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

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

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

Prognostic implications of mutations and expression of the Wilms tumor 1 (WT1) gene in adult acute T-lymphoblastic leukemia

BACKGROUND

The role of the Wilms tumor 1 gene (WT1) in acute leukemias has been underscored by mutations found in acute myeloid leukemia identifying patients with inferior survival. Furthermore, aberrant expression of WT1 in acute myeloid leukemia was associated with an increased risk of relapse. No larger studies have performed a combined approach including WT1 mutation and expression analyses in acute T-lymphoblastic leukemia.

DESIGN AND METHODS

We analyzed the WT1 mutations and the expression status in a total of 252 consecutive adult patients with newly diagnosed T-lymphoblastic leukemia, who were registered on the GMALL 06/99 and 07/03 protocols and had sufficient material available. The GMALL protocols included intensive chemotherapy as well as stem cell transplantation according to a risk-based model with indication for stem cell transplantation in first complete remission for early and mature T-lymphoblastic leukemia patients; patients with thymic T-lymphoblastic leukemia were allocated to a standard risk group and treated with intensive chemotherapy.

RESULTS

Twenty of the 238 patients analyzed had WT1 mutations (WT1mut) in exon 7. WT1mut cases were characterized by immature features such as an early immunophenotype and higher WT1 expression. In thymic T-lymphoblastic leukemia, WT1mut patients had an inferior relapse-free survival compared to WT1 wild-type patients. T-lymphoblastic leukemia patients with aberrant WT1 expression (high or negative) showed a higher relapse rate and an inferior outcome compared to patients with intermediate WT1 expression. In the standard risk group of thymic T-lymphoblastic leukemia, aberrant WT1 expression was predictive for an inferior relapse-free survival as compared to patients with intermediate expression. In multivariate analysis, WT1 expression was of independent prognostic significance for relapse-free survival.

CONCLUSIONS

WT1 mutations were associated with an inferior relapse-free survival in standard risk thymic T-lymphoblastic leukemia patients. Moreover, altered expression associated with inferior outcome also suggests a role of WT1 in T-lymphoblastic leukemia and the potential use of molecularly-based treatment stratification to improve outcome.

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.

Wilms' tumor gene WT1 17AA(-)/KTS(-) isoform induces morphological changes and promotes cell migration and invasion in vitro

The wild-type Wilms' tumor gene WT1 is overexpressed in human primary leukemia and in a wide variety of solid cancers. All of the four WT1 isoforms are expressed in primary cancers and each is considered to have a different function. However, the functions of each of the WT1 isoforms in cancer cells remain unclear. The present study demonstrated that constitutive expression of the WT1 17AA(-)/KTS(-) isoform induces morphological changes characterized by a small-sized cell shape in TYK-nu.CP-r (TYK) ovarian cancer cells. In the WT1 17AA(-)/KTS(-) isoform-transduced TYK cells, cell-substratum adhesion was suppressed, and cell migration and in vitro invasion were enhanced compared to that in mock vector-transduced TYK cells. Constitutive expression of the WT1 17AA(-)/KTS(-) isoform also induced morphological changes in five (one gastric, one esophageal, two breast and one fibrosarcoma) of eight cancer cell lines examined. No WT1 isoforms other than the WT1 17AA(-)/KTS(-) isoform induced the phenotypic changes. A decrease in alpha-actinin 1 and cofilin expression and an increase in gelsolin expression were observed in WT1 17AA(-)/KTS(-) isoform-transduced TYK cells. In contrast, co-expression of alpha-actinin 1 and cofilin or knockdown of gelsolin expression by small interfering RNA restored WT1 17AA(-)/KTS(-) isoform-transduced TYK cells to a phenotype that was comparable to that of the parent TYK cells. These results indicated that the WT1 17AA(-)/KTS(-) isoform exerted its oncogenic functions through modulation of cytoskeletal dynamics. The present results may provide a novel insight into the signaling pathway of the WT1 gene for its oncogenic functions.

Antiapoptotic function of 17AA(+)WT1 (Wilms' tumor gene) isoforms on the intrinsic apoptosis pathway

The WT1 gene is overexpressed in human primary leukemia and a wide variety of solid cancers. The WT1 gene is alternatively spliced at two sites, yielding four isoforms: 17AA(+)KTS(+), 17AA(+)KTS(-), 17AA(-)KTS(+), and 17AA(-)KTS(-). Here, we showed that 17AA(+)WT1-specific siRNA induced apoptosis in three WT1-expressing leukemia cell lines (K562, HL-60, and Kasumi-1), but not in WT1-non-expressing lymphoma cell line (Daudi). 17AA(+)WT1-specific siRNA activated caspase-3 and -9 in the intrinsic apoptosis pathway but not caspase-8 in the extrinsic one. On the other hand, 17AA(-)WT1-specific siRNA did not induce apoptosis in the three WT1-expressing cell lines. The apoptosis was associated with activation of proapoptotic Bax, which was activated upstream of the mitochondria. Constitutive expression of 17AA(+)WT1 isoforms inhibited apoptosis of K562 leukemia cells induced by apoptosis-inducing agents, etoposide and doxorubicin, through the protection of mitochondrial membrane damages, and DNA-binding zinc-finger region of 17AA(+)WT1 isoform was essential for the antiapoptotic functions. We further studied the gene(s) whose expression was altered by the expression of 17AA(+)WT1 isoforms and showed that the expression of proapoptotic Bak was decreased by the expression of 17AA(+)KTS(-)WT1 isoform. Taken together, these results indicated that 17AA(+)WT1 isoforms played antiapoptotic roles at some points upstream of the mitochondria in the intrinsic apoptosis pathway.

AML1-ETO rapidly induces acute myeloblastic leukemia in cooperation with the Wilms tumor gene, WT1

AML1-ETO, a chimeric gene frequently detected in acute myelogenous leukemia (AML), inhibits the differentiation of myeloid progenitors by suppressing genes associated with myeloid differentiation and increases the replating ability of clonogenic myeloid progenitors. However, AML1-ETO alone cannot induce AML and thus additional genetic events are required for the onset of AML. The Wilms tumor gene (WT1), which has been identified as the gene responsible for Wilms tumor, is expressed at high levels in almost all human leukemias. In this study, we have generated transgenic mice (WT1-Tg) that overexpress WT1 in hematopoietic cells to investigate the effects of WT1 on AML1-ETO-associated leukemogenesis. AML1-ETO-transduced bone marrow (BM) cells from WT1-Tg mice exhibited inhibition of myeloid differentiation at more immature stages and higher in vitro colony-forming ability compared with AML1-ETO-transduced BM cells from wild-type mice. Most importantly, all of the mice that received a transplant of AML1-ETO-transduced BM cells from the WT1-Tg mice rapidly developed AML. These results demonstrate that AML1-ETO may exert its leukemogenic function in cooperation with the expression of WT1.

The Wilms' tumor gene WT1 is a common marker of progenitor cells in fetal liver

It is well known that the Wilms' tumor gene WT1 plays an important role in cell proliferation and differentiation, and in organ development. In this study, to examine the role of the WT1 gene in lineage determination, fetal liver cells from LacZ-transgenic mice, in which WT1 expression was marked by the expression of the LacZ gene driven by WT1 promoter, were FACS-sorted according to LacZ expression of high (LacZ(++)) or undetectable (LacZ(-)) levels, which paralleled endogenous WT1 expression levels. LacZ(++) fetal liver cells were enriched by hepatocyte and endothelial progenitor cells. These results indicated that WT1 expression is a common marker of both hepatocyte and endothelial progenitors. These results also implied a role of the WT1 gene in lineage determination.

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.

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.