Feasibility, safety, and efficacy of early prophylactic donor lymphocyte infusion after T cell-depleted allogeneic stem cell transplantation in acute leukemia patients.

Prophylactic donor lymphocyte infusion (DLI) starting at 6 months after T cell-depleted allogeneic stem cell transplantation (TCD-alloSCT) can introduce a graft-versus-leukemia (GvL) effects with low risk of severe graft-versus-host-disease (GvHD). We established a policy to apply low-dose early DLI at 3 months after alloSCT to prevent early relapse. This study analyzes this strategy retrospectively. Of 220 consecutive acute leukemia patients undergoing TCD-alloSCT, 83 were prospectively classified to have a high relapse risk and 43 were scheduled for early DLI. 95% of these patients received freshly harvested DLI within 2 weeks of the planned date. In patients transplanted with reduced intensity conditioning and an unrelated donor, we found an increased cumulative incidence of GvHD between 3 and 6 months after TCD-alloSCT for patients receiving DLI at 3 months compared to patients who did not receive this DLI (0.42 (95%Confidence Interval (95% CI): 0.14-0.70) vs 0). Treatment success was defined as being alive without relapse or need for systemic immunosuppressive GvHD treatment. The five-year treatment success in patients with acute lymphatic leukemia was comparable between high- and non-high-risk disease (0.55 (95% CI: 0.42-0.74) and 0.59 (95% CI: 0.42-0.84)). It remained lower in high-risk acute myeloid leukemia (AML) (0.29 (95% CI: 0.18-0.46)) than in non-high-risk AML (0.47 (95% CI: 0.42-0.84)) due to an increased relapse rate despite early DLI.

T helper 2 response in allergic bronchopulmonary aspergillosis is not driven by specific Aspergillus antigens.

Allergic bronchopulmonary aspergillosis (ABPA) is characterized by an allergic immunological response to Aspergillus fumigatus. In this study, we investigated whether certain Aspergillus antigens are more allergenic than others, as was postulated previously. We stimulated peripheral blood mononuclear cells from patients with ABPA with the classically described A. fumigatus allergens Aspf1, Aspf2, Aspf3, and Aspf4, as well as two other Aspergillus antigens, Crf1 and Catalase1. Activated CD4+ T cells displayed a T helper 2 phenotype with the production of IL-4 in response to stimulation with several of these different antigens. Immune responses were not limited to the classically described A. fumigatus allergens. In healthy individuals, we demonstrated a similar recognition profile to the different antigens, but in contrast the activated CD4+ T cells exerted a T helper 1 phenotype and mainly produced IFN-γ after stimulation with A. fumigatus antigens. In conclusion, irrespective of the A. fumigatus antigen, the T-cell immune response in patients with ABPA is skewed to a T helper 2 cytokine secretion profile.

Multi-cistronic vector encoding optimized safety switch for adoptive therapy with T-cell receptor-modified T cells.

T-cell receptor (TCR) gene transfer is an attractive strategy to equip T cells with defined antigen-specific TCRs using short-term in vitro procedures to target both hematological malignancies and solid tumors. TCR gene transfer poses different safety issues that might warrant the inclusion of a suicide gene. High affinity TCRs may result in on-target toxicity, and off-target reactivity directed against healthy tissue can be observed due to mixed TCR dimers. Inclusion of a suicide gene as a safety switch may abrogate these unwanted toxicities. Human CD20 has been proposed as a nonimmunogenic suicide gene targeted by widely used clinical-grade anti-CD20 antibodies that can additionally function as a selection marker. However, transduction of T cells with a multi-cistronic vector encoding both TCR and CD20 resulted in poor coexpression. In this study, we demonstrated that codon optimization of TCR and CD20 resulted in profound coexpression of both the preferentially expressed antigen in melanoma (PRAME)-TCR and CD20, allowing selective as well as efficient elimination of these engineered T cells in vitro. These results demonstrate the great potential of codon optimized CD20 to be broadly used in clinical trials as a safety switch.

Tracking the progeny of adoptively transferred virus-specific T cells in patients posttransplant using TCR sequencing.

Adoptive cellular therapies with T cells are increasingly used to treat a variety of conditions. For instance, in a recent phase 1/2 trial, we prophylactically administered multivirus-specific T-cell products to protect recipients of T-cell-depleted allogeneic stem cell grafts against viral reactivation. To establish treatment efficacy, it is important to determine the fate of the individual transferred T-cell populations. However, it is difficult to unequivocally distinguish progeny of the transferred T-cell products from recipient- or stem cell graft-derived T cells that survived T-cell depletion during conditioning or stem cell graft manipulation. Using messenger RNA sequencing of the T-cell receptor ß-chains of the individual virus-specific T-cell populations within these T-cell products, we were able to track the multiple clonal virus-specific subpopulations in peripheral blood and distinguish recipient- and stem cell graft-derived virus-specific T cells from the progeny of the infused T-cell products. We observed in vivo expansion of virus-specific T cells that were exclusively derived from the T-cell products with similar kinetics as the expansion of virus-specific T cells that could also be detected before the T-cell product infusion. In addition, we demonstrated persistence of virus-specific T cells derived from the T-cell products in most patients who did not show viral reactivation. This study demonstrates that virus-specific T cells from prophylactically infused multiantigen-specific T-cell products can expand in response to antigen encounter in vivo and even persist in the absence of early viral reactivation.

HA-1H T-Cell Receptor Gene Transfer to Redirect Virus-Specific T Cells for Treatment of Hematological Malignancies After Allogeneic Stem Cell Transplantation: A Phase 1 Clinical Study.

Graft-vs.-leukemia (GVL) reactivity after HLA-matched allogeneic stem cell transplantation (alloSCT) is mainly mediated by donor T cells recognizing minor histocompatibility antigens (MiHA). If MiHA are targeted that are exclusively expressed on hematopoietic cells of recipient origin, selective GVL reactivity without severe graft-vs.-host-disease (GVHD) may occur. In this phase I study we explored HA-1H TCR gene transfer into T cells harvested from the HA-1H negative stem-cell donor to treat HA-1H positive HLA-A*02:01 positive patients with high-risk leukemia after alloSCT. HA-1H is a hematopoiesis-restricted MiHA presented in HLA-A*02:01. Since we previously demonstrated that donor-derived virus-specific T-cell infusions did not result in GVHD, we used donor-derived EBV and/or CMV-specific T-cells to be redirected by HA-1H TCR. EBV and/or CMV-specific T-cells were purified, retrovirally transduced with HA-1H TCR, and expanded. Validation experiments illustrated dual recognition of viral antigens and HA-1H by HA-1H TCR-engineered virus-specific T-cells. Release criteria included products containing more than 60% antigen-specific T-cells. Patients with high risk leukemia following T-cell depleted alloSCT in complete or partial remission were eligible. HA-1H TCR T-cells were infused 8 and 14 weeks after alloSCT without additional pre-conditioning chemotherapy. For 4/9 included patients no appropriate products could be made. Their donors were all CMV-negative, thereby restricting the production process to EBV-specific T-cells. For 5 patients a total of 10 products could be made meeting the release criteria containing 3-280 × 106 virus and/or HA-1H TCR T-cells. No infusion-related toxicity, delayed toxicity or GVHD occurred. One patient with relapsed AML at time of infusions died due to rapidly progressing disease. Four patients were in remission at time of infusion. Two patients died of infections during follow-up, not likely related to the infusion. Two patients are alive and well without GVHD. In 2 patients persistence of HA-1H TCR T-cells could be illustrated correlating with viral reactivation, but no overt in-vivo expansion of infused T-cells was observed. In conclusion, HA-1H TCR-redirected virus-specific T-cells could be made and safely infused in 5 patients with high-risk AML, but overall feasibility and efficacy was too low to warrant further clinical development using this strategy. New strategies will be explored using patient-derived donor T-cells isolated after transplantation transduced with HA-1H-specific TCR to be infused following immune conditioning.

Bone marrow central memory and memory stem T-cell exhaustion in AML patients relapsing after HSCT.

The major cause of death after allogeneic Hematopoietic Stem Cell Transplantation (HSCT) for acute myeloid leukemia (AML) is disease relapse. We investigated the expression of Inhibitory Receptors (IR; PD-1/CTLA-4/TIM-3/LAG-3/2B4/KLRG1/GITR) on T cells infiltrating the bone marrow (BM) of 32 AML patients relapsing (median 251 days) or maintaining complete remission (CR; median 1 year) after HSCT. A higher proportion of early-differentiated Memory Stem (TSCM) and Central Memory BM-T cells express multiple IR in relapsing patients than in CR patients. Exhausted BM-T cells at relapse display a restricted TCR repertoire, impaired effector functions and leukemia-reactive specificities. In 57 patients, early detection of severely exhausted (PD-1+Eomes+T-bet-) BM-TSCM predicts relapse. Accordingly, leukemia-specific T cells in patients prone to relapse display exhaustion markers, absent in patients maintaining long-term CR. These results highlight a wide, though reversible, immunological dysfunction in the BM of AML patients relapsing after HSCT and suggest new therapeutic opportunities for the disease.

T-cell receptor gene transfer for treatment of leukemia.

The therapeutic efficacy of donor lymphocyte infusions has been proven for patients with relapsed hematologic malignancies after allogeneic stem cell transplantation. The beneficial effect of donor lymphocytes, however, is often accompanied by graft-versus-host-disease (GvHD). Adoptive transfer of antigen (Ag)-specific T-cell lines may eradicate the relapsed hematological malignancy, and may separate the anti-leukemic effect from GvHD. The main drawback of adoptive therapy of defined T-cell populations is the difficulty in producing sufficient quantities of these Ag-specific T cells. In addition, the specificity of the infused T cells is difficult to control. As the T-cell receptor (TCR) solely determines the specificity of T cells, transfer of relevant TCR genes into appropriate T-cell populations may provide a potent therapeutic reagent. With this strategy, donor-derived T-cell populations would be equipped with a TCR of defined specificity in short-term in vitro procedures, and infusion of the redirected cells would result in T-cell reactivity against the defined Ag. In this review we discuss the current status of TCR gene transfer for the treatment of hematological malignancies.

Tissue Damage Caused by Myeloablative, but Not Non-Myeloablative, Conditioning before Allogeneic Stem Cell Transplantation Results in Dermal Macrophage Recruitment without Active T-Cell Interaction.

Introduction: Conditioning regimens preceding allogeneic stem cell transplantation (alloSCT) can cause tissue damage and acceleration of the development of graft-versus-host disease (GVHD). T-cell-depleted alloSCT with postponed donor lymphocyte infusion (DLI) may reduce GVHD, because tissue injury can be restored at the time of DLI. In this study, we investigated the presence of tissue injury and inflammation in skin during the period of hematologic recovery and immune reconstitution after alloSCT. Methods: Skin biopsies were immunohistochemically stained for HLA class II, CD1a, CD11c, CD40, CD54, CD68, CD86, CD206, CD3, and CD8. HLA class II-expressing cells were characterized as activated T-cells, antigen-presenting cells (APCs), or tissue repairing macrophages. In sex-mismatched patient and donor couples, origin of cells was determined by multiplex analysis combining XY-FISH and fluorescent immunohistochemistry. Results: No inflammatory environment due to pretransplant conditioning was detected at the time of alloSCT, irrespective of the conditioning regimen. An increase in HLA class II-positive macrophages and CD3 T-cells was observed 12-24 weeks after myeloablative alloSCT, but these macrophages did not show signs of interaction with the co-localized T-cells. In contrast, during GVHD, an increase in HLA class II-expressing cells coinciding with T-cell interaction was observed, resulting in an overt inflammatory reaction with the presence of activated APC, activated donor T-cells, and localized upregulation of HLA class II expression on epidermal cells. In the absence of GVHD, patient derived macrophages were gradually replaced by donor-derived macrophages although patient-derived macrophages were detectable even 24 weeks after alloSCT. Conclusion: Conditioning regimens cause tissue damage in the skin, but this does not result in a local increase of activated APC. In contrast to the inflamed situation in GVHD, when interaction takes place between activated APC and donor T-cells, the tissue damage caused by myeloablative alloSCT results in dermal recruitment of HLA class II-positive tissue repairing macrophages co-existing with increased numbers of patient- and donor-derived T-cells, but without signs of specific interaction and initiation of an immune response. Thus, the local skin damage caused by the conditioning regimen appears to be insufficient as single factor to provoke GVHD induction.

CMV seronegative donors: Effect on clinical severity of CMV infection and reconstitution of CMV-specific immunity.

BACKGROUND: Cytomegalovirus (CMV)-specific T-cells are crucial to prevent CMV disease. CMV seropositive recipients transplanted with stem cells from a CMV seronegative allogeneic donor (R+D-) may be at risk for CMV disease due to absence of donor CMV-specific memory T-cells in the graft. METHODS: We analyzed the duration of CMV reactivations and the incidence of CMV disease in R+D- and R+D+ patients after alemtuzumab-based T-cell depleted allogeneic stem cell transplantation (TCD alloSCT). To determine the presence of donor-derived primary CMV-specific T-cell responses we analyzed the origin of CMV-specific T-cells in R+D- patients. RESULTS: The duration of CMV reactivations (54 versus 38 days, respectively, p = 0.048) and the incidence of CMV disease (0.14 versus 0.02, p = 0.003 at 1 year after alloSCT) were higher in R+D- patients compared to R+D+ patients. In R+D- patients, CMV-specific CD4+ and CD8+ T-cells were mainly of recipient origin. However, in 53% of R+D- patients donor-derived CMV-specific T-cells were detected within the first year. CONCLUSIONS: In R+D- patients, immunity against CMV was predominantly mediated by recipient T-cells. Nevertheless, donor CMV serostatus significantly influenced the clinical severity of CMV reactivations indicating the role of CMV-specific memory T-cells transferred with the graft, despite the ultimate formation of primary donor-derived CMV-specific T-cell responses in R+D- patients.

Molecular persistence of chronic myeloid leukemia caused by donor T cells specific for lineage-restricted maturation antigens not recognizing immature progenitor-cells.

Although donor lymphocyte infusion (DLI) induces complete remissions in 70% of patients with relapsed chronic myeloid leukemia (CML) after allogeneic stem-cell transplantation (SCT), some patients are refractory to DLI by showing disease persistence. In a patient who received DLI for relapsed CML, we observed persisting molecular disease despite a hematological and cytogenetic remission in the absence of graft-versus-host disease (GVHD). To determine the nature of this immune response, we isolated leukemia-reactive donor T-cell clones from the bone marrow (BM) of the patient at the time of clinical response. Four different types of CD8+ HLA class I restricted T-cell clones were obtained that were cytotoxic against Ebstein-Barr virus-transformed B-cell lines (EBV-LCL) of the patient, but not the donor, indicating recognition of minor histocompatibility antigens (mHags). By using survival studies with CFSE labelled BM cells populations, a hematopoietic progenitor cell inhibition assay and direct morphological examination we showed that the T-cell clones recognized mature monocytic and myeloid cells, whereas immature BM progenitor cells were insufficiently lysed. This patient's refractoriness for DLI appears to be caused by inadequate lysis of progenitor cells by these cytotoxic T cells. These findings support the hypothesis that for eradication of CML a cytotoxic T-cell response against leukemic progenitor cells is essential.

An activating mutation of GNB1 is associated with resistance to tyrosine kinase inhibitors in ETV6-ABL1-positive leukemia.

Leukemias harboring the ETV6-ABL1 fusion represent a rare subset of hematological malignancies with unfavorable outcomes. The constitutively active chimeric Etv6-Abl1 tyrosine kinase can be specifically inhibited by tyrosine kinase inhibitors (TKIs). Although TKIs represent an important therapeutic tool, so far, the mechanism underlying the potential TKI resistance in ETV6-ABL1-positive malignancies has not been studied in detail. To address this issue, we established a TKI-resistant ETV6-ABL1-positive leukemic cell line through long-term exposure to imatinib. ETV6-ABL1-dependent mechanisms (including fusion gene/protein mutation, amplification, enhanced expression or phosphorylation) and increased TKI efflux were excluded as potential causes of resistance. We showed that TKI effectively inhibited the Etv6-Abl1 kinase activity in resistant cells, and using short hairpin RNA (shRNA)-mediated silencing, we confirmed that the resistant cells became independent from the ETV6-ABL1 oncogene. Through analysis of the genomic and proteomic profiles of resistant cells, we identified an acquired mutation in the GNB1 gene, K89M, as the most likely cause of the resistance. We showed that cells harboring mutated GNB1 were capable of restoring signaling through the phosphoinositide-3-kinase (PI3K)/Akt/mTOR and mitogen-activated protein kinase (MAPK) pathways, whose activation is inhibited by TKI. This alternative GNB1K89M-mediated pro-survival signaling rendered ETV6-ABL1-positive leukemic cells resistant to TKI therapy. The mechanism of TKI resistance is independent of the targeted chimeric kinase and thus is potentially relevant not only to ETV6-ABL1-positive leukemias but also to a wider spectrum of malignancies treated by kinase inhibitors.

Donor T-cell responses and disease progression patterns of multiple myeloma.

Donor T-cells transferred after allogeneic stem cell transplantation (alloSCT) can result in long-term disease control in myeloma by the graft-versus-myeloma (GvM) effect. However, T-cell therapy may show differential effectiveness against bone marrow (BM) infiltration and focal myeloma lesions resulting in different control and progression patterns. Outcomes of 43 myeloma patients who underwent T-cell-depleted alloSCT with scheduled donor lymphocyte infusion (DLI) were analyzed with respect to diffuse BM infiltration and focal progression. For comparison, 12 patients for whom a donor search was started but no alloSCT was performed, were analyzed. After DLI, complete disappearance of myeloma cells in BM occurred in 86% of evaluable patients. The probabilities of BM progression-free survival (PFS) at 2 years after start of donor search, alloSCT and DLI, were 17% (95% confidence interval 0-38%), 51% (36-66%), and 62% (44-80%) respectively. In contrast, the probabilities of focal PFS at 2 years after start of donor search, alloSCT and DLI, were 17% (0-38%), 30% (17-44%) and 28% (11-44%), respectively. Donor-derived T-cell responses effectively reduce BM infiltration, but not focal progression in myeloma, illustrating potent immunological responses in BM with only limited effect of T-cells on focal lesions.

A phase I/II minor histocompatibility antigen-loaded dendritic cell vaccination trial to safely improve the efficacy of donor lymphocyte infusions in myeloma.

Allogeneic stem cell transplantation (allo-SCT) with or without donor lymphocyte infusions (DLI) is the only curative option for several hematological malignancies. Unfortunately, allo-SCT is often associated with GvHD, and patients often relapse. We therefore aim to improve the graft-versus-tumor effect, without increasing the risk of GvHD, by targeting hematopoietic lineage-restricted and tumor-associated minor histocompatibility antigens using peptide-loaded dendritic cell (DC) vaccinations. In the present multicenter study, we report the feasibility, safety and efficacy of this concept. We treated nine multiple myeloma patients with persistent or relapsed disease after allo-SCT and a previous DLI, with donor monocyte-derived mHag-peptide-loaded DC vaccinations combined with a second DLI. Vaccinations were well tolerated and no occurrence of GvHD was observed. In five out of nine patients, we were able to show the induction of mHag-specific CD8+ T cells in peripheral blood. Five out of nine patients, of which four developed mHag-specific T cells, showed stable disease (SD) for 3.5-10 months. This study shows that mHag-based donor monocyte-derived DC vaccination combined with DLI is safe, feasible and capable of inducing objective mHag-specific T-cell responses. Future research should focus on further improvement of the vaccination strategy, toward translating the observed T-cell responses into robust clinical responses.

Similar potential to become activated and proliferate but differential kinetics and profiles of cytokine production of umbilical cord blood T cells and adult blood naive and memory T cells.

Low alloreactivity of umbilical cord blood (UCB) T-cells may explain diminished graft-versus-host-disease after UCB transplantation. We investigated whether UCB T-cells have an intrinsic lower capacity to become activated. T-cells from UCB or adult blood (AB) were stimulated with anti-CD3 and anti-CD28 antibodies. On days 1-3 after stimulation, T-cell activation was determined by CD25 expression, proliferation was measured, and kinetics of cell division were analyzed by staining with CFSE. UCB and AB T cells exhibited similar numbers of activated and proliferating cells, but the extent of activation was lower in UCB T-cells. Enzyme-linked immunospot analysis showed lower levels and slower kinetics of IL-2, IL-4, IL-10, and IFN-gamma secreting cells for UCB T-cells. Comparison of UCB T-cells with CD45RA+ naive or CD45RO+ memory T cells purified from AB showed relatively low numbers of IL-4 and IL-10 secreting T cells in CD45RA+ AB T-cells and UCB T-cells as compared with CD45RO+ AB T cells. Numbers of IL-2 or IFN-gamma secreting cells in adult CD45RA+ T-cells were lower than in CD45RO+ T-cells but higher than in UCB T-cells. Thus diminished reactivity of UCB T-cells was not caused by a lower capacity to become activated and proliferate but may be explained by a lower extent of activation in UCB T cells, the absence of memory T cells in UCB, and differences between naive T cells from UCB and AB.

Long-term follow-up of myeloablative allogeneic stem cell transplantation using Campath "in the bag" as T-cell depletion: the Leiden experience.

Graft-versus-host disease (GVHD) is a major cause of mortality and morbidity after allogeneic stem cell transplantation (alloSCT) but can be prevented by removing T-lymphocytes from the graft. Campath (anti-CD52) antibodies have been widely used in vivo for T-cell depletion following conventional and reduced intensity conditioning regimens. The use of Campath in vivo was associated with a significant reduction in GVHD but at the cost of impaired immune reconstitution. We evaluated the long-term outcome of 73 myeloablative allogeneic stem cell transplants with HLA-identical sibling donors using Campath "in the bag" as method of in vitro T-cell depletion. All patients engrafted and hematopoietic recovery was uneventful, resulting in a median of 99% donor chimerism at 3 months after alloSCT. Cytomegalovirus (CMV) reactivation occurred in 53% of the patients. No CMV disease was observed probably as a result of pre-emptive (val)ganciclovir treatment. The incidence of aGVHD was low (22% grade II). No grades III-IV aGVHD was observed and extensive chronic GVHD (cGVHD) occurred in 19% of the patients. The low incidence of GVHD and successful pre-emptive antiviral therapy resulted in low TRM of 8%. Sixteen patients died due to disease relapse after alloSCT, resulting in an overall survival of 48% at 5-years after alloSCT.

Minor histocompatibility antigen-specific T cells with multiple distinct specificities can be isolated by direct cloning of IFNgamma-secreting T cells from patients with relapsed leukemia responding to donor lymphocyte infusion.

Graft-vs-leukemia reactivity after donor lymphocyte infusion (DLI) can be mediated by donor T cells recognizing minor histocompatibility antigens (mHags) on recipient hematopoietic cells. To study the diversity of cells involved in this immune response, hematopoietic cell reactive T cells were directly clonally isolated from peripheral blood of patients entering complete remission after DLI. T cells were briefly stimulated with bone marrow cells from patients pretransplant, and IFNgamma-secreting T cells were directly clonally isolated, and expanded. Cytotoxic T-lymphocyte (CTL) clones from individual patients used multiple distinct HLA-restricting molecules and varied in reactivity against patient-derived normal and/or malignant hematopoietic cells. For each patient, CTL clones specific for known immunodominant mHags as well as distinct unknown mHags were found. Within individual patients, CTL clones using the same HLA-restricting element could show differential recognition patterns, indicating further diversity in mHag reactivity. CTL clones from individual patients exhibiting identical specificities could show oligoclonal origin. In conclusion, the direct cloning technique shows that the response to hematopoietic cells after DLI is directed against multiple distinct mHags, including but not limited to known immunodominant mHags, implying that immunotherapy with T cells against multiple mHag specificities may be more effective in eradicating malignant cells.

Effectivity of a strategy in elderly AML patients to reach allogeneic stem cell transplantation using intensive chemotherapy: Long-term survival is dependent on complete remission after first induction therapy.

Intensive chemotherapy followed by allogeneic stem cell transplantation (alloSCT) can cure AML. Most studies on alloSCT in elderly AML report results of highly selected patient cohorts. Hardly any data exist on the effectiveness of prospective strategies intended to bring as many patients as possible to transplant. Between 2006 and 2011 we implemented a treatment algorithm for all newly diagnosed AML patients aged 61-75 years, consisting of intensive chemotherapy cycles to induce complete remission, followed by alloSCT. 44 of 60 (73%) newly diagnosed elderly AML patients started with chemotherapy. By meticulously following our algorithm in almost all patients, we could induce complete remission (CR) in 66% of patients starting with chemotherapy, and transplant 32% of these patients in continuous CR. Main reasons for failure were early relapse (16%), early death (14%), primary refractory disease (9%), and patient or physician decision to stop treatment (16%). Patients in continuous CR after first induction benefit most with 36% long-term survival. Patients not in CR after first induction benefit less; although additional chemotherapy induces CR in 45% of these patients, only 23% are transplanted and no long-term survival is observed, mainly due to relapse. Long-term survival in the group of 44 patients is 9% (median 4.5 years after alloSCT). Considering that 27% of patients do not start with chemotherapy and 64% of patients starting with chemotherapy do not reach alloSCT, the reasons for failure presented here should be used as a guide to develop new treatment algorithms to improve long-term survival in elderly AML patients.

Microarray Gene Expression Analysis to Evaluate Cell Type Specific Expression of Targets Relevant for Immunotherapy of Hematological Malignancies.

Cellular immunotherapy has proven to be effective in the treatment of hematological cancers by donor lymphocyte infusion after allogeneic hematopoietic stem cell transplantation and more recently by targeted therapy with chimeric antigen or T-cell receptor-engineered T cells. However, dependent on the tissue distribution of the antigens that are targeted, anti-tumor responses can be accompanied by undesired side effects. Therefore, detailed tissue distribution analysis is essential to estimate potential efficacy and toxicity of candidate targets for immunotherapy of hematological malignancies. We performed microarray gene expression analysis of hematological malignancies of different origins, healthy hematopoietic cells and various non-hematopoietic cell types from organs that are often targeted in detrimental immune responses after allogeneic stem cell transplantation leading to graft-versus-host disease. Non-hematopoietic cells were also cultured in the presence of IFN-γ to analyze gene expression under inflammatory circumstances. Gene expression was investigated by Illumina HT12.0 microarrays and quality control analysis was performed to confirm the cell-type origin and exclude contamination of non-hematopoietic cell samples with peripheral blood cells. Microarray data were validated by quantitative RT-PCR showing strong correlations between both platforms. Detailed gene expression profiles were generated for various minor histocompatibility antigens and B-cell surface antigens to illustrate the value of the microarray dataset to estimate efficacy and toxicity of candidate targets for immunotherapy. In conclusion, our microarray database provides a relevant platform to analyze and select candidate antigens with hematopoietic (lineage)-restricted expression as potential targets for immunotherapy of hematological cancers.

High susceptibility of human leukemic cells to Fas-induced apoptosis is restricted to G1 phase of the cell cycle and can be increased by interferon treatment.

In this study, we analyzed the influence of cell cycle status manipulations of leukemic cells on Fas-mediated apoptosis using the GM-CSF-dependent human myeloid leukemia cell line AML-193 as a model. GM-CSF and long-term treatment with interferon-gamma (IFN-gamma) or interferon-alpha (IFN-alpha) were used to manipulate the cell cycle status. Control cells were GM-CSF deprived, nonproliferating cells. IFN-gamma or IFN-alpha treatment did not induce proliferation in control cells, but resulted in recruitment of cells from resting G(0) phase into activated G(1) phase. Using agonistic anti-Fas antibodies (FAS18), we demonstrated that this shift from G(0) to G(1) was accompanied by a 2.5-fold increase in Fas sensitivity. A similar increase in sensitivity to FAS18 could be obtained by induction of proliferation with GM-CSF. Quantitative FACS analysis of surviving cells after FAS18-induced apoptosis showed deletion of the G(1) compartment, but complete protection of resting G(0) cells. Cells in S or G(2)/M phase were relatively protected against Fas induction. In conclusion, sensitivity to Fas-mediated apoptosis was restricted to cells in G(1) phase of the cell cycle, and can be increased by treatment of cells with interferons. By this mechanism, interferon treatment may render leukemic cells more susceptible to lysis by T cells during immunotherapeutic interventions.