Wilms tumor 1 (WT1) protein: Diagnostic utility in pediatric tumors

Immunotherapy Applications for Thymine Dimers and WT1 Antigen in Renal Cancers: A Comparative Statistical Analysis

Renal cell carcinoma (RCC) remains incurable in advanced stages. Biomarkers have proven to be quite useful in cancer therapeutics. Herein, we provide a comparative/integrative statistical analysis of seminal immunohistochemistry (IHC) findings for Wilms' Tumor 1 antigen (WT1) and thymine dimers (TDs), emerging as atypical, yet promising, potential biomarkers for RCCs. We assessed WT1/TD reactivity in adult RCC tumor cells, tumor microenvironment (TME), and tumor-adjacent healthy renal tissue (HRT). WT1 positivity was scarce and strictly nuclear in tumor cells, whereas TD-reactive tumor tissues were prevalent. We report statistically significant positive correlations between the density of reactive RCC cellularity and the intensity of nuclear staining for both biomarkers (WT1 - rho = 0.341, p-value = 0.036; TDs - rho = 0.379, p-value = 0.002). RCC stromal TME TD-positivity was much more frequent than WT1 reactivity, apparently proportional to that of the proper RCC cellularity and facilitated by extensive RCC inflammatory infiltration. TDs exhibited nuclear reactivity for most TME cell lines, while RCC TME WT1 expression was rare and inconsistent. In HRTs, TDs were entirely restricted to renal tubular cells, the likely cellular progenitor of most conventional RCC subtypes. In lieu of proper validation, these early findings have significant implications regarding the origins/biology of RCCs and may inform RCC therapeutics, both accounting for the high frequency of immunotherapy-permissive frameshift indels in RCCs, but also hinting at novel predictive clinical tools for WT1-targeted immunotherapy. Overall, the current study represents a meek yet hopefully significant step towards understanding the molecular biology and potential therapeutic targets of RCCs.

Glass Capillary-Based Nanopores for Single Molecule/Single Cell Detection

A glass capillary-based nanopore (G-nanopore), due to its tapered tip, easy tunability in orifice size, and especially its flexible surface modifications that can be tailored to effectively capture and enhance the ionic current signal of single entities (single molecules, single cells, and single particles), offers a powerful and nanoconfined sensing platform for diverse biological measurements of single cells and single molecules. Compared with other artificial two-dimensional solid-state nanopores, its conical tip and high spatial and temporal resolution characteristics facilitate noninvasive single molecule and selected area (subcellular) single cell detections (e.g., DNA mutations, highly expressed proteins, and small molecule markers that reflect the change characteristics of the tumor), as a small G-nanopore (≤100 nm) does negligible damage to cell functions and cell membrane integrity when inserted through the cell membrane. In this brief review, we summarize the preparation of G-nanopores and discuss the advantages of them as solid-state sensing platforms for single molecule and single cell detection applications as well as for cancer diagnosis and treatment applications. We also describe the current bottlenecks that limit the widespread use of G-nanopores in clinical applications and provide an outlook on future developments. The brief review will provide the reader with a quick survey of this field and facilitate the rapid development of a G-nanopore sensing platform for future tumor diagnosis and personalized medicine based on single-molecule/single-cell bioassay.

Extrarenal Wilms tumor with hypertension and dilated cardiomyopathy in an infant: A report of an unusual case

While Wilms tumors are the most frequently detected kidney cancer type in children, extrarenal Wilms tumors (ERWTs) remain rare. This report is the first to describe hypertension and dilated cardiomyopathy in a patient with an ERWT. A 6-month-old male infant presented with an abdominal mass and paroxysmal hypertension; echocardiography revealed dilated cardiomyopathy with an ejection fraction of 34%, as well as substantially increased plasma renin activity. Pathology yielded a definitive diagnosis of ERWT. Cardiac function and blood pressure gradually returned to normal after tumorectomy. The early diagnosis of such a tumor together with efficient oncologic treatment are vital to optimal patient outcomes.

Evaluating Established Roles, Future Perspectives and Methodological Heterogeneity for Wilms’ Tumor 1 (WT1) Antigen Detection in Adult Renal Cell Carcinoma, Using a Novel N-Terminus Targeted Antibody (Clone WT49)

Renal cell carcinoma (RCC) is arguably the deadliest form of genitourinary malignancy and is nowadays viewed as a heterogeneous series of cancers, with the same origin but fundamentally different metabolisms and clinical behaviors. Immunohistochemistry (IHC) is increasingly necessary for RCC subtyping and definitive diagnosis. WT1 is a complex gene involved in carcinogenesis. To address reporting heterogeneity and WT1 IHC standardization, we used a recent N-terminus targeted monoclonal antibody (clone WT49) to evaluate WT1 protein expression in 56 adult RCC (aRCC) cases. This is the largest WT1 IHC investigation focusing exclusively on aRCCs and the first report on clone WT49 staining in aRCCs. We found seven (12.5%) positive cases, all clear cell RCCs, showing exclusively nuclear staining for WT1. We did not disregard cytoplasmic staining in any of the negative cases. Extratumoral fibroblasts, connecting tubules and intratumoral endothelial cells showed the same exclusively nuclear WT1 staining pattern. We reviewed WT1 expression patterns in aRCCs and the possible explanatory underlying metabolomics. For now, WT1 protein expression in aRCCs is insufficiently investigated, with significant discrepancies in the little data reported. Emerging WT1-targeted RCC immunotherapy will require adequate case selection and sustained efforts to standardize the quantification of tumor-associated antigens for aRCC and its many subtypes.

WT1 and Cyclin D1 Immunohistochemistry: A Useful Adjunct for Diagnosis of Pediatric Small Round Blue Cell Tumors on Small Biopsies

Pediatric small round blue cell tumors (SRBCTs) are a heterogeneous group of neoplasms with overlapping morphological appearance. Accordingly, their diagnosis is one of the most difficult in the field of surgical pathology. The most common tumors include rhabdomyosarcoma, Ewing’s sarcoma, neuroblastoma, lymphoblastic lymphoma and Wilms’ tumor (the blastemal component). Over time their diagnosis has become more difficult due to the increasing use of small biopsies. However, the advent of immunohistochemistry has improved the quality of diagnosis in most cases by the application of an adequate panel of immunomarkers. Recently, WT1 and Cyclin D1 have been shown to be useful in the differential diagnosis of SRBCTs on surgically-resected specimens, showing a diffuse cytoplasmic positivity of the former in all RMSs and a diffuse nuclear staining of the latter in both EWS and NB. The aim of the present study was to investigate the expression of WT1 and Cyclin D1 on small biopsies from a series of 105 pediatric SRBCTs to evaluate their diagnostic utility. Both immunomarkers were differentially expressed, with a diffuse and strong cytoplasmic staining for WT1 limited to all cases of RMS, and a diffuse nuclear staining for cyclin D1 restricted to all cases of EWS and NB. Notably, the expression of WT1 and cyclin D1 was also retained in those cases in which the conventional tumor markers (myogenin, desmin and MyoD1 for RMS; CD99 for EWS; NB84 for NB) were focally expressed or more rarely absent. The present study shows that WT1 and Cyclin D1 are helpful immunomarkers exploitable in the differential diagnosis of pediatric SRBCTs on small biopsies, suggesting their applicability in routine practice.

Identification of key carcinogenic genes in Wilms' tumor

This study aimed to probe carcinogenic genes and pathways associated with Wilms' tumor (WT) onset and malignancy progression. After screening, three datasets acquired from the Gene Expression Omnibus database were analyzed. Differentially expressed genes (DEGs) were identified and GO functional enrichment, KEGG pathway enrichment and protein-protein interaction (PPI) were analyzed. The DEGs with top fold change values or top protein interaction scores were used to analyze overall survival based on the TARGET WT dataset. Together, 866 up-regulated genes in GDS1791, 585 up-regulated genes in GDS2010, and 277 down-regulated genes in GDS4802 were found, from which 46 key DEGs were selected for further analysis. In the PPI network, hub positions included COL5A1, COL4A1, ARPP21, SPARCL1, CD86, LY96 and PPP1R12B. The top DEGs (ARPP21, SYNPO, PRRC2B, PPP1R12B, EFCAB2 and LY96) were selected for survival analysis, and they consistently showed a significantly positive correlation with poor survival. Together, five key carcinogenic genes (SYNPO, PRRC2B, PPP1R12B, EFCAB2 and LY96) were highly associated with WT onset and patient survival. These risk genes, interaction networks and enrichments should improve our understanding of the complex molecular mechanisms in WT development and help clinical applications.

Ovarian Cancer Immunotherapy and Personalized Medicine

Ovarian cancer response to immunotherapy is limited; however, the evaluation of sensitive/resistant target treatment subpopulations based on stratification by tumor biomarkers may improve the predictiveness of response to immunotherapy. These markers include tumor mutation burden, PD-L1, tumor-infiltrating lymphocytes, homologous recombination deficiency, and neoantigen intratumoral heterogeneity. Future directions in the treatment of ovarian cancer include the utilization of these biomarkers to select ideal candidates. This paper reviews the role of immunotherapy in ovarian cancer as well as novel therapeutics and study designs involving tumor biomarkers that increase the likelihood of success with immunotherapy in ovarian cancer.

Desmoplastic Small Round Cell Tumor with "Pure" Spindle Cell Morphology and Novel EWS-WT1 Fusion Transcript: Expanding the Morphological and Molecular Spectrum of This Rare Entity

Background: Desmoplastic small round cell tumor (DSRCT) is a rare pediatric soft tissue neoplasm composed of small round tumor cells with prominent stromal desmoplasia, polyphenotypic differentiation and EWSR1-WT1 gene fusion. We, herein, present a unique case of DSRCT, exhibiting a pure spindle cell morphology, absence of desmoplastic stroma and showing a novel EWS-WT1 fusion transcript. Methods: A 12-year-old boy presented multiple intra-abdominal, confluent and mass-forming nodules that affected the entire abdominal and pelvic cavities. Results: Histologically, the nodules were composed of spindle cells with scant cytoplasm and oval nuclei arranged into short, intersecting fascicles and set in a scant, non-desmoplastic, stroma. Immunohistochemically, neoplastic cells were stained with vimentin, desmin, WT-1 (C-terminus antibodies) and EMA. Reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed the presence of an unusual chimeric transcript, composed of an in-frame junction of exon 9 of EWS to exon 7 of WT1, confirming the histological diagnosis of DSRCT. Conclusions: The present case contributes to widen the morphological spectrum of this entity; notably, the additional presence of a novel chimeric fusion transcript contributes to making the present case even more unique. Whether the detection of the above-mentioned fusion transcripts could explain the unusual morphology of the tumor remains to be established.

Wilms’ tumor 1 protein expression in embryonal and alveolar rhabdomyosarcoma and its association with clinical prognostic factors: a cross-sectional study

BACKGROUND Embryonal rhabdomyosarcoma (ERMS) and alveolar rhabdomyosarcoma (ARMS) are the two major histological types commonly found in the pediatric population, which have different morphology and genetic profile. Wilms’ tumor 1 (WT1) is an antigen highly expressed in solid tumors, including rhabdomyosarcoma, and a potential immunotherapy target. Only a few studies have attempted to determine WT1 expression in rhabdomyosarcoma. This study was conducted to demonstrate WT1 expression in ERMS, ARMS and associate it with established prognostic factors. METHODS A cross-sectional study was conducted at the Department of Anatomical Pathology, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo Hospital, Jakarta using archival data from January 2011 to December 2017. 30 from 102 ERMS cases and 16 from 28 ARMS cases were included in this study. Data of age, tumor size, and location were collected. All cases were stained by WT1 immunohistochemistry. The expression was assessed semiquantitatively using histoscore (H-score) formula. An independent t-test was used to compare WT1 expression between ERMS and ARMS. Correlation analysis was used to evaluate the relationship between WT1 expression and prognostic factors. RESULTS All ERMS and ARMS cases expressed WT1 in diffuse, moderate to strong staining. ERMS show higher WT1 expression than ARMS (H-score 179.9 versus 149.5) (p = 0.014). Strong WT1 expression mostly found in patient age <20 years and non favourable location. Moderate WT1 expression mostly found in cases with tumor size >5 cm. CONCLUSIONS WT1 expression was higher in ERMS cases than in ARMS cases, which the expressions were similar in different age, tumor size, and location groups.

Renal Tumors of Childhood-A Histopathologic Pattern-Based Diagnostic Approach

Renal tumors comprise approximately 7% of all malignant pediatric tumors. This is a highly heterogeneous group of tumors, each with its own therapeutic management, outcome, and association with germline predispositions. Histopathology is the key in establishing the correct diagnosis, and therefore pathologists with expertise in pediatric oncology are needed for dealing with these rare tumors. While each tumor shows different histologic features, they do have considerable overlap in cell type and histologic pattern, making the diagnosis difficult to establish, if based on routine histology alone. To this end, ancillary techniques, such as immunohistochemistry and molecular analysis, can be of great importance for the correct diagnosis, resulting in appropriate treatment. To use ancillary techniques cost-effectively, we propose a pattern-based approach and provide recommendations to aid in deciding which panel of antibodies, supplemented by molecular characterization of a subset of genes, are required.

Immunohistochemical Expression of Wilms’ Tumor 1 Protein in Human Tissues: From Ontogenesis to Neoplastic Tissues

The human Wilms’ tumor gene (WT1) was originally isolated in a Wilms’ tumor of the kidney as a tumor suppressor gene. Numerous isoforms of WT1, by combination of alternative translational start sites, alternative RNA splicing and RNA editing, have been well documented. During human ontogenesis, according to the antibodies used, anti-C or N-terminus WT1 protein, nuclear expression can be frequently obtained in numerous tissues, including metanephric and mesonephric glomeruli, and mesothelial and sub-mesothelial cells, while cytoplasmic staining is usually found in developing smooth and skeletal cells, myocardium, glial cells, neuroblasts, adrenal cortical cells and the endothelial cells of blood vessels. WT1 has been originally described as a tumor suppressor gene in renal Wilms’ tumor, but more recent studies emphasized its potential oncogenic role in several neoplasia with a variable immunostaining pattern that can be exclusively nuclear, cytoplasmic or both, according to the antibodies used (anti-C or N-terminus WT1 protein). With the present review we focus on the immunohistochemical expression of WT1 in some tumors, emphasizing its potential diagnostic role and usefulness in differential diagnosis. In addition, we analyze the WT1 protein expression profile in human embryonal/fetal tissues in order to suggest a possible role in the development of organs and tissues and to establish whether expression in some tumors replicates that observed during the development of tissues from which these tumors arise.

Screening and identification of non-inflammatory specific protein markers in Wilms' tumor tissues

Wilms' tumor is one of the most common malignancies in children, and early diagnosis is critical for its subsequent treatment and prognosis. Our previous study employed proteomics to investigate protein markers in the serum of Wilms' tumor children. The present study aimed to identify specific protein markers in Wilms' tumor. Proteomic comparison of Wilms' tumor with normal kidney tissues and the sera of systemic inflammatory response syndrome (SIRS) controls was performed. Surface-enhanced laser desorption ionization time-of-flight (SELDI-TOF-MS) identified a protein with m/z 8350 as specific to Wilms' tumor. The target protein was purified using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and identified as profilin-1 by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF). Its expression was validated using real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Our data identify profilin-1 as a potential protein marker for Wilms' tumor and demonstrate the feasibility of the above procedures for screening and identification of tumor-specific protein markers.

HnRNPL promotes Wilms tumor progression by regulating the p53 and Bcl2 pathways

Background: Wilms tumor (WT) is the most common renal tumor in children with diffusely anaplastic or unfavorable histology, indicative of a poor prognosis. Heterogeneous nuclear ribonucleoprotein L (hnRNPL) is an RNA-binding protein (RBP) and a regulator of alternative RNA splicing that plays an important role in the occurrence and development of several cancers. Methods: Next generation sequencing technologies was used to discovery differentially expressed genes between WT and adjacent nontumors. The gene ontology (GO) analysis was performed to uncover the biological functions of differentially expressed genes, and the kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis was applied to find out the related signal pathways. Expression levelsof hnRNPL with WT tissues and cells were determined by RT-qPCR.After silencing hnRNPL, the expression of hnRNPL, p53 and Bcl-2 were detected by RT-qPCR and Western blot in WT cell line. The regulatory effects of hnRNPLon proliferative and apoptotic potentials of WT cells were evaluated by MTT and flow cytometry, respectively. RNA-binding protein immuno-precipitation was used to confirm the direct interaction of hnRNPL with p53 mRNA. Mouse xenograft models ofhnRNPL knockdown were established to test the functions in the growth of WT in vivo. Results: High levels of hnRNPL were expressed in WT tissues and cells. Functional analysis revealed that hnRNPL silencing suppressed cell proliferation and promoted cell apoptosis in WT. Molecular mechanism exploration indicated that hnRNPL directly targeted p53. Moreover, knockdown of hnRNPL inhibited the expression of p53 and Bcl2 in WT. Additionally, hnRNPL silencing inhibited the growth of xenograft tumors in vivo. Conclusion: HnRNPL act as p53 mRNA-binding protein, which plays an important role in the proliferation and apoptosis of WT through p53 and Bcl2 pathways and these findings provide new insights into the mechanism of WT pathogenesis.

Validation of Immunohistochemical Assays for Integral Biomarkers in the NCI-MATCH EAY131 Clinical Trial

Biomarkers that guide therapy selection are gaining unprecedented importance as targeted therapy options increase in scope and complexity. In conjunction with high-throughput molecular techniques, therapy-guiding biomarker assays based upon immunohistochemistry (IHC) have a critical role in cancer care in that they inform about the expression status of a protein target. Here, we describe the validation procedures for four clinical IHC biomarker assays-PTEN, RB, MLH1, and MSH2-for use as integral biomarkers in the nationwide NCI-Molecular Analysis for Therapy Choice (NCI-MATCH) EAY131 clinical trial. Validation procedures were developed through an iterative process based on collective experience and adaptation of broad guidelines from the FDA. The steps included primary antibody selection; assay optimization; development of assay interpretation criteria incorporating biological considerations; and expected staining patterns, including indeterminate results, orthogonal validation, and tissue validation. Following assay lockdown, patient samples and cell lines were used for analytic and clinical validation. The assays were then approved as laboratory-developed tests and used for clinical trial decisions for treatment selection. Calculations of sensitivity and specificity were undertaken using various definitions of gold-standard references, and external validation was required for the PTEN IHC assay. In conclusion, validation of IHC biomarker assays critical for guiding therapy in clinical trials is feasible using comprehensive preanalytic, analytic, and postanalytic steps. Implementation of standardized guidelines provides a useful framework for validating IHC biomarker assays that allow for reproducibility across institutions for routine clinical use. Clin Cancer Res; 24(3); 521-31. ©2017 AACR.

Expression profile of Wilms Tumor 1 (WT1) isoforms in undifferentiated and all-trans retinoic acid differentiated neuroblastoma cells

Wilms tumor 1 gene (WT1) is a tumor suppressor gene originally identified in nephroblastoma. It is also expressed in neuroblastoma which represents the most aggressive extracranial pediatric tumor. Many evidences have shown that neuroblastoma may undergo maturation, by transforming itself in a more differentiated tumors such as ganglioneuroblastoma and ganglioneuroma, or progressing into a highly aggressive metastatic malignancy. To date, 13 WT1 mRNA alternative splice variants have been identified. However, most of the studies have focused their attention only on isoform of ∼49 kDa. In the present study, it has been investigated the expression pattern of WT1 isoforms in an in vitro model of neuroblastoma consisting in undifferentiated or all-trans retinoic acid (RA) differentiated cells. These latter representing the less malignant phenotype of this tumor. Results have demonstrated that WT1.1-WT1.5, WT1.6-WT1.9, WT1.10 WT1.11-WT1.12 and WT1.13 isoforms are expressed in both groups of cells, but their levels are significantly increased after RA treatment. These data have also been confirmed by immunofluorescence analysis. Moreover, the inhibition of PI3K/Akt and MAPK/ERK, that represent two signalling pathway specifically involved in NB differentiation, induces an overexpression of WT1 isoforms. These data suggest that WT1 isoforms might be involved in differentiation of neuroblastic into mature ganglion cells.

Immunohistochemical Markers of Soft Tissue Tumors: Pathologic Diagnosis, Genetic Contributions, and Therapeutic Options

After ~30 years of widespread usage, immunohistochemistry (IHC) has become a standard method of diagnosis for surgical pathology. Because of the plethora of diagnoses and often subtle nature of diagnostic criteria, IHC finds particular utility in soft tissue tumors. The use of progressively small amounts of tissue for diagnosis highlights the importance of this method. The sensitivity and crispness of IHC stains have progressively improved with the advent of new techniques. Traditionally, IHC detects cell-typic markers that characterize cell phenotypes, such as chromogranin for neuroectodermal tissue, myogenin for skeletal muscle, and cytokeratin for epithelium. However, the advent of genetic discoveries have led to IHC testing for detection of fusion gene products or overexpressed oncogenes associated with deletions and mutations. Proliferation-based markers such as Ki-67 can also be used for prognosis and grading, but more standardization is needed. Development of monoclonal antibody-based pharmaceuticals, such as imatinib or crizotinib, holds the promise of tailored anticancer therapy. IHC thus has assumed importance not only for diagnosis but also for guidance of personalized medicine.

WT1 expression is inversely correlated with MYCN amplification or expression and associated with poor survival in non-MYCN-amplified neuroblastoma

Neuroblastoma (NB) is the most common extra cranial solid tumor in childhood and the most frequently diagnosed neoplasm during infancy. A striking feature of this tumor is its clinical heterogeneity. Several tumor progression markers have been delineated so far, among which MYCN amplification, which occurs in about 25% of total NB cases, with the percentage increasing to 30% in advanced stage NB. Although MYCN amplification is strongly correlated with NB of poor outcome, the MYCN status cannot alone predict all cases of poor survival in NB. Indeed NB without MYCN amplification (about 70-80% of NB) are not always favorable. WT1 was initially identified as a tumor suppressor gene involved in the development of a pediatric renal tumor (Wilms' tumor). Here, we describe an inverse correlation between WT1 expression and MYCN amplification and expression. However and most notably, our results show that WT1 gene expression is associated with a poor outcome for patients showing non-MYCN-amplified tumors. Thus WT1 expression is clinically significant in NB and may be a prognostic marker for better risk stratification and for an optimized therapeutic management of NB.

Immunohistochemistry as potential diagnostic pitfall in the most common solid tumors of children and adolescents

Making a correct diagnosis when dealing with a small round blue cell tumor (SRBCT) of children and adolescents may be relatively straightforward if the tumor arises in the typical clinical setting and the classic pathologic features are all recognizable. However it is widely known that diagnostic difficulties may arise because of: (i) many tumors share overlapping morphological and/or immunohistochemical features; (ii) considerable clinical, pathologic, and immunohistochemical variations do exist; (iii) the increasing use of small biopsies in daily practice makes the diagnosis of these neoplasms more challenging. Accordingly, immunohistochemical analyses are currently mandatory in establishing the correct diagnosis. In this regard there is the need to identify more sensitive and specific immunomarkers useful in the distinction of the several tumor entities. Over the last decades, several markers, such as CD99, WT1 protein, desmin, myogenin, NB84, and INI1 have been identified, providing a considerable help in recognition of the most common solid tumors (ESW/pPNET, rhabdomyosarcoma, neuroblastoma, Wilms' tumor, desmoplastic small round cell tumor; malignant rhabdoid tumor) in children and adolescents. However, at the same time, their unusual, unexpected expression can result in a misinterpretation of the immunohistochemical results, especially by pathologists who are not familiar with oncologic pediatric pathology. Therefore the present review focuses on the potential immunohistochemical pitfalls which should be kept in mind by pathologists to prevent diagnostic errors when dealing with SRBCTs.

Wilms' tumor 1 (WT1) protein expression in human developing tissues

Several genes playing crucial roles in human development often reproduce a key role also during the onset and progression of malignant tumors. WT1, a transcription factor expressed with a dynamic pattern during human development, has either oncogenic or suppressor tumor properties. A detailed analysis of the immunohistochemical profile of WT1 protein in human developmental tissues could be exploitable as the rational for better understanding its role in cancerogenesis and planning innovative WT1-based therapeutic approaches. This review focuses on the dynamic immunohistochemical expression and distribution of WT1 protein during human ontogenesis, providing illustrations and discussion on the most relevant findings. The possibility that WT1 nuclear/cytoplasmic expression in some tumors mirrors its normal developmental regulation will be emphasized.

Oncofetal expression of Wilms' tumor 1 (WT1) protein in human fetal, adult and neoplastic skeletal muscle tissues

There is increasing evidence that WT1 protein expression is found not only at nuclear, but also at cytoplasmic, level in several developing and neoplastic tissues. In order to better understand the possible role of WT1 protein in human skeletal myogenesis and oncogenesis of rhabdomyosarcoma, we assessed immunohistochemically its comparative expression in a large series of human developing, adult and neoplastic skeletal muscle tissues. The present study shows that WT1 protein is developmentally expressed in the cytoplasm of human myoblasts from the 6 weeks of gestational age. This expression was maintained in the myotubes of developing muscles of the trunk, head, neck, and extremities, while it was down-regulated in fetal skeletal fibers from 20 weeks of gestational age as well as in adult normal skeletal muscle. Notably, WT1 immunostaining disappeared from rhabdomyomas, whereas it was strongly and diffusely re-expressed in all cases (27/27) of embryonal and alveolar rhabdomyosarcoma. The comparative evaluation of the immunohistochemical findings revealed that WT1 cytoplasmic expression in rhabdomyosarcoma may represent an ontogenetic reversal, and this nuclear transcription factor can also be considered an oncofetal protein which can be exploitable as an additional, highly sensitive immunomarker, together with desmin, myogenin and MyoD1, of this tumor. Moreover, our observations support the rationale for the use of WT1 protein-based target therapy in high risk rhabdomyosarcomas in children and adolescents.