The Wilms' tumor gene is frequently expressed in acute myeloblastic leukemias and may provide a marker for residual blast cells detectable by PCR

Background: The tumor suppressor gene wt-1 was isolated by cytogenetic deletion analysis of patients with Wilms' tumor (wt-1). This gene encodes for a zinc finger DNA-binding protein with transcription-repressing properties. During normal ontogenesis it is expressed in a time-and tissue-dependent manner mainly in the kidneys and gonads. Recently, the expression of wt-1 in acute leukemias (AL) was reported. Here we investigated the prognostic potential of wt-1 mRNA expression during the course of the disease using the PCR technique. Patients and methods: Blast cells from 83 patients with newly diagnosed AML and 20 AML patients during followup in complete remission were analyzed for wt-1 mRNA expression. Peripheral blood mononuclear cells (PBMNC) and bone marrow (BM) from healthy persons (n = 13) and sorted CD34-positive cells from normal donors (n = 4) were used as negative controls. Results: Wt-1-specific m-RNA was detectable in 67/83 (81%) patients with AML. Normal donors did not express wt-1 m-RNA but in 1/4 sorted CD34+ cell samples a weak amplified product was observed. After achieving cytological CR 14/20 studied patients lost wt-1 expression. In 7/8 patients in morphological CR the reappearance of wt-1 expression preceded relapse of the disease, in 1/8 patients wt-1 remained positive in CR. Response to therapy, disease free survival, overall survival and FAB-subtype did not correlate with wt-1 m-RNA expression in newly diagnosed AML before therapy. Conclusions: In the majority of acute leukemias wt-1 is expressed and probably blast cell-associated, at least in levels detectable by PCR. Wt-1 mRNA was detectable in bone marrow cells of AML patients in clinical CR. The results strongly suggest that the persistance or reappearance of wt-1 predicts relapse of the disease prior to morphological relapse.