Quantitative assessment of WT1 gene expression after allogeneic stem cell transplantation is a useful tool for monitoring minimal residual disease in acute myeloid leukemia

Abstract

Evaluation of therapeutic efficacy in cancer patients requires a precise evaluation of minimal residual disease (MRD) after treatment. In hematological malignancies, and particularly in acute and chronic leukemia, definition of remission often requires not only a morphological analysis, but also lack of disease evidence at sub-microscopic level. This is highly important after a potentially curative approach as allogeneic hematopoietic stem cell transplant (HSCT), where early detection of relapse may lead to the modulation of AbstractIntroduction: WT1 overexpression is described in several oncological diseases including acute myeloid leukemia (AML). Quantification of WT1 in bone marrow samples may be useful as a marker of minimal residual disease (MRD) and may predict the relapse of AML after allogeneic hematopoietic stem cell transplant (HSCT). Methods and results: The quantitative expression of WT1 was measured in 38 AML patients (16 males and 22 females) at diagnosis, at the time of transplant and after the allogeneic HSCT (at precise time points). All cases showed high WT1 expression levels at diagnosis with a mean of 4189 (SD 3325) and a median of 3495 (range 454-13923) copies WT1 ⁄ 10 4 Abl. At transplant, 25 patients (66%) were in complete cytologic remission (CcR) and 13 (34%) had refractory or relapsed AML. Bone marrow samples from patients transplanted in CcR showed significantly lower WT1 expression levels during HSCT compared with the samples from patients with a relapsed or refractory AML (P = 0.004). After HSCT, a rapid decline in WT1 expression levels was observed in all patients who attained or maintained a condition of CcR. Six of 38 patients (13%) relapsed after HSCT and all of them had an increase in WT1 expression at ⁄ or before relapse. Five of these six patients died of leukemia and one was successfully reinduced with donor lymphocyte infusion (DLI) + chemotherapy with a rapid reduction of WT1 levels. Besides, we found a complete concordance between WT1 expression levels and other disease markers (when available). Conclusions: In our experience, there was a complete concordance between WT1 expression levels (measured by quantitative RT-PCR at precise time points) and status of AML before and after allogeneic HSCT. WT1 may be useful as a non-specific leukemia marker for monitoring MRD and as a predictor of AML clinical relapse. Based on these results, cases with increase of WT1 levels after HSCT and without graft vs. host disease may be candidate to discontinuation of immunosuppression and ⁄ or DLI therapy.

Predictive value of pretransplantation molecular minimal residual disease assessment by WT1 gene expression in FLT3-positive acute myeloid leukemia

“…It is well known that the WT1 gene is expressed in O90% of AML cases at diagnosis and it is stable over time; in addition, standardized quantitative methods for its expression detection are available [18]. Therefore, expression of WT1 is currently considered an adequate and reliable marker for monitoring molecular MRD in the postchemotherapy and post-SCT phase [18,35,36]. However, it is documented that, in the post-allo-SCT phase, the time to recurrence of this MRD marker relative to the subsequent cytological relapse can be variable and, if overexpression of WT1 is too close to cytological relapse, an early and effective preemptive therapy may be unworkable [36].…”

Monitoring of WT1 expression in PB and CD34+ donor chimerism of BM predicts early relapse in AML and MDS patients after hematopoietic cell transplantation with reduced-intensity conditioning

“…WT1 expression has already been shown to be a helpful marker in patients with AML after chemotherapy, 19,[21][22][23] after autologous 24 and after conventional allogeneic HCT. [25][26][27] In this analysis, the ability of different markers to predict relapse following allogeneic HCT with RIC was analyzed both alone and in combination. Peripheral blood (PB) cell WT1 expression levels quantified by real-time polymerase chain reaction (RT-PCR) were compared with the detection of diseasespecific (DS) markers by fluorescence in situ hybridization (FISH).…”

Wilms’ Tumor Gene (WT1) Expression and Minimal Residual Disease in Acute Myeloid Leukemia

“…In particular, post-transplant WT1 expression was the strongest predictor of outcome in multivariate analysis and was found to be a useful marker to select patients for preemptive immune intervention (DLI, tapering of immunosuppressive therapy). Comparable data were reported in a smaller number of patients monitored before and after transplant (21,22). However, discordant results on prognosis were obtained when MFC and WT1 levels were compared (40)(41)(42).…”

“…On the contrary, a greater agreement was found among groups that have used WT1 levels as a marker of minimal residual disease (MRD) in AML remission BMs (less than 5% of blast cells). In particular, WT1 expression has been shown to predict disease progression in AML patients treated with conventional chemotherapy (8)(9)(10)(15)(16)(17) and patients undergone allogeneic stem cell transplantation (allo-SCT) (18)(19)(20)(21)(22). Furthermore, when WT1 expression was compared with widely used techniques in monitoring MRD such as multiparameter flow cytometry (MFC) (23) or specific molecular targets such as fusion genes transcripts (PMLRARa, AML-ETO1, and CBFb-MYH11), comparable sensitivities were found in predicting the relapse in AML.…”