Detection by monoclonal antibodies of the Wilms' tumor (WT1) nuclear protein in patients with acute leukemia

Abstract

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...

The Expression of WT1 in the Differentiation of Rhabdomyosarcoma from Other Pediatric Small Round Blue Cell Tumors

“…In fact, a similar strong cytoplasmic staining pattern has been previously described in two nephroblastomas within areas of desmin positivity using the same antibody (31). In contrast, previous immunohistochemical reports also described a weak cytoplasmic positivity with WT1 (C-terminus) antibodies in mesotheliomas (23,25), leukemias (20), and SRBCT (24) raising the possibility of an artifact of fixation (24,31,54). Some of the tumors we examined (neuroblastomas, DSRCT, lymphomas, and Wilms' tumors) had a weak cytoplasmic reactivity and nonspecific staining could not be excluded.…”

“…However, an activator or oncogenic behavior may be acquired by missense mutations. WT1 expression has been demonstrated in hema-tological malignancies (17)(18)(19)(20)(21)(22), mesothelial-derived neoplasms (23)(24)(25)(26)(27), breast cancer (28,29), genitourinary tumors (30,31), and small round blue cell tumors (SRBCT; 24,27,[32][33][34]. Recent studies have evaluated the possible role of peripheral blood RNA (18,19), serum antibodies (35), and immunotherapy (36,37) in the diagnosis, monitoring, and treatment of WT1-positive tumors.…”

Quantitative real-time RT-PCR detects elevated Wilms tumor gene (WT1) expression in autologous blood stem cell preparations (PBSCs) from acute myeloid leukemia (AML) patients indicating contamination with leukemic blasts

“…4 Blasts of the majority of acute myeloid and lymphoid leukemia patients express WT1, whereas patients with reactive changes to their bone marrow due to infections or malignancies show no significant WT1 expression. 5,6 WT1 expression is not detectable in patients with leukemic low-grade non-Hodgkin's lymphoma (NHL) or in patients with chronic myeloid leukemia in chronic phase. Stem cell preparations of solid cancer patients express WT1 at low levels, if at all.…”

Prognostic significance of WT1 gene expression at diagnosis in adult de novo acute myeloid leukemia

“…Several row samples of 125 patients with de novo acute myeloid leukeauthors [10][11][12][13][14][15][16][17] have shown that in the majority of AML cases mia at diagnosis by two-step RT-PCR. The sensitivity of the WT1 is expressed.…”