Wilms' tumor 1 mutation accumulated during therapy in acute myeloid leukemia: biological and clinical implications

Abstract

treatment, marrow blasts increased to 40%. FISH for BCR-ABL remained negative (also negative with the sorted CD34 þ / CD38 þ and CD34 þ /CD38-population) whereas À7 was present in 82% of the marrow cells. Quantitative PCR analysis was not performed. However, with nested RT-PCR using sets of BIOMED primers 2 the e1a2 transcript was still detectable suggesting presence of a very small and quiescent population of imatinib-resistant BCR-ABL-positive leukemic stem cells. There are only a few reports on the use of imatinib in Ph þ AML. 3-7 Most cases reporting molecular remission with imatinib had short follow-up and long-term clinical and molecular data is not available. Our case of AML with 45,XX,inv(3)(q21q26),À7, t(9;22)(q34;q11.2) shows two recognized secondary cytogenetic anomalies in advanced CML, that is, monosomy 7 and chromosome aberrations involving band 3q21or 3q26, 8 which initially would have suggested a case of CML blast crisis. However, simultaneous presence of À7 and inv(3)(q21q26) in blastic CML is rare (http://cgap.nci.nih.gov/Chromosomes). We propose that owing to the secondary nature of the Ph chromosome, the rarity in which these three cytogenetic changes are found together in blast crisis, the lack of p210 BCR-ABL protein transcript and the absence of splenomegaly, our case is more in keeping with de novo Ph þ AML over myeloid blastic CML. This is confirmed by FISH studies, which revealed the Ph chromosome is acquired as a late event during clonal evolution. It is salutary to note that combination of FISH and RT-PCR analysis was needed to avoid the erroneous conclusion of imatinib resistance as the size of the BCR-ABL clone went down which is not compatible with BCR-ABL-dependent imatinib resistance.

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

“…On this basis, we conclude that UDC and FISH are insufficient to predict HR in advance, consistent with observations of other groups. 34,35 The majority of AML cells express the CD34 antigen, and we and others have reported an association between a low or decreasing CD34 þ DC and relapse after HCT with conventional conditioning, 36 2 Gy total body irradiation, 7 other RIC regimens 37 or both RIC and conventional conditioning. 33 …”

“…This may be explained in part by the recently recognized phenomenon of WT1 exon 7 mutations, which might have prevented sufficient primer binding and compromised the performance of the RT-PCR amplification. 20,37,38 WT1 expression above the cutoff corresponds to an odds ratio of impending relapse of 27.6. This is comparable with the predictive power of MRD levels determined via T-cell receptor and immunoglobulin gene rearrangement in standard risk acute lymphoblastic leukemia, in which an MRD level higher than 10 À4 by 16 weeks was associated with a relapse risk of 95% within 3 years.…”

Standardization of WT1 mRNA quantitation for minimal residual disease monitoring in childhood AML and implications of WT1 gene mutations: a European multicenter study

“…[18][19][20][21][22][23][24] Hotspots for mutations were recently detected and included, among others, exon 7 of the WT1 gene. 18,19,22 As the reverse primer of our qRT-PCR approach spans exons 6 and 7, mutations in exon 7 might theoretically affect the detection of WT1 expression, if a potential mutation is located at the binding site of the primer.…”

“…[18][19][20][21][22][23][24] As pediatric AML is a rare disease, international cooperation is necessary for monitoring substantial numbers of patients to obtain statistically powerful results. Although various methodologies have been applied in the past, a uniform approach that has been proven to ensure reproducible, accurate and comparable results on a multicenter basis is currently unavailable.…”

Reply to ‘Wilms' tumour 1 mutations are associated with FLT3-ITD and failure of standard induction chemotherapy in patients with normal karyotype AML’ by Summers et al.

“…We thank Dr Summers et al for their interest in our recent report 1 on the emergence of a clone of Wilm's tumour 1 (WT1) mutated AML blasts in a paediatric patient. Their data 2 support and considerably extend our data and argue for further studies in this increasingly interesting gene.…”