Willemijn van den Ancker

MicroRNA profiling can classify acute leukemias of ambiguous lineage as either acute myeloid leukemia or acute lymphoid leukemia.

Purpose: Classification of acute leukemia is based on the commitment of leukemic cells to the myeloid or the lymphoid lineage. However, a small percentage of acute leukemia cases lack straightforward immunophenotypical lineage commitment. These leukemias of ambiguous lineage represent a heterogeneous category of acute leukemia that cannot be classified as either acute myeloid leukemia (AML) or acute lymphoid leukemia (ALL). The lack of clear classification of acute leukemias of ambiguous lineage as either AML or ALL is a hurdle in treatment choice for these patients. Experimental Design: Here, we compared the microRNA (miRNA) expression profiles of 17 cases with acute leukemia of ambiguous lineage and 16 cases of AML, B-cell acute lymphoid leukemia (B-ALL), and T-cell acute lymphoid leukemia (T-ALL). Results: We show that leukemias of ambiguous lineage do not segregate as a separate entity but exhibit miRNA expression profiles similar to AML, B-ALL, or T-ALL. We show that by using only 5 of the most lineage-discriminative miRNAs, we are able to define acute leukemia of ambiguous lineage as either AML or ALL. Conclusion: Our results indicate the presence of a myeloid or lymphoid lineage-specific genotype, as reflected by miRNA expression, in these acute leukemias despite their ambiguous immunophenotype. miRNA-based classification of acute leukemia of ambiguous lineage might be of additional value in therapeutic decision making. Clin Cancer Res; 19(8); 2187–96. ©2013 AACR.

Absence of Class II-Associated Invariant Chain Peptide on Leukemic Blasts of Patients Promotes Activation of Autologous Leukemia-Reactive CD4(+) T Cells

Immune escape in cancer poses a substantial obstacle to successful cancer immunotherapy. Multiple defects in HLA class I antigen presentation exist in cancer that may contribute to immune escape, but less is known about roles for HLA class II antigen presentation. On class II(+) leukemic blasts, the presence of class II-associated invariant chain peptide (CLIP) is known to be correlated with poor survival in acute myeloid leukemia (AML). In this study, we evaluated the functional significance of CLIP expression on leukemic blasts of AML patients. CD4(+) T cells from patients were cocultured with autologous CLIP(-) and CLIP(+) primary leukemic blasts and analyzed for several functional parameters by flow cytometry. Increased HLA-DR and IFN-γ expression was observed for CD4(+) T cells stimulated with CLIP(-) leukemic blasts, in contrast to CLIP(+) leukemic blasts, which indicated an activation and polarization of the CD4(+) T cells toward T-helper 1 cells. In addition, CLIP(-) leukemic blasts induced greater outgrowth of effector memory CD4(+) T cells (with HLA-DR-restricted T-cell receptor Vβ repertoires) that were associated with better leukemia-specific reactivity than with CLIP(+) leukemic blasts. Our findings offer a clinical rationale to downmodulate CLIP on leukemic blasts as a strategy to degrade immune escape and improve leukemia-specific T-cell immunity in AML patients.

Recent advances in antigen-loaded dendritic cell-based strategies for treatment of minimal residual disease in acute myeloid leukemia

Therapeutic vaccination with dendritic cells (DCs) is recognized as an important experimental therapy for the treatment of minimal residual disease in acute myeloid leukemia. Many sources of leukemia-associated antigens and different methods for antigen loading of DCs have been used in an attempt to optimize anti-tumor responses. For instance, monocyte-derived DCs have been loaded with apoptotic whole-cell suspensions, necrotic cell lysates, tumor-associated peptides, eluted peptides and cellular DNA or RNA. Furthermore, monocyte-derived DCs can be chemically or electrically fused with leukemic blasts, and DCs have been cultured out of leukemic blasts. However, it remains a challenge in cancer immunotherapy to identify which of these methods is the most optimal for antigen loading and activation of DCs. This review discusses recent advances in DC research and the application of this knowledge towards new strategies for antigen loading of DCs in the treatment of minimal residual disease in acute myeloid leukemia.

Impaired antigen presentation in neoplasia: basic mechanisms and implications for acute myeloid leukemia

During onset, treatment and progression of acute myeloid leukemia (AML), inadequate immune responses against certain myeloid leukemic blasts might be associated with the occurrence of minimal residual disease and subsequent relapse. Several studies on this subject have demonstrated that, in general, solid tumor cells are able to avoid CD8(+) cytotoxic T-cell recognition by downregulating HLA class I-restricted presentation of tumor-associated antigens. In tumor cells that can express HLA class II molecules, such as myeloid leukemic blasts, abnormalities in the processing pathways of endogenous antigens could also result in impaired HLA class II-restricted tumor-associated antigen presentation to CD4(+) T helper cells. More insight into impaired tumor-associated antigen presentation by myeloid leukemic blasts could explain their escape from immune recognition and might be crucial for selecting appropriate strategies to improve whole-cell or dendritic cell-based tumor vaccine efficacy in the treatment of AML 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.

Chronic myeloid leukemia lysate-loaded dendritic cells induce T-cell responses towards leukemia progenitor cells

Treatment of chronic myeloid leukemia with tyrosine kinase inhibitors, such as imatinib mesylate, dasatinib and nilotinib, results in high rates of cytogenetic and molecular responses. However, in many patients, minimal residual disease is detected by molecular techniques. Since chronic myeloid leukemia cells are particularly good targets for immune surveillance mechanisms, we explored active specific immunotherapy using leukemia lysate-loaded dendritic cells in vitro. Our data show the potency of dendritic cell-based vaccination strategies for the induction of T cell-mediated responses to eradicate minimal residual disease.

Back to basics: in search of the optimal dendritic cell for vaccination in AML.

Acute myeloid leukemia (AML) is characterized by prolifration of clonal neoplastic myeloid hematopoietic precursor ells and impaired production of normal hematopoiesis. hemotherapeutic induction regimens establish complete emission in 70–80% of adults. Despite intensive consoliation chemotherapy, AML relapses in 50% of patients due o the presence of minimal residual disease (MRD) [1]. In the ast decade search for new treatment modalities has indicated he important role of the immune system in the prevention and ontrol of leukemia, shown for instance by the graft versus eukemia effect induced by allogeneic stem cell transplantaion (SCT). Furthermore, the critical role of dendritic cells DCs) in induction, regulation and maintenance of primary mmune responses, including specific antitumor responses, as demonstrated. This has led to development of DC vacination strategies as a way to actively induce antitumor mmunity. Nowadays, DC vaccination is recognized as an mportant investigational therapy due to the DC’s unique ntigen presenting capacity, thereby circumventing immunouppressive features of leukemic cells [2]. The first steps own the road towards DC vaccination in AML have been aken and small clinical trials have been reported [3–6]. The ack of clinical responses evoked important issues concerning he broad array from the generation of DC vaccines towards accination of the patient. In this issue of Leukemia Research, Lee et al. returned to he starting point of DC based vaccination and compared arious sources of DCs for vaccination purposes from a linical point of view. Lee et al. investigated the use of alloeneic monocyte derived DCs (MoDCs) from HLA-matched onors, autologous MoDCs obtained at time of complete emission and DCs cultured from leukemic cells (leukemic Cs) [7]. A systematic approach as detailed in this article is f great value to pave the way for the proper development of C vaccination protocols. s o p

High class II-associated invariant chain peptide expression on residual leukemic cells is associated with increased relapse risk in acute myeloid leukemia

The presence of class II-associated invariant chain (CLIP) on leukemic cells is negatively associated with clinical outcome in untreated acute myeloid leukemia (AML). CLIP plays a role in the immune escape of leukemic cells, suggesting that it impairs the immunogenicity of minimal residual disease (MRD) cells causing a relapse. Here, we demonstrate that CLIP expression on leukemia-associated phenotype (LAP)-positive cells during follow-up is significantly correlated with a shortened relapse-free survival, even in those patients who are generally considered as MRD(low) (0.01-0.1% LAP(+) cells). Consequently, CLIP evaluation could be of additional value in the evaluation of MRD to predict a relapse of AML.

Challenging diagnosis in a patient with clear lymphoid immunohistochemical features and myeloid morphology: Mixed phenotype acute leukemia with erythrophagocytosis

Acute leukemia (AL) is classified according to commitment owards either the myeloid or lymphoid cell lineage. In about 4% f acute leukemias it is unclear whether the blasts are of myeloid r lymphoid origin. These AL with both myeloid and lymphoid haracteristics represent a worse prognostic subgroup and it is till a matter of debate whether patients may benefit from an cute lymphoid leukemia (ALL) or acute myeloid leukemia (AML) reatment. In the WHO2008 criteria for defining mixed phenoype acute leukemia (MPAL), important changes have been made in efining cell line specific and characterizing markers in AL as comared to European Group for the Immunological Characterization f Leukemias (EGIL) criteria incorporated in the WHO2001. In the HO2001 criteria a weighted points system is used for defining a iphenotypic Acute Leukemia (BAL) to be Myeloid, Bor T-cell. In his scoring system at least one additional lineage defining marker

Class II-associated invariant chain peptide as predictive immune marker in minimal residual disease in acute myeloid leukemia

The majority of patients with acute myeloid leukemia (AML) reach complete remission after high-dose chemotherapy. Still, half of these patients experience a relapse due to presence of minimal residual disease (MRD). Here we discuss the poor prognostic role of class II-associated invariant chain peptide (CLIP) expression on residual leukemic cells.The majority of patients with acute myeloid leukemia (AML) reach complete remission after high-dose chemotherapy. Still, half of these patients experience a relapse due to presence of minimal residual disease (MRD). Here we discuss the poor prognostic role of class II-associated invariant chain peptide (CLIP) expression on residual leukemic cells.