WT1 gene expression: an excellent tool for monitoring minimal residual disease in 70% of acute myeloid leukaemia patients - results from a single-centre study

WT1 together with RUNX1::RUNX1T1 targets DUSP6 to dampen ERK activity in acute myeloid leukaemia

Wilms' tumour 1 (WT1) can function as an oncogene or a tumour suppressor. Our previous clinical cohort studies showed that low WT1 expression at diagnosis independently predicted poor outcomes in acute myeloid leukaemia (AML) with RUNX1::RUNX1T1, whereas it had an opposite role in AML with non-favourable cytogenetic risk (RUNX1::RUNX1T1-deficient). The molecular mechanism by which RUNX1::RUNX1T1 affects the prognostic significance of WT1 in AML remains unknown. In the present study, first we validated the prognostic significance of WT1 expression in AML. Then by using the established transfected cell lines and xenograft tumour model, we found that WT1 suppresses proliferation and enhances effect of cytarabine in RUNX1::RUNX1T1(+) AML but has opposite functions in AML cells without RUNX1::RUNX1T1. Furthermore, as a transcription factor, WT1 physically interacts with RUNX1::RUNX1T1 and acts as a co-factor together with RUNX1::RUNX1T1 to activate the expression of its target gene DUSP6 to dampen extracellular signal-regulated kinase (ERK) activity. When RUNX1::RUNX1T1-deficient, WT1 can activate the mitogen-activated extracellular signal-regulated kinase/ERK axis but not through targeting DUSP6. These results provide a mechanism by which WT1 together with RUNX1::RUNX1T1 suppresses cell proliferation through WT1/DUSP6/ERK axis in AML. The current study provides an explanation for the controversial prognostic significance of WT1 expression in AML patients.

Multi-target measurable residual disease assessed by error-corrected sequencing in patients with acute myeloid leukemia: An ALFA study

The evaluation of measurable residual disease (MRD) in acute myeloid leukemia (AML) using comprehensive mutation analysis by next-generation sequencing (NGS) has been investigated in several studies. However controversial results exist regarding the detection of persisting mutations in DNMT3A, TET2, and ASXL1 (DTA). Benchmarking of NGS-MRD taking into account other molecular MRD strategies has to be done. Here, we performed error-corrected-NGS-MRD in 189 patients homogeneously treated in the ALFA-0702 study (NCT00932412). Persistence of non-DTA mutations (HR = 2.23 for RFS and 2.26 for OS), and DTA mutations (HR = 2.16 for OS) were associated with poorer prognosis in multivariate analysis. Persistence of at least two mutations in complete remission (CR) was associated with a higher cumulative incidence of relapse (CIR) (HR = 3.71, p < 0.0001), lower RFS (HR = 3.36, p < 0.0001) and OS (HR = 3.81, p = 0.00023) whereas persistence of only one mutation was not. In 100 analyzable patients, WT1-MRD, but not NGS-MRD, was an independent factor for RFS and OS. In the subset of 67 NPM1 mutated patients, both NPM1 mutation detection (p = 0.0059) and NGS-MRD (p = 0.035) status were associated with CIR. We conclude that detectable NGS-MRD including DTA mutations correlates with unfavorable prognosis in AML. Its integration with alternative MRD strategies in AML management warrants further investigations.

High WT1 expression predicted induction chemotherapy failure in acute myeloid leukemia patients with non-favorable cytogenetic risk

The prognostic significance of WT1 expression at diagnosis in acute myeloid leukemia (AML) remains obscure, and subgroup analysis is the way for clarification. We previously reported the results in t(8;21) AML. In this study, 437 consecutive adult AML patients with non-favorable cytogenetic risk were enrolled. All patients were tested WT1 transcript levels using real-time quantitative PCR at diagnosis; AML-related common fusion genes, KMT2A-PTD, FLT3-ITD, NPM1, CEBPA and TP53 mutations were simultaneously tested. 92.4% of patients overexpressed WT1 compared to normal bone marrow. The existence of FLT3-ITD, NPM1 mutation and the absence of CEBPA biallelic mutation were significantly related to higher WT1 expression. The cutoff value for WT1 was determined by performing receiver operating characteristic curve analysis in regard to complete remission (CR) achievement and was used to categorize patients into low-expression (WT1-L) and high-expression (WT1-H) groups. In the entire cohort, WT1-H was significantly associated with a lower 1-course and 2-course CR rate (P < 0.0010 and P = 0.0060) but was not related to relapse-free survival (RFS). Multivariate analysis showed that WT1-H was an independent adverse prognostic factor for both 1-course and 2-course CR achievement. Subgroup analysis was further performed. WT1-H had a significant adverse impact on CR achievement within intermediate-cytogenetic risk, high-cytogenetic risk, ELN-defined-intermediate-risk, normal karyotype, KMT2A rearrangement, FAB-M2, FAB-M5 and NPM1 mutation (+) subgroups, whereas it had no impact within ELN-defined-low-risk, ELN-defined-high-risk, FAB-M4, FLT3-ITD mutation (+) and CEBPA biallelic mutation (+) subgroups. Moreover, WT1-H patients had a significantly lower RFS rate than WT1-L patients within both FAB-M5 and KMT2A rearrangement subgroups (P = 0.010 and 0.028), whereas WT1 had no impact on RFS within other subgroups mentioned above (all P > 0.05). Therefore, high WT1 expression at diagnosis independently predicted induction chemotherapy failure in AML patients with non-favorable cytogenetic risk, and it was related to relapse just within FAB-M5 and KMT2A rearrangement subgroups.

Eustachian Valve-Enhanced Paradoxical Cerebral Embolism: A Case Report

Cryptogenic stroke includes many suspicious embolic causes that do not fulfill the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification criteria. Atrial fibrillation (AF) is one of the major hidden causes of cryptogenic stroke, and an implantable loop recorder (ILR) is widely used for detecting AF. Herein, we report a case of paradoxical cerebral embolism due to a large Eustachian valve with large PFO under no molecular complete remission (CR) of acute monocytic leukemia (AMoL). A 75-year-old man arrived at our emergency room because of aphasia and right hemiparesis. He had a history of two cryptogenic strokes and implanted ILR. Magnetic resonance imaging showed left middle cerebral artery occlusion with slight acute ischemic lesion. The red clot was retrieved by mechanical thrombectomy, and complete recanalization was achieved. We checked ILR, but there was no AF. Transesophageal echocardiography revealed a large patent foramen ovale (PFO) and the large Eustachian valve in the right atrium. Although obvious deep vein thrombosis (DVT) was not detected in venous ultrasonography of the lower extremities, Wilms' tumor 1 messenger ribonucleic acid (WT1mRNA) expression level was high, and AMoL was considered to be not in molecular CR, suggesting a high risk of thrombosis to the large Eustachian valve. From large PFO and no molecular CR of AMoL, we diagnosed him with paradoxical cerebral embolism. Ruling out of AF by ILR and other etiologies, such as aortic or carotid atherosclerosis and pulmonary shunt, also supported the diagnosis of paradoxical cerebral embolism. Even in the absence of obvious DVT, paradoxical cerebral embolism should be considered in cases of a large Eustachian valve and PFO with a hypercoagulable state.

Prognostic value of combined WT1 and multiparameter flow cytometry assessment for measurable residual disease after induction in non-APL acute myeloid leukemia

The objective of this study was to investigate the expression pattern of Wilms tumor 1 (WT1) gene at diagnosis, complete remission (CR) and relapse status in non-acute promyelocytic leukemia (non-APL) acute myeloid leukemia (AML) patients, and further explore the prognostic value of measurable residual disease (MRD) assessment by WT1 gene and multiparameter flow cytometry (MFC). Our results showed that the average expression level of WT1 was 4026 ± 616.1 copies/104 ABL at diagnosis, 155.3 ± 36.03 copies/104 ABL at CR, and 1766 ± 238.8 copies/104 ABL at relapse, with statistically significant differences (p = .000). ROC analysis showed that WT1 expression levels were 118.1 copies/104 ABL and MFC-MRD was 0.155%, which had good predictive efficacy for relapse of patients during consolidation therapy. Both WT1-MRD and MFC-MRD had a significant impact on relapse-free survival (RFS) and overall survival (OS). Patients with WT1-MRD positive or MFC-MRD positive were associated with worse RFS (HR 3.840, 95% CI 1.582-9.320, p = .003), (HR 4.464, 95% CI 1.841-10.984, p = .001) and worse OS (HR 2.963, 95% CI 1.058-8.295, p = .039), (HR 3.590, 95% CI 1.254-10.280, p = .017). Besides, compared with patients who were negative for both WT1-MRD and MFC-MRD, patients who were positive both WT1-MRD and MFC-MRD were associated with worse RFS (HR 6.200, 95% CI 2.206-17.430, p = .001) and worse OS (HR 4.886, 95% CI 1.388-17.197, p = .013). This study demonstrates that combined assessment of MRD by WT1 and MFC improves relapse and prognosis prediction in non-APL AML patients, and may help guide interventions for disease relapse.

Shift of N-MYC Oncogene Expression in AML Patients Carrying the FLT3-ITD Mutation

Mutations in the FLT3 gene not only lead to abnormalities in its structure and function, but also affect the expression of other genes involved in leukemogenesis. This study evaluated the expression of genes that are more characteristic of neuroblastoma but less studied in leukemia. N-MYC oncogene expression was found to be more than 3-fold higher in primary AML patients carrying the FLT3-ITD mutation compared to carriers of other mutations as well as patients with normal karyotype (p = 0.03946). In contrast to the expression of several genes (C-MYC, SPT16, AURKA, AURKB) directly correlated to the allelic load of FLT3-ITD, the expression of the N-MYC oncogene is extremely weakly related or independent of it (p = 0.0405). Monitoring of N-MYC expression in some patients with high FLT3-ITD allelic load receiving therapy showed that a decrease in FLT3-ITD allelic load is not always accompanied by a decrease in N-MYC expression. On the contrary, N-MYC expression may remain elevated during the first three months after therapy, which is additional evidence of the emergence of resistance to therapy and progression of AML.

Wilms tumor 1 gene expression in acute myeloid leukemia: prognostic significance and usefulness in minimal residual disease monitoring—a case–control study

Background

Minimal residual disease (MRD), which is characterized as leukemic cells at a level below morphologic detection, has been connected to the risk of relapse in acute myeloid leukemia. In 80–90% of acute myeloid leukemia (AML) patients, the Wilms tumor (WT1) gene is overexpressed at the mRNA level. In our prospective study, a total of 55 patients were enrolled in the study. Group I involved 40 AML patients and group II involved 15 patients healthy controls. WT1 gene expression was quantified using quantitative real-time PCR on bone marrow samples from AML patients at initial diagnosis and at day 28 after induction chemotherapy, and compared to 15 healthy controls in group II. Follow up of patients for prognosis evaluation was assessed. IBM SPSS software was used to capture and analyses the data.

Results

At diagnosis, the mean WT1 transcript value in AML patients was substantially higher than the expression observed in control patient’s Bone marrow. There was no statistically relevant relationship between the onset of relapse and WT1 expression. Patients with WT1 overexpression at diagnosis had a shorter overall survival than patients with negative WT1 expression.

Conclusions

Wilms tumor 1 gene expression was found to be significantly higher in AML patients than control cases, overall, our results confirmed the prognostic significance of WT1 overexpression in AML patients. Our findings support the application of MRD in AML patients based on WT1 overexpression.

The Role of Wilms' Tumor Gene (WT1) Expression as a Marker of Minimal Residual Disease in Acute Myeloid Leukemia

The Minimal Residual Disease(MRD) monitoring in acute myeloid leukemia (AML) is crucial to guide treatment after morphologic complete remission, to define the need for consolidation with allogeneic stem cell transplantation (Allo-SCT), and to detect impending relapse allowing early intervention. However, more than 50% of patients with AML lack a specific or measurable molecular marker to monitor MRD. We reviewed the key studies on WT1 overexpression as a marker of MRD in AML patients undergoing an intensive chemotherapy program, including Allo-SCT. In addition, we provided some practical considerations on how to properly use WT1 expression as an MRD marker, considering its strengths and weaknesses. In order to achieve the best sensitivity and specificity, it is recommended to refer to the standardized method of European LeukemiaNet and its defined threshold (250 WT1 copies/10⁴ Abelson (ABL) on Bone Marrow-BM and 50 WT1 copies/10⁴ ABL on Peripheral Blood-PB), which has been validated in a large and multicenter cohort of patients and normal controls.

Early detection of WT1 measurable residual disease identifies high-risk patients, independent of transplantation in AML

Postinduction WT1 measurable residual disease is associated with shorter survival and higher risk of relapse in younger patients with AML.

Postinduction WT1 residual disease is an independent prognostic factor in patients eligible for allogeneic stem cell transplantation.

WT1 overexpression is frequently identified in acute myeloid leukemia (AML) and has been reported to be a potential marker for monitoring measurable residual disease (MRD). We evaluated the use of postinduction WT1 MRD level as a prognostic factor, as well as the interaction between postinduction WT1 MRD response and the effect of allogeneic stem cell transplantation (allo-SCT) in the first complete remission (CR). In the ALFA-0702 trial, patients with AML, aged 18 to 59, had a prospective quantification of WT1 MRD. The occurrence of a WT1 MRD ratio >2.5% in bone marrow or >0.5% in peripheral blood was defined as MRD^high, and ratios below these thresholds were defined as MRD^low. The prognostic value of MRD after induction chemotherapy was assessed in 314 patients in first CR by comparing the risk of relapse, the relapse-free survival (RFS), and the overall survival (OS). Interaction between MRD response and the allo-SCT effect was evaluated in patients by comparing the influence of allo-SCT on the outcomes of patients with MRD^high with those with MRD^low. The results showed that patients with MRD^high after induction had a higher risk of relapse and a shorter RFS and OS. The MRD response remained of strong prognostic value in the subset of 225 patients with intermediate-/unfavorable-risk AML who were eligible for allo-SCT, because patients with MRD^high had a significantly higher risk of relapse resulting in worse RFS and OS. The effect of allo-SCT was higher in patients with MRD^low than in those with MRD^high, but not significantly different. The early WT1 MRD response highlights a population of high-risk patients in need of additional therapy.

Molecular evaluation of mutations in acute myeloid leukemia patients from Turkey: A single-center study

Certain genetic mutations could have a role in the etiology of acute myeloid leukemia (AML). Hereby, in this study, we primarily aimed to investigate the distribution of genetic mutations in AML patients. We also attempted to analyze the incidence of genetic mutations in AML patients from Turkey.This retrospective study included a total of 126 patients diagnosed with AML, who had molecular mutation test results or records in their patient files. The patients who were not citizens of the Republic of Turkey were not included in the study.It was observed that analyses for at least 1 c-kit exon mutation had been carried out on 76 patients, which detected no c-kit mutation among the types of genetic mutations investigated in all of those 76 patients. We found the frequency of FMS-like tyrosine kinase 3-internal tandem duplication mutation as 25%. The prevalence of translocation(15;17) was approximately 11% and the prevalence of translocation(8;21) was % 6.25. In addition, we also showed that the frequency of inversion16 was nearly 3.7%.Lastly, the possibility of c-kit mutation in AML patients from Turkey might actually be low.

Measurable Residual Disease Monitoring of SPAG6, ST18, PRAME, and XAGE1A Expression in Peripheral Blood May Detect Imminent Relapse in Childhood Acute Myeloid Leukemia

Overexpressed genes may be useful for monitoring of measurable residual disease (MRD) in patients with childhood acute myeloid leukemia (AML) without a leukemia-specific target. The normal expression of five leukemia-associated genes (SPAG6, ST18, MSLN, PRAME, XAGE1A) was defined in children without hematologic disease (n = 53) and children with suspected infection (n = 90). Gene expression at AML diagnosis (n=50) and during follow-up (n = 21) was compared with child-specific reference values. At diagnosis, 34/50 children (68%) had high expression of at least one of the five genes, and so did 16/31 children (52%) without a leukemia-specific target. Gene expression was quantified in 110 peripheral blood (PB) samples (median, five samples/patient; range, 1 to 10) during follow-up in 21 patients with high expression at diagnosis. All nine patients with PB sampling performed within 100 days of disease recurrence displayed overexpression of SPAG6, ST18, PRAME, or XAGE1A at a median of 2 months (range, 0.6 to 9.6 months) before hematologic relapse, whereas MSLN did not reach expression above normal prior to hematologic relapse. Only 1 of 130 (0.8%) follow-up analyses performed in 10 patients in continuous complete remission had transient expression above normal. SPAG6, ST18, PRAME, and XAGE1A expression in PB may predict relapse in childhood AML patients and facilitate MRD monitoring in most patients without a leukemia-specific target.

Multicenter, Open-Label, Phase I Study of DSP-7888 Dosing Emulsion in Patients with Advanced Malignancies

BACKGROUND

Wilms' tumor 1 (WT1) is overexpressed in various malignancies. DSP-7888 Dosing Emulsion, also known as ombipepimut-S (United States Adopted Name; International Nonproprietary Name: adegramotide/nelatimotide), is an investigational therapeutic cancer vaccine comprising two synthetic peptides derived from WT1 to promote both cytotoxic T-lymphocyte (CTL) and helper T-lymphocyte-mediated immune responses against WT1-expressing tumors.

OBJECTIVE

The aim of this study was to report the results from a phase I dose-escalation study (NCT02498665) that evaluated DSP-7888, administered either intradermally (ID) or subcutaneously (SC), in patients with recurrent or advanced malignancies associated with overexpression of WT1.

PATIENTS AND METHODS

In this phase I dose-escalation study, patients with recurrent or advanced malignancies associated with overexpression of WT1 who progressed on, were intolerant to, or not a candidate for standard therapy or who presented with a malignancy that had no definite standard therapy received escalating doses of ID or SC DSP-7888 in a rolling-six study design. DSP-7888 3.5, 10.5, or 17.5 (ID only) mg was administered until disease progression or other discontinuation event. Primary objectives were safety, tolerability, and identification of the recommended phase II dose (RP2D). Overall survival (OS) and WT1-specific CTL induction were included as secondary and exploratory objectives, respectively.

RESULTS

Twenty-four patients received either ID (3.5 mg, n = 4; 10.5 mg, n = 3; 17.5 mg, n = 3) or SC DSP-7888 (3.5 mg, n = 9; 10.5 mg, n = 5). No dose-limiting toxicity was observed. The most frequent treatment-emergent adverse event was injection site reactions (ID, 100% [10/10]; SC, 35.7% [5/14]); all were grade 1 or 2. Four patients (ID 17.5 mg, n = 1; SC 3.5 mg, n = 1; SC 10.5 mg, n = 2) had stable disease, 16 had progressive disease, and four were not evaluable. Median (95% confidence interval) OS duration was 180.0 (136.0-494.0) days. Among evaluable patients, WT1-specific CTL induction was observed in 66.7% (6/9) and 41.7% (5/12) of those administered ID and SC DSP-7888, respectively.

CONCLUSIONS

DSP-7888 Dosing Emulsion was well tolerated, with no dose-limiting toxicities, in patients with recurrent or advanced malignancies. Higher WT1-specific CTL induction activity was noted with ID compared with SC administration; because of this, the ID route was selected for further evaluation in the clinical program.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02498665.

WT1 Expression in Peripheral Blood at Diagnosis and During the Course of Early Consolidation Treatment Correlates With Survival in Patients With Intermediate and Poor-Risk Acute Myeloid Leukemia

BACKGROUND

Up to 55% of non-APL acute myeloid leukemias (AML) lack a molecular target suitable for standardized disease monitoring. We aimed to evaluate the prognostic significance of WT1 gene expression at early stages of intensive treatment.

PATIENTS AND METHODS

A total of 106 consecutive patients with intermediate and high-risk AML who had WT1 expression at diagnosis >500 copies/10⁴ABL and who achieved remission after 1 to 2 cycles of induction treatment were analyzed. WT1 expression was measured in peripheral blood using a standardized European LeukemiaNet method. Overexpression was defined as >50 copies/10⁴ABL. The median follow-up was 30 months.

RESULTS

Patients with normal versus high WT1 expression after 2 cycles of chemotherapy had overall survival (OS) at 3 years of 66% versus 41% (P = .01); event-free survival (EFS) 45% versus 22% (P = .01). Prognostic significance of WT1 expression after 2 cycles of treatment was maintained in the group of patients treated with chemotherapy alone without hematopoietic stem cell transplantation in first line treatment (OS 70% vs. 36%, P = .02; EFS 35% vs. 0%, P = .03). Significant prognostic factors for EFS on multivariate analysis were the achievement of molecular remission (<50 copies of WT1) at any time during treatment (hazard ratio [HR] 0.47, P = .04) and increased WT1 expression after 2 cycles of chemotherapy (HR 2.0, P = .03).

CONCLUSION

Increased WT1 expression after 2 cycles of chemotherapy is a negative prognostic factor for survival. WT1 remains a valuable molecular marker in AML without any leukemia-specific mutation, especially if next generation sequencing and/or digital polymerase chain reaction are not routinely available.

Wilms' tumor 1 gene in hematopoietic malignancies: clinical implications and future directions

The Wilms' tumor 1 (WT1) gene is an important regulatory molecule that plays a vital role in cell growth and development. Initially, knowledge of WT1 was mostly limited to Wilms' tumor. Over the past years, numerous studies have shown that WT1 is aberrant expressed or mutated in hematopoietic malignancies, including acute leukemia (AL), myelodysplastic syndrome (MDS) and chronic myelogenous leukemia (CML). Currently, many studies focus on exploring the role of WT1 in hematopoietic malignancies. Such studies improve the understanding of hematopoietic malignancies, and the collection of data about WT1 expression or mutation in hematopoietic malignancies over the past years can facilitate the risk stratification of hematopoietic malignancies. In this review, we highlight the important role of WT1 in hematopoietic malignancies, discuss its potential clinical applications as a minimal residual disease (MRD) and prognostic biomarker, and evaluate the possible therapy target of WT1 in hematopoietic malignancies.

Application of a digital PCR method for WT1 to myeloid neoplasms in CR and deep ELN WT1 molecular response (< 10 copies)

Bone marrow WT1 mRNA levels assessed by the ELN method are useful to establish prognostic correlations in myeloid malignancies treated with chemotherapy or hematopoietic stem cell transplantation (HCT). Those patients with WT1 levels below ten copies have a good outcome. However, some of these patients relapse. To further characterize this group of cases, we applied a new and sensitive digital (ddPCR) WT1 method. A consecutive series of 49 patients with treated myeloid malignancies and with an ELN WT1 quantitation of < 10 copies were included in the study. All cases (47 AML and 2 MDS) have received intensive chemotherapy or HCT. One to four micrograms of total RNA were retrotranscribed to obtain ≥ 10,000 ABL1 copies using the ELN protocol. Only those cases with a good quality cDNA were used in the ddPCR WT1 test. The ddPCR Gene Expression WT1 Assay of Bio-Rad© was used to perform the PCR amplification, and the microdroplets were quantified in the Bio-Rad's QX200 droplet reader. Eighteen patients showed a negative WT1 ddPCR assay (0 copies/μl), whereas 31 cases were positive (results ranged from 1 to 15.2 copies/μl). Survival analysis showed statistically significant differences in terms of OS between both groups, 83 ± 8% vs. 46 ± 9% (p = 0.024). A statistically significant correlation was also found between ddPCRWT1 results and CD123+ cell number detected by flow cytometry (p = 0.024). Larger series of patients tested with the current ddPCRWT1 method will solve whether it could be used to stratify patients with myeloid malignancies achieving deep WT1 molecular response (< 10 copies).

Strategies for minimal residual disease detection: current perspectives

Currently, the post-remission treatment in acute leukemia is based on the genetic profile of leukemic cells at diagnosis (ie, FLT3 ITD positivity) and on the level of measurable residual disease (MRD) after induction and consolidation chemotherapy. Two methods are currently preferred for MRD evaluation in many centers: multiparameter flow cytometry and real-time quantitative PCR. Additional methods such as next-generation sequencing and digital PCR are under investigation, in an attempt to increase the sensitivity and thus allowing the detection of small clones. Many studies suggest that MRD positivity after chemotherapy is associated with negative prognosis, and the reappearance of MRD during follow-up allows impending relapse to be identified and consequently enables early intervention. Finally, MRD positivity before hematopoietic stem cell transplantation is predictive of the outcome. Although the significance of MRD in acute leukemia has been widely explored, the assessment of molecular MRD is not yet a routine practice. In this review, we describe the significance of MRD in different settings and the main markers and methods used for MRD detection.

Quantitative chimerism in CD3-negative mononuclear cells predicts prognosis in acute myeloid leukemia patients after hematopoietic stem cell transplantation

Relapse is a major complication of acute myeloid leukemia (AML) after allogeneic hematopoietic stem cell transplantation (SCT). The objective of our study was to evaluate chimerism monitoring on the CD3-negative mononuclear cells by RQ-PCR to predict relapse of patients allografted for AML and to compare its performance with WT1 quantification. A cohort of 100 patients undergoing allogenic SCT for AML was retrospectively analyzed in a single institution. Patients without complete chimerism, defined as less than 0.01% of recipient's DNA in CD3-negative cells, had a significantly higher risk of relapse and a lower overall survival (p < 0.001). An increase in the percentage of recipient DNA in CD3-negative cells was associated with an increased risk of relapse (p < 0.001) but not with overall survival. Comparable performances between monitoring of CD3-negative cell chimerism and WT1 expression to predict relapse was observed up to more than 90 days before hematological relapse, with sensitivity of 82% and 78%, respectively, and specificity of 100% for both approaches. Quantitative specific chimerism of the CD3-negative mononuclear fraction, enriched in blastic cells, is a new and powerful tool for monitoring measurable residual disease and could be used for AML patients without available molecular markers.

Clinical Challenges and Consequences of Measurable Residual Disease in Non-APL Acute Myeloid Leukemia

The ability to detect residual levels of leukemic blasts (measurable residual disease, MRD) has already been integrated in the daily routine for treatment of patients with chronic myeloid and acute lymphoblastic leukemia. In acute myeloid leukemia (AML), a variety of mostly retrospective studies have shown that individuals in AML remission who tested positive for MRD at specific time-points or had increasing MRD levels are at significantly higher risk of relapse and death compared to MRD-negative patients. However, these studies differ with respect to the "MRD-target", time-point of MRD determination, material analyzed, and method applied. How this probably very valuable MRD information in individual patients may be adapted in the daily clinical routine, e.g., to separate patients who need more aggressive therapies from those who may be spared additional-potentially toxic-therapies is still a work-in-progress. With the exception of MRD assessment in acute promyelocytic leukemia (APL), the lack of randomized, prospective trials renders MRD-based decisions and clinical implications in AML a difficult task. As of today, we still do not have proof that early intervention in MRD-positive AML patients would improve outcomes, although this is very likely. In this article, we review the current knowledge on non-APL AML MRD assessment and possible clinical consequences.

Monocytes reprogrammed with lentiviral vectors co-expressing GM-CSF, IFN-α2 and antigens for personalized immune therapy of acute leukemia pre- or post-stem cell transplantation

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and overall survival remains poor. Chemotherapy is the standard of care for intensive induction therapy. Patients who achieve a complete remission require post-remission therapies to prevent relapse. There is no standard of care for patients with minimal residual disease (MRD), and stem cell transplantation is a salvage therapy. Considering the AML genetic heterogeneity and the leukemia immune-suppressive properties, novel cellular immune therapies to effectively harness immunological responses to prevent relapse are needed. We developed a novel modality of immune therapy consisting of monocytes reprogrammed with lentiviral vectors expressing GM-CSF, IFN-α and antigens. Preclinical studies in humanized mice showed that the reprogrammed monocytes self-differentiated into highly viable induced dendritic cells (iDCs) in vivo which migrated effectively to lymph nodes, producing remarkable effects in the de novo regeneration of T and B cell responses. For the first-in-man clinical trial, the patient’s monocytes will be transduced with an integrase-defective tricistronic lentiviral vector expressing GM-CSF, IFN-α and a truncated WT1 antigen. For transplanted patients, pre-clinical development of iDCs co-expressing cytomegalovirus antigens is ongoing. To simplify the product chain for a de-centralized supply model, we are currently exploring a closed automated system for a short two-day manufacturing of iDCs. A phase I clinical trial study is in preparation for immune therapy of AML patients with MRD. The proposed cell therapy can fill an important gap in the current and foreseeable future immunotherapies of AML.

Treatment of Molecular Relapse by Cessation of Immunosuppression After Hematopoietic Stem Cell Transplantation in Pediatric FLT3-ITD AML Monitored by WT1 Expression in Peripheral Blood

Relapse after hematopoietic stem cell transplantation in pediatric acute myeloid leukemia is a fatal event in the majority of cases. Immunotherapy may prevent an impending relapse if instituted at first molecular evidence of disease recurrence. Wilms tumor gene 1 (WT1) is overexpressed in the majority of children and may constitute a useful molecular marker of measurable residual disease applicable for disease monitoring in peripheral blood where the background amplification from healthy hematopoiesis is less prevalent compared with bone marrow. We report the measurable residual disease kinetics from a child with FLT3-internal tandem duplication acute myeloid leukemia where sequential WT1 monitoring in peripheral blood-guided withdrawal of immunosuppression.

Measurable residual disease monitoring using Wilms tumor gene 1 expression in childhood acute myeloid leukemia based on child-specific reference values

BACKGROUND

Measurable/minimal residual disease (MRD) monitoring can predict imminent hematological relapse in acute myeloid leukemia (AML). The majority of childhood AML patients do not harbor fusion genes or mutations applicable as MRD markers and overexpression of Wilms tumor gene 1 (WT1) may constitute a useful monitoring target. However, age-specific reference values in healthy hematopoiesis and standardization of WT1 assessment are prerequisites for clinical utility.

PROCEDURE

We investigated WT1 expression across age in hematologically healthy controls (n = 109), during suspected infection (n = 90) and bone marrow (BM) regeneration (n = 13). WT1 expression in AML at diagnosis (n = 91) and during follow-up (n = 30) was compared with age-specific reference values.

RESULTS

WT1 expression correlated with age and showed higher levels in both BM and peripheral blood (PB) in children compared with adults (P < 0.001 and P = 0.01). WT1 expression from healthy hematopoiesis was lower in PB compared with BM (WT1_BM /WT1_PB  = 8.6, 95% CI: 5.3-13.7) and not influenced by infection nor BM regeneration. At AML diagnosis, 66% had more than 20-fold WT1 overexpression in PB or BM (PB 74%; BM 45%). WT1 was quantified in 279 PB samples during follow-up. All 11 patients with PB sampling within 4 months of disease recurrence displayed WT1 overexpression by a median of 1.9 months (range, 0.7-9.7) before hematological relapse.

CONCLUSIONS

This study defines child-specific reference values for WT1 expression in healthy hematopoiesis and demonstrates that WT1 expression in PB is a useful post-treatment monitoring tool in childhood AML. Based on these observations, we propose definitions for childhood AML molecular relapse using WT1 overexpression.

Digital PCR in Myeloid Malignancies: Ready to Replace Quantitative PCR?

New techniques are on the horizon for the detection of small leukemic clones in both, acute leukemias and myeloproliferative disorders. A promising approach is based on digital polymerase chain reaction (PCR). Digital PCR (dPCR) is a breakthrough technology designed to provide absolute nucleic acid quantification. It is particularly useful to detect a low amount of target and therefore it represents an alternative method for detecting measurable residual disease (MRD). The main advantages are the high precision, the very reliable quantification, the absolute quantification without the need for a standard curve, and the excellent reproducibility. Nowadays the main disadvantages of this strategy are the costs that are still higher than standard qPCR, the lack of standardized methods, and the limited number of laboratories that are equipped with instruments for dPCR. Several studies describing the possibility and advantages of using digital PCR for the detection of specific leukemic transcripts or mutations have already been published. In this review we summarize the available data on the use of dPCR in acute myeloid leukemia and myeloproliferative disorders.

Prognostic Impact of Blood MN1 Copy Numbers Before Allogeneic Stem Cell Transplantation in Patients With Acute Myeloid Leukemia

High expression of the leukemia-associated gene meningioma-1 (MN1) is frequently found at diagnosis of acute myeloid leukemia (AML) and associates with adverse outcomes. The presence of measurable residual disease (MRD) in complete remission (CR) indicates high risk of relapse and worse outcome in AML patients. However, the prognostic impact of MN1 expression levels as MRD marker has not been evaluated. Digital droplet polymerase chain reaction (ddPCR) is a novel technique allowing sensitive and specific absolute gene expression quantification. We retrospectively analyzed 124 AML patients who received allogeneic hematopoietic stem cell transplantation (HSCT) in CR or CR with incomplete peripheral recovery. Absolute MN1 copy numbers in peripheral blood were assessed prior to HSCT (median 7; range 0-29 days) using ddPCR. High pre-HSCT MN1/Abelson murine leukemia viral oncogene homolog 1 gene (ABL1) copy numbers associated with a higher cumulative incidence of relapse after HSCT and-in relapsing patients-shorter time to relapse. In multivariable analysis, high pre-HSCT MN1/ABL1 copy numbers remained an independent prognosticator for relapse after HSCT. Patients with the highest pre-HSCT MN1/ABL1 copy numbers also had the highest risk of relapse. MN1 copy number assessment also added prognostic information to nucleophosmin 1 gene (NPM1) mutation- and brain and acute leukemia, cytoplasmic (BAALC) and Wilm's tumor gene 1 (WT1) expression-based MRD evaluation. Our study demonstrates the feasibility of the novel ddPCR technique for MN1/ABL1 copy number assessment as a marker for MRD. Evaluation of MN1/ABL1 copy numbers allows the identification of patients at high risk of relapse, independently of other diagnostic risk factors and MRD markers.

Molecular Minimal Residual Disease Testing in Acute Myeloid Leukemia: A Review for the Practicing Clinician

Minimal residual disease (MRD) testing in acute myeloid leukemia is increasingly being used to assess treatment response and stratify the risk of relapse for individual patients. Molecular methods for MRD testing began with PCR-based assays for individual recurrent mutations. To date, there is robust evidence for testing NPM1, CBFB-MYH11, and RUNX1/RUNXT1 mutations using this approach, though the best timing and threshold level for each mutation varies. More recent approaches have been with PCR-based multigene panels, occasionally combined with flow cytometric techniques, and next-generation sequencing techniques. This review outlines the various techniques used in molecular approaches to MRD, the evidence behind individual mutation testing, and the novel approaches for evaluating multigene MRD so that clinicians can understand and incorporate these evaluations into their practice.

Outcomes of Measurable Residual Disease in Pediatric Acute Myeloid Leukemia before and after Hematopoietic Stem Cell Transplant: Validation of Difference from Normal Flow Cytometry with Chimerism Studies and Wilms Tumor 1 Gene Expression

We enrolled 150 patients in a prospective multicenter study of children with acute myeloid leukemia undergoing hematopoietic stem cell transplantation (HSCT) to compare the detection of measurable residual disease (MRD) by a "difference from normal" flow cytometry (ΔN) approach with assessment of Wilms tumor 1 (WT1) gene expression without access to the diagnostic specimen. Prospective analysis of the specimens using this approach showed that 23% of patients screened for HSCT had detectable residual disease by ΔN (.04% to 53%). Of those patients who proceeded to transplant as being in morphologic remission, 10 had detectable disease (.04% to 14%) by ΔN. The disease-free survival of this group was 10% (0 to 35%) compared with 55% (46% to 64%, P < .001) for those without disease. The ΔN assay was validated using the post-HSCT specimen by sorting abnormal or suspicious cells to confirm recipient or donor origin by chimerism studies. All 15 patients who had confirmation of tumor detection relapsed, whereas the 2 patients with suspicious phenotype cells lacking this confirmation did not. The phenotype of the relapse specimen was then used retrospectively to assess the pre-HSCT specimen, allowing identification of additional samples with low levels of MRD involvement that were previously undetected. Quantitative assessment of WT1 gene expression was not predictive of relapse or other outcomes in either pre- or post-transplant specimens. MRD detected by ΔN was highly specific, but did not identify most relapsing patients. The application of the assay was limited by poor quality among one-third of the specimens and lack of a diagnostic phenotype for comparison.

Role of minimal residual disease in the management of acute myeloid leukemia-a case-based discussion

AML is stratified into risk-categories based on cytogenetic and molecular features that prognosticate survival and facilitate treatment algorithms, though there is still significant heterogeneity within risk groupings with regard to risk of relapse and prognosis. The ambiguity regarding prognosis is due in large part to the relatively outdated criteria used to determine response to therapy. Whereas risk assessment has evolved to adopt cytogenetic and molecular profiling, response criteria are still largely determined by bone marrow morphologic assessment and peripheral cell count recovery. Minimal residual disease refers to the detection of a persistent population of leukemic cells below the threshold for morphologic CR determination. MRD assessment represents standard of care for ALL and PML, but concerns over prognostic capability and standardization have limited its use in AML. However, recent advancements in MRD assessment and research supporting the use of MRD assessment in AML require the reconsideration and review of this clinical tool in this disease entity. This review article will first compare and contrast the major modalities used to assess MRD in AML, such as RQ-PCR and flow cytometry, as well as touching upon newer technologies such as next-generation sequencing and digital droplet PCR. The majority of the article will discuss the evidence supporting the use of MRD assessment to prognosticate disease at various time points during treatment, and review the limited number of studies that have incorporated MRD assessment into novel treatment algorithms for AML. The article concludes by discussing the current major limitations to the implementation of MRD assessment in this disease. The manuscript is bookended by a clinical vignette that highlights the need for further research and refinement of this clinical tool.

The Wilms' tumor gene-1 is a prognostic factor in myelodysplastic syndrome: a meta analysis

Previous studies have suggested that Wilms’ tumor gene-1 (WT1) may be related to a decrease in both relapse-free survival (RFS) and overall survival (OS) for patients with myelodysplastic syndrome (MDS). Therefore, we conducted a meta-analysis on the utility of WT1 as a prognostic indicator of MDS. Published reports were searched in the following databases: Cochrane Library, PubMed, Embase, and Web of Science. The meta-analysis was conducted using the Cochrane Collaboration RevMan 5.2 software. Six publications with 450 total patients met the inclusion criteria and were subjected to further examination. The results showed a reduction in both overall survival (OS) and leukemia-free survival (LFS) with increasing WT1 expression levels: 1-year OS (odds ratio, OR = 0.16; 95% CI = 0.08–0.34, P < 0.001), 3-year OS (OR = 0.21; 95% CI = 0.09–0.47, P < 0.001), 5-year OS (OR = 0.24; 95% CI = 0.06–0.92, P = 0.04), 1-year LFS (OR = 0.06; 95% CI = 0.02–0.18; P < 0.001), 3-year LFS (OR = 0.20; 95% CI = 0.09–0.46; P < 0.001), and 5-year LFS (OR = 0.12; 95% CI = 0.04–0.38; P < 0.001). In terms of patients receiving hematopoietic stem cell transplantation, the cumulative incidence of relapse (CIR) was higher in the WT1 over-expression group than in the low-expression group: 1-year CIR (OR = 13.69; 95% CI = 2.99–62.62; P < 0.001), 3-year CIR (OR = 6.52; 95% CI = 2.31–18.40, P < 0.001). In conclusion, WT1 over-expression is a prognostic factor for MDS.

Leukemia Associated Antigens: Their Dual Role as Biomarkers and Immunotherapeutic Targets for Acute Myeloid Leukemia

Leukemia associated antigens (LAAs) are being increasingly identified by methods such as cytotoxic T-lymphocyte (CTL) cloning, serological analysis of recombinant cDNA expression libraries (SEREX) and mass spectrometry (MS). In additional, large scale screening techniques such as microarray, single nucleotide polymorphisms (SNPs), serial analysis of gene expression (SAGE) and 2-dimensional gel electrophoresis (2-DE) have expanded our understanding of the role that tumor antigens play in the biological processes which are perturbed in acute myeloid leukemia (AML). It has become increasingly apparent that these antigens play a dual role, not only as targets for immunotherapy, but also as biomarkers of disease state, stage, response to treatment and survival. We need biomarkers to enable the identification of the patients who are most likely to benefit from specific treatments (conventional and/or novel) and to help clinicians and scientists improve clinical end points and treatment design. Here we describe the LAAs identified in AML, to date, which have already been shown to play a dual role as biomarkers of AML disease.

High BAALC copy numbers in peripheral blood prior to allogeneic transplantation predict early relapse in acute myeloid leukemia patients

High BAALC expression levels at acute myeloid leukemia diagnosis have been linked to adverse outcomes. Recent data indicate that high BAALC expression levels may also be used as marker for residual disease following acute myeloid leukemia treatment. Allogeneic hematopoietic stem cell transplantation (HSCT) offers a curative treatment for acute myeloid leukemia patients. However, disease recurrence remains a major clinical challenge and identification of high-risk patients prior to HSCT is crucial to improve outcomes. We performed absolute quantification of BAALC copy numbers in peripheral blood prior (median 7 days) to HSCT in complete remission (CR) or CR with incomplete peripheral recovery in 82 acute myeloid leukemia patients using digital droplet PCR (ddPCR) technology. An optimal cut-off of 0.14 BAALC/ABL1 copy numbers was determined and applied to define patients with high or low BAALC/ABL1 copy numbers. High pre-HSCT BAALC/ABL1 copy numbers significantly associated with higher cumulative incidence of relapse and shorter overall survival in univariable and multivariable models. Patients with high pre-HSCT BAALC/ABL1 copy numbers were more likely to experience relapse within 100 days after HSCT. Evaluation of pre-HSCT BAALC/ABL1 copy numbers in peripheral blood by ddPCR represents a feasible and rapid way to identify acute myeloid leukemia patients at high risk of early relapse after HSCT. The prognostic impact was also observed independently of other known clinical, genetic, and molecular prognosticators. In the future, prospective studies should evaluate whether acute myeloid leukemia patients with high pre-HSCT BAALC/ABL1 copy numbers benefit from additional treatment before or early intervention after HSCT.

Can Minimal Residual Disease Determination in Acute Myeloid Leukemia Be Used in Clinical Practice?

In acute myeloid leukemia (AML) that is in complete remission, minimal residual disease (MRD) is presumed to be present, though not morphologically evident. Advances in diagnostics now permit the detection and quantification of MRD in AML by several techniques. The level of MRD after induction and consolidation therapy correlates with disease sensitivity to chemotherapy and has greater power to predict long-term survival than patient and disease characteristics that are available at diagnosis, including genetic information. A unique advantage of MRD is that it is an integrated measure of the impact and interaction of genetics, epigenetics, host immune milieu, bone marrow environment, and drug sensitivity on disease response to treatment. Here, we review the main techniques for MRD assessment in AML, including polymerase chain reaction, multiparameter flow cytometry, and next-generation sequencing, with a focus on method-specific and general limitations to the optimal employment of MRD techniques for the determination of AML prognosis. We also review the data that establish the prognostic and predictive value of MRD assessment in AML. Finally, we provide recommendations for the use of MRD in the care of patients with AML in clinical practice today, including whether it should influence treatment decisions.

[Minimal residual disease level predicts outcomes in the non-favorable risk patients with acute myeloid leukemia]

Objective: To explore impact of minimal residual leukemia (MRD) on outcomes in the non-favorable risk adults with de novo acute myeloid leukemia (AML) . Methods: From January 2008 to February 2016, data of consecutive newly-diagnosed non-favorable risk adults with AML (non-APL) according to SWOG criteria who achieved morphologic leukemia-free state (MLFS) and received continuous chemotherapy were assessed retrospectively. Results: 292 AML patients were enrolled, 150 (51.4%) were male. Median age was 46 years (range, 18-65 years) . Using the SWOG cytogenetic classification, 186 (63.7%) , 49 (16.8%) and 57 (19.5%) patients belonged to intermediate, unfavorable and unknown categories, respectively. With a median follow-up period of 15 months (range, 1 to 94 months) in survivors, the probabilities of cumulative rates of relapse (CIR) , disease free survival (DFS) and overall survival (OS) at 2-years were 51.6%, 42.6% and 60.0%, respectively. Multivariate analyses showed that MRD positive (defined as Q-PCR WT1 mRNA ≥0.6% or any level of abnormal blast population detected by flow cytometry) after achieving MLFS and PLT<100×10(9)/L were common adverse factors affecting CIR and DFS. In addition, positive FLT3-ITD mutation and CRp/CRi had negatively impact on CIR, DFS and OS. Monosomal karyotype was adverse factors affecting CIR and OS. Age ≥44 years and unfavorable-risk of SWOG criteria were associated with shorter DFS. Conclusions: MRD level after achieving MLFS had prognostic significance on outcomes in non-favorable adults with AML who received continuous chemotherapy after achieving MLFS.

Enhancing acute myeloid leukemia therapy - monitoring response using residual disease testing as a guide to therapeutic decision-making

INTRODUCTION

Current standards for monitoring the response of acute myeloid leukemia (AML) are based on morphologic assessments of the bone marrow and recovery of peripheral blood counts. A growing experience is being developed to enhance the detection of small amounts of AML, or minimal residual disease (MRD). Areas covered: Available techniques include multi-color flow cytometry (MFC) of leukemia associated immunophenotypes (LAIP), quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) for detecting fusion and mutated genes (RUNX1-RUNX1T1, CBFB-MYH11, and NPM1), overexpression of genes such as WT1, and next generation sequencing (NGS) for MRD. Expert commentary: While MRD monitoring is standard of care in some leukemia subsets such as acute promyelocytic leukemia, this approach for the broader AML population does not universally predict outcomes as some patients may experience relapse in the setting of undetectable leukemia while others show no obvious disease progression despite MRD positivity. However, there are instances where MRD can identify patients at increased risk for relapse that may change recommended therapy. Currently, prospective investigations to define clinically relevant MRD thresholds are ongoing. Risk-adapted trials are needed to best define the use of MRD in the follow up of AML patients after initial induction therapy.

Quantitative assessment of Wilms tumor 1 expression by real-time quantitative polymerase chain reaction in patients with acute myeloblastic leukemia

BACKGROUND

The Wilms tumor 1 (WT1) gene is originally defined as a tumor suppressor gene and a transcription factor that overexpressed in leukemic cells. It is highly expressed in more than 80% of acute myeloid leukemia (AML) patients, both in bone marrow (BM) and in peripheral blood (PB), and it is used as a powerful and independent marker of minimal residual disease (MRD); we have determined the expression levels of the WT1 by real-time quantitative polymerase chain reaction (RQ-PCR) in PB and BM in 126 newly diagnosed AML patients.

MATERIALS AND METHODS

This study was done in molecular pathology and cancer research center from April 2014 to June 2015, RQ-PCR method was used to determine the WT1 gene expression in BM and/or PB samples from 126 patients of AML, we cloned both WT1 and ABL genes for creating a standard curve, and we calculate copy number of WT1 genes in patients.

RESULTS

A total of 126 AML patients consist of 70 males (55.6%) and 56 females (44.4%), with a median age of 26 years; 104 (81%) patients out of 126 show overexpression of WT1 gene. We also concomitant monitoring of fusion transcripts (PML RARa, AML1-ETO, MLL-MLL, CBFb-MYH11, or DEK-CAN) in our patients, the AML1-ETO group showing remarkably low levels of WT1 compared with other fusion transcript and the CBFB-MYH11 showing high levels of WT1.

CONCLUSION

We conclude that WT1 expression by RQ-PCR in AML patients may be employed as an independent tool to detect MRD in the majority of normal karyotype AML patients.

Immune responses and long-term disease recurrence status after telomerase-based dendritic cell immunotherapy in patients with acute myeloid leukemia

BACKGROUND

Telomerase activity in leukemic blasts frequently is increased among patients with high-risk acute myeloid leukemia (AML). In the current study, the authors evaluated the feasibility, safety, immunogenicity, and therapeutic potential of human telomerase reverse transcriptase (hTERT)-expressing autologous dendritic cells (hTERT-DCs) in adult patients with AML.

METHODS

hTERT-DCs were produced from patient-specific leukapheresis, electroporated with an mRNA-encoding hTERT and a lysosomal-targeting sequence, and cryopreserved. A total of 22 patients with a median age of 58 years (range, 30-75 years) with intermediate-risk or high-risk AML in first or second complete remission (CR) were enrolled. hTERT-DCs were generated for 24 patients (73%). A median of 17 intradermal vaccinations (range, 6-32 intradermal vaccinations) containing 1×10⁷ cells were administered as 6 weekly injections followed by 6 biweekly injections. A total of 21 patients (16 in first CR, 3 in second CR, and 2 with early disease recurrence) received hTERT-DCs.

RESULTS

hTERT-DCs were well tolerated with no severe toxicities reported, with the exception of 1 patient who developed idiopathic thrombocytopenic purpura. Of the 19 patients receiving hTERT-DCs in CR, 11 patients (58%) developed hTERT-specific T-cell responses that primarily were targeted toward hTERT peptides with predicted low human leukocyte antigen (HLA)-binding affinities. With a median follow-up of 52 months, 58% of patients in CR (11 of 19 patients) were free of disease recurrence at the time of their last follow-up visit; 57% of the patients who were aged ≥60 years (4 of 7 patients) also were found to be free of disease recurrence at a median follow-up of 54 months.

CONCLUSIONS

The generation of hTERT-DCs is feasible and vaccination with hTERT-DCs appears to be safe and may be associated with favorable recurrence-free survival. Cancer 2017;123:3061-72. © 2017 American Cancer Society.

WT1 protein is cleaved by caspase-3 in apoptotic leukemic cells

The aberrant overexpression of Wilms' tumor-1 gene (WT1) plays an important role in blast cell survival and resistance to chemotherapy in acute myeloid leukemia (AML). Here, we found in chemotherapeutic drug etoposide-induced apoptosis, WT1 protein was cleaved into smaller fragment by caspase-3 in leukemic cells. The cleavage was blocked by pan-caspase inhibitor and special caspase-3 inhibitor, suggesting that caspase-3 might cleave WT1 protein. Furthermore, recombinant active caspase-3 cleaved the Flag-WT1 and GST-WT1 proteins in vitro. However, site-directed mutagenesis analyses failed to identify caspase-3-targeted sites in WT1 protein, indicating that caspase-3 cleaved uncommon sites but not classical motifs (DXXD) and non-classical motifs (XXXD). Finally, Eto decreased c-Myc and Bcl-2 expression via reducing the binding of WT1 to the promoter and Eto-induced apoptosis was partially prevented by overexpression of WT1. Collectively, we identify a new substrate for caspase-3 and shed new light on understanding the complicated biology of WT1 in leukemia.

Use of Wilms Tumor 1 Gene Expression as a Reliable Marker for Prognosis and Minimal Residual Disease Monitoring in Acute Myeloid Leukemia With Normal Karyotype Patients

BACKGROUND

Acute myeloid leukemia with normal karyotype (AML-NK) represents the largest group of AML patients classified with an intermediate prognosis. A constant need exists to introduce new molecular markers for more precise risk stratification and for minimal residual disease (MRD) monitoring.

PATIENTS AND METHODS

Quantitative assessment of Wilms tumor 1 (WT1) gene transcripts was performed using real-time polymerase chain reaction. The bone marrow samples were collected at the diagnosis from 104 AML-NK patients and from 34 of these patients during follow-up or disease relapse.

RESULTS

We found that overexpression of the WT1 gene (WT1^high status), present in 25.5% of patients, was an independent unfavorable factor for achieving complete remission. WT1^high status was also associated with resistance to therapy and shorter disease-free survival and overall survival. Assessment of the log reduction value of WT1 expression, measured in paired diagnosis/complete remission samples, revealed that patients with a log reduction of < 2 had a tendency toward shorter disease-free survival and overall survival and a greater incidence of disease relapse. Combining WT1 gene expression status with NPM1 and FLT3-ITD mutational status, we found that the tumor behavior of intermediate patients (FLT3-ITD^-/NPM1^- double negative) with WT1^high status is almost the same as the tumor behavior of the adverse risk group.

CONCLUSION

WT1 expression status represents a good molecular marker of prognosis, response to treatment, and MRD monitoring. Above all, the usage of the WT1 expression level as an additional marker for more precise risk stratification of AML-NK patients could lead to more adapted, personalized treatment protocols.

Impact of Wilms' tumor 1 expression on outcome of patients undergoing allogeneic stem cell transplantation for AML

The monitoring of the minimal residual disease by Wilms' tumor 1 expression (MRD^WT1) is a standardized test, which can be used in over 80% of patients with AML. To investigate the prognostic value of MRD^WT1 in patients undergoing allogeneic stem cell transplantation (allo-SCT) for AML, MRD^WT1 was monitored 3 months after transplantation in 139 patients. MRD^WT1 positivity did not lead to any therapeutic intervention. Median follow-up was 39.3 (6.4-99.8) months. Patients with positive MRD^WT1 at 3 months experienced more often post-transplant relapse (27/30, 90%) than those with negative MRD^WT1 (16/109, 14.7%) (P<0.0001). Similarly, a shorter 3-year event-free survival (EFS) was observed in MRD^WT1-positive patients (10% vs 72.3% in MRD^WT1-negative patients, P<0.0001). The correlation between relapse and MRD^WT1 was stronger in blood than in bone marrow samples. Multivariate analysis confirmed the detrimental role of 3-month positive MRD^WT1 for relapse (hazard ratio (HR): 15.42; 95% confidence interval (CI): 7.53-31.59; P<0.0001) and EFS (HR: 10.71; 95% CI: 5.41-21.21; P<0.0001). Interestingly, 3-month chimerism was less predictive of relapse than positive MRD^WT1. In conclusion, our results demonstrate the usefulness of peripheral blood MRD^WT1 monitoring in identifying very high-risk patients, who could benefit from an early preemptive treatment, and those who do not need such an intervention.

Minimal Residual Disease in Acute Myeloid Leukemia of Adults: Determination, Prognostic Impact and Clinical Applications

Pretreatment assessment of cytogenetic/genetic signature of acute myeloid leukemia (AML) has been consistently shown to play a major prognostic role but also to fail at predicting outcome on individual basis, even in low-risk AML. Therefore, we are in need of further accurate methods to refine the patients’ risk allocation process, distinguishing more adequately those who are likely to recur from those who are not. In this view, there is now evidence that the submicroscopic amounts of leukemic cells (called minimal residual disease, MRD), measured during the course of treatment, indicate the quality of response to therapy. Therefore, MRD might serve as an independent, additional biomarker to help to identify patients at higher risk of relapse. Detection of MRD requires the use of highly sensitive ancillary techniques, such as polymerase chain reaction (PCR) and multiparametric flow cytometry(MPFC). In the present manuscript, we will review the current approaches to investigate MRD and its clinical applications in AML management.

Clinical Impact of Overexpression of FOXP3 and WT1 on Disease Outcome in Egyptian Acute Myeloid Leukemia Patients

Background:

In the last decade, it has become clear that change of gene expression may alter the hematopoietic cell quiescent state and consequently play a major role in leukemogenesis. WT1 is known to be a player in acute myeloid leukemia (AML) and FOXP3 has a crucial role in regulating the immune response.

Objectives:

To evaluate the impact of overexpression of WT1and FOXP3 genes on clinical course in adult and pediatric AML patients in Egypt.

Patients and methods:

Bone marrow and peripheral blood samples were obtained from 97 de novo non M3 AML patients (63 adult and 34 pediatric). Real-time quantitative PCR was used to detect overexpression WT1 and FOXP3 genes. Patient follow up ranged from 0.2 to 39.0 months with a median of 5 months.

Results:

In the pediatric group; WT1 was significantly expressed with a high total leukocyte count median 50X109/L (p=0.018). In the adult group, WT1 had an adverse impact on complete remission induction, disease-free survival and overall survival (p=0.02, p=0.035, p=0.019 respectively). FOXP3 overexpression was associated with FAB subtypes AML M0 +M1 vs. M2, M4+M5 (p =0.039) and the presence of hepatomegaly (p=0.005).

Conclusions:

WT1 and FOXP3 overexpression has an adverse impact on clinical presentation, treatment response and survival of pediatric and adult Egyptian AML patients.

Low WT1 transcript levels at diagnosis predicted poor outcomes of acute myeloid leukemia patients with t(8;21) who received chemotherapy or allogeneic hematopoietic stem cell transplantation

Background

Acute myeloid leukemia (AML) with t(8;21) is a heterogeneous disease. Identifying AML patients with t(8;21) who have a poor prognosis despite achieving remission is important for determining the best subsequent therapy. This study aimed to evaluate the impact of Wilm tumor gene-1 (WT1) transcript levels and cellular homolog of the viral oncogene v-KIT receptor tyrosine kinase (C-KIT) mutations at diagnosis, and RUNX1-RUNX1T1 transcript levels after the second consolidation chemotherapy cycle on outcomes.

Methods

Eighty-eight AML patients with t(8;21) who received chemotherapy only or allogeneic hematopoietic stem cell transplantation (allo-HSCT) were included. Patients who achieved remission, received two or more cycles of consolidation chemotherapy, and had a positive measureable residual disease (MRD) test result (defined as <3-log reduction in RUNX1-RUNX1T1 transcript levels compared to baseline) after 2–8 cycles of consolidation chemotherapy were recommended to receive allo-HSCT. Patients who had a negative MRD test result were recommended to receive further chemotherapy up to only 8 cycles. WT1 transcript levels and C-KIT mutations at diagnosis, and RUNX1-RUNX1T1 transcript levels after the second consolidation chemotherapy cycle were tested.

Results

Patients who had a C-KIT mutation had significantly lower WT1 transcript levels than patients who did not have a C-KIT mutation (6.7% ± 10.6% vs. 19.5% ± 19.9%, P < 0.001). Low WT1 transcript levels (≤5.0%) but not C-KIT mutation at diagnosis, a positive MRD test result after the second cycle of consolidation chemotherapy, and receiving only chemotherapy were independently associated with high cumulative incidence of relapse in all patients (hazard ratio [HR] = 3.53, 2.30, and 11.49; 95% confidence interval [CI] 1.64–7.62, 1.82–7.56, and 4.43–29.82; P = 0.002, 0.034, and <0.001, respectively); these conditions were also independently associated with low leukemia-free survival (HR = 3.71, 2.33, and 5.85; 95% CI 1.82–7.56, 1.17–4.64, and 2.75–12.44; P < 0.001, 0.016, and <0.001, respectively) and overall survival (HR = 3.50, 2.32, and 4.34; 95% CI 1.56–7.82, 1.09–4.97, and 1.98–9.53; P = 0.002, 0.030, and <0.001, respectively) in all patients.

Conclusions

Testing for WT1 transcript levels at diagnosis in patients with AML and t(8;21) may predict outcomes in those who achieve remission. A randomized study is warranted to determine whether allo-HSCT can improve prognosis in these patients.

Monitoring minimal residual disease in acute myeloid leukaemia: a review of the current evolving strategies

Several disease-monitoring techniques are available for the physician treating acute myeloid leukaemia (AML). Besides immunohistochemistry assisted light microscopy, the past 20 years have seen the development and preclinical perfection of a number of techniques, most notably quantitative polymerase chain reaction (PCR) and multicolor flow cytometry. Late additions to the group of applicable assays include next generation sequencing and digital PCR. In this review the principles of use of these modalities at three different time points during the AML disease course are discussed, namely at the time of treatment evaluation, pretransplantation and postconsolidation. The drawbacks and pitfalls of each different technique are delineated. The evidence or lack of evidence for minimal residual disease guided treatment decisions is discussed. Lastly, future strategies in the MRD field are suggested and commented upon.