Expression of the gene Wilms tumor 1 (WT1) has been suggested as a marker of minimal residual disease in acute myeloid leukemia (AML), but literature data are not without controversy. Our aim was to assess the presence, magnitude and temporal changes of WT1 expression as prognostic factors. 60 AML patients were followed until death or the end of the 6-year observation period. Blood samples were taken at diagnosis, post-induction, during remission and in case of a relapse. Using quantitative real-time PCR, we determined WT1 expression from each sample, normalized it against the endogenous control gene glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and classified samples as negative, moderately positive or highly positive. We divided the patients into groups based on detected WT1 expression values, illustrated overall and disease-free survival on Kaplan-Meier curves, and compared differences between each group by the logrank test. Disappearance of WT1-positivity during chemotherapy had a favorable effect on survival. Interestingly, no difference was seen between the survivals of WT1-positive subgroups that expressed moderate or high levels of WT1 mRNA. A 1-log decrease in WT1 expression without becoming negative did not affect prognosis, either. Our results suggest that defining a cut-off value for WT1-positivity, rather than just using logarithmic figures of changes in gene expression, might have prognostic use in post-induction AML patients. We encourage further, larger-scale studies.
Keywords: Acute myeloid leukemia; Overexpression; Quantitative real-time PCR; WT1 gene.