Erin Gatza

Histone deacetylase inhibition modulates indoleamine 2,3-dioxygenase–dependent DC functions and regulates experimental graft-versus-host disease in mice

Histone deacetylase (HDAC) inhibitors are antitumor agents that also have antiinflammatory properties. However, the mechanisms of their immunomodulatory functions are not known. We investigated the mechanisms of action of 2 HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and ITF 2357, on mouse DC responses. Pretreatment of DCs with HDAC inhibitors significantly reduced TLR-induced secretion of proinflammatory cytokines, suppressed the expression of CD40 and CD80, and reduced the in vitro and in vivo allostimulatory responses induced by the DCs. In addition, injection of DCs treated ex vivo with HDAC inhibitors reduced experimental graft-versus-host disease (GVHD) in a murine allogeneic BM transplantation model. Exposure of DCs to HDAC inhibitors increased expression of indoleamine 2,3-dioxygenase (IDO), a suppressor of DC function. Blockade of IDO in WT DCs with siRNA and with DCs from IDO-deficient animals caused substantial reversal of HDAC inhibition-induced in vitro suppression of DC-stimulated responses. Direct injection of HDAC inhibitors early after allogeneic BM transplantation to chimeric animals whose BM-derived cells lacked IDO failed to protect from GVHD, demonstrating an in vivo functional role for IDO. Together, these data show that HDAC inhibitors regulate multiple DC functions through the induction of IDO and suggest that they may represent a novel class of agents to treat immune-mediated diseases.

Extracorporeal photopheresis reverses experimental graft-versus-host disease through regulatory T cells

Extracorporeal photopheresis (ECP), a technique that exposes isolated white blood cells to photoactivatable 8-methoxypsoralen and ultraviolet A radiation, is used clinically to treat cutaneous T-cell lymphoma and immune-mediated diseases such as graft-versus-host disease (GVHD). ECP is thought to control these diseases in part through direct induction of lymphocyte apoptosis, but its effects on the immune system beyond apoptosis remain poorly characterized. We have developed a novel method for incorporating ECP treatment into well-established and clinically relevant murine models of GVHD to examine its effects during an ongoing immune response. We demonstrate that the transfer of cells treated with ECP reverses established GVHD by increasing donor regulatory T cells and indirectly reducing the number of donor effector lymphocytes that themselves had never been exposed to psoralen and ultraviolet A radiation.

Manipulating the Bioenergetics of Alloreactive T Cells Causes Their Selective Apoptosis and Arrests Graft-Versus-Host Disease

Bioenergetic properties differentiate alloreactive T cells from other proliferating cells and can be exploited to arrest GVHD in mice. A Xenophobe’s Guide to Treating Graft-Versus-Host Disease Immune cells are in essence xenophobes—they distinguish and then attack cells that are foreign to the body. This prejudice is helpful in the context of infection or cancer; the immune system raises destructive responses directed against stranger cells that have been infected or transformed while remaining calm in the presence of healthy cells recognized as “self.” However, when immune cells are transferred to a new host, for example, by bone marrow transplantation, these cells see the patient’s own tissues as foreign and attack, resulting in graft-versus-host disease (GVHD). Gatza et al. have found a way to differentiate these so-called alloreactive donor cells from non-alloreactive donor cells and host immune cells and thus provide a target for preventing GVHD. Cells can generate energy in the form of adenosine triphosphate (ATP) through either aerobic glycolysis or oxidative phosphorylation (OXPHOS). In general, proliferating lymphocytes preferentially use aerobic glycolysis, which produces significantly fewer ATP molecules than OXPHOS, but little is known about the specific metabolic requirements of proliferating alloreactive T cells. Gatza et al. found that after bone marrow transplantation, alloreactive T cells, but not other proliferating T cells and bone marrow cells, up-regulated both aerobic glycolysis and OXPHOS to meet their increased energy demand. Relative to other proliferating cells, alloreactive T cells produced higher concentrations of acylcarnitines—fatty acid oxidation intermediates that transport fatty acids into the mitochondrial matrix. Further highlighting their altered metabolism, alloreactive T cells could be specifically killed by Bz-423, a small-molecule inhibitor of the mitochondrial F1F0-ATPase, and Bz-423 decreased the severity of GVHD in mice without impairing transplant engraftment and bone marrow reconstitution. Thus, bioenergetic differences may provide targets for order-maintaining therapeutics that stop alloreactive T cells from attacking perceived foreigners in the transplanted immune cells’ new neighborhood. Cells generate adenosine triphosphate (ATP) by glycolysis and by oxidative phosphorylation (OXPHOS). Despite the importance of having sufficient ATP available for the energy-dependent processes involved in immune activation, little is known about the metabolic adaptations that occur in vivo to meet the increased demand for ATP in activated and proliferating lymphocytes. We found that bone marrow (BM) cells proliferating after BM transplantation (BMT) increased aerobic glycolysis but not OXPHOS, whereas T cells proliferating in response to alloantigens during graft-versus-host disease (GVHD) increased both aerobic glycolysis and OXPHOS. Metabolomic analysis of alloreactive T cells showed an accumulation of acylcarnitines consistent with changes in fatty acid oxidation. Alloreactive T cells also exhibited a hyperpolarized mitochondrial membrane potential (ΔΨm), increased superoxide production, and decreased amounts of antioxidants, whereas proliferating BM cells did not. Bz-423, a small-molecule inhibitor of the mitochondrial F1F0 adenosine triphosphate synthase (F1F0-ATPase), selectively increased superoxide and induced the apoptosis of alloreactive T cells, which arrested established GVHD in several BMT models without affecting hematopoietic engraftment or lymphocyte reconstitution. These findings challenge the current paradigm that activated T cells meet their increased demands for ATP through aerobic glycolysis, and identify the possibility that bioenergetic and redox characteristics can be selectively exploited as a therapeutic strategy for immune disorders.

Cutting Edge: Negative Regulation of Dendritic Cells through Acetylation of the Nonhistone Protein STAT-3

Histone deacetylase (HDAC) inhibition modulates dendritic cell (DC) functions and regulates experimental graft-vs-host disease and other immune-mediated diseases. The mechanisms by which HDAC inhibition modulates immune responses remain largely unknown. STAT-3 is a transcription factor shown to negatively regulate DC functions. In this study we report that HDAC inhibition acetylates and activates STAT-3, which regulates DCs by promoting the transcription of IDO. These findings demonstrate a novel functional role for posttranslational modification of STAT-3 through acetylation and provide mechanistic insights into HDAC inhibition-mediated immunoregulation by induction of IDO.

Tumor Cell Lysate-Pulsed Dendritic Cells Are More Effective Than TCR Id Protein Vaccines for Active Immunotherapy of T Cell Lymphoma

TCR Id protein conjugated to keyhole limpet hemocyanin (KLH) (TCR Id:KLH) and injected with a chemical adjuvant (QS-21) induces a protective, Id-specific immune response against the murine T cell lymphoma, C6VL. However, Id-based immunotherapy of C6VL has not demonstrated therapeutic efficacy in tumor-bearing mice. We report here that C6VL lysate-pulsed dendritic cells (C6VL-DC) vaccines display enhanced efficacy in both the prevention and the therapy of T cell lymphoma compared with TCR Id:KLH with QS-21 vaccines. C6VL-DC vaccines stimulated potent tumor-specific immunity that protected mice against lethal challenge with C6VL and significantly enhanced the survival of tumor-bearing mice. Tumor-specific proliferation and secretion of IFN-γ indicative of a Th1-type immune response were observed upon ex vivo stimulation of vaccine-primed lymph node cells. Adoptive transfer of immune T cell-enriched lymphocytes was sufficient to protect naive recipients from lethal tumor challenge. Furthermore, CD8+ T cells were absolutely required for tumor protection. Although C6VL-DC and control vaccines stimulated low levels of tumor-specific Ab production in mice, Ab levels did not correlate with the protective ability of the vaccine. Thus, tumor cell lysate-pulsed DC vaccines appear to be an effective approach to generate potent T cell-mediated immune responses against T cell malignancies without requiring identification of tumor-specific Ags or patient-specific Id protein expression.

Histone deacetylase inhibition regulates inflammation and enhances Tregs after allogeneic hematopoietic cell transplantation in humans

We examined immunological responses in patients receiving histone deacetylase (HDAC) inhibition (vorinostat) for graft-versus-host disease prophylaxis after allogeneic hematopoietic cell transplant. Vorinostat treatment increased histone acetylation in peripheral blood mononuclear cells (PBMCs) from treated patients, confirming target HDAC inhibition. HDAC inhibition reduced proinflammatory cytokine levels in plasma and from PBMCs and decreased ex vivo responses of PBMCs to proinflammatory TLR-4 stimuli, but did not alter the number or response of conventional T cells to nonspecific stimuli. However, the numbers of regulatory T cells (Tregs) were increased, which revealed greater demethylation of the Foxp3 T regulatory-specific demethylation region. Vorinostat-treated patients showed increased expression of CD45RA and CD31 on Tregs, and these Tregs demonstrated greater suppression on a per cell basis. Consistent with preclinical findings, HDAC inhibition also increased signal transducer and activator of transcription 3 acetylation and induced indoleamine-2,3-dioxygenase. Our data demonstrate that HDAC inhibition reduces inflammatory responses of PBMC but enhances Tregs after allo-HCT.

FLT3 mutational status is an independent risk factor for adverse outcomes after allogeneic transplantation in AML.

Allogeneic hematopoietic cell transplantation (HCT) has been increasingly used in the setting of FMS-like tyrosine kinase-3 (FLT3)-mutated AML. However, its role in conferring durable relapse-free intervals remains in question. Herein we sought to investigate FLT3 mutational status on transplant outcomes. We conducted a retrospective cohort study of 262 consecutive AML patients who underwent first-time allogeneic HCT (2008–2014), of whom 171 had undergone FLT3-ITD (internal tandem duplication) mutational testing. FLT3-mutated AML was associated with nearly twice the relapse risk (RR) compared with those without FLT3 mutation 3 years post-HCT (63% vs 37%, P<0.001) and with a shorter median time to relapse (100 vs 121 days). FLT3 mutational status remained significantly associated with this outcome after controlling for patient, disease and transplant-related risk factors (P<0.05). Multivariate analysis showed a significant association of FLT3 mutation with increased 3-year RR (hazard ratio (HR) 3.63, 95% confidence interval (CI): 2.13, 6.19, P<0.001) and inferior disease-free survival (HR 2.05, 95% CI: 1.29, 3.27, P<0.01) and overall survival (HR 1.92, 95% CI: 1.14, 3.24, P<0.05). These data demonstrate high risk of early relapse after allogeneic HCT for FLT3-mutated AML that translates into adverse disease-free and overall survival outcomes. Additional targeted and coordinated interventions are needed to maintain durable remission after allogeneic HCT in this high-risk population.

Vorinostat plus tacrolimus/methotrexate to prevent GVHD after myeloablative conditioning, unrelated donor HCT

The oral histone deacetylase (HDAC) inhibitor (vorinostat) is safe and results in low incidence of acute graft-versus-host disease (GVHD) after reduced-intensity conditioning, related donor hematopoietic cell transplantation (HCT). However, its safety and efficacy in preventing acute GVHD in settings of heightened clinical risk that use myeloablative conditioning, unrelated donor (URD), and methotrexate are not known. We conducted a prospective, phase 2 study in this higher-risk setting. We enrolled 37 patients to provide 80% power to detect a significant difference in grade 2 to 4 acute GVHD of 50% compared with a reduction in target to 28%. Eligibility included adults with a hematological malignancy to receive myeloablative HCT from an available 8/8-HLA matched URD. Patients received GVHD prophylaxis with tacrolimus and methotrexate. Vorinostat (100 mg twice daily) was started on day -10 and continued through day +100 post-HCT. Median age was 56 years (range, 18-69 years), and 95% had acute myelogenous leukemia or high-risk myelodysplastic syndrome. Vorinostat was safe and tolerable. The cumulative incidence of grade 2 to 4 acute GVHD at day 100 was 22%, and for grade 3 to 4 it was 8%. The cumulative incidence of chronic GVHD was 29%; relapse, nonrelapse mortality, GVHD-free relapse-free survival, and overall survival at 1 year were 19%, 16%, 47%, and 76%, respectively. Correlative analyses showed enhanced histone (H3) acetylation in peripheral blood mononuclear cells and reduced interleukin 6 (P = .028) and GVHD biomarkers (Reg3, P = .041; ST2, P = .002) at day 30 post-HCT in vorinostat-treated subjects compared with similarly treated patients who did not receive vorinostat. Vorinostat for GVHD prevention is an effective strategy that should be confirmed in a randomized phase 3 study. This trial was registered at www.clinicaltrials.gov as #NCT01790568.

Differential susceptibility of C57BL/6NCr and B6.Cg-Ptprca mice to commensal bacteria after whole body irradiation in translational bone marrow transplant studies.

BackgroundThe mouse is an important and widely utilized animal model for bone marrow transplant (BMT) translational studies. Here, we document the course of an unexpected increase in mortality of congenic mice that underwent BMT.MethodsThirty five BMTs were analyzed for survival differences utilizing the Log Rank test. Affected animals were evaluated by physical examination, necropsy, histopathology, serology for antibodies to infectious disease, and bacterial cultures.ResultsSevere bacteremia was identified as the main cause of death. Gastrointestinal (GI) damage was observed in histopathology. The bacteremia was most likely caused by the translocation of bacteria from the GI tract and immunosuppression caused by the myeloablative irradiation. Variability in groups of animals affected was caused by increased levels of gamma and X-ray radiation and the differing sensitivity of the two nearly genetically identical mouse strains used in the studies.ConclusionOur retrospective analysis of thirty five murine BMTs performed in three different laboratories, identified C57BL/6NCr (Ly5.1) as being more radiation sensitive than B6.Cg-Ptprca/NCr (Ly5.2). This is the first report documenting a measurable difference in radiation sensitivity and its effects between an inbred strain of mice and its congenic counterpart eventually succumbing to sepsis after BMT.

Analytic morphomics: A novel CT imaging approach to quantify adipose tissue and muscle composition in allogeneic hematopoietic cell transplantation

Analytic morphomics is a novel methodology that uses high-throughput computed tomography (CT) processing techniques to generate reproducible body measurements (Supplementary Table).1, 2, 3, 4 Body mass index is widely used in clinical and public health studies to predict mortality risk.5 Indeed, we recently examined its impact in allogeneic hematopoietic cell transplantation (HCT) and found that obese patients were at significantly greater risk of mortality compared with normal weight individuals.6 Unfortunately, body mass index does not reliably distinguish adipose tissue mass from muscle mass.7 Therefore, we sought to index patient size using CT measurements.2 The aim of the current study was to apply analytic morphomics in a cohort of allogeneic HCT patients and correlate with clinical outcomes.