Molecular Minimal Residual Disease in Acute Myeloid Leukemia

BACKGROUND

Patients with acute myeloid leukemia (AML) often reach complete remission, but relapse rates remain high. Next-generation sequencing enables the detection of molecular minimal residual disease in virtually every patient, but its clinical value for the prediction of relapse has yet to be established.

METHODS

We conducted a study involving patients 18 to 65 years of age who had newly diagnosed AML. Targeted next-generation sequencing was carried out at diagnosis and after induction therapy (during complete remission). End points were 4-year rates of relapse, relapse-free survival, and overall survival.

RESULTS

At least one mutation was detected in 430 out of 482 patients (89.2%). Mutations persisted in 51.4% of those patients during complete remission and were present at various allele frequencies (range, 0.02 to 47%). The detection of persistent DTA mutations (i.e., mutations in DNMT3A, TET2, and ASXL1), which are often present in persons with age-related clonal hematopoiesis, was not correlated with an increased relapse rate. After the exclusion of persistent DTA mutations, the detection of molecular minimal residual disease was associated with a significantly higher relapse rate than no detection (55.4% vs. 31.9%; hazard ratio, 2.14; P<0.001), as well as with lower rates of relapse-free survival (36.6% vs. 58.1%; hazard ratio for relapse or death, 1.92; P<0.001) and overall survival (41.9% vs. 66.1%; hazard ratio for death, 2.06; P<0.001). Multivariate analysis confirmed that the persistence of non-DTA mutations during complete remission conferred significant independent prognostic value with respect to the rates of relapse (hazard ratio, 1.89; P<0.001), relapse-free survival (hazard ratio for relapse or death, 1.64; P=0.001), and overall survival (hazard ratio for death, 1.64; P=0.003). A comparison of sequencing with flow cytometry for the detection of residual disease showed that sequencing had significant additive prognostic value.

CONCLUSIONS

Among patients with AML, the detection of molecular minimal residual disease during complete remission had significant independent prognostic value with respect to relapse and survival rates, but the detection of persistent mutations that are associated with clonal hematopoiesis did not have such prognostic value within a 4-year time frame. (Funded by the Queen Wilhelmina Fund Foundation of the Dutch Cancer Society and others.).

Minimal/measurable residual disease in AML: a consensus document from the European LeukemiaNet MRD Working Party

Measurable residual disease (MRD; previously termed minimal residual disease) is an independent, postdiagnosis, prognostic indicator in acute myeloid leukemia (AML) that is important for risk stratification and treatment planning, in conjunction with other well-established clinical, cytogenetic, and molecular data assessed at diagnosis. MRD can be evaluated using a variety of multiparameter flow cytometry and molecular protocols, but, to date, these approaches have not been qualitatively or quantitatively standardized, making their use in clinical practice challenging. The objective of this work was to identify key clinical and scientific issues in the measurement and application of MRD in AML, to achieve consensus on these issues, and to provide guidelines for the current and future use of MRD in clinical practice. The work was accomplished over 2 years, during 4 meetings by a specially designated MRD Working Party of the European LeukemiaNet. The group included 24 faculty with expertise in AML hematopathology, molecular diagnostics, clinical trials, and clinical medicine, from 19 institutions in Europe and the United States.

Specific Depletion of Leukemic Stem Cells: Can MicroRNAs Make the Difference?

For over 40 years the standard treatment for acute myeloid leukemia (AML) patients has been a combination of chemotherapy consisting of cytarabine and an anthracycline such as daunorubicin. This standard treatment results in complete remission (CR) in the majority of AML patients. However, despite these high CR rates, only 30–40% (<60 years) and 10–20% (>60 years) of patients survive five years after diagnosis. The main cause of this treatment failure is insufficient eradication of a subpopulation of chemotherapy resistant leukemic cells with stem cell-like properties, often referred to as “leukemic stem cells” (LSCs). LSCs co-exist in the bone marrow of the AML patient with residual healthy hematopoietic stem cells (HSCs), which are needed to reconstitute the blood after therapy. To prevent relapse, development of additional therapies targeting LSCs, while sparing HSCs, is essential. As LSCs are rare, heterogeneous and dynamic, these cells are extremely difficult to target by single gene therapies. Modulation of miRNAs and consequently the regulation of hundreds of their targets may be the key to successful elimination of resistant LSCs, either by inducing apoptosis or by sensitizing them for chemotherapy. To address the need for specific targeting of LSCs, miRNA expression patterns in highly enriched HSCs, LSCs, and leukemic progenitors, all derived from the same patients’ bone marrow, were determined and differentially expressed miRNAs between LSCs and HSCs and between LSCs and leukemic progenitors were identified. Several of these miRNAs are specifically expressed in LSCs and/or HSCs and associated with AML prognosis and treatment outcome. In this review, we will focus on the expression and function of miRNAs expressed in normal and leukemic stem cells that are residing within the AML bone marrow. Moreover, we will review their possible prospective as specific targets for anti-LSC therapy.

Measurable residual disease testing in acute myeloid leukaemia

There is considerable interest in developing techniques to detect and/or quantify remaining leukaemia cells termed measurable or, less precisely, minimal residual disease (MRD) in persons with acute myeloid leukaemia (AML) in complete remission defined by cytomorphological criteria. An important reason for AML MRD-testing is the possibility of estimating the likelihood (and timing) of leukaemia relapse. A perfect MRD-test would precisely quantify leukaemia cells biologically able and likely to cause leukaemia relapse within a defined interval. AML is genetically diverse and there is currently no uniform approach to detecting such cells. Several technologies focused on immune phenotype or cytogenetic and/or molecular abnormalities have been developed, each with advantages and disadvantages. Many studies report a positive MRD-test at diverse time points during AML therapy identifies persons with a higher risk of leukaemia relapse compared with those with a negative MRD-test even after adjusting for other prognostic and predictive variables. No MRD-test in AML has perfect sensitivity and specificity for relapse prediction at the cohort- or subject levels and there are substantial rates of false-positive and -negative tests. Despite these limitations, correlations between MRD-test results and relapse risk have generated interest in MRD-test result-directed therapy interventions. However, convincing proof that a specific intervention will reduce relapse risk in persons with a positive MRD-test is lacking and needs testing in randomized trials. Routine clinical use of MRD-testing requires further refinements and standardization/harmonization of assay platforms and results reporting. Such data are needed to determine whether results of MRD-testing can be used as a surrogate end point in AML therapy trials. This could make drug-testing more efficient and accelerate regulatory approvals. Although MRD-testing in AML has advanced substantially, much remains to be done.

Multifactorial resistance to aminopeptidase inhibitor prodrug CHR2863 in myeloid leukemia cells: down-regulation of carboxylesterase 1, drug sequestration in lipid droplets and pro-survival activation ERK/Akt/mTOR

Aminopeptidase inhibitors are receiving attention as combination chemotherapeutic agents for the treatment of refractory acute myeloid leukemia. However, the factors determining therapeutic efficacy remain elusive. Here we identified the molecular basis of acquired resistance to CHR2863, an orally available hydrophobic aminopeptidase inhibitor prodrug with an esterase-sensitive motif, in myeloid leukemia cells. CHR2863 enters cells by diffusion and is retained therein upon esterase activity-mediated conversion to its hydrophilic active metabolite drug CHR6768, thereby exerting amino acid depletion. Carboxylesterases (CES) serve as candidate prodrug activating enzymes given CES1 expression in acute myeloid leukemia specimens. We established two novel myeloid leukemia sublines U937/CHR2863(200) and U937/CHR2863(5uM), with low (14-fold) and high level (270-fold) CHR2863 resistance. The latter drug resistant cells displayed: (i) complete loss of CES1-mediated drug activation associated with down-regulation of CES1 mRNA and protein, (ii) marked retention/sequestration of the prodrug, (iii) a substantial increase in intracellular lipid droplets, and (iv) a dominant activation of the pro-survival Akt/mTOR pathway. Remarkably, the latter feature coincided with a gain of sensitivity to the mTOR inhibitor rapamycin. These finding delineate the molecular basis of CHR2863 resistance and offer a novel modality to overcome this drug resistance in myeloid leukemia cells.

Reduced CD62L Expression on T Cells and Increased Soluble CD62L Levels Predict Molecular Response to Tyrosine Kinase Inhibitor Therapy in Early Chronic-Phase Chronic Myelogenous Leukemia

Purpose

Immunologic surveillance of minimal residual disease in chronic myelogenous leukemia (CML) may be relevant for long-term control or cure of CML. Little is known about immune-modulatory effects of nilotinib in vivo, potentially predicting response to therapy.

Patients and Methods

A prospective and comprehensive flow cytometry–based immunomonitoring program paralleled the ENEST1st clinical study, investigating 52 nilotinib-naïve patients with chronic-phase CML. Data were verified in independent validation cohorts.

Results

T cells of patients with CML at diagnosis expressed low l-selectin (CD62L) levels, which was not a result of proportional aberrations of T-cell subsets. Low numbers of CD62L-expressing CD4+ and CD8+ T cells correlated with higher Sokal score, increased spleen size, and high leukocyte and peripheral-blood blast counts. At month 6 during nilotinib therapy, CD62L expression returned to levels of healthy individuals. The level of CD62L loss on T cells directly correlated with the extent of soluble CD62L (sCD62L) elevation. In parallel, the proteolytic activity of tumor necrosis factor α–converting enzyme (TACE; ADAM17, CD156b), the metalloproteinase shedding CD62L, was increased at diagnosis and significantly decreased during nilotinib treatment. High CD62L+ expression on both CD4+ and CD8+ T cells and, vice versa, low sCD62L levels at CML diagnosis were linked to superior molecular responses. These findings were corroborated in independent validation cohorts.

Conclusion

We demonstrate the prognostic impact of CD62L shedding from T cells and increased sCD62L plasma levels at CML diagnosis on molecular response to tyrosine kinase inhibitor therapy in early chronic-phase CML. Functionally, decreased CD62L may be a consequence of increased TACE-mediated CD62L cleavage and potentially impairs immune-cell function. Larger prospective studies are ongoing to confirm the prognostic relevance of this finding.

Risk factors for relapse after allogeneic transplantation in acute myeloid leukemia

Acute myeloid leukemia is a clonal neoplasm derived from myeloid progenitor cells with a varying outcome. The initial goal of treatment is the achievement of complete remission, defined for over 40 years by morphology. However, without additional post-remission treatment the majority of patients relapse. In many cases of acute myeloid leukemia, allogeneic stem cell transplantation offers the best prospects of cure. In 2013, 5608 stem cell transplantations in acute myeloid leukemia were performed in Europe (5228 allogeneic and 380 autologous stem cell transplantations). Most stem cell transplantations are performed in first complete remission. However, despite a considerable reduction in the chance of relapse, in most studies, overall survival benefit of allogeneic stem cell transplantation is modest due to substantial non-relapse mortality. Here we discuss the many factors related to the risk of relapse after allogeneic stem cell transplantation.

Implementation of erythroid lineage analysis by flow cytometry in diagnostic models for myelodysplastic syndromes

Flow cytometric analysis is a recommended tool in the diagnosis of myelodysplastic syndromes. Current flow cytometric approaches evaluate the (im)mature myelo-/monocytic lineage with a median sensitivity and specificity of ~71% and ~93%, respectively. We hypothesized that the addition of erythroid lineage analysis could increase the sensitivity of flow cytometry. Hereto, we validated the analysis of erythroid lineage parameters recommended by the International/European LeukemiaNet Working Group for Flow Cytometry in Myelodysplastic Syndromes, and incorporated this evaluation in currently applied flow cytometric models. One hundred and sixty-seven bone marrow aspirates were analyzed; 106 patients with myelodysplastic syndromes, and 61 cytopenic controls. There was a strong correlation between presence of erythroid aberrancies assessed by flow cytometry and the diagnosis of myelodysplastic syndromes when validating the previously described erythroid evaluation. Furthermore, addition of erythroid aberrancies to two different flow cytometric models led to an increased sensitivity in detecting myelodysplastic syndromes: from 74% to 86% for the addition to the diagnostic score designed by Ogata and colleagues, and from 69% to 80% for the addition to the integrated flow cytometric score for myelodysplastic syndromes, designed by our group. In both models the specificity was unaffected. The high sensitivity and specificity of flow cytometry in the detection of myelodysplastic syndromes illustrates the important value of flow cytometry in a standardized diagnostic approach. The trial is registered at www.trialregister.nl as NTR1825; EudraCT n.: 2008-002195-10.

Multiparameter flow cytometry is instrumental to distinguish myelodysplastic syndromes from non-neoplastic cytopenias

Mandatory for the diagnosis of myelodysplastic syndromes (MDS) is the presence of dysplasia in >10% of cells within one or more cell lineages or presence of >15% ring sideroblasts or presence of MDS-associated cytogenetic (CG) abnormalities. Discrimination between neo-plastic and non-neoplastic causes of cytopenias can be challenging when dysplastic features by cytomorphology (CM) are minimal and CG abnormalities are absent or non-discriminating from other myeloid neoplastic disorders. This study evaluated a standard diagnostic approach in 379 patients with unexplained cytopenias and highlights the additional value of flow cytometry (FC) in patients with indeterminate CM and CG. CM reached no clear-cut diagnosis in 44% of the patients. Here, CG was able to identify two additional patients with MDS; other CG results did not reveal abnormalities or were not contributory. Based on the FC results, patients without a diagnosis by CM and CG were categorized 'no MDS-related features' (65%), 'limited number of MDS-related changes' (24%), and 'consistent with MDS' (11%). Patients were followed over time in an attempt to establish or confirm a diagnosis (median follow-up 391 d, range 20-1764). The specificity (true negative) of MDS-FC analysis calculated after follow-up was 95%. FC can aid as a valuable tool to exclude MDS when CM and additional CG are not conclusive in patients with cytopenia.

A Human Cell Line Model for Interferon-α Driven Dendritic Cell Differentiation

The CD34⁺ MUTZ-3 acute myeloid leukemia cell line has been used as a dendritic cell (DC) differentiation model. This cell line can be cultured into Langerhans cell (LC) or interstitial DC-like cells using the same cytokine cocktails used for the differentiation of their primary counterparts. Currently, there is an increasing interest in the study and clinical application of DC generated in the presence of IFNα, as these IFNα-DC produce high levels of inflammatory cytokines and have been suggested to be more potent in their ability to cross-present protein antigens, as compared to the more commonly used IL-4-DC. Here, we report on the generation of IFNα-induced MUTZ-DC. We show that IFNα MUTZ-DC morphologically and phenotypically display characteristic DC features and are functionally equivalent to “classic” IL-4 MUTZ-DC. IFNα MUTZ-DC ingest exogenous antigens and can subsequently cross-present HLA class-I restricted epitopes to specific CD8⁺ T cells. Importantly, mature IFNα MUTZ-DC express CCR7, migrate in response to CCL21, and are capable of priming naïve antigen-specific CD8⁺ T cells. In conclusion, we show that the MUTZ-3 cell line offers a viable and sustainable model system to study IFNα driven DC development and functionality.

Abstract 1820: Phosphoproteomics of a panel of AML cell lines reveals oncogenic signaling and candidate drivers

Background: Acute myeloid leukemia (AML) is a malignant hematopoietic stem cell disease, caused by a differentiation block at the level of immature progenitors, leading to massive accumulation of malignant cells in the bone marrow and suppression of normal hematopoiesis. The disease is highly heterogeneous with 2 year survival rates, after intensive chemotherapy regimens depending on cytogenetic and molecular risk factors, varying between 70% for patients with good risk and less than 10% in those with poor prognostic features.

In recent years clinical success has been achieved in the treatment of several cancer types with kinase inhibitors (KIs) and they may prove to be a valuable addition to standard therapy in AML. However, a proper rationale to select a suitable KI is still lacking. Phosphoproteomics based on tandem mass spectrometry (MS/MS) is a powerful approach for unbiased, global profiling of protein phosphorylation, and could identify aberrancies in signal transduction pathways and associated key kinases that may be suitable for targeted treatment with KIs.

The aim of this study is to identify candidate driver kinases and signaling routes that may be targets for kinase inhibitor treatment by analyzing 16 selected AML cell lines.

Methods: Sixteen different AML cell lines were cultured (EOL-1, HEL, HL-60, Kasumi-1, Kasumi-3, Kasumi-6, KG-1, KG-1a, ME-1, ML2, MM6, MOLM-13, MV-4-11, NB-4, OCI-AML3, THP1). For each cell line 10 mg protein lysate was processed. Phospho-Tyrosine containing peptides were captured from AML cell line lysates using the pY1000 antibody in an immunoprecipitation (IP) experiment. Both whole cell lysate and pTyr IP fractions were measured using nanoLC-MS/MS (2-hour gradient, QExactive). MaxQuant version 1.4.1.2 was used for phosphopeptide identification and label-free quantification.

Results: The whole phosphoproteome dataset of 16 AML cell lines contained 4853 identified phosphopeptides corresponding to 2280 phosphoproteins, including 138 phosphokinases. Ranking of phosphokinases identified in each of the 16 AML cell lines confirmed FLT3, PDGFRa, JAK2 and c-KIT as hyperphosphorylated kinases in AML cells with mutations in these genes. Interestingly, AML cell lines without known kinase-related genomic aberrations also showed high activation of several kinases which could be potential KI targets. Current data analysis will link phosphokinases to downstream phosphoprotein substrates and pathways, in order to prioritize (combinations of) candidate driver kinases for functional perturbation experiments.

Conclusion: Phosphoproteomics analysis of a panel of 16 AML cell lines showed differential (hyper-) activation of multiple kinases, including those already implicated in AML. The current analysis gives us insight into the heterogeneity of activated signaling pathways in AML and allows for the identification of possible new targets for treatment of AML with KIs.

Citation Format: Carolien van Alphen, Jacqueline Cloos, Sander R. Piersma, Jaco C. Knol, Thang V. Pham, Gert J. Ossenkoppele, Henk Verheul, Jeroen JWM Janssen, Connie R. Jimenez. Phosphoproteomics of a panel of AML cell lines reveals oncogenic signaling and candidate drivers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1820. doi:10.1158/1538-7445.AM2015-1820

Differential capacity of human interleukin-4 and interferon-α monocyte-derived dendritic cells for cross-presentation of free versus cell-associated antigen

Dendritic cells (DC) vaccination is a potent therapeutic approach for inducing tumor-directed immunity, but challenges remain. One of the particular interest is the induction of an immune response targeting multiple (unknown) tumor-associated antigens (TAA), which requires a polyvalent source of TAA. Previously, we described the preferred use of apoptotic cell-derived blebs over the larger apoptotic cell remnants, as a source of TAA for both in situ loading of skin-resident DC and in vitro loading of monocyte-derived DC (MoDC). Recent reports suggest that MoDC cultured in the presence of GM-CSF supplemented with IFNα (IFNα MoDC), as compared to IL-4 (IL-4 MoDC), have an increased capacity to cross-present antigen to CD8(+) T cells. As culture conditions, maturation methods and antigen sources differ between the conducted studies, we analyzed the functional differences between IL-4 MoDC and IFNα MoDC, loaded with blebs, in a head-to-head comparison using commonly used protocols. Our data show that both MoDC types are potent (cross-) primers of CD8(+) T cells. Whereas IFNα MoDC were more potent in their capacity to cross-present a 25-mer MART-1 synthetic long peptide (SLP) to a MART-1aa26-35 recognizing CD8(+) T cell line, IL-4 MoDC proved more potent cross-primers of antigen-specific CD8(+) T cells when loaded with blebs. The latter is likely due to the observed greater capacity of IL-4 MoDC to ingest apoptotic blebs. In conclusion, our data indicate the use of IFNα MoDC over IL-4 MoDC in the context of DC vaccination with SLP, whereas IL-4 MoDC are preferred for vaccination with bleb-derived antigens.

Absence of leukaemic CD34+ cells in acute myeloid leukaemia is of high prognostic value: a longstanding controversy deciphered

Primary resistance and relapses after initial successful treatment are common in acute myeloid leukaemia and therefore outcome remains poor. More accurate risk group stratification and effective personalized risk adapted treatment are necessary to improve outcome. In the last two decades, controversial results have been published concerning the prognostic relevance of CD34 expression. In this study of 706 acute myeloid leukaemia patients, we established a new flow cytometric-based CD34-definition, without use of cut-off values. We discriminated CD34-positive (n = 548) and CD34-negative (n = 158) patients by the presence or absence of neoplastic CD34+ cells, respectively. CD34-status was defined using aberrant immunophenotypes and validated using molecular phenotypes. This new definition of CD34 enables strong prediction of treatment outcome in the entire patient group and in several risk subgroups. Previously observed discrepancies in prognostic impact of CD34 protein expression using cut-offs (5-20%) can now entirely be explained by considering the number of CD34-negative cases. In the total patient group, the absence of neoplastic CD34-positive cells is paralleled by low levels of minimal residual disease, suggesting relative therapy sensitivity and explaining longer survival. Overall, we present CD34 surface expression as a relatively simple, powerful and independent predictor of clinical outcome, now warranting incorporation in acute myeloid leukaemia risk stratification.

Tyrosine kinase inhibitors improve long-term outcome of allogeneic hematopoietic stem cell transplantation for adult patients with Philadelphia chromosome positive acute lymphoblastic leukemia

This study aimed to determine the impact of tyrosine kinase inhibitors given pre- and post-allogeneic stem cell transplantation on long-term outcome of patients allografted for Philadelphia chromosome-positive acute lymphoblastic leukemia. This retrospective analysis from the EBMT Acute Leukemia Working Party included 473 de novo Philadelphia chromosome-positive acute lymphoblastic leukemia patients in first complete remission who underwent an allogeneic stem cell transplantation using a human leukocyte antigen-identical sibling or human leukocyte antigen-matched unrelated donor between 2000 and 2010. Three hundred and ninety patients received tyrosine kinase inhibitors before transplant, 329 at induction and 274 at consolidation. Kaplan-Meier estimates of leukemia-free survival, overall survival, cumulative incidences of relapse incidence, and non-relapse mortality at five years were 38%, 46%, 36% and 26%, respectively. In multivariate analysis, tyrosine-kinase inhibitors given before allogeneic stem cell transplantation was associated with a better overall survival (HR=0.68; P=0.04) and was associated with lower relapse incidence (HR=0.5; P=0.01). In the post-transplant period, multivariate analysis identified prophylactic tyrosine-kinase inhibitor administration to be a significant factor for improved leukemia-free survival (HR=0.44; P=0.002) and overall survival (HR=0.42; P=0.004), and a lower relapse incidence (HR=0.40; P=0.01). Over the past decade, administration of tyrosine kinase inhibitors before allogeneic stem cell transplantation has significantly improved the long-term allogeneic stem cell transplantation outcome of adult Philadelphia chromosome-positive acute lymphoblastic leukemia. Prospective studies will be of great interest to further confirm the potential benefit of the prophylactic use of tyrosine kinase inhibitors in the post-transplant setting.

Improved risk stratification by the integration of the revised international prognostic scoring system with the myelodysplastic syndromes comorbidity index

Myelodysplastic syndromes (MDS) comprise bone marrow failure diseases with a diverse clinical outcome. For improved risk stratification, the International Prognostic Scoring System (IPSS) has recently been revised (IPSS-R). This single-centre study aimed to validate the IPSS-R and to evaluate prior prognostic scoring systems for MDS. We retrospectively analysed 363 patients diagnosed with MDS according to the FAB criteria between 2000 and 2012. The IPSS, MD Anderson Risk Model Score (MDAS), World Health Organisation (WHO)-classification based Prognostic Scoring System (WPSS), refined WPSS (WPSS-R), IPSS-R and MDS-Comorbidity Index (MDS-CI) were applied to 222 patients considered with primary MDS following the WHO criteria and their prognostic power was investigated. According to the IPSS-R, 18 (8%), 81 (37%), 50 (23%), 43 (19%) and 30 (13%) patients were classified as very low, low, intermediate, high and very high risk with, respectively, a median overall survival of 96 (95% Confidence interval (CI) not reached), 49 (95% CI 34-64), 22 (95% CI 0-49), 19 (95% CI 11-27) and 10 (95% CI 6-13) months (p<.000). The IPSS-R showed improved prognostic power as compared to the IPSS, MDAS, WPSS and WPSS-R. Furthermore, the MDS-CI refined the risk stratification of MDS patients stratified according to the IPSS-R. In conclusion, accounting for the disease status by means of the IPSS-R and comorbidity through the MDS-CI considerably improves the prognostic assessment in MDS patients.

Priming of PRAME- and WT1-specific CD8+ T cells in healthy donors but not in AML patients in complete remission: Implications for immunotherapy

Active immunotherapy may prevent the relapse of acute myeloid leukemia (AML) by inducing leukemia-specific T cells. Here, we investigated whether Wilms’ tumor 1 (WT1) and preferentially expressed antigen in melanoma (PRAME)-specific T cells could be induced upon the priming of healthy donor- and AML patient-derived T cells with HLA-A2-matched, peptide-loaded allogeneic dendritic cells. AML-reactive, tetramer (Tm)-binding and interferon-producing, cytotoxic T lymphocytes specific for PRAME could readily be isolated from healthy individuals and maintained in culture. In this setting, priming efficacy was significantly higher for PRAME than for WT1. The priming of T cells from patient-derived material proved to be near-to-impossible: No leukemia-associated antigen (LAA)-specific T cell could be primed in 4 patients that had recently achieved a complete response (CR), and in only 1 out of 3 patients exhibiting a sustained CR we did observe WT1-specific T cells, though with a low frequency. These findings suggest that the functionality and/or repertoire of T cells differ in healthy subjects and AML patients in CR, and may have repercussions for the implementation of active vaccination approaches against AML.