1499

CTNNB1

CTNNB;catenin (cadherin-associated protein), beta 1, 88kDa;CTNNB1;catenin (cadherin-associated protein), beta 1, 88kDa

catenin beta-1

3p21

protein-coding

The benign epithelial neoplasm liver cell adenoma is rare, especially in childhood. We report 2 such cases, 1 of which was associated with Prader-Willi syndrome. Differential diagnosis of the liver cell adenomas on the basis of histopathologic findings proved difficult and was based on the absence of cellular and nuclear atypia, mitotic activity, and invasive growth. In both cases, immunohistochemical staining demonstrated the nuclear accumulation of beta-catenin, and in 1 case, the tumor cells carried a mutation of the beta-catenin gene. Recently, disregulation of the Wnt/beta-catenin pathway, attributable to abnormalities of the beta-catenin gene, has been reported to be a major event in the development of hepatocellular carcinomas and hepatoblastomas.Our report may be the first to describe the beta-catenin abnormalities in childhood liver cell adenoma. These findings imply that abnormalities of beta-catenin can be an early initiating event in human liver tumorigenesis.#CI- Copyright 2002, Elsevier Science (USA). ALL rights reserved.

Wilms' tumor (WT) is the most common childhood renal malignancy. Although several genetic loci such as the WT1 gene have been known to relate to the biology of WT, the cause of the tumor is complex and the implicated molecular pathways are largely unknown. The beta-catenin gene encodes a protein playing an important role in the Wnt signaling pathway, and its mutations that abrogate specific serine/threonine phosphorylation sites and express oncogenic effect have been found in a variety of tumors. Implication of beta-catenin mutations in WT was investigated in 24 tumors collected from 20 WT patients. One patient had a totalof five multiple tumors simultaneously in the bilateral kidneys. Exon 3 and its flanking regions encompassing mutational hot spots of the gene were examined by PCR-based methods. Samples indicating to harbor mutations were further analyzed by sequencing. Six tumors (6/24, 25%) from 4 patients (4/20, 20%) were confirmedto have mutations in heterozygous status. ALL the mutations, including five different types, were uniformly observed at codon 45 (Ser). Three mutations, Ser45Phe (TCT --> TTT), Ser45Tyr (TCT --> TAT), and Delta45 (deletion of TCT), were found in 3 of 19 unilateral WTs. Other three mutations were detected in three of five multiple tumors developed in the bilateral WT patient; a mutation of Delta45 in one of two tumors in the right kidney, and Ser45Cys (TCT --> TGT) and Ser45Pro (TCT --> CCT) in two of three tumors in the left kidney. Frequent beta-catenin mutations preferentially occurring at codon 45 most likely indicatespecial importance of this codon for the development of WT and existence of an underlying mechanism causing such a tissue-specific mutational pattern.

OBJECT: Medulloblastoma is a malignant cerebellar tumor of childhood and is difficult to cure due to frequent cerebrospinal fluid dissemination. Amplification of the c-myc gene (4%) and messenger (mRNA) overexpression (50%) are known to be adverse prognostic indicators. Because mRNA overexpression cannot be explained by gene amplification alone, mechanisms other than gene amplification are postulated. Molecules on the Wnt signal pathway in primary tumors were examined. METHODS: Immunohistochemical and cytogenetic examinations of beta- and gamma-catenin, c-myc, N-myc, and cyclin D1 in 24 primary medulloblastomas were conducted, and their clinical relevance was evaluated. Cytoplasmic/membranous staining of beta- and gamma-catenin was detected in 19 (79%) and nine (37%) cases, respectively, and nuclear expression of cyclin D1 and c-myc was detected in six (25%) and 21 (83%) cases, respectively. The expressionlevels of gamma-catenin in Western blot analysis and immunohistochemistry were similar. By differential polymerase chain reaction, c-myc and N-myc were amplified separately in two large cell/anaplastic medulloblastomas. No cyclin D1amplification, or beta- or gamma-catenin mutations were found. Kaplan-Meier analysis revealed no dissemination at diagnosis (Chang Grade M0) and gamma-catenin expression was correlated with good prognosis (p = 0.0002 and 0.003, respectively). expression of gamma-catenin was also significant in the M0group (p = 0.022). expression of cyclin D1 showed a trend toward adverse outcome(p = 0.057) and ALL patients in whom cyclin D1 expression was found died of disease. CONCLUSIONS: expression of gamma-catenin is of great prognostic value and its immunohistochemistry may be useful for further stratification of treatment. Cyclin D expression may have the potential to be an adverse prognostic indicator.

mutations of beta-catenin have been identified in the majority of pediatric hepatic malignancies, including hepatoblastoma (HB) and hepatocellular carcinoma(HCC), suggesting its important contribution in hepatic tumorigenesis in this age group. However, the role of beta-catenin/canonical Wnt signaling pathway in the neoplastic growth of cancer cells has not been directly studied. To address beta-catenin's capability in maintaining the malignant phenotype in established pediatric HB and HCC cell lines, HuH-6 and HepG2, harboring mutated and overexpressed beta-catenin, we carried out a series of in vitro analyses througha transfection of short interfering RNAs (siRNAs) to generate a loss-of-functionmodel. HuH-7, another HB cell line derived from a pediatric patient without a stabilizing mutation was used for comparison. RNA interference successfully manipulated the degradation of overexpressed beta-catenin. In ALL cell lines, beta-catenin mRNA was suppressed by 80-90% after 48 h of transfection, and a reduction of its protein expression was demonstrated. In HuH-6 and HepG2, the pre-existing beta-catenin nuclear accumulation disappeared and reductions of beta-catenin downstream target genes, c-myc and cyclinD1, were also evidenced after the treatment. The in vitro proliferation of both cell lines was transiently inhibited. In contrast, the suppression of beta-catenin in HuH-7 didnot lead to a significant change in the expression of target genes or cellular proliferation. Our data indicate that beta-catenin can be considered a specific target for gene therapy in pediatric hepatic tumors with mutations and overexpression of this gene.

Hepatoblastoma (HBL), a major childhood malignant neoplasm, represents the most frequent malignant liver tumor in childhood. Recent reports have shown the CTNNB1 coding beta-catenin protein to be frequently mutated or deleted at hot-spot regions involving exon 3 in HBL. We investigated the genetic alterations of the CTNNB1 coding beta-catenin protein and expression of several genes downstream ofWnt signals in 4 benign and 17 malignant pediatric liver tumors (PLTs) consisting of 15 HBL, 1 hepatocellular carcinoma, and 1 hepatic immature sarcoma. Of 17 malignant PLTs, 10 (56%) revealed pathogenic alterations of the CTNNB1 gene, including 4 with missense mutations at codons 28, 32, 34 or 44, and 6 with interstitial deletions that partially or totally affected exon 3. ALL 6 deletions were in-frame deletions without a frame shift. The high frequency without any correlation to histological type indicates that the CTNNB1 gene alteration is a crucial event in the tumorigenesis of malignant PLTs. The immunohistochemical studies in 17 malignant PLTs demonstrated the nuclear/cytoplasmic accumulation of beta-catenin to be positive in ALL tumor specimens except for one hepatic sarcoma. A histological examination revealed ALL HBL cases involving tumors without detectable CTNNB1 gene alterations to show high expression of beta-catenin, thus indicating the accumulation of beta-catenin to be a common event in malignant PLTs, including HBL and hepatocellular carcinoma. Among the Wnt signal genes downstream of beta-catenin, E-cadherin is expressed in ALL malignant PLTs, while cyclin D1 expression was significantly detected in malignant PLTs with an advanced stage of disease. An immunohistological examination of nuclear accumulation of beta-catenin may thus be useful for diagnosing malignant PLTs. On the other hand, the expression of cyclin D1, a gene downstream of beta-catenin, might play a role in tumor progression.

The WNT/beta-catenin pathway is involved in numerous human cancers. mutations ofthe CTNNB1 (beta-catenin) gene have also been detected in a subset of pediatric Wilms tumors, but the target genes of the deregulated WNT/beta-catenin pathway in these tumors have yet to be identified. To compare gene expression profiles of Wilms tumors with and without mutations of CTNNB1, we used 11.5-k cDNA microarrays. Most of the tumors (86%) had received preoperative chemotherapy as mandated by the European SIOP protocol. The comparison between Wilms tumors withand without CTNNB1 mutations revealed several target genes specifically deregulated in CTNNB1-mutated Wilms tumors. Among these, PITX2, APCDD1, and two members of the endothelin axis (EDN3 and EDNRA) are directly activated downstream targets of the WNT/beta-catenin pathway that may enhance proliferation of these tumor cells. In addition, several upstream inhibitors of WNT/beta-catenin signaling like WIF1 and PRDC were also strongly up-regulated in the CTNNB1-mutated Wilms tumors. This overexpression may be a negative feedback mechanism in tumors with uncontrolled WNT signaling. Moreover, we identified deregulated genes in both the retinoic acid and the RAS pathways, such as ATX/ENPP2 and RIS1, suggesting an association between these two pathways with that of WNT. In addition, the strong representation of muscle-related genes in the expression profile of CTNNB1-mutated Wilms tumors corresponded to histologically detectable areas of myomatous cells in these tumors that displayed intense and preferential nuclear beta-catenin antibody staining. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.#CI- (c) 2006 Wiley-Liss, Inc.

The ependymoma is the second most common malignant brain tumor of childhood; however, its molecular basis is poorly understood. The formation of multiple ependymomas has been reported as an occasional feature of Turcot syndrome type 2(TS2), a familial cancer syndrome caused by inherited mutations of the APC tumorsuppressor gene, and characterised by the concurrence of a primary CNS tumor (predominantly medulloblastoma) and multiple colorectal adenomas. APC is a critical component of the Wnt/Wingless signaling pathway, which is disrupted in sporadic cancers (e.g., colorectal adenomas, hepatocellular carcinomas, and medulloblastomas) by somatic mutations affecting multiple genes encoding alternative pathway components, including APC and CTNNB1 (encoding beta-catenin). To investigate any role for genetic disruption of the Wnt/Wingless pathway in sporadic ependymomas, we performed mutation analysis of APC and CTNNB1 in 77 primary tumors. Two synonymous APC polymorphisms (PRO1442PRO; THR1493THR) were identified, which were detected at equivalent rates in ependymomas and control nonneoplastic DNA samples (n =50); however, no further APC or CTNNB1 sequence variations were found. In summary, although inherited APC mutations may be associated with ependymoma development in certain TS2 cases, these data indicatethat somatic mutations affecting APC and CTNNB1 do not play a major role in the pathogenesis of sporadic ependymomas.

Significant progress has been made in understanding the molecular basis of pediatric malignancies. Mechanisms of pediatric acute leukemia induction includehyperdiploidy, aberrant expression of proto-oncogenes, and activation of transcription factors or kinases by aberrant fusion genes. Molecular analysis ofthese alterations has facilitated the recognition of distinct groups with different sensitivity to therapy, and identified potential targets for antileukemic agents. Similar analysis of pediatric soft tissue and bone tumors also resulted in the identification of specific fusion genes, and their characterization has contributed greatly to understand their biology. Molecular assays for these rearrangements have become important tools in classifying thesetumors, providing important prognostic data. However, the understanding of mechanisms involved in the pathogenesis of many other pediatric malignancies, including some embryonal tumors--believed to arise due to perturbation of the normal developmental program--is still vastly incomplete. The Department of Pathology at Texas children's Hospital is one of the children's Oncology Group (COG) reference centers for pediatric liver tumors. We have been particularly interested in the biology of hepatoblastoma, the most common type of pediatric liver tumor. Although a number of cytogenetic and molecular abnormalities have been described for this type of embryonal tumor, its pathogenesis is still poorly understood. In an attempt to explore the role of different signaling pathways inthis disease, we analyzed the expression patterns of different histologic subtypes of hepatoblastoma using cDNA microarray analysis, qualitative reverse transcription, polymerase chain reaction (QRT-PCR), and immunohistochemistry. Wnt signaling pathway, critical both in development and in neoplasia, appears to be particularly relevant in these tumors. mutations of the beta-catenin gene are present in over 90% of hepatoblastomas, leading to activating transcription of anumber of target genes. The pattern of beta-catenin expression and type of mutation in groups of tumors are crucial to understand the corresponding differences in their gene expression profiles. Our findings are consistent with a relationship between poor histologic phenotype and beta-catenin activation, indicating the potential utility of targeted gene expression assays to identify molecular events related to the pathogenesis and prognosis of hepatoblastomas. Integration of clinical, morphologic, phenotypic, cytogenetic, and molecular data has become the basis of novel prognostic prediction and therapeutic strategies in pediatric leukemia. Similarly, integration of new genetic and molecular data with clinical, and other diagnostic information will be crucial for accurate classification of pediatric tumors, risk stratification, and successful development of new therapies for pediatric oncologic patients.

Neuroblastoma (NB) is a frequently lethal tumor of childhood. MYCN amplificationaccounts for the aggressive phenotype in a subset while the majority have no consistently identified molecular aberration but frequently express MYC at high levels. We hypothesized that activated Wnt/beta-catenin (CTNNB1) signaling mightaccount for this as MYC is a beta-catenin transcriptional target and multiple embryonal and neural crest malignancies have oncogenic alterations in this pathway. NB cell lines without MYCN amplification express higher levels of MYC and beta-catenin (with aberrant nuclear localization) than MYCN-amplified cell lines. Evidence for aberrant beta-catenin-TCF transcriptional activity was demonstrated using expression profiles from 73 primary NBs. Findings included increased WNT ligands (WNT1, WNT6, WNT7A, WNT10B), DVL1 and TCF7 expression in high-risk NBs without MYCN amplification, consistent with canonical beta-cateninsignaling. More directly, Patterns of Gene expression and Gene Set Enrichment Analyses demonstrated beta-catenin target genes (for example, MYC, PPARD, NRCAM,CD44, TCF7) as coordinately upregulated in high-risk NBs without MYCN amplification in comparison to high-risk MYCN-amplified or intermediate-risk NBs, supporting pathway activation in this subset. Thus, high-risk NBs without MYCN amplification may deregulate MYC and other oncogenic genes via altered beta-catenin signaling providing a potential candidate pathway for therapeutic inhibition.

BACKGROUND: This study investigated the genetic events leading to tumorigenesis in a patient affected with WAGR syndrome who developed multiple distinct Wilms tumors (WTs). PROCEDURE AND RESULTS: At 1 year of age, the child developed two synchronous bilateral WTs that were resected by partial nephrectomy. Histologically, these tumors were fetal rhabdomyomatous nephroblastomas. Immunohistochemical study revealed the absence of nuclear expression of WT1 protein, while beta-catenin protein was expressed at nuclear level by the large majority of tumor cells. Molecular investigations of WT1 gene and exon 3 of beta-catenin (CTNNB1) gene detected no mutations. At 4 years of age, 28 months after the chemotherapy completion, a third WT was diagnosed in the left kidney, and surgically removed before any further chemotherapy. Nine months after surgery, a metastasis was detected in the left lung. Both the third renal tumor and the lung metastasis showed a blastema-predominant morphology. Immunohistochemistry confirmed the lack of expression of WT1 protein, while beta-catenin protein was expressed at nuclear level by the large majority of tumor cells. Molecular analysis of the third renal tumor and the lung metastasisrevealed a 4 bp deletion in exon 7 of WT1 gene, leading to a frameshift of the reading frame and to a premature stop of the translation (c.925_928delACTC, p.T309LfsX71); no mutations in the exon 3 of the beta-catenin gene were documented. CONCLUSIONS: These data demonstrate that multiple WTs can arise as aconsequence of different genetic events in a patient with genetic predisposition, such as WAGR syndrome.#CI- (c) 2008 Wiley-Liss, Inc.

BACKGROUND: mutations in the Wilms tumor (WT) suppressor 1 gene (WT1) and the cadherin-associated protein beta1 gene (CTNNB1) are found predominantly in stromal type WT, defining a genetic subgroup. The clinical relevance of these mutations remains to be determined. METHODS: A long-term follow-up study was performed for 71 patients (International Society of pediatric Oncology Study 9/Society for pediatric Oncology; n = 77 tumors) with known molecular genetic status. Eight patients had bilateral disease, including 2 patients with a WT in both kidneys and 5 patients with a WT in 1 kidney and nephrogenic rests (NRs) inthe other kidney. The response to preoperative chemotherapy, relapses, metastases, metachronous tumor development, and deaths were evaluated with a median follow-up of 12 years and 4 months. RESULTS: Nineteen patients (n = 24 tumors) had WT1 mutations, and 16 were constitutional mutations. Three patients with germline mutations had second tumor events: Two patients developed a WT in the kidney with NRs 3 years and 11 years after the first tumor; and 1 patient developed second tumors after 2 years, 1 in the kidney with a previous WT and 1 in the kidney with a previous NR. Eighteen of the WT1 mutant tumors were analyzed for CTNNB1 mutations, and ALL had mutations. A poor volumetric response (progression and <50% reduction) was observed in ALL patients who had tumors with a WT1 mutation and in 23 of 52 nonmutant tumors. CONCLUSIONS: Patients with WT1 germline mutations had an increased risk for bilateral disease and second tumor events. Therefore, the authors concluded that tumor surveillance until adulthoodshould be considered. Although tumors with both WT1 and CTNNB1 mutations had a poor volumetric response, there was no significant difference in overall survival in this cohort of patients with and without WT1 mutations.#CI- (c) 2008 American cancer Society.

Wilms' tumor is the most common pediatric renal neoplasm, but its occurrence in adults is very rare. In contrast to pediatric Wilms' tumor (PWT), very little isknown about the pathogenesis of adult Wilms' tumor (AWT). Despite there currently being no morphological difference between AWT and PWT, a cytogenetic study has suggested that the pathogenesis of AWT might be different from that of PWT. Although dysregulation of the Wnt pathway has been implicated in PWT, its role in AWT has never been investigated. To investigate the role of dysregulation of theWnt pathway in AWT, tumor samples from 4 AWTs and 19 PWTs were surveyed for subcellular localization of beta-catenin by immunohistochemistry and potential mutation of the beta-catenin gene by sequencing. Nuclear translocation of beta-catenin was found in one out of four cases of AWT, but none of them carriedmutation of the beta-catenin gene. By comparison, nuclear translocation for beta-catenin and mutation of the beta-catenin gene were present in 53% (10/19) and 15.8% (3/19) of PWTs, respectively. Of the three mutations identified, we found a novel mutation combining a silent mutation (TCT to TCC, Ser37Ser) and anin-frame six-base-pair deletion (del GGTGCC, del Gly38Ala39). This report suggests that dysregulation of the Wnt pathway might also play a role in the pathogenesis of AWT.

Hepatoblastoma, the most common pediatric liver cancer, is tightly linked to excessive Wnt/beta-catenin signaling. Here, we used microarray analysis to identify two tumor subclasses resembling distinct phases of liver development and a discriminating 16-gene signature. beta-catenin activated different transcriptional programs in the two tumor types, with distinctive expression of hepatic stem/progenitor markers in immature tumors. This highly proliferating subclass was typified by gains of chromosomes 8q and 2p and upregulated Myc signaling. Myc-induced hepatoblastoma-like tumors in mice strikingly resembled the human immature subtype, and Myc downregulation in hepatoblastoma cells impaired tumorigenesis in vivo. Remarkably, the 16-gene signature discriminated invasive and metastatic hepatoblastomas and predicted prognosis with high accuracy.

We report on a child with X-linked nephrogenic diabetes insipidus (NDI) who developed Wilms tumor (WT). Nephrogenic diabetes insipidus is caused by mutations of the arginine vasopressin receptor (AVPR2) or aquaporin-II (AQP2) genes. Wilmstumor is also genetically heterogeneous and is associated with mutations of WT1 (15-20%), WTX (20-30%) and other loci. The boy presented at 5 months with failure to thrive, polyuria, hypernatremia and abdominal mass. Analysis of leukocyte DNAshowed a novel missense mutation (Q174H) of the AVPR2 gene, which was not present in his mother. In cells (WitS) isolated from the tumor, WTX mRNA expression and coding sequence were intact. However, we identified a 44-kb homozygous deletion of the WT1 gene spanning exons 4 to 10. The WT1 deletion was not present in leukocyte DNA from the patient or his mother. We also noted strong beta-catenin (CTNNB1) expression in the tumor cells and identified a heterozygote missense Ser45Cys mutation of exon 3 of CTNNB1. However, the mutation was absent both in the constitutional DNA of the patient and his mother. The concurrence of WT and NDI has not been previously reported and may be unrelated. Nevertheless, this case nicely illustrates the sequence of events leading to sporadic Wilms tumor.

Wilms tumor (WT) is one of the most common solid tumors in childhood. mutations in WT1 and CTNNB1 are well established as causal alterations in about 10-15% of cases. Recently, WTX (WT gene on the X-chromosome), a gene implicated in WNT signaling, has been identified as a third WT gene. We determined the mutation status of WTX, CTNNB1, and WT1 in a large set of 429 tumors. Genomic WTX alterations were identified in 17% of WTs, equally distributed between males andfemales. Analysis of 104 WT samples for WTX point mutations revealed a rate of only 2%. An additional 11.5% of tumor samples lacked expression of WTX mRNA. These WTX alterations can occur in parallel to WT1 or CTNNB1 mutations. However,we could not find a significant correlation between WTX deletion status or expression level and clinical parameters suggesting that WTX mutations apparently have little direct impact on tumor behavior and presentation. Incomplete deletions of WTX in several cases suggested heterogeneity in tumors. In a small number of cases, we could analyze separate tumor fragments or microdissected regions with different histology of tumors with heterozygous point mutations. Despite complete allele losses at other sites in the genome, we detected varyingdegrees of WTX mutation. This suggests that WTX alteration is not an essential and early mutation needed to drive tumorigenesis, but rather a later event that may affect only a fraction of cells with unclear clinical relevance.#CI- (c) 2009 Wiley-Liss, Inc.

PURPOSE: Wilms' tumor (WT), the most common pediatric renal malignancy, is associated with mutations in several well-characterized genes, most notably WT1,CTNNB1, WTX, and TP53. However, the majority of cases do not harbor mutations inthese genes. We hypothesized that additional drivers of tumor behavior would be contained within areas of consistent genomic copy number change, especially those associated with the WT risk groups defined by the International Society of Paediatric Oncology (SIOP). EXPERIMENTAL DESIGN: We analyzed high-resolution (Affymetrix 250K single nucleotide polymorphism array) genomic copy number profiles of over 100 tumors from selected risk groups treated under the SIOP protocols, further characterizing genes of interest by sequencing, Multiplex Ligation-dependent Probe Amplification, or fluorescence in situ hybridization. RESULTS: We identified FBXW7, an E3 ubiquitin ligase component, as a novel Wilms' tumor gene, mutated or deleted in approximately 4% of tumors examined. Strikingly, 3 of 14 (21%) of tumors with epithelial type histology after neoadjuvant chemotherapy had FBXW7 aberrations, whereas a fourth WT patient had germline mutations in both FBXW7 and WT1. We also showed that MYCN copy number gain, detected in 9 of 104 (8.7%) of cases, is relatively common in WT and significantly more so in tumors of the high risk diffuse anaplastic subtype (6 of 19, 32%). CONCLUSIONS: Because MYCN is itself a target of FBXW7-mediated ubiquitination and degradation, these results suggest that a common pathway is dysregulated by different mechanisms in various WT subtypes. Emerging therapies that target MYCN, which is amplified in several other pediatric cancers, may therefore be of value in high risk Wilms' tumor.#CI- Copyright 2010 AACR.

Aggressive fibromatosis is a benign tumor with a high recurrence rate after surgical resection, particularly in children. Abnormal regulation of beta-catenin in the presence or absence of a change of genotype has been identified in adult sporadic aggressive fibromatosis. However, the status of beta-catenin expressionand mutation remains unclear in pediatric patients. The present study was designed to analyze the expression and mutation status of beta-catenin in pediatric aggressive fibromatosis. B-catenin expression was analyzed by immunohistochemistry in 32 samples from pediatric patients with aggressive fibromatosis (21 recurrent cases and 11 primary-onset cases) and 15 control subjects. Somatic point mutations in beta-catenin exon 3 were identified by sequencing of polymerase chain reaction products. Nuclear expression of beta-catenin was detected in 94% (30/32) of aggressive fibromatosis samples and 13% (2/15) of control samples (P < 0.001). mutations in exon 3 of the beta-catenin gene were identified in 78% (25/32) of aggressive fibromatosis samples (19/21 recurrent cases, 6/11 primary-onset cases; P = 0.032). The primary mutation in the recurrent cases occurred at codon 45 (S45F), while codon 41 (T41A) was most frequently mutated in the primary-onset cases (P = 0.002). Abnormal expression of beta-catenin appears to occur frequently in pediatric aggressive fibromatosis. Muftations in exon 3 of the beta-catenin gene, particularly the S45F mutation, may represent risk factors for recurrence in pediatric patients and could potentially be used as prognostic factors.

Adrenocortical tumors (ACT) are more frequent during childhood, but they can appear at any age. ACTs can be classified in functioning, nonfunctioning (mainlyobserved in adults) and mixed. The diagnosis is based on clinical, biochemical findings and imaging. In children, in order to classify ACT as benign or malignant, tumor staging classification is recommended. Regarding molecular markers some studies should be taken into account: besides TP53 mutations, previous studies have also provided evidences of IGF2 involvement in 90% of the malignant ACT. mutations altering exon 3 of CTNNB1 gene have been found in 6% ofchildhood ACTs. In addition, microRNAs can act as negative regulators of gene expression by targeting mRNA controlling cell growth, differentiation and apoptosis and have been implicated in adrenal tumorigenesis. High-throughput methods to analyze genome-wide expression have been developed over the last decade and identified a subset of tumors with good or poor prognosis. In the future, these studies can provide the basis of specific drug development, which can treat patients according to specific altered signaling pathway.

Desmoid fibromatosis is a rare, locally aggressive fibroblastic/myofibroblastic tumor that occasionally involves children. We examined a series of pediatric desmoids for CTNNB1 mutations, seen in sporadic tumors, and APC germline mutations, associated with familial adenomatous polyposis (FAP). Forty-four desmoids in pediatric patients were identified in the pathology files of 2 largereferral centers (1995-2009). Clinical charts were reviewed for history of FAP. Germline APC gene mutations were determined on blood samples from patients presenting with FAP. Immunohistochemistry for beta-catenin was performed. CTNNB1genotyping was done by Sanger sequencing on formalin-fixed paraffin-embedded tissue. CTNNB1 mutations were observed in 29 of 44 (66%) desmoids, with 3 mutations identified: T41A (64%), S45F (29%), and S45P (7%). Germline APC mutations were present in 7 (16%) desmoid patients. Eight (18%) patients had desmoids that were wild type for CTNNB1 and had no known clinical signs or family history suspicious for FAP at the time of testing or with extended follow up (n = 6). Beta-catenin nuclear labeling was observed in 38 of 41 (92%) tested cases, 34 (89%) of which showed mutations in either CTNNB1 (n = 29) or APC (n = 5). Nuclear localization of beta-catenin was seen in the majority of pediatric desmoids and was most often associated with somatic mutations in CTNNB1. However, a significant proportion of pediatric patients harbored germline mutations in APC.Given the implications, genetic counseling is recommended for children diagnosedwith desmoid tumors lacking CTNNB1 mutations because this population is enrichedfor FAP patients.

Wilms tumor (WT) accounts for approximately 95 % of ALL pediatric renal tumors, with a peak incidence between 2 and 3 years of age. It occurs in sporadic and congenital forms, the latter often occurring before 1 year of age. Incidence declines with age, and WT rarely is observed in adults. WT is an embryonal tumorof the kidney caused by aberrant proliferation of early metanephric kidney cells. It can arise from more than one developmental error and therefore several subtypes can be defined. WT1, a zinc-finger transcription factor, was identifiedas the first WT gene. Other genes frequently altered somatically in subsets of WT are CTNNB1 and WTX; both genes influence the Wnt signalling pathway. Imprinting alterations of genes in 11p15 are also observed in a subset of WTs. Other pediatric renal tumors occur less often, e.g. malignant rhabdoid tumor of the kidney, clear-cell sarcoma, desmoplastic small-round-cell tumors, congenital mesoblastic nephroma, renal cell carcinoma of childhood, renal primitive neuroectodermal tumors, renal medullary carcinoma, and synovial sarcoma of the kidney. In most of these, characteristic genetic alterations have been identified that help in the unequivocal diagnosis of these childhood renal cancers that areoften difficult to distinguish.

Nested stromal epithelial tumor of the liver is a rare neoplasm of early childhood and adolescence with a characteristic nested morphology of spindle andepithelioid cells. Histogenesis and pathogenesis of this neoplasm are, however, still unclear. Because the characteristic nested morphology with spindle mesenchymal and epithelioid cells is suggestive of altered mesenchymal-epithelial transition and beta-catenin mutations are rather common in other liver tumors such as hepatoblastomas, we investigated the beta-catenin gene in 2 nested stromal epithelial tumors of the liver and analyzed additional factors involved in mesenchymal-epithelial transition, such as E-cadherin, vimentin, c-Met, TWIST, SNAIL, and SLUG by molecular genetic and immunohistochemical methods. mutation analysis of both cases revealed large deletions in exon 3 of the beta-catenin gene (155 and 228 base pairs), resulting in an accumulation of beta-catenin in the cytoplasm and nuclei of tumor cells, as evidenced by immunohistochemistry. The expression of the mesenchymal-epithelial transition factors SNAIL, SLUG, TWIST, c-Met, vimentin, and beta-catenin was generally increased, whereas E-cadherin was decreased. Morphological and immunohistochemical analysis, however, showed a variable expression pattern of various epithelial and mesenchymal markers both in the spindle and epithelioid cell compartments of thetumors, thus illustrating the transitional status of the tumor cells. In conclusion, our data clearly identify protein stabilizing mutations of the beta-catenin gene as a common feature of nested stromal epithelial tumors of theliver, similarly as in hepatoblastomas. Therefore, nested stromal epithelial tumors of the liver may be regarded as a variant of hepatoblastoma, despite differing from it in clinical and morphological aspects. The characteristic epithelioid-spindle morphology along with the incomplete epithelial differentiation proposes impaired mesenchymal-epithelial transition as a possible pathogenetic mechanism of this rare tumor. However, because only 2 cases were studied, this hypothesis awaits further validation.#CI- Copyright (c) 2012 Elsevier Inc. ALL rights reserved.

OBJECTIVES: We investigated four components of the Wnt signaling pathway in medulloblastomas. Medulloblastoma is the most common type of malignant pediatricbrain tumor, and the Wnt signaling pathway has been shown to be activated in this type of tumor. METHODS: Sixty-one medulloblastoma cases were analyzed for beta-catenin gene (CTNNB1) mutations, beta-catenin protein expression via immunostaining and Wnt signaling pathway-related gene expression. ALL data were correlated with histological subtypes and patient clinical information. RESULTS:CTNNB1 sequencing analysis revealed that 11 out of 61 medulloblastomas harbored missense mutations in residues 32, 33, 34 and 37, which are located in exon 3. These mutations alter the glycogen synthase kinase-3beta phosphorylation sites, which participate in beta-catenin degradation. No significant differences were observed between mutation status and histological medulloblastoma type, patient age and overall or progression-free survival times. Nuclear beta-catenin accumulation, which was observed in 27.9% of the cases, was not associated with the histological type, CTNNB1 mutation status or tumor cell dissemination. The relative expression levels of genes that code for proteins involved in the Wnt signaling pathway (CTNNB1, APC, AXIN1 and WNT1) were also analyzed, but no significant correlations were found. In addition, large-cell variant medulloblastomas presented lower relative CTNNB1 expression as compared to the other tumor variants. CONCLUSIONS: A small subset of medulloblastomas carry CTNNB1 mutations with consequent nuclear accumulation of beta-catenin. The Wnt signaling pathway plays a role in classic, desmoplastic and extensive nodularitymedulloblastoma variants but not in large-cell medulloblastomas.

Constitutional mismatch repair deficiency (CMMR-D) due to biallelic germline mutations in one of four mismatch repair genes causes a childhood cancer syndrome characterized by a broad tumor spectrum including hematological malignancies, and brain and Lynch syndrome-associated tumors. Herein, we report three children whohad in addition to CMMR-D-associated malignancies multiple pilomatricomas. Theseare benign skin tumors of hair matrical differentiation frequently associated with somatic activating mutations in the ss-catenin gene CTNNB1. In two of the children, the diagnosis of CMMR-D was confirmed by the identification of biallelic germline PMS2 mutations. In the third individual, we only found a heterozygous germline PMS2 mutation. In ALL nine pilomatricomas with basophilic cells, we detected CTNNB1 mutations. Our findings indicate that CTNNB1 is a target for mutations when mismatch repair is impaired due to biallelic PMS2 mutations. An elevated number of activating CTNNB1 alterations in hair matrix cells may explain the development of multiple pilomatricomas in CMMR-D patients.Of note, two of the children presented with multiple pilomatricomas and other nonmalignant features of CMMR-D before they developed malignancies. To offer surveillance programs to CMMR-D patients, it may be justified to suspect CMMR-D syndrome in individuals fulfilling multiple nonmalignant features of CMMR-D (including multiple pilomatricomas) and offer molecular testing in combination with interdisciplinary counseling.#CI- Copyright (c) 2013 Wiley Periodicals, Inc.