Increased efficacy of dual proinflammatory cytokine blockade on acute GVHD while maintaining GVT effects.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a potential curative option for treating a variety of hematologic diseases, but acute and chronic graft-versus-host disease (GVHD) remain major barriers limiting efficacy. Acute gut GVHD occurs with marked increases in proinflammatory cytokines (including TNF and IL-6), which we recently demonstrated was exacerbated in obesity resulting in severe gastrointestinal pathology. Given the pleiotropic and overlapping effects of these 2 cytokines, we assessed the impact of dual TNF and IL-6R blockade on GVHD as well as graft-versus tumor (GVT) effects in different mouse GVHD models. Early administration of combined blockade resulted in greater protection and survival from acute gut GVHD compared with single blockade regimens and even development of later chronic skin GVHD. Importantly, double cytokine blockade preserved GVT effects reinforcing that GVT and GVHD can be delineated and may result in greater efficacy in allo-HSCT.

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.

Intratumoral CD4+ T Cells Mediate Anti-tumor Cytotoxicity in Human Bladder Cancer.

Responses to anti-PD-1 immunotherapy occur but are infrequent in bladder cancer. The specific T cells that mediate tumor rejection are unknown. T cells from human bladder tumors and non-malignant tissue were assessed with single-cell RNA and paired T cell receptor (TCR) sequencing of 30,604 T cells from 7 patients. We find that the states and repertoires of CD8+ T cells are not distinct in tumors compared with non-malignant tissues. In contrast, single-cell analysis of CD4+ T cells demonstrates several tumor-specific states, including multiple distinct states of regulatory T cells. Surprisingly, we also find multiple cytotoxic CD4+ T cell states that are clonally expanded. These CD4+ T cells can kill autologous tumors in an MHC class II-dependent fashion and are suppressed by regulatory T cells. Further, a gene signature of cytotoxic CD4+ T cells in tumors predicts a clinical response in 244 metastatic bladder cancer patients treated with anti-PD-L1.

Suppression of Exosomal PD-L1 Induces Systemic Anti-tumor Immunity and Memory.

PD-L1 on the surface of tumor cells binds its receptor PD-1 on effector T cells, thereby suppressing their activity. Antibody blockade of PD-L1 can activate an anti-tumor immune response leading to durable remissions in a subset of cancer patients. Here, we describe an alternative mechanism of PD-L1 activity involving its secretion in tumor-derived exosomes. Removal of exosomal PD-L1 inhibits tumor growth, even in models resistant to anti-PD-L1 antibodies. Exosomal PD-L1 from the tumor suppresses T cell activation in the draining lymph node. Systemically introduced exosomal PD-L1 rescues growth of tumors unable to secrete their own. Exposure to exosomal PD-L1-deficient tumor cells suppresses growth of wild-type tumor cells injected at a distant site, simultaneously or months later. Anti-PD-L1 antibodies work additively, not redundantly, with exosomal PD-L1 blockade to suppress tumor growth. Together, these findings show that exosomal PD-L1 represents an unexplored therapeutic target, which could overcome resistance to current antibody approaches.

Clonal Deletion of Tumor-Specific T Cells by Interferon-γ Confers Therapeutic Resistance to Combination Immune Checkpoint Blockade.

Resistance to checkpoint-blockade treatments is a challenge in the clinic. We found that although treatment with combined anti-CTLA-4 and anti-PD-1 improved control of established tumors, this combination compromised anti-tumor immunity in the low tumor burden (LTB) state in pre-clinical models as well as in melanoma patients. Activated tumor-specific T cells expressed higher amounts of interferon-γ (IFN-γ) receptor and were more susceptible to apoptosis than naive T cells. Combination treatment induced deletion of tumor-specific T cells and altered the T cell repertoire landscape, skewing the distribution of T cells toward lower-frequency clonotypes. Additionally, combination therapy induced higher IFN-γ production in the LTB state than in the high tumor burden (HTB) state on a per-cell basis, reflecting a less exhausted immune status in the LTB state. Thus, elevated IFN-γ secretion in the LTB state contributes to the development of an immune-intrinsic mechanism of resistance to combination checkpoint blockade, highlighting the importance of achieving the optimal magnitude of immune stimulation for successful combination immunotherapy strategies.

Tumor-conditional anti-CTLA4 uncouples antitumor efficacy from immunotherapy-related toxicity.

While immune checkpoint blockade leads to potent antitumor efficacy, it also leads to immune-related adverse events in cancer patients. These toxicities stem from systemic immune activation resulting in inflammation of multiple organs, including the gastrointestinal tract, lung, and endocrine organs. We developed a dual variable domain immunoglobulin of anti-CTLA4 antibody (anti-CTLA4 DVD, where CTLA4 is defined as cytotoxic T lymphocyte-associated antigen-4) possessing an outer tumor-specific antigen-binding site engineered to shield the inner anti-CTLA4-binding domain. Upon reaching the tumor, the outer domain was cleaved by membrane type-serine protease 1 (MT-SP1) present in the tumor microenvironment, leading to enhanced localization of CTLA4 blockade. Anti-CTLA4 DVD markedly reduced multiorgan immune toxicity by preserving tissue-resident Tregs in Rag 1-/- mice that received naive donor CD4+ T cells from WT C57BL/6j mice. Moreover, anti-CTLA4 DVD induced potent antitumor effects by decreasing tumor-infiltrating Tregs and increasing the infiltration of antigen-specific CD8+ T lymphocytes in TRAMP-C2-bearing C57BL/6j mice. Treg depletion was mediated through the antibody-dependent cellular cytotoxicity (ADCC) mechanism, as anti-CTLA4 without the FcγR-binding portion (anti-CTLA4 DANA) spared Tregs, preventing treatment-induced toxicities. In summary, our results demonstrate an approach to anti-CTLA4 blockade that depletes tumor-infiltrating, but not tissue-resident, Tregs, preserving antitumor effects while minimizing toxicity. Thus, our tumor-conditional anti-CTLA4 DVD provides an avenue for uncoupling antitumor efficacy from immunotherapy-induced toxicities.

Targeting EZH2 Reprograms Intratumoral Regulatory T Cells to Enhance Cancer Immunity.

Regulatory T cells (Tregs) are critical for maintaining immune homeostasis, but their presence in tumor tissues impairs anti-tumor immunity and portends poor prognoses in cancer patients. Here, we reveal a mechanism to selectively target and reprogram the function of tumor-infiltrating Tregs (TI-Tregs) by exploiting their dependency on the histone H3K27 methyltransferase enhancer of zeste homolog 2 (EZH2) in tumors. Disruption of EZH2 activity in Tregs, either pharmacologically or genetically, drove the acquisition of pro-inflammatory functions in TI-Tregs, remodeling the tumor microenvironment and enhancing the recruitment and function of CD8+ and CD4+ effector T cells that eliminate tumors. Moreover, abolishing EZH2 function in Tregs was mechanistically distinct from, more potent than, and less toxic than a generalized Treg depletion approach. This study reveals a strategy to target Tregs in cancer that mitigates autoimmunity by reprogramming their function in tumors to enhance anti-cancer immunity.

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.

Repeated PD-1/PD-L1 monoclonal antibody administration induces fatal xenogeneic hypersensitivity reactions in a murine model of breast cancer.

Monoclonal antibodies (mAbs) targeting coinhibitory molecules such as PD-1, PD-L1 and CTLA-4 are increasingly used as targets of therapeutic intervention against cancer. While these targets have led to a critical paradigm shift in treatments for cancer, these approaches are also plagued with limitations owing to cancer immune evasion mechanisms and adverse toxicities associated with continuous treatment. It has been difficult to reproduce and develop interventions to these limitations preclinically due to poor reagent efficacy and reagent xenogenecity not seen in human trials. In this study, we investigated adverse effects of repeated administration of PD-1 and PD-L1 mAbs in the murine 4T1 mammary carcinoma model. We observed rapid and fatal hypersensitivity reactions in tumor bearing mice within 30-60 min after 4-5 administrations of PD-L1 or PD-1 mAb but not CTLA-4 antibody treatment. These events occurred only in mice bearing the highly inflammatory 4T1 tumor and did not occur in mice bearing non-inflammatory tumors. We observed that mortality was associated with systemic accumulation of IgG1 antibodies, antibodies specific to the PD-1 mAb, and accumulation of Gr-1high neutrophils in lungs which have been implicated in the IgG mediated pathway of anaphylaxis. Anti-PD-1 associated toxicities were alleviated when PD-1 blockade was combined with the therapeutic HSP90 inhibitor, ganetespib, which impaired immune responses toward the xenogeneic PD-1 mAb. This study highlights a previously uncharacterized fatal hypersensitivity exacerbated by the PD-1/PD-L1 axis in the broadly used 4T1 tumor model as well as an interesting relationship between this particular class of checkpoint blockade and tumor-dependent immunomodulation.

Preclinical modeling of hematopoietic stem cell transplantation - advantages and limitations.

Hematopoietic stem cell transplantation, which was first successfully performed in the 1950s, remains a critical therapeutic modality for treatment of a diverse array of diseases, including a multitude of hematological malignancies, autoimmune disorders, amyloidosis and inherited genetic hematological disorders. Although great advances have been made in understanding and application of this therapy, significant complications still exist, warranting further investigation. Of critical importance, graft-versus-host disease (GVHD), in both acute and chronic forms, remains a major complication of hematopoietic stem cell transplantation, responsible for both the development of chronic illness and morbidity, as well as mortality. Use of an appropriate preclinical model may provide significant insight into the mechanistic pathways leading to the development and progression of graft-versus-host disease, as well as cancer in general. However, existing preclinical modeling systems exhibit significant limitations, and development of models that recapitulate the complex and comprehensive clinical scenario and provide a tool by which therapeutic intervention may be developed and assessed is of utmost importance. Here, we review the present status of the field of graft-versus-host disease research. We discuss and summarize the preclinical models currently in use, as well as their advantages and limitations.

Adiposity induces lethal cytokine storm after systemic administration of stimulatory immunotherapy regimens in aged mice.

Aging is a contributing factor in cancer occurrence. We recently demonstrated that systemic immunotherapy (IT) administration in aged, but not young, mice resulted in induction of rapid and lethal cytokine storm. We found that aging was accompanied by increases in visceral fat similar to that seen in young obese (ob/ob or diet-induced obese [DIO]) mice. Yet, the effects of aging and obesity on inflammatory responses to immunotherapeutics are not well defined. We determine the effects of adiposity on systemic IT tolerance in aged compared with young obese mice. Both young ob/ob- and DIO-generated proinflammatory cytokine levels and organ pathologies are comparable to those in aged ad libitum mice after IT, culminating in lethality. Young obese mice exhibited greater ratios of M1/M2 macrophages within the peritoneal and visceral adipose tissues and higher percentages of TNF(+) macrophages in response to αCD40/IL-2 as compared with young lean mice. Macrophage depletion or TNF blockade in conjunction with αCD40/IL-2 prevented cytokine storms in young obese mice and protected from lethality. Calorie-restricted aged mice contain less visceral fat and displayed reduced cytokine levels, protection from organ pathology, and protection from lethality upon αCD40/IL-2 administration. Our data demonstrate that adiposity is a critical factor in the age-associated pathological responses to systemic anti-cancer IT.

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.

IFN-γ receptor-deficient donor T cells mediate protection from graft-versus-host disease and preserve graft-versus-tumor responses after allogeneic bone marrow transplantation.

Graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. It has been previously reported that lung GVHD severity directly correlates with the expansion of donor Th17 cells in the absence of IFN-γ. However, the consequence of Th17-associated lung GVHD in the presence of IFN-γ has not been well characterized. In the current study, T cells from IFN-γ receptor knockout (IFN-γR(-/-)) mice, capable of producing IFN-γ but unable to signal in response to IFN-γ, have been used to elucidate further the role of IFN-γ in GVHD. We found the transfer of donor T cells from either IFN-γR(-/-) or IFN-γ knockout (IFN-γ(-/-)) mice resulted in significant increases in donor Th17 cells in the lung. Marked increases in IL-4-producing Th2 cells infiltrating the lungs were also observed in the mice of donor IFN-γR(-/-) T cells. Notably, despite the presence of these cells, these mice did not show the severe immune-mediated histopathological lung injury observed in mice receiving donor IFN-γ(-/-) T cells. Increases in lung GVHD did occur in mice with donor IFN-γR(-/-) T cells when treated in vivo with anti-IFN-γ demonstrating that the cytokine has a protective role on host tissues in GVHD. A survival benefit from acute GVHD was also observed using donor cells from IFN-γR(-/-) T cells compared with control donors. Importantly, tumor-bearing mice receiving IFN-γR(-/-) T cells versus wild-type donor T cells displayed similar graft-versus-tumor (GVT) effects. These results demonstrate the critical role of IFN-γ on host tissues and cell effector functions in GVHD/GVT.

Immunopathogenic behaviors of canine transmissible venereal tumor in dogs following an immunotherapy using dendritic/tumor cell hybrid.

Canine transmissible venereal tumor (CTVT) is a naturally occurring tumor that can be transmitted between dogs via live tumor cell inoculation. It is also a spontaneous self-regression tumor and its behavior is closely related to host immune responses. Since CTVT had been widely used for tumor models in canine cancers, whether this self-regression may overtake the immunity elicited from an exogenous tumor vaccine remains unclear and certainly worthwhile to be investigated. In this study, we used DCs/tumor hybrids as a tumor vaccine to evaluate the CTVT model. We prepared mature allogeneic dendritic cells from bone marrow and then assessed their phenotype (CD80, CD83, CD86, CD1a, CD11c, CD40 and MHC II), antigen uptake and presenting abilities. Fused dendritic cell/CTVT hybrids were then used as a vaccine, administered three times at two-week intervals via subcutaneous injection near the bilateral auxiliary and inguinal lymph nodes. In comparison with unvaccinated dogs (spontaneous regressed group), within a period of 2.5 months, the vaccinations substantially inhibited tumor progression (p<0.05) and accelerated the rate of regression by a mechanism involving amplification of the host tumor-specific adaptive immune responses and NK cytotoxicity (p<0.001). Pathologic examination revealed early massive lymphocyte infiltration resulting in final tumor necrosis. In addition, there are not any detectable effects on routine physical, body temperature or blood chemistry examinations. In conclusion, our data furnishes a reference value showing that CTVT is a model of potential use for the study of immunity elicited by vaccines against tumors, and also enable early-phase evaluation of the dendritic cell/tumor vaccine in terms of raising host immunity.

Combined immunogene therapy of IL-6 and IL-15 enhances anti-tumor activity through augmented NK cytotoxicity.

Many tumors evade host immunity by lowering expression of major histocompatibility complex (MHC) molecules. Theoretically, low MHC expression should activate natural killer (NK) cells and in some cases suppress tumor growth; nevertheless, some tumors also produce high concentrations of immunosuppressive cytokines, such as transforming growth factor (TGF)-beta, to inhibit the activity of NK cells. Using a canine transmissible venereal tumor (CTVT) model, we have previously demonstrated that IL-6 is a strong antagonist for TGF-beta. Herein, we found that IL-6 alone was unable to significantly promote TGF-beta-inhibited NK activities. Conversely, IL-15 alone strongly promoted NK activities; however, NK activities were inhibited to baseline levels following the addition of TGF-beta. Therefore, a new strategy using combined immunogene therapy of both IL-6 and IL-15 mediated by electroporation was used in this study. This combined IL-6 and IL-15 treatment effectively relieved the inhibitory effect of TGF-beta and activated NK cell cytotoxicity of lymphokine-activated killer (LAK) cells. Similarly, in isolated DX5+ NK cells, only IL-6 and IL-15 in combination significantly overcame the inhibitory effect of TGF-beta and promoted NK cytotoxicity. The group of BALB/c mice injected with plasmids with IL-6 and IL-15 genes (pIL-6/pIL-15) had the highest percentages of DX5+ NK cells as compared with either the pIL-6 or pIL-15 groups. Further, in SCID mice inoculated with CTVT, electroporation-mediated delivery of pIL-6/pIL-15 was significantly more efficient in suppressing both tumor establishment and tumor growth as compared with pIL-6 or pIL-15 inoculation alone. In addition, the anti-asialo GM-1 antibody abolished NK activities in SCID mice and resulted in outgrowth of the tumors. Together, these results suggest that the TGF-beta-associated inhibition of NK cytotoxicity cannot be adequately restored by simply antagonizing TGF-beta with IL-6: the co-existence of NK activating factors such as IL-15 is also important in restoring TGF-beta-inhibited cytotoxicity. This study highlights the therapeutic potential of the pIL-6/pIL-15 combination by inhibiting TGF-beta activity and enhancing NK cytotoxicity.