Differential effects of donor T-cell cytokines on outcome with continuous bortezomib administration after allogeneic bone marrow transplantation

Allogeneic stem cell transplantation in multiple myeloma: is there still a place?

The introduction of novel agents dramatically improved response and outcomes of multiple myeloma (MM) and led to a sharp decline in the use of allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Thus, recent guidelines do not recommend anymore allo-HSCT as consolidation in the first-line treatment of newly diagnosed MM, even in high-risk patients. In a relapsed/refractory setting, allo-HSCT is not routinely recommended but should only be performed within clinical trials in young and high-risk patients. Nonetheless, allo-HSCT still represents a potential curative approach that has been used for decades in the treatment of MM and plasma cell neoplasms with favorable results and may still represent a treatment option for carefully selected patients. Despite that promising results were obtained with CAR T-cell therapies and bispecific antibodies in triple- and penta-exposed/refractory MM, these patients will inevitably relapse. To date, less is known about outcomes of allo-HSCT in patients exposed to novel immunotherapeutic drugs. Therefore, allo-HSCT could represent a reasonable treatment choice for younger and high-risk patients who have relapsed after CAR T-cell therapies and bispecific antibodies as well as an alternative for patients not eligible to these treatments and in those countries where immunotherapies are not yet available. In the choice of conditioning, reduced intensity conditioning regimens are currently recommended for the lower toxicity and mortality. Moreover, the use of alternative donors, particularly haploidentical, has progressively increased in last years with results comparable to full matched donors. Finally, post-transplantation maintenance strategies are encouraged whenever feasible.

Translational Clinical Strategies for the Prevention of Gastrointestinal Tract Graft Versus Host Disease

Graft versus host disease (GVHD) is the major non-relapse complication associated with allogeneic hematopoietic stem cell transplantation (HSCT). Unfortunately, GVHD occurs in roughly half of patients following this therapy and can induce severe life-threatening side effects and premature mortality. The pathophysiology of GVHD is driven by alloreactive donor T cells that induce a proinflammatory environment to cause pathological damage in the skin, gastrointestinal (GI) tract, lung, and liver during the acute phase of this disease. Recent work has demonstrated that the GI tract is a pivotal target organ and a primary driver of morbidity and mortality in patients. Prevention of this complication has therefore emerged as an important goal of prophylaxis strategies given the primacy of this tissue site in GVHD pathophysiology. In this review, we summarize foundational pre-clinical studies that have been conducted in animal models to prevent GI tract GVHD and examine the efficacy of these approaches upon subsequent translation into the clinic. Specifically, we focus on therapies designed to block inflammatory cytokine pathways, inhibit cellular trafficking of alloreactive donor T cells to the GI tract, and reconstitute impaired regulatory networks for the prevention of GVHD in the GI tract.

Obesity induces gut microbiota alterations and augments acute graft-versus-host disease after allogeneic stem cell transplantation

The efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by acute and chronic graft-versus-host disease (GVHD). The impact of obesity on allo-HSCT outcomes is poorly understood. Here, we report that obesity had a negative and selective impact on acute gut GVHD after allo-HSCT in mice with diet-induced obesity (DIO). These animals exhibited increased gut permeability, endotoxin translocation across the gut, and radiation-induced gastrointestinal damage after allo-HSCT. After allo-HSCT, both male and female DIO mouse recipients showed increased proinflammatory cytokine production and expression of the GVHD marker ST2 (IL-33R) and MHC class II molecules; they also exhibited decreased survival associated with acute severe gut GVHD. This rapid-onset, obesity-associated gut GVHD depended on donor CD4⁺ T cells and occurred even with a minor MHC mismatch between donor and recipient animals. Retrospective analysis of clinical cohorts receiving allo-HSCT transplants from unrelated donors revealed that recipients with a high body mass index (BMI, >30) had reduced survival and higher serum ST2 concentrations compared with nonobese transplant recipients. Assessment of both DIO mice and allo-HSCT recipients with a high BMI revealed reduced gut microbiota diversity and decreased Clostridiaceae abundance. Prophylactic antibiotic treatment protected DIO mouse recipients from endotoxin translocation across the gut and increased inflammatory cytokine production, as well as gut pathology and mortality, but did not protect against later development of chronic skin GVHD. These results suggest that obesity-induced alterations of the gut microbiota may affect GVHD after allo-HSCT in DIO mice, which could be ameliorated by prophylactic antibiotic treatment.

Allogeneic Stem Cell Transplantation in Patients with High-Risk Multiple Myeloma: Utopia or Continuous Challenge in Aiming for Cure?

OPINION STATEMENT

Nowadays, several novel agents have been introduced in the treatment of multiple myeloma, not only resulting in high response rates and prolonged survival but also offering good quality of life. However, the potential of cure, especially for patients with advanced or unfavorable disease features, remains elusive. Allogeneic hematopoietic stem cell transplantation, based mainly on the graft vs. myeloma effect, can offer prolonged disease control and probability of cure but unfortunately at the cost of considerable transplant-related toxicity rates. Therefore, the role of allogeneic hematopoietic stem cell transplantation in the treatment of multiple myeloma has been called into question. Recently, several studies, particularly those with long-term follow-up, demonstrated a trend of survival superiority for allografted patients with high-risk disease. These data fuel again the interest in allogeneic stem cell transplantation for selected patients with high-risk multiple myeloma, especially if the high remission rates which can be achieved with the currently used treatment protocols could be long-life sustained through the additional exploitation of the long-lasting anti-multiple myeloma effect, originating from the allograft.

Therapeutic Effects of a NEDD8-Activating Enzyme Inhibitor, Pevonedistat, on Sclerodermatous Graft-versus-Host Disease in Mice

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole treatment option for highly malignant hematologic disease; however, the major complication-graft-versus-host disease (GVHD)-still hinders its clinical application. In addition, chronic GVHD remains the major cause of long-term morbidity and mortality after allo-HSCT. Previously we showed that bortezomib, a proteasome inhibitor, can ameliorate the sclerodermatous GVHD response while maintaining graft-versus-tumor (GVT) effects. Here we report that pevonedistat (MLN4924), an inhibitor of the Nedd8-activating enzyme, which functions upstream of the proteasome in the ubiquitin-proteasome pathway, can also show similar protective effects. Recipient mice treated with pevonedistat demonstrated inhibitory effects on sclerodermatous GVHD pathogenesis. The beneficial effect of pevonedistat was observed to be temporally dependent. Whereas treatment given at the time of allo-HSCT administration or before the onset of symptoms worsened the scleroderma response, therapeutic administration starting at 20 days post-transplantation ameliorated the sclerodermatous GVHD. Flow cytometry analysis revealed differential effects on immune subsets, with inhibition of only antigen-presenting cells and not of donor T cells. Finally, pevonedistat preserved GVT effects in a sclerodermatous murine model of B cell lymphoma. Taken together, these data suggest that inhibition of neddylation with pevonedistat can serve as an alternative approach for the treatment of GVHD while maintaining GVT effects in a murine model of sclerodermatous GVHD.

Inhibition of the Immunoproteasome Subunit LMP7 with ONX 0914 Ameliorates Graft-versus-Host Disease in an MHC-Matched Minor Histocompatibility Antigen-Disparate Murine Model

In the current study we evaluated the effects of immunoproteasome inhibition using ONX 0914 (formerly PR-957) to ameliorate graft-versus-host disease (GVHD). ONX 0914, an LMP7-selective epoxyketone inhibitor of the immunoproteasome, has been shown to reduce cytokine production in activated monocytes and T cells and attenuate disease progression in mouse models of rheumatoid arthritis, colitis, systemic lupus erythematosus, and, more recently, encephalomyelitis. Inhibition of LMP7 with ONX 0914 in the B10.BR→CBA MHC-matched/minor histocompatibility antigen (miHA)-disparate murine blood and marrow transplant (BMT) model caused a modest but significant improvement in the survival of mice experiencing GVHD. Concomitant with these results, in vitro mixed lymphocyte cultures revealed that stimulator splenocytes, but not responder T cells, treated with ONX 0914 resulted in decreased IFN-γ production by allogeneic T cells in both MHC-disparate (B10.BR anti-B6) and miHA-mismatched (B10.BR anti-CBA) settings. In addition, a reduction in the expression of the MHC class I-restricted SIINFEKL peptide was observed in splenocytes from transgenic C57BL/6-Tg(CAG-OVA)916Jen/J mice exposed to ONX 0914. Taken together, these data support that LMP7 inhibition in the context of BMT modulates allogeneic responses by decreasing endogenous miHA presentation and that the consequential reduction in allogeneic stimulation and cytokine production reduces GVHD development.

The complex and central role of interferon-γ in graft-versus-host disease and graft-versus-tumor activity

Allogeneic hematopoietic cell transplantation (allo-HCT) is increasingly being performed to treat patients with hematologic malignancies. However, separating the beneficial graft-versus-tumor (GVT) or graft-versus-leukemia effects from graft-versus-host disease (GVHD) has been difficult and remains a significant challenge toward improving therapeutic efficacy and reducing toxicity of allo-HCT. GVHD is induced by donor T cells that also mediate potent anti-tumor responses. However, despite the largely shared effector mechanisms, extensive animal studies have demonstrated the potential of dissociating the GVT effect from GVHD. Also in many clinical cases, long-term remission was achieved following allo-HCT, without significant GVHD. A better mechanistic understanding of the immunopathophysiology of GVHD and GVT effects may potentially help to improve allo-HCT as well as maximize the benefit of GVT effects while minimizing GVHD. In this article, we review the role of IFN-γ in regulation of alloresponses following allo-HCT, with a focus on the mechanisms of how this cytokine may separate GVHD from GVT effects.

Bone Marrow Derived Kit-positive Cells Colonize the Gut but Fail to Restore Pacemaker Function in Intestines Lacking Interstitial Cells of Cajal

Background/Aims

Several motility disorders are associated with disruption of interstitial cells of Cajal (ICC), which provide important functions, such as pacemaker activity, mediation of neural inputs and responses to stretch in the gastrointestinal (GI) tract. Restoration of ICC networks may be therapeutic for GI motor disorders. Recent reports have suggested that Kit⁺ cells can be restored to the GI tract via bone marrow (BM) transplantation. We tested whether BM derived cells can lead to generation of functional activity in intestines naturally lacking ICC.

Methods

BM cells from Kit^+/copGFP mice, in which ICC are labeled with a green fluorescent protein, were transplanted into W/W^V intestines, lacking ICC. After 12 weeks the presence of ICC was analyzed by immunohistochemistry and functional analysis of electrical behavior and contractile properties.

Results

After 12 weeks copGFP⁺ BM derived cells were found within the myenteric region of intestines from W/W^V mice, typically populated by ICC. Kit⁺ cells failed to develop interconnections typical of ICC in the myenteric plexus. The presence of Kit⁺ cells was verified with Western analysis. BM cells failed to populate the region of the deep muscular plexus where normal ICC density, associated with the deep muscular plexus, is found in W/W^V mice. Engraftment of Kit⁺-BM cells resulted in the development of unitary potentials in transplanted muscles, but slow wave activity failed to develop. Motility analysis showed that intestinal movements in transplanted animals were abnormal and similar to untransplanted W/W^V intestines.

Conclusions

BM derived Kit⁺ cells colonized the gut after BM transplantation, however these cells failed to develop the morphology and function of mature ICC.

Therapeutic benefit of bortezomib on acute graft-versus-host disease is tissue specific and is associated with interleukin-6 levels

Bortezomib, a proteasome inhibitor capable of direct antitumor effects, has been shown to prevent acute graft-versus-host disease (GVHD) when administered in a short course immediately after bone marrow transplantation (BMT) in mice. However, when bortezomib is given continuously, CD4(+) T cell-mediated gastrointestinal tract damage increases GVHD mortality. To investigate the protective effects of bortezomib on other organs, we used a CD8-dependent acute GVHD (aGVHD) model of C3H.SW donor T cells engrafted into irradiated C57BL/6 recipients (minor MHC mismatch), which lack significant gut GVHD. Our data in this model show that bortezomib can be given continuously to prevent and treat aGVHD mediated by CD8(+) T cells, but this effect is organ specific, such that only skin, and not liver, protection was observed. Despite the lack of hepatic protection, bortezomib still significantly improved survival, primarily because of its skin protection. Reduced skin GVHD by bortezomib was correlated with reduced serum and skin IL-6 levels. Administration of a blocking IL-6 antibody in this model also resulted in similar cutaneous GVHD protection. These results indicate that bortezomib or blockade of IL-6 may prevent CD8(+) T cell-mediated cutaneous acute GVHD.

Treatment of chronic graft-versus-host disease with bortezomib

Chronic graft-versus-host disease (cGVHD) following allogeneic hematopoietic stem cell transplantation (HSCT) has emerged as a predominant complication following HSCT and has a distinct etiology. We and others have previously demonstrated that bortezomib, a proteasome inhibitor, can prevent but not treat acute GVHD in mice. To assess the effects of bortezomib on cGVHD, a mouse minor histocompatibility antigen-mismatched strain combination was used to mimic clinical cGVHD sclerodermatous pathogenesis and phenotype. Treatment of ongoing cGVHD with bortezomib ameliorated cutaneous lesions, which were also associated with a reduction in total numbers of germinal center B cells and lower B-cell activating factor gene expression levels in cutaneous tissues. Importantly, lymphoma-bearing mice receiving allogeneic HSCT with bortezomib preserved graft-versus-tumor (GVT) effects. Based on these animal studies, we initiated an intrapatient dose escalation clinical trial in patients with extensive steroid-intolerant, dependent, or resistant cGVHD. Marked clinical improvement was observed in patients, which was also associated with reductions of peripheral B cells and minimal toxicity. These results indicate that bortezomib can be of significant use in the treatment of cGVHD and may also allow for maintenance of GVT. This trial was registered at www.clinicaltrials.gov as #NCT01672229.

Utilizing glycogen synthase kinase-3β as a marker for the diagnosis of graft-versus-host disease

INTRODUCTION

Graft-versus-host disease (GVHD) is a deadly complication of allogeneic hematopoietic stem cell transplantation. Timely diagnosis is critical, because mortality rates for GVHD are high, increasing with disease severity. A diagnostic tool to predict GVHD before the onset of clinical symptoms could save many lives. On the cellular level, GVHD occurs when T cells from the transplant attack the tissues of the host, after perceiving them to be foreign. T-cell proliferation occurs even before clinical symptoms appear. Glycogen synthase kinase (GSK)-3β is a protein which regulates proliferation in many cell types including T-cells. GSK-3β has never been directly connected with GVHD and we applied GSK-3β as a novel marker for GVHD prediction, seeking herein to determine whether GSK-3β can be utilized as a marker for the early diagnosis of GVHD.

METHODS

For the mouse model of acute GVHD, irradiated mice underwent allogeneic splenocyte transplantation and GSK-3β expression levels and phosphorylation states were monitored in harvested spleens by western blot. FACS analysis was used to measure the number of T cells within the harvested spleens.

RESULTS

Mice developed observable GVHD symptoms by day 5 post-transplantation, with severe symptoms on day 6 requiring mice to be killed for humane reasons. A significantly increased number of T cells in the allogeneic mice correlated with GVHD development. GSK-3β protein expression levels and phosphorylation levels were significantly lower in allogeneic (GVHD) mice compared with negative (untreated) and positive (syngeneic transplant; non-GVHD) controls over time.

CONCLUSION

GSK-3β was directly connected with the onset and progression of GVHD. Therefore, it can be utilized as a marker for GVHD diagnosis in animals and potentially in humans.

IL-1β and TLR4 signaling are involved in the aggravated murine acute graft-versus-host disease caused by delayed bortezomib administration

It was shown that the proteasome inhibitor, bortezomib, administered immediately following allogeneic bone marrow transplantation resulted in marked inhibition of acute graft-versus-host disease (aGVHD), with retention of graft-versus-tumor effects. However, continuous bortezomib administration resulted in significant acceleration of graft-versus-host disease-dependent morbidity. We carried out studies to dissect the mechanisms of aggravated aGVHD caused by delayed bortezomib administration. First, we demonstrated that IL-1β was critically involved, and the subsequent aGVHD could be alleviated by IL-1β blockade. Bortezomib treatment after dendritic cell (DC) activation resulted in drastically elevated IL-1β production, whereas bortezomib treatment before DC activation inhibited IL-1β production, suggesting that the timing of bortezomib administration significantly affected IL-1β production by DCs. We further demonstrated that delayed administration of bortezomib accelerated aGVHD through TLR4 signaling. Because the LPS levels were much lower with reduced-intensity conditioning compared with high-dose irradiation, the accelerated graft-versus-host disease-dependent morbidity with delayed bortezomib administration could be rescued by reduced-intensity conditioning. Our studies suggested that TLR4 pathway activation and delayed bortezomib administration amplified the production of IL-1β and other inflammatory cytokines, which resulted in accelerated aGVHD-dependent morbidity. These results indicated that decreased toxicity of continuous bortezomib administration could be achieved by reduced-intensity conditioning or by inhibiting IL-1β.

Egr2 induced during DC development acts as an intrinsic negative regulator of DC immunogenicity

Early growth response gene 2 (Egr2), which encodes a zinc finger transcription factor, is rapidly and transiently induced in various cell types independently of de novo protein synthesis. Although a role for Egr2 is well established in T-cell development, Egr2 expression and its biological function in dendritic cells (DCs) have not yet been described. Here, we demonstrate Egr2 expression during DC development, and its role in DC-mediated immune responses. Egr2 is expressed in the later stage of DC development from BM precursor cells. Even at steady state, Egr2 is highly expressed in mouse splenic DCs. Egr2-knockdown (Egr2-KD) DCs showed increased levels of major histocompatability complex (MHC) class I and II and co-stimulatory molecules, and enhanced antigen uptake and migratory capacities. Furthermore, Egr2-KD abolished SOCS1 expression and signal transducer and activator of transcription 5 (STAT5) activation during DC development, probably resulting in the enhancement of IL-12 expression and Th1 immunogenicity of a DC vaccine. DC-mediated cytotoxic T lymphocyte (CTL) activation and antitumor immunity were significantly enhanced by Egr2-KD, and impaired by Egr2 overexpression in antigen-pulsed DC vaccines. These data suggest that Egr2 acts as an intrinsic negative regulator of DC immunogenicity and can be an attractive molecular target for DC vaccine development.

Proteasome inhibitors as immunosuppressants: biological rationale and clinical experience

Accumulating evidence supports the potential of proteasome inhibitors as immunosuppressants. Proteasome inhibitors interfere with antigen processing and presentation, as well as with the signaling cascades involved in immune cell function and survival. Both myeloma and healthy plasma cells appear to be highly susceptible to proteasome inhibitors due to impaired proteasomal activity in both cell types. As a consequence, these agents can be used to reduce antibody production and thus prevent antibody-induced tissue damage. Several clinical studies have explored the potential of bortezomib, a peptide boronate proteasome inhibitor, for treating immune disorders, such as antibody-mediated organ rejection and graft-versus-host disease (GVHD), with encouraging results. Here, we discuss the biological rationale for the use of proteasome inhibitors as immunosuppressive agents and review the clinical experience with bortezomib in immune-mediated diseases.

Emerging therapies in hematopoietic stem cell transplantation

Despite improvements to hematopoietic stem cell transplantation over the past several decades, further advances are necessary to achieve: improved control of toxicities like graft-versus-host disease; enhanced immunologic reconstitution posttransplantation; and reduction in relapse risk via enhancement of graft-versus-tumor responses. Achieving these disparate hematopoietic stem cell transplantation goals will likely require the introduction of novel therapeutic agents to the current armamentarium. In this article, we outline preclinical and early-phase clinical data indicating the potential of proteasome-inhibitor therapy (bortezomib), hypomethylating agent therapy (azacytidine), and histone deacetylase-inhibitor therapy (vorinostat) to help improve hematopoietic stem cell transplantation outcomes.

Mast cells promote the growth of Hodgkin's lymphoma cell tumor by modifying the tumor microenvironment that can be perturbed by bortezomib

Hodgkin's lymphoma is frequently associated with mast cell infiltration that correlates directly with disease severity, but the mechanisms underlying this relationship remain unclear. Here, we report that mast cells promote the growth of Hodgkin's tumor by modifying the tumor microenvironment. A transplantation assay shows that primary murine mast cells accelerate tumor growth by established Hodgkin's cell lines, and promote marked neovascularization and fibrosis. Both mast cells and Hodgkin's cells were sensitive to bortezomib, but mast cells were more resistant to bortezomib. However, bortezomib inhibited degranulation, PGE(2)-induced rapid release of CCL2, and continuous release of vascular endothelial growth factor-A from mast cells even at the concentration that did not induce cell death. Bortezomib-treated mast cells lost the ability to induce neovasculization and fibrosis, and did not promote the growth of Hodgkin tumor in vivo. These results provide further evidence supporting causal relationships between inflammation and tumor growth, and demonstrate that bortezomib can target the tumor microenvironment.

Combination of intra-bone marrow-bone marrow transplantation and subcutaneous donor splenocyte injection diminishes risk of graft-versus-host disease and enhances survival rate

The combination of allogeneic bone marrow transplantation (allo-BMT) and donor lymphocyte infusion (DLI) is a useful method for establishing donor chimerism and preventing a relapse of leukemia/lymphoma. However, there is a risk of inducing uncontrollable fatal graft-versus-host disease (GVHD). In fact, allo-BMT plus intravenous (IV)-DLI using donor splenocytes induces fatal GVHD in recipient mice. In this study, we examined the effects of the combination of intra-bone marrow (IBM)-BMT and the subcutaneous injection of donor splenocytes (SC-DLI) on the allo-BMT system. Recipient BALB/c mice were conditioned by sublethal irradiation (5 Gy), followed by IBM-BMT plus IV-DLI or SC-DLI in C57BL/6 mice. The IV-DLI group showed better engraftment of donor hemopoietic cells than the control group (without DLI) but showed fatal GVHD. The SC-DLI group, however, showed good reconstitution and mild GVHD. These results suggest that the combination of SC-DLI and IBM-BMT promotes the reconstitution of hemopoiesis and helps reduce the risk of GVHD.

Immunotherapy following hematopoietic stem cell transplantation: potential for synergistic effects

Hematopoietic stem cell transplantation (HSCT) is a particularly important treatment for hematologic malignancies. Unfortunately, following allogeneic HSCT, graft-versus-host disease, immunosuppression and susceptibility to opportunistic infections remain among the most substantial problems restricting the efficacy and use of this procedure, particularly for cancer. Adoptive immunotherapy and/or manipulation of the graft offer ways to attack residual cancer as well as other transplant-related complications. Recent exciting discoveries have demonstrated that HSCT could be expanded to solid tissue cancers with profound effects on the effectiveness of adoptive immunotherapy. This review will provide a background regarding HSCT, discuss the complications that make it such a complex treatment procedure following up with current immunotherapeutic strategies and discuss emerging approaches in applying immunotherapy in HSCT for cancer.

The triterpenoid CDDO-Me delays murine acute graft-versus-host disease with the preservation of graft-versus-tumor effects after allogeneic bone marrow transplantation

The occurrence of acute graft-versus-host disease (aGVHD) and tumor relapse represent the two major obstacles impeding the efficacy of allogeneic bone marrow transplantation (BMT) in cancer. We have previously shown that the synthetic triterpenoid 2-cyano-3, 12-dioxooleana-1, 9-dien-28-oic acid (CDDO) can inhibit murine early aGVHD, but antitumor effects were not assessed. In the current study, we found that a new derivative of CDDO, CDDO-Me, had an increased ability to inhibit allogeneic T cell responses and induce cell death of alloreactive T cells in vitro. Administration of CDDO-Me to mice following allogeneic BMT resulted in significant and increased protection from lethal aGVHD compared to CDDO. This correlated with reduced TNF-alpha production, reduced donor T cell proliferation, and decreased adhesion molecule (alpha(4)beta(7) integrin) expression on the donor T cells. CDDO-Me was also superior to CDDO in inhibiting leukemia growth in vitro. When CDDO-Me was administered following an allogeneic BMT to leukemia-bearing mice, significant increases in survival were observed. These findings suggest that CDDO-Me is superior to CDDO in delaying aGVHD, while preserving or possibly even augmenting GVT effects.

Proteasome inhibition and allogeneic hematopoietic stem cell transplantation: a review

The proteasome and its associated ubiquitin protein modification system have proved to be an important therapeutic target in the treatment of multiple myeloma and other cancers. In addition to direct antitumor effects, proteasome inhibition also exerts strong effects on nonneoplastic immune cells. This indicates that proteasome inhibition, through the use of agents like bortezomib, could be used therapeutically to modulate immune responses. In this review we explore the emerging data, both preclinical and clinical, highlighting the importance of proteasome targeting of immunologic responses, primarily in the context of allogeneic hematopoietic stem cell transplantation (HSCT), both for the control of transplant-related toxicities like acute and chronic graft-versus-host disease (aGVHD, cGHVHD), and for improved malignant disease control after allogeneic HSCT.

Personalizing Stem Cell Research and Therapy: The Arduous Road Ahead or Missed Opportunity?

The euphoria of stem cell therapy has diminished, allowing scientists, clinicians and the general public to seriously re-examine how and what types of stem cells would effectively repair damaged tissue, prevent further tissue damage and/or replace lost cells. Importantly, there is a growing recognition that there are substantial person-to-person differences in the outcome of stem cell therapy. Even though the small molecule pharmaceuticals have long remained a primary focus of the personalized medicine research, individualized or targeted use of stem cells to suit a particular individual could help forecast potential failures of the therapy or identify, early on, the individuals who might benefit from stem cell interventions. This would however demand collaboration among several specialties such as pharmacology, immunology, genomics and transplantation medicine. Such transdisciplinary work could also inform how best to achieve efficient and predictable stem cell migration to sites of tissue damage, thereby facilitating tissue repair. This paper discusses the possibility of polarizing immune responses to rationalize and individualize therapy with stem cell interventions, since generalized "one-size-fits-all" therapy is difficult to achieve in the face of the diverse complexities posed by stem cell biology. We also present the challenges to stem cell delivery in the context of the host related factors. Although we focus on the mesenchymal stem cells in this paper, the overarching rationale can be extrapolated to other types of stem cells as well. Hence, the broader purpose of this paper is to initiate a dialogue within the personalized medicine community by expanding the scope of inquiry in the field from pharmaceuticals to stem cells and related cell-based health interventions.

Ex vivo inhibition of NF-kappaB signaling in alloreactive T-cells prevents graft-versus-host disease

The ex vivo induction of alloantigen-specific hyporesponsiveness by costimulatory pathway blockade or exposure to immunoregulatory cytokines has been shown to inhibit proliferation, IL-2 production, and the graft-versus-host disease (GVHD) capacity of adoptively transferred T-cells. We hypothesized that inhibition of the intracellular NF-kappaB pathway in alloreactive T-cells, which is critical for T-cell activation events including IL-2 transcription, could lead to alloantigen hyporesponsiveness and loss of GVHD capacity. We demonstrate that treatment of mixed lymphocyte reaction (MLR) cultures with PS1145, a potent inhibitor of NF-kappaB activation, can induce T-cell hyporesponsiveness to alloantigen in primary and secondary responses while preserving in vitro responses to potent mitogenic stimulation. GVHD lethality in recipients of ex vivo PS1145-treated cells was profoundly inhibited. Parking of control or PS1145-treated MLR cells in syngeneic Rag(-/-) recipients resulted in intact contact hypersensitivity (CHS) responses. However, GVHD lethality capacity also was restored, suggesting that lymphopenic expansion uncoupled alloantigen hyporesponsiveness. These results indicate that the NF-kappaB pathway is a critical regulator of alloresponses and provide a novel small molecule inhibitor based approach that is effective in preventing early posttransplant GVHD lethality but that also permits donor T-cell responses to recover after a period of lymphopenic expansion.

Clinical-grade ex vivo-expanded human natural killer cells up-regulate activating receptors and death receptor ligands and have enhanced cytolytic activity against tumor cells

BACKGROUND AIMS

Cancer immunotherapy involving natural killer (NK) cell infusions and administration of therapeutic agents modulating the susceptibility of tumors to NK-cell lysis has been proposed recently. We provide a method for expanding highly cytotoxic clinical-grade NK cells in vitro for adoptive transfer following bortezomib treatment in patients with advanced malignancies.

METHODS

NK cells were expanded with irradiated Epstein-Barr virus-transformed lymphoblastoid cells. Expanded cells were evaluated for their phenotype, cytotoxicity, cytokine secretion, dependence on interleukin (IL)-2 and ability to retain function after cryopreservation.

RESULTS

A pure population of clinical-grade NK cells expanded 490+/-260-fold over 21 days. Expanded NK cells had increased TRAIL, FasL and NKG2D expression and significantly higher cytotoxicity against bortezomib-treated tumors compared with resting NK cells. Expanded NK cells, co-cultured with K562 and renal cell carcinoma tumor targets, secreted significantly higher levels of soluble Fas ligand 6; fgjhd IFN-gamma, GM-CSF, TNF-alpha, MIP-1alpha and MIP-1beta compared with resting NK cells. Secretion of the above cytokines and NK-cell cytolytic function were IL-2 dose dependent. Cryopreservation of expanded NK cells reduced expression of NKG2D and TRAIL and NK-cell cytotoxicity, although this effect could be reversed by exposure of NK cells to IL-2.

CONCLUSIONS

We describe a method for large-scale expansion of NK cells with increased expression of activating receptors and death receptor ligands resulting in superior cytotoxicity against tumor cells. This ex vivo NK-cell expansion technique is currently being utilized in a clinical trial evaluating the anti-tumor activity of adoptively infused NK cells in combination with bortezomib.