Overexpression of the Wilms' tumor gene WT1 in de novo lung cancers

Wilms tumor gene product: sensitive and contextually specific marker of serous carcinomas of ovarian surface epithelial origin

Carcinomas of ovarian surface epithelial origin can arise from, and often present at, extraovarian sites. There are few available markers for the positive identification of carcinomas of ovarian surface epithelial origin, which might aid in distinguishing them from metastatic carcinomas, such as of breast, colon, or lung origin. Recently, the Wilms tumor gene product (WT-1) has been shown to be expressed in ovarian surface and mesothelial epithelium. We tested the hypothesis that WT-1 would be a sensitive and specific marker of ovarian surface epithelium carcinomas. An archived series of 116 ovarian carcinomas (57 serous [43 ovarian, 14 extraovarian], 31 mucinous, 15 clear cell, 13 endometrioid), 118 breast carcinomas, 46 colonic carcinomas, and 45 nonsmall cell lung cancers were selected. A polyclonal antibody to the WT-1 gene product was applied to deparaffinized, formalin-fixed tissue sections after epitope retrieval. Fifty-two of 57 (93%) serous carcinomas of ovarian surface epithelial origin were WT-1-positive, in a nuclear pattern, with virtually all the tumor cell population positive in the majority of cases. None of the mucinous, clear cell, or endometrioid ovarian cancers were positive, and only 8 of 118 breast, 0 of 46 colonic, and 0 of 45 lung nonsmall cell carcinomas were WT-1-positive. These findings demonstrate that WT-1 is a highly sensitive and specific marker of serous carcinomas of ovarian surface epithelial origin (both ovarian and extraovarian). These results also contradict recent reports demonstrating WT-1 expression in both breast and lung carcinomas.

Overexpression of the Wilms' tumor gene W T1 in primary astrocytic tumors

Expression of the Wilms' tumor gene W T1 in primary astrocytic tumors was examined using a quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) or immunohistochemistry. Real-time RT-PCR showed that W T1 mRNA was expressed at various levels in all of the 25 astrocytic tumors examined. Immunohistochemical analysis showed that W T1 protein was expressed in 5 of 6 low-grade astrocytic tumors (grade I-II) and all of 18 high-grade ones (grade III-IV), and that expression levels of W T1 protein in high-grade tumors were significantly higher than those in low-grade ones. W T1 protein was not detected in the normal glial cells contained in the tumor specimens. Furthermore, treatment with W T1 antisense oligomers specifically inhibited growth of glioblastoma cell lines, U87-MG, A172, and T-98G. These results may indicate that the W T1 gene plays an important role in tumorigenesis of primary astrocytic tumors.

Induction of WT1 (Wilms' tumor gene)-specific cytotoxic T lymphocytes by WT1 peptide vaccine and the resultant cancer regression

The Wilms' tumor gene WT1 is overexpressed in leukemias and various types of solid tumors, and the WT1 protein was demonstrated to be an attractive target antigen for immunotherapy against these malignancies. Here, we report the outcome of a phase I clinical study of WT1 peptide-based immunotherapy for patients with breast or lung cancer, myelodysplastic syndrome, or acute myeloid leukemia. Patients were intradermally injected with an HLA-A*2402-restricted, natural, or modified 9-mer WT1 peptide emulsified with Montanide ISA51 adjuvant at 0.3, 1.0, or 3.0 mg per body at 2-week intervals, with toxicity and clinical and immunological responses as the principal endpoints. Twenty-six patients received one or more WT1 vaccinations, and 18 of the 26 patients completed WT1 vaccination protocol with three or more injections of WT1 peptides. Toxicity consisted only of local erythema at the WT1 vaccine injection sites in patients with breast or lung cancer or acute myeloid leukemia with adequate normal hematopoiesis, whereas severe leukocytopenia occurred in patients with myelodysplastic syndrome with abnormal hematopoiesis derived from WT1-expressing, transformed hematopoietic stem cells. Twelve of the 20 patients for whom the efficacy of WT1 vaccination could be assessed showed clinical responses such as reduction in leukemic blast cells or tumor sizes and/or tumor markers. A clear correlation was observed between an increase in the frequencies of WT1-specific cytotoxic T lymphocytes after WT1 vaccination and clinical responses. It was therefore demonstrated that WT1 vaccination could induce WT1-specific cytotoxic T lymphocytes and result in cancer regression without damage to normal tissues.

Morphologic and Molecular Characterization of Renal Cell Carcinoma in Children and Young Adults

A new WHO classification of renal cell carcinoma has been introduced in 2004. This classification includes the recently described renal cell carcinomas with the ASPL-TFE3 gene fusion and carcinomas with a PRCC-TFE3 gene fusion. Collectively, these tumors have been termed Xp11.2 or TFE3 translocation carcinomas, which primarily occur in children and young adults. To further study the characteristics of renal cell carcinoma in young patients and to determine their genetic background, 41 renal cell carcinomas of patients younger than 22 years were morphologically and genetically characterized. Loss of heterozygosity analysis of the von Hippel-Lindau gene region and screening for VHL gene mutations by direct sequencing were performed in 20 tumors. TFE3 protein overexpression, which correlates with the presence of a TFE3 gene fusion, was assessed by immunohistochemistry. Applying the new WHO classification for renal cell carcinoma, there were 6 clear cell (15%), 9 papillary (22%), 2 chromophobe, and 2 collecting duct carcinomas. Eight carcinomas showed translocation carcinoma morphology (20%). One carcinoma occurred 4 years after a neuroblastoma. Thirteen tumors could not be assigned to types specified by the new WHO classification: 10 were grouped as unclassified (24%), including a unique renal cell carcinoma with prominently vacuolated cytoplasm and WT1 expression. Three carcinomas occurred in combination with nephroblastoma. Molecular analysis revealed deletions at 3p25-26 in one translocation carcinoma, one chromophobe renal cell carcinoma, and one papillary renal cell carcinoma. There were no VHL mutations. Nuclear TFE3 overexpression was detected in 6 renal cell carcinomas, all of which showed areas with voluminous cytoplasm and foci of papillary architecture, consistent with a translocation carcinoma phenotype. The large proportion of TFE3 "translocation" carcinomas and "unclassified" carcinomas in the first two decades of life demonstrates that renal cell carcinomas in young patients contain genetically and phenotypically distinct tumors with further potential for novel renal cell carcinoma subtypes. The far lower frequency of clear cell carcinomas and VHL alterations compared with adults suggests that renal cell carcinomas in young patients have a unique genetic background.

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.

Overexpression of the Wilms' tumor gene WT1 in pancreatic ductal adenocarcinoma

The expression of the Wilms' tumor gene WT1 was examined by immunohistochemistry in 40 cases of pancreatic ductal adenocarcinoma. WT1 protein was expressed in 30 (75%) of the 40 pancreatic ductal adenocarcinomas, but not in the remaining 10 (25%). In normal pancreatic ductal cells, WT1 protein was undetectable. No correlations between WT1 expression and clinicopathological parameters such as age, sex, T or N stage, tumor location, and tumor differentiation were observed. Treatment with WT1 antisense oligomers significantly inhibited the growth of five human pancreatic cancer cell lines, PSN1, MiaPaCa2, ASPC1, BxPC3, and PCI6, expressing the WT1 gene. These results indicate an important role of the WT1 gene in the tumorigenesis of pancreatic ductal adenocarcinoma expressing WT1 and provide a rationale for new treatment strategies to treat pancreatic ductal adenocarcinoma by targeting the WT1 gene and its product.

WT1 is a tumor-associated antigen in colon cancer that can be recognized by in vitro stimulated cytotoxic T cells

The Wilms' tumor suppressor gene (WT1) has been shown to be overexpressed in acute and chronic leukemias and in a variety of solid human malignancies, including cancers of the breast and lung. In our present study, we investigated the potential role of WT1 gene in human colon cancer. WT1 mRNA and protein expression was analyzed in a panel of human colon cancer cell lines and primary colon carcinomas by RT-PCR and Western blot analysis, respectively. A mutational screen of WT1' zinc-finger region was carried out by sequence analysis. Finally, using peptide-stimulated cytotoxic T cells it was investigated whether WT1-expressing colon tumor cells are a potential target for antigen-specific immunotherapy. Medium to high abundant levels of WT1 mRNA were detected by RT-PCR in 10 of 12 (83%) colon cell lines and by quantitative, real-time RT-PCR in 13 of 15 (87%) primary tumors, whereas only very low levels of expression were found in 2 primary tumors. Interestingly, however, low levels of WT1 mRNA were also detected in all samples derived from normal colon mucosa. When RT-PCR products were examined by sequence analysis, both +KTS and -KTS splice isoforms but no zinc-finger mutations were found, suggesting that the wild-type form of the WT1 gene is expressed. To determine whether the WT1 protein can serve as a target antigen for immunotherapy, 2 HLA-A2.1-restricted WT1 peptides (Db126 and WH187) were used for the in vitro induction of WT1-specific cytotoxic T lymphocytes (CTLs). The WH187-specific CTLs not only lysed target cells pulsed exogenously with cognate peptide but also WT1-expressing colon tumor cells in a HLA-restricted manner. These findings identify the WT1 protein as an attractive target for the development of antigen-specific immunotherapy in human colon cancer.

Overexpression of the Wilms' tumor gene WT1 in colorectal adenocarcinoma

Expression of the Wilms' tumor gene WT1 was examined in 59 cases of colorectal adenocarcinoma to examine the involvement of WT1 in tumorigenesis. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) showed that WT1 mRNA was expressed in the range from 7.2 x 10(-5) to 4.9 x 10(-1) levels (WT1 expression level in K562 leukemic cells was defined as 1.0) in all (100%) of the 28 cases of colorectal adenocarcinoma examined, and that the WT1 mRNA expression levels were higher in 20 (71%) of the 28 cases compared to those of normal-appearing mucosal tissues examined. Immunohistochemical analysis using an anti-WT1 antibody was performed on 46 cases of colorectal adenocarcinoma (15 of the 28 cases with WT1 mRNA expression and 31 newly collected cases), and the expression of WT1 protein was detected in 41 (89%) of the 46 cases. The direct sequencing analysis of the WT1 genomic DNA showed no mutations in any of the 10 exons of the WT1 gene in any of 5 different colorectal adenocarcinomas. These results may indicate an important role of the wild-type WT1 gene in tumorigenesis of colorectal adenocarcinoma.

Overexpression of the Wilms' tumor gene WT1 in primary thyroid cancer

The expression levels of the Wilms' tumor gene WT1 were examined in 34 primary thyroid cancers (24 papillary, 5 follicular, 1 anaplastic, and 4 medullary carcinomas), 17 thyroid follicular adenomas, and 6 normal-appearing thyroid tissues using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). In 33 of 34 thyroid cancers, the WT1 mRNA was expressed at levels ranging from 5.0 x 10 (-5) to 8.3 x 10 (-2) levels (WT1 expression level in K562 leukemic cells was defined as 1.0). The WT1 mRNA expression levels were significantly higher than those in either thyroid follicular adenomas (P < 0.001) or normal-appearing thyroid tissues (P < 0.01). Immunohistochemical analysis confirmed the expression of WT1 protein in 20 of 21 thyroid cancers with WT1 mRNA expression. WT1 protein was also detected in 6 of 7 follicular adenomas with WT1 mRNA expression. However, the intensity of staining of WT1 protein in adenoma cells was weaker than that in cancer cells and its expression was restricted to approximately 30-80% of adenoma cells in the tumors examined. The direct sequencing analysis of the WT1 genomic DNA showed no mutations in any of the 10 exons of the WT1 gene in all of the 9 different thyroid cancers. These findings indicate an important role of the wild-type WT1 gene in the tumorigenesis of primary thyroid cancer.

Wilms tumor gene peptide-based immunotherapy for patients with overt leukemia from myelodysplastic syndrome (MDS) or MDS with myelofibrosis

The Wilms tumor gene, WT1, is overexpressed not only in leukemias and myelodysplastic syndrome (MDS) but also in various types of solid tumors, including lung and breast cancer, and the WT1 protein is a tumor antigen for these malignancies. In clinical trials of WT1 peptide-based cancer immunotherapy, patients with overt leukemia from MDS or MDS with myelofibrosis were injected intradermally with 0.3 mg of an HLA-A*2402-restricted, 9-mer WT1 peptide emulsified with Montanide ISA51 adjuvant. Only a single dose of WT1 vaccination resulted in an increase in WT1-specific cytotoxic T-lymphocytes, which was followed by a rapid reduction in leukemic blast cells. Severe leukopenia and local erythema at the injection sites of WT1 peptide were observed as adverse effects. These results have provided us with the first clinical evidence suggesting that WT1 peptide-based immunotherapy is an attractive treatment for patients with leukemias or MDS.

The lck promoter-driven expression of the Wilms tumor gene WT1 blocks intrathymic differentiation of T-lineage cells

In the thymi of WT1-transgenic (Tg) mice with the 17AA+/KTS- spliced form of the Wilms tumor gene WT1 driven by the lck promoter, the frequencies of CD4-CD8- double-negative (DN) thymocytes were significantly increased relative to those in normal littermates. Of the 4 subsets of CD4-CD8- DN thymocytes, the DN1 (CD44+CD25-) subset increased in both frequency and absolute cell number, whereas the DN2 (CD44+CD25+) and DN3 (CD44-CD25+) subsets decreased, indicating the blocking of thymocyte differentiation from the DN1 to the DN2 subsets. Furthermore, CD4-CD8+ T-cell receptor (TCR) -gammadelta T-cells increased in both frequency and absolute cell number in the spleen and peripheral blood of the WT1-Tg mice relative to those of normal littermates. The CD8 molecules of these CD4-CD8+ TCRgammadelta T-cells were CD8alphabeta, suggesting that they originated from the thymus. These results are the first direct evidence demonstrating that the WT1 gene is involved in the development and differentiation of T-lineage cells.

Overexpression of the Wilms' tumor gene WT1 in head and neck squamous cell carcinoma

The expression levels of the Wilms' tumor gene WT1 were examined in 56 cases of head and neck squamous cell carcinoma (HNSCC) using quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). They included 4 cases of floor of mouth, 9 of gingiva, 25 of tongue, 10 of oropharynx, 3 of hypopharynx, and 5 larynx squamous cell carcinoma (SCC). All (100%) of 4 cases of floor of mouth, 5 (56%) of 9 gingiva, 17 (68%) of 25 tongue, 8 (80%) of 10 oropharynx, all (100%) of 3 hypopharynx, and all (100%) of 5 larynx SCC overexpressed the WT1 gene in the range of 3.07 x 10(-4)-8.60 x 10(-1) levels (the WT1 expression level in K562 leukemic cells was defined as 1.0). Thus, 42 (75%) out of 56 cases of HNSCC overexpressed the WT1 gene. The high expression level of the WT1 gene significantly correlated with poor histological tumor differentiation and high tumor stage of HNSCC. Immunohistochemical analysis confirmed the expression of WT1 protein in 6 cases (one floor of mouth, 2 tongue, 2 oropharynx, and one larynx SCC) with overexpression of the WT1 gene. The direct sequencing analysis of the WT1 genomic DNA showed no mutations in any of 10 exons of the WT1 gene in 5 different HNSCC. These findings suggest an important role of the wild-type WT1 gene in the tumorigenesis of HNSCC.

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.

Overexpression of the Wilms' tumor gene WT1 in human bone and soft-tissue sarcomas

The expression levels of the Wilms' tumor gene WT1 were examined in 36 cases of various types of human bone and soft-tissue sarcomas using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). They included 12 malignant fibrous histiocytomas (MFH), 3 malignant peripheral nerve sheath tumors (MPNST), 6 synovial sarcomas (SyS), 4 myxoid liposarcomas (MyLS), one angiosarcoma (AGS), one clear cell sarcoma (CCS), and 9 osteosarcomas (OS). Eleven (92%) of 12 MFH, 2 (67%) of 3 MPNST, all (100%) of 6 SyS, 2 (50%) of 4 MyLS, one AGS, one CCS, and 5 (56%) of 9 OS cases overexpressed WT1 in the range of 1.4 x 10(-3)-3.9 x 10(-1) levels (WT1 expression level in K562 leukemic cells was defined as 1.0). Thus, 28 (78%) out of 36 various types of human bone and soft-tissue sarcomas overexpressed the WT1 gene. Immunohistochemical analysis showed positive staining for WT1 protein in all of 4 cases (one case each of MFH, MyLS, AGS and OS) with WT1 gene overexpression detected by RT-PCR analysis, demonstrating clearly that WT1 was expressed at the protein level in various types of human bone and soft-tissue sarcomas. The direct sequencing analysis of the WT1 genomic DNA showed no mutations in any of 10 exons of the WT1 gene in 8 different sarcoma samples (3 MFH, one SyS, one MyLS, one AGS, and 2 OS). The present study demonstrates that various types of human bone and soft-tissue sarcomas frequently overexpress the wild-type WT1 gene, suggesting an important role of the wild-type WT1 gene in tumorigenesis of various types of human bone and soft-tissue sarcomas.