Wilm's Tumor 1 Gene Expression Is a Useful Marker for Minimal Residual Disease in Acute Myeloid Leukemia.

Abstract

One of the difficulties in managing patients with acute myeloid leukemia (AML) is the detection of minimal residual disease. Only a fraction of AML patients have a distinct phenotype on flow cytometry or a genetic abnormality which can be followed as a sensitive marker for minimal residual disease (MRD). The Wilm's tumor - 1 gene (WT1) is overexpressed in leukemic blasts, but not in normal blood or marrow cells, and thus can be used as a marker for MRD in leukemia patients who otherwise do not have a characteristic immunophenotypic or molecular marker that can be monitored. We prospectively measured serial peripheral blood WT1 levels by RQ-PCR in 54 patients with AML. Of the 54 patients, 23 patients were newly diagnosed. The remaining 31 patients were in complete remission prior to a planned allogeneic transplant. Subsequent WT1 levels were obtained during routine evaluation both during and up to three years after completion of either chemotherapy and/or transplant. Using regression analysis, we found that a normalized WT1 level greater than 10−4 (as compared to a level of 1 in K562 cells) indicates a higher likelihood of the patient having active leukemia with a sensitivity of 87.5% and a specificity of 89.1%. The positive and negative predictive values are 71.19% and 95.89% respectively. We also compared WT1 levels with peripheral blood and bone marrow blasts to determine whether a correlation existed. We found a strong correlation between WT1 expression and bone marrow blasts with a correlation coefficient of 0.77 (p< 0.0001). A weak correlation was found with peripheral blood blast count (correlation coefficient = 0.35, p<0.0001). Our data implies WT1 can be a useful marker for minimal residual disease in patients with acute myeloid leukemia, especially in patients who do not have an unusual phenotype or molecular marker to monitor MRD.