Monitoring of minimal residual disease by quantitative WT1 gene expression following reduced intensity conditioning allogeneic stem cell transplantation in acute myeloid leukemia.
WT1 is well-known to be a panleukemic marker that is expressed in 90% of acute myeloid leukemias (AML). Quantification of WT gene expression in bone marrow (BM) samples may be useful as a marker of minimal residual disease (MRD) during and after treatment for early prediction of relapse. We evaluated the validity of this AML-MRD marker after reduced intensity conditioning (RIC) allogeneic stem cell transplantation (SCT). The quantitative assessment of WT1 expression by real-time quantitative PCR (RQ-PCR) was measured in 25 patients (pts) with AML at diagnosis, at the time of RIC-SCT and after transplant at precise time points. All pts showed high WT1 levels at diagnosis with a mean of 4895 (SD 4462) and a median of 3679 (range 454-16,853) copies WT1/10(4) ABL. At transplant, 18/25 pts (72%) were in complete cytologic remission (CcR) and 7/25 (28%) had refractory AML. At the pre-SCT evaluation, BM samples from pts transplanted in CcR showed significantly lower WT1 expression levels compared to the samples from pts with refractory AML (p = 0.002). Median follow-up after RIC-SCT was 18 months (range 2-54). On 18 pts transplanted in CcR, those (17/18) who maintained CcR after RIC-SCT displayed a WT1 copy number persistently low during all the follow-up period. In patients who received RIC-SCT with active disease obtaining a sustained CcR after transplant (3/25), WT1 levels decreased to normal range in the first two months after RIC-SCT and remained low through the entire study period. All pts who relapsed after RIC-SCT (4/25) had a high WT1 copy number before the cytologic relapse. In 50% of these cases, an increase in WT1 expression was documented before molecular chimerism decreasing. With this experience, taking into account the limited number of pts, we confirmed a concordance between WT1 expression levels (measured by RQ-PCR at precise and sequential time points) and status of AML before and after RIC-SCT and we found a concordance between WT1 expression levels and hematopoietic chimerism status. Our data suggest that, in the RIC-SCT setting, the sequential and quantitative analysis of WT1 may be useful as a leukemia marker for monitoring MRD and as a predictor of overt AML cytologic relapse.
Candoni
Anna
A
Division of Hematology and Bone Marrow Transplantation, Department of Medical and Morphologic Research, University of Udine, Udine, Italy. candoni.anna@aoud.sanita.fvg.it
Toffoletti
Eleonora
E
Gallina
Roberto
R
Simeone
Erica
E
Chiozzotto
Marianna
M
Volpetti
Stefano
S
Fanin
Renato
R
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis* / Q000235:genetics* / Q000601:surgery; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000175:diagnosis* / Q000235:genetics* / Q000601:surgery; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D033581:Stem Cell Transplantation; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous; D025721:WT1 Proteins / Q000235:genetics*; D055815:Young Adult
D012333:RNA, Messenger; D012334:RNA, Neoplasm; D025721:WT1 Proteins