Wilms' tumour gene (wt1) expression at diagnosis has no prognostic relevance in childhood acute lymphoblastic leukaemia treated by an intensive chemotherapy protocol

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Abstract
Expression of the Wilms' tumour gene (wt1) has been demonstrated in a large proportion of human acute leukaemias and is thought to play a role in leukaemogenesis. Recent observations in adult patients with acute leukaemia suggest that wt1 gene expression is a poor prognostic factor. In childhood acute leukaemia, the clinical role of wt1 gene expression has not been established. We have therefore investigated bone marrow samples from 50 children with acute lymphocytic leukaemia at the time of diagnosis for the presence of wt1 transcripts to determine whether wt1 gene expression is associated with specific characteristics of leukaemic cells and whether it is predictive of response to treatment. All patients were treated according to the ALL‐BFM 90 protocol. The median observation time was 30 months. Wt1 transcripts were detected by RT‐PCR in 60% of the diagnostic samples. Wt1 PCR positive patients showed a higher median leukocyte and peripheral blast cell count than wt1 negative patients. High and intermediate risk patients more frequently displayed wt1 transcripts than low risk patients. No correlation between wt1 gene expression and FAB type, immunophenotype, co‐expression of myeloid antigens or karyotype has been observed. Furthermore, there was no correlation between wt1 gene expression at diagnosis and achievement of complete remission (CR) and no difference in disease‐free survival (DFS) or overall survival (OS) between wt1 positive and negative patients (p >0.1). These data indicate that (1) wt1 gene expression at diagnosis is detected more frequently in patients with high leukocyte and peripheral blast cell counts, but is not associated with specific characteristics of leukaemic cells, (2) wt1 gene expression is not an independent prognostic factor for CR, DFS or OS in childhood ALL treated by an intensive therapy protocol.