The WT1 gene encodes a transcriptional regulator which during embryogenesis is involved in growth control and differentiation of diverse tissues. It is also expressed in few human malignancies, including acute leukemia. We tested 3 different monoclonal antibodies (MAbs H2, H7, HC17) and the polyvalent serum WTC-19 for WT1 protein detection in mononuclear cell (MNC) preparations of 104 newly diagnosed acute leukemia patients. Using RT-PCR, these MNC preparations were also analyzed for WT1 gene expression. The Wilms' tumor 1 gene (WT1) encodes a transcription factor containing a glutamine-and proline-rich regulatory region at the amino-terminus and 4 DNA-binding zinc finger motifs at the carboxy-terminus that bind to the EGR1 DNA consensus sequence (Gessler et al., 1990;Call et al., 1990). As a result of differential mRNA splicing, 4 different WT1 mRNA and protein species are expressed, exhibiting different DNA-binding specificities (Bickmore et al., 1992). Binding of the WT1 protein to target gene promoters results in transcriptional suppression or activation of growth factor genes, depending on promoter structure and the presence of other transcriptional regulators such as p53 (Maheswaran et al., 1993;Wang et al., 1993;Drummond et al., 1992;Harrington et al., 1993). As a result, the WT1 protein is involved in growth control and differentiation of various cell types. Its possible role in growth regulation is further supported by the finding that over-expression of the WT1 gene in NIH 3T3 cells at early or mid-G 1 phase reduces cellular proliferation by blocking cell cycle progression into S phase (Kudoh et al., 1995). During embryogenesis, the WT1 gene is expressed in various tissues, including kidney, mesothelial cells, spleen, gonads and the central nervous system (Armstrong et al., 1993). After birth, WT1 gene expression is restricted to select tissues, including Sertoli cells, decidua cells of the uterus and mesothelial cells. In contrast, a variety of malignant tissues express WT1 mRNA, including Wilms' tumor, ovarian cancer, mesothelioma, melanoma, lung cancer cell lines and acute leukemias (Inoue et al., 1994;Brieger et al., 1994;Menssen et al., 1995). Interestingly, WT1 gene mutations have been rarely described in these malignancies and in sporadic Wilms' tumors, whereas in the hereditary WAGR and Denys-Drash syndromes germ-line WT1 gene mutations were frequently found (Coppes et al., 1993).Using RT-PCR, we (Menssen et al., 1995) and others (Inoue et al., 1994;Brieger et al., 1994) have observed WT1 gene expression in most acute leukemia cell preparations of lymphoid and myeloid differentiation. There are contradictory results on the WT1 gene expression in normal hematopoietic progenitor cells, probably due to different sensitivities of the various RT-PCR protocols used to detect the WT1 gene transcripts. In summary, normal hematopoietic progenitor cells did not express the WT1 gene (Menssen et al., 1995;Brieger et al., 1995), or the expression was found in substantially lower amounts compared with leukem...

No abstract

Summary. In patients presenting with immature eosinophilic precursors it is notoriously difficult to distinguish acute eosinophilic leukaemia (EoL) from the benign idiopathic hypereosinophilic syndrome (HES), based on morphological, cytochemical and immunophenotyping criteria, alone. Cytogenetic analysis or fluorescence in situ hybridization (FISH) can help in discriminating between these rare haematological disorders, but often treatment decisions cannot wait for the results of these time-consuming techniques. Recently, we and others found Wilms' tumour (WT1) gene expression to be increased in virtually all patients with acute leukaemias, whereas normal haemopoietic progenitors express the WT1 gene at much lower levels or not at all. To determine whether detection of WT1 gene expression is useful to distinguish EoL from HES patients, we analysed, by RT-PCR, bone marrow or blood mononuclear cells from EoL (n¼3), HES (n¼ 3) and reactive eosinophilia patients (n¼ 4) for WT1 gene expression. Using our WT1-RT-PCR protocol, we found WT1 gene expression to be restricted to EoL patients. By detecting WT1 mRNA transcripts in the cerebrospinal fluid using RT-PCR, we were also able to diagnose isolated CNS-relapsed leukaemia, initially confused with bacterial meningitis, in an EoL patient. In conclusion, we show that WT1-RT-PCR is a powerful complementary diagnostic tool to distinguish acute eosinophilic leukaemia from the hypereosinophilic syndromes. This observation needs confirmation in a larger series of EoL and HES patients.