Clear cell sarcoma of the kidney demonstrates an embryonic signature indicative of a primitive nephrogenic origin

Molecular Signature of Biological Aggressiveness in Clear Cell Sarcoma of the Kidney (CCSK)

Clear cell sarcoma of the kidney (CCSK) is a rare pediatric renal tumor with a worse prognosis than Wilms' tumor. Although recently, BCOR internal tandem duplication (ITD) has been found as a driver mutation in more than 80% of cases, a deep molecular characterization of this tumor is still lacking, as well as its correlation with the clinical course. The aim of this study was to investigate the differential molecular signature between metastatic and localized BCOR-ITD-positive CCSK at diagnosis. Whole-exome sequencing (WES) and whole-transcriptome sequencing (WTS) were performed on six localized and three metastatic BCOR-ITD-positive CCSKs, confirming that this tumor carries a low mutational burden. No significant recurrences of somatic or germline mutations other than BCOR-ITD were identified among the evaluated samples. Supervised analysis of gene expression data showed enrichment of hundreds of genes, with a significant overrepresentation of the MAPK signaling pathway in metastatic cases (p < 0.0001). Within the molecular signature of metastatic CCSK, five genes were highly and significantly over-expressed: FGF3, VEGFA, SPP1, ADM, and JUND. The role of FGF3 in the acquisition of a more aggressive phenotype was investigated in a cell model system obtained by introducing the ITD into the last exon of BCOR by Crispr/Cas9 gene editing of the HEK-293 cell line. Treatment with FGF3 of BCOR-ITD HEK-293 cell line induced a significant increase in cell migration versus both untreated and scramble cell clone. The identification of over-expressed genes in metastatic CCSKs, with a particular focus on FGF3, could offer new prognostic and therapeutic targets in more aggressive cases.

Role of Cyclin D1 and BCOR Immunohistochemistry in Differentiating Clear Cell Sarcoma of Kidney From its Mimics

BACKGROUND AND AIM

Clear cell sarcoma of kidney (CCSK) is the second most common pediatric renal malignancy, constituting ∼3% of renal tumors. Due to its morphologic diversity, the diagnosis of CCSK is often challenging. Recent studies have identified internal tandem duplication of BCL6 corepressor (BCOR) gene in CCSKs which coupled with cyclin D1 immunoreactivity, is helpful in differentiating it from its mimics, particularly blastema-rich Wilms tumor (WT), malignant rhabdoid tumor (MRT), and congenital mesoblastic nephroma (CMN). We aimed to evaluate the utility of cyclin D1 and BCOR immunohistochemistry in differentiating CCSK from its morphologic mimics.

MATERIALS AND METHODS

Our cohort comprised of 38 pediatric renal tumors which included CCSK (n=18), WT (n=10), MRT (n=5), and CMN (n=5) cases. A detailed clinicopathologic analysis was performed, and tissue microarray were constructed for CCSK and WT, while MRT and CMN tumors were individually stained.

RESULTS

The age ranged from 2 months to 16 years with male:female ratio of 3:1. Strong, diffuse nuclear immunoreactivity for cyclin D1 and BCOR was noted in 61% (n=11/18) and 83% (n=15/18) of CCSK, respectively, while it was significantly less in WT (n=3/10 for cyclin D1) (n=2/10 for BCOR). None of the MRT and CMN examples demonstrated any immunoreactivity. Interestingly, only the blastemal component of WTs showed distinct, rare nuclear immunoreactivity for cyclin D1 or BCOR and the combination of these was never positive in a given case.

CONCLUSION

Our results provide evidence that concurrent immunopositivity with cyclin D1 and BCOR is helpful in distinguishing CCSK from its morphologic mimics.

BCOR Overexpression in Renal Malignant Solitary Fibrous Tumors: A Close Mimic of Clear Cell Sarcoma of Kidney

BCOR immunoreactivity is a sensitive and highly specific marker for clear cell sarcoma of the kidney (CCSK). However, a subset of adult renal sarcomas which overexpress BCOR are negative for BCOR genetic alterations, including BCOR gene fusions or BCOR-internal tandem duplication, and thus remain unclassified. We report 5 such undifferentiated renal/perirenal sarcomas which raised the differential diagnosis of CCSK due to their morphologic appearance and strong BCOR immunoreactivity, but which on RNA sequencing proved to be malignant solitary fibrous tumors (SFTs). The neoplasms occurred in patients at an age range of 30 to 62 years. Three patients were females and 2 male. Four were primary renal neoplasms while one was perirenal. All 5 neoplasms were cellular, nonpleomorphic, undifferentiated sarcomas with branching capillary vasculature composed of primitive round to ovoid neoplastic cells with scant cytoplasm and nuclei having fine, evenly dispersed chromatin. None of the cases demonstrated the typical hyperchromatic fusiform nuclei, prominent collagen deposition, or hemangiopericytomatous vasculature of SFT. All 5 cases were strongly immunoreactive for BCOR. Three cases were CD34 negative, where the other 2 were only focally CD34 positive. STAT6 was subsequently found to be positive by immunohistochemistry in all 5 cases. In summary, we report a previously unrecognized mimic of CCSK: malignant SFTs with an undifferentiated/small round cell phenotype along with branching capillary vasculature, strong immunoreactivity for BCOR, and minimal or no immunoreactivity for CD34. As CCSK is treated with a specific chemotherapy regimen, this distinction has therapeutic implications.

Diagnostic Utility of BCOR Antibody in Clear Cell Sarcomas of Kidney

Purpose. Clear cell sarcoma of the kidney (CCSK) is an uncommon malignant renal tumor. It is the second most common renal pediatric renal malignancy after Wilms tumor. It exhibits a heterogeneous morphology, with overlapping features with its close differentials, which results in diagnostic challenges. There was no specific immunohistochemical marker in the past, to help in this regard. BCOR antibody has recently been suggested to be helpful in the differential diagnosis. We aim to study the utility of the BCOR antibody in the diagnosis of CCSK. Methods. We selected a total of 27 cases of CCSK (n = 12), Wilms tumor (n = 12), and congenital mesoblastic nephroma (n = 3). All cases were evaluated for the extent and intensity of nuclear labeling for BCOR antibody by immunohistochemistry (IHC). Results. We found that BCOR IHC was positive in 11 out of 12 cases with diffuse and strong staining in 8 of the cases. None of the cases of Wilms tumor and congenital mesoblastic nephroma were positive. Only 2 cases of Wilms tumor showed minimal and weak staining in <5% of cells. Conclusion. Diffuse and strong nuclear staining for the BCOR antibody is highly specific for CCSK among common pediatric renal malignancies. Our study confirms that BCOR IHC is a good IHC marker for the diagnosis of CCSK.

Clear cell sarcoma of the kidney in a 62-year-old patient presenting with generalized pruritus

Background

Clear cell sarcoma of the kidney (CCSK) is the second most common renal tumor in children following Wilms’ tumor. CCSK is extremely rare in adults, with only 25 adult cases reported in the medical literature.

Case presentation

We reported a 62-year-old man with a right renal mass presenting only with generalized pruritus who underwent radical right nephrectomy. With immunostaining, tumor cells were positive for expressed vimentin, neural cell adhesion molecule (NCAM, CD56), and Ki-67 and focally positive for p53, CD10 and Bcl-2. The histopathological diagnosis was CCSK. Two weeks after the operation, the generalized pruritus ended. One month after the operation, the patient started treatment with a regimen combining doxorubicin, vincristine, cyclophosphamide, and etoposide. At the 20-month follow-up visit, there was no evidence of local recurrence or metastases.

Conclusions

In a patient presenting with generalized pruritus, further evaluation for an underlying malignancy should be considered. It is difficult to distinguish CCSK from undifferentiated renal neoplasms. Immunohistochemistry could help to make exact histopathological diagnoses. The BCL-6 corepressor (BCOR) gene could play a significant role in CCSK tumorigenesis and be a good marker for CCSK diagnosis. Surgery with combination chemotherapy and radiation therapy could be used to treat CCSK in older patients.

The Iroquois homeobox proteins IRX3 and IRX5 have distinct roles in Wilms tumour development and human nephrogenesis

Wilms tumour is a paediatric malignancy with features of halted kidney development. Here, we demonstrate that the Iroquois homeobox genes IRX3 and IRX5 are essential for mammalian nephrogenesis and govern the differentiation of Wilms tumour. Knock‐out Irx3⁻/Irx5⁻ mice showed a strongly reduced embryonic nephron formation. In human foetal kidney and Wilms tumour, IRX5 expression was already activated in early proliferative blastema, whereas IRX3 protein levels peaked at tubular differentiation. Accordingly, an orthotopic xenograft mouse model of Wilms tumour showed that IRX3^−/− cells formed bulky renal tumours dominated by immature mesenchyme and active canonical WNT/β‐catenin‐signalling. In contrast, IRX5^−/− cells displayed activation of Hippo and non‐canonical WNT‐signalling and generated small tumours with abundant tubulogenesis. Our findings suggest that promotion of IRX3 signalling or inhibition of IRX5 signalling could be a route towards differentiation therapy for Wilms tumour, in which WNT5A is a candidate molecule for enforced tubular maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A method of gene expression data transfer from cell lines to cancer patients for machine-learning prediction of drug efficiency

Personalized medicine implies that distinct treatment methods are prescribed to individual patients according several features that may be obtained from, e.g., gene expression profile. The majority of machine learning methods suffer from the deficiency of preceding cases, i.e. the gene expression data on patients combined with the confirmed outcome of known treatment methods. At the same time, there exist thousands of various cell lines that were treated with hundreds of anti-cancer drugs in order to check the ability of these drugs to stop the cell proliferation, and all these cell line cultures were profiled in terms of their gene expression. Here we present a new approach in machine learning, which can predict clinical efficiency of anti-cancer drugs for individual patients by transferring features obtained from the expression-based data from cell lines. The method was validated on three datasets for cancer-like diseases (chronic myeloid leukemia, as well as lung adenocarcinoma and renal carcinoma) treated with targeted drugs - kinase inhibitors, such as imatinib or sorafenib.

Aberrant epigenetic regulation in clear cell sarcoma of the kidney featuring distinct DNA hypermethylation and EZH2 overexpression

The global methylation profile and the mutational status of 633 specific epigenetic regulators were analyzed in the pediatric tumor clear cell sarcoma of the kidney (CCSK). Methylation array analyses of 30 CCSKs revealed CCSK tumor DNA to be globally hypermethylated compared to Wilms tumor, normal fetal kidney, and adult kidney. The aberrant methylation pattern of CCSKs was associated with activation of genes involved in embryonic processes and with silencing of genes linked to normal kidney function. No epigenetic regulator was recurrently mutated in our cohort, but a mutation in the key epigenetic regulator EZH2 was discovered in one case. EZH2 mRNA was significantly higher in CCSK compared to Wilms tumor and normal kidney, and the EZH2 protein was strongly expressed in more than 90 % of CCSK tumor cells in 9/9 tumors analyzed. This was in striking contrast to the lack of EZH2 protein expression in Wilms tumor stromal elements, indicating that EZH2 could be explored further as a diagnostic marker and a potential drug target for CCSK.

Unravelling the link between embryogenesis and cancer metastasis

PURPOSE

Cancer as opposed to embryonic development is characterized by dysregulated, uncontrolled and clonal growth of cells. Inspite of that they share certain commonality in gene expression patterns and a number of cellular & molecular features. Consequently, in the present study we aimed to evaluate the role of a definite set of genes in fetal liver, primary liver cancers and metastatic liver tissue.

METHODS

The relative expression of fourteen candidate genes obtained by data mining and manual curation of published data (CXCL12, CXCR4, CK7, CDH1, CTNNB1, CLDN4, VEGFA, HIF1A, MMP9, p53, OPN, CDKN2A, TGFBR2, MUC16, β-actin) were performed on 62 tissues (32 liver metastasis tissues and 30 primary Liver cancer tissues), Fetal liver tissues (below and above 20weeks of gestation) and 2 sets of control samples by real-time quantitative reverse transcription PCR (qRT-PCR).

RESULTS

Results showed significant down-regulation of MMP9 and TP53 in Fetal liver above 20weeks of gestation whereas it was up-regulated in fetal liver below 20weeks of gestation, primary liver cancers and liver metastasis. Contradictory to that OPN and CDKN2A were significantly up-regulated in primary liver cancer, liver metastasis; down-regulated in fetal liver above 20weeks of gestation but were not expressed during early embryo development (below 20weeks of gestation). Moreover, MMP9 and TP53 demonstrated a strong correlation with MUC16 whereas CDKN2A and OPN showed correlation with CXCL12/CXCR4 signifying that MUC16, CXCL12/CXCR4 might be involved in the complex process of cancer metastasis.

CONCLUSION

MMP9, OPN, TP53 and CDKN2A were the identified markers that were expressed in a similar pattern in early embryonic development and cancer development & invasion suggesting that these genes are activated during embryogenesis and might be re-expressed in cancer metastasis. Moreover, these genes govern a pathway that might be activated during cancer metastasis. Thus, targeting these molecules may provide better treatment for metastatic liver cancers.

Data aggregation at the level of molecular pathways improves stability of experimental transcriptomic and proteomic data

High throughput technologies opened a new era in biomedicine by enabling massive analysis of gene expression at both RNA and protein levels. Unfortunately, expression data obtained in different experiments are often poorly compatible, even for the same biologic samples. Here, using experimental and bioinformatic investigation of major experimental platforms, we show that aggregation of gene expression data at the level of molecular pathways helps to diminish cross- and intra-platform bias otherwise clearly seen at the level of individual genes. We created a mathematical model of cumulative suppression of data variation that predicts the ideal parameters and the optimal size of a molecular pathway. We compared the abilities to aggregate experimental molecular data for the 5 alternative methods, also evaluated by their capacity to retain meaningful features of biologic samples. The bioinformatic method OncoFinder showed optimal performance in both tests and should be very useful for future cross-platform data analyses.

Recurrent BCOR Internal Tandem Duplication and YWHAE-NUTM2B Fusions in Soft Tissue Undifferentiated Round Cell Sarcoma of Infancy: Overlapping Genetic Features With Clear Cell Sarcoma of Kidney

Soft tissue undifferentiated round cell sarcoma (URCS) occurring in infants is a heterogenous group of tumors, often lacking known genetic abnormalities. On the basis of a t(10;17;14) karyotype in a pelvic URCS of a 4-month-old boy showing similar breakpoints with clear cell sarcoma of kidney (CCSK), we have investigated the possibility of shared genetic abnormalities in CCSK and soft tissue URCS. Most CCSKs are characterized by BCOR exon 16 internal tandem duplications (ITDs), whereas a smaller subset shows YWHAE-NUTM2B/E fusions. Because of overlapping clinicopathologic features, we have also investigated these genetic alterations in the so-called primitive myxoid mesenchymal tumor of infancy (PMMTI). Among the 22 infantile URCSs and 7 PMMTIs selected, RNA sequencing was performed in 5 and 2 cases, with frozen tissue, respectively. The remaining cases with archival material were tested for YWHAE-NUTM2B/E by fluorescence in situ hybridization (FISH) or reverse transcription-polymerase chain reaction (RT-PCR), and BCOR ITD by PCR. A control group of 4 CCSKs and 14 URCSs in older children or adults without known gene fusion and 20 other sarcomas with similar histomorphology or age at presentation were also tested. A YWHAE-NUTM2B fusion was confirmed in the index case by FISH and RT-PCR, whereas BCOR ITD was lacking. An identical YWHAE-NUTM2B fusion was found in another URCS case of a 5-month-old girl with a back lesion. The remaining cases and control group lacked YWHAE gene rearrangements; instead, consistent BCOR ITDs, similar to CCSK, were found in 15/29 (52%) infantile sarcoma cases (9/22 infantile URCS and 6/7 PMMTI). In the control cohort, BCOR ITD was found only in 3 CCSK cases but not in the other sarcomas. Histologically, URCS with both genotypes and PMMTI shared significant histologic overlap, with uniform small blue round cells with fine chromatin and indistinct nucleoli. A prominent capillary network similar to CCSK, rosette structures, and varying degree of myxoid change were occasionally seen. BCOR ITD-positive tumors occurred preferentially in the somatic soft tissue of the trunk, abdomen, and head and neck, sparing the extremities. RNAseq showed high BCOR mRNA levels in BCOR ITD-positive cases, compared with other URCSs. In summary, we report recurrent BCOR exon 16 ITD and YWHAE-NUTM2B fusions in half of infantile soft tissue URCS and most PMMTI cases, but not in other pediatric sarcomas. These findings suggest a significant overlap between infantile URCS and CCSK, such as age at presentation, histologic features, and genetic signature, thus raising the possibility of a soft tissue counterpart to CCSK.

BCOR Overexpression Is a Highly Sensitive Marker in Round Cell Sarcomas With BCOR Genetic Abnormalities

With the advent of next-generation sequencing, an increasing number of novel gene fusions and other abnormalities have emerged recently in the spectrum of EWSR1-negative small blue round cell tumors (SBRCTs). In this regard, a subset of SBRCTs harboring either BCOR gene fusions (BCOR-CCNB3, BCOR-MAML3), BCOR internal tandem duplications (ITD), or YWHAE-NUTM2B share a transcriptional signature including high BCOR mRNA expression, as well as similar histologic features. Furthermore, other tumors such as clear cell sarcoma of kidney (CCSK) and primitive myxoid mesenchymal tumor of infancy also demonstrate BCOR ITDs and high BCOR gene expression. The molecular diagnosis of these various BCOR genetic alterations requires an elaborate methodology including custom BAC fluorescence in situ hybridization (FISH) probes and reverse transcription polymerase chain reaction assays. As these tumors show high level of BCOR overexpression regardless of the genetic mechanism involved, either conventional gene fusion or ITD, we sought to investigate the performance of an anti-BCOR monoclonal antibody clone C-10 (sc-514576) as an immunohistochemical marker for sarcomas with BCOR gene abnormalities. Thus we assessed the BCOR expression in a pathologically and genetically well-characterized cohort of 25 SBRCTs, spanning various BCOR-related fusions and ITDs and YWHAE-NUTM2B fusion. In addition, we included related pathologic entities such as 8 CCSKs and other sarcomas with BCOR gene fusions. As a control group we included 20 SBRCTs with various (non-BCOR) genetic abnormalities, 10 fusion-negative SBRCTs, 74 synovial sarcomas, 29 rhabdomyosarcomas, and other sarcoma types. In addition, we evaluated the same study group for SATB2 immunoreactivity, as these tumors also showed SATB2 mRNA upregulation. All SBRCTs with BCOR-MAML3 and BCOR-CCNB3 fusions, as well as most with BCOR ITD (93%), and all CCSKs showed strong and diffuse nuclear BCOR immunoreactivity. Furthermore, all SBRCTs with YWHAE-NUTM2B also were positive. SATB2 stain was also positive in tumors with YWHAE-NUTM2B, BCOR-MAML3, BCOR ITD (75%), BCOR-CCNB3 (71%), and a subset of CCSKs (33%). In conclusion, BCOR immunohistochemical stain is a highly sensitive marker for SBRCTs and CCSKs with BCOR abnormalities and YWHAE-rearrangements and can be used as a useful diagnostic marker in these various molecular subsets. SATB2 immunoreactivity is also present in the majority of this group of tumors.

FOXD1-ALDH1A3 Signaling Is a Determinant for the Self-Renewal and Tumorigenicity of Mesenchymal Glioma Stem Cells

Glioma stem-like cells (GSC) with tumor-initiating activity orchestrate the cellular hierarchy in glioblastoma and engender therapeutic resistance. Recent work has divided GSC into two subtypes with a mesenchymal (MES) GSC population as the more malignant subtype. In this study, we identify the FOXD1-ALDH1A3 signaling axis as a determinant of the MES GSC phenotype. The transcription factor FOXD1 is expressed predominantly in patient-derived cultures enriched with MES, but not with the proneural GSC subtype. shRNA-mediated attenuation of FOXD1 in MES GSC ablates their clonogenicity in vitro and in vivo Mechanistically, FOXD1 regulates the transcriptional activity of ALDH1A3, an established functional marker for MES GSC. Indeed, the functional roles of FOXD1 and ALDH1A3 are likely evolutionally conserved, insofar as RNAi-mediated attenuation of their orthologous genes in Drosophila blocks formation of brain tumors engineered in that species. In clinical specimens of high-grade glioma, the levels of expression of both FOXD1 and ALDH1A3 are inversely correlated with patient prognosis. Finally, a novel small-molecule inhibitor of ALDH we developed, termed GA11, displays potent in vivo efficacy when administered systemically in a murine GSC-derived xenograft model of glioblastoma. Collectively, our findings define a FOXD1-ALDH1A3 pathway in controling the clonogenic and tumorigenic potential of MES GSC in glioblastoma tumors. Cancer Res; 76(24); 7219-30. ©2016 AACR.

Revealing the role of VEGFA in clear cell sarcoma of the kidney by protein-protein interaction network and significant pathway analysis

Despite clear cell sarcoma of the kidney (CCSK) being the second most common renal tumor in children, its mechanism has not yet been fully investigated. The aim of the present study was to investigate the potential role of vascular endothelial growth factor A (VEGFA) in CCSK development. Following preprocessing of the original GSE2712 data, the differentially-expressed genes (DEGs) between 14 CCSK and 3 fetal kidney samples were identified through Significance Analysis of Microarrays, using the R package. Pathway enrichment analysis was then performed on the DEGs. A protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes/Proteins database and the DEGs that were enriched in the most significant pathways. Following this, gene ontology analysis was performed on the VEGFA-associated genes, whilst transcription factor binding site analysis was conducted on the hot genes. A total of 2,681 DEGs, including 543 upregulated and 2,138 downregulated genes, were identified, and these were significantly enriched in pathways associated with cancer and focal adhesion. Furthermore, VEGFA, integrin β1, integrin αV, v-akt murine thymoma viral oncogene homolog 1 and endothelial growth factor receptor were identified as hot genes in the PPI network. In addition, the upregulated VEGFA-associated genes, cyclin D1 and cyclin-dependent kinase inhibitor 1B, affected kinase regulation, and the downregulated VEGFA-associated genes, receptor tyrosine-protein kinase erbB-2, mesenchymal-epithelial transition tyrosine kinase receptor and kinase insert domain receptor, were enriched in the protein tyrosine kinase process. It was identified that VEGFA was regulated by restorer of fertility, erythromycin resistance methylase, GA binding protein subunit α, norepinephrine transporter, nuclear factor κB and Sp2 transcription factor genes. Overall, VEGFA and its associated genes serve important roles during CCSK development, and alongside transcription factors, they may function as novel therapeutic targets for disease treatment.

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.

CONCLUSIONS

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.

BCOR internal tandem duplication and YWHAE-NUTM2B/E fusion are mutually exclusive events in clear cell sarcoma of the kidney

Clear cell sarcoma of the kidney (CCSK) is the second most common pediatric renal tumor. Two recurrent genetic aberrations have been described in CCSK. One is a fusion of YWHAE and NUTM2B/E, the other is an internal tandem duplication (ITD) in the BCOR gene. Here it is shown that YWHAE-NUTM2B/E fusion and the BCOR ITD are mutually exclusive events and activated different downstream signaling systems. This has important diagnostic implications and opens up for further mechanistic studies of CCSK pathogenesis.

The origin of the mammalian kidney: implications for recreating the kidney in vitro

The mammalian kidney, the metanephros, is a mesodermal organ classically regarded as arising from the intermediate mesoderm (IM). Indeed, both the ureteric bud (UB), which gives rise to the ureter and the collecting ducts, and the metanephric mesenchyme (MM), which forms the rest of the kidney, derive from the IM. Based on an understanding of the signalling molecules crucial for IM patterning and kidney morphogenesis, several studies have now generated UB or MM, or both, in vitro via the directed differentiation of human pluripotent stem cells. Although these results support the IM origin of the UB and the MM, they challenge the simplistic view of a common progenitor for these two populations, prompting a reanalysis of early patterning events within the IM. Here, we review our understanding of the origin of the UB and the MM in mouse, and discuss how this impacts on kidney regeneration strategies and furthers our understanding of human development.

Novel Karyotypes and Cyclin D1 Immunoreactivity in Clear Cell Sarcoma of the Kidney

Pathological diagnosis of clear cell sarcoma of the kidney (CCSK) is challenging as it resembles blastemal Wilms tumor (WT) and other pediatric sarcomas, and does not have any distinctive immunophenotype. The YWHAE-FAM22 translocation t(10;17)(q22;p13) has been reported in a subset of CCSK. This translocation also occurs in high-grade endometrial sarcoma, in which it is associated with cyclin D1 overexpression. Hence we seek to determine YWHAE-FAM22 translocation status and cyclin D1 immunoreactivity in a series of local CCSK cases. Of 8 CCSK cases from 7 patients identified, no CCSK had the YWHAE-FAM22 fusion transcript by reverse transcriptase-polymerase chain reaction. Novel karyotypes were identified for 2 cases: 1 had t(2;13)(q13;q22) and the other t(3:17)(q29;p11.2). Excluding a case with poor tissue section antigenicity, 7 of 7 CCSKs (100%) showed diffuse and strong nuclear cyclin D1 staining. Cyclin D1 immunohistochemistry was also performed on tissue microarrays of other pediatric renal tumors: blastemal areas of 18 WT cases were negative; 6 rhabdoid tumors and 1 metanephric adenoma showed patchy and weak staining; 3 mesoblastic nephromas and 18 of 29 neuroblastomas had positive staining. Cyclin D1 immunohistochemistry helps distinguish CCSK from blastemal WT and metanephric adenoma and rhabdoid tumors, but not from neuroblastomas and mesoblastic nephromas. Cyclin D1 overexpression in CCSK is not contingent on YWHAE-FAM22 translocation, and cyclin D1 inhibition may potentially be explored as a targeted therapeutic strategy in CCSK.

TCF21 hypermethylation in genetically quiescent clear cell sarcoma of the kidney

Clear Cell Sarcoma of the Kidney (CCSK) is a rare childhood tumor whose molecular pathogenesis remains poorly understood. We analyzed a discovery set of 13 CCSKs for changes in chromosome copy number, mutations, rearrangements, global gene expression and global DNA methylation. No recurrent segmental chromosomal copy number changes or somatic variants (single nucleotide or small insertion/deletion) were identified. One tumor with t(10;17)(q22;p13) involving fusion of YHWAE with NUTM2B was identified. Integrated analysis of expression and methylation data identified promoter hypermethylation and low expression of the tumor suppressor gene TCF21 (Pod-1/capsulin/epicardin) in all CCSKs except the case with t(10;17)(q22;p13). TARID, the long noncoding RNA responsible for demethylating TCF21, was virtually undetectable in most CCSKs. TCF21 hypermethylation and decreased TARID expression were validated in an independent set of CCSK tumor samples. The presence of significant hypermethylation of TCF21, a transcription factor known to be active early in renal development, supports the hypothesis that hypermethylation of TCF21 and/or decreased TARID expression lies within the pathogenic pathway of most CCSKs. Future studies are needed to functionally verify a tumorigenic role of TCF21 down-regulation and to tie this to the unique gene expression pattern of CCSK.

A novel embryonic plasticity gene signature that predicts metastatic competence and clinical outcome

Currently, very few prognosticators accurately predict metastasis in cancer patients. In order to complete the metastatic cascade and successfully colonize distant sites, carcinoma cells undergo dynamic epithelial-mesenchymal-transition (EMT) and its reversal, mesenchymal-epithelial-transition (MET). While EMT-centric signatures correlate with response to therapy, they are unable to predict metastatic outcome. One reason is due to the wide range of transient phenotypes required for a tumor cell to disseminate and recreate a similar histology at distant sites. Since such dynamic cellular processes are also seen during embryo development (epithelial-like epiblast cells undergo transient EMT to generate the mesoderm, which eventually redifferentiates into epithelial tissues by MET), we sought to utilize this unique and highly conserved property of cellular plasticity to predict metastasis. Here we present the identification of a novel prognostic gene expression signature derived from mouse embryonic day 6.5 that is representative of extensive cellular plasticity, and predicts metastatic competence in human breast tumor cells. This signature may thus complement conventional clinical parameters to offer accurate prediction for outcome among multiple classes of breast cancer patients.

An approach to renal masses in pediatrics

Renal masses in children may be discovered during routine clinical examination or incidentally during the course of diagnostic or therapeutic procedures for other causes. Renal cancers are rare in the pediatric population and include a spectrum of pathologies that may challenge the clinician in choosing the optimal treatment. Correct identification of the lesion may be difficult, and the appropriate surgical procedure is paramount for lesions suspected to be malignant. The purpose of this article is to provide a comprehensive overview regarding the spectrum of renal tumors in the pediatric population, both benign and malignant, and their surgical management.