The nuclear WT1 protein can be found in blasts of approximately 50–60% of acute leukaemia patients at diagnosis. Conversely, WT1 is only transiently expressed in normal haemopoiesis. Therefore detection of the submicroscopic levels of leukaemic cells (MRD) in peripheral blood samples from children with acute lymphoblastic leukaemia (ALL) using WT1 as a marker should have clinical importance. We aimed to develop a quantitative method based on the real-time quantitative reverse transcriptase PCR (RQ–PCR) in order to monitor the WT1 level in children with ALL and assess its prognostic importance.
Fourteen newly diagnosed ALL children were included in this study. The peripheral blood samples were collected before induction, at the second week of induction, at the start of consolidation and beginning of the maintenance phase of chemotherapy. The last blood sample was collected from each patient at random 2–6 months after the maintenance phase started. For real-time reverse transcriptase PCR we have used the LightCycler device, SYBR Green I dye and WT1 primers with 90 bp PCR products.
The proportion of patients with detectable WT1 was 92% at diagnosis and 42% at the second week of therapy, 38% at the start of consolidation and 0% at the beginning of maintenance. WT1 could not be detected in any of the last samples. The absence of WT1 showed accordance with the clinical course of patients. CQ–PCR and RQ–PCR results were correlated together.
These preliminary results indicate that real time PCR can be employed to monitor MRD in leukaemic patients during chemotherapy.