The role of WT1 in oncogenesis: tumor suppressor or oncogene?

Correlation of Wilms' Tumor 1 (WT1) with Oxidative Stress Markers and Expression of miR-361-5p; New Aspect of WT1 in Breast Cancer

Breast carcinoma is a heterogeneous disease that affects millions of women worldwide. Wilms' tumor 1 (WT1) is an oncogene that promotes proliferation, metastasis and reduces apoptosis. MicroRNAs (miR) are short noncoding RNAs with a major role in cancer metastasis. In present study, we investigated the association of serum level of WT1 with oxidative stress and expression of miR-361-5p in breast cancer. Serum samples of 45 patients and of 45 healthy women analyzed for protein level of WT1, malondialdehyde (MDA), total oxidant status (TOS), and total antioxidant capacity (TAC). Serum and tissue expression of miR-361-5p in 45 tumor tissues and 45 paired non-tumor adjacent tissues and 45 serum samples of patients and healthy women analyzed by qRT-PCR. Protein levels of WT1 not significantly difference in serum of patients compared to healthy controls. Serum levels of MDA and TOS in patients were higher, but TAC level was lower than healthy controls (p < 0.001). There was a positive correlation between WT1 with MDA and TOS, and a negative correlation between WT1 with TAC in patients. miR-361-5p expression in tumor tissues and serum of patients was lower than non-tumor adjacent tissues and serum of healthy controls, respectively (p < 0.001). Moreover, there was a negative correlation between miR-361-5p and WT1 in patients. The positive correlation between WT1 with MDA and TOS and negative correlation between TAC and miR-361-5p suggests that this gene can play an important role in worse prognoses in breast cancer. Additionally, miR-361-5p may serve as an invasive biomarker for early detection of breast cancer.

Application of Bioinformatics Analysis to Identify Important Pathways and Hub Genes in Ovarian Cancer Affected by WT1

Wilms tumor gene (WT1) is used as a marker for the diagnosis and prognosis of ovarian cancer. However, the molecular mechanisms involving WT1 in ovarian cancer require further study. Herein, we used bioinformatics and other methods to identify important pathways and hub genes in ovarian cancer affected by WT1. The results showed that WT1 is highly expressed in ovarian cancer and is closely related to the overall survival and progression-free survival (PFS) of ovarian cancer. In ovarian cancer cell line SKOV3, WT1 downregulation increased the mRNA expression of 638 genes and decreased the mRNA expression of 512 genes, which were enriched in the FoxO, AMPK, and the Hippo signaling pathways. The STRING online tool and Cytoscape software were used to construct a Protein-protein interaction (PPI) network and for Module analysis, and 18 differentially expressed genes (DEGs) were selected. Kaplan-Meier plotter analysis revealed that 16 of 18 genes were related to prognosis. Analysis of GEPIA datasets indicated that 7 of 16 genes were differentially expressed in ovarian cancer tissues and in normal tissues. The expression of IGFBP1 and FBN1 genes increased significantly after WT1 interference, while the expression of the SERPINA1 gene decreased significantly. The correlation between WT1 expression and that of these three genes was consistent with that of ovarian cancer tissues and normal tissues. According to the GeneMANIA online website analysis, there were complex interactions between WT1, IGFBP1, FBN1, SERPINA1, and 20 other genes. In conclusion, we have identified important signaling pathways involving WT1 that affect ovarian cancer, and distinguished three differentially expressed genes regulated by WT1 associated with the prognosis of ovarian cancer. Our findings provide evidence outlining mechanisms involving WT1 gene expression in ovarian cancer and provides a rational for novel treatment of ovarian cancer.

WT1 regulates HOXB9 gene expression in a bidirectional way

The homeoboxB9 (HOXB9) gene is necessary for specification of the anterior-posterior body axis during embryonic development and expressed in various types of cancer. Here we show that the Wilms tumor transcription factor WT1 regulates the HOXB9 gene in a bidirectional manner. Silencing of WT1 activates HOXB9 in Wt1 expressing renal cell adenocarcinoma-derived 786-0 cells, mesonephric M15 cells and ex vivo cultured murine embryonic kidneys. In contrast, HOXB9 expression in U2OS osteosarcoma and human embryonic kidney (HEK) 293 cells, which lack endogenous WT1, is enhanced by overexpression of WT1. Consistently, Hoxb9 promoter activity is stimulated by WT1 in transiently transfected U2OS and HEK293 cells, but inhibited in M15 cells with CRISPR/Cas9-mediated Wt1 deletion. Electrophoretic mobility shift assay and chromatin immunoprecipitation demonstrate binding of WT1 to the HOXB9 promoter in WT1-overexpressing U2OS cells and M15 cells. BASP1, a transcriptional co-repressor of WT1, is associated with the HOXB9 promoter in the chromatin of these cell lines. Co-transfection of U2OS and HEK293 cells with BASP1 plus WT1 prevents the stimulatory effect of WT1 on the HOXB9 promoter. Our findings identify HOXB9 as a novel downstream target gene of WT1. Depending on the endogenous expression of WT1, forced changes in WT1 can either stimulate or repress HOXB9, and the inhibitory effect of WT1 on transcription of HOXB9 involves BASP1. Consistent with inhibition of Hoxb9 expression by WT1, both transcripts are distributed in an almost non-overlapping pattern in embryonic mouse kidneys. Regulation of HOXB9 expression by WT1 might become relevant during kidney development and cancer progression.

Basal cell carcinomas of the scalp after radiotherapy for tinea capitis in childhood: A genetic and epigenetic study with comparison with basal cell carcinomas evolving in chronically sun-exposed areas

BACKGROUND

Basal cell carcinoma (BCC) has been mostly associated with sun exposure, but ionizing radiation is also a known risk factor. It is not clear if the pathogenesis of BCC, namely at a genomic and epigenetic level, differs according to the underlying triggering factors.

OBJECTIVE

The present study aims to compare genetic and epigenetic changes in BCCs related to ionizing radiation and chronic sun exposure.

METHODS

Tumor samples from BCCs of the scalp in patients submitted to radiotherapy to treat tinea capitis in childhood and BCCs from sun-exposed areas were analysed through array comparative genomic hybridization (array-CGH) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) to detect copy number alterations and methylation status of specific genes.

RESULTS

Genomic characterization of tumor samples revealed several copy number gains and losses in all chromosomes, with the most frequent gains observed at 2p, 6p, 12p, 14q, 15q, 18q, Xp and Yp, and the most frequent losses observed at 3q, 14q, 16p, 17q, 22q, Xp, Yp and Yq. We developed a statistical model, encompassing gains in 3p and 16p and losses in 14q and 20p, with potential to discriminate BCC samples with sporadic aetiology from BCC samples that evolve after radiotherapy in childhood for the treatment of tinea capitis, which presented statistical significance (P = 0.003). Few methylated genes were detected through MS-MLPA, most frequently RARB and CD44.

CONCLUSIONS

Our study represents a step forward in the understanding of the genetic mechanisms underlying the pathogenesis of BCC and suggests potential differences according to the underlying ris k factors.

Combinational immunotherapy based on immune checkpoints inhibitors in small cell lung cancer: is this the beginning to reverse the refractory situation?

Small cell lung cancer (SCLC), a particular neuroendocrine tumor, occupies 13% of lung cancers, with the highest mortality among cancers. Immune checkpoints inhibitors (ICIs) based on programmed cell death protein-1 (PD-1)/programmed cell death one ligand (PD-L1) inhibitors and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors have been one of the most favorable therapies in SCLC. Simultaneously, not all the patients respond to ICIs due to the lack of biomarkers to predict the immunotherapeutic effect. Multiple combinational approaches are under exploration, including the integrated or successive assessment of additional immunotherapeutic agents, chemotherapy, radiotherapy, and targeted therapy with ICIs. The current review offers a general view of the rationale for clinical studies exploring the experimental result of combinational immunotherapy based on ICIs, with both available results and ongoing trials. Moreover, the development of more predictive biomarkers, specific clinical trial designs, enhancement of the efficacy, and decreasing the financial toxicity will become the trend of future research and clinical applications of ICIs. Understanding the evolving immuno-oncology is increasingly relevant and crucial to solve those problems and define therapeutic strategies and potential target populations of combinational immunotherapy. Ultimately, emerging combinational immunotherapy will transform SCLC into a chronic disease to help patients survive from tumors.

WT1 activates transcription of the splice factor kinase SRPK1 gene in PC3 and K562 cancer cells in the absence of corepressor BASP1

Dysregulated alternative splicing plays a prominent role in all hallmarks of cancer. The splice factor kinase SRPK1 drives the activity of oncogenic splice factors such as SRSF1. SRSF1 in turn promotes the expression of splice isoforms that favour tumour growth, including proangiogenic VEGF. Knockdown (with siRNA) or chemical inhibition (using SPHINX) of SRPK1 in K562 leukemia and PC3 prostate cancer cell lines reduced cell proliferation, invasion and migration. In glomerular podocytes, the Wilms tumour suppressor zinc-finger transcription factor WT1 represses SRPK1 transcription. Here we show that in cancer cells WT1 activates SRPK1 transcription, unless a canonical WT1 binding site adjacent to the transcription start site is mutated. The ability of WT1 to activate SRPK1 transcription was reversed by the transcriptional corepressor BASP1, and both WT1 and BASP1 co-precipitated with the SRPK1 promoter. BASP1 significantly increased the expression of the antiangiogenic VEGF₁₆₅b splice isoform. We propose that by upregulating SRPK1 transcription WT1 can direct an alternative splicing landscape that facilitates tumour growth.

The role of WT1 in breast cancer: clinical implications, biological effects and molecular mechanism

Although Wilms' tumor gene 1 (WT1) was first cloned and identified as a tumor suppressor gene in nephroblastoma, subsequent studies have demonstrated that it can also play an oncogenic role in leukemia and various solid tumors. WT1 exerts biological functions with high tissue- and cell-specificity. This article reviews the relationship between WT1 and breast cancer from two aspects: (1) clinical application of WT1, including the relationship between expression of WT1 and prognosis of breast cancer patients, and its effectiveness as a target for comprehensive therapy of breast cancer; (2) the biological effects and molecular mechanisms of WT1 in the development and progression of breast cancer, including proliferation, apoptosis, invasion, and metastasis of breast cancer cells.

Plasmacytoid cells in salivary pleomorphic adenoma: an alternative interpretation of their immunohistochemical characteristics highlights function and capability for epithelial-mesenchymal transition

OBJECTIVES

Plasmacytoid cells (PLCs) in salivary pleomorphic adenoma (SPA) are regarded as modified neoplastic myoepithelia and define plasmacytoid myoepithelioma (pMYO). However, histochemically, immunohistochemically and ultrastructurally, PLCs fail to demonstrate frank myogenous properties. Epithelial-mesenchymal transition (EMT) may explain the phenotypes in SPA. Our aim was to evaluate (1) PLCs with accepted or purported myoepithelial and EMT-related markers; and (2) pMYOs for PLAG1 aberrations by using fluorescence in situ hybridization.

STUDY DESIGN

Eight SPAs with or without PLC-predominance and 3 pMYOs were immunohistochemically studied.

RESULTS

PLCs in SPA and pMYO exhibited strong, scattered to diffuse positivity for K7, rare K14 positivity and were mostly negative for α-smooth muscle actin, h-caldesmon, and p63/p40. S100 staining was strong and diffuse, whereas calponin was variable. DOG1 was negative. PLCs in pMYO and PLC-rich SPA exhibited selective or diffuse WT1 and D2-40 immunoreactivity. EMT markers SNAIL/SLUG exhibited strong and variable immunoreactivity in PLCs in contrast to weak or absent E-cadherin expression. SOX10 was diffusely and strongly positive. PLAG1 rearrangement was present in 1 pMYO.

CONCLUSIONS

PLCs mostly fail to express myoepithelial markers; PLCs are neoplastic cells adapting to microenvironmental changes and capable of EMT; and tumors composed solely of PLCs are apparently SPAs depleted of a ductal component.

Overexpression of Wilms' tumor 1 in skin lesions of psoriasis is associated with abnormal proliferation and apoptosis of keratinocytes

Psoriasis vulgaris (PV) is a chronic inflammatory skin disease, which is characterized by the abnormal proliferation and apoptosis of keratinocytes. Previous studies have demonstrated that transcription factor Wilms' tumor 1 (WT1) is involved in a number of pathophysiological processes, including organ development, tumorigenesis and cell proliferation. However, the role of WT1 in PV remains unclear. In the present study, WT1 expression was analyzed by reverse transcription‑quantitative polymerase chain reaction and western blot analyses. WT1 was stably overexpressed or inhibited in HaCaT cells using Lipofectamine® 2000, and cell proliferation and apoptosis were determined using a Cell Counting Kit‑8 or Fluorescein Isothiocyanate Annexin V Apoptosis Detection kit II, respectively. We demonstrated that compared with normal controls, the mRNA and protein expression levels of WT1 were significantly increased in non‑lesional skins (human, P<0.0001 and P=0.0291, respectively; mouse, P=0.0020 and P=0.0150, respectively) and lesional skins (human, P<0.0001 and P=0.0060, respectively; mouse, P=0.0010 and P=0.0172, respectively) of patients with PV, in addition to the imiquimod (IMQ)‑induced psoriasis‑like mouse model. WT1 mRNA and protein expression levels in lesional skins were slightly increased compared with those in non‑lesional skins from patients with psoriasis (P=0.2510 and P=0.1690, respectively) and IMQ‑treated mice (P=0.9590 and P=0.2552, respectively), although there were no statistical differences. Knockdown of WT1 inhibited the proliferation of HaCaT cells [day (D)4, P=0.0454; D5, P=0.0021] and promoted their apoptosis (P=0.0007), while overexpressing WT1 exhibited the opposite effects (proliferation D3, P=0.0216; D4, P=0.0356; D5, P=0.0188; apoptosis, P=0.0003). Furthermore, it was identified that the inflammatory cytokines interleukin‑17A (IL‑17A), interferon‑γ and IL‑22 induced the overexpression of WT1 in HaCaT cells. The results of the present study suggested that inflammatory cytokine‑induced WT1 overexpression may promote the formation of psoriatic skin lesions via regulation of the proliferation and apoptosis of keratinocytes.

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

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

Studies of Wilms’ Tumor (WT1) Gene Expression in Adult Acute Leukemias in Singapore

Biomarkers provide certain values for diagnosis, monitor treatment efficacy, or for the development of novel therapeutic approach for particular diseases. Thus, the identification of specific of biomarkers for specific medical problems, including malignant diseases may be valuable in medical practice. In the study, we have used the Wilms’ tumor gene ( WT1) as a biomarker to evaluate its expression in local adult patients with newly diagnosed acute leukemia, including both acute myeloid and lymphoid leukemias (AML and ALL).

Aim

To investigate WT1 gene expression in adult patients with acute leukemia at diagnosis.

Methods

Eighteen patients with acute leukemia diagnosed at Singapore General Hospital, Singapore, between September, 2004 and July, 2005 were included in this study. There were fifteen AML and three ALL cases aged from 18 to 71 years old. Total RNA and DNA was extracted from peripheral blood mononuclear cells (PBMCs). Expression of WT1 was detected by nested reverse-transcription polymerase chain reaction (Nested RT-PCR). K562, and 3T3 cells were used as positive- and negative-controls. The results were revalidated using real-time PCR. HLA-A genotyping was performed using sequence specific oligonucleotide polymorphism (SSOP) analysis.

Results

WT1 gene was exclusively expressed in all eighteen, including three ALL and fifteen AML, patients. In contrast with WT1 gene, the HLA-A genotyping was remarkably heterogeneous in these patients.

Conclusions

WT1 gene expression was observed in local patients with acute leukemia at diagnosis. It may be used as a potential molecular marker for diagnosis, clinical progression of the diseases or monitoring the response to treatment, as well as a target for the development of novel therapeutic approaches.

The Role of WT1 in Embryonic Development and Normal Organ Homeostasis

The Wilms' tumor suppressor gene 1 (Wt1) is critically involved in a number of developmental processes in vertebrates, including cell differentiation, control of the epithelial/mesenchymal phenotype, proliferation, and apoptosis. Wt1 proteins act as transcriptional and post-transcriptional regulators, in mRNA splicing and in protein-protein interactions. Furthermore, Wt1 is involved in adult tissue homeostasis, kidney function, and cancer. For these reasons, Wt1 function has been extensively studied in a number of animal models to establish its spatiotemporal expression pattern and the developmental fate of the cells expressing this gene. In this chapter, we review the developmental anatomy of Wt1, collecting information about its dynamic expression in mesothelium, kidney, gonads, cardiovascular system, spleen, nervous system, lung, and liver. We also describe the adult expression of Wt1 in kidney podocytes, gonads, mesothelia, visceral adipose tissue, and a small fraction of bone marrow cells. We have reviewed the available animal models for Wt1-expressing cell lineage analysis, including direct Wt1 expression reporters and systems for permanent Wt1 lineage tracing, based on constitutive or inducible Cre recombinase expression under control of a Wt1 promoter. Finally we provide a number of laboratory protocols to be used with these animal models in order to assess reporter expression.

Trop2 and its overexpression in cancers: regulation and clinical/therapeutic implications

Trop2 is a transmembrane glycoprotein encoded by the Tacstd2 gene. It is an intracellular calcium signal transducer that is differentially expressed in many cancers. It signals cells for self-renewal, proliferation, invasion, and survival. It has stem cell-like qualities. Trop2 is expressed in many normal tissues, though in contrast, it is overexpressed in many cancers and the overexpression of Trop2 is of prognostic significance. Several ligands have been proposed that interact with Trop2. Trop2 signals the cells via different pathways and it is transcriptionally regulated by a complex network of several transcription factors. Trop2 expression in cancer cells has been correlated with drug resistance. Several strategies target Trop2 on cancer cells that include antibodies, antibody fusion proteins, chemical inhibitors, nanoparticles, etc. The in vitro studies and pre-clinical studies, using these various therapeutic treatments, have resulted in significant inhibition of tumor cell growth both in vitro and in vivo in mice. A clinical study is underway using IMMU-132 (hrS7 linked to SN38) in patients with epithelial cancers. This review describes briefly the various characteristics of cancer cells overexpressing Trop2 and the potential application of Trop2 as both a prognostic biomarker and as a therapeutic target to reverse resistance.

WT1 regulates angiogenesis in Ewing Sarcoma

Angiogenesis is required for tumor growth. WT1, a protein that affects both mRNA transcription and splicing, has recently been shown to regulate expression of vascular endothelial growth factor (VEGF), one of the major mediators of angiogenesis. In the present study, we tested the hypothesis that WT1 is a key regulator of tumor angiogenesis in Ewing sarcoma. We expressed exogenous WT1 in the WT1-null Ewing sarcoma cell line, SK-ES-1, and we suppressed WT1 expression using shRNA in the WT1-positive Ewing sarcoma cell line, MHH-ES. Suppression of WT1 in MHH-ES cells impairs angiogenesis, while expression of WT1 in SK-ES-1 cells causes increased angiogenesis. Different WT1 isoforms result in vessels with distinct morphologies, and this correlates with preferential upregulation of particular VEGF isoforms. WT1-expressing tumors show increased expression of pro-angiogenic molecules such as VEGF, MMP9, Ang-1, and Tie-2, supporting the hypothesis that WT1 is a global regulator of angiogenesis. We also demonstrate that WT1 regulates the expression of a panel of pro-angiogenic molecules in Ewing sarcoma cell lines. Finally, we found that WT1 expression is correlated with VEGF expression, MMP9 expression, and microvessel density in samples of primary Ewing sarcoma. Thus, our results demonstrate that WT1 expression directly regulates tumor angiogenesis by controlling the expression of a panel of pro-angiogenic genes.

T cell-based targeted immunotherapies for patients with multiple myeloma

Despite high-dose chemotherapy followed by autologs stem-cell transplantation as well as novel therapeutic agents, multiple myeloma (MM) remains incurable. Following the general trend towards personalized therapy, targeted immunotherapy as a new approach in the therapy of MM has emerged. Better progression-free survival and overall survival after tandem autologs/allogeneic stem cell transplantation suggest a graft versus myeloma effect strongly supporting the usefulness of immunological therapies for MM patients. How to induce a powerful antimyeloma effect is the key issue in this field. Pivotal is the definition of appropriate tumor antigen targets and effective methods for expansion of T cells with clinical activity. Besides a comprehensive list of tumor antigens for T cell-based approaches, eight promising antigens, CS1, Dickkopf-1, HM1.24, Human telomerase reverse transcriptase, MAGE-A3, New York Esophageal-1, Receptor of hyaluronic acid mediated motility and Wilms' tumor gene 1, are described in detail to provide a background for potential clinical use. Results from both closed and on-going clinical trials are summarized in this review. On the basis of the preclinical and clinical data, we elaborate on three encouraging therapeutic options, vaccine-enhanced donor lymphocyte infusion, chimeric antigen receptors-transfected T cells as well as vaccines with multiple antigen peptides, to pave the way towards clinically significant immune responses against MM.

Promoter methylation patterns in Richter syndrome affect stem-cell maintenance and cell cycle regulation and differ from de novo diffuse large B-cell lymphoma

In a fraction of patients, chronic lymphocytic leukaemia (CLL) can transform to Richter syndrome (RS), usually a diffuse large B-cell lymphoma (DLBCL). We studied genome-wide promoter DNA methylation in RS and clonally related CLL-phases of transformed patients, alongside de novo DLBCL (of non-germinal centre B type), untransformed-CLL and normal B-cells. The greatest differences in global DNA methylation levels were observed between RS and DLBCL, indicating that these two diseases, although histologically similar, are epigenetically distinct. RS was more highly methylated for genes involved in cell cycle regulation. When RS was compared to the preceding CLL-phase and with untransformed-CLL, RS presented a higher degree of methylation for genes possessing the H3K27me3 mark and PRC2 targets, as well as for gene targets of TP53 and RB1. Comparison of the methylation levels of individual genes revealed that OSM, a stem cell regulatory gene, exhibited significantly higher methylation levels in RS compared to CLL-phases. Its transcriptional repression by DNA methylation was confirmed by 5-aza-2'deoxycytidine treatment of DLBCL cells, determining an increased OSM expression. Our results showed that methylation patterns in RS are largely different from de novo DLBCL. Stem cell-related genes and cell cycle regulation genes are targets of DNA methylation in RS.

WT1 promotes cell proliferation in non-small cell lung cancer cell lines through up-regulating cyclin D1 and p-pRb in vitro and in vivo

The Wilms’ tumor suppressor gene (WT1) has been identified as an oncogene in many malignant diseases such as leukaemia, breast cancer, mesothelioma and lung cancer. However, the role of WT1 in non-small-cell lung cancer (NSCLC) carcinogenesis remains unclear. In this study, we compared WT1 mRNA levels in NSCLC tissues with paired corresponding adjacent tissues and identified significantly higher expression in NSCLC specimens. Cell proliferation of three NSCLC cell lines positively correlated with WT1 expression; moreover, these associations were identified in both cell lines and a xenograft mouse model. Furthermore, we demonstrated that up-regulation of Cyclin D1 and the phosphorylated retinoblastoma protein (p-pRb) was mechanistically related to WT1 accelerating cells to S-phase. In conclusion, our findings demonstrated that WT1 is an oncogene and promotes NSCLC cell proliferation by up-regulating Cyclin D1 and p-pRb expression.

The Trop-2 signalling network in cancer growth

Our findings show that upregulation of a wild-type Trop-2 has a key controlling role in human cancer growth, and that tumour development is quantitatively driven by Trop-2 expression levels. However, little is known about the regulation of expression of the TROP2 gene. Hence, we investigated the TROP2 transcription control network. TROP2 expression was shown to depend on a highly interconnected web of transcription factors: TP63/TP53L, ERG, GRHL1/Get-1 (grainyhead-like epithelial transactivator), HNF1A/TCF-1 (T-cell factor), SPI1/PU.1, WT (Wilms' tumour)1, GLIS2, AIRE (autoimmune regulator), FOXM1 (forkhead box M1) and FOXP3, with HNF4A as the major network hub. TROP2 upregulation was shown to subsequently drive the expression and activation of CREB1 (cyclic AMP-responsive-element binding protein), Jun, NF-κB, Rb, STAT1 and STAT3 through induction of the cyclin D1 and ERK (extracellular signal regulated kinase)/MEK (MAPK/ERK kinase) pathways. Growth-stimulatory signalling through NF-κB, cyclin D1 and ERK was shown to require an intact Trop-2 cytoplasmic tail. Network hubs and interacting partners are co-expressed with Trop-2 in primary human tumours, supporting a role of this signalling network in cancer growth.

Dysregulation of gene expression in the artificial human trisomy cells of chromosome 8 associated with transformed cell phenotypes

A change in chromosome number, known as aneuploidy, is a common characteristic of cancer. Aneuploidy disrupts gene expression in human cancer cells and immortalized human epithelial cells, but not in normal human cells. However, the relationship between aneuploidy and cancer remains unclear. To study the effects of aneuploidy in normal human cells, we generated artificial cells of human primary fibroblast having three chromosome 8 (trisomy 8 cells) by using microcell-mediated chromosome transfer technique. In addition to decreased proliferation, the trisomy 8 cells lost contact inhibition and reproliferated after exhibiting senescence-like characteristics that are typical of transformed cells. Furthermore, the trisomy 8 cells exhibited chromosome instability, and the overall gene expression profile based on microarray analyses was significantly different from that of diploid human primary fibroblasts. Our data suggest that aneuploidy, even a single chromosome gain, can be introduced into normal human cells and causes, in some cases, a partial cancer phenotype due to a disruption in overall gene expression.

Angiotensin-(1-7) reduces fibrosis in orthotopic breast tumors

Angiotensin-(1-7) [Ang-(1-7)] is an endogenous 7-amino acid peptide hormone of the renin-angiotensin system that has antiproliferative properties. In this study, Ang-(1-7) inhibited the growth of cancer-associated fibroblasts (CAF) and reduced fibrosis in the tumor microenvironment. A marked decrease in tumor volume and weight was observed in orthotopic human breast tumors positive for the estrogen receptor (BT-474 or ZR-75-1) and HER2 (BT-474) following Ang-(1-7) administration to athymic mice. Ang-(1-7) concomitantly reduced interstitial fibrosis in association with a significant decrease in collagen I deposition, along with a similar reduction in perivascular fibrosis. In CAFs isolated from orthotopic breast tumors, the heptapeptide markedly attenuated in vitro growth as well as reduced fibronectin, transforming growth factor-β (TGF-β), and extracellular signal-regulated kinase 1/2 kinase activity. An associated increase in the mitogen-activated protein kinase (MAPK) phosphatase DUSP1 following treatment with Ang-(1-7) suggested a potential mechanism by which the heptapeptide reduced MAPK signaling. Consistent with these in vitro observations, immunohistochemical analysis of Ang-(1-7)-treated orthotopic breast tumors revealed reduced TGF-β and increased DUSP1. Together, our findings indicate that Ang-(1-7) targets the tumor microenvironment to inhibit CAF growth and tumor fibrosis.

WT1 Gene Transcript Assay for Relapse in Acute Leukemia after Transplantation

The WT1 gene is highly expressed in various types of leukemia, particularly in acute type leukemia. The extent of minimal residual disease (MRD) of leukemia can be evaluated by measuring the WT1 gene expression level using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. The WT1 transcript assay can be applied to almost all patients with leukemia regardless of the presence or absence of chimeric DNA markers. Furthermore, because of the fact that WT1 expression levels increase significantly at relapse compared with those at the time of diagnosis, and because of the decrease in background levels of WT1 expression in bone marrow following allogeneic SCT, the WT1 transcript assay possesses a high degree of sensitivity following allogeneic SCT. Frequent monitoring of the WT1 gene expression level predicts the risk of relapse following allogeneic SCT, and furthermore, the kinetics of WT1 transcripts predict the efficacy of immunomodulation therapy such as donor leukocyte infusion.

WT1 immunoreactivity in breast carcinoma: selective expression in pure and mixed mucinous subtypes

Current literature suggests that strong WT1 expression in a carcinoma of unknown origin virtually excludes a breast primary. Our previous pilot study on WT1 expression in breast carcinomas has shown WT1 expression in approximately 10% of carcinomas that show mixed micropapillary and mucinous morphology (Mod Pathol 2007;20(Suppl 2):38A). To definitively assess as to what subtype of breast carcinoma might express WT1 protein, we examined 153 cases of invasive breast carcinomas. These consisted of 63 consecutive carcinomas (contained 1 mucinous tumor), 20 cases with micropapillary morphology (12 pure and 8 mixed), 6 micropapillary 'mimics' (ductal no special type carcinomas with retraction artifacts), 33 pure mucinous carcinomas and 31 mixed mucinous carcinomas (mucinous mixed with other morphologic types). Overall, WT1 expression was identified in 33 carcinomas, that is, 22 of 34 (65%) pure mucinous carcinomas and in 11 of 33 (33%) mixed mucinous carcinomas. The non-mucinous component in these 11 mixed mucinous carcinomas was either a ductal no special type carcinoma (8 cases) or a micropapillary component (3 cases). WT1 expression level was similar in both the mucinous and the non-mucinous components. The degree of WT1 expression was generally weak to moderate (>90% cases) and rarely strong (<10% cases). None of the breast carcinoma subtype unassociated with mucinous component showed WT1 expression.

Wilms' tumor 1 message and protein expression in bone marrow failure syndrome and acute leukemia

Wilms' tumor 1 (WT1) is a useful marker for the diagnosis of acute leukemia and myelodysplastic syndromes (MDS). In the current study quantitative reverse transcription-polymerase chain reaction and immunostaining were used simultaneously to examine the relationship between WT1 RNA and protein level and also to evaluate WT1 as a tool to differentiate aplastic anemia (AA) and MDS refractory anemia (RA). Three types of WT1 messages (total, exon 5(+) and KTS(+)) and WT1 immunostaining of these diseases were analyzed. An increase of all three WT1 messages in high-grade MDS and acute leukemia was observed as compared with the normal control, whereas there was no significant difference in WT1 message between AA and RA, suggesting that WT1 message is not a good tool to discriminate AA and RA. No significant difference was observed between normal and RA, except for exon 5 message. Three WT1 message levels had a significant correlation, suggesting that the total WT1 message is sufficient for clinical practice. Positive immunostaining of WT1 was observed only in the portion of acute leukemia and overt leukemia (OL) transformed from MDS with a high WT1 message level, suggesting the relatively high detection threshold of WT1 protein with the immunostaining method.

Wilms' tumor protein 1: an early target of progestin regulation in T-47D breast cancer cells that modulates proliferation and differentiation

Progesterone regulates the proliferation and differentiation of normal mammary epithelium. In breast cancer cells, progesterone and its synthetic analogs, progestins, induce long-term growth inhibition and differentiation. However, the mechanisms responsible are not fully understood. When T-47D breast cancer cells were treated with the synthetic progestin ORG 2058 (16alpha-ethoxy-21-hydroxy-19-norpregn-4-en-3,20-dione), all isoforms of Wilms' tumor protein 1 (Wt1) mRNA and protein were rapidly downregulated. We reasoned that the decrease in Wt1 levels may contribute to the long-term antiproliferative and differentiative effects of progestins as proliferation and differentiation are known end points of Wt1 action. Consistent with this idea, Wt1 small interfering RNA led to a decrease in S phase and cyclin D1 levels, and increased Oil-Red-O staining, indicating increased lipogenesis. Conversely, overexpression of Wt1 attenuated the decrease in S phase induced by ORG 2058 at 48-96 h. This was accompanied by the sustained expression of cyclin D1 despite progestin treatment, and increased levels of retinoblastoma (Rb) phosphorylation at sites targeted by cyclin D1-Cdk4 (Ser249/Thr252). Wt1 overexpression also attenuated the ORG 2058-mediated increase in fatty acid synthase levels and reduced lipogenesis. Thus, Wt1 downregulation was sufficient to mimic the effects of progestin and was necessary for complete progestin-mediated proliferative arrest and subsequent differentiation. Furthermore, Wt1 overexpression modulated the effects of progestins but not anti-estrogens or androgens. These results indicate that Wt1 is an important early target of progestins that regulates both proliferation and differentiation in breast cancer cells.

Histone modification enzymes induced during chemical hepatocarcinogenesis

Aberrant methylation patterns of genomic DNA are well-studied epigenetic mutations in cancer. Hypermethylation of CpG islands in tumor-suppressor genes promotes oncogenesis and hypomethylation of global genomic DNA affects genomic stability. Cancer is recognized as a genetic and epigenetic disease. However, it is not clear how epigenetic regulatory factors, including histone modification enzymes, chromatin components and other factors are involved in carcinogenesis. To gain insights into the molecular mechanisms mediated by these factors at the early stage of hepatocarcinogenesis and hepatotoxicity induced by chemicals, we investigated gene expression profiles by DNA microarray and Western blot analyses. We prepared RNA and nuclear extracts from livers with hyperplastic nodules expressing Glutathione S-transferase placental form (GST-P) and compared findings with those of normal liver. GST-P is a phase II detoxification enzyme and a well-known tumor marker. We identified several epigenetic regulatory factors that showed dysregulated expression during chemically induced hepatocarcinogenesis. Here I review the characterization and functions of these factors and discuss the mechanisms of tumor marker gene expression during chemical hepatocarcinogenesis.

Inhibition of fibroblast to myofibroblast transition by halofuginone contributes to the chemotherapy-mediated antitumoral effect

Stromal myofibroblasts play an important role in tumor progression. The transition of fibroblasts to myofibroblasts is characterized by expression of smooth muscle genes and profuse synthesis of extracellular matrix proteins. We evaluated the efficacy of targeting fibroblast-to-myofibroblast transition with halofuginone on tumor progression in prostate cancer and Wilms' tumor xenografts. In both xenografts, low doses of halofuginone treatment, independent of the route of administration, resulted in a trend toward inhibition in tumor development. Moreover, halofuginone synergizes with low dose of docetaxel in prostate cancer and vincristine and dactinomycin in Wilms' tumor xenografts, resulting in significant reduction in tumor volume and weight comparable to the effect observed by high doses of the respective chemotherapies. In prostate cancer and Wilms' tumor xenografts, halofuginone, but not the respective chemotherapies, inhibited the synthesis of collagen type I, alpha-smooth muscle actin, transgelin, and cytoglobin, all of which are characteristics of activated myofibroblasts. Halofuginone, as the respective chemotherapies, increased the synthesis of Wilms' tumor suppressor gene product (WT-1) and prostate apoptosis response gene-4 (Par-4), resulting in apoptosis/necrosis. These results suggest that targeting the fibroblast-to-myofibroblast transition with halofuginone may synergize with low doses of chemotherapy in achieving a significant antitumoral effect, avoiding the need of high-dose chemotherapy and its toxicity without impairing treatment efficacy.

Altered gene expression of transcriptional regulatory factors in tumor marker-positive cells during chemically induced hepatocarcinogenesis

Glutathione-S-transferase placental form (GST-P) is markedly and specifically inducible in rat chemical hepatocarcinogenesis and is a reliable marker protein for pre-neoplasia. To gain insights into the molecular mechanisms at the early stage of hepatocarcinogenesis and hepatotoxicity, we investigated the gene expression profile by DNA microarray analysis. We prepared RNA from GST-P-positive foci in three individual rats and compared with normal liver sections from three individual rats, and labeled RNA was individually hybridized onto Affymetrix GeneChip Rat Expression Array 230A. DNA microarray analysis showed distinctly different profiles of dysregulated gene expression and supported the previous finding that some enzymes involved in metabolism and detoxification are overexpressed and suppressed. Here we discovered that several DNA-binding transcription factors and cofactors, including sterol-regulatory-element binding protein 1 (SREBP1) and Wilms' tumour 1 (WT1)-interacting protein, and their target genes were dysregulated in GST-P-positive foci. Moreover, genes involved in chromatin components, histone modification enzymes, and centrosome duplication were highly expressed. These genes were not previously known to be up-regulated during chemically induced hepatocarcinogenesis. DNA microarray analysis using RNA prepared from tumor marker-positive foci and control tissues provided a candidate gene link to the early stage of carcinogenesis and hepatotoxicity.

Cancer immunotherapy targeting Wilms' tumor gene WT1 product

The Wilms' tumor gene WT1 is expressed at high levels in leukemic blast cells in most acute myeloid and lymphoblastic leukemias. In myelodysplastic syndrome, WT1 mRNA expression levels increase along with disease progression; thus, WT1 mRNA is a tumor marker for leukemic blast cells. WT mRNA is also expressed at high levels in various types of solid cancers, including cancers of the lung, breast, colon and pancreas. Patients with WT1-expressing tumors produce antibodies and cytotoxic T-lymphocytes against WT1 protein, indicating that WT1 protein is highly immunogenic and a promising tumor antigen. Major histocompatibility complex class I-restricted cytotoxic T-lymphocyte and class II-restricted helper epitopes of WT1 protein were identified, and clinical studies of cancer immunotherapy using these cytotoxic T-lymphocyte epitope peptides were performed without significant adverse effect and with clinical results promising enough to encourage further clinical trials. The clinical efficacy of cancer immunotherapy targeting the WT1 protein should be clarified by a large-scale clinical study.

N-terminally truncated WT1 protein with oncogenic properties overexpressed in leukemia

WT1 was originally identified as an inactivated gene in Wilms tumor, a childhood kidney cancer. Alternative splicing of the WT1 transcript generates four major protein isoforms, each having different functional properties. Here we characterized a short transcript originating from a second promoter located within intron 1 of WT1. This 2.3-kb sWT1 transcript encodes a protein of approximately 35-37 kDa that retains intact DNA-binding and transactivation domains but lacks the 147 amino acids at the N terminus required for transcriptional repression. We found sWT1 to be a more potent transcriptional activator than WT1 for cyclin E and insulin-like growth factor 1 receptor promoters, which are normally repressed by WT1. The expression patterns of the sWT1 and WT1 transcripts differed slightly in various organs; we found sWT1 protein in tissue samples from adult testis and fetal kidney, with low-level expression in adult kidney as well. The sWT1 transcript, but not the full-length transcript, was over-expressed in the leukemia samples tested. sWT1-specific small interfering RNA retarded the proliferation of leukemia cell line K562 in vitro. Finally, sWT1 cooperated with Ras in transforming primary fibroblasts in vitro. Further studies are needed to clarify the oncogenic behavior of this isoform and to determine the mechanism underlying its up-regulation in leukemia and other forms of cancer.

Wilms' tumor gene 1 (WT1) expression in childhood acute lymphoblastic leukemia: a wide range of WT1 expression levels, its impact on prognosis and minimal residual disease monitoring

Wilms' tumor gene 1 (WT1) is overexpressed in the majority (70-90%) of acute leukemias and has been identified as an independent adverse prognostic factor, a convenient minimal residual disease (MRD) marker and potential therapeutic target in acute leukemia. We examined WT1 expression patterns in childhood acute lymphoblastic leukemia (ALL), where its clinical implication remains unclear. Using a real-time quantitative PCR designed according to Europe Against Cancer Program recommendations, we evaluated WT1 expression in 125 consecutively enrolled patients with childhood ALL (106 BCP-ALL, 19 T-ALL) and compared it with physiologic WT1 expression in normal and regenerating bone marrow (BM). In childhood B-cell precursor (BCP)-ALL, we detected a wide range of WT1 levels (5 logs) with a median WT1 expression close to that of normal BM. WT1 expression in childhood T-ALL was significantly higher than in BCP-ALL (P<0.001). Patients with MLL-AF4 translocation showed high WT1 overexpression (P<0.01) compared to patients with other or no chromosomal aberrations. Older children (> or =10 years) expressed higher WT1 levels than children under 10 years of age (P<0.001), while there was no difference in WT1 expression in patients with peripheral blood leukocyte count (WBC) > or =50 x 10(9)/l and lower. Analysis of relapsed cases (14/125) indicated that an abnormal increase or decrease in WT1 expression was associated with a significantly increased risk of relapse (P=0.0006), and this prognostic impact of WT1 was independent of other main risk factors (P=0.0012). In summary, our study suggests that WT1 expression in childhood ALL is very variable and much lower than in AML or adult ALL. WT1, thus, will not be a useful marker for MRD detection in childhood ALL, however, it does represent a potential independent risk factor in childhood ALL. Interestingly, a proportion of childhood ALL patients express WT1 at levels below the normal physiological BM WT1 expression, and this reduced WT1 expression appears to be associated with a higher risk of relapse.

Expression, purification, and characterization of the 4 zinc finger region of human tumor suppressor WT1

Wilm's Tumor gene 1 (WT1) encodes a zinc finger protein with four distinct splice isoforms. WT1 has a critical role in genesis of various cancer types both at the DNA/RNA and the protein level. The zinc-finger DNA-binding capacity of the protein is located in the C-terminal domain. Two recombinant proteins, 6HIS-ZN-wt1 and 6HIS-ZN+wt1, corresponding to two alternative splice variants of the C-terminal regions of human WT1 (-KTS) and WT1 (+KTS), respectively, were over-expressed with hexa-histidine fusion tags in inclusion bodies in Escherichia coli for crystallization studies. A combination of Ni2+-NTA affinity and size-exclusion chromatography was applied for purification of the proteins in denaturing conditions. The effects of various buffers, salts and other additives were scrutinized in a systematic screening to establish the optimal conditions for solubility and refolding of the recombinant WT1 proteins. Circular dichroism analysis revealed the expected betabetaalpha content for the refolded proteins, with a notable degradation of the alpha-helical segment in the DNA-free state. Electrophoretic mobility shift assay with double-stranded DNA containing the double Egr1 consensus site 5'-GCG-TGG-GCG-3' confirmed that 6HIS-ZN-wt1 has higher DNA binding affinity than 6HIS-ZN+wt1.

Genetic mapping of a Ptch1-associated rhabdomyosarcoma susceptibility locus on mouse chromosome 2

Mutations in the Patched (Ptch1) gene are responsible for various familial and sporadic cancers. Ptch1(neo67/+) mice, in which exons 6 and 7 are deleted, show genetic background-dependent susceptibility to the development of muscle tumors resembling human rhabdomyosarcoma (RMS); BALB/c (BALB) is a susceptible strain whereas C57BL/6 (B6) shows resistance. A genome-wide linkage analysis was carried out using Ptch1(neo67/+)mice produced from B6 x (BALB x B6) backcrosses to identify loci involved in the control of RMS susceptibility. Quantitative trait locus mapping with the censored tumor latency time as the quantitative parameter was used to detect a significant RMS susceptibility modifier locus, Parms1 (Patched-Associated RMS 1), on chromosome 2 between D2Mit37 and D2Mit102 (LRS = 10). A Kaplan-Meier survival curve revealed that mice with the B6/BALB genotype develop tumors more frequently and much faster as compared to mice homozygous for the B6 allele (P = 0.02). Additional loci not reaching linkage significance were also detected for medulloblastoma resistance.

Renal metanephric adenoma with previously unreported cytogenetic abnormalities: case report and review of the literature

We report a case of a renal metanephric adenoma in a 10-year-old boy, in which cytogenetic analysis showed a balanced translocation, t(9;15)(p24;q24) and a balanced paracentric inversion of chromosome 12, inv(12)(q13q15). Immunohistochemically, the tumor showed diffuse reactivity for cytokeratin AE1/AE3, CAM5.2, CD57, and WT1; patchy reactivity for CD56; and focal reactivity for cytokeratin 7, epithelial membrane antigen, and CD10. Tumor cells were entirely nonreactive for alpha-methyl acyl coenzyme A racemase. Published cytogenetic data for metanephric adenomas are limited, and this is the first report of these cytogenetic abnormalities. The involvement of the chromosome region 9p24 is particularly interesting because of the recent identification of a tumor suppressor gene, KANK (kidney ankyrin repeat-containing protein), at this locus.

Chromosomal alterations detected by comparative genomic hybridization in nonfunctioning endocrine pancreatic tumors

We have used comparative genomic hybridization to investigate changes in DNA copy number in 20 nonfunctioning endocrine pancreatic tumors. The total number of regional DNA imbalances per tumor showed variation from case to case and high genetic heterogeneity was observed. From 1 to 22 chromosomal anomalies were detected in 13 of the 20 cases evaluated. Overall gains predominated over losses with a ratio of about 3.9:1 (58 gains/15 losses). The mean total number of regions displaying imbalances increased from 1.25 per tumor for benign tumors to 5.25 for malignant tumors, although statistical significance was not reached (P=0.074).

Expression of the Wilms' tumor gene product WT1 in glioblastomas and medulloblastomas

The Wilms' tumor gene WT1 was first identified as the gene responsible for a childhood renal tumor, Wilms' tumor. This gene encodes for a zinc finger-containing transcription factor. Although originally identified as a tumor suppressor gene, WT1 is overexpressed in a variety of hematologic malignancies and solid tumors. Recently, WT1 protein has been considered as a new molecular target of cancer immunotherapy for several solid tumors. In the present study, we investigated the expression of WT1 protein and WT1 mRNA in glioblastomas and medulloblastomas. Forty-eight of 51 glioblastoma samples (94%) showed immunohistochemically positive staining of WT1 protein, whereas all 10 medulloblastomas examined were negative. According to the immunohistochemical expression of WT1 protein, WT1 mRNA was also highly expressed in the same glioblastoma tissue. Our results suggest that the WT1 gene may play an important role in the tumorigenesis of glioblastoma, in contrast to medulloblastoma, and be integral in the development of the immunotherapy targeting WT1 protein in patients with glioblastoma.

Expression of Wilms' tumor gene 1 at different stages of acute myeloid leukemia and analysis of its major splice variants

WT1 is a transcription factor involved in differentiation and proliferation of acute myeloid leukemia (AML) blasts and is expressed in 90% of cases, as determined by nested reverse transcription polymerase chain reaction (RT-PCR). It is proposed to be a key molecule in leukemia promotion. To assess the relevance of WT1 expression, we analyzed blood and bone marrow samples from 58 AML patients (37 at diagnosis, 8 in hematological remission, and 13 at relapse) for the level of WT1 expression, using quantitative real-time RT-PCR. In addition, 21 randomly chosen samples were also analyzed for the quantitative expression of the main WT1 splice variants. As expected, samples from patients at the time of diagnosis or relapse showed significantly higher WT1 expression compared to samples from patients in remission or control samples. No striking difference in expression levels was found between various French-American-British (FAB) subtypes. The level of WT1 expression observed in patients at the time of initial diagnosis was similarly high in patients at relapse. Expression of the four main isoforms (E5+/KTS+, E5-/KTS+, E5+/KTS-, and E5-/KTS-) was found in all samples with significantly higher expression levels of the E5+ variants. Together, these findings support the potential of WT1 as a target for novel treatment approaches in AML.

The Wilms Tumor Suppressor-1 Target Gene Podocalyxin Is Transcriptionally Repressed by p53

Wilms tumors are a heterogeneous class of tumors in which Wilms tumor suppressor-1 (WT1) and the p53 tumor suppressor may be variously inactivated by mutation, reduced in expression, or even overexpressed in the wild-type state. The downstream transcriptional targets of WT1 and p53 that are critical for mediating their roles in Wilms tumorigenesis are not well defined. The WiT49 cell line is characteristic of anaplastic Wilms tumors that are refractory to treatment and expresses wild-type WT1 and mutant p53. We have used the small molecule compound CP-31398 (Pfizer) to restore wild-type p53 function to the codon 248 mutant p53 present in WiT49 cells. In these cells, CP-31398 activated transcription of p53-regulated promoters and enhanced UV light-induced apoptosis without altering the overall p53 protein level. These phenotypes were accompanied by restored binding of the p53 protein to promoter sequences in vivo. Gene expression profiling of CP-31398-treated WiT49 cells revealed subsets of putative p53 target genes that were up- or down-regulated. A preferred target of p53-mediated repression in this system is the podocalyxin (PODXL) gene. PODXL is also transcriptionally regulated by WT1 and has roles in cell adhesion and anti-adhesion. Our results show that PODXL is a bona fide target of p53-mediated transcriptional repression while being positively regulated by WT1. We propose that inappropriate expression of PODXL due to changes in WT1 and/or p53 activity may contribute to Wilms tumorigenesis.

The complex life of WT1

The Wilms' tumour gene, WT1, encodes a zinc-finger transcription factor that is inactivated in a subset of Wilms' tumours. Mutation analysis in human patients and genetic experiments in mice have revealed that WT1 has a role much wider than just tumour suppression. Alternative splicing, RNA editing, and the use of alternative translation initiation sites generate a multitude of isoforms, which seem to have overlapping but also distinct functions during embryonic development and the maintenance of organ function. Recently, mouse strains lacking the WT1(-KTS) or WT1(+KTS) splice variants of exon 9 were generated. More severe defects of kidneys and gonads are found in mice lacking the WT1(-KTS) variant. Animals lacking the WT1(+KTS) variant show disturbed podocyte function and male-to-female sex reversal. Alternative splicing of exon 5, however, might not modify WT1 function dramatically. Recently, it was also described that reduction of WT1 levels in the kidney results in glomerulosclerosis and upregulation of WT1 in the heart might contribute to neovascularization after infarction.

Role of homeobox genes in normal mammary gland development and breast tumorigenesis

The role of homeobox-containing genes in embryogenesis and organogenesis is well documented. Also, a sizeable body of evidence has accumulated and supports the fact that homeobox genes, when dysregulated, are involved in tumorigenesis. However, the precise mechanisms of homeobox gene functions are largely unknown. The mammary gland, in which most maturation occurs postnatally, provides an ideal model for studying the functions of homeobox genes in both development and tumorigenesis. The expression of many homeobox genes has been detected in both normal mammary gland and neoplastic breast tissues. In the normal mammary gland, the expression of homeobox genes is coordinately regulated by hormone and extracellular matrix (ECM) and other unknown factors in a spatial and temporal manner in both stromal and epithelial cells. Animals with misexpressed homeobox genes displayed different extents of defects in ductal proliferation, side branching, and alveoli formation, implying that homeobox genes are important for normal mammary gland development. Recent studies of homeobox genes in breast cancer cells and primary tumors indicate that they may also play a contributory or causal role in tumorigenesis by regulating the cell cycle, apoptosis, angiogenesis, and/or metastasis.