Complete remission after the first cycle of induction chemotherapy determines the clinical efficacy of relapse-preventive immunotherapy in acute myeloid leukaemia

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Immunotherapy with HDC/IL-2 may be clinically efficacious in acute myeloid leukemia of normal karyotype

Immunotherapy with histamine dihydrochloride and low-dose interleukin-2 (HDC/IL-2) reduces the risk of relapse in the post-chemotherapy phase of acute myeloid leukemia (AML). Here we report the results of exploratory analyses of the clinical efficacy of HDC/IL-2 in AML with focus on the impact of karyotype aberrations in leukemic cells. Post-hoc analyses of phase III trial data suggested that HDC/IL-2 is primarily beneficial for patients with AML of normal karyotype. These results may be helpful in the selection of patients who are suitable for therapy and in the design of future immunotherapy protocols aiming at further defining the mechanism of relapse prevention by HDC/IL-2

Immunotherapy and immunosuppression in myeloid leukemia

Acute myeloid leukemia (AML) and chronic myelomonocytic leukemia (CMML) are potentially life-threatening blood cancers characterized by the expansion of malignant myeloid cells in bone marrow and other organs. This thesis aimed at contributing to the understanding of the role of natural killer (NK) cells in AML and CMML with focus on the potential impact of the immunosuppression exerted by reactive oxygen species (ROS) formed by the myeloid cell NOX2 enzyme. The thesis work has comprised in vitro studies of interactions between NK cells and primary myeloid leukemic cells along with analyses of NK cell repertoires in a clinical trial using a NOX2 inhibitor, histamine dihydrochloride (HDC) in conjunction with the NK cell-activating cytokine interleukin-2 (IL-2) for the prevention of relapse of AML after the completion of chemotherapy. Paper I reports that the functions and viability of cytotoxic lymphocytes, including NK cells, were compromised by ROS produced by leukemic myeloid cells recovered from patients with CMML. The results are thus suggestive of a novel mechanism of leukemia-induced immunosuppression in this disease. Paper II analyzed aspects of myeloid cell populations in AML using blood samples from a clinical phase IV trial where AML patients (n=84) received HDC in conjunction with IL-2. The results imply that HDC may exert anti-leukemic efficacy by facilitating the maturation of myeloid cells, which impacts on the efficiency of immunotherapy with HDC/IL-2. In papers III and IV we explored the role of killer cell immunoglobulin-like receptors (KIR) for the relapse and survival of AML patients receiving HDC/IL-2. The results suggest that a subset of immature NK cells with low KIR expression may determine clinical outcome. In paper IV we further analyzed results from the above-referenced phase IV trial and observed that a past cytomegalovirus (CMV) infection predicted high relapse risk and poor survival, presumably by reducing the pool of immature NK cells. The results of paper V suggest that a dimorphism in the leader peptide of HLA-B is relevant to NK cell-mediated killing of AML cells and to the outcome of immunotherapy. In conclusion, this thesis work presents novel aspects of myeloid cell-induced immunosuppression in AML and CMML and identifies NK cell subsets of potential relevance to the benefit of immunotherapy with HDC/IL-2

NOX2-dependent immunosuppression in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is a myeloproliferative and myelodysplastic neoplasm with few treatment options and dismal prognosis. The role of natural killer (NK) cells and other antileukemic lymphocytes in CMML is largely unknown. We aimed to provide insight into the mechanisms of immune evasion in CMML with a focus on immunosuppressive reactive oxygen species (ROS) formed by the myeloid cell NADPH oxidase-2 (NOX2). The dominant population of primary human CMML cells was found to express membrane-bound NOX2 and to release ROS, which, in turn, triggered extensive PARP-1-dependent cell death in cocultured NK cells, CD8(+) T effector memory cells, and CD8(+) T effector cells. Inhibitors of ROS formation and scavengers of extracellular ROS prevented CMML cell-induced lymphocyte death and facilitated NK cell degranulation toward Ab-coated, primary CMML cells. In patients with CMML, elevation of immature cell counts (CD34(+)) in blood was associated with reduced expression of several NK cell-activating receptors. We propose that CMML cells may use extracellular ROS as a targetable mechanism of immune escape

Determinants for Effective ALECSAT Immunotherapy Treatment on Autologous Patient-Derived Glioblastoma Stem Cells.

Glioblastoma (GBM) is the most aggressive primary brain tumor with a median survival of less than 15 months, emphasizing the need for better treatments. Immunotherapy as a treatment for improving or aiding the patient's own immune defense to target the tumor has been suggested for GBM. A randomized clinical trial of adoptive cell transfer using ALECSAT (Autologous Lymphoid Effector Cells Specific Against Tumor Cells) is currently ongoing in Sweden. Here we performed a paired pre-clinical study to investigate the composition and in vitro effect of ALECSAT and identify determinants for the effect using autologous GBM-derived cancer stem cells (CSC), immunocytochemistry and flow cytometry. We show a clear dose-response relationship of ALECSAT on CSC, suggesting that the number of infused cells is of importance. In addition, the in vitro effect of ALECSAT on CSC correlated significantly to the blood count of T helper (Th) cells in the patient indicating a potential benefit of collecting cells for ALECSAT preparation at an even earlier stage when patients generally have a better blood count. The factors identified in this study will be important to consider in the design of future immunotherapy trials to achieve prolonged survival