Serum-free generation and quantification of functionally active Leukemia-derived DC is possible from malignant blasts in acute myeloid leukemia and myelodysplastic syndromes

Microenvironmental Features Driving Immune Evasion in Myelodysplastic Syndromes and Acute Myeloid Leukemia

Bone marrow, besides the known functions of hematopoiesis, is an active organ of the immune system, functioning as a sanctuary for several mature immune cells. Moreover, evidence suggests that hematopoietic stem cells (the bone marrow’s functional unit) are capable of directly sensing and responding to an array of exogenous stimuli. This chronic immune stimulation is harmful to normal hematopoietic stem cells, while essential for the propagation of myeloid diseases, which show a dysregulated immune microenvironment. The bone marrow microenvironment in myelodysplastic syndromes (MDS) is characterized by chronic inflammatory activity and immune dysfunction, that drive excessive cellular death and through immune evasion assist in cancer cell expansion. Acute myeloid leukemia (AML) is another example of immune response failure, with features that augment immune evasion and suppression. In this review, we will outline some of the functions of the bone marrow with immunological significance and describe the alterations in the immune landscape of MDS and AML that drive disease progression.

In Vitro Generated Dendritic Cells of Leukemic Origin Predict Response to Allogeneic Stem Cell Transplantation in Patients With AML and MDS

Allogeneic stem cell transplantation (alloSCT) is the treatment of choice for many patients with acute myeloid leukemia (AML) and myelodysplastic syndrome. The presentation of leukemic or allospecific antigens by malignant blasts is regarded as a crucial trigger for an effective allogeneic immune response. Conversely, insufficient stimulatory capacity by the leukemic blasts is thought to be a relevant escape mechanism from cellular immunotherapy (alloSCT). Our purpose was to test, whether the ability of malignant blasts to differentiate in vitro toward dendritic cells of leukemic origin (DCleu) is associated with clinical outcome. We isolated leukemic blasts from peripheral blood or bone marrow of AML and myelodysplastic syndrome patients before alloSCT (n=47) or at relapse after alloSCT (n=22). A panel of 6 different assays was used to generate DCleu in vitro. Results were correlated with clinical outcome. DCleu could be generated from all 69 samples. Significantly higher mean frequencies of DCleu were found in clinical long-term responders versus nonresponders to SCT (76.8% vs. 58.8%, P=0.006). Vice versa, the chance for response to SCT was significantly higher, if a DCleu+/dendritic cells (DC) ratio of >50% could be reached in vitro (P=0.004). Those patients were characterized by a longer time to relapse (P=0.04) and by a higher probability for leukemia-free survival (P=0.005). In vitro generation of DC and DCleu from leukemic blasts correlated with the clinical outcome. This observation may support a role of leukemic antigen presentation by "leukemia-derived DC" for the stimulation of an allogeneic immune response in AML.

Conversion of AML-blasts to leukemia-derived dendritic cells (DCleu) in 'DC-culture-media' shifts correlations of released chemokines with antileukemic T-cell reactions

Dendritic cells (DC) and T-cells are mediators of CTL-responses. Autologous (from patients with acute myeloid leukaemia (AML) or myelodysplasia (MDS)) or allogeneic (donor)-T-cells stimulated by DC_leu, gain an efficient lysis of naive blasts, although not in every case. CXCL8, -9, -10, CCL2, -5 and Interleukin (IL-12) were quantified by Cytometric Bead Array (CBA) in supernatants from 5 DC-generating methods and correlated with AML-/MDS-patients' serum-values, DC-/T-cell-interactions/antileukemic T-cell-reactions after mixed lymphocyte culture (MLC) and patients' clinical course. The blast-lytic activity of T-cells stimulated with DC or mononuclear cells (MNC) was quantified in a cytotoxicity assay. Despite great variations of chemokine-levels, correlations with post-stimulation (after stimulating T-cells with DC in MLC) improved antileukemic T-cell activity were seen: higher released chemokine-values correlated with improved T-cells' antileukemic activity (compared to stimulation with blast-containing MNC) - whereas with respect to the corresponding serum values higher CXCL8-, -9-, and -10- but lower CCL5- and -2-release correlated with improved antileukemic activity of DC-stimulated (vs. blast-stimulated) T-cells. In DC-culture supernatants higher chemokine-values correlated with post-stimulation improved antileukemic T-cell reactivity, whereas higher serum-values of CXCL8, -9, and -10 but lower serum-values of CCL5 and -2 correlated with post-stimulation improved antileukemic T-cell-reactivity. In a context of 'DC'-stimulation (vs serum) this might point to a change of (CCL5 and -2-associated) functionality from a more 'inflammatory' or 'tumor-promoting' to a more 'antitumor'-reactive functionality. This knowledge could contribute to develop immune-modifying strategies that promote antileukemic (adaptive) immune-responses.

Dendritic Cells of Leukemic Origin: Specialized Antigen-Presenting Cells as Potential Treatment Tools for Patients with Myeloid Leukemia

The prognosis of elderly patients with acute myeloid leukemia (AML) and high-grade myelodysplastic syndrome (MDS) is limited due to the lack of therapy options and high relapse rates. Dendritic cell (DC)-based immunotherapy seems to be a promising treatment tool. DC are potent antigen-presenting cells and play a pivotal role on the interface of the innate and the adaptive immune system. Myeloid leukemia blasts can be converted to DC of leukemic origin (DC_leu), expressing costimulatory molecules along with the whole leukemic antigen repertoire of individual patients. These generated DC_leu are potent stimulators of various immune reactive cells and increase antileukemic immunity ex vivo. Here we review the generating process of DC/DC_leu from leukemic peripheral blood mononuclear cells as well as directly from leukemic whole blood with "minimized" Kits to simulate physiological conditions ex vivo. The purpose of adoptive cell transfer of DC/DC_leu as a vaccination strategy is discussed. A new potential therapy option with Kits for patients with myeloid leukemia, which would render an adoptive DC/DC_leu transfer unnecessary, is presented. In summary, DC/DC_leu-based therapies seem to be promising treatment tools for patients with AML or MDS but ongoing research including trials in animals and humans have to be performed.

Dendritic cell vaccines for leukemia patients

Dendritic cells are the most professional antigen-presenting cells to elicit T-cellular responses toward microbial agents and cancer cells. The graft-versus-leukemia effect observed after allogeneic stem cell transplantation strongly suggests that T lymphocytes play a major role in the rejection of leukemic cells. This graft-versus-leukemia effect might be enhanced through dendritic cell vaccination. The characterization of leukemia-specific antigens eliciting immune responses in the autologous host has prompted researchers and clinicians to broaden the spectrum of dendritic cell vaccines to hematological malignancies. Recently, the focus is on acute myeloid leukemia and chronic lymphocytic leukemia. This review summarizes data on the administration of autologous and allogeneic dendritic cells to leukemia patients as an interesting approach in cellular therapy of leukemias.

Dendritic cells in myelodysplastic syndromes: from pathogenesis to immunotherapy

Myelodysplastic syndromes (MDS) are clonal disorders of the hematopoietic stem cell characterized by ineffective hematopoiesis leading to peripheral cytopenias. Different processes are involved in its pathogenesis, such as (epi)genetic alterations and immunological dysfunctions. The nature of immune dysregulation is markedly different between various MDS risk groups. In low-risk MDS, the immune system is in a proinflammatory state, whereas in high-risk disease, immunosuppressive features facilitate expansion of the dysplastic clone and can eventually lead to disease progression to acute myeloid leukemia. Various cell types contribute to dysregulation of immune responses in MDS. Dendritic cells (DCs) are important regulators of immunity. However, the role of DCs in MDS has yet to be elucidated. It has been suggested that impaired DC function can hamper adequate immune responses. This review focuses on the involvement of DCs in immune dysregulation in low- and high-risk MDS and the implications for DC-targeted therapies.

Combined immunophenotyping and fluorescence in situ hybridization with chromosome-specific DNA probes allows quantification and differentiation of ex vivo generated dendritic cells, leukemia-derived dendritic cells and clonal leukemic cells in patients with acute myeloid leukemia

Antileukemic T-cell responses induced by leukemia-derived dendritic cells (DC(leu)) are variable, due to varying DC/DC(leu) composition/quality. We studied DC/DC(leu) composition/quality after blast culture in four DC media by flow cytometry (FC) and combined fluorescence in situ hybridization/immunophenotyping analysis (FISH-IPA). Both methods showed that DC methods produce variable proportions of DC subtypes. FISH-IPA is an elaborate method to study clonal aberrations in blast/DC cells on slides, however without preselection of distinct cell populations for FISH analysis. FISH-IPA data proved previous FC data: not every clonal/blast cell is converted to DC(leu) (resulting in various proportions of DC(leu)) and not every detectable DC is of clonal/leukemic origin. Preselection of the best of four DC methods for "best" DC/DC(leu) generation is necessary. DC(leu) proportions correlate with the antileukemic functionality of DC/DC(leu)-stimulated T-cells, thereby proving the necessity of studying the quality of DC/DC(leu) after culture. FC is the superior method to quantify DC/DC(leu), since a blast phenotype is available in every given patient, even with low/no proportions of clonal aberrations, and can easily be used to study cellular compositions after DC culture.

Synergistic effect of Toll-like receptor 4 and 7/8 agonists is necessary to generate potent blast-derived dendritic cells in Acute Myeloid Leukemia

Leukemic cells from AML patients can be differentiated to dendritic cells (DCs). Such DCs have potential for immunotherapy of patients. Blasts from 15 AML patients were differentiated into DCs and matured by different TLR agonists. We could generate AML-DCs from 73% of patients mostly with M4 or M5 subtypes. The DC recoveries ranged from 28% to 50%. The results showed that concomitant use of TLR4 and TLR7/8 agonists induced proficient DCs. Therefore, a combination of TLR4 and 7/8 agonists can be considered as an appropriate maturation cocktail for AML-DC production in order to use in the immunotherapy of AML patients.

The characterization and role of leukemia cell-derived dendritic cells in immunotherapy for leukemic diseases

Usually, an effective anti-leukemia immune response cannot be initiated effectively in patients with leukemia. This is probably related to immunosuppression due to chemotherapy, down-regulation of major histocompatibility complex (MHC) II molecules, and the lack of co-stimulatory molecules on dendritic cells (DC). In light of this problem, some methods had been used to induce leukemia cells to differentiate into mature DCs, causing them to present leukemia-associated antigens and activating naïve T cells. Furthermore, leukemia-derived DCs could be modified with tumor antigens or tumor-associated antigens to provide a new approach to anti-leukemia therapy. Numerous studies have indicated factors related to the induction and functioning of leukemia-derived DCs and the activation of cytotoxic T-lymphocytes (CTLs). These include the amount of purified DCs, cytokine profiles appropriate for inducing leukemia-derived DCs, effective methods of activating CTLs, reasonable approaches to DC vaccines, and the standardization of their clinical use. Determining these factors could lead to more effective leukemia treatment and benefit both mankind and scientific development. What follows in a review of advances in and practices of inducing leukemia-derived DCs and the feasibility of their clinical use.

In vitro-induced response patterns of antileukemic T cells: characterization by spectratyping and immunophenotyping

Myeloid leukemic cells can be induced to differentiate into leukemia-derived dendritic cells (DCleu) regaining the stimulatory capacity of professional DCs while presenting the leukemic antigen repertoire. But so far, the induced antileukemic T-cell responses are variable both in specificity and in efficacy. In an attempt to elucidate the underlying causes of different T-cell response patterns, T-cell receptor (TR) Vβ chain rearrangements were correlated with the T cells corresponding immunophenotypic profile, as well as their proliferative response and cytolytic capacities. In three different settings, donor T cells, either human leukocyte antigen matched or mismatched (haploidentical), or autologous T cells were repeatedly stimulated with myeloid blasts or leukemia-derived DC/DCleus from the corresponding patients diseased from acute myeloid leukemia (AML). Although no significant differences in T-cell proliferation were observed, the T-cell-mediated cytolytic response pattern varied considerably and even caused blast proliferation in two cases. Spectratyping revealed a remarkable restriction (>75% of normal level) of the CD4+ or CD8+-TR repertoire of blast- or DC/DCleu-stimulated T cells. Although in absolute terms, DC/DCleu stimulation induced the highest grade of restriction in the CD8+ T-cell subset, the CD4+ T-cell compartment seemed to be relatively more affected. But most importantly, in vitro stimulation with DC/DCleu resulted into an identical TR restriction pattern (β chain) that could be identified in vivo in a patient sample 3 months after allo-SCT. Thus, in vitro tests combining functional flow cytometry with spectratyping might provide predictive information about T cellular response patterns in vivo.

Various ‘dendritic cell antigens’ are already expressed on uncultured blasts in acute myeloid leukemia and myelodysplastic syndromes

Aim and methods: Leukemia-derived dendritic cells (DCleu) potentially present the whole leukemic antigen repertoire. We studied antigen-expression profiles of blasts/dendritic cells (DCs) generated from 137 acute myeloid leukemia (AML)/49 myelodysplastic syndromes (MDS) patients with six different DC-generating media by flow-cytometry combining expression of blast/maturation and DC antigens (DCA:CD1a,b,c, CD25, CD40, CD80, CD83, CD86, CD137-L and CD206). Results: First, DCA are regularly and variably expressed on uncultured blasts/mononuclear cells (MNCs). Individual patients’ DCA profiles must be evaluated before DC-culture to find suitable DCA to estimate quality/quantity of DC after culture. Second, after culture in every patient, at least one marker fulfilled these criteria. Third, different DC-generating methods showed varying efficiency to generate DC: not every method was always successful. Fourth, individual FACS-DCA profiles showed a successful DC/DCleu generation with at least one of three previously tested methods in every given AML/MDS case. Fifth, pooling results of all selected best methods in every given case, 28/30% DC were generated from AML/MDS samples: >60% viable DC, on average 49/56% mature DC and on average 36% of blasts were convertible to DCleu resulting in on average 49% DCleu of AML-DC. Conclusions: Individual DCA-expression profiles should be evaluated before culture to evaluate DC counts/subtypes (mature/viableDC, DCleu) in individual patients.

Immune alterations in untreated and treated myelodysplastic syndrome

INTRODUCTION

Current literature suggests a variety of immune abnormalities are present in myelodysplastic syndrome (MDS) patients. However, they have not been comprehensively characterized or systematized to date. As a result, their clinical implications remain largely unknown. In addition, an increased incidence of various autoimmune conditions has been documented in MDS patients.

AREAS COVERED

The authors offer a comprehensive review of the existing literature on immune mechanisms involved in the pathogenesis of MDS, various immune abnormalities documented in its course, their link with the clonal evolution of MDS as well as immune alterations induced by the existing MDS therapies.

EXPERT OPINION

The course of MDS is accompanied by complex immune alterations, including T-cell and NK-cell defects, decreased functional abilities of neutrophils and antigen-presenting cells, altered antibody and cytokine production. While contemporary MDS therapies are shown to possess some immunomodulatory properties, authentic autoimmune conditions have also been documented with lenalidomide and recombinant erythropoietin. Caution should be exerted with the use of these agents in MDS patients with evidence of autoimmune disorders, as exacerbation of autoimmune phenomena can be anticipated. While the heterogeneity of MDS represents an inherent limitation, integration of emerging information from molecular biology, genetics, immunology research and clinical practice could translate into improved outcomes of this disease spectrum.

Quality of T-cells after stimulation with leukemia-derived dendritic cells (DC) from patients with acute myeloid leukemia (AML) or myeloid dysplastic syndrome (MDS) is predictive for their leukemia cytotoxic potential

Myeloid leukemic cells can differentiate into leukemia-derived dendritic cells (DC(leu)), presenting known/unknown leukemic-antigens. Induced anti-leukemic T-cell-responses are variable. To further elicit DC/DC(leu)-induced T-cell-response-patterns we performed (functional)flow-cytometry/fluorolysis-assays before/after mixed lymphocyte cultures (MLC) of matched (allogeneic) donor-T-cells (n=6), T-cells prepared at relapse after stem cell transplantation (n=4) or (autologous) patients'-T-cells (n=7) with blast-containing-mononuclear-cells ('MNC') or DC(leu)-containing DC ('DC'). Compared to 'MNC' 'DC' were better mediators of anti-leukaemic T-cell-activity, although not in every case effective. We could define cut-off proportions of mature DC, DC(leu), proliferating, CD4(+), CD8(+) and non-naive T-cells after 'MNC'- or 'DC'-stimulation, that were predictive for an anti-leukemic-activity of stimulated T-cells as well as a response to immunotherapy. Interestingly especially ratios >1 of CD4:CD8 or CD45RO:CD45RA T-cells were predictive for anti-leukemic function after DC-stimulation. In summary the composition and quality of DC and T-cells after a MLC-stimulating-phase is predictive for a successful ex-vivo and in-vivo anti-leukemic response, especially with respect to proportions of proliferating, CD4(+) and CD45RO(+) T-cells. Successful cytotoxicity and the development of a T-cell-memory after 'DC'-stimulation could be predictive for the clinical course of the disease and may pave the way to develop adoptive immunotherapy, especially for patients at relapse after SCT.

Dendritic cells (DCs) can be successfully generated from leukemic blasts in individual patients with AML or MDS: an evaluation of different methods

Myeloid-leukemic cells (AML, MDS, CML) can be differentiated to leukemia-derived dendritic cell [DC (DCleu)] potentially presenting the whole leukemic antigen repertoire without knowledge of distinct leukemia antigens and are regarded as promising candidates for a vaccination strategy. We studied the capability of 6 serum-free DC culture methods, chosen according to different mechanisms, to induce DC differentiation in 137 cases of AML and 52 cases of MDS. DC-stimulating substances were cytokines ("standard-medium", "MCM-Mimic", "cytokine-method"), bacterial lysates ("Picibanil"), double-stranded RNA ["Poly (I:C)"] or a cytokine bypass method ("Ca-ionophore"). The quality/quantity of DC generated was estimated by flow cytometry studying (co) expressions of "DC"antigens, costimulatory, maturation, and blast-antigens. Comparing these methods on average 15% to 32% DC, depending on methods used, could be obtained from blast-containing mononuclear cells (MNC) in AML/MDS cases with a DC viability of more than 60%. In all, 39% to 64% of these DC were mature; 31% to 52% of leukemic blasts could be converted to DCleu and DCleu-proportions in the suspension were 2% to 70% (13%). Average results of all culture methods tested were comparable, however not every given case of AML could be differentiated to DC with 1 selected method. However performing a pre-analysis with 3 DC-generating methods (MCM-Mimic, Picibanil, Ca-ionophore) we could generate DC in any given case. Functional analyses provided proof, that DC primed T cells to antileukemia-directed cytotoxic cells, although an anti-leukemic reaction was not achieved in every case. In summary our data show that a successful, quantitative DC/DCleu generation is possible with the best of 3 previously tested methods in any given case. Reasons for different functional behaviors of DC-primed T cells must be evaluated to design a practicable DC-based vaccination strategy.

Peptide vaccines for patients with acute myeloid leukemia

The majority of patients with acute myeloid leukemia (AML) under 60 years of age reach a complete hematological remission after intensive chemotherapy. However, only 20-40% of all patients with AML achieve a disease-free survival of more than 5 years. The graft-versus-leukemia effect observed after allogeneic stem cell transplantation and donor lymphocyte infusions strongly suggests that T lymphocytes play a major role in the rejection of leukemic cells. Vaccination with leukemia-associated antigen (LAA) peptides might constitute a way to augment the graft-versus-leukemia effect. Peptide vaccination causes no major side effects, which is of particular note as most AML patients are people over 60 years of age, often suffering from concomitant disease. This review summarizes approaches to define appropriate LAAs as targets of a T-cell-based vaccine immunotherapy. Current clinical LAA peptide vaccination protocols targeting Wilms' tumor gene, proteinase-3 and the receptor for hyaluronan-mediated motility are reviewed and an outlook to dendritic cells, adjuvants and short oligodenucleotides is given.

The role of soluble and cell-surface expressed 4-1BB ligand in patients with malignant hemopoietic disorders

The TNFR family member 4-1BB and its ligand 4-1BBL are involved in the costimulation of T-cells and tumor-derived soluble (s)4-1BBL may influence the interaction of malignant cells with the immune system. Here, we report that cell-surface-expressed (c)4-1BBL can be expressed on mononuclear blood cells from patients with acute myeloid leukemia (AML) (n = 35), myelodysplasia (n = 5) or non-Hodgkin lymphoma (n = 11) and can be coexpressed on varying proportions of lymphoid or myeloid malignant cells and on dendritic cells differentiated from AML-blasts. Direct correlations between c- and s4-1BBL were not found in the investigated cases. Up to now expression of 4-1BBL has not been described on primary myeloid malignant cells, but only on malignant cells of lymphoid or solid tumor origin or on tumor cell lines. With our work we further contribute to the understanding of the potential role of c/s4-1BBL in immune reactions and its influence on the interaction of tumor and immunoreactive cells.

Large-scale generation of autologous dendritic cells for immunotherapy in patients with acute myeloid leukemia

BACKGROUND

Mononuclear cells (MNCs) of severely impaired acute myeloid leukemia (AML) patients may be collected by leukapheresis for large-scale generation of dendritic cells (AML-DCs) under good manufacturing practice (GMP) conditions for adoptive immunotherapy.

STUDY DESIGN AND METHODS

In five end-stage AML patients, a leukapheresis procedure was performed with a cell separator (either COBE Spectra [Gambro BCT] or Amicus [Baxter]). For large-scale AML-DC generation, the MNCs of a single leukapheresis concentrate were isolated by density gradient and plated into a cell factory under GMP conditions. The AML-DCs were harvested on Day 8 of culture, and their viability, the mature morphology, and the phenotype were evaluated. The AML-DCs were injected subcutaneously into five AML patients up to four times at a biweekly interval.

RESULTS

All AML patients entered the leukapheresis procedure with a highly pathologic blood count. In a mean separation time of 198 +/- 33 minutes, a mean of 1.3 +/- 0.2-fold the total blood volume was processed with a white blood cell (WBC) yield of 9 x 10(9) to 70 x 10(9) per collection dependent on the precollection WBC count. After density gradient a mean of 2.2 x 10(9) +/- 0.3 x 10(9) MNCs were plated into a cell factory. This resulted in a mean viable and mature DC yield of 0.01 x 10(9) of MNCs.

CONCLUSION

The leukapheresis procedure is a feasible and safe procedure even in patients with hematologic malignancies and highly pathologic blood counts. Sufficient amounts of MNCs can be collected in leukopenic patients and the large-scale generation of AML-DCs in cell factories under GMP conditions yields in an adequate quantity of viable and mature AML-DCs.

Immature and mature monocyte-derived dendritic cells in myelodysplastic syndromes of subtypes refractory anemia or refractory anemia with ringed sideroblasts display an altered cytokine profile

Dendritic cells (DC) are pivotal for T cell-mediated immunity. We investigated the early and terminal maturation of monocyte-derived DC (MoDC) in myelodysplastic syndromes (FAB subtypes refractory anemia (MDS-RA) or refractory anemia with ringed sideroblasts (MDS-RARS)). Immature MoDC were obtained by culture of monocytes with GM-CSF and IL-4 for 8 days. To obtain mature MoDC, TNF-alpha was added during the final three culture days. T cell proliferation and T cell cytokine secretion in mixed lymphocyte reactions (MLR) unveiled a strong reduction of allostimulatory capacity of mature but also of immature MoDC from MDS patients. Immature MoDC from MDS patients exhibited an almost normal immunophenotype, but secreted substantially less IL-12 and more IL-10 in response to LPS/IFN-gamma than normal controls. Terminal addition of TNF-alpha to GM-CSF/IL-4 treated monocytes failed to extinguish cytokine production by MDS MoDC and failed to induce the expected membrane upregulation of costimulatory and other ligands as in normal controls. While our data provide further support for previous studies that have indicated an impaired differentiation of immature towards mature MoDC, they also clearly demonstrate a qualitatively and quantitatively altered cytokine secretion at the level of immature MoDC, which may in part explain the reduced allostimulatory capacity of these cells. These alterations may contribute to immune modulation of the clinical phenotype of marrow failure in MDS, and may have to be considered when designing DC-based immunotherapeutic strategies for MDS.

Dendritic cells and myeloid leukaemias: plasticity and commitment in cell differentiation

Dendritic cells (DCs) are key antigen-presenting cells (APCs), which link innate and adaptive immunity, ultimately activating antigen-specific T cells. This review examines the relationship between the acute and chronic myeloid leukaemias and cells with DC properties. DCs are non-dividing terminally differentiated cells, and ex vivo leukaemic cells or cell lines show little similarity to DCs. However, many leukaemias differentiate further in response to defined stimuli, and retain a degree of lineage plasticity. Therefore, several studies have explored the response of leukaemic cells to the in vitro regimens used to differentiate ex vivo primary DCs. Recent data suggest that the most 'dendritic-like' cells can be derived from more undifferentiated myeloid leukaemias, such as the myelomonocytic Mutz-3 cell line. These findings have important implications for understanding the developmental origins of DCs, for harnessing the APC properties of this class of tumour to stimulate the therapeutic anti-tumour immunity, and for developing useful models for the study of human DC physiology and pathology. There is a strong rationale for further exploration of this class of tumour and its relationship to the normal DC.

Cyclin B1 is commonly expressed in the cytoplasm of primary human acute myelogenous leukemia cells and serves as a leukemia-associated antigen associated with autoantibody response in a subset of patients

OBJECTIVES

Aberrant expression of cyclin B1, a cell cycle regulator, is related to prognosis in various human malignancies. Additionally, cytoplasmic expression of cyclin B1 in epithelial malignancies is associated with a specific T-cell response and presumably also a humoral immune response. We therefore investigated (i) whether a similar expression pattern could be detected in native human acute myelogenous leukemia (AML) cells and (ii) whether cyclin B1 specific antibodies could be detected in AML.

METHODS

AML cell expression of cyclin B1 was analyzed by flow cytometry and confocal microscopy. Humoral immune response in AML patient sera against cyclin B1 was analyzed by ELISA.

RESULTS

AML cell expression of cyclin B1 was detected for all 42 patients; but the percentage of cyclin B1 positive cells showed a wide variation between patients. Confocal microscopy demonstrated that 32/42 (76%) patient samples showed abnormal cytoplasmic expression. Furthermore, the cytoplasmic expression was maintained after 14 d of in vitro culture and differentiation of the AML cells towards a dendritic cell phenotype. Cyclin B1 specific serum antibodies could be detected for seven of 65 patients with untreated AML.

CONCLUSIONS

Our studies demonstrate that primary human AML cells show aberrant cytoplasmic expression of cyclin B1 for a majority of patients and a specific humoral immune response was also detected for a subset of patients with untreated leukemia.

Immunotherapy of myeloid leukaemia

The treatment of myeloid leukaemia has progressed in recent years with the advent of donor leukocyte infusions (DLI), haemopoietic stem cell transplants (HSCTs) and targeted therapies. However, relapse has a high associated morbidity rate and a method for removing diseased cells in first remission, when a minimal residual disease state is achieved and tumour load is low, has the potential to extend remission times and prevent relapse especially when used in combination with conventional treatments. Acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) are heterogeneous diseases which lack one common molecular target while chronic myeloid leukaemia (CML) patients have experienced prolonged remissions through the use of targeted therapies which remove BCR-ABL(+) cells effectively in early chronic phase. However, escape mutants have arisen and this therapy has little effectivity in the late chronic phase. Here we review the immune therapies which are close to or in clinical trials for the myeloid leukaemias and describe their potential advantages and disadvantages.

Acute lymphoblastic leukaemia cells express CCR7 but not higher amounts of IL-10 after CD40 ligation

OBJECTIVE

Production of cytokines that support T-cell activation and proliferation and migration to lymph nodes is one of the most important terms of cancer vaccine development. In previous studies we and others used CD40 ligation to obtain higher expression of co-stimulatory and adhesion molecules on leukaemic cells from children with acute lymphoblastic leukaemia (ALL). This time we assess the cytokine and chemokine gene expression profile in CD40-stimulated ALL cells.

MATERIAL AND METHODS

Malignant cells from 25 children with BCP-ALL were stimulated (or not) with huCD40LT and rIL-4 for 96 h. Eleven different molecule, cytokine and chemokine mRNAs levels (CCR7, IL-23, TGF-beta-IP, IFN-gamma, IL-10, CD1a, CD40, CD54, CD80, CD83, CD86) were determined using the real-time PCR technique with TaqMan chemistry using ready-to-use low-density arrays for gene expression by Applied Biosystems.

RESULTS

1) Increases in mRNA levels for CD40, CD54 and CD80 after CD40L and IL-4 stimulation were observed, 2) CCR7 mRNA expression was higher after CD40 ligation than before the culture (p = 0.002), 3) IL-10 mRNA expression was higher after the culture with medium than before the culture (p = 0.01).

CONCLUSIONS

The results show that leukaemia-derived dendritic cells obtained with CD40 ligation express CCR7 - chemokine is involved in migration to lymph nodes and does not produce higher amounts of IL-10, a potent immunosuppressive cytokine. Our preclinical findings could be used in the design of immunotherapy trials for the treatment of children with ALL.

Feasibility of clinical dendritic cell vaccination in acute myeloid leukemia

Dendritic cells (DC) are increasingly being utilized for anti-cancer therapy. Acute myeloid leukemia (AML) blasts are able to differentiate towards leukemia-derived DC enabling efficient presentation of known and unknown leukemic antigens. Advances in culture techniques and AML-DC characterization justify clinical application. However, clinical trials using AML-DC are hampered by patient inclusion criteria which allow selective entering of patients in second complete remission. Clinical relevant responses to DC-based immunotherapy are likely to only occur in non-end-stage patients. Application in early stage disease is mandatory to permit ultimate proof of clinical benefit of AML-DC vaccination strategy.

An immune edited tumour versus a tumour edited immune system: Prospects for immune therapy of acute myeloid leukaemia

Cell based therapies for acute myeloid leukaemia (AML) have made significant progress in the last decade benefiting the prognosis and survival of patients with this aggressive form of leukaemia. Due to advances in haematopoietic stem cell transplantation (HSCT) and particularly the advent of reduced intensity conditioning (RIC), the scope of transplantation has now extended to those patients previously ineligible due to age and health restrictions and has been associated with a decrease in transplant related mortality. The apparent graft versus leukaemia (GvL) effect observed following HSCT demonstrates the potential of the immune system to target and eradicate AML cells. Building on previously published pre-clinical studies by ourselves and others, we are now initiating a Phase I clinical study in which lentiviral vectors are used to genetically modify AML cells to express B7.1 (CD80) and IL-2. By combining allogeneic HSCT with immunisation, using the autologous AML cells expressing B7.1 and IL-2, we hope to stimulate immune eradication of residual AML cells in poor prognosis patients that have achieved donor chimerism. In this report we describe the background to cell therapy based approaches for AML, and discuss difficulties associated with the deployment of a chronically stimulated, hence exhausted/depleted immune system to eradicate tumour cells that have already escaped immune surveillance.