Generation of Leukaemia-Derived Dendritic Cells (DCleu) to Improve Anti-Leukaemic Activity in AML: Selection of the Most Efficient Response Modifier Combinations.

Dendritic cells (DC) and leukaemia derived DC (DCleu) are potent stimulators of anti-leukaemic activity in acute myeloid leukaemia (AML) and can be generated from mononuclear cells in vitro following standard DC/DCleu-generating protocols. With respect to future clinical applications though, DC/DCleu-generating protocols specifically designed for application in a whole-blood-(WB)-environment must be established. Therefore, we developed ten new DC/DCleu-generating protocols (kits; Kit-A/-C/-D/-E/-F/-G/-H/-I/-K/-M) for the generation of DC/DCleu from leukaemic WB, containing calcium-ionophore, granulocyte-macrophage-colony-stimulating-factor (GM-CSF), tumour-necrosis-factor-alpha, prostaglandin-E1 (PGE1), prostaglandin-E2 (PGE2) and/or picibanil (OK-432). All protocols were evaluated regarding their performance in generating DC/DCleu using refined classification and/or ranking systems; DC/DCleu were evaluated regarding their performance in stimulating anti-leukaemic activity using a cytotoxicity fluorolysis assay. Overall, we found the new kits capable to generate (mature) DC/DCleu from leukaemic WB. Through refined classification and ranking systems, we were able to select Kit-I (GM-CSF + OK-432), -K (GM-CSF + PGE2) and -M (GM-CSF + PGE1) as the most efficient kits in generating (mature) DC/DCleu, which are further competent to stimulate immunoreactive cells to show an improved anti-leukaemic cytotoxicity as well. This great performance of Kit-I, -K and -M in mediating DC/DCleu-based anti-leukaemic immunity in a WB-environment in vitro constitutes an important and directive step for translating DC/DCleu-based immunotherapy of AML into clinical application.

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.

Expression profiles of HMGB1 on B-CLL related leukocytes contribute to prediction of relapse.

BACKGROUND: The High Mobility Group Box 1 (HMGB1) is a nuclear protein that is frequently overexpressed in hematologic diseases and might be of relevance in immunogenic cancer control thus correlating with patients' (pts.) prognosis in diseases such as acute myeloid, acute lymphatic and chronic lymphocytic leukemia. MATERIALS AND METHODS: Expression profiles of blasts from AML (n = 21), ALL (n = 16) and of B-lymphocytes of CLL (n = 9) pts. were analyzed for surface expression of HMGB1 using flow cytometry. Expression was quantified and correlated with clinically and prognostically relevant markers. RESULTS: Expression profiling of HMGB1 in blasts of AML and ALL subtypes did not show differences between primary vs. secondary disease development and gender related differences. In ALL pts. however, age groups at initial diagnosis between ≥20 vs. <20 years were compared and showed significant differences (≥20 vs. <20 years; 89% vs. 49%, p  <0.05) with higher expression in higher age. In AML and CLL these differences were not visible. To evaluate the prognostic significance of HMGB1 expression, expression quantity was correlated with established and prognostic classification systems (in AML ELN, in ALL GMALL) and probability to relapse. No significant correlation was seen in these entities. However, when AML pts. were analyzed for remission rates after first anthracycline based induction therapy, in those who did not experience a complete remission significantly enhanced HMGB1 surface expression was seen (98 vs. 94%; p < 0.05; n = 20). Furthermore, for CLL it was shown that higher HMGB1 expression was found in pretreated patients with relapsed or/and refractory disease (1 vs. more relapses; 94 vs. 98%; p  <0.05; n = 9). CONCLUSION: HMGB1 is frequently expressed in hematologic malignancies. In this study it was shown that HMGB1 surface expression on AML blasts can be used as predictors for treatment response. In CLL it may be a marker for advanced disease. In order to implement this marker in FACS routine it could be a useful and practical tool for prognostic assessment and treatment planning.

WT1, PRAME, and PR3 mRNA Expression in Acute Myeloid Leukemia (AML).

Several tumor-associated antigens (TAAs) were recently identified, that could qualify as targets for immunotherapy, they could qualify (on RNA-level) for monitoring of tumor load. Here, we studied the expression levels of the immunogenic antigens PRAME (preferentially expressed antigen of melanoma), WT1 (Wilms' tumor gene), and PR3 (proteinase 3) on myeloid blasts by real-time quantitative polymerase chain reaction and correlated these data to the state and course of disease and to the defined subgroups of acute myeloid leukemia (AML). At first diagnoses, 41 of 47 patients tested showed overexpression of PRAME (87%), 38 of WT1 (81%), and 26 of PR3 (55%), with the highest expression levels for PRAME (2048-fold), followed by WT1 (486-fold) and PR3 (196-fold). Thereby, with 70%, the most frequent combination at first diagnoses was detected to be PRAME and WT1 (33/47 patients). Overall, 21 patients (45%) revealed overexpression for all 3 TAAs. Moreover, the highest expression levels of PRAME were found to be correlated with the FAB subtype M5, cytogenetic unfavorable risk groups, and AMLs arising from myelodysplasia (secondary AML; P=0.02). To compare TAA expression levels in the course of disease, expression data were calculatory adjusted to 100% blasts, revealing a relative increase in the PRAME expression levels during the course of persistent disease (3/4 cases). Independent of stage of disease, by trend, higher TAA expression levels were found on blasts derived from peripheral blood than those derived from the bone marrow. In conclusion, it is suggested that vaccine strategies for cancer immunotherapy should comprise different TAA peptides anticipating the diverse TAA expression levels on blasts evolving during the course of disease or treatment.

Role of Interferon (IFN)α in "Cocktails" for the Generation of (Leukemia-derived) Dendritic Cells (DCleu) From Blasts in Blood From Patients (pts) With Acute Myeloid Leukemia (AML) and the Induction of Antileukemic Reactions.

Strategies to stabilize remissions by specific elimination of residual acute myeloid leukemia (AML) blasts are needed. Leukemia-derived dendritic cell (DCleu/DC) generated from myeloid blasts improve antileukemic T-cell reactivity and install T-cell memory. Interferon (IFN)α-DC methods produce DCleu from chronic myeloid leukemia-patients (pts') blood. Various INFα-containing versus other DC methods were studied to produce DCleu (evaluated by flowcytometry) from AML-pts' blast-containing mononuclear (MNC) or whole blood (WB). After DCleu/DC stimulation in mixed lymphocyte cultures, T cells' potential to gain antileukemic cytotoxicity was studied and correlated with different DC methods and DCleu/DC counts. (1) Generation of DCleu/DC: (a) "IFN-GIT" [containing granulocyte macrophage-colony stimulating factor (GM-CSF)+IFNα+ tumor necrosis factor (TNF)-α] produced DC successfully (≥10% DC, ≥5% DCleu/cells) from AML-MNC (WB) in 54 (56%), "MCM-Mimic" in 76 (75%), "Picibanil" in 83 (64%), and "Calcium-ionophore" in 42 (67%) of cases. Proportions of DC subtypes in MNC (WB) were comparable with all DC methods, (b) IFNα combinations containing only GM-CSF+IFNα or only IFNα showed low efficiency to produce DCleu/DC from MNC (WB) compared with "IFN-GIT." (2) Antileukemic functionality: DCleu/DC-stimulated T cells showed improved leukemia cytotoxicity compared with blast cells or unstimulated T cells. The highest blast proliferation (=insufficient T cells) was seen with "IFN-GIT" DC-stimulated T cells. Probability to respond to immunotherapy or to obtain blast lysis of DC-stimulated T cells correlated with high proportions of DCleu/DC after DC culture, independent of DC-generating methods. (3) Cytokine release profiles: levels of interleukin-6, IFN-γ, and interleukin-2 were significantly lower in DC culture supernatants (from MNC/WB) with "IFN-GIT" compared with "MCM," "Pici," and "Ca" DC supernatants. Our data show that (1) WB culture simulates AML-pts' in vivo situation, (2) DC generation is possible from AML-MNC (WB) with IFNα-containing and other DC methods, (3) successful IFNα-DC generation needs GM-CSF+IFNα+TNF-α (IFN-GIT); however, "IFN-GIT" produces less DCleu/DC compared with other (non-IFNα) DC methods, (4) T cells stimulated with "IFN-GIT"-produced DCleu/DC yielded comparable antileukemic cytotoxicity; however, in cases without achieved blast lysis, an increased blast proliferation was observed.

Paramunity-inducing Factors (PINDs) in dendritic cell (DC) cultures lead to impaired antileukemic functionality of DC-stimulated T-cells.

INTRODUCTION: Paramunity-inducing-Factors (PINDs) consist of attenuated/inactivated viruses of various poxvirus-genera, used in veterinary medicine as non-antigen-specific, non-immunising stimulators of the innate immune system against infectious and malignant diseases. Their danger-signaling-interactions were tested for their capacity to improve leukemic antigen-presentation on DC generated from AML-patients' blasts ('DCleu') and DC-stimulation/activation of antileukemic T-cells. METHODS: We analyzed, whether the addition of PINDs during DC cultures (15 healthy, 22 leukemic donors) and mixed lymphocyte culture (MLC, n = 15) with autologous (n = 6), allogeneic (n = 2) or T-cells after stem cell transplantation (SCT; n = 7) would alter the quality and quantity of DC, the composition of T-cell-subsets, and/or their antileukemic functionality (AF) as studied by FACS and functional Fluorolysis-cytotoxicity-assays. RESULTS: Effects on 1. DC-cultures: PINDs in DC-cultures lead to increased proportions of mature DC and DCleu, but reduced proportions of viable and overall, as well as TLR4- and TLR9-expressing DC. 2. MLC: PINDs increased early (CD8+) T-cell activation (CD69+), but reduced proportions of effector-T-cells after MLC 3. AF: Presence of PINDs in DC- and MLC-cultures reduced T-cells' as well as innate cells' antileukemic functionality. 4. Cytokine-release profile: Supernatants from PIND-treated DC- and MLC-cultures resembled an inhibitory microenvironment, correlating with impaired blast lysis. CONCLUSIONS: Our data shows that addition of PINDs to DC-cultures and MLC result in a "blast-protective-capacity" leading to impaired AF, likely due to changes in the composition of T-/innate effector cells and the induction of an inhibitory microenvironment. PINDs might be promising in treating infectious diseases, but cannot be recommended for the treatment of AML-patients due to their inhibitory influence on antileukemic functionality.

Expression of 4-1BB and its ligand on blasts correlates with prognosis of patients with AML.

Costimulatory ligands (COLs) and their receptors (COR) regulate immune reactions and cellular survival and might be relevant in acute myeloid leukemia (AML). This study evaluated the clinical relevance of 4-1BBL, glucocorticoid-induced TNFR-related protein (GITR) and ligand (GITRL), CD80, and CD86 in case of expression on AML blasts. 98 patients were evaluated at initial diagnosis. Immunophenotypically evaluated specific fluorescence index (SFI) levels of COR and COL on blasts were correlated with morphological, cytogenetic, and several prognostic parameters. Significantly higher COR expression was seen in monocytic versus non-monocytic AML subtypes; GITR, p=0.05; GITRL, p=0.005; CD86, p=0.001). Cut-off values for two COR and their ligands were evaluated: cases presenting with 4-1BB values above cut-off 1.2 SFI levels correlated (tendentially) significantly with a higher probability for disease-free survival (DFS, p=0.06) and a favorable HR of 0.2; p=0.04 for relapse. HR for death was also significantly lower in this group (0.12; p=0.04). In contrast, a lower probability for DFS and overall survival was seen in cases with 4-1BBL expression above 2.2 SFI levels (p=0.08 and p=0.09). In addition, multivariate analysis showed a significantly higher probability of death in this group (HR 10.3, p=0.04). Expression of CD80 and CD86 did not show significant prognostic relevance. On initial diagnosis, 4-1BB and 4-1BBL qualify as markers for prediction of patients' course and represent a valuable screening target for patients with AML at initial diagnosis.

Expression of RANK-L and in part of PD-1 on blasts in patients with acute myeloid leukemia correlates with prognosis.

BACKGROUND: Co-stimulatory receptor (COR) and ligand (COL) expression on immune effectors are known to be relevant for immunological interactions and might be of prognostic relevance if expressed on acute myeloid leukemia (AML) blasts as reported for receptors of the tumor necrosis factor receptor family. AIM AND METHODS: Antigen expression profiling of COR (RANK, PD-1), COL (RANK-L, PD-1L), and HLA-ABC-antigens on blasts from 90 AML-patients at first diagnosis was performed by flow cytometry (SFI-Level characterization) and findings were correlated with clinical parameters. RESULTS: RANK expression was higher in immature compared to mature FAB groups (P = 0.08). As a monocytic marker, we identified HLA-ABC (P = 0.07). Prognostic analysis revealed a higher probability of overall survival in cases with lower RANK-L expression (<1.6 and ≥1.6, 15.6 vs. 12.2 months, P = 0.008, hazard ratio 0.36, P = 0.008). No significant impact of PD-1/L expression for patients'(pts) survival was seen but a correlation of PD-1 with a secondary AML (P = 0.03). Prolonged disease-free survival however correlated with higher PD-1 expression (≥1.1 vs. <1.1, 31.4 vs. 12.7 months; P = 0.03). CONCLUSION: Our study revealed that RANK-L is a promising marker to forecast pts' prognosis in AML. Immune checkpoint receptor PD-1/L as well as RANK and HLA-ABC did not show an impact on pts' survival.

Expression of surface-associated 82kDa-proMMP-9 in primary acute leukemia blast cells inversely correlates with patients' risk.

With its ability to degrade extracellular matrix proteins and activate growth factors and cytokines, matrix metalloproteinase (MMP)-9 is an important regulator of cell function. Previously, we reported that myeloid leukemic cells express a unique 82kDa-proMMP-9 variant on their cell surface that is not affected by its natural inhibitor. In this study, we generated monoclonal antibodies that specifically recognize 82kDa-proMMP-9. Flow cytometry analysis using these antibodies revealed significant surface expression of 82kDa-proMMP-9 in monocytes, but minimal amounts in T and B cells isolated from peripheral blood of nine healthy donors and 22 patients with acute myeloid leukemia (AML). In all AML patients, blasts expressed 82kDa-proMMP-9 at levels of 4%-46%, with significantly higher levels in patients with a better risk defined according to National Comprehensive Cancer Network (NCCN) guidelines (ρ = -0.748, p < 0.001) and favorable phenotype according to the French-American-British classification (p = 0.02) compared with patients with adverse prognoses. Receiver operating characteristic curve analysis confirmed the diagnostic accuracy of 82kDa-proMMP-9 measurement in AML blasts (area under the curve: 0.893 [0.739-1.000], p = 0.019). It led us to define a cutoff value of 11.5% for identifying patients with lower NCCN risk (p = 0.005) and with a tendency toward a higher probability of response to anthracycline-based therapy (p = 0.109) and increased event-free survival (p = 0.24). Thus, 82kDa-proMMP-9 expression on blasts may represent a novel independent marker of prognosis in patients with AML.

Death Receptor Expression on Blasts in AML Is Associated with Unfavorable Prognosis.

BACKGROUND: Tumor necrosis factor (TNF) receptor family members play a key role in the regulation of biological functions such as differentiation, proliferation and apoptosis of various cell types. MATERIALS AND METHODS: We studied co-expression profiles of death receptors from the TNF family [TNF-related apoptosis-inducing ligand receptor (TRAILR) 1 to 3, TNF receptor 1 (TNFR1) and FAS receptor (FAS)] on peripheral blood blasts from 46 patients with acute myeloid leukemia (AML) at first diagnosis by flow cytometry and correlated the obtained specific fluorescence indices (SFI) with morphological, cytogenetic and clinical parameters. RESULTS: We found that the expression of TRAILR2 and R3 was significantly increased in unfavorable risk groups, according to the National Comprehensive Cancer Network. Additionally, cut-off analyses for TRAILR2 and TNFR1 showed significantly shorter overall survival, earlier disease onset, higher proportions of cases with unfavorable prognosis and higher probability of relapse when SFIs were above the established cut-off. CONCLUSION: We demonstrate that high co-expression of death receptors on blasts is an independent predictor of poor prognosis in AML.

Cytokine Release Patterns in Mixed Lymphocyte Culture (MLC) of T-Cells with Dendritic Cells (DC) Generated from AML Blasts Contribute to Predict anti-Leukaemic T-Cell Reactions and Patients' Response to Immunotherapy.

To enlighten interactions between autologous, allogeneic or T-cells from patients after stem cell transplantation with leukaemia-derived-dendritic-cells containing dendritic cells or blast containing mononuclear cells (n = 21, respectively), we determined cytokine-concentrations (interleukin 2, 4, 6, 10, tumor-necrosis-factor-α, interferon-γ) in supernatants of mixed-lymphocyte-culture and in serum (n = 16) of 20 patients with acute myeloid leukaemia and three patients with myelodysplastic syndromes by cytometric-bead-assay. We correlated our data with lytic capabilities of stimulated T-cells in a fluorolysis-assay and clinical data: Dendritic-cell-/mononuclear-cell-stimulation of T-cells resulted in increased cytokine-levels in culture-medium compared to serum. There were no significant differences between cytokine-patterns of cases with/without lytic T-cell-activity, response to immunotherapy (stem cell transplantation/donor-lymphocyte-infusion) or graft-versus-host-disease. However, some predictive cytokine-cut-off-values for antileukaemic T-cell-activity, patients' response to immunotherapy and graft-versus-host-disease could be defined. Cytokine-profiles alone, without functional assays, are no useful tool to predict antileukaemic T-cell-function, although they can indicate lytic T-cell-activity, patients' response to immunotherapy and graft-versus-host-disease.

Profiles of activation, differentiation-markers, or ß-integrins on T cells contribute to predict T cells' antileukemic responses after stimulation with leukemia-derived dendritic cells.

Stem cell transplantations and donor lymphocyte infusions are promising immunotherapies to cure acute myeloid leukemia (AML). Leukemia-derived dendritic cells are known to improve antileukemic functionality of T cells. We evaluated the composition and development of distinct T-cell subtypes in AML patients (n=12) compared with healthy probands (n=5) before and during stimulation with leukemia-derived dendritic cells-containing DC (DC) or blast-containing mononuclear cells (MNC) in 0-7 days mixed lymphocyte cultures (MLC) by flow cytometry. AML patients' T-cell subgroups were correlated with antileukemic functionality before and after DC/MNC stimulation by functional fluorolysis assays. (1) Unstimulated T cells from AML patients presented with significantly lower proportions of activated, Tcm, CD137, and ß-integrin T cells, and significantly higher proportions of Tnaive and Teff compared with healthy probands. (2) After 7 days of DC or MNC stimulation, T-cell profiles were characterized by (significantly) increased proportions of activated T cells with effector function and significantly decreased proportions of ß-integrin T cells. (3) Antileukemic cytotoxicity was achieved in 40% of T cells after MNC stimulation compared with 64% after DC stimulation. Antileukemic activity after DC stimulation but not after MNC stimulation correlated with higher proportions of Tcm and Tnaive before stimulation, as well as with significantly higher proportions of activated and ß-integrin T cells. Furthermore, cutoff values for defined T-cell activation/differentiation markers and ß-integrin T cells could be defined, allowing a prediction of antileukemic reactivity. We could demonstrate the potential of the composition of unstimulated/DC-stimulated T cells for the lysis of AML blasts. Especially, AML patients with high numbers of Tnaive and Tcm could benefit from DC stimulation; proportions of activated and ß-integrin T cells correlated with increased antileukemic functionality and could serve to predict T cells' reactivity during stimulation. Refined analyses in the context of responses to immunotherapies are required.

CD4(+)and CD8(+)T-cell reactions against leukemia-associated- or minor-histocompatibility-antigens in AML-patients after allogeneic SCT.

T-cells play an important role in the remission-maintenance in AML-patients (pts) after SCT, however the role of LAA- (WT1, PR1, PRAME) or minor-histocompatibility (mHag, HA1) antigen-specific CD4(+) and CD8(+)T-cells is not defined. A LAA/HA1-peptide/protein stimulation, cloning and monitoring strategy for specific CD8(+)/CD4(+)T-cells in AML-pts after SCT is given. Our results show that (1) LAA-peptide-specific CD8+T-cells are detectable in every AML-pt after SCT. CD8(+)T-cells, recognizing two different antigens detectable in 5 of 7 cases correlate with long-lasting remissions. Clonal TCR-Vß-restriction exemplarily proven by spectratyping in PRAME-specific CD8(+)T-cells; high PRAME-peptide-reactivity was CD4(+)-associated, as shown by IFN-γ-release. (2) Two types of antigen-presenting cells (APCs) were tested for presentation of LAA/HA1-proteins to CD4(+)T-cells: miniEBV-transduced lymphoblastoid cells (B-cell-source) and CD4-depleted MNC (source for B-cell/monocyte/DC). We provide a refined cloning-system for proliferating, CD40L(+)CD4(+)T-cells after LAA/HA1-stimulation. CD4(+)T-cells produced cytokines (GM-CSF, IFN-γ) upon exposure to LAA/HA1-stimulation until after at least 7 restimulations and demonstrated cytotoxic activity against naive blasts, but not fibroblasts. Antileukemic activity of unstimulated, stimulated or cloned CD4(+)T-cells correlated with defined T-cell-subtypes and the clinical course of the disease. In conclusion we provide immunological tools to enrich and monitor LAA/HA1-CD4(+)- and CD8(+)T-cells in AML-pts after SCT and generate data with relevant prognostic value. We were able to demonstrate the presence of LAA-peptide-specific CD8(+)T-cell clones in AML-pts after SCT. In addition, we were also able to enrich specific antileukemic reactive CD4(+)T-cells without GvH-reactivity upon repeated LAA/HA1-protein stimulation and limiting dilution cloning.

Antileukemic T-cell responses can be predicted by the composition of specific regulatory T-cell subpopulations.

Regulatory T cells (Treg) are important regulators of immune responses. In acute myeloid leukemia (AML) patients before/after immunotherapy (stem cell transplantation or donor lymphocyte infusion), their suppressive role can contribute to suppress severe graft-versus-host reactions, but also to impair antileukemic reactions. As leukemia-derived dendritic cells (DCleu) are known to improve the antileukemic functionality of T cells, we evaluated the composition and development of distinct Treg subtypes in AML patients (n=12) compared with healthy probands (n=5) under unstimulated conditions and during stimulation with DCleu-containing DC (DC) or blast-containing mononuclear cells (MNC) in 0- to 7-day mixed lymphocyte cultures by flow cytometry. T-cell subgroups in AML patients were correlated with antileukemic functionality before and after DC or MNC stimulation by functional fluorolysis assays. (1) AML patients' T cells presented with significantly higher frequencies of Treg subgroups in unstimulated T cells compared with healthy probands. (2) After 7 days of DC or MNC stimulation, all Treg subtypes generally increased; significantly higher frequencies of Treg subtypes were still found in AML patients. (3) Antileukemic cytotoxicity was achieved in 36% of T cells after MNC compared with 64% after DC stimulation. Antileukemic activity after DC but not after MNC stimulation correlated with significantly lower frequencies of Treg subtypes (CD8Treg/Teff/em reg). Furthermore, cut-off values for Treg subpopulations could be defined, allowing a prediction of antileukemic response. We demonstrate a crucial role of special Treg subtypes in the mediation of antileukemic functionality. High CD8 Treg, Teff/em reg, and CD39 T cells correlated clearly with a reduced antileukemic activity of T cells. DC stimulation of T cells contributes to overcome impaired antileukemic T-cell reactivity. Refined analyses in the context of clinical responses to immunotherapies and graft versus host reactions are required.

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.

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) Vß 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 (ß 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.

Expression and prognostic value of FAS receptor/FAS ligand and TrailR1/TrailR2 in acute myeloid leukemia.

We studied the expressions of FR, FL, TR1, and TR2 on blasts and T cells from 71 patients with acute myeloid leukemia (AML) and correlated expression rates with the clinical course. Compared to AML-blasts we found higher co-expressions on healthy myeloid and T cells. Expression of all markers on blasts and on T cells was similar in different subtypes and acute stages of AML. Compared to the non-responders (n = 7) responders to the AML Cooperative Group-therapy (n = 22) presented with higher proportions of blasts co-expressing the four markers (FR: 32 vs 15%; FL: 15 vs 13%; TR1: 72 vs 37%; TR2: 24 vs 23%) or T cells (FR: 88 vs 71%; FL: 76 vs 56%; TR1: 96 vs 44%; TR2: 54 vs 42%). Patients with higher expression rates of TR1 on blasts (≥ 48%) and on T cells (≥ 67%) were characterized by a prolonged survival. In summary, our data show a variable expression of FR, FL, TR1 and TR2 on blasts or T cells in different subgroups of AML. Higher co-expression rates of FR, FL, TR1 and TR2 were characterized by a better prognosis for the patients with respect to achieve a remission and to survive. Functional analyses should be performed to find out those patients in who induced upregulation of these markers could contribute to overcome drug resistance.

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

AIM AND METHODS: Leukemia-derived dendritic cells (DC(leu)) 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/DC(leu) 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 DC(leu) resulting in on average 49% DC(leu) of AML-DC. CONCLUSIONS: Individual DCA-expression profiles should be evaluated before culture to evaluate DC counts/subtypes (mature/viableDC, DC(leu)) in individual patients.

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.

The quality and quantity of leukemia-derived dendritic cells from patients with acute myeloid leukemia and myelodysplastic syndrome are a predictive factor for the lytic potential of dendritic cells-primed leukemia-specific T cells.

Adoptive immunotherapy is an important therapy option to reduce relapse rates after stem-cell transplantation in patients suffering from acute myeloid leukemia and myelodysplastic syndromes. Myeloid leukemic cells can regularly be induced to differentiate into leukemia-derived dendritic cells (DC(leu)), regaining the stimulatory capacity of professional dendritic cells (DCs) while presenting the known/unknown leukemic antigen repertoire. So far, induced antileukemic T-cell responses are variable or even mediate opposite effects. To further elicit DC/DC(leu)-induced T-cell-response patterns, we generated DC from 17 Acute myeloid leukemia (AML) and 2 myelodysplastic syndrome cases and carried out flowcytometry and (functional) nonradioactive fluorolysis assays before/after mixed lymphocyte cultures 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) ("DC"). Compared with "MNC", "DC" were better mediators of antileukemic-activity, although not in every case effective. We could define DC subtypes and cut-off proportions of DC subtypes/qualities (mature DC/DC(leu)) after "DC" priming, which were predictive for an antileukemic activity of primed T cells and the clinical course of the disease after immunotherapy (allogeneic stem-cell transplantation/donor lymphocytes infusion/therapy). In summary, our data show that the composition and quality of DC after a mixed lymphocyte culture-priming phase is predictive for a successful ex vivo antileukemic response, especially with respect to proportions of mature and leukemia-derived DC. These data contribute not only to predict DC-mediated functions or the clinical course of the diseases but also to develop and refine DC-vaccination strategies that may pave the way to develop and modify adoptive immunotherapy, especially for patients at relapse after allogeneic stem-cell transplantation.