Impaired NK cells and increased T regulatory cell numbers during cytotoxic maintenance therapy in AML
Introduction
Curative treatment approaches for patients with acute myeloid leukemia (AML) are based on intensive induction chemotherapy consisting of cytarabine and anthracyclines. Despite high initial complete remission (CR) rates, clinical outcome is still poor, with an age-dependent 5-year overall survival rate of 15–40% [1], [2]. Relapse remains the biggest clinical problem; therefore, the choice of post-remission therapy is critical. One post-remission therapy approach developed by the AML Cooperative Group (AML-CG) has been prolonged cyclic maintenance therapy consisting of monthly courses of cytarabine in combination with various second agents (daunorubicin, tioguanine, or cyclophosphamide) in a rotating sequence for up to two years (Supplementary Fig. S1). It was shown that the addition of this treatment to consolidation therapy was able to improve the remission-free survival in AML patients compared to consolidation therapy alone [3], [4]; therefore, this post-remission treatment is regularly used within the clinical centers associated with the AML-CG. However, the mechanism for the clinical benefit of cyclic maintenance therapy has not been elucidated. There is no data available on potential conversion of minimal residual disease during this treatment. Importantly, hemato-oncologists are becoming increasingly aware that the effect of conventional chemotherapeutic agents has to be evaluated in the context of the patients’ immune system [5], [6].
So far, there are only few studies that have analyzed the immune status of AML patients in CR after intensive induction chemotherapy. In one of the first studies, a reduction of overall lymphocytes and specifically T helper (TH) cells was found [7]. Two reports showed that natural killer (NK) cell counts [8] as well as TC1 and TH1 levels [9] are reduced compared to healthy controls. In contrast, frequency and function of T regulatory (Treg) cells were shown to be elevated in CR, albeit to a lower degree compared to primary diagnosis [10]. Similarly, an early expansion of Treg cells after induction timed sequential chemotherapy was demonstrated [11].
Even less is known about the influence of cytotoxic maintenance therapy on the immune system. In patients with various solid tumors, cyclophosphamide has been repeatedly described to induce a temporary reduction in frequency and suppressor function of Treg cells when given iteratively in low doses (“metronomically”) [12], [13], [14]. A different study demonstrated differentiation of Th17 cells after cyclophosphamide therapy [15]. Effects of cyclophosphamide therapy in AML patients and of antimetabolite or anthracycline treatment on the different immune cell populations have not been described in detail. Thus, it is not known what effects the cyclic maintenance therapy has on the immune system of AML patients.
In the present study, we set out to first analyze the immune status of AML patients in CR after intensive induction and consolidation chemotherapy, focusing on frequency and function of different NK and T cell populations including Treg cells. We then for the first time provide data on immunomonitoring of AML patients that received cyclic cytotoxic maintenance therapy within the AML-CG 2008 study. This data will be of great interest for future considerations of immunotherapeutic strategies in post-remission and for possible combinatorial approaches with cytotoxic therapy for AML.
Section snippets
Peripheral blood samples
After written informed consent in accordance with the Declaration of Helsinki and approval by the Institutional Review Board of the Ludwig-Maximilians-Universität (Munich, Germany), peripheral blood (PB) was obtained from 15 healthy donors (HDs) and 17 AML patients treated in our department within the German AML-CG trial 2008 or analogous to the study protocol. All patients received intensive induction and consolidation chemotherapy and achieved CR as defined by cytomorphology of bone marrow
AML patients prior to maintenance therapy have reduced absolute NK, TH, and Treg cell counts
PB was obtained from 13 AML patients (#1–13; Supplementary Table S1) before the application of maintenance chemotherapy and from 6 HDs. PBMCs were isolated, stained with antibodies for T and NK cell markers, as specified in Section 2, and analyzed by flow cytometry. Absolute cell counts of different cell populations were calculated by multiplying their percentage within the lymphocyte gate with the absolute lymphocyte count according to the hemogram of the respective blood donor.
The total T
Discussion
Multiple trials have been conducted on the efficacy of cytotoxic regimens for the treatment of AML, but the immunomodulatory effect of these treatments has rarely been addressed. However, there is mounting evidence that the effect of conventional chemotherapeutic agents cannot be completely evaluated without considering their effect on the patient's immune system [5], [6]. Besides, there is a high interest in the development of novel immunotherapeutic strategies for post-remission therapy to
Funding
This work was supported by funds from BayImmuNet, the Bavarian Immunotherapy Network (http://www.bayimmunet.de). The funders had no role in study design, data collection, analysis and interpretation, decision to publish, or preparation of the manuscript.
Conflict of interest statement
Katharina Gellhaus is employed by Epiontis. All other authors declare no conflict of interest.
Acknowledgments
The authors thank Patrick Palluch for his excellent technical assistance.
Contributions: Research design: FSL, WH, BB, MS; performance of the experiments and collection of the data: FSL, RL, KG, BB; analysis and interpretation of the data: FSL, RL, BB, MS; writing of the manuscript: FSL, MS; supervision of the project: MS.
References (28)
- et al.
Acute myeloid leukaemia in adults
Lancet
(2013) - et al.
Early lymphocyte recovery after intensive timed sequential chemotherapy for acute myelogenous leukemia: peripheral oligoclonal expansion of regulatory T cells
Blood
(2011) - et al.
The biology of human natural killer-cell subsets
Trends Immunol
(2001) - et al.
Selective killing of candidate AML stem cells by antibody targeting of IL1RAP
Blood
(2013) - et al.
Generation and preclinical characterization of a Fc-optimized GITR-Ig fusion protein for induction of NK cell reactivity against leukemia
Mol Ther
(2013) Treatment of acute myeloid leukemia: are we making progress
Hematology Am Soc Hematol Educ Program
(2012)- et al.
Intensified induction and consolidation with or without maintenance chemotherapy for acute myeloid leukemia (AML): two multicenter studies of the German AML Cooperative Group
J Clin Oncol
(1985) - et al.
6-Thioguanine, cytarabine, and daunorubicin (TAD) and high-dose cytarabine and mitoxantrone (HAM) for induction, TAD for consolidation, and either prolonged maintenance by reduced monthly TAD or TAD-HAM-TAD and one course of intensive consolidation by sequential HAM in adult patients at all ages with de novo acute myeloid leukemia (AML): a randomized trial of the German AML Cooperative Group
J Clin Oncol
(2003) - et al.
Immunological aspects of cancer chemotherapy
Nat Rev Immunol
(2008) - et al.
Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer
Cell Death Differ
(2013)
Immunological monitoring in remission acute myeloid leukemia during maintenance therapy
Haematol Blood Transfus
Quantification and cytokine production of circulating lymphoid and myeloid cells in acute myelogenous leukaemia
Leukemia
Intensive chemotherapy for acute myeloid leukemia differentially affects circulating TC1, TH1, TH17 and TREG cells
BMC Immunol
Increased frequency and suppression by regulatory T cells in patients with acute myelogenous leukemia
Clin Cancer Res
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