a subset of patients. Finally, the relatively high incidence of bilateral tumors suggests the need for further genetic and molecular studies in this patient population.

WT1 Mutation in Childhood Cancer

In this chapter, the role of WT1 in childhood cancer is discussed, using the key examples Wilms' tumor, desmoplastic small round cell of childhood, and leukemia. The role of WT1 in each disease is described and mirrored to the role of WT1 in normal development.

MLLT1 YEATS domain mutations in clinically distinctive Favourable Histology Wilms tumours

Wilms tumour is an embryonal tumour of childhood that closely resembles the developing kidney. Genomic changes responsible for the development of the majority of Wilms tumours remain largely unknown. Here we identify recurrent mutations within Wilms tumours that involve the highly conserved YEATS domain of MLLT1 (ENL), a gene known to be involved in transcriptional elongation during early development. The mutant MLLT1 protein shows altered binding to acetylated histone tails. Moreover, MLLT1-mutant tumours show an increase in MYC gene expression and HOX dysregulation. Patients with MLLT1-mutant tumours present at a younger age and have a high prevalence of precursor intralobar nephrogenic rests. These data support a model whereby activating MLLT1 mutations early in renal development result in the development of Wilms tumour.

Wilms' tumour: Determinants of prognosis in an African setting

BACKGROUND

The few studies available in the literature on Wilms' tumour (WT) from sub-Saharan Africa have reported a dismal outcome for children with the tumour. This study evaluated the risk factors that have been correlated with outcome in the literature and compare these with outcome among our patients.

MATERIALS AND METHODS

Cases of histologically confirmed WT between 2009 and 2013 in a tertiary hospital in Northwestern Nigeria were evaluated for gender, age, laterality, symptoms, duration before presentation, stage at presentation, histologic subtype and p53 mutation. These were then correlated with outcome.

RESULTS

Totally, 30 cases of WT were diagnosed with mean age of 4.8 ± 1.9 years; and male:female ratio of 2:1. No statistically significant relationship with outcome was found for gender (P = 0.138) or histologic subtype (P = 0.671). The most significant variables which positively influenced the outcome were presentation at earlier stages (P = 0.007) and completion of therapy (P = 0.0007). p53 mutation was seen in 3 (16.7%) of 18 cases and was not associated with a poor outcome (P = 0.089). However, 2 of the 3 cases presented in Stage IV and none of them survived the 1 st year.

CONCLUSION

This study shows that even though p53 mutation was associated with a more aggressive phenotype, the most significant determinants of a good outcome among patients in a developing country like ours is non-blastemal dominant histologic subtype, early stage at presentation and completion of therapy.

Renal function in survivors of nonsyndromic Wilms tumor treated with unilateral radical nephrectomy

BACKGROUND

Partial nephrectomy is considered by some for children with unilateral Wilms tumor (UWT) to avoid the theoretical complication of renal insufficiency. In the current study, the authors evaluated the prevalence of hypertension and impaired renal function in long-term survivors of nonsyndromic UWT who were treated without nephrotoxic chemotherapy or ionizing radiation.

METHODS

Eligibility included age ≤15 years at the time of diagnosis of nonsyndromic UWT, treatment receipt before 2002, and maintenance of disease remission after unilateral nephrectomy without receipt of abdominal irradiation or nephrotoxic chemotherapy. Renal function was assessed by urinalysis and estimated glomerular filtration rate (eGFR). Patients receiving antihypertensive medication or those with blood pressure readings of >140/90 mm Hg were considered to be hypertensive.

RESULTS

A total of 75 patients with a median age at diagnosis of 3.2 years (range, 0.2-12.1 years) met eligibility criteria. The median length of follow-up was 19.6 years (range, 10.0-32.8 years). All but 1 patient had stage I/II disease. Sixty-eight patients (90.7%) patients had WT with favorable histology and 7 patients had anaplastic histology. Sixteen patients (21.3%) had an eGFR <90 mL/minute/1.73m(2), 2 of whom also had proteinuria (12.5%). No patient had an eGFR <60 mL/minute/1.73m(2). Five patients (6.7%) had hypertension, 3 of whom were receiving antihypertensive medications. At the time of last follow-up, no patient had developed end-stage renal disease.

CONCLUSIONS

Patients with UWT who were treated with unilateral radical nephrectomy without nephrotoxic chemotherapy or ionizing radiation appear to be at low risk of developing significant long-term renal dysfunction. For this patient population, the routine use of partial nephrectomy does not appear justified. However, monitoring and counseling are important for identifying the rare patient who develops subtle renal insufficiency and therefore might be at an increased risk of adverse cardiovascular sequelae.

The yin and yang of kidney development and Wilms' tumors

Wilms' tumor, or nephroblastoma, is the most common pediatric renal cancer. The tumors morphologically resemble embryonic kidneys with a disrupted architecture and are associated with undifferentiated metanephric precursors. Here, we discuss genetic and epigenetic findings in Wilms' tumor in the context of renal development. Many of the genes implicated in Wilms' tumorigenesis are involved in the control of nephron progenitors or the microRNA (miRNA) processing pathway. Whereas the first group of genes has been extensively studied in normal development, the second finding suggests important roles for miRNAs in general-and specific miRNAs in particular-in normal kidney development that still await further analysis. The recent identification of Wilms' tumor cancer stem cells could provide a framework to integrate these pathways and translate them into new or improved therapeutic interventions.

Recurrent DGCR8, DROSHA, and SIX homeodomain mutations in favorable histology Wilms tumors

We report the most common single-nucleotide substitution/deletion mutations in favorable histology Wilms tumors (FHWTs) to occur within SIX1/2 (7% of 534 tumors) and microRNA processing genes (miRNAPGs) DGCR8 and DROSHA (15% of 534 tumors). Comprehensive analysis of 77 FHWTs indicates that tumors with SIX1/2 and/or miRNAPG mutations show a pre-induction metanephric mesenchyme gene expression pattern and are significantly associated with both perilobar nephrogenic rests and 11p15 imprinting aberrations. Significantly decreased expression of mature Let-7a and the miR-200 family (responsible for mesenchymal-to-epithelial transition) in miRNAPG mutant tumors is associated with an undifferentiated blastemal histology. The combination of SIX and miRNAPG mutations in the same tumor is associated with evidence of RAS activation and a higher rate of relapse and death.

Comparative methylome analysis identifies new tumour subtypes and biomarkers for transformation of nephrogenic rests into Wilms tumour

BACKGROUND

Wilms tumours (WTs) are characterised by several hallmarks that suggest epimutations such as aberrant DNA methylation are involved in tumour progression: loss of imprinting at 11p15, lack of recurrent mutations and formation of nephrogenic rests (NRs), which are lesions of retained undifferentiated embryonic tissue that can give rise to WTs.

METHODS

To identify such epimutations, we performed a comprehensive methylome analysis on 20 matched trios of micro-dissected WTs, NRs and surrounding normal kidneys (NKs) using Illumina Infinium HumanMethylation450 Bead Chips and functionally validated findings using RNA sequencing.

RESULTS

Comparison of NRs with NK revealed prominent tissue biomarkers: 629 differentially methylated regions, of which 55% were hypermethylated and enriched for domains that are bivalent in embryonic stem cells and for genes expressed during development (P = 2.49 × 10(-5)). Comparison of WTs with NRs revealed two WT subgroups; group-2 WTs and NRs were epigenetically indistinguishable whereas group-1 WTs showed an increase in methylation variability, hypomethylation of renal development genes, hypermethylation and relative loss of expression of cell adhesion genes and known and potential new WT tumour suppressor genes (CASP8, H19, MIR195, RB1 and TSPAN32) and was strongly associated with bilateral disease (P = 0.032). Comparison of WTs and NRs to embryonic kidney highlighted the significance of polycomb target methylation in Wilms tumourigenesis.

CONCLUSIONS

Methylation levels vary during cancer evolution. We have described biomarkers related to WT evolution from its precursor NRs which may be useful to differentiate between these tissues for patients with bilateral disease.

CITED1 confers stemness to Wilms tumor and enhances tumorigenic responses when enriched in the nucleus

Wilms tumor (WT) is the most common childhood kidney cancer and retains gene expression profiles reminiscent of the embryonic kidney. We have shown previously that CITED1, a transcriptional regulator that labels the self-renewing, multipotent nephron progenitor population of the developing kidney, is robustly expressed across all major WT disease and patient characteristics. In this malignant context, CITED1 becomes enriched in the nucleus, which deviates from its cytosolic predominance in embryonic nephron progenitors. We designed the current studies to test the functional and mechanistic effects of differential CITED1 subcellular localization on WT behavior. To mimic its subcellular distribution observed in clinical WT specimens, CITED1 was misexpressed ectopically in the human WT cell line, WiT49, as either a wild-type (predominantly cytosolic) or a mutant, but transcriptionally active, protein (two point mutations in its nuclear export signal, CITED1ΔNES; nuclear-enriched). In vitro analyses showed that CITED1ΔNES enhanced WiT49 proliferation and colony formation in soft agar relative to wild-type CITED1 and empty vector controls. The nuclear-enriched CITED1ΔNES cell line showed the greatest tumor volumes after xenotransplantation into immunodeficient mice (n=15 animals per cell line). To elucidate CITED1 gene targets in this model, microarray profiling showed that wildtype CITED1 foremost upregulated LGR5 (stem cell marker), repressed CDH6 (early marker of epithelial commitment of nephron progenitors), and altered expression of specific WNT pathway participants. In summary, forced nuclear enrichment of CITED1 in a human WT cell line appears to enhance tumorigenicity, whereas ectopic cytosolic expression confers stem-like properties and an embryonic phenotype, analogous to the developmental context.

Biomarkers to detect Wilms tumors in pediatric patients: where are we now?

Wilms tumor (WT) is the most common pediatric renal tumor. Survival rates are high, whether treated according to the European protocols (SIOP-RTSG) that use prenephrectomy chemotherapy or the Children's Oncology Group (COG) protocols, with immediate nephrectomy. However, the more intensive treatment given to higher risk subgroups may result in late effects. Current risk stratification does not identify all tumors that relapse and loss of heterozygosity of 16q and 1p are the only molecular biomarkers used in risk stratification. In this review we describe recent new genetic and epigenetic findings in WT and discuss their potential use as biomarkers. We discuss approaches to ensure representative sampling of WTs including the potential for 'liquid biopsy' to circumvent intratumoral heterogeneity.

SIX2 Effects on Wilms Tumor Biology

Wilms tumor (WT) blastema retains gene expression profiles characteristic of the multipotent nephron progenitor pool, or cap mesenchyme (CM), in the developing kidney. As a result, WT blastema and the CM are believed to represent contextual analogues of one another. Sine oculis homeobox 2 (SIX2) is a transcription factor expressed specifically in the CM, provides a critical mechanism for CM self-renewal, and remains persistently active in WT blastema, although its purpose in this childhood malignancy remains unclear. We hypothesized that SIX2, analogous to its function in development, confers a survival pathway to blastema, the putative WT stem cell. To test its functional significance in WT biology, wild-type SIX2 was overexpressed in the human WT cell line, WiT49. After validating this model, SIX2 effects on anchorage-independent growth, proliferation, invasiveness, canonical WNT pathway signaling, and gene expression of specific WNT pathway participants were evaluated. Relative to controls, WiT49 cells overexpressing SIX2 showed significantly enhanced anchorage-independent growth and early-passage proliferation representing surrogates of cell survival. Interestingly, overexpression of SIX2 generally repressed TCF/LEF-dependent canonical WNT signaling, which activates and coordinates both differentiation and stem pathways, but significantly heightened canonical WNT signaling through the survivin promoter, a mechanism that exclusively maintains the stem state. In summary, when overexpressed in a human WT cell line, SIX2 enhances cell survival and appears to shift the balance in WNT/β-catenin signaling away from a differentiation path and toward a stem cell survival path.

A practical guide to urinary tract ultrasound in a child: Pearls and pitfalls

The aim of this review article is to equip the sonographer with the necessary knowledge to perform a detailed and clinically relevant assessment of the urinary tract in a child. Many of the techniques and principles used in the imaging of the urinary tract in adults can be applied to children. There are, however, notable differences with which the sonographer should be familiar. There is often a certain amount of trepidation when asked to image a child, but there are a number of simple steps that can make the process easier and more fulfilling. This article begins with advice on how to maintain cooperation in a child and the differences in the technical aspects of imaging of children. This is followed by a detailed review of the different pathologies that may be encountered, as well as highlighting information that is particularly relevant to the clinician looking after the child.

Extrarenal nephroblastomatosis in children: a report of two cases

BACKGROUND

Extrarenal nephroblastomatosis is a rare entity which occurs in retroperitoneum and inguinal region predominantly. Here we report two cases of primary extrarenal nephroblastomatosis of Han Chinese in Asian in unusual locations, one is located in testis and paratestis, and the other is paraspinal cord.

CASE PRESENTATION

Patient 1 was a 19-month-old boy with a hard and nodular mass adherent to the left testis in inguinal region. Patient 2 was a 9-month-old boy with a 1 × 0.7 × 0.4 cm mass in spinal canal at the midline thoracolumbar region. Histological examinations of the two patients after operations revealed extrarenall nephroblastomatosis with multiple nephrogenic foci, composed of immature glomeruli, tubules and blastemal cells.Then the patients were closely monitored without adjuvant chemotherapy, and has been alive and well without any recurrence for >6 months.

CONCLUSIONS

Most nephrogenic rests remain subclinical, and thus, complete excision of the lesion with conservative treatment is recommended. Otherwise, nephrogenic rests are close associated with Wilms tumor and regular follow-up is required to ensure early detection of malignant transformation.

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.

Perilobar nephroblastomatosis: natural history and management

Nephroblastomatosis (NB) has been considered as a precursor of Wilms tumor (WT). The natural history of NB seems to present significant variation as some lesions may regress spontaneously, while others may grow and expand or relapse and develop into WT later in childhood. Although, most investigators suggest adjutant chemotherapy, the effect and duration of treatment are not well established. Children with diffuse perilobar NB, Beckwith-Wiedemann syndrome, and hemihypertrophy seem to particularly benefit from treatment. We discuss our experience on two cases of NB and we review the literature for the management of this rare condition.

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.

Wilms tumor: an update

Wilms tumor (WT) is the most common neoplasm of the kidney in children. It is an embryologic tumor that histologically mimics renal embryogenesis and is composed of a variable mixture of stromal, blastemal, and epithelial elements. Nephrogenic rests, generally considered to be precursor lesions of the WT, are foci of the embryonic metanephric tissue that persist after the completion of renal embryogenesis. These are classified as perilobar and intralobar based on their location and maybe present as single or multiple foci. Intralobar and perilobar rests and the tumors arising from these rests differ morphologically and are characterized by 2 different sets of genetic abnormalities involving 2 adjacent foci, WT1 and WT2, on the short arm of chromosome 11. WTs arising in the intralobar rests tend to be stromal predominant and have a mutation or deletion of WT1. Germline mutation in WT1 may be associated with syndromic conditions such as WAGR and Denys-Drash syndromes. Perilobar rests and their corresponding tumors usually have loss of imprinting/loss of heterozygosity involving WT2, which contains several parentally imprinted genes. Loss of function of these genes, if present constitutionally, may be associated with Beckwith-Wiedemann syndrome or may result in isolated hypertrophy. Abnormalities in several other genes may also be seen in WT. These include WTX, (on chromosome X), CTNNB1 (chromosome 3), and TP53 (chromosome 17) among others. WT with loss of heterozygosity at 1p and 16q may have poor prognosis, requiring aggressive therapy. Treatment modalities for WT have evolved over many decades, primarily through the efforts of Dr J Bruce Beckwith at National WT study. This work is now being carried out by Children Oncology Group in North America and International Society of Pediatric Oncology in Europe. Although their therapeutic approaches are somewhat different, both have reported excellent results with equally high cure rates.

Kidney protein profiling of Wilms' tumor patients by analysis of formalin-fixed paraffin-embedded tissue samples

Wilms' tumor (nephroblastoma, WT) is the most frequent renal cancer in children. However, molecular details leading to WT have not been characterized sufficiently yet. Proteomic studies might provide new insights but are hampered by limited availability of fresh frozen tissue specimen. Therefore, we tested formalin-fixed paraffin-embedded (FFPE) tissue sections routinely collected for pathological inspection for their use in in-depth-proteomic analyses of WT samples in comparison to fresh frozen specimen. The overlap of the proteins identified was over 65%. Thus we used FFPE material from 7 patients for tandem mass spectrometry based comparison of the proteomes of WT and healthy renal tissues. We detected 262 proteins, which were differentially expressed in tumor compared to healthy renal tissue. The majority of these proteins displayed lower levels in the tumor tissue and only 30% higher levels. For selected candidates data were confirmed by immunohistochemical staining. Correlation analysis of blastemal proportions in WT and protein intensities revealed candidates for tumor stratification.

CONCLUSION

This proof of principle proteomic study of FFPE tissue sections from WT patients demonstrates that these archived tissues constitute a valuable resource for larger in-depth proteomic studies to identify markers to follow chemotherapy efficiency or for stratification of tumor subtypes.

Magnetic resonance imaging versus histopathology in Wilms tumor and nephroblastomatosis: 3 examples of noncorrelation

Magnetic resonance imaging (MRI) has become the principal tool for Wilms tumor (WT) assessment and follow-up. MRI and histopathologic findings were not congruent in 2 of the q30 scanned patients with renal masses (2008 to 2011). Three lesions thought to be WT on MRI were found to be a sclerotic nephrogenic rest (1), cystic renal dysplasia (1), and focal chronic pyelonephritis (1). The "typical" features suggesting nephroblastomatosis and WT on MRI are unreliable and such lesions require biopsy for histopathologic diagnosis, especially when nephron-sparing surgery is necessary to preserve renal function.

Wilms' tumor: biology, diagnosis and treatment

Wilms' tumor is the commonest renal tumor of childhood affecting one in 10,000 children. It is also one of the successes of paediatric oncology with long term survival above 90% for localised disease and 75% for metastatic disease. Successful management of Wilms' tumor necessitates meticulous attention to correct staging of the tumor and a collaborative effort between paediatric oncologists, specialist surgeons, radiologists, pathologists, and radiation oncologists. Although current treatment protocols are based on risk assignment to minimise toxicity for low risk patients and improve outcomes for those with high risk disease, challenges remain in identifying novel molecular, histological and clinical risk factors for stratification of treatment intensity. Knowledge about Wilms' tumor biology and treatment is evolving rapidly and remains a paradigm for multimodal malignancy treatment. Future efforts will focus on the use of biomarkers to improve risk stratification and the introduction of newer molecularly targeted therapies that will minimise toxicity and improve the outcomes for patients with unfavourable histology and recurrent disease. The aim of this article is to summarise advances in our understanding of the biology of Wilms' tumor and to describe the current approaches to clinical management of patients.