Physical and functional interaction between WT1 and p53 proteins

Upregulation of HOXA3 by isoform-specific Wilms tumour 1 drives chemotherapy resistance in acute myeloid leukaemia

Upregulation of the Wilms' tumour 1 (WT1) gene is common in acute myeloid leukaemia (AML) and is associated with poor prognosis. WT1 generates 12 primary transcripts through different translation initiation sites and alternative splicing. The short WT1 transcripts express abundantly in primary leukaemia samples. We observed that overexpression of short WT1 transcripts lacking exon 5 with and without the KTS motif (sWT1+/- and sWT1-/-) led to reduced cell growth. However, only sWT1+/- overexpression resulted in decreased CD71 expression, G1 arrest, and cytarabine resistance. Primary AML patient cells with low CD71 expression exhibit resistance to cytarabine, suggesting that CD71 may serve as a potential biomarker for chemotherapy. RNAseq differential expressed gene analysis identified two transcription factors, HOXA3 and GATA2, that are specifically upregulated in sWT1+/- cells, whereas CDKN1A is upregulated in sWT1-/- cells. Overexpression of either HOXA3 or GATA2 reproduced the effects of sWT1+/-, including decreased cell growth, G1 arrest, reduced CD71 expression and cytarabine resistance. HOXA3 expression correlates with chemotherapy response and overall survival in NPM1 mutation-negative leukaemia specimens. Overexpression of HOXA3 leads to drug resistance against a broad spectrum of chemotherapeutic agents. Our results suggest that WT1 regulates cell proliferation and drug sensitivity in an isoform-specific manner.

The RNA-binding protein KSRP aggravates malignant progression of clear cell renal cell carcinoma through transcriptional inhibition and post-transcriptional destabilization of the NEDD4L ubiquitin ligase

BACKGROUND

KH-type splicing regulatory protein (KHSRP, also called KSRP), a versatile RNA-binding protein, plays a critical role in various physiological and pathological conditions through modulating gene expressions at multiple levels. However, the role of KSRP in clear cell renal cell carcinoma (ccRCC) remains poorly understood.

METHODS

KSRP expression was detected by a ccRCC tissue microarray and evaluated by an in silico analysis. Cell loss-of-function and gain-of-function, colony-formation, anoikis, and transwell assays, and an orthotopic bioluminescent xenograft model were conducted to determine the functional role of KRSP in ccRCC progression. Micro (mi)RNA and complementary (c)DNA microarrays were used to identify downstream targets of KSRP. Western blotting, quantitative real-time polymerase chain reaction, and promoter- and 3-untranslated region (3'UTR)-luciferase reporter assays were employed to validate the underlying mechanisms of KSRP which aggravate progression of ccRCC.

RESULTS

Our results showed that dysregulated high levels of KSRP were correlated with advanced clinical stages, larger tumor sizes, recurrence, and poor prognoses of ccRCC. Neural precursor cell-expressed developmentally downregulated 4 like (NEDD4L) was identified as a novel target of KSRP, which can reverse the protumorigenic and prometastatic characteristics as well as epithelial-mesenchymal transition (EMT) promotion by KSRP in vitro and in vivo. Molecular studies revealed that KSRP can decrease NEDD4L messenger (m)RNA stability via inducing mir-629-5p upregulation and directly targeting the AU-rich elements (AREs) of the 3'UTR. Moreover, KSRP was shown to transcriptionally suppress NEDD4L via inducing the transcriptional repressor, Wilm's tumor 1 (WT1). In the clinic, ccRCC samples revealed a positive correlation between KSRP and mesenchymal-related genes, and patients expressing high KSRP and low NEDD4L had the worst prognoses.

CONCLUSION

The current findings unveil novel mechanisms of KSRP which promote malignant progression of ccRCC through transcriptional inhibition and post-transcriptional destabilization of NEDD4L transcripts. Targeting KSRP and its pathways may be a novel pharmaceutical intervention for ccRCC.

WT1: The Hinge Between Anemia Correction and Cancer Development in Chronic Kidney Disease

Hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHIs) emerge as promising agents to treat anemia in chronic kidney disease (CKD) but the major concern is their correlated risk of cancer development and progression. The Wilms’ tumor gene, WT1, is transcriptionally regulated by HIF and is known to play a crucial role in tumorigenesis and invasiveness of certain types of cancers. From the mechanism of action of HIF–PHIs, to cancer hypoxia and the biological significance of WT1, this review will discuss the link between HIF, WT1, anemia correction, and cancer. We aimed to reveal the research gaps and offer a focused strategy to monitor the development and progression of specific types of cancer when using HIF–PHIs to treat anemia in CKD patients. In addition, to facilitate the long-term use of HIF–PHIs in anemic CKD patients, we will discuss the strategy of WT1 inhibition to reduce the development and progression of cancer.

Acquired WT1 mutations contribute to relapse of NPM1-mutated acute myeloid leukemia following allogeneic hematopoietic stem cell transplant

The role of WT1 protein in hematopoiesis and leukemogenesisis incompletely elucidated. WT1 overexpression is common in acute myeloid leukemia (AML); however, WT1 mutations occur in only about 10% of cases, with increasing incidence in the setting of relapse. In this study, we investigated the clinical and molecular characteristics of WT1 mutations in NPM1-mutated AML, to enhance our understanding of the biology and potential therapeutic implications of WT1 mutations. Our study cohort included 67 patients with NPM1 mutated AML and a median follow-up of 13.7 months. WT1 mutations were identified in 7% (n = 5) of patients at the time of initial diagnosis. WT1 mutant clones were presumed to be present as co-dominant clones in 3/5 and in subclonal populations in 2/5 cases based on variant allelic frequency (VAF) when compared with NPM1 mutation VAF. All WT1 mutations became undetectable at time of MRD-negative (NPM1-wild type) remission. None of these patients experienced relapse at the time of last follow-up (median, 15 months; range, 4.5-20.2 months). A total of 15/67 (22%) patients relapsed; among these patient, four (27%) relapsed with WT1 mutant AML. Three of four patients had undergone allogeneic hematopoietic stem cell transplantation (HSCT). None of these patients had detectable WT1 mutations at the time of initial diagnosis. WT1 mutations were presumed clonal in two cases and subclonal in the other two cases, based on VAF. Our results indicate that WT1 mutations contribute to relapse in NPM1 mutated AML, especially in the setting of HSCT. These findings suggest that emerging WT1 mutations may serve as a conduit for relapse in NPM1-mutated AML, and that sequential molecular profiling to evaluate potential emergent WT1 mutations during surveillance and particularly at relapse likely has prognostic value in patients with NPM1 mutated AML.

Barriers to Immunotherapy in Ovarian Cancer: Metabolic, Genomic, and Immune Perturbations in the Tumour Microenvironment

A lack of explicit early clinical signs and effective screening measures mean that ovarian cancer (OC) often presents as advanced, incurable disease. While conventional treatment combines maximal cytoreductive surgery and platinum-based chemotherapy, patients frequently develop chemoresistance and disease recurrence. The clinical application of immune checkpoint blockade (ICB) aims to restore anti-cancer T-cell function in the tumour microenvironment (TME). Disappointingly, even though tumour infiltrating lymphocytes are associated with superior survival in OC, ICB has offered limited therapeutic benefits. Herein, we discuss specific TME features that prevent ICB from reaching its full potential, focussing in particular on the challenges created by immune, genomic and metabolic alterations. We explore both recent and current therapeutic strategies aiming to overcome these hurdles, including the synergistic effect of combination treatments with immune-based strategies and review the status quo of current clinical trials aiming to maximise the success of immunotherapy in OC.

Truncated WT1 Protein Isoform Expression Is Increased in MCF-7 Cells with Long-Term Estrogen Depletion

Background

The wt1 gene codes for a transcription factor that presents several protein isoforms with diverse biological properties, capable of positively and negatively regulating genes involved in proliferation, differentiation, and apoptosis. WT1 protein is overexpressed in more than 90% of breast cancer; however, its role during tumor progression is still unknown. Methodology. In this work, we analyzed the expression of WT1 isoforms in several breast cancer cells with different tumor marker statuses and an in vitro assay using MCF-7 cells cultured with long-term estrogen depletion (MCF-7 LTED cells) with the finality to mimic the process of switching from hormone-dependent to hormone-independent. Moreover, growth kinetics, sensitivity to tamoxifen, and relative expression analysis of ER and Her2/neu were performed.

Results

Initially, the expression of 52-54 kDa protein isoform of WT1 in the breast cancer cell line ER (+) was detected by western blot and was absent in ER (-), and the 36-38 kDa protein isoform of WT1 was detected in all cell lines analyzed. The analysis of alternative splicing by RT-PCR shows that the 17AA (+)/KTS (-) isoform of WT1 was the most frequent in the four cell lines analyzed. In vitro, the MCF-7 cells in the estrogen depletion assay show an increase in the expression of the 52-54 kDa isoform of WT1 in the first 48 hours, and this was maintained until week 13, and later, this expression was decreased, and the 36-38 kDa isoform of WT1 did not show change during the first 48 hours but from week 1 showed an increase of expression, and this remained until week 27. Growth kinetic analysis showed that MCF-7 LTED cells presented a 1.4-fold decrease in cellular proliferation compared to MCF-7 cells cultured under normal conditions. In addition, MCF-7 LTED cells showed a decrease in sensitivity to the antiproliferative effect of tamoxifen (p ≤ 0.05). Samples collected until week 57 analyzed by qRT-PCR showed an increase in the relative expression of the Her2/neu and ER.

Conclusions

Modulation of protein isoforms showed differential expression of WT1 isoforms dependent on estrogen receptor. The absence of 52-54 kDa and the presence of the 36-38 kDa protein isoform of WT1 were detected in ER-negative breast cancer cell lines classified as advanced stage cells. Long-term estrogen depletion assay in MCF-7 cells increased the expression of the 36-38 kDa isoform and reduced the 52-54 kDa isoform, and these cells show an increase in the expression of tumor markers of ER and Her2/neu. MCF-7 LTED cells showed low proliferation and insensitivity to tamoxifen compared to MCF-7 cells in normal conditions. These results support the theory about the relationship of the 36-38 kDa isoform of WT1 and the absence of ER function in advanced breast cancer.

CMIP interacts with WT1 and targets it on the proteasome degradation pathway

BACKGROUND

The Wilms tumor 1 suppressor gene, WT1, is expressed throughout life in podocytes and is essential for their function. Downregulation of WT1 has been reported in podocyte diseases but the underlying mechanisms remain unclear. Podocyte injury is the hallmark of idiopathic nephrotic syndrome (INS), the most frequent glomerular disease in children and young adults. An increase in the abundance of Cmaf-inducing protein (CMIP) has been found to alter podocyte function, but it is not known whether CMIP affects WT1 expression.

METHODS

Transcriptional and post-transcriptional regulation of WT1in the presence of CMIP was studied using transient transfection, mouse models, and siRNA handling.

RESULTS

We showed that overproduction of CMIP in the podocyte was consistently associated with a downregulation of WT1 according to two mechanisms. We found that CMIP prevented the NF-kB-mediated transcriptional activation of WT1. We demonstrated that CMIP interacts directly with WT1 through its leucine-rich repeat domain. Overexpression of CMIP in the M15 cell line induced a downregulation of WT1, which was prevented by lactacystin, a potent proteasome inhibitor. We showed that CMIP exhibits an E3 ligase activity and targets WT1 to proteasome degradation. Intravenous injection of Cmip-siRNA specifically prevented the repression of Wt1 in lipopolysaccharides-induced proteinuria in mice.

CONCLUSIONS

These data suggest that CMIP is a repressor of WT1 and might be a critical player in the pathophysiology of some podocyte diseases. Because WT1 is required for podocyte integrity, CMIP could be considered a therapeutic target in podocyte diseases.

Podocyte apoptosis in diabetic nephropathy by BASP1 activation of the p53 pathway via WT1

AIMS

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. BASP1 (brain acid-soluble protein) is up-regulated in podocyte-specific protein phosphatase 2A knockout mice (Pod-PP2A-KO) that develop kidney dysfunction. Here, we explore the role of BASP1 for podocytes in DN.

METHODS

BASP1 was assessed in kidneys from DN patients and DN mouse models, podocyte specific BASP1 knockout mice (Pod-BASP1-KO mice) were generated and studied in vivo. Furthermore, podocyte injury and apoptosis were measured after BASP1 knockdown and overexpression in a mouse podocyte cell line (MPC5). Potential signalling pathways involved in podocyte apoptosis were detected.

RESULTS

BASP1 expression was up-regulated in DN patients compared to normal controls. BASP1 specific deletion in podocytes protected against podocyte injury by reducing the loss of expression of slit diaphragm molecules and foot process effacement in the DN model. BASP1 promoted actin cytoskeleton rearrangements and apoptosis in the MPC5 podocyte line. Molecules involved in the p53 pathway were down-regulated in BASP1 knockdown podocytes treated with high glucose compared to controls. BASP1 promoted podocyte apoptosis and P53 pathway activation through co-repression with Wilms' tumour 1 transcription factor (WT1).

CONCLUSION

BASP1 activates the p53 pathway through modulation of WT1 to induce podocyte apoptosis in diabetic nephropathy.

Tumor suppression by the EGR1, DMP1, ARF, p53, and PTEN Network

Recent studies have indicated that EGR1 is a direct regulator of tumor suppressors including TGFβ1, PTEN, and p53. The Myb-like transcription factor Dmp1 is a physiological regulator of the Arf-p53 pathway through transactivation of the Arf promoter and physical interaction of p53. The Dmp1 promoter has binding sites for Egr proteins, and Egr1 is a target for Dmp1. Crosstalks between p53 and PTEN have been reported. The Egr1-Dmp1-Arf-p53-Pten pathway displays multiple modes of interaction with each other, suggesting the existence of a functional network of tumor suppressors that maintain normal cell growth and prevent the emergence of incipient cancer cells.

Development of mesenteric tissues

Mesothelial, neurovascular, lymphatic, adipose and mesenchymal tissues make up the mesentery. These tissues are pathobiologically important for numerous reasons. Collectively, they form a continuous, discrete and substantive organ. Additionally, they maintain abdominal digestive organs in position and in continuity with other systems. Furthermore, as they occupy a central position, they mediate transmission of signals between the abdominal digestive system and the remainder of the body. Despite this physiologic centrality, mesenteric tissue development has received little investigatory focus. However, recent advances in our understanding of anatomy demonstrate continuity between all mesenteric tissues, thereby linking previously unrelated studies. In this review, we examine the development of mesenteric tissue in normality and in the setting of congenital abnormalities.

Transcription factors WT1 and p53 combined: a prognostic biomarker in ovarian cancer

Background

New approaches to ovarian cancer are needed to improve survival. Wilms’ tumour 1 (WT1) is a tumour-associated antigen expressed in many ovarian cancers. P53 is also often altered. The clinical significance of the combined expression of these two transcription factors has not been studied.

Methods

One hundred ninety-six ovarian tumours were classified histopathologically. Tumours were stained for WT1 and p53 immunohistochemically. Stains were analysed according to tumour type, grade and FIGO stage. Kaplan–Meier analyses on 96 invasive carcinomas determined whether categorical variables were related to survival.

Results

WT1 and p53 were related to ovarian tumour type, grade, FIGO stage and patient survival. Uniform nuclear p53 expression was associated with invasion and WT1 expression was associated with advanced grade, FIGO stage and poor survival. When WT1 and p53 were both in the age-adjusted Cox model, WT1 was significant while p53 was not. When we combined tumours expressing WT1 and p53, then adjusted for age and tumour subtype, the hazard ratio compared to tumours without WT1 and with normal p53 was 2.70; when adjusted for age and FIGO stage, the hazard ratio was 2.40.

Conclusions

WT1, an antigen target, is a biomarker for poor prognosis, particularly when combined with altered p53.

Aberrant expression of ETS1 and ETS2 proteins in cancer

The ETS transcription factors regulate expression of genes involved in normal cell development, proliferation, differentiation, angiogenesis, and apoptosis, consisting of 28 family members in humans. Dysregulation of these transcription factors facilitates cell proliferation in cancers, and several members participate in invasion and metastasis by activating gene transcription. ETS1 and ETS2 are the founding members of the ETS family and regulate transcription by binding to ETS sequences. They are both involved in oncogenesis and tumor suppression depending on the biological situations used. The essential roles of ETS proteins in human telomere maintenance have been suggested, which have been linked to creation of new Ets binding sites. Recently, preferential binding of ETS2 to gain-of-function mutant p53 and ETS1 to wild type p53 (WTp53) has been suggested, raising the tumor promoting role for the former and tumor suppressive role for the latter. The oncogenic and tumor suppressive functions of ETS1 and 2 proteins have been discussed.

Wilms Tumor 1b defines a wound-specific sheath cell subpopulation associated with notochord repair

Regenerative therapy for degenerative spine disorders requires the identification of cells that can slow down and possibly reverse degenerative processes. Here, we identify an unanticipated wound-specific notochord sheath cell subpopulation that expresses Wilms Tumor (WT) 1b following injury in zebrafish. We show that localized damage leads to Wt1b expression in sheath cells, and that wt1b⁺cells migrate into the wound to form a stopper-like structure, likely to maintain structural integrity. Wt1b⁺sheath cells are distinct in expressing cartilage and vacuolar genes, and in repressing a Wt1b-p53 transcriptional programme. At the wound, wt1b⁺and entpd5⁺ cells constitute separate, tightly-associated subpopulations. Surprisingly, wt1b expression at the site of injury is maintained even into adult stages in developing vertebrae, which form in an untypical manner via a cartilage intermediate. Given that notochord cells are retained in adult intervertebral discs, the identification of novel subpopulations may have important implications for regenerative spine disorder treatments.

WT1 loss attenuates the TP53-induced DNA damage response in T-cell acute lymphoblastic leukemia

Loss-of-function mutations and deletions in Wilms tumor 1 (WT1) gene are present in approximately 10% of T-cell acute lymphoblastic leukemia. Clinically, WT1 mutations are enriched in relapsed series and are associated to inferior relapse-free survival in thymic T-cell acute lymphoblastic leukemia cases. Here we demonstrate that WT1 plays a critical role in the response to DNA damage in T-cell leukemia. WT1 loss conferred resistance to DNA damaging agents and attenuated the transcriptional activation of important apoptotic regulators downstream of TP53 in TP53-competent MOLT4 T-leukemia cells but not in TP53-mutant T-cell acute lymphoblastic leukemia cell lines. Notably, WT1 loss positively affected the expression of the X-linked inhibitor of apoptosis protein, XIAP, and genetic or chemical inhibition with embelin (a XIAP inhibitor) significantly restored sensitivity to γ-radiation in both T-cell acute lymphoblastic leukemia cell lines and patient-derived xenografts. These results reveal an important role for the WT1 tumor suppressor gene in the response to DNA damage, and support the view that anti-XIAP targeted therapies could have a role in the treatment of WT1-mutant T-cell leukemia.

Wilms tumor 1 mutations in the pathogenesis of acute myeloid leukemia

Wilms tumor 1 (WT1) has long been implicated in acute myeloid leukemia. It has been described to be both overexpressed and mutated in different forms of acute myeloid leukemia, and overexpression has been reported to play a prognostic role in this disease. However, the precise mechanism through which WT1 may play a role in leukemogenesis has remained elusive. In recent years, new evidence has emerged that points towards a novel role of WT1 mutations in the deregulation of epigenetic programs in leukemic cells through its interaction with TET proteins. Herein we review the current status of the field and its therapeutic and prognostic implications in acute myeloid leukemia.

Wilms' tumor gene 1 silencing inhibits proliferation of human osteosarcoma MG-63 cell line by cell cycle arrest and apoptosis activation

Wilms' tumor gene 1 (WT1) plays complex roles in tumorigenesis, acting as tumor suppressor gene or an oncogene depending on the cellular context. A high WT1 expression level was described in various types of human bone and soft-tissue sarcomas, including osteosarcoma (OS), but its function in carcinogenesis is not yet well understood. This study investigated WT1 both in human OS tissues and in human OS MG-63 cell line in which WT1 gene is up-regulated. The results demonstrated that WT1 is expressed in 50% of human OS cases. WT1-silenced MG-63 cells showed deregulation of proteins of cell cycle and down-regulation of PI3K/AKT pathway. Induction of apoptotic programme was also established by activation of caspase-3 and increase of Bax/Bcl2 ratio and p53 protein. This study provided new findings on role of WT1 and indicated an association between WT1 expression, cell cycle and apoptotic machinery. In conclusion, WT1 acts as a tumour promoter in osteosarcoma and it could be a potential therapeutic target.

Role for Egr1 in the Transcriptional Program Associated with Neuronal Differentiation of PC12 Cells

PC12 cells are a well-established model to study how differences in signal transduction duration can elicit distinct cell behaviors. Epidermal growth factor (EGF) activates transient ERK signaling in PC12 cells that lasts 30–60 min, which in turn promotes proliferation; nerve growth factor (NGF) activates more sustained ERK signaling that lasts 4–6 h, which in turns induces neuronal differentiation. Data presented here extend a previous study by Mullenbrock et al. (2011) that demonstrated that sustained ERK signaling in response to NGF induces preferential expression of a 69-member gene set compared to transient ERK signaling in response to EGF and that the transcription factors AP-1 and CREB play a major role in the preferential expression of several genes within the set. Here, we examined whether the Egr family of transcription factors also contributes to the preferential expression of the gene set in response to NGF. Our data demonstrate that NGF causes transient induction of all Egr family member transcripts, but a corresponding induction of protein was detected for only Egr1 and 2. Chromatin immunoprecipitation experiments provided clearest evidence that, after induction, Egr1 binds 12 of the 69 genes that are preferentially expressed during sustained ERK signaling. In addition, Egr1 expression and binding upstream of its target genes were both sustained in response to NGF versus EGF within the same timeframe that its targets are preferentially expressed. These data thus provide evidence that Egr1 contributes to the transcriptional program activated by sustained ERK signaling in response to NGF, specifically by contributing to the preferential expression of its target genes identified here.

The small molecule 2-phenylethynesulfonamide induces covalent modification of p53

p53 is a tumor suppressor protein which is either lost or inactivated in a large majority of tumors. The small molecule 2-phenylethynesulfonamide (PES) was originally identified as the inhibitor of p53 effects on the mitochondrial death pathway. In this report we demonstrate that p53 protein from PES-treated cells was detected in reduced mobility bands between molecular weights 95-220 kDa. Resolution of p53 aggregates on urea gel was unable to reduce the high molecular weight p53 aggregates, which were shown to be primarily located in the nucleus. Therefore, our data suggest that PES exerts its effects through covalent cross-linking and nuclear retention of p53.

In Vitro Transcription to Study WT1 Function

In vitro transcription methods using mammalian nuclear extracts have been available for over 30 years and have allowed sophisticated biochemical analyses of the transcription process. This method has been extensively used to study the basic mechanisms of transcription, allowing the identification of the general transcription factors and elucidation of their mechanisms of action. Gene-specific transcriptional regulators have also been studied using in vitro transcription. This has facilitated the identification of their cofactors and provided information on their function that is invaluable to facilitate their study in a more physiological setting. Here we describe the application of in vitro transcription methods to study the mechanism of action of WT1. Coupling transcription assays with methods to purify transcription complexes, and protein affinity chromatography, has provided insights into how WT1 can both positively and negatively regulate transcription.

WT1 Mutation in Childhood Cancer

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

Wilms' tumor gene 1 regulates p63 and promotes cell proliferation in squamous cell carcinoma of the head and neck

Background

Wilms’ tumor gene 1 (WT1) can act as a suppressor or activator of tumourigenesis in different types of human malignancies. The role of WT1 in squamous cell carcinoma of the head and neck (SCCHN) is not clear. Overexpression of WT1 has been reported in SCCHN, suggesting a possible oncogenic role for WT1. In the present study we aimed at investigating the function of WT1 and its previously identified protein partners p63 and p53 in the SCCHN cell line FaDu.

Methods

Silencing RNA (siRNA) technology was applied to knockdown of WT1, p63 and p53 in FaDu cells. Cell proliferation was detected using MTT assay. Chromatin immunoprecipitation (ChIP)/PCR analysis was performed to confirm the effect of WT1 on the p63 promoter. Protein co-immunoprecipitation (co-IP) was used to find protein interaction between WT1 and p53/p63. Microarray analysis was used to identify changes of gene expression in response to knockdown of either WT1 or p63. WT1 RNA level was detected using real-time quantitative PCR (RT-qPCR) in patients with SCCHN.

Results

We found that WT1 and p63 promoted cell proliferation, while mutant p53 (R248L) possessed the ability to suppress cell proliferation. We reported a novel positive correlation between WT1 and p63 expression. Subsequently, p63 was identified as a WT1 target gene. Furthermore, expression of 18 genes involved in cell proliferation, cell cycle regulation and DNA replication was significantly altered by downregulation of WT1 and p63 expression. Several known WT1 and p63 target genes were affected by WT1 knockdown. Protein interaction was demonstrated between WT1 and p53 but not between WT1 and p63. Additionally, high WT1 mRNA levels were detected in SCCHN patient samples.

Conclusions

Our findings suggest that WT1 and p63 act as oncogenes in SCCHN, affecting multiple genes involved in cancer cell growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1356-0) contains supplementary material, which is available to authorized users.

WT1 recruits TET2 to regulate its target gene expression and suppress leukemia cell proliferation

The TET2 DNA dioxygenase regulates cell identity and suppresses tumorigenesis by modulating DNA methylation and expression of a large number of genes. How TET2, like most other chromatin-modifying enzymes, is recruited to specific genomic sites is unknown. Here we report that WT1, a sequence-specific transcription factor, is mutated in a mutually exclusive manner with TET2, IDH1, and IDH2 in acute myeloid leukemia (AML). WT1 physically interacts with and recruits TET2 to its target genes to activate their expression. The interaction between WT1 and TET2 is disrupted by multiple AML-derived TET2 mutations. TET2 suppresses leukemia cell proliferation and colony formation in a manner dependent on WT1. These results provide a mechanism for targeting TET2 to a specific DNA sequence in the genome. Our results also provide an explanation for the mutual exclusivity of WT1 and TET2 mutations in AML, and suggest an IDH1/2-TET2-WT1 pathway in suppressing AML.

Mechanisms of transcriptional regulation by WT1 (Wilms' tumour 1)

The WT1 (Wilms' tumour 1) gene encodes a zinc finger transcription factor and RNA-binding protein that direct the development of several organs and tissues. WT1 manifests both tumour suppressor and oncogenic activities, but the reasons behind these opposing functions are still not clear. As a transcriptional regulator, WT1 can either activate or repress numerous target genes resulting in disparate biological effects such as growth, differentiation and apoptosis. The complex nature of WT1 is exemplified by a plethora of isoforms, post-translational modifications and multiple binding partners. How WT1 achieves specificity to regulate a large number of target genes involved in diverse physiological processes is the focus of the present review. We discuss the wealth of the growing molecular information that defines our current understanding of the versatility and utility of WT1 as a master regulator of organ development, a tumour suppressor and an oncogene.

Wilms' tumor gene 1 immunotherapy in pelvic gynecological malignancies

Pelvic gynecological malignancies account for 6% of all cancers. In the relapsed state, classical treatments are limited. There is an urgent need for new and personalized treatment. Wilms' tumor gene 1 (WT1) is the most important tumor-associated antigen. Although highly present in gynecological tumors, active immunotherapy against it is still underexplored. This review gives an insight into the importance of WT1 in pelvic gynecological malignancies and the first taken steps into the world of WT1 immunotherapy.

A novel cell-penetrating peptide derived from WT1 enhances p53 activity, induces cell senescence and displays antimelanoma activity in xeno- and syngeneic systems

The Wilms tumor protein 1 (WT1) transcription factor has been associated in malignant melanoma with cell survival and metastasis, thus emerging as a candidate for targeted therapy. A lysine-arginine rich peptide, WT1-pTj, derived from the ZF domain of WT1 was evaluated as an antitumor agent against A2058 human melanoma cells and B16F10-Nex2 syngeneic murine melanoma. Peptide WT1-pTj quickly penetrated human melanoma cells and induced senescence, recognized by increased SA-β-galactosidase activity, enhanced transcriptional activity of p53, and induction of the cell cycle inhibitors p21 and p27. Moreover, the peptide bound to p53 and competed with WT1 protein for binding to p53. WT1-pTj treatment led to sustained cell growth suppression, abrogation of clonogenicity and G2/M cell cycle arrest. Notably, in vivo studies showed that WT1-pTj inhibited both the metastases and subcutaneous growth of murine melanoma in syngeneic mice, and prolonged the survival of nude mice challenged with human melanoma cells. The 27-amino acid cell-penetrating WT1-derived peptide, depends on C(3) and H(16) for effective antimelanoma activity, inhibits proliferation of WT1-expressing human tumor cell lines, and may have an effective role in the treatment of WT1-expressing malignancies.

Wilms' tumor gene 1 enhances nutlin-3-induced apoptosis

Nutlin-3, a human double minute 2 (HDM2) antagonist, induces cell cycle arrest or apoptosis by upregulating p53 in cancer cells. WT1, the product of Wilms' tumor gene 1, has been shown to interact with p53, but the effect of WT1 on nutlin-3-induced apoptosis has yet to be examined. To address this issue, we analyzed the inhibitory effect of nutlin-3 on cell growth as a function of Wt1 expression status using a Wt1-inducible U2OS cell line. In the absence of Wt1 expression, nutlin-3 induced cell cycle arrest with marginal cytotoxicity. Furthermore, upon Wt1 expression, nutlin-3 exerted a marked degree of cell death, as evidenced by the accumulation of hypo-diploid cells and LDH release. During cell death induction, cytochrome c was released into the cytosol, and caspase-9 and -3 were activated, suggesting that an intrinsic apoptotic pathway may be involved in this cell death. Consistent with this, z-VAD-Fmk, a pan-caspase inhibitor and the overexpression of BCL-XL attenuated the cell death. Nutlin-3 caused an increase in the mRNA levels of both BCL-XL and BAK, as well as their corresponding protein levels in mitochondria. In the presence of Wt1, nutlin-3-induced BCL-XL expression was attenuated while the expression of nutlin-3-induced BAK was potentiated. Collectively, these results suggest that WT1 potentiates nutlin-3-induced apoptosis by downregulating the expression of BCL-XL while upregulating that of BAK, which leads to the activation of an intrinsic apoptotic pathway.

The involvement of WT1 in the regulation of GADD45a in response to genotoxic stress

Expression of the human GADD45a gene is increased in TK6 cells exposed to mutagens, clastogens and aneugens. It is known to be regulated through both p53-dependent and p53-independent pathways and WT1 has been implicated in both cases. This article reports an investigation into the effect that mutations in the WT1 and p53 response elements of the gene have on GADD45a expression. This was conducted in both p53 wild-type (TK6) and mutant (WI-L2-NS) human B lymphoblastoid cell lines. Gene expression was monitored using a GADD45a-green fluorescent protein reporter assay. Mutant cell lines were exposed to the mechanistically diverse genotoxins methyl methanesulphonate, cisplatin and mitomycin C (direct acting), hydroxyurea, aphidicolin and 5'fluorouracil (inhibitors of nucleotide/DNA synthesis) and benomyl (aneugen). In all cases, the induction of the reporter was reduced in the mutants compared with wild-type. These results provide experimental evidence for the implied role of WT1 in both p53-dependent and p53-independent pathways of GADD45a regulation and further insight into the mechanism of GADD45a induction by genotoxins.

The WTX tumor suppressor enhances p53 acetylation by CBP/p300

WTX encodes a tumor suppressor, frequently inactivated in Wilms tumor, with both plasma membrane and nuclear localization. WTX has been implicated in β-catenin turnover, but its effect on nuclear proteins is unknown. We report an interaction between WTX and p53, derived from the unexpected observation of WTX, p53, and E1B 55K colocalization within the characteristic cytoplasmic body of adenovirus-transformed kidney cells. In other cells without adenovirus expression, the C-terminal domain of WTX binds to the DNA-binding domain of p53, enhances its binding to CBP, and increases CBP/p300-mediated acetylation of p53 at Lys 373/382. WTX knockdown accelerates CBP/p300 protein turnover and attenuates this modification of p53. In p53-reconstitution experiments, cell-cycle arrest, apoptosis, and p53 target-gene expression are suppressed by depletion of WTX. Together, these results suggest that WTX modulates p53 function, in part through regulation of its activator CBP/p300.

Trimming of mammalian transcriptional networks using network component analysis

Background

Network Component Analysis (NCA) has been used to deduce the activities of transcription factors (TFs) from gene expression data and the TF-gene binding relationship. However, the TF-gene interaction varies in different environmental conditions and tissues, but such information is rarely available and cannot be predicted simply by motif analysis. Thus, it is beneficial to identify key TF-gene interactions under the experimental condition based on transcriptome data. Such information would be useful in identifying key regulatory pathways and gene markers of TFs in further studies.

Results

We developed an algorithm to trim network connectivity such that the important regulatory interactions between the TFs and the genes were retained and the regulatory signals were deduced. Theoretical studies demonstrated that the regulatory signals were accurately reconstructed even in the case where only three independent transcriptome datasets were available. At least 80% of the main target genes were correctly predicted in the extreme condition of high noise level and small number of datasets. Our algorithm was tested with transcriptome data taken from mice under rapamycin treatment. The initial network topology from the literature contains 70 TFs, 778 genes, and 1423 edges between the TFs and genes. Our method retained 1074 edges (i.e. 75% of the original edge number) and identified 17 TFs as being significantly perturbed under the experimental condition. Twelve of these TFs are involved in MAPK signaling or myeloid leukemia pathways defined in the KEGG database, or are known to physically interact with each other. Additionally, four of these TFs, which are Hif1a, Cebpb, Nfkb1, and Atf1, are known targets of rapamycin. Furthermore, the trimmed network was able to predict Eno1 as an important target of Hif1a; this key interaction could not be detected without trimming the regulatory network.

Conclusions

The advantage of our new algorithm, relative to the original NCA, is that our algorithm can identify the important TF-gene interactions. Identifying the important TF-gene interactions is crucial for understanding the roles of pleiotropic global regulators, such as p53. Also, our algorithm has been developed to overcome NCA's inability to analyze large networks where multiple TFs regulate a single gene. Thus, our algorithm extends the applicability of NCA to the realm of mammalian regulatory network analysis.

Candidate genes and potential targets for therapeutics in Wilms' tumour

Wilms' tumour (WT) is the most common malignant renal tumour of childhood. During the past two decades or so, molecular studies carried out on biopsy specimens and tumour-derived cell lines have identified a multitude of chromosomal and epigenetic alterations in WT. In addition, a significant amount of evidence has been gathered to identify the genes and signalling pathways that play a defining role in its genesis, growth, survival and treatment responsiveness. As such, these molecules and mechanisms constitute potential targets for novel therapeutic strategies for refractory WT. In this report we aim to review some of the many candidate genes and intersecting pathways that underlie the complexities of WT biology.

Wilms' tumour 1 can suppress hTERT gene expression and telomerase activity in clear cell renal cell carcinoma via multiple pathways

Background:

Wilms' tumour 1 (WT1) gene was discovered as a tumour suppressor gene. Later findings have suggested that WT1 also can be oncogenic. This complexity is partly explained by the fact that WT1 has a number of target genes.

Method:

WT1 and its target gene human telomerase reverse transcriptase (hTERT) were analysed in clear cell renal cell carcinoma (ccRCC). In vitro experiments were performed to examine the functional link between WT1 and hTERT by overexpression of WT1 isoforms in the ccRCC cell line, TK-10.

Results:

WT1 demonstrated lower RNA expression in ccRCC compared with renal cortical tissue, whereas hTERT was increased, showing a negative correlation between WT1 and hTERT (P=0.005). These findings were experimentally confirmed in vitro. The WT1 generated effect on hTERT promoter activity seemed complex, as several negative regulators of hTERT transcription, such as SMAD3, JUN (AP-1) and ETS1, were activated by WT1 overexpression. Downregulation of potential positive hTERT regulators, such as cMyc, AP-2α, AP-2γ, IRF1, NFX1 and GM-CSF, were also observed. Chromatin immunoprecipitation analysis verified WT1 binding to the hTERT, cMyc and SMAD3 promoters.

Conclusion:

The collected data strongly indicate multiple pathways for hTERT regulation by WT1 in ccRCC.

The Wilms' tumour suppressor protein WT1 acts as a key transcriptional repressor of the human thromboxane A2 receptor gene in megakaryocytes

In humans, the TPalpha and TPbeta isoforms of the thromboxane A2 receptor are transcriptionally regulated by distinct promoters, designated Prm1 and Prm3. Previous investigations identified two upstream repressor regions (URR) 1 and URR2 within Prm1. Herein, it was sought to characterize Prm1, identifying the factor(s) regulating URR1 and URR2 in human erythroleukaemia (HEL) 92.1.7 cells. Genetic reporter assays and 5' deletions confirmed the presence of URR1 and URR2 but also identified a third repressor, designated RR3, within the proximal 'core' promoter. Bioinformatic analysis revealed several GC elements representing putative sites for Egr1/Sp1/Wilms tumour (WT)1 within URR1, URR2 and RR3. While mutation of three GC elements within URR1 and of an adjacent GC element suggested that repressor binding occurs through a cooperative mechanism, repressors binding to the single GC elements within URR2 and RR3 act independently to regulate Prm1. While electrophoretic mobility shift assays and supershift assays demonstrated that each of the GC elements can bind Egr1 and WT1 in vitro, chromatin immunoprecipitations established that WT1 is the factor predominantly bound to each of the repressor regions in vivo. Additionally, ectopic expression of -KTS isoforms of WT1 decreased Prm1-directed gene expression and TPalpha mRNA expression. Collectively, these data establish WT1 as a critical repressor of Prm1, suppressing TPalpha expression in the platelet progenitor megakaryoblastic HEL cells.

Regulation of p53--insights into a complex process

The p53 protein is one of the most important tumor suppressor proteins. Normally, the p53 protein is in a latent state. However, when its activity is required, e.g. upon DNA damage, nucleotide depletion or hypoxia, p53 becomes rapidly activated and initiates transcription of pro-apoptotic and cell cycle arrest-inducing target genes. The activity of p53 is regulated both by protein abundance and by post-translational modifications of pre-existing p53 molecules. In the 30 years of p53 research, a plethora of modifications and interaction partners that modulate p53's abundance and activity have been identified and new ones are continuously discovered. This review will summarize our current knowledge on the regulation of p53 abundance and activity.

Contribution of individual amino acids to the RNA binding activity of the Wilms' tumor suppressor protein WT1

In addition to binding to DNA, the zinc finger protein WT1 can also bind specifically to RNA. To determine the role of individual zinc fingers of the protein in this RNA binding activity, deletion and substitution mutants of the WT1 zinc finger domain were constructed. The effects of the various mutations on the binding of WT1 to the RNA aptamers RNA22 and RNA38 were determined using a quantitative equilibrium binding assay. The results indicate that zinc fingers 2 and 3 of WT1 are essential for the binding of the protein to the RNA aptamers. For both of these fingers, the arginine residue immediately preceding the alpha-helix makes a significant contribution to RNA binding. For zinc finger 2, a second arginine residue within the alpha-helix is also critical for RNA binding, while several alpha-helical residues in zinc finger 3 contribute to the overall affinity of WT1 for RNA. Investigating the effects of the same point mutations on DNA binding indicates that there are similarities and differences in the contributions of zinc fingers 2 and 3 to the DNA and RNA binding activities of WT1.

No evidence for WT1 involvement in a beta-catenin-independent activation of the Wnt signaling pathway in pituitary adenomas

The overexpression of Wilms' tumor gene product WT1, which acts as a tumor suppressor or oncogene, has been reported in various malignancies. Recent studies have shown that the interaction partner Wnt-4 is upregulated in pituitary adenomas dependent on the Pit-1 lineage (somatotrophs, lactotrophs, and thyrotrophs). However, no data on WT1 expression in nontumorous pituitary tissue or pituitary adenomas is available to date. We investigated WT1 expression in 90 paraffin-embedded pituitary adenomas, including eight atypical adenomas, and in 28 nontumorous pituitary glands by immunohistochemistry. WT1 is absent in epithelial cells of all nontumorous pituitary glands and in 87 out of 90 pituitary adenomas. Only two GHomas (including one atypical adenoma) and one gonadotropin-producing adenoma expressed WT1 in the cytoplasm of single tumor cells without nuclear staining. There is no evidence that WT1 does regulate the Wnt-4/beta-catenin-independent pathway which is activated in the Pit-1-expressing subset of pituitary adenomas.

WT1 induction of mitogen-activated protein kinase phosphatase 3 represents a novel mechanism of growth suppression

In its role as a tumor suppressor, WT1 transactivates several genes that are regulators of cell growth and differentiation pathways. For instance, WT1 induces the expression of the cell cycle regulator p21, the growth-regulating glycoprotein amphiregulin, the proapoptotic gene Bak, and the Ras/mitogen-activated protein kinase (MAPK) inhibitor Sprouty1. Here, we show that WT1 transactivates another important negative regulator of the Ras/MAPK pathway, MAPK phosphatase 3 (MKP3). In a WT1-inducible cell line that exhibits decreased cell growth and increased apoptosis on expression of WT1, microarray analysis showed that MKP3 is the most highly induced gene. This was confirmed by real-time PCR where MKP3 and other members of the fibroblast growth factor 8 syn expression group, which includes Sprouty 1 and the Ets family of transcription factors, were induced rapidly following WT1 expression. WT1 induction was associated with a block in the phosphorylation of extracellular signal-regulated kinase in response to epidermal growth factor stimulation, an effect mediated by MKP3. In the presence of a dominant-negative MKP3, WT1 could no longer block phosphorylation of extracellular signal-regulated kinase. Lastly, when MKP3 expression is down-regulated by short hairpin RNA, WT1 is less able to block Ras-mediated transformation of 3T3 cells.

In silico regulatory analysis for exploring human disease progression

Background

An important goal in bioinformatics is to unravel the network of transcription factors (TFs) and their targets. This is important in the human genome, where many TFs are involved in disease progression. Here, classification methods are applied to identify new targets for 152 transcriptional regulators using publicly-available targets as training examples. Three types of sequence information are used: composition, conservation, and overrepresentation.

Results

Starting with 8817 TF-target interactions we predict an additional 9333 targets for 152 TFs. Randomized classifiers make few predictions (~2/18660) indicating that our predictions for many TFs are significantly enriched for true targets. An enrichment score is calculated and used to filter new predictions.

Two case-studies for the TFs OCT4 and WT1 illustrate the usefulness of our predictions:

• Many predicted OCT4 targets fall into the Wnt-pathway. This is consistent with known biology as OCT4 is developmentally related and Wnt pathway plays a role in early development.

• Beginning with 15 known targets, 354 predictions are made for WT1. WT1 has a role in formation of Wilms' tumor. Chromosomal regions previously implicated in Wilms' tumor by cytological evidence are statistically enriched in predicted WT1 targets. These findings may shed light on Wilms' tumor progression, suggesting that the tumor progresses either by loss of WT1 or by loss of regions harbouring its targets.

• Targets of WT1 are statistically enriched for cancer related functions including metastasis and apoptosis. Among new targets are BAX and PDE4B, which may help mediate the established anti-apoptotic effects of WT1.

• Of the thirteen TFs found which co-regulate genes with WT1 (p ≤ 0.02), 8 have been previously implicated in cancer. The regulatory-network for WT1 targets in genomic regions relevant to Wilms' tumor is provided.

Conclusion

We have assembled a set of features for the targets of human TFs and used them to develop classifiers for the determination of new regulatory targets. Many predicted targets are consistent with the known biology of their regulators, and new targets for the Wilms' tumor regulator, WT1, are proposed. We speculate that Wilms' tumor development is mediated by chromosomal rearrangements in the location of WT1 targets.

Reviewers

This article was reviewed by Trey Ideker, Vladimir A. Kuznetsov(nominated by Frank Eisenhaber), and Tzachi Pilpel.

Diagnostic value of WT1 in neuroepithelial tumours

AIMS

Currently, clinical trials using WT1 (Wilms tumour gene) peptide vaccines are conducted in haematopoietic malignancies and solid cancers. Single reports showed that the Wilms tumour gene product WT1 is also expressed in astrocytic neoplasms. Our aim was to investigate WT1 expression in a large cohort of various neuroepithelial tumours of different World Health Organization (WHO) grades and in normal central nervous system (CNS) tissue specimens to test its potential value as a diagnostic marker.

METHODS

Specimens were assessed by RT-PCR, Western blotting and immunohistochemistry. The samples investigated in our study consisted of 334 human neuroepithelial tumours, among those 33 oligodendrogliomas, 219 astrocytomas (including 105 glioblastomas) and 47 ependymomas.

RESULTS

Our results showed a de novo WT1 expression in neuroepithelial tumours. In diffuse astrocytomas and ependymomas, WT1 expression increased significantly with the grade of malignancy. In contrast, no significant difference was seen between WHO grade-II and -III oligodendrogliomas. Controlling for WHO grade, the comparison of oligodendrogliomas with ependymal and astrocytic tumours showed higher expression values for the latter.

CONCLUSIONS

Our study shows that WT1 is expressed de novo in numerous neuroepithelial tumours and increases with the grade of malignancy. These results suggest an important role of WT1 in tumourigenesis and progression in human brain tumours.

The Wilms' tumor suppressor Wt1 activates transcription of the erythropoietin receptor in hematopoietic progenitor cells

The Wilms' tumor protein Wt1 is required for embryonic development and has been implicated in hematologic disorders. Since Wt1 deficiency may compromise the proliferation and differentiation of erythroid progenitor cells, we analyzed the possible role of the transcriptionally active Wt1 isoform, Wt1(-KTS), in regulating the expression of the erythropoietin receptor (EpoR). Wt1 and EpoR were coexpressed in CD117(+) hematopoietic progenitor cells and in several hematopoietic cell lines. CD117(+) cells of Wt1-deficient murine embryos (Wt1(-/-)) exhibited a significantly lower proliferation response to recombinant erythropoietin than CD117(+) cells of heterozygous (Wt1(+/-)) and wild-type littermates (Wt1(+/+)). EpoR expression was significantly diminished in hematopoietic progenitors (CD117(+)) that lacked Wt1, and the erythroid colony-forming capacity was reduced by more than 50% in fetal liver cells of Wt1-deficient embryonic mice. Wt1(-KTS) significantly increased endogenous EpoR transcripts in transfected cells. The proximal EpoR promoter of human and mouse was stimulated more than 10-fold by Wt1(-KTS) in transiently cotransfeced K562 erythroleukemia cells. A responsible cis-element, which is highly conserved in the EpoR promoter of human and mouse, was identified by mutation analysis, electrophoretic mobility shift assay, and chromatin immunoprecipitation assay. In conclusion, activation of the EpoR gene by Wt1 may represent an important mechanism in normal hematopoiesis.

WT1 expression distinguishes astrocytic tumor cells from normal and reactive astrocytes

Particularly in small brain biopsies, it might be difficult to distinguish reactive astrogliosis from low-grade or infiltration zones of high-grade astrocytomas. So far no immunohistochemical marker allows a reliable distinction. Recently, the over-expression of Wilms' tumor gene product WT1 was reported in astrocytic tumor cells. However, no sufficient data on WT1 expression in normal or reactive astrocytes are available. Therefore, we investigated WT1 expression in paraffin-embedded brain sections from 28 controls, 48 cases with astrogliosis of various etiology and 219 astrocytomas [World Health Organization (WHO) grades I-IV] by immunohistochemistry. In normal brains and in astrogliosis, expression of WT1 was restricted to endothelial cells. In astrocytomas, WT1-positive tumor cells were found in pilocytic astrocytomas (66.7% of cases), diffuse astrocytomas (52.7%) WHO grade II (52.7%), anaplastic astrocytomas (83.4%) and glioblastomas (98.1%). Overall, the majority of all astrocytic neoplasms (84.5%) expressed WT1. Establishing a cut-off value of 0% immunoreactive tumor cells served to recognize neoplastic astrocytes with 100% specificity and 68% sensitivity and was associated with positive and negative predictive values of 1 and 0.68, respectively. Therefore, WT1 expression in astrocytes indicates a neoplastic origin and might represent an important diagnostic tool to differentiate reactive from neoplastic astrocytes by immunohistochemistry.

Wilms tumor 1 expression in malignant gliomas and correlation of +KTS isoforms with p53 status

Object

The WT1 gene is overexpressed in many types of human cancer. It has been demonstrated that Wilms tumor 1 (WT1) promotes tumor cell proliferation and survival in some cell lines by inhibiting p53-mediated apoptosis; however, this relationship has not been investigated in gliomas. The goal in this study was to characterize the expression pattern of WT1 in human gliomas and to determine if a correlation exists between WT1 expression and p53 status.

Methods

The authors screened nine malignant glioma cell lines, 50 glioblastoma multiforme (GBM) samples, and 16 lower-grade glial tumors for WT1 expression.

Results

Five of nine cell lines, 44 of 50 GBM samples, and 13 of 16 lower-grade gliomas expressed WT1 mRNA on reverse transcriptase polymerase chain reaction (PCR) analysis. Expression of WT1 was not detected in normal astrocytes. Two WT1 isoforms, +/+ and −/+, were expressed in the majority of these samples. Real-time PCR analysis of the GBM cell lines revealed that the level of WT1 mRNA ranged from 6.33 to 214.70 ng per ng 18S ribosomal RNA. The authors screened the GBM samples for p53 mutation by using PCR and single-stranded conformational polymorphism analysis, and they demonstrated an association between WT1 expression and p53 status. Tumors that contained wild-type p53 were significantly more likely to express WT1 than tumors that contained mutant p53.

Conclusions

The presence of WT1 in glioma cell lines and the majority of primary tumor samples and its absence in normal astrocytes support the suggestion that WT1 expression is important in glioma biology.

Wilms tumor: progress and considerations for the surgeon

Wilms tumor (WT) or nephroblastoma is the most common tumor of renal origin found in children. It accounts for 6% of all pediatric tumors and is the second most frequent intrabdominal solid organ tumor found in children. Initial survival rates in the early part of the last century was only 30%, but now long-term survival in both North America and European trials is approaching 85% with many low-stage tumors significantly higher. Treatment is now progressing towards "risk-based management"- based not only on stage and histology but also incorporating genetic markers [Dome JS, Grundy PE, Perlman EJ, Ehrlich PF, et al. Protocols for the renal tumors study. Childrens Oncology Group. [www.childrensoncologygroup.org. 2007.]. Within the multidisciplinary treatment team the surgeon plays a critical role in the diagnosis, staging and the surgeon's technical skills and judgment directs therapy and impacts outcome. The next generation of treatment for children with WT will focus on identifying subsets of patients who can be defined by some criterion as having a different outcome than their similar stage peers and who therefore require a variation in management. These include children with WT that have unsatisfactory long-term survival (less then 75%), patients of good survival but high potential for late effects and a final challenge are those children with both a poor survival and a high potential for late effects. This article presents a review of the most recent treatment considerations for WT with a focus on the surgeon's role to ensure a good outcome.

Upregulation of Wilms’ tumour gene 1 (WT1) in uterine sarcomas

AIM

Overexpression of Wilms' tumour gene (WT1) has been proven in several tumours. Previous research of our group on the cell cycle of uterine leiomyosarcoma (LMS) and carcinosarcoma (CS) suggested a possible role for WT1. We therefore intended to further explore the expression pattern of WT1 in uterine sarcomas.

METHODS

27 CS, 38 LMS, 15 endometrial stromal sarcomas (ESS) and seven undifferentiated sarcomas (US) were collected. WT1 expression was evaluated by immunohistochemistry (IHC) in 87 samples, by RT-PCR (m-RNA expression) in 23 random selected samples and by Western blotting in 12 samples, separating cytoplasmic and nuclear proteins. A pilot study to detect mutations (exons 7-10) was performed on eight samples.

RESULTS

IHC showed WT1 positivity in 12/27 CS, 29/38 LMS, 7/15 ESS and 4/7 US. All-but-one sample had a positive RT-PCR. All Western blottings were positive with more cytoplasmic expression in 9/12 cases. No mutations were found.

CONCLUSIONS

WT1 is overexpressed in uterine sarcomas. Since increased levels of mRNA determine the biological role, WT1 might contribute to uterine sarcoma tumour biology.

Clinicopathological significance of WT1 expression in ovarian cancer: a possible accelerator of tumor progression in serous adenocarcinoma

Recently, oncogenic potential of the WT1 gene has been proposed in some human solid tumors and leukemias. Although previous studies have shown the frequent expression of the WT1 protein in ovarian serous adenocarcinomas (OSAs), its clinicopathologic significance is still unclear. We immunohistochemically examined the expression status of WT1 in 119 OSAs and analyzed the correlation of the intensity of WT1 immunoreactivity with the level of WT1 mRNA expression by quantitative real-time polymerase chain reaction, clinicopathologic variables, expression of p53, Bcl-2, and Ki-67 labeling index (LI). Of 119 OSAs, nuclear WT1 immunoreactivity was positive in 99 (83%), of which 44 (44%) and 55 (56%) exhibited high and low WT1 immunoreactivities, respectively. The quantitative WT1 mRNA levels were significantly correlated with the intensity of WT1 immunoreactivity (P < 0.05). In comparison with WT1-negative OSAs, the WT1-positive OSAs showed a higher grade (P = 0.007), advanced stage (P = 0.018), and higher Ki-67 LI (P < 0.001). Additionally, high WT1 immunoreactivity was correlated with a higher grade (P = 0.003), Ki-67 LI (P = 0.012), Bcl-2 expression (P = 0.003), and poorer patient outcome (5-year survival, 36.5 vs 63.8%, P = 0.008 by log-rank test). The WT1 protein may be an accelerator of the progression of OSA.

A tumor suppressor and oncogene: the WT1 story

The Wilms' tumor 1 (WT1) gene encodes a transcription factor important for normal cellular development and cell survival. The initial discovery of WT1 as the causative gene in an autosomal-recessive condition identified it as a tumor suppressor gene whose mutations are associated with urogenital disease and the development of kidney tumors. However, this view is not in keeping with the frequent finding of wild-type, full-length WT1 in human leukemia, breast cancer and several other cancers including the majority of Wilms' tumors. Rather, these observations suggest that in those conditions, WT1 has an oncogenic role in tumor formation. In this review, we explore the literature supporting both views of WT1 in human cancer and in particular human leukemias. To understand the mechanism by which WT1 can do this, we will also examine its functional activity as a transcription factor and the influence of protein partners on its dual behavior.

Posttranslational phosphorylation of mutant p53 protein in tumor development

p53 has been called the "cellular gatekeeper" and the "genome guard," because in response to exposure to DNA-damaging agents, it induces cell-cycle arrest in G1 or apoptosis and also directly affects DNA replication. Multiple mechanisms regulate p53 activity and posttranslational modification, including multisite phosphorylation of wild-type p53, in particular. Normal functions of wild-type p53 are abrogated by mutation of this gene, and oncogenic studies have revealed that p53 mutation is among the most common genetic alteration in human cancers. It is generally accepted that mutant p53 protein may not only lose the tumor suppressor functions of wild-type p53 but also acquire additional tumorigenetic roles, including dominant-negative effects and gain of function. Although many studies have revealed such aberrant functions of mutant p53, less is known about the posttranslational phosphorylation status of mutant p53 and novel biological functions of phosphorylation in carcinogenesis.

Isoforms of Wilms' tumor suppressor gene (WT1) have distinct effects on mammary epithelial cells

The role of WT1 (Wilm's tumor suppressor gene) in breast cancer is controversial, with evidence for both tumor-promoting and tumor-suppressing activities. In order to address this question, we expressed different WT1 isoforms in the mammary epithelial cell line H16N-2, which does not express endogenous WT1. Cells were stably transfected with either WT1 (-Ex5/-KTS) or WT1 (+Ex5/+KTS) under the control of the inducible metallothionein promoter. Induction of WT1 (-Ex5/-KTS) upregulated p21, causing a slowing of proliferation and a G2-phase cell cycle arrest. In artificial basement membrane, the WT1 (-Ex5/-KTS) isoform promoted the appearance of highly organized acinar cellular aggregates. In contrast, WT1 (+Ex5/+KTS) had no effect on p21 or proliferation, but rather caused an epithelial-mesenchymal transition and a redistribution of E-cadherin from the cell membrane to the cytoplasm. This isoform also causes the cellular aggregates growing in artificial basement membrane to appear significantly less organized than control cells. Thus, different WT1 isoforms have distinct effects in this cell line, suggesting that depending on the ratio of WT1 isoform expression in mammary epithelial cells, WT1 could function to either promote or suppress a transformed phenotype.