Expression Patterns of WT1 and PRAME in Acute Myeloid Leukemia Patients and Their Usefulness for Monitoring Minimal Residual Disease

Both WT1 and PRAME are highly expressed in acute myeloid leukemia (AML) patients. To assess the efficacy of their simultaneous detection for the purpose of monitoring minimal residual disease (MRD), we used real-time quantitative RT-PCR to quantify both WT1 and PRAME transcript levels in the bone marrow of 204 newly diagnosed AML patients, and 21 patients were serially monitored for a median of 11 months. The 22 normal bone marrow samples which served as controls collectively expressed low levels of WT1 and PRAME. An increase of >1-log over the upper limit of normal bone marrow was defined as positive. The positive rates of WT1 and PRAME for all patients were 79.2% and 55.4%, respectively. For the 108 patients lacking a specific fusion gene, the positive rate of WT1 was significantly higher than that of PRAME (76.9% vs. 35.2%, P<0.001). PRAME was positive in 9/25 WT1 (-) patients and the log increase of PRAME was higher than that of WT1 in 12/83 WT1 (+) patients. Dynamic patterns of WT1 and PRAME during follow-up showed that a consistent elevation or a rise over time to exceed the normal range predicted clinical relapse. The exception was that one patient's WT1 significantly decreased at relapse compared to diagnosis. Therefore, a simultaneous detection of WT1 and PRAME might not only provide AML patients with either a positive or a more sensitive molecular marker for MRD monitoring. Moreover, it might also avoid false negativity in the case of expression alteration.