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

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 leuk aemogenesis. Recent observations in adult patients with acute leukaemia sug gest that wt1 gene expression is a poor prognostic factor. In childhood acu te leukaemia, the clinical role of wt1 gene expression has not been establi shed. We have therefore investigated bone marrow samples from 50 children w ith acute lymphocytic leukaemia at the time of diagnosis for the presence o f wt1 transcripts to determine whether wt1 gene expression is associated wi th specific characteristics of leukaemic cells and whether it is predictive of response to treatment. All patients were treated according to the ALL-B FM 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 t han wt1 negative patients. High and intermediate risk patients more frequen tly displayed wt1 transcripts than low risk patients. No correlation betwee n wt1 gene expression and FAB type, immunophenotype, co-expression of myelo id antigens or karyotype has been observed. Furthermore, there was no corre lation 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 da ta indicate that (1) wt1 gene expression at diagnosis is detected more freq uently in patients with high leukocyte and peripheral blast cell counts, bu t is not associated with specific characteristics of leukaemic cells, (2) w t1 gene expression is not an independent prognostic factor for CR, DFS or O S in childhood ALL treated by an intensive therapy protocol.