Synergistic anti-tumor responses after administration of agonistic antibodies to CD40 and IL-2: coordination of dendritic and CD8+ cell responses

Development and validation of an immune-related gene signature for prognosis in Lung adenocarcinoma

The most common type of lung cancer tissue is lung adenocarcinoma. The TCGA-LUAD cohort retrieved from the TCGA dataset was considered the internal training cohort, while GSE68465 and GSE13213 datasets from the GEO database were used as the external test cohort. The TCGA-LUAD cohort was classified into two immune subtypes using single-sample gene set enrichment analysis of the immune gene set and unsupervised clustering analysis. The ESTIMATE algorithm, the CIBERSORT algorithm, and HLA family expression levels again validated the reliability of this typing. We performed Venn analysis using immune-related genes from the immport dataset and differentially expressed genes from the subtypes to retrieve differentially expressed immune genes (DEIGs). In addition, DEIGs were used to construct a prognostic model with the least absolute shrinkage and selection operator regression analysis. A reliable risk model consisting of 11 DEIGs, including S100P, INHA, SEMA7A, INSL4, CD40LG, AGER, SERPIND1, CD1D, CX3CR1, SFTPD, and CD79A, was then built, and its reliability was further confirmed by ROC curve and calibration plot analysis. The high-risk score subgroup had a poor prognosis and a lower tumour immune dysfunction and exclusion score, indicating a greater likelihood of anti-PD-1/cytotoxic T lymphocyte antigen 4 benefit.

A Bayesian network meta-analysis of comparison of cancer therapeutic vaccines for melanoma

Several approaches to active immunotherapy for melanoma, including peptide-based vaccines (PVs), autologous tumour cell vaccines (TCVs), allogeneic TCVs and autologous dendritic cell vaccines (DCVs), have been investigated in clinical trials. However, comprehensive evidence comparing these interventions remains unavailable. The objective of this study was to expand previous work to compare and rank the immunotherapeutic strategies for melanoma in terms of overall survival and toxic effects with a Bayesian network meta-analysis. Methodologically, we performed a network meta-analysis of head-to-head randomized controlled trials comparing and ranking cancer vaccine approaches for patients with melanoma. PubMed, MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, the WHO International Clinical Trials Registry Platform and ClinicalTrials.gov were searched up to 31 July 2020. We estimated summary hazard ratios for death and risk ratios for toxicity. The effects of the underlying prognostic variable on survival benefits were examined by meta-regression. We performed subgroup analysis for the outcomes based on metastatic categories. Overall, we identified 4776 citations, of which 15 head-to-head randomized controlled trials (3162 participants) were included in the analysis. In terms of efficacy, allogeneic tumour cell vaccines plus immunotherapy adjuvants, peptide-based vaccines plus immunotherapy adjuvants and standard therapy were more effective than peptide vaccines. The proportion of women was inversely associated with mortality risk. For safety, all treatments were inferior to allogeneic tumour cell vaccines except for allogeneic tumour cell vaccines plus chemotherapy. Peptide vaccines plus immunotherapy adjuvants led to an increased risk of adverse events compared to allogeneic tumour cell vaccines plus immunotherapy adjuvants. These results suggest that allogeneic TCV and autologous DCV are better than standard therapy. PV plus immune modulators are the most effective strategy among all comparable strategies but is associated with increased toxicity. Any combination regimens for cancer therapeutic vaccines need to be balanced between risk and benefit profiles.

Rationale and clinical development of CD40 agonistic antibodies for cancer immunotherapy

Introduction: CD40 signaling activates dendritic cells leading to improved T cell priming against tumor antigens. CD40 agonism expands the tumor-specific T cell repertoire and has the potential to increase the fraction of patients that respond to established immunotherapies.Areas covered: This article reviews current as well as emerging CD40 agonist therapies with a focus on antibody-based therapies, including next generation bispecific CD40 agonists. The scientific rationale for different design criteria, binding epitopes, and formats are discussed.Expert opinion: The ability of CD40 agonists to activate dendritic cells and enhance antigen cross-presentation to CD8⁺ T cells provides an opportunity to elevate response rates of cancer immunotherapies. While there are many challenges left to address, including optimal dose regimen, CD40 agonist profile, combination partners and indications, we are confident that CD40 agonists will play an important role in the challenging task of reprogramming the immune system to fight cancer.

CD40 Agonist Targeted to Fibroblast Activation Protein α Synergizes with Radiotherapy in Murine HPV-Positive Head and Neck Tumors

PURPOSE

The incidence of human papillomavirus-associated head and neck squamous cell carcinoma (HPV⁺-HNSCC) is rising worldwide and although current therapeutic modalities are efficient in the majority of patients, there is a high rate of treatment failures. Thus, novel combination approaches are urgently needed to achieve better disease control in patients with HPV⁺-HNSCC. We investigated the safety and therapeutic efficacy of a novel fibroblast activation protein (FAP)-targeted CD40 agonist (FAP-CD40) in combination with local hypofractionated radiation in a syngeneic HPV⁺-HNSCC model.

EXPERIMENTAL DESIGN

Using an established orthotopic model, we treated tumor-bearing mice with local hypofractionated radiotherapy (2 × 6 Gy) alone or in combination with a systemic administration of the FAP-CD40 antibody. Following up the mice, we evaluated the changes in the tumor microenvironment (TME) by immunofluorescence, FACS, and NanoString RNA analysis.

RESULTS

The suboptimal radiotherapy regimen chosen failed to control tumors in the treated mice. The FAP-CD40 administered in monotherapy transiently controlled tumor growth, whereas the combined therapy induced durable complete responses in more than 80% of the tumor-bearing mice. This notable efficacy relied on the radiotherapy-induced remodeling of the TME and activation of the CD8⁺ T-cell-cDC1 axis and was devoid of the systemic toxicity frequently associated with CD40-targeted therapy. Moreover, the robust immunologic memory developed effectively prevented tumor relapses, a common feature in patients with HNSCC.

CONCLUSIONS

Our study provides proof of concept, as well as mechanistic insights of the therapeutic efficacy of a bispecific FAP-CD40 combined with local radiotherapy in a FAP⁺-HNSCC model increasing overall survival and inducing long-term antitumor immunity.

Neoadjuvant vascular-targeted photodynamic therapy improves survival and reduces recurrence and progression in a mouse model of urothelial cancer

Locally advanced urothelial cancer has high recurrence and progression rates following surgical treatment. This highlights the need to develop neoadjuvant strategies that are both effective and well-tolerated. We hypothesized that neoadjuvant sub-ablative vascular-targeted photodynamic therapy (sbVTP), through its immunotherapeutic mechanism, would improve survival and reduce recurrence and progression in a murine model of urothelial cancer. After urothelial tumor implantation and 17 days before surgical resection, mice received neoadjuvant sbVTP (WST11; Tookad Soluble, Steba Biotech, France). Local and systemic response and survival served as measures of therapeutic efficacy, while immunohistochemistry and flow cytometry elucidated the immunotherapeutic mechanism. Data analysis included two-sided Kaplan-Meier, Mann-Whitney, and Fischer exact tests. Tumor volume was significantly smaller in sbVTP-treated animals than in controls (135 mm3 vs. 1222 mm3, P < 0.0001) on the day of surgery. Systemic progression was significantly lower in sbVTP-treated animals (l7% vs. 30%, P < 0.01). Both median progression-free survival and overall survival were significantly greater among animals that received sbVTP and surgery than among animals that received surgery alone (P < 0.05). Neoadjuvant-treated animals also demonstrated significantly lower local recurrence. Neoadjuvant sbVTP was associated with increased early antigen-presenting cells, and subsequent improvements in long-term memory and increases in effector and active T-cells in the spleen, lungs, and blood. In summary, neoadjuvant sbVTP delayed local and systemic progression, prolonged progression-free and overall survival, and reduced local recurrence, thereby demonstrating therapeutic efficacy through an immune-mediated response. These findings strongly support its evaluation in clinical trials.

Molecular and metabolic pathways mediating curative treatment of a non-Hodgkin B cell lymphoma by Sindbis viral vectors and anti-4-1BB monoclonal antibody

Background

Limitations to current therapies for treating non-Hodgkin B cell lymphoma include relapse, toxicity and high cost. Thus, there remains a need for novel therapies. Oncolytic viral (OV) therapy has become a promising cancer immunotherapy because of its potential effectiveness, specificity and long-lasting immunity. We describe and characterize a novel cancer immunotherapy combining Sindbis virus (SV) vectors and the agonistic monoclonal antibody (mAb) to the T cell costimulatory receptor, 4-1BB (CD137).

Methods

A20 lymphoma was transfected with luciferase and tumor cells were inoculated to BALB/c mice. Tumor growth was monitored by IVIS imaging. Tumor bearing mice were treated with Sindbis virus, α4-1BB Ab or SV plus α4-1BB Ab. On day 7 after treatment, splenocytes were harvested and surface markers, cytokines, and transcription factors were measured by flow cytometry or Elispot. Splenic T cells were isolated and RNA transcriptome analysis was performed. Tumor cured mice were rechallenged with tumor for testing immunological memory.

Results

SV vectors in combination with α4-1BB monoclonal antibody (mAb) completely eradicated a B-cell lymphoma in a preclinical mouse model, a result that could not be achieved with either treatment alone. Tumor elimination involves a synergistic effect of the combination that significantly boosts T cell cytotoxicity, IFNγ production, T cell proliferation, migration, and glycolysis. In addition, all mice that survived after treatment developed long lasting antitumor immunity, as shown by the rejection of A20 tumor rechallenge. We identified the molecular pathways, including upregulated cytokines, chemokines and metabolic pathways in T cells that are triggered by the combined therapy and help to achieve a highly effective anti-tumor response.

Conclusions

Our study provides a novel, alternative method for B cell lymphoma treatment and describes a rationale to help translate SV vectors plus agonistic mAb into clinical applications.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0664-3) contains supplementary material, which is available to authorized users.

The influence of the microbiota on immune development, chronic inflammation, and cancer in the context of aging

From birth, the microbiota plays an essential role in human development by educating host immune responses. Proper maturation of the immune system perturbs chronic inflammation and the pathogenesis of disease by preventing inappropriate immune responses. While many have detailed the roles of specific microbial groups in immune development and human disease, it remains to be elucidated how the microbiota influences the immune system during aging. Furthermore, it is not yet understood how age-related changes to the microbiota and immune system influence the development of age-related diseases. In this review, we outline the role of the microbiota in immune system development as well as functional changes that occur to immune cell populations during immunosenescence. In addition, we highlight how commensal microbes influence the pathogenesis of cancer, a prominent disease of aging. The information provided herein suggests that age-related changes to the microbiota and immune system should be considered in disease treatment and prevention strategies.

OMIC signatures to understand cancer immunosurveillance and immunoediting: Melanoma and immune cells interplay in immunotherapy

Melanoma is the deadliest form of skin cancer. Cutaneous melanomas usually originate from exposure to the mutagenic effects of ultraviolet radiation, and as such they exhibit the highest rate of somatic mutations than any other human cancer, and an extensive expression of neoantigens concurrently with a dense infiltrate of immune cells. The coexistence of high immunogenicity and high immune cell infiltration may sound contradictory for cancers carrying a gloomy outcome. However, recent studies have unveiled a variety of immunosuppressive mechanisms that often permeate the tumor microenvironment and that are responsible for tumor escaping from immunosurveillance mechanisms. Nonetheless, this particular immune profile has opened a new window of treatments based on immunotherapy that have significantly improved the clinical outcome of melanoma patients. Still, positive and complete therapy responses have been limited, and this particular cancer continues to be a major clinical challenge. The transcriptomic signatures of those patients with clinical benefit and those with progressive disease have provided a more complete picture of the universe of interactions between the tumor and the immune system. In this review, we integrate the results of the immunotherapy clinical trials to discuss a novel understanding of the mechanisms guiding cancer immunosurveillance and immunoediting. A clear notion of the cellular and molecular processes shaping how the immune system and the tumor are continuously coevolving would result in the rational design of combinatory therapies aiming to counteract the signaling pathways and cellular processes responsible for immunoescape mechanisms and provide clinical benefit to immunotherapy nonresponsive patients.

The Regulatory Status Adopted by Lymph Node Dendritic Cells and T Cells During Healthy Aging Is Maintained During Cancer and May Contribute to Reduced Responses to Immunotherapy

Aging is associated with an increased incidence of cancer. One contributing factor could be modulation of immune cells responsible for anti-tumor responses, such as dendritic cells (DCs) and T cells. These immunological changes may also impact the efficacy of cancer immunotherapies in the elderly. The effects of healthy aging on DCs and T cells, and their impact on anti-mesothelioma immune responses, had not been reported. This study examined DCs and T cells in young (2–5 months; equivalent to 16–26 human years) and elderly (20–24 months; equivalent to 60–70 human years) healthy and mesothelioma-bearing C57BL/6J mice. During healthy aging, elderly lymph nodes adopted a regulatory profile, characterized by: (i) increased plasmacytoid DCs, (ii) increased expression of the adenosine-producing enzyme CD73 on CD11c⁺ cells, and (iii) increased expression of multiple regulatory markers (including CD73, the adenosine A2B receptor, CTLA-4, PD-1, ICOS, LAG-3, and IL-10) on CD8⁺ and CD4⁺ T cells, compared to lymph nodes from young mice. Although mesotheliomas grew faster in elderly mice, the increased regulatory status observed in healthy elderly lymph node DCs and T cells was not further exacerbated. However, elderly tumor-bearing mice demonstrated reduced MHC-I, MHC-II and CD80 on CD11c⁺ cells, and decreased IFN-γ by CD8⁺ and CD4⁺ T cells within tumors, compared to young counterparts, implying loss of function. An agonist CD40 antibody based immunotherapy was less efficient at promoting tumor regression in elderly mice, which may be due to: (i) failure of elderly CD8⁺ T cells to up-regulate perforin, and (ii) increased expression of multiple regulatory markers on CD11c⁺ cells and T cells in elderly tumor-draining lymph nodes (including CD73, PD-1, ICOS, LAG-3, and TGF-β). Our findings suggest that checkpoint blockade may improve responses to immunotherapy in elderly hosts with mesothelioma, and warrants further investigation.

Overcoming Barriers of Age to Enhance Efficacy of Cancer Immunotherapy: The Clout of the Extracellular Matrix

There is a growing list of cancer immunotherapeutics approved for use in a population with an increasing number of aged individuals. Cancer immunotherapy (CIT) mediates tumor destruction by activating anti-tumor immune responses that have been silenced through the oncogenic process. However, in an aging individual, immune deregulation is positively correlated with age. In this context, it is vital to examine the age-related changes in the tumor microenvironment (TME) and specifically, those directly affecting critical players to ensure CIT efficacy. Effector T cells, regulatory T cells, myeloid-derived suppressor cells, tumor-associated macrophages, and tumor-associated neutrophils play important roles in promoting or inhibiting the inflammatory response, while cancer-associated fibroblasts are key mediators of the extracellular matrix (ECM). Immune checkpoint inhibitors function optimally in inflamed tumors heavily invaded by CD4 and CD8 T cells. However, immunosenescence curtails the effector T cell response within the TME and causes ECM deregulation, creating a biophysical barrier impeding both effective drug delivery and pro-inflammatory responses. The ability of the chimeric antigen receptor T (CAR-T) cell to artificially induce an adaptive immune response can be modified to degrade essential components of the ECM and alleviate the age-related changes to the TME. This review will focus on the age-related alterations in ECM and immune-stroma interactions within the TME. We will discuss strategies to overcome the barriers of immunosenescence and matrix deregulation to ameliorate the efficacy of CIT in aged subjects.

A pilot study of the immunogenicity of a 9-peptide breast cancer vaccine plus poly-ICLC in early stage breast cancer

BACKGROUND

Breast cancer remains a leading cause of cancer death worldwide. There is evidence that immunotherapy may play a role in the eradication of residual disease. Peptide vaccines for immunotherapy are capable of durable immune memory, but vaccines alone have shown sparse clinical activity against breast cancer to date. Toll-like receptor (TLR) agonists and helper peptides are excellent adjuvants for vaccine immunotherapy and they are examined in this human clinical trial.

METHODS

A vaccine consisting of 9 MHC class I-restricted breast cancer-associated peptides (from MAGE-A1, -A3, and -A10, CEA, NY-ESO-1, and HER2 proteins) was combined with a TLR3 agonist, poly-ICLC, along with a helper peptide derived from tetanus toxoid. The vaccine was administered on days 1, 8, 15, 36, 57, 78. CD8⁺ T cell responses to the vaccine were assessed by both direct and stimulated interferon gamma ELIspot assays.

RESULTS

Twelve patients with breast cancer were treated: five had estrogen receptor positive disease and five were HER2 amplified. There were no dose-limiting toxicities. Toxicities were limited to Grade 1 and Grade 2 and included mild injection site reactions and flu-like symptoms, which occurred in most patients. The most common toxicities were injection site reaction/induration and fatigue, which were experienced by 100% and 92% of participants, respectively. In the stimulated ELIspot assays, peptide-specific CD8⁺ T cell responses were detected in 4 of 11 evaluable patients. Two patients had borderline immune responses to the vaccine. The two peptides derived from CEA were immunogenic. No difference in immune response was evident between patients receiving endocrine therapy and those not receiving endocrine therapy during the vaccine series.

CONCLUSIONS

Peptide vaccine administered in the adjuvant breast cancer setting was safe and feasible. The TLR3 adjuvant, poly-ICLC, plus helper peptide mixture provided modest immune stimulation. Further optimization is required for this multi-peptide vaccine/adjuvant combination.

TRIAL REGISTRATION

ClinicalTrials.gov (posted 2/15/2012): NCT01532960. Registered 2/8/2012. https://clinicaltrials.gov/show/NCT01532960.

Combination of CD40 Agonism and CSF-1R Blockade Reconditions Tumor-Associated Macrophages and Drives Potent Antitumor Immunity

Efficacious antitumor immune responses must overcome multiple suppressive mechanisms in the tumor microenvironment to control cancer progression. In this study, we demonstrate that dual targeting of suppressive myeloid populations by inhibiting CSF-1/CSF-1R signaling and activation of antigen-presenting cells with agonist anti-CD40 treatment confers superior antitumor efficacy and increased survival compared with monotherapy treatment in preclinical tumor models. Concurrent CSF-1R blockade and CD40 agonism lead to profound changes in the composition of immune infiltrates, causing an overall decrease in immunosuppressive cells and a shift toward a more inflammatory milieu. Anti-CD40/anti-CSF-1R-treated tumors contain decreased tumor-associated macrophages and Foxp3⁺ regulatory T cells. This combination approach increases maturation and differentiation of proinflammatory macrophages and dendritic cells and also drives potent priming of effector T cells in draining lymph nodes. As a result, tumor-infiltrating effector T cells exhibit improved responses to tumor antigen rechallenge. These studies show that combining therapeutic approaches may simultaneously remove inhibitory immune populations and sustain endogenous antitumor immune responses to successfully impair cancer progression. Cancer Immunol Res; 5(12); 1109-21. ©2017 AACR.

Differential phenotypes of memory CD4 and CD8 T cells in the spleen and peripheral tissues following immunostimulatory therapy

Background

Studies assessing immune parameters typically utilize human PBMCs or murine splenocytes to generate data that is interpreted as representative of immune status. Using splenocytes, we have shown memory CD4-T cells that expand following systemic immunostimulatory therapies undergo rapid IFNg-mediated activation induced cell death (AICD) resulting in a net loss of total CD4-T cells which correlates with elevated PD-1 expression. This is in contrast to CD8-T cells which expand with minimal PD-1 upregulation and apoptosis. In this study we expand upon our previous work by evaluating CD4 and CD8-T cell phenotype and distribution in peripheral organs which are more representative of immune responses occurring at metastatic sites following immunotherapy.

Methods

Phenotypic assessment of T cells in both lymphoid (spleen and LN) as well as peripheral organs (liver and lungs) in control and immunotherapy treated mice was performed to survey the impact of location on memory phenotype and activation marker status. Peripheral blood from patients undergoing systemic high dose IL-2 was also assessed for expression of PD-1 and memory phenotype.

Results

Here we reveal that, similar to what occurs in the spleen and lymph nodes, CD4-T cell numbers decreased while CD8-T cells expanded at these peripheral sites. In contrast to having differential expression of PD-1 as occurs in the spleen, both CD4 and CD8-T cells had significantly elevated levels of PD-1 in both the liver and lungs. Further analysis correlated PD-1 expression to CD62L^low (T effector/effector memory,T_E/EM) expression which are more prevalent in CD4-T cells in general as well as CD8-T cells in peripheral organs. Similar elevated PD-1 expression on T_E/EM cells was observed in patients undergoing systemic high-dose IL-2 therapy.

Conclusions

These data highlight PD-1 expressing and/or T_E/EM subsets of T cells in circulation as more representative of cells at immune sites and underscore the importance of valuation both in lymphoid as well as target organs when making determinations about immune status.

Trial registration

ClinicalTrials.gov NCT01416831. Registered August 12, 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0235-4) contains supplementary material, which is available to authorized users.

Diacylglycerol Kinase ζ Limits Cytokine-dependent Expansion of CD8+ T Cells with Broad Antitumor Capacity

Interleukin-2 and -15 drive expansion/differentiation of cytotoxic CD8⁺ T cells that eliminate targets via antigen-independent killing. This property is clinically relevant for the improvement of T cell-based antitumor therapies. Diacylglycerol kinase α and ζ (DGKα/ζ) metabolize the diacylglycerol generated following antigen recognition by T lymphocytes. Enhanced expression of these two lipid kinases in tumor-infiltrating CD8⁺ T cells promotes a hyporesponsive state that contributes to tumor immune escape. Inhibition of these two enzymes might thus be of interest for potentiating conventional antigen-directed tumor elimination. In this study, we sought to characterize the contribution of DGKα and ζ to antigen-independent cytotoxic functions of CD8⁺ T cells. Analysis of DGKζ-deficient mice showed an increase in bystander memory-like CD8⁺ T cell populations not observed in DGKα-deficient mice. We demonstrate that DGKζ limits cytokine responses in an antigen-independent manner. Cytokine-specific expansion of DGKζ-deficient CD8⁺ T cells promoted enhanced differentiation of innate-like cytotoxic cells in vitro, and correlated with the more potent in vivo anti-tumor responses of DGKζ-deficient mice engrafted with the murine A20 lymphoma. Our studies reveal a isoform-specific function for DGKζ downstream of IL-2/IL-15-mediated expansion of innate-like cytotoxic T cells, Pharmacological manipulation of DGKζ activity is of therapeutic interest for cytokine-directed anti-tumor treatments.

•

DGKζ, a well-characterized negative regulator of TCR signals, also limits IL-2/15 function.

•

DGKζ impairs cytokine-induced differentiation of cytotoxic T cell populations with innate-like ability to kill targets.

•

As a result, DGKζ-deficient mice demonstrate enhanced rejection of implanted B cell lymphoma compared to wild type mice.

•

Targeting DGKζ activity might be of interest to enhance cytokine-mediated antitumor therapies.

The immune system defends the body from foreign invaders. In cancer, tumors disguise as self-body cells and evade immune attack. For this reason it is important to identify the mechanism that stop T lymphocytes from recognize and destroy tumors. In this study we investigate the role of Diacylglycerol kinase zeta (DGKζ) as an inhibitor of antitumor T cell functions. We demonstrate that lymphoma cells injected in mice genetically modified to lack DGKζ expression develop smaller tumors that resolve more rapidly than those grown in normal mice. Our studies suggest that inhibition of DGKζ could help to reinforce the antitumor capacity of immune T lymphocytes.

Combination immunotherapy: a road map

Cancer immunotherapy and in particular monoclonal antibodies blocking the inhibitory programed cell death 1 pathway (PD-1/PD-L1) have made a significant impact on the treatment of cancer patients in recent years. However, despite the remarkable clinical efficacy of these agents in a number of malignancies, it has become clear that they are not sufficiently active for many patients. Initial evidence, for example with combined inhibition of PD-1 and CTLA-4 in melanoma and non-small cell lung cancer (NSCLC), has highlighted the potential to further enhance the clinical benefits of monotherapies by combining agents with synergistic mechanisms of action. In order to address the current progress and consider challenges associated with these novel approaches, the Society for Immunotherapy of Cancer (SITC) convened a Combination Immunotherapy Task Force. This Task Force was charged with identifying and prioritizing the most promising prospects for combinatorial approaches as well as addressing the challenges associated with developing these strategies. As a result of the extensive clinical benefit and tolerable side effects demonstrated with agents inhibiting the PD-1 pathway, an overview of current evidence to support its promising potential for use as a backbone in combination strategies is presented. In addition, key issues in the development of these strategies including preclinical modeling, patient safety and toxicity considerations, clinical trial design, and endpoints are also discussed. Overall, the goal of this manuscript is to provide a summary of the current status and potential challenges associated with the development and clinical implementation of these strategies.

Cancer immunotherapy: activating innate and adaptive immunity through CD40 agonists

INTRODUCTION

CD40 is a promising therapeutic target for cancer immunotherapy. In patients with advanced solid malignancies, CD40 agonists have demonstrated some anti-tumor activity and a manageable toxicity profile. A 2^nd generation of CD40 agonists has now been designed with optimized Fc receptor (FcR) binding based on preclinical evidence suggesting a critical role for FcR engagement in defining the potency of CD40 agonists in vivo. Areas covered: We provide a comprehensive review using PubMed and Google Patent databases on the current clinical status of CD40 agonists, strategies for applying CD40 agonists in cancer therapy, and the preclinical data that supports and is guiding the future development of CD40 agonists. Expert commentary: There is a wealth of preclinical data that provide rationale on several distinct approaches for using CD40 agonists in cancer immunotherapy. This data illustrates the need to strategically combine CD40 agonists with other clinically active treatment regimens in order to realize the full potential of activating CD40 in vivo. Thus, critical to the success of this class of immune-oncology drugs, which have the potential to restore both innate and adaptive immunosurveillance, will be the identification of biomarkers for monitoring and predicting responses as well as informing mechanisms of treatment resistance.

Adapting Cancer Immunotherapy Models for the Real World

Early experiments in mice predicted the success of checkpoint blockade immunotherapy in cancer patients. However, these same animal studies failed to accurately predict many of the limitations and toxicities of treatment. One of the likely reasons for this discrepancy is the nearly universal use of young healthy mice, which stand in stark contrast to diverse patient populations varying in age, weight, diet, and hygiene. Because these variables impact immunity and metabolism, they also influence outcomes during immunotherapy and should be incorporated into the study design of preclinical experiments. Here, we discuss recent findings that highlight how efficacy and toxicity of cancer immunotherapy are affected by patient variation, and how distinct host environments can be better modeled in animal studies.

Blocking Indolamine-2,3-Dioxygenase Rebound Immune Suppression Boosts Antitumor Effects of Radio-Immunotherapy in Murine Models and Spontaneous Canine Malignancies

PURPOSE

Previous studies demonstrate that intratumoral CpG immunotherapy in combination with radiotherapy acts as an in-situ vaccine inducing antitumor immune responses capable of eradicating systemic disease. Unfortunately, most patients fail to respond. We hypothesized that immunotherapy can paradoxically upregulate immunosuppressive pathways, a phenomenon we term "rebound immune suppression," limiting clinical responses. We further hypothesized that the immunosuppressive enzyme indolamine-2,3-dioxygenase (IDO) is a mechanism of rebound immune suppression and that IDO blockade would improve immunotherapy efficacy.

EXPERIMENTAL DESIGN

We examined the efficacy and immunologic effects of a novel triple therapy consisting of local radiotherapy, intratumoral CpG, and systemic IDO blockade in murine models and a pilot canine clinical trial.

RESULTS

In murine models, we observed marked increase in intratumoral IDO expression after treatment with radiotherapy, CpG, or other immunotherapies. The addition of IDO blockade to radiotherapy + CpG decreased IDO activity, reduced tumor growth, and reduced immunosuppressive factors, such as regulatory T cells in the tumor microenvironment. This triple combination induced systemic antitumor effects, decreasing metastases, and improving survival in a CD8(+) T-cell-dependent manner. We evaluated this novel triple therapy in a canine clinical trial, because spontaneous canine malignancies closely reflect human cancer. Mirroring our mouse studies, the therapy was well tolerated, reduced intratumoral immunosuppression, and induced robust systemic antitumor effects.

CONCLUSIONS

These results suggest that IDO maintains immune suppression in the tumor after therapy, and IDO blockade promotes a local antitumor immune response with systemic consequences. The efficacy and limited toxicity of this strategy are attractive for clinical translation. Clin Cancer Res; 22(17); 4328-40. ©2016 AACR.

Late administration of murine CTLA-4 blockade prolongs CD8-mediated anti-tumor effects following stimulatory cancer immunotherapy

We have demonstrated that immunostimulatory therapies such as interleukin-2 (IL-2) and anti-CD40 (αCD40) can be combined to deliver synergistic anti-tumor effects. While this strategy has shown success, efficacy varies depending on a number of factors including tumor type and severe toxicities can be seen. We sought to determine whether blockade of negative regulators such as cytotoxic T lymphocyte antigen-4 (CTLA-4) could simultaneously prolong CD8(+) T cell responses and augment T cell anti-tumor effects. We devised a regimen in which anti-CTLA-4 was administered late so as to delay contraction and minimize toxicities. This late administration both enhanced and prolonged CD8 T cell activation without the need for additional IL-2. The quality of the T cell response was improved with increased frequency of effector/effector memory phenotype cells along with improved lytic ability and bystander expansion. This enhanced CD8 response translated to improved anti-tumor responses both at the primary and metastatic sites. Importantly, toxicities were not exacerbated with combination. This study provides a platform for rational design of immunotherapy combinations to maximize anti-tumor immunity while minimizing toxicities.

Out-of-Sequence Signal 3 Paralyzes Primary CD4(+) T-Cell-Dependent Immunity

Primary T cell activation involves the integration of three distinct signals delivered in sequence: (1) antigen recognition, (2) costimulation, and (3) cytokine-mediated differentiation and expansion. Strong immunostimulatory events such as immunotherapy or infection induce profound cytokine release causing "bystander" T cell activation, thereby increasing the potential for autoreactivity and need for control. We show that during strong stimulation, a profound suppression of primary CD4(+) T-cell-mediated immune responses ensued and was observed across preclinical models and patients undergoing high-dose interleukin-2 (IL-2) therapy. This suppression targeted naive CD4(+) but not CD8(+) T cells and was mediated through transient suppressor of cytokine signaling-3 (SOCS3) inhibition of the STAT5b transcription factor signaling pathway. These events resulted in complete paralysis of primary CD4(+) T cell activation, affecting memory generation and induction of autoimmunity as well as impaired viral clearance. These data highlight the critical regulation of naive CD4(+) T cells during inflammatory conditions.

Molecular Pathways: Activating T Cells after Cancer Cell Phagocytosis from Blockade of CD47 "Don't Eat Me" Signals

Recent advances with immunotherapy agents for the treatment of cancer have provided remarkable, and in some cases, curative results. Our laboratory has identified CD47 as an important "don't eat me" signal expressed on malignant cells. Blockade of the CD47:SIRP-α axis between tumor cells and innate immune cells (monocytes, macrophages, and dendritic cells) increases tumor cell phagocytosis in both solid tumors (including, but not limited to, bladder, breast, colon, lung, and pancreatic) and hematologic malignancies. These phagocytic innate cells are also professional antigen-presenting cells (APC), providing a link from innate to adaptive antitumor immunity. Preliminary studies have demonstrated that APCs present antigens from phagocytosed tumor cells, causing T-cell activation. Therefore, agents that block the CD47:SIRP-α engagement are attractive therapeutic targets as a monotherapy or in combination with additional immune-modulating agents for activating antitumor T cells in vivo.

Role of CD154 in cancer pathogenesis and immunotherapy

Many factors and molecules have been investigated as potential players in the pathogenesis or immunosurveillance of cancer. Among these, CD154 has been recognized as a co-stimulatory molecule with high potential for treating cancer, in addition to its contribution in the development of the disease. CD154 was initially described for its pivotal role in T cell-dependent humoral responses via an interaction with its classical receptor, CD40. Subsequent studies showed that CD154 is also implicated in cell-mediated immunity and inflammation via an interaction with CD40 alone or in combination with newly identified receptors, members of the integrin family, leading to the development of chronic inflammatory and autoimmune diseases. In the current article, we present an overview of the role of CD154 as a potential etiological factor in tumors inducing proliferation of malignant cells, their rescue from apoptosis and their invasiveness. In addition, this review describes the immuno-regulatory functions of CD154 against cancer reflected by its stimulation of antigen-presenting cells and the subsequent activation of effector cells, its enhancement of malignant cells' immunogenicity, its modulation of immune settings around tumors, and its initiation of proliferation inhibiting effects in malignant cells. In vitro as well as in vivo studies are outlined and a particular attention is given to clinical studies and progress reached at this point. Findings reviewed herein will improve our knowledge of the role of the CD154 system in cancers from causative to immunotherapeutic functions, paving the way for the identification of new targets for prevention and/or treatment of malignant disorders.

The efficacy of tumor debulking surgery is improved by adjuvant immunotherapy using imiquimod and anti-CD40

Background

Tumor debulking surgery followed by adjuvant chemotherapy or radiotherapy is a standard treatment for many solid malignancies. Although this approach can be effective, it often has limited success against recurrent or metastatic cancers and new multimodality approaches are needed. Adjuvant immunotherapy is another potentially effective approach. We therefore tested the efficacy of the TLR7 agonist imiquimod (IMQ) combined with agonistic anti-CD40 in an incomplete debulking model of malignant mesothelioma.

Methods

Established subcutaneous murine ABA-HA mesothelioma tumors in BALB/c mice were surgically debulked by 75% and treated with either: i) saline; ii) intratumoral IMQ; iii) systemic anti-CD40 antibody, or using a combination of IMQ and anti-CD40. Tumour growth and survival were monitored, and the role of anti-tumor CD4 and CD8 T cells in therapeutic responses was determined.

Results

The combination therapy of partial debulking surgery, IMQ and anti-CD40 significantly delayed tumor growth in a CD8 T cell dependent manner, and promoted tumor regression in 25% of animals with establishment of immunological memory. This response was associated with an increase in ICOS+ CD8 T cells and tumor-specific CTL activity in tumor draining lymph nodes along with an increase in ICOS+ CD8 T cells in responding tumours.

Conclusions

We show that the post-surgical environment can be significantly altered by the co-administration of adjuvant IMQ and anti-CD40, resulting in strong, systemic anti-tumor activity. Both adjuvants are available for clinical use/trial, hence this treatment regimen has clear translational potential.

Evaluation of the safety and biodistribution of M032, an attenuated herpes simplex virus type 1 expressing hIL-12, after intracerebral administration to aotus nonhuman primates

Herpes simplex virus type 1 (HSV-1) mutants lacking the γ(1)34.5 neurovirulence loci are promising agents for treating malignant glioma. Arming oncolytic HSV-1 to express immunostimulatory genes may potentiate therapeutic efficacy. We have previously demonstrated improved preclinical efficacy, biodistribution, and safety of M002, a γ(1)34.5-deleted HSV-1 engineered to express murine IL-12. Herein, we describe the safety and biodistribution of M032, a γ(1)34.5-deleted HSV-1 virus that expresses human IL-12 after intracerebral administration to nonhuman primates, Aotus nancymae. Cohorts were administered vehicle, 10(6), or 10(8) pfu of M032 on day 1 and subjected to detailed clinical observations performed serially over a 92-day trial. Animals were sacrificed on days 3, 31, and 91 for detailed histopathologic assessments of all organs and to isolate and quantify virus in all organs. With the possible exception of one animal euthanized on day 16, neither adverse clinical signs nor sex- or dose-related differences were attributed to M032. Elevated white blood cell and neutrophil counts were observed in virus-injected groups on day 3, but no other significant changes were noted in clinical chemistry or coagulation parameters. Minimal to mild inflammation and fibrosis detected, primarily in meningeal tissues, in M032-injected animals on days 3 and 31 had mostly resolved by day 91. The highest viral DNA levels were detected at the injection site and motor cortex on day 3 but decreased in central nervous system tissues over time. These data demonstrate the requisite safety of intracerebral M032 administration for consideration as a therapeutic for treating malignant brain tumors.

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

William Murphy’s group at UC Davis previously found that systemic administration of stimulatory immunotherapy (IT) in aged mice resulted in the rapid induction of cytokine storm culminating in multi-organ pathology and rapid lethality. They now show that in addition to age, increased body fat is critical to this adverse reaction, as aged calorie-restricted mice demonstrate protection from IT-induced toxicity. In contrast, young obese mice succumb to cytokine storm, multi-organ pathology, and lethality after systemic IT administration.

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.

CD4⁺ and CD8⁺ T cell-dependent antiviral immunity requires STIM1 and STIM2

Calcium signaling is critical for lymphocyte function, and intracellular Ca2+ concentrations are regulated by store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels. In patients, loss-of-function mutations in CRAC channel components ORAI1 and STIM1 abolish SOCE and are associated with recurrent and chronic viral infections. Here, using mice with conditional deletion of Stim1 and its homolog Stim2 in T cells, we determined that both components are required for the maintenance of virus-specific memory CD8+ T cells and recall responses following secondary infection. In the absence of STIM1 and STIM2, acute viral infections became chronic. Early during infection, STIM1 and STIM2 were required for the differentiation of naive CD8+ T cells into fully functional cytolytic effector cells and mediated the production of cytokines and prevented cellular exhaustion in viral-specific CD8+ effector T cells. Importantly, memory and recall responses by CD8+ T cells required expression of STIM1 and STIM2 in CD4+ T cells. CD4+ T cells lacking STIM1 and STIM2 were unable to provide "help" to CD8+ T cells due to aberrant regulation of CD40L expression. Together, our data indicate that STIM1, STIM2, and CRAC channel function play distinct but synergistic roles in CD4+ and CD8+ T cells during antiviral immunity.

Bystander activation and anti-tumor effects of CD8+ T cells following Interleukin-2 based immunotherapy is independent of CD4+ T cell help

We have previously demonstrated that immunotherapy combining agonistic anti-CD40 and IL-2 (IT) results in synergistic anti-tumor effects. IT induces expansion of highly cytolytic, antigen-independent “bystander-activated” (CD8⁺CD44^high) T cells displaying a CD25⁻NKG2D⁺ phenotype in a cytokine dependent manner, which were responsible for the anti-tumor effects. While much attention has focused on CD4+ T cell help for antigen-specific CD8+ T cell expansion, little is known regarding the role of CD4+ T cells in antigen-nonspecific bystander-memory CD8+ T cell expansion. Utilizing CD4 deficient mouse models, we observed a significant expansion of bystander-memory T cells following IT which was similar to the non-CD4 depleted mice. Expanded bystander-memory CD8+ T cells upregulated PD-1 in the absence of CD4+ T cells which has been published as a hallmark of exhaustion and dysfunction in helpless CD8+ T cells. Interestingly, compared to CD8+ T cells from CD4 replete hosts, these bystander expanded cells displayed comparable (or enhanced) cytokine production, lytic ability, and in vivo anti-tumor effects suggesting no functional impairment or exhaustion and were enriched in an effector phenotype. There was no acceleration of the post-IT contraction phase of the bystander memory CD8+ response in CD4-depleted mice. The response was independent of IL-21 signaling. These results suggest that, in contrast to antigen-specific CD8+ T cell expansion, CD4+ T cell help is not necessary for expansion and activation of antigen-nonspecific bystander-memory CD8+ T cells following IT, but may play a role in regulating conversion of these cells from a central memory to effector phenotype. Additionally, the expression of PD-1 in this model appears to be a marker of effector function and not exhaustion.

The "Trojan Horse" approach to tumor immunotherapy: targeting the tumor microenvironment

Most anticancer therapies including immunotherapies are given systemically; yet therapies given directly into tumors may be more effective, particularly those that overcome natural suppressive factors in the tumor microenvironment. The “Trojan Horse” approach of intratumoural delivery aims to promote immune-mediated destruction by inducing microenvironmental changes within the tumour at the same time as avoiding the systemic toxicity that is often associated with more “full frontal” treatments such as transfer of large numbers of laboratory-expanded tumor-specific cytotoxic T lymphocytes or large intravenous doses of cytokine. Numerous studies have demonstrated that intratumoural therapy has the capacity to minimizing local suppression, inducing sufficient “dangerous” tumor cell death to cross-prime strong immune responses, and rending tumor blood vessels amenable to immune cell traffic to induce effector cell changes in secondary lymphoid organs. However, the key to its success is the design of a sound rational approach based on evidence. There is compelling preclinical data for local immunotherapy approaches in tumor immunology. This review summarises how immune events within a tumour can be modified by local approaches, how this can affect systemic antitumor immunity such that distal sites are attacked, and what approaches have been proven most successful so far in animals and patients.

Regulatory T cells and myeloid-derived suppressor cells in the tumor microenvironment undergo Fas-dependent cell death during IL-2/αCD40 therapy

Fas ligand expression in certain tumors has been proposed to contribute to immunosuppression and poor prognosis. However, immunotherapeutic approaches may elicit the Fas-mediated elimination of immunosuppressive regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) within tumors that represent major obstacles for cancer immunotherapy. Previously, we showed that IL-2 and agonistic CD40 Ab (αCD40) elicited synergistic antitumor responses coincident with the efficient removal of Tregs and MDSCs. We demonstrate in this study in two murine tumor models that Treg and MDSC loss within the tumor microenvironment after IL-2/αCD40 occurs through a Fas-dependent cell death pathway. Among tumor-infiltrating leukocytes, CD8(+) T cells, neutrophils, and immature myeloid cells expressed Fas ligand after treatment. Fas was expressed by tumor-associated Tregs and immature myeloid cells, including MDSCs. Tregs and MDSCs in the tumor microenvironment expressed active caspases after IL-2/αCD40 therapy and, in contrast with effector T cells, Tregs significantly downregulated Bcl-2 expression. In contrast, Tregs and MDSCs proliferated and expanded in the spleen after treatment. Adoptive transfer of Fas-deficient Tregs or MDSCs into wild-type, Treg-, or MDSC-depleted hosts resulted in the persistence of Tregs or MDSCs and the loss of antitumor efficacy in response to IL-2/αCD40. These results demonstrate the importance of Fas-mediated Treg/MDSC removal for successful antitumor immunotherapy. Our results suggest that immunotherapeutic strategies that include exploiting Treg and MDSC susceptibility to Fas-mediated apoptosis hold promise for treatment of cancer.

Anti-CD40-mediated cancer immunotherapy: an update of recent and ongoing clinical trials

The costimulatory molecule CD40 is a member of the tumor necrosis factor (TNF) receptor superfamily and is expressed on various antigen presenting cells (APCs) as well as some tumor cells. The binding to the natural ligand CD40L, which is expressed on T helper cells, leads to APC activation and thus enhancement of immune responses. Treatment with anti-CD40 monoclonal antibodies has been exploited in several cancer immunotherapy studies in mice and led to the development of anti-CD40 antibodies for clinical use. Here, Dacetuzumab and Lucatumumab are in the most advanced stage and are being tested as treatment for malignancies such as chronic lymphatic leukemia (CLL), Multiple Myeloma (MM), and non-Hodgkin's lymphoma (NHL). The promising results from these early clinical trials have encouraged clinical drug development in order to investigate the effect of CD40 mAbs in combination with other cancer immunotherapies, in particular interleukin (IL)-2. An in-depth analysis of this immunotherapy is provided elsewhere. In the present review, we provide an update of the most recent clinical trials with anti-CD40 antibodies. We present and discuss recent and ongoing clinical trials in this field, including clinical studies which combine anti-CD40 treatment with other cancer-treatments, such as Rituximab and Tremelimumab.

Impact of aging in cancer immunotherapy: The importance of using accurate preclinical models

Cancer immunotherapy holds great promise, yet its efficacy and applicability can be hampered by the rise of systemic toxicities. We have recently shown that the lethal side effects of cancer immunotherapy are markedly exacerbated with aging. Blocking tumor necrosis factor α or macrophages can alleviate the systemic toxicity of immunotherapy while preserving its antineoplastic effects.

Th1 cytokines are more effective than Th2 cytokines at licensing anti-tumour functions in CD40-activated human macrophages in vitro

CD40 agonists are showing activity in early clinical trials in patients with advanced cancer. In animal models, CD40 agonists synergise with T-cell-activating therapies to inhibit tumour growth by driving tumour macrophage repolarisation from an immunosuppressive to a Th1 immunostimulatory, tumouricidal phenotype. We therefore tested the hypothesis that T-cell-derived cytokines license anti-tumour functions in CD40-activated human macrophages. CD40 ligand (CD40L) alone activated macrophages to produce immunosuppressive IL-10, in a similar fashion to bacterial LPS, but failed to promote anti-tumour functions. The Th1 cytokine IFN-γ optimally licensed CD40L-induced macrophage anti-tumour functions, inducing a switch from IL-10 to IL-12p70 production, promoting macrophage-mediated Th1 T-cell skewing and enhancing tumouricidal activity. We found that even the Th2 cytokines IL-4 and IL-13 promoted IL-12p70 production (albeit without inhibiting IL-10 production) and enhanced Th1 T-cell skewing by CD40L-activated macrophages. However, IL-4 and IL-13 did not enhance tumouricidal activity in CD40L-activated macrophages. Thus, while both Th1 and Th2 cytokines biased macrophages to a Th1 immunostimulatory phenotype, only Th1 cytokines promoted tumouricidal activity in CD40L-activated macrophages. The presence of tumour-infiltrating Th1 or Th2 cells might therefore be predictive for patient response to CD40 agonism.

The IL-15-based superagonist ALT-803 promotes the antigen-independent conversion of memory CD8+ T cells into innate-like effector cells with antitumor activity

ALT-803, an interleukin-15-based superagonist, induces memory CD8⁺ T cells to proliferate, upregulate receptors involved in innate immunity, secrete interferon γ and acquire the ability to kill malignant cells in the absence of antigenic stimulation. Thus, ALT-803 can promote the expansion and activation of memory CD8⁺ T cells while converting them into innate immune effector cells that exhibit robust antineoplastic activity.

Aging predisposes to acute inflammatory induced pathology after tumor immunotherapy

Aging strongly promotes inflammation responses, which may predispose individuals after cancer therapies to lethal system toxicities and pathology that can be partially prevented by TNF blockade.

Cancer commonly occurs in the elderly and immunotherapy (IT) is being increasingly applied to this population. However, the majority of preclinical mouse tumor models assessing potential efficacy and toxicities of therapeutics use young mice. We assessed the impact of age on responses to systemic immune stimulation. In contrast to young mice, systemic cancer IT regimens or LPS given to aged mice resulted in rapid and lethal toxicities affecting multiple organs correlating with heightened proinflammatory cytokines systemically and within the parenchymal tissues. This inflammatory response and increased morbidity with age was independent of T cells or NK cells. However, prior in vivo depletion of macrophages in aged mice resulted in lesser cytokine levels, increased survival, and decreased liver histopathology. Furthermore, macrophages from aged mice and normal human elderly volunteers displayed heightened TNF and IL-6 production upon in vitro stimulation. Treatment of both TNF knockout mice and in vivo TNF blockade in aged mice resulted in significant increases in survival and lessened pathology. Importantly, TNF blockade in tumor-bearing, aged mice receiving IT displayed significant anti-tumor effects. These data demonstrate the critical role of macrophages in the age-associated hyper-inflammatory cytokine responses to systemic immunostimulation and underscore the importance of performing preclinical assessments in aged mice.

Immunoediting and antigen loss: overcoming the achilles heel of immunotherapy with antigen non-specific therapies

Cancer immunotherapy has emerged as a mainstream therapy option in the battle against cancer. Pre-clinical data demonstrates the ability of immunotherapy to harness the immune system to fight disseminated malignancy. Clinical translation has failed to recapitulate the promising results of pre-clinical studies although there have been some successes. In this review we explore some of the short-comings of cancer immunotherapy that have limited successful clinical translation. We will give special consideration to what we consider the most formidable hurdle to successful cancer immunotherapy: tumor-induced immune suppression and immune escape. We will discuss the need for antigen-specific immune responses for successful immunotherapy but also consider the need for antigen specificity as an Achilles heel of immunotherapy given tumor heterogeneity, immune editing, and antigen loss. Finally, we will discuss how combinatorial strategies may overcome some of the pitfalls of antigen specificity and highlight recent studies from our lab which suggest that the induction of antigen non-specific immune responses may also produce robust anti-tumor effects and bypass the need for antigen specificity.

Efficacy and mechanism-of-action of a novel superagonist interleukin-15: interleukin-15 receptor αSu/Fc fusion complex in syngeneic murine models of multiple myeloma

ALT-803, a complex of an interleukin (IL)-15 superagonist mutant and a dimeric IL-15 receptor αSu/Fc fusion protein, was found to exhibit significantly stronger in vivo biologic activity on NK and T cells than IL-15. In this study, we show that a single dose of ALT-803, but not IL-15 alone, eliminated well-established 5T33P and MOPC-315P myeloma cells in the bone marrow of tumor-bearing mice. ALT-803 treatment also significantly prolonged survival of myeloma-bearing mice and provided resistance to rechallenge with the same tumor cells through a CD8(+) T-cell-dependent mechanism. ALT-803 treatment stimulated CD8(+) T cells to secrete large amounts of IFN-γ and promoted rapid expansion of CD8(+)CD44(high) memory T cells in vivo. These memory CD8(+) T cells exhibited ALT-803-mediated upregulation of NKG2D (KLRK1) but not PD-1 (PDCD1) or CD25 (IL2RA) on their cell surfaces. ALT-803-activated CD8(+) memory T cells also exhibited nonspecific cytotoxicity against myeloma and other tumor cells in vitro, whereas IFN-γ had no direct effect on myeloma cell growth. ALT-803 lost its antimyeloma activity in tumor-bearing IFN-γ knockout mice but retained the ability to promote CD8(+)CD44(high) memory T-cell proliferation, indicating that ALT-803-mediated stimulation of CD8(+)CD44(high) memory T cells is IFN-γ-independent. Thus, besides well-known IL-15 biologic functions in host immunity, this study shows that IL-15-based ALT-803 could activate CD8(+)CD44(high) memory T cells to acquire a unique innate-like phenotype and secrete IFN-γ for nonspecific tumor cell killing. This unique immunomodulatory property of ALT-803 strongly supports its clinical development as a novel immunotherapeutic agent against cancer and viral infections.

Localized immunotherapy via liposome-anchored Anti-CD137 + IL-2 prevents lethal toxicity and elicits local and systemic antitumor immunity

Immunostimulatory agonists such as anti-CD137 and interleukin (IL)-2 have elicited potent antitumor immune responses in preclinical studies, but their clinical use is limited by inflammatory toxicities that result upon systemic administration. We hypothesized that by rigorously restricting the biodistribution of immunotherapeutic agents to a locally accessible lesion and draining lymph node(s), effective local and systemic antitumor immunity could be achieved in the absence of systemic toxicity. We anchored anti-CD137 and an engineered IL-2Fc fusion protein to the surfaces of PEGylated liposomes, whose physical size permitted dissemination in the tumor parenchyma and tumor-draining lymph nodes but blocked entry into the systemic circulation following intratumoral injection. In the B16F10 melanoma model, intratumoral liposome-coupled anti-CD137 + IL-2Fc therapy cured a majority of established primary tumors while avoiding the lethal inflammatory toxicities caused by equivalent intratumoral doses of soluble immunotherapy. Immunoliposome therapy induced protective antitumor memory and elicited systemic antitumor immunity that significantly inhibited the growth of simultaneously established distal tumors. Tumor inhibition was CD8(+) T-cell-dependent and was associated with increased CD8(+) T-cell infiltration in both treated and distal tumors, enhanced activation of tumor antigen-specific T cells in draining lymph nodes, and a reduction in regulatory T cells in treated tumors. These data suggest that local nanoparticle-anchored delivery of immuno-agonists represents a promising strategy to improve the therapeutic window and clinical applicability of highly potent but otherwise intolerable regimens of cancer immunotherapy. Cancer Res; 73(5); 1547-58. ©2012 AACR.

The use of agonistic anti-CD40 therapy in treatments for cancer

Agonistic anti-CD40 antibody is a potent stimulator of anti-tumor immune responses due to its action on both immune and tumor cells. It has the ability to "precondition" dendritic cells, allowing them to prime effective cytotoxic T-cell responses. Thus, anti-CD40 antibody provides an ideal therapy for combination with traditional cancer treatments (i.e., chemotherapy, surgery) in order to elicit immune-mediated anti-tumor effects. This review summarizes the mechanisms of action of agonistic anti-CD40, the use of mouse models to investigate its effects and combinations with other therapies in vivo, and current clinical trials combining humanized anti-CD40 antibody with chemotherapy and/or other immunotherapies.

Mechanical disruption of tumors by iron particles and magnetic field application results in increased anti-tumor immune responses

The primary tumor represents a potential source of antigens for priming immune responses for disseminated disease. Current means of debulking tumors involves the use of cytoreductive conditioning that impairs immune cells or removal by surgery. We hypothesized that activation of the immune system could occur through the localized release of tumor antigens and induction of tumor death due to physical disruption of tumor architecture and destruction of the primary tumor in situ. This was accomplished by intratumor injection of magneto-rheological fluid (MRF) consisting of iron microparticles, in Balb/c mice bearing orthotopic 4T1 breast cancer, followed by local application of a magnetic field resulting in immediate coalescence of the particles, tumor cell death, slower growth of primary tumors as well as decreased tumor progression in distant sites and metastatic spread. This treatment was associated with increased activation of DCs in the draining lymph nodes and recruitment of both DCs and CD8(+)T cells to the tumor. The particles remained within the tumor and no toxicities were observed. The immune induction observed was significantly greater compared to cryoablation. Further anti-tumor effects were observed when MRF/magnet therapy was combined with systemic low dose immunotherapy. Thus, mechanical disruption of the primary tumor with MRF/magnetic field application represents a novel means to induce systemic immune activation in cancer.

Agonistic antibody to CD40 boosts the antitumor activity of adoptively transferred T cells in vivo

CD40, a member of the tumor necrosis factor receptor superfamily, is broadly expressed on antigen-presenting cells and other cells, including fibroblasts and endothelial cells. Binding of CD40 and its natural ligand CD40L (CD154) triggers cytokine secretion, and increased expression of costimulatory molecules is required for T-cell activation and proliferation. However, to our knowledge, the use of agonistic antibodies to CD40 to boost adoptively transferred T cells in vivo has not been investigated. The purpose of this study was to determine whether anti-CD40 monoclonal antibody (mAb) in combination with interleukin (IL)-2 could improve the efficacy of in vitro-activated T cells to enhance antitumor activity. Mice bearing B16 melanoma tumors expressing the gp100 tumor antigen were treated with cultured, activated T cells transgenic for a T-cell receptor specifically recognizing gp100, with or without anti-CD40 mAb. In this model, the combination of anti-CD40 mAb with IL-2 led to expansion of adoptively transferred T cells and induced a more robust antitumor response. Furthermore, the expression of CD40 on bone marrow-derived cells and the presence of CD80/CD86 in the host were required for the expansion of adoptively transferred T cells. The use of neutralizing mAb to IL-12 provided direct evidence that enhanced IL-12 secretion induced by anti-CD40 mAb was crucial for the expansion of adoptively transferred T cells. Collectively, these findings provide a rationale to evaluate the potential application of anti-CD40 mAb in adoptive T-cell therapy for cancer.

The role of antigen-specific and non-specific immunotherapy in the treatment of cancer

Immunotherapy in the treatment of cancer is increasing, particularly with the recent FDA approval of sipuleucel-T and ipilimumab. The efficacy of anti-tumor immunotherapies has been modest compared to their theoretical and pre-clinical promise. This review evaluates the promise and pitfalls of immunotherapy and highlight some of the obstacles to improving anti-tumor immunotherapy: the need for technical refinement of therapies, the need for an increased understanding of how best to combine therapies with traditional cytotoxic therapies, the inability of patients to mount an effective immune response either due to disease burden or tumor induced immune suppression, the significant toxicities associated with many immunotherapies, and the lack of strongly immunogenic antigens required by many therapies. Further, antigen-non-specific immunotherapies, including cytokines such as interleukins and interferons, immuno-stimulatory agents such as CpG oligonucleotides, or BCG, antibodies targeted against receptors such as the agonistic CD40 or inhibitory CTLA-4 antibodies, and enzyme inhibitors such as those targeting cyclo-oxygenase or indolamine-2,3-dioxygenase are discussed. In addition, potential mechanisms of these therapies such as direct anti-tumor effects, reversal of immune suppression, activation of innate immunity, and antigen-non-specific T-cell activation are reviewed. We also appraise the potential of these antigen-non-specific therapies to overcome some of the previously described pitfalls of immunotherapy. Lastly, we discuss a recent series of studies from our laboratory demonstrating the importance of antigen-non-specific 'bystander activation' of memory T-lymphocytes by immunomodulatory therapies such as interleukin-2 and the antigen-non-specific anti-tumor effects of these cells.

Delineation of antigen-specific and antigen-nonspecific CD8(+) memory T-cell responses after cytokine-based cancer immunotherapy

Memory T cells exhibit tremendous antigen specificity within the immune system and accumulate with age. Our studies reveal an antigen-independent expansion of memory, but not naive, CD8(+) T cells after several immunotherapeutic regimens for cancer resulting in a distinctive phenotype. Signaling through T-cell receptors (TCRs) or CD3 in both mouse and human memory CD8(+) T cells markedly up-regulated programmed death-1 (PD-1) and CD25 (IL-2 receptor α chain), and led to antigen-specific tumor cell killing. In contrast, exposure to cytokine alone in vitro or with immunotherapy in vivo did not up-regulate these markers but resulted in expanded memory CD8(+) T cells expressing NKG2D, granzyme B, and possessing broadly lytic capabilities. Blockade of NKG2D in mice also resulted in significantly diminished antitumor effects after immunotherapy. Treatment of TCR-transgenic mice bearing nonantigen expressing tumors with immunotherapy still resulted in significant antitumor effects. Human melanoma tissue biopsies obtained from patients after topically applied immunodulatory treatment resulted in increased numbers of these CD8(+) CD25(-) cells within the tumor site. These findings demonstrate that memory CD8(+) T cells can express differential phenotypes indicative of adaptive or innate effectors based on the nature of the stimuli in a process conserved across species.

Induction of potent anti-tumor responses while eliminating systemic side effects via liposome-anchored combinatorial immunotherapy

Immunostimulatory therapies that activate immune response pathways are of great interest for overcoming the immunosuppression present in advanced tumors. Agonistic anti-CD40 antibodies and CpG oligonucleotides have previously demonstrated potent, synergistic anti-tumor effects, but their clinical use even as monotherapies is hampered by dose-limiting inflammatory toxicity provoked upon systemic exposure. We hypothesized that by anchoring immuno-agonist compounds to lipid nanoparticles we could retain the bioactivity of therapeutics in the local tumor tissue and tumor-draining lymph node, but limit systemic exposure to these potent molecules. We prepared PEGylated liposomes bearing surface-conjugated anti-CD40 and CpG and assessed their therapeutic efficacy and systemic toxicity compared to soluble versions of the same immuno-agonists, injected intratumorally in the B16F10 murine model of melanoma. Anti-CD40/CpG-liposomes significantly inhibited tumor growth and induced a survival benefit similar to locally injected soluble anti-CD40 + CpG. Biodistribution analyses following local delivery showed that the liposomal carriers successfully sequestered anti-CD40 and CpG in vivo, reducing leakage into systemic circulation while allowing draining to the tumor-proximal lymph node. Contrary to locally-administered soluble immunotherapy, anti-CD40/CpG-liposomes did not elicit significant increases in serum levels of ALT enzyme, systemic inflammatory cytokines, or overall weight loss, confirming that off-target inflammatory effects had been minimized. The development of a delivery strategy capable of inducing robust anti-tumor responses concurrent with minimal systemic side effects is crucial for the continued progress of potent immunotherapies toward widespread clinical translation.

Immunotherapeutic modulation of the suppressive liver and tumor microenvironments

The liver is an immunologically unique organ, consisting of resident hematopoietic and parenchymal cells which often contribute to a relatively tolerant microenvironment. It is also becoming increasingly clear that tumor-induced immunosuppression occurs via many of the same cellular mechanisms which contribute to the tolerogenic liver microenvironment. Myeloid cells, consisting of dendritic cells (DC), macrophages and myeloid derived suppressor cells (MDSC), have been implicated in providing a tolerogenic liver environment and immune dysfunction within the tumor microenvironment which can favor tumor progression. As we increase our understanding of the biological mechanisms involved for each phenotypic and/or functionally distinct leukocyte subset, immunotherapeutic strategies can be developed to overcome the inherent barriers to the development of improved strategies for the treatment of liver disease and tumors. In this review, we discuss the principal myeloid cell-based contributions to immunosuppression that are shared between the liver and tumor microenvironments. We further highlight immune-based strategies shown to modulate immunoregulatory cells within each microenvironment and enhance anti-tumor responses.

Macrophage-dependent nitric oxide expression regulates tumor cell detachment and metastasis after IL-2/anti-CD40 immunotherapy

Immunotherapy with IL-2 and anti-CD40 induces the expression of NOS2 in tumor-associated macrophages, and its expression is required for the inhibition of tumor metastasis.

Using an orthotopic model of renal cell carcinoma, we showed previously that IL-2/anti-CD40 immunotherapy resulted in synergistic anti-tumor responses, whereas IL-2 or α-CD40 alone mediated partial transient anti-tumor effects. We now show that treatment of tumor-bearing mice with IL-2/α-CD40, but not IL-2 or α-CD40, induced significant nitric oxide synthase (NOS) 2 expression in tumor-associated macrophages. In control-treated mice (low NO), NOS2 inhibition reduced tumor burden. However, during immunotherapy (high NO), NOS2 inhibition or macrophage depletion reversed the ability of IL-2/α-CD40 treatment to reduce lung metastases but had no effect on primary tumor burden. Furthermore, IL-2/α-CD40 induced the IFN-γ– and NO-dependent decrease in matrix metalloproteinase (MMP) expression and activity, concomitant with increases in tissue inhibitor of metalloproteinase (TIMP) 1 and E-cadherin expression within tumors. Finally, treatment of tumor-bearing mice with the NO donor JS-K significantly reduced metastases. These data differentiate the mechanism for primary anti-tumor effects of IL-2/α-CD40 immunotherapy, which are independent of NO, from the NO-dependent inhibition of metastases. Furthermore, reduced MMP9 activity implicates M1-polarized macrophages within the tumor microenvironment as critical components of therapeutic response. Our data demonstrate the mechanistic basis for IL-2/α-CD40–mediated control of metastases and suggest that the context-dependent application of NO donors may hold promise for prevention of metastatic disease.

Advances in lupus stemming from the parent-into-F1 model

The parent-into-F1 model has led to important advances in our understanding of lupus. Here, we review the work in murine lupus that elucidated the role of T cells and supported the conclusion that the parent-into-F1 model of induced lupus compares favorably with de facto gold standard spontaneous models of lupus. Then we focus on recent work in parent-into-F1 mice, which has yielded novel insights into unresolved controversies, such as the role of apoptosis in the pathogenesis of lupus and lupus in patients receiving TNF blockade. Finally, the review considers the evidence that supports a potential role for CD8 T cells, both cytotoxic and memory cells, in mediating disease remission.