Graft-versus-leukemia reactions in allogeneic chimeras

Immune Reconstitution after Allogeneic Hematopoietic Stem Cell Transplantation

The timely reconstitution and regain of function of a donor-derived immune system is of utmost importance for the recovery and long-term survival of patients after allogeneic hematopoietic stem cell transplantation (HSCT). Of note, new developments such as umbilical cord blood or haploidentical grafts were associated with prolonged immunodeficiency due to delayed immune reconstitution, raising the need for better understanding and enhancing the process of immune reconstitution and finding strategies to further optimize these transplant procedures. Immune reconstitution post-HSCT occurs in several phases, innate immunity being the first to regain function. The slow T cell reconstitution is regarded as primarily responsible for deleterious infections with latent viruses or fungi, occurrence of graft-versus-host disease, and relapse. Here we aim to summarize the major steps of the adaptive immune reconstitution and will discuss the importance of immune balance in patients after HSCT.

Genetic barriers in transplantation medicine

The successful of transplantation is determined by the shared human leukocyte antigens (HLAs) and ABO blood group antigens between donor and recipient. In recent years, killer cell receptor [i.e., killer cell immunoglobulin-like receptor (KIR)] and major histocompatibility complex (MHC) class I chain-related gene molecule (i.e., MICA) were also reported as important determinants of transplant compatibility. At present, several different genotyping techniques (e.g., sequence specific primer and sequence based typing) can be used to characterize blood group, HLA, MICA and KIR and loci. These molecular techniques have several advantages because they do not depend on the availability of anti-sera, cellular expression and have greater specificity and accuracy compared with the antibody-antigen based typing. Nonetheless, these molecular techniques have limited capability to capture increasing number of markers which have been demonstrated to determine donor and recipient compatibility. It is now possible to genotype multiple markers and to the extent of a complete sequencing of the human genome using next generation sequencer (NGS). This high throughput genotyping platform has been tested for HLA, and it is expected that NGS will be used to simultaneously genotype a large number of clinically relevant transplantation genes in near future. This is not far from reality due to the bioinformatics support given by the immunogenetics community and the rigorous improvement in NGS methodology. In addition, new developments in immune tolerance based therapy, donor recruitment strategies and bioengineering are expected to provide significant advances in the field of transplantation medicine.

Lysosome-associated membrane glycoprotein 1 predicts fratricide amongst T cell receptor transgenic CD8+ T cells directed against tumor-associated antigens

AIM

Autologous as well as allogeneic CD8+ T cells transduced with tumor antigen specific T cell receptors (TCR) may cause significant tumor lysis upon adoptive transfer. Besides unpredictable life-threatening off-target effects, these TCRs may unexpectedly commit fratricide. We hypothesized lysosome-associated membrane glycoprotein 1 (LAMP1, CD107a) to be a marker for fratricide in TCR transgenic CD8+ T cells.

METHODS

We identified HLA-A*02:01/peptide-restricted T cells directed against ADRB3295. After TCR identification, we generated HLA-A*02:01/peptide restricted TCR transgenic T cells by retroviral transduction and tested T cell expansion rates as well as A*02:01/peptide recognition and ES killing in ELISpot and xCELLigence assays. Expansion arrest was analyzed via Annexin and CD107a staining. Results were compared to CHM1319-TCR transgenic T cells.

RESULTS

Beta-3-adrenergic receptor (ADRB3) as well as chondromodulin-1 (CHM1) are over-expressed in Ewing Sarcoma (ES) but not on T cells. TCR transgenic T cells demonstrated HLA-A*02:01/ADRB3295 mediated ES recognition and killing in ELISpot and xCELLigence assays. 24h after TCR transduction, CD107a expression correlated with low expansion rates due to apoptosis of ADRB3 specific T cells in contrast to CHM1 specific transgenic T cells. Amino-acid exchange scans clearly indicated the cross-reactive potential of HLA-A*02:01/ADRB3295- and HLA-A*02:01/CHM1319-TCR transgenic T cells. Comparison of peptide motive binding affinities revealed extended fratricide among ADRB3295 specific TCR transgenic T cells in contrast to CHM1319.

CONCLUSION

Amino-acid exchange scans alone predict TCR cross-reactivity with little specificity and thus require additional assessment of potentially cross-reactive HLA-A*02:01 binding candidates. CD107a positivity is a marker for fratricide of CD8+ TCR transgenic T cells.

Blinatumomab-induced donor T-cell activation for post-stem cell transplant-relapsed acute CD19-positive biphenotypic leukemia

Post-stem cell transplantation (SCT) relapsed acute lymphoblastic leukemia (ALL) has extremely poor prognosis with median survival of less than 1 year. Donor lymphocyte infusion, second transplantation, chemotherapy or cytokine treatment have been tried as a salvage regimen without significant clinical benefit. Recently, blinatumomab, a bispecific monoclonal antibody targeting CD3-expressing T cells and CD19-expressing B-cell lineage malignant cells demonstrated promising outcomes in relapsed/refractory ALL patients. Literature on blinatumomab use in biphenotypic ALL along with Philadelphia chromosome positive (Ph+) ALL is limited. We report a case of post-SCT relapsed CD19 expressing biphenotypic lymphoblastic leukemia patient who achieved complete remission after blinatumomab treatment and has lasting remission for 1 year.

Novel approaches for preventing acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (alloHSCT) offers potential curative treatment for a wide range of malignant and nonmalignant hematological disorders. However, its success may be limited by post-transplant acute graft-versus-host disease (aGVHD), a systemic syndrome in which donor's immune cells attack healthy tissues in the immunocompromised host. aGVHD is one of the main causes of morbidity and mortality after alloHSCT. Despite standard GVHD prophylaxis regimens, aGVHD still develops in approximately 40-60% of alloHSCT recipients.

AREAS COVERED

In this review, after a brief summary of current knowledge on the pathogenesis of aGVHD, the authors review the current combination of a calcineurin inhibitor with an antimetabolite with or without added anti-thymocyte globulin (ATG) and emerging strategies for GVHD prevention.

EXPERT OPINION

A new understanding of the involvement of cytokines, intracellular signaling pathways, epigenetics and immunoregulatory cells in GVHD pathogenesis will lead to new standards for aGVHD prophylaxis allowing better prevention of severe aGVHD without affecting graft-versus-tumor effects.

T-cell and natural killer cell therapies for hematologic malignancies after hematopoietic stem cell transplantation: enhancing the graft-versus-leukemia effect

Hematopoietic stem cell transplantation has revolutionized the treatment of hematologic malignancies, but infection, graft-versus-host disease and relapse are still important problems. Calcineurin inhibitors, T-cell depletion strategies, and immunomodulators have helped to prevent graft-versus-host disease, but have a negative impact on the graft-versus-leukemia effect. T cells and natural killer cells are both thought to be important in the graft-versus-leukemia effect, and both cell types are amenable to ex vivo manipulation and clinical manufacture, making them versatile immunotherapeutics. We provide an overview of these immunotherapeutic strategies following hematopoietic stem cell transplantation, with discussions centered on natural killer and T-cell biology. We discuss the contributions of each cell type to graft-versus-leukemia effects, as well as the current research directions in the field as related to adoptive cell therapy after hematopoietic stem cell transplantation.

Tolerance and efficacy of autologous or donor-derived T cells expressing CD19 chimeric antigen receptors in adult B-ALL with extramedullary leukemia

The engineering of T lymphocytes to express chimeric antigen receptors (CARs) aims to establish T cell-mediated tumor immunity rapidly. In this study, we conducted a pilot clinical trial of autologous or donor- derived T cells genetically modified to express a CAR targeting the B-cell antigen CD19 harboring 4-1BB and the CD3ζ moiety. All enrolled patients had relapsed or chemotherapy-refractory B-cell lineage acute lymphocytic leukemia (B-ALL). Of the nine patients, six had definite extramedullary involvement, and the rate of overall survival at 18 weeks was 56%. One of the two patients who received conditioning chemotherapy achieved a three-month durable complete response with partial regression of extramedullary lesions. Four of seven patients who did not receive conditioning chemotherapy achieved dramatic regression or a mixed response in the haematopoietic system and extramedullary tissues for two to nine months. Grade 2-3 graft-versus-host disease (GVHD) was observed in two patients who received substantial donor-derived anti-CD19 CART (chimeric antigen receptor-modified T) cells 3-4 weeks after cell infusions. These results show for the first time that donor-derived anti-CD19 CART cells can cause GVHD and regression of extramedullary B-ALL. This study is registered at www.clinicaltrials.gov as NCT01864889.

KIR alloreactivity based on the receptor-ligand model is associated with improved clinical outcomes of allogeneic hematopoietic stem cell transplantation: Result of single center prospective study

Receptors on natural killer (NK) cells, named killer immunoglobulin-like receptors (KIRs), recognize HLA class I alleles. Patients (n=59) who received allogeneic hematopoietic stem cell transplantation (HSCT) from either a related (n=17) or unrelated donor (n=42) in Samsung Medical Center (Seoul, South Korea) were included. KIR mismatch was defined as incompatibility between the donor KIR and recipient KIR ligand (receptor-ligand model), and all cases were classified into the two broad haplotypes of KIR A and B. Patients with acute leukemia (n=51, 86.4%) or myelodysplastic syndrome (n=8, 13.6%) were included. Peripheral blood was used as the source of stem cells in all patients. Kaplan-Meier survival curves for overall survival (OS), disease-free survival (DFS), and cumulative incidence of relapse (CIR) favored recipients with a KIR-mismatched donor, although the differences were not statistically significant. In multivariate analysis, KIR mismatch was an independent prognostic indicator of a better OS (P=0.010, HR=0.148, 95% CI 0.034-0.639), DFS (P=0.022, HR=0.237, 95% CI 0.069-0.815), and CIR (P=0.031, HR=0.117, 95% CI 0.017-0.823). OS, DFS, and CIR did not differ significantly between the KIR A and B haplotypes.

Novel immunotherapies for hematologic malignancies

The immune system is designed to discriminate between self and tumor tissue. Through genetic recombination, there is fundamentally no limit to the number of tumor antigens that immune cells can recognize. Yet, tumors use a variety of immunosuppressive mechanisms to evade immunity. Insight into how the immune system interacts with tumors is expanding rapidly and has accelerated the translation of immunotherapies into medical breakthroughs. Herein, we appraise novel strategies that exploit the patient's immune system to kill cancer. We review various forms of immune-based therapies, which have shown significant promise in patients with hematologic malignancies, including (i) conventional monoclonal therapies like rituximab; (ii) engineered monoclonal antibodies called bispecific T-cell engagers; (iii) monoclonal antibodies and pharmaceutical drugs that block inhibitory T-cell pathways (i.e. PD-1, CTLA-4, and IDO); and (iv) adoptive cell transfer therapy with T cells engineered to express chimeric antigen receptors or T-cell receptors. We also assess the idea of using these therapies in combination and conclude by suggesting multi-prong approaches to improve treatment outcomes and curative responses in patients.

Mechanism of tumor remission by cytomegalovirus in a murine lymphoma model: evidence for involvement of virally induced cellular interleukin-15

A murine model of B and T cell lymphomas in recipients after hematoablative conditioning for hematopoietic cell transplantation (HCT) has previously revealed a tumor-repressive, metastasis-inhibiting function of murine cytomegalovirus (mCMV). More recently, this prediction from the experimental model was put on trial in several clinical studies that indeed gave evidence for a lower incidence of tumor relapse associated with early reactivation of latent human cytomegalovirus (hCMV) after allogeneic HCT in patients treated against different types of hematopoietic malignancies, including lymphoma and acute as well as chronic leukemias. Due to the limitations inherent to clinical studies, the tumor-repressive role of hCMV remained observational with no approach to clarify mechanisms. Although the tumor-repressive mechanisms of mCMV and hCMV may differ and depend on the type of tumor, experimental approaches in the murine model might give valuable hints for concepts to follow in clinical research. We have previously shown for the liver-adapted A20-derived B cell lymphoma E12E that mCMV does not infect the lymphoma cells for causing cell death by viral cytopathogenicity but triggers tumor-selective apoptosis at a tissue site of tumor metastasis distant from a local site of infection. This finding suggested involvement of a cytokine that triggers apoptosis, directly or indirectly. Here we used a series of differential high-density microarray analyses to identify cellular genes whose expression is specifically upregulated at the site of virus entry only by viruses capable of triggering lymphoma cell apoptosis. This strategy identified interleukin-15 (IL-15) as most promising candidate, eventually confirmed by lymphoma repression with recombinant IL-15.

Donor Lymphocyte Infusions for Chronic Myeloid Leukemia Relapsing after Allogeneic Stem Cell Transplantation: May We Predict Graft-versus-Leukemia Without Graft-versus-Host Disease?

Donor lymphocyte infusions (DLI) are an effective treatment for relapsed chronic myeloid leukemia (CML) after allogeneic stem cell transplantation (alloSCT). Leukemia resistance and secondary graft-versus-host disease (GVHD) are major obstacles to success with DLI. The aim of this study was to identify pre-DLI factors associated with prolonged survival in remission without secondary GVHD. We retrospectively analyzed 500 patients treated with DLI for CML relapse (16% molecular, 30% cytogenetic, and 54% hematological) after alloSCT. The overall probabilities of failure- and secondary GVHD-free survival (FGFS) were 29% and 27% at 5 and 10 years after DLI, respectively. The type of relapse was the major factor influencing FGFS (40% for molecular and/or cytogenetic relapse and 20% for hematological relapse at 5 years, P < .001). Chronic GVHD before DLI and an interval <1 year between alloSCT and first DLI were independently associated with inferior FGFS in patients with molecular and/or cytogenetic relapse. Consequently, FGFS was 13%, 35%, to 56% at 5 years in patients with 2, 1, and 0 adverse features, respectively. In patients with hematological relapse, independent adverse prognostic factors for FGFS were initial dose of CD3(+) cells ≥ 50 × 10(6)/kg, donor-recipient sex mismatch, and chronic GVHD before DLI. FGFS was 0%, 17%, 33%, to 37% in patients with 3, 2, 1, and 0 adverse features, respectively. The probability of survival in remission without secondary GVHD was highest (>50% at 5 years) when DLI were given beyond 1 year from alloSCT for molecular and/or cytogenetic CML relapse that was not preceded by chronic GVHD.

Flow cytometric analysis of the graft-versus-Leukemia-effect after hematopoietic stem cell transplantation in mice

Acute Graft-versus-Host-Disease (aGvHD) is one of the major complications following allogeneic hematopoietic stem cell transplantation (HSCT). Although rather helpful, the use of conventional immunosuppressive drugs leads to general immunosuppression and is toxic. The effects of CD4(+) T-cells, in respect to the development of aGvHD, can be altered by administration of antihuman CD4 monoclonal antibodies, here MAX.16H5 IgG1 . This approach must be tested for possible interference with the Graft-versus-Leukemia-Effect (GvL). Thus, in vitro experiments were conducted, exposing P815 leukemic cells to bone marrow and splenocytes from cd4(-/-) -C57Bl/6 mice transgenic for human CD4 and HLA-DR3 (triple transgenic mice, [TTG]) as well as previously irradiated splenocytes from Balb/c(wt) mice. Using flow cytometry, the vitality of the various malignant and graft cells was analyzed over the course of 4 days. The survival rate of P815 cells did not change significantly when exposed to MAX.16H5 IgG1 , neither did the viability of the graft cells. This provides evidence that MAX.16H5 IgG1 does not impair the GvL effect in vitro. Additionally, P815-Balb/c(wt) leukemic mice were transplanted with P815(GFP) cells, bone marrow, and splenocytes from TTG mice with and without MAX.16H5 IgG1 . Without transplantation, P815(GFP) leukemic cells could be detected by flow cytometry in the liver, the bone marrow, and the spleen of recipients. The antibodies prevented aGvHD while leaving the GvL effect intact. These findings indicate no negative effect of MAX.16H5 IgG1 on the GvL effect in vitro and in vivo after HSCT in a murine model.

Treatment of High-Risk T-NHL with Stem Cell Transplantation: A Single Center Experience

Prognosis of peripheral and other advanced T cell lymphomas is poor. 20 patients with a median age of 46.4 (range 20.5-64.1) years were treated with autoSCT (n = 6) or alloSCT (n = 14) from 1996 to 2013. All patients were at high risk either due to the IPI-score or to the fact that SCT was part of a salvage therapy. Conditioning prior to alloSCT was myeloablative in seven cases (50 %). The patients were pretreated with 8.5 (median, range 2-38) cycles of chemotherapy. Ten patients are alive in CR after a median follow-up of 1.3 years (range 0.1-13.3). OS was 53 % after one and 40 % after 10 years. Best survival was reached after related alloSCT (80 % at 10 years) compared to other modalities. GvHD did not influence survival. AlloSCT from related donors can cure patients from T-cell lymphomas. Unrelated alloSCT or high-dose therapy and autoSCT are an option for patients without a familiar donor.

Safety and tolerability of allogeneic dendritic cell vaccination with induction of Wilms tumor 1-specific T cells in a pediatric donor and pediatric patient with relapsed leukemia: a case report and review of the literature

A 15-year-old girl with acute lymphoblastic leukemia received allogeneic dendritic cell vaccination, pulsed with Wilms tumor 1 (WT1) peptide, after her third hematopoietic stem cell transplantation (HSCT). The vaccines were generated from the third HSCT donor, who was her younger sister, age 12 years. The patient received 14 vaccines and had no graft-versus-host disease or systemic adverse effect, aside from grade 2 skin reaction at the injection site. WT1-specific immune responses were detected after vaccination by both WT1-tetramer analysis and enzyme-linked immunosorbent spot assay. This strategy may be safe, tolerable and even feasible for patients with a relapse after HSCT.

Impaired CD8(+) T cell immunity after allogeneic bone marrow transplantation leads to persistent and severe respiratory viral infection

RATIONALE

Bone marrow transplant (BMT) recipients experience frequent and severe respiratory viral infections (RVIs). However, the immunological mechanisms predisposing to RVIs are uncertain. Therefore, we hypothesized that antiviral T cell immunity is impaired as a consequence of allogeneic BMT, independent of pharmacologic immunosuppression, and is responsible for increased susceptibility to RVI.

METHODS

Bone marrow and splenocytes from C57BL/6(H2(b)) mice were transplanted into B10.BR(H2(k)) (Allo) or C57BL/6(H2(b)) (Syn) recipients. Five weeks after transplantation, recipient mice were inoculated intranasally with mouse parainfluenza virus type 1 (mPIV-1), commonly known as Sendai virus (SeV), and monitored for relevant immunological and disease endpoints.

MAIN RESULTS

Severe and persistent airway inflammation, epithelial injury, and enhanced mortality are found after viral infection in Allo mice but not in control Syn and non-transplanted mice. In addition, viral clearance is delayed in Allo mice as evidenced by prolonged detection of viral transcripts at Day 15 post-inoculation (p.i.) but not in control mice. In concert with these events, we also detected decreased levels of total and virus-specific CD8(+) T cells, as well as increased T cellexpression of inhibitory receptor programmed death-1 (PD-1), in the lungs of Allo mice at Day 8 p.i. Adoptive transfer of CD8(+) T cells from non-transplanted mice recovered from SeV infection into Allo mice at Day 8 p.i. restored normal levels of viral clearance, epithelial repair, and lung inflammation.

CONCLUSIONS

Taken together these results indicate that allogeneic BMT results in more severe RVI based on the failure to develop an appropriate pulmonary CD8(+) T cell response, providing an important potential mechanism to target in improving outcomes of RVI after BMT.

Current status of hematopoietic stem cell transplant in chronic myeloid leukemia

Indications for hematopoietic stem cell transplant (HSCT) in chronic myeloid leukemia (CML) have changed over time. This change has largely been influenced by the advent of tyrosine kinase inhibitors, increased understanding of the mechanisms underlying disease phase progression as well as drug resistance, refinement of transplant techniques and exploitation of graft versus leukemia effect in this disease. Here, we have discussed the status of HSCT in CML in the present era with regards to the current indications, factors determining outcome and management strategies for posttransplant relapse.

Loss of mismatched HLA in myeloid/NK cell precursor acute leukemia relapse after T cell-replete haploidentical hematopoietic stem cell transplantation

Myeloid/natural killer cell precursor acute leukemia (MNKL) is an aggressive disease with a high relapse rate even after allogeneic hematopoietic stem cell transplantation (SCT). We report a patient with MNKL who had a donor lymphocyte infusion (DLI) for relapse after T cell-replete human leukocyte antigen (HLA)-haploidentical SCT, but relapsed again 20 months later with loss of mismatched HLA. This case suggests that a strong graft-versus-leukemia effect of haploidentical SCT can be expected in MNKL patients. In the haploidentical setting, DLI should be considered for patients with relapsed leukemia whose leukemic cells have not lost HLA cell surface expression.

Harnessing the power of alloreactivity without triggering graft-versus-host disease: how non-engrafting alloreactive cellular therapy might change the landscape of acute myeloid leukemia treatment

Human leukocyte antigen-mismatched leukocyte infusions outside of the context of transplantation are a promising strategy for acute myeloid leukemia. Recent studies using such non-engrafting alloreactive cellular therapy (NEACT) revealed that survival of elderly patients increased from 10% to 39% when NEACT was given following chemotherapy, and that durable complete remissions were achieved in about a third of patients with relapsed or chemorefractory disease. We review the clinical reports of different NEACT approaches to date and describe how although T-cell and NK alloreactivity could generate immediate anti-leukemic effects, long-term disease control may be achieved by stimulating recipient-derived T-cell responses against tumor-associated antigens. Other variables likely impacting NEACT such as the release of pro-inflammatory cytokines from donor-host bidirectional alloreactivity and the choice of chemotherapeutics as well as future avenues for improving NEACT, such as optimizing the cell dose and potential synergies with adjuvant pharmacologic immune checkpoint blockade, are discussed.

Genetically engineered donor T cells to optimize graft-versus-tumor effects across MHC barriers

Hematopoietic stem cell transplantation has been used for more than 50 years to combat hematologic malignancies. In addition to being the first stem cell therapy, transplantation has provided evidence for the potent anti-tumor effects of T cells. Facilitating T-cell-based immunity against malignancies requires a careful balancing act between generating a robust response and avoiding off-target killing of healthy tissues, which is difficult to accomplish using bulk donor T cells. To address these issues, several approaches have been developed, drawing on basic T-cell biology, to potentiate graft-versus-tumor activity while avoiding graft-versus-host disease. Current strategies for anti-tumor cell therapies include: (i) selecting optimal T cells for transfer; (ii) engineering T cells to possess enhanced effector functions; and (iii) generating T-cell precursors that complete development after adoptive transfer. In this review, we assess the current state of the art in T-lineage cell therapy to treat malignancies in the context of allogeneic hematopoietic stem cell transplantation.

Association of severity of organ involvement with mortality and recurrent malignancy in patients with chronic graft-versus-host disease

The National Institutes of Health global score for chronic graft-versus-host disease was devised by experts but was not based on empirical data. We hypothesized that analysis of prospectively collected data would enable derivation of a more accurate model for estimating mortality risk. We analyzed 574 adult patients with chronic graft-versus-host disease enrolled in a multicenter, observational study, using multivariate time-varying analysis accounting for serial changes in severity of involvement of eight individual organ sites over time. In the training set, severity of skin, mouth, gastrointestinal tract, liver and lung involvement were independently associated with the risk of non-relapse mortality. Weighted mortality points were assigned to individual organs based on the hazard ratios and were summed. The population was divided into three risk groups based on the total mortality points. The three new risk groups were validated in an independent validation set, but did not show better discriminative performance than the National Institutes of Health global score. As compared to a moderate or mild global score, a severe global score was associated with increased risks of non-relapse and overall mortality across time but not with a decreased risk of recurrent malignancy. The National Institutes of Health global score predicts patients' mortality risk throughout the course of their chronic graft-versus-host disease. Further research is required in order to improve outcomes in patients with severe chronic graft-versus-host disease, since their risk of mortality remains elevated.

Allogeneic stem cell transplantation in patients above 55: suggestion for a further stratification of the HCT-CI

INTRODUCTION

Allogeneic stem cell transplantation (alloSCT) has become available for elderly patients or for patients with comorbidities by introduction of reduced-intense conditioning. Comorbidity-related prognosis after alloSCT can be estimated by the hematopoietic cell transplantation comorbidity index (HCT-CI).

MATERIAL AND METHODS

The charts from 85 patients who have undergone 90 alloSCTs between 1999 and 2011 were analysed. Most patients received a dose-reduced conditioning and a graft from an unrelated donor. Patients were stratified for age, HCT-CI, cGvHD versus no cGvHD, and a modified HCT-CI with a further split high-risk score.

RESULTS

Age over 60 years did not affect the outcome. Manifestation of cGvHD improved the prognosis significantly. An additional stratification of the high-risk group of the HCT-CI revealed that even a fraction of these patients can have considerable benefit from an alloSCT. Furthermore, this high-risk collective could be clearly discriminated into two groups with different outcomes.

CONCLUSIONS

The investigation confirms that age is no absolute risk factor for alloSCT and demonstrates the heterogeneity of the high-risk group of the HCT-CI. A comprehensive investigation of an additional stratification is suggested. Furthermore, the authors encourage early withdrawal of immunosuppression, even in elderly patients and patients with comorbidities to permit graft-versus-leukaemia/lymphoma, since cGvHD is associated with a significantly better prognosis.

Dendritic Cell Therapy in an Allogeneic-Hematopoietic Cell Transplantation Setting: An Effective Strategy toward Better Disease Control?

Hematopoietic cell transplantation (HCT) is a last treatment resort and only potentially curative treatment option for several hematological malignancies resistant to chemotherapy. The induction of profound immune regulation after allogeneic HCT is imperative to prevent graft-versus-host reactions and, at the same time, allow protective immune responses against pathogens and against tumor cells. Dendritic cells (DCs) are highly specialized antigen-presenting cells that are essential in regulating this balance and are of major interest as a tool to modulate immune responses in the complex and challenging phase of immune reconstitution early after allo-HCT. This review focuses on the use of DC vaccination to prevent cancer relapses early after allo-HCT. It describes the role of host and donor-DCs, various vaccination strategies, different DC subsets, antigen loading, DC maturation/activation, and injection sites and dose. At last, clinical trials using DC vaccination post-allo-HCT and the future perspectives of DC vaccination in combination with other cancer immunotherapies are discussed.

Primary cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome): part II. Prognosis, management, and future directions

Both mycosis fungoides (MF) and Sézary syndrome (SS) have a chronic, relapsing course, with patients frequently undergoing multiple, consecutive therapies. Treatment is aimed at the clearance of skin disease, the minimization of recurrence, the prevention of disease progression, and the preservation of quality of life. Other important considerations are symptom severity, including pruritus and patient age/comorbidities. In general, for limited patch and plaque disease, patients have excellent prognosis on ≥1 topical formulations, including topical corticosteroids and nitrogen mustard, with widespread patch/plaque disease often requiring phototherapy. In refractory early stage MF, transformed MF, and folliculotropic MF, a combination of skin-directed therapy plus low-dose immunomodulators (eg, interferon or bexarotene) may be effective. Patients with advanced and erythrodermic MF/SS can have profound immunosuppression, with treatments targeting tumor cells aimed for immune reconstitution. Biologic agents or targeted therapies either alone or in combination--including immunomodulators and histone-deacetylase inhibitors--are tried first, with more immunosuppressive therapies, such as alemtuzumab or chemotherapy, being generally reserved for refractory or rapidly progressive disease or extensive lymph node and metastatic involvement. Recently, an increased understanding of the pathogenesis of MF and SS with identification of important molecular markers has led to the development of new targeted therapies that are currently being explored in clinical trials in advanced MF and SS.

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.

Donor-derived CD19-targeted T cells cause regression of malignancy persisting after allogeneic hematopoietic stem cell transplantation

New treatments are needed for B-cell malignancies persisting after allogeneic hematopoietic stem cell transplantation (alloHSCT). We conducted a clinical trial of allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) targeting the B-cell antigen CD19. T cells for genetic modification were obtained from each patient's alloHSCT donor. All patients had malignancy that persisted after alloHSCT and standard donor lymphocyte infusions (DLIs). Patients did not receive chemotherapy prior to the CAR T-cell infusions and were not lymphocyte depleted at the time of the infusions. The 10 treated patients received a single infusion of allogeneic anti-CD19-CAR T cells. Three patients had regressions of their malignancies. One patient with chronic lymphocytic leukemia (CLL) obtained an ongoing complete remission after treatment with allogeneic anti-CD19-CAR T cells, another CLL patient had tumor lysis syndrome as his leukemia dramatically regressed, and a patient with mantle cell lymphoma obtained an ongoing partial remission. None of the 10 patients developed graft-versus-host disease (GVHD). Toxicities included transient hypotension and fever. We detected cells containing the anti-CD19-CAR gene in the blood of 8 of 10 patients. These results show for the first time that donor-derived allogeneic anti-CD19-CAR T cells can cause regression of B-cell malignancies resistant to standard DLIs without causing GVHD.

Allogeneic stem cell transplantation for patients with advanced rhabdomyosarcoma: a retrospective assessment

BACKGROUND

Allogeneic haematopoietic stem cell transplantation (allo-SCT) may provide donor cytotoxic T cell-/NK cell-mediated disease control in patients with rhabdomyosarcoma (RMS). However, little is known about the prevalence of graft-vs-RMS effects and only a few case experiences have been reported.

METHODS

We evaluated allo-SCT outcomes of 30 European Group for Blood and Marrow Transplantation (EBMT)-registered patients with advanced RMS regarding toxicity, progression-free survival (PFS) and overall survival (OS) after allo-SCT. Twenty patients were conditioned with reduced intensity and ten with high-dose chemotherapy. Twenty-three patients were transplanted with HLA-matched and seven with HLA-mismatched grafts. Three patients additionally received donor lymphocyte infusions (DLIs). Median follow-up was 9 months.

RESULTS

Three-year OS was 20% (s.e.±8%) with a median survival time of 12 months. Cumulative risk of progression was 67% (s.e.±10%) and 11% (s.e.±6%) for death of complications. Thirteen patients developed acute graft-vs-host disease (GvHD) and five developed chronic GvHD. Eighteen patients died of disease and four of complications. Eight patients survived in complete remission (CR) (median: 44 months). No patients with residual disease before allo-SCT were converted to CR.

CONCLUSION

The use of allo-SCT in patients with advanced RMS is currently experimental. In a subset of patients, it may constitute a valuable approach for consolidating CR, but this needs to be validated in prospective trials.

Fludarabine and 2-Gy TBI is superior to 2 Gy TBI as conditioning for HLA-matched related hematopoietic cell transplantation: a phase III randomized trial

The risks and benefits of adding fludarabine to a 2-Gy total body irradiation (TBI) nonmyeloablative regimen are unknown. For this reason, we conducted a prospective randomized trial comparing 2-Gy TBI alone, or in combination with 90 mg/m(2) fludarabine (FLU/TBI), before transplantation of peripheral blood stem cells from HLA-matched related donors. Eighty-five patients with hematological malignancies were randomized to be conditioned with TBI alone (n = 44) or FLU/TBI (n = 41). All patients had initial engraftment. Two graft rejections were observed, both in the TBI group. Infection rates, nonrelapse mortality, and graft-versus-host disease (GVHD) were similar between groups. Three-year overall survival was lower in the TBI group (54% versus 65%; hazard ratio [HR], .57; P = .09), with higher incidences of relapse/progression (55% versus 40%; HR, .55; P = .06), relapse-related mortality (37% versus 28%; HR, .53; P = .09), and a lower progression-free survival (36% versus 53%; HR, .56; P = .05). Median donor T cell chimerism levels were significantly lower in the TBI group at days 28 (61% versus 90%; P < .0001) and 84 (68% versus 92%; P < .0001), as was NK cell chimerism on day 28 (75% versus 96%; P = .0005). In conclusion, this randomized trial demonstrates the importance of fludarabine in augmenting the graft-versus-tumor effect by ensuring prompt and durable high-level donor engraftment early after transplantation.

Children's Oncology Group's 2013 blueprint for research: non-Hodgkin lymphoma

Non-Hodgkin lymphomas account for approximately 7% of cancers diagnosed in patients less than 20 years of age, with approximately 800 cases diagnosed annually at COG institutions. With current therapies, cure rates range from 70% to over 90%, even for children with disseminated disease. However, two major challenges need to be overcome: (i) to optimize upfront treatment to prevent relapse since prognosis for patients with relapsed disease remains poor and (ii) minimize long-term side effects in survivors. Hence, the future initiatives for the treatment of pediatric NHL are to utilize novel targeted therapies to not only improve outcomes but to decrease bystander organ toxicities and late effects.

Promising role of reduced-toxicity hematopoietic stem cell transplantation (PART-I)

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potential curative option for many patients with hematological malignancies (HM). However, the high rate of transplantation-related mortality (TRM) restricted the use of standard myeloablative HSCT to a minority of young and fit patients. Over the past few years, it has become evident that the alloreactivity of the immunocompetent donor cells mediated anti-malignancy effects independent of the action of high dose chemoradiotherapy. The use of reduced intensity conditioning (RIC) regimens has allowed a graft-versus-malignancy (GvM) effect to be exploited in patients who were previously ineligible for HSCT on the grounds of age and comorbidity. Retrospective analysis showed that RIC has been associated with lower TRM but a higher relapse rate leading to similar intermediate term overall and progression-free survivals when compared to standard myeloablative HSCT. However, the long term antitumor effect of this approach is less well established. Prospective studies are ongoing to define which patients might most benefit from reduced toxicity stem cell transplant (RT-SCT) and which transplant protocols are suitable for the different types of HM. The advent of RT-SCT permits the delivery of a potentially curative GvM effect to the majority of patients with HM whose outcome with conventional chemotherapy would be dismal. Remaining challenges include development of effective strategies to reduce relapse rates by augmenting GvM effects without increasing toxicity.

Minor histocompatibility antigen UTY as target for graft-versus-leukemia and graft-versus-haematopoiesis in the canine model

Male patients with female-stem-cell donors have better prognosis compared to female-to-male combinations due to Y-encoded minor histocompatibility antigens recognized by female-alloimmune-effector lymphocytes in the context of a graft-versus-leukemia (GvL) effect. We provide data in a dog-model that the minor histocompatibility antigen UTY might be a promising target to further improve GvL-immune reactions after allogeneic-stem-cell transplantations. Female-canine-UTY-specific T cells (CTLs) were stimulated in vitro using autologous-DCs loaded with three HLA-A2-restricted-UTY-derived peptides (3-fold-expansion), and specific T cell responses were determined in 3/6 female dogs. CTLs specifically recognized/lysed autologous-female-peptide-loaded DCs, but not naïve-autologous-female DCs and monocytes. They mainly recognized bone-marrow (BM) and to a lower extent DCs, monocytes, PBMCs and B-cells from DLA-identical-male littermates and peptide-loaded T2-cells in an MHC-I-restricted manner. A UTY-/male-specific reactivity was also obtained in vivo after stimulation of a female dog with DLA-identical-male PBMCs. In summary, we demonstrated natural UTY processing and presentation in dogs. We showed that female-dog CTLs were specifically stimulated by HLA-A2-restricted-UTY peptides, thereby enabling recognition of DLA-identical-male cells, mainly BM cells. These observations suggest UTY as a promising candidate-antigen to improve GvL-reactions in the course of immunotherapy.

Generation of multi-leukemia antigen-specific T cells to enhance the graft-versus-leukemia effect after allogeneic stem cell transplant

Adoptive immunotherapy with ex vivo expanded T cells is a promising approach to prevent or treat leukemia. Myeloid leukemias express tumor-associated antigens (TAA) that induce antigen-specific cytotoxic T lymphocyte (CTL) responses in healthy individuals. We explored the feasibility of generating TAA-specific CTLs from stem cell donors of patients with myeloid leukemia to enhance the graft-versus-leukemia effect after stem cell transplantation. CTL lines were manufactured from peripheral blood of 10 healthy donors by stimulation with 15mer peptide libraries of five TAA (proteinase 3 (Pr3), preferentially expressed antigen in melanoma, Wilms tumor gene 1 (WT1), human neutrophil elastase (NE) and melanoma-associated antigen A3) known to be expressed in myeloid leukemias. All CTL lines responded to the mix of five TAA and were multi-specific as assessed by interferon-γ enzyme-linked immunospot. Although donors showed individual patterns of antigen recognition, all responded comparably to the TAAmix. Immunogenic peptides of WT1, Pr3 or NE could be identified by epitope mapping in all donor CTL lines. In vitro experiments showed recognition of partially human leukocyte antigen (HLA)-matched myeloid leukemia blasts. These findings support the development of a single clinical grade multi-tumor antigen-specific T-cell product from the stem cell source, capable of broad reactivity against myeloid malignancies for use in donor-recipient pairs without limitation to a certain HLA-type.

Transferred WT1-reactive CD8+ T cells can mediate antileukemic activity and persist in post-transplant patients

Relapse remains a leading cause of death after allogeneic hematopoietic cell transplantation (HCT) for patients with high-risk leukemias. The potentially beneficial donor T cell-mediated graft-versus-leukemia (GVL) effect is often mitigated by concurrent graft-versus-host disease (GVHD). Providing T cells that can selectively target Wilms tumor antigen 1 (WT1), a transcription factor overexpressed in leukemias that contributes to the malignant phenotype, represents an opportunity to promote antileukemic activity without inducing GVHD. HLA-A*0201-restricted WT1-specific donor-derived CD8 cytotoxic T cell (CTL) clones were administered after HCT to 11 relapsed or high-risk leukemia patients without evidence of on-target toxicity. The last four treated patients received CTL clones generated with exposure to interleukin-21 (IL-21) to prolong in vivo CTL survival, because IL-21 can limit terminal differentiation of antigen-specific T cells generated in vitro. Transferred cells exhibited direct evidence of antileukemic activity in two patients: a transient response in one patient with advanced progressive disease and the induction of a prolonged remission in a patient with minimal residual disease (MRD). Additionally, three treated patients at high risk for relapse after HCT survive without leukemia relapse, GVHD, or additional antileukemic treatment. CTLs generated in the presence of IL-21, which were transferred in these latter three patients and the patient with MRD, all remained detectable long-term and maintained or acquired in vivo phenotypic and functional characteristics associated with long-lived memory CD8 T cells. This study supports expanding efforts to immunologically target WT1 and provides insights into the requirements necessary to establish potent persistent T cell responses.

Autologous stem cell transplant recipients tolerate haploidentical related-donor natural killer cell-enriched infusions

BACKGROUND

In the setting of allogeneic stem cell transplantation (SCT), infusing natural killer (NK) cells from a major histocompatibility complex (MHC)-mismatched donor can mediate an antileukemic effect. The graft-versus-tumor effect after autologous stem cell transplantation (ASCT) may result in less disease relapse.

STUDY DESIGN AND METHODS

We performed a Phase I clinical trial to assess the safety and feasibility of infusing distantly processed donor NK-enriched mononuclear cell (NK-MNC) infusions from a MHC haplotype-mismatched (haploidentical) donor to patients who recently underwent ASCT for a hematologic malignancy. On Day 1, peripheral blood MNCs were obtained by steady-state leukapheresis and sent from Boston to the Production Assistance for Cellular Therapies (PACT) facility at the University of Minnesota, where immunomagnetic depletion of CD3 cells was performed on Day 2. NK-MNC products were then returned to Boston on Day 2 for infusion on Day 3. Toxicity, cellular product characteristics, and logistic events were monitored.

RESULTS

At a median of 90 days (range, 49-191 days) after ASCT, 13 patients were treated with escalating doses of NK-MNCs per kilogram from 10(5) to 2 × 10(7) . Adverse effects included Grade 2 rigors and muscle aches, but no Grade 3 or 4 events and no graft-versus-host disease or marrow suppression. One air courier delay occurred. NK-MNC products were viable with cytotoxic activity after transport.

CONCLUSION

CD3-depleted, MHC-mismatched allogeneic NK-MNC infusions can be safely and feasibly administered to patients after ASCT after distant processing and transport, justifying further development of this approach.

New insights into antigen specific immunotherapy for chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a stem cell disease in which BCR/ABL plays an important role as an oncoprotein and a molecular and immunogenic target. Despite the success of targeted therapy using tyrosine kinase inhibitors (TKIs), CML remains largely incurable, most likely due to the treatment resistance of leukemic stem cells. Several immunotherapies have been developed for CML in different stages and relapse after allogeneic stem cell transplantation. In the this review, several specific immunotherapeutic approaches for CML, including vaccination and adoptive cellular immunotherapy, are discussed along with results from clinical trials, and the value of such immunotherapies in the era of imatinib and leukemia-associated antigens (LAAs), which are capable of inducing specific T cell responses and are appropriate target structures for the immunological targeting of CML cells, are also summarized.

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.

A TLR5 agonist enhances CD8(+) T cell-mediated graft-versus-tumor effect without exacerbating graft-versus-host disease

Allogeneic hematopoietic cell transplantation is an established treatment for hematologic and nonhematologic malignancies. Donor-derived immune cells can identify and attack host tumor cells, producing a graft-versus-tumor (GVT) effect that is crucial to the effectiveness of the transplantation therapy. CBLB502 is a novel agonist for TLR5 derived from Salmonella flagellin. On the basis of TLR5-mediated immunomodulatory function, we examined the effect of CBLB502 on GVT activity. Using two tumor models that do not express TLR5, and thereby do not directly respond to CBLB502, we found that CBLB502 treatment significantly enhanced allogeneic CD8(+) T cell-mediated GVT activity, which was evidenced by decreased tumor burden and improved host survival. Importantly, histopathologic analyses showed that CBLB502 treatment did not exacerbate the moderate graft-versus-host disease condition caused by the allogeneic CD8(+) T cells. Moreover, mechanistic analyses showed that CBLB502 stimulates CD8(+) T cell proliferation and enhances their tumor killing activity mainly indirectly through a mechanism that involves the IL-12 signaling pathway and the CD11c(+) and CD11b(+) populations in the bone marrow cells. This study demonstrates a new beneficial effect of CBLB502, and suggests that TLR5-mediated immune modulation may be a promising approach to improve GVT immunity without exacerbating graft-versus-host disease.

Reduced efficacy of mesenchymal stromal cells in preventing graft-versus-host disease in an in vivo model of haploidentical bone marrow transplant with leukemia

Mesenchymal stromal cell (MSC) immunosuppressive properties have been applied to treat graft-versus-host disease (GVHD) in allogeneic hematopoietic stem cell transplants (HSCTs). We have previously demonstrated that MSC infusions early after haplo-HSCT prevent GVHD in a haploidentical-HSCT mouse model. Now, we investigated the impact that MSCs' immunosuppressive properties have on the graft-versus-leukemia (GVL) effect. First, to mimic a chronic myeloid leukemia (CML) relapse after a haploidentical HSCT, lethally irradiated mice were coinfused with haploidentical donor bone marrow cells plus syngenic hematopoietic progenitors transduced with a retroviral vector encoding both the BCR/ABL oncogene and the ΔNGFR marker gene. As expected, a CML-like myeloproliferative syndrome developed in all the recipient animals. The addition of haploidentical splenocytes to the transplanted graft prevented CML development by a GVL effect, and all transplanted recipients died of GVHD. This GVL mouse model allowed us to investigate the impact of MSCs infused to prevent GVHD on days 0, 7, and 14 after HSCT, on the GVL effect, expecting an increase in leukemic relapse. Strikingly, a high mortality of the recipients was observed, caused by GVHD, and only few leukemic cells were detected in the recipient animals. In contrast, GVHD prevention by MSCs in the absence of BCR/ABL leukemic cells resulted in a significant survival of the recipients. In vitro data pointed to an inability of MSCs to control strong CTLs responses against BCR/ABL. Our results show that, although an evident increase in leukemic relapses induced by MSCs could not be detected, they showed a reduced efficacy in preventing GVHD that precluded us to draw clear conclusions on MSCs' impact over GVL effect.

Reduced-intensity conditioning versus standard conditioning before allogeneic haemopoietic cell transplantation in patients with acute myeloid leukaemia in first complete remission: a prospective, open-label randomised phase 3 trial

BACKGROUND

Reduced-intensity conditioning regimens have been developed to minimise early toxic effects and deaths after allogeneic haemopoietic cell transplantation. However, the efficacy of these regimens before this procedure has not been investigated in a randomised trial. In this prospective, open-label randomised phase 3 trial we compared a reduced-intensity fludarabine-based conditioning regimen with a standard regimen in patients with acute myeloid leukaemia in first complete remission.

METHODS

Patients were aged 18-60 years and had intermediate-risk or high-risk acute myeloid leukaemia (defined by cytogenetics) in first complete remission; an available HLA-matched sibling donor or an unrelated donor with at least nine of ten HLA alleles; and adequate renal, cardiac, pulmonary, and neurological function. Between Nov 15, 2004, and Dec 31, 2009, patients were randomly assigned (1:1, by a computer-based minimisation procedure that balanced patients for age, cytogenetic risk, induction therapy, and donor type) to receive either reduced-intensity conditioning of four doses of 2 Gy of total-body irradiation and 150 mg/m(2) fludarabine or standard conditioning of six doses of 2 Gy of total-body irradiation and 120 mg/kg cyclophosphamide. All patients were given ciclosporin and methotrexate as prophylaxis against graft-versus-host disease. Neither investigators nor patients were blinded to study treatment. Our primary endpoint was the incidence of non-relapse mortality, analysed in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT00150878.

FINDINGS

The trial was stopped early on Dec 31, 2009, because of slow accrual of patients. 99 patients were randomly assigned to receive reduced-intensity conditioning and 96 to receive standard conditioning. The incidence of non-relapse mortality did not differ between the reduced-intensity and standard conditioning groups (cumulative incidence at 3 years 13% [95% CI 6-21] vs 18% [10-26]; HR 0·62 [95% CI 0·30-1·31]). Relapse incidence (cumulative incidence 3 years 28% [95% CI 19-38] vs 26% [17-36]; HR 1·10 [95% CI 0·63-1·90]), disease-free survival (3 year disease-free survival 58% [95% CI 49-70] vs 56% [46-67]; HR 0·85 [95% CI 0·55-1·32]), and overall survival (3 year overall survival 61% [95% CI 50-74] vs 58% [47-70]; HR 0·77 [95% CI 0·48-1·25]) did not differ significantly between groups. Grade 3-4 of oral mucositis was less common in the reduced-intensity group than in the standard conditioning group (50 patients in the reduced-intensity conditioning group vs 73 patients in the standard conditioning group); the frequency of other side-effects such as graft-versus-host disease and increased concentrations of bilirubin and creatinine did not differ significantly between groups.

INTERPRETATION

Reduced-intensity conditioning results in a similar incidence of non-relapse mortality and reduced toxic effects compared with standard conditioning without affecting survival outcomes, and thus could be preferentially used in patients younger than 60 years with acute myeloid leukaemia transplanted in first complete remission.

BCR-ABL regulates death receptor expression for TNF-related apoptosis-inducing ligand (TRAIL) in Philadelphia chromosome-positive leukemia

Allogeneic stem cell transplantation (allo-SCT) is a potentially curative therapy for chronic myeloid leukemia and Philadelphia chromosome-positive (Ph(+)) acute lymphoblastic leukemia, and the graft-vs-leukemia (GVL) effect can eradicate residual leukemia after allo-SCT. Ph(+) leukemia cells frequently express death-inducing receptors (DR4 and DR5) for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which is one of the cytotoxic ligands expressed on cytotoxic T cells and natural killer cells mediating the GVL effect. Here we demonstrate that imatinib specifically downregulated DR4 and DR5 expression in cell lines and clinical samples of Ph(+) leukemia. Second-generation tyrosine kinase inhibitors (dasatinib and nilotinib) and short hairpin RNA against bcr-abl also downregulated DR4 and DR5 expression in Ph(+) leukemia cells, and transfection of bcr-abl into a Ph(-) leukemia cell line induced DR4 and DR5 expression, which was abrogated by imatinib treatment. Accordingly, Ph(+) leukemia cells that had been pretreated with imatinib showed resistance to the pro-apoptotic activity of recombinant human soluble TRAIL. These observations demonstrate that BCR-ABL is critically involved in the leukemia-specific expression of DR4 and DR5 and in the susceptibility of Ph(+) leukemia to TRAIL-mediated anti-leukemic activity, providing new insight into the mechanisms of the tumor-specific cytotoxic activities of TRAIL.