CD40 ligation activates murine macrophages via an IFN-gamma-dependent mechanism resulting in tumor cell destruction in vitro

Innate immune cells in tumor microenvironment: A new frontier in cancer immunotherapy

Innate immune cells, crucial in resisting infections and initiating adaptive immunity, play diverse and significant roles in tumor development. These cells, including macrophages, granulocytes, dendritic cells (DCs), innate lymphoid cells, and innate-like T cells, are pivotal in the tumor microenvironment (TME). Innate immune cells are crucial components of the TME, based on which various immunotherapy strategies have been explored. Immunotherapy strategies, such as novel immune checkpoint inhibitors, STING/CD40 agonists, macrophage-based surface backpack anchoring, ex vivo polarization approaches, DC-based tumor vaccines, and CAR-engineered innate immune cells, aim to enhance their anti-tumor potential and counteract cancer-induced immunosuppression. The proximity of innate immune cells to tumor cells in the TME also makes them excellent drug carriers. In this review, we will first provide a systematic overview of innate immune cells within the TME and then discuss innate cell-based therapeutic strategies. Furthermore, the research obstacles and perspectives within the field will also be addressed.

The engineered agonistic anti-CD40 antibody potentiates the antitumor effects of β-glucan by resetting TAMs

Anti-CD40 antibodies (Abs) have been shown to induce antitumor T-cell responses. We reported that the engineered agonistic anti-CD40 Ab (5C11, IgG4 isotype) recognized human CD40 antigen expressed on a human B lymphoblastoid cell line as well as on splenic cells isolated from humanized CD40 mice. Of note, a single high dosage of 5C11 was able to prohibit tumor growth in parallel with an increase in the population of infiltrated CD8+ T cells. Furthermore, the antitumor effects of 5C11 were enhanced in the presence of β-glucan along with an increase in the population of infiltrated CD8+ T cells. In addition, the numbers of CD86+ TAMs and neutrophils were elevated in the combination of 5C11 and β-glucan compared with either 5C11 or β-glucan alone. Furthermore, the abundance of Faecalibaculum, one of the probiotics critical for tumor suppression, was obviously increased in the combination of 5C11 and β-glucan-treated mice. These data reveal a novel mechanism of tumor suppression upon the combination treatment of 5C11 and β-glucan and propose that the combination treatment of agonistic anti-human CD40 antibody 5C11 and β-glucan could be a promising therapeutic strategy for cancer patients.

Co-stimulators CD40-CD40L, a potential immune-therapy target for atherosclerosis: A review

The interaction between CD40 and CD40 ligand (CD40L) a crucial co-stimulatory signal for activating adaptive immune cells, has a noteworthy role in atherosclerosis. It is well-known that atherosclerosis is linked to immune inflammation in blood vessels. In atherosclerotic lesions, there is a multitude of proinflammatory cytokines, adhesion molecules, and collagen, as well as smooth muscle cells, macrophages, and T lymphocytes, particularly the binding of CD40 and CD40L. Therefore, research on inhibiting the CD40-CD40L system to prevent atherosclerosis has been ongoing for more than 30 years. However, it's essential to note that long-term direct suppression of CD40 or CD40L could potentially result in immunosuppression, emphasizing the critical role of the CD40-CD40L system in atherosclerosis. Thus, specifically targeting the CD40-CD40L interaction on particular cell types or their downstream signaling pathways may be a robust strategy for mitigating atherosclerosis, reducing potential side effects. This review aims to summarize the potential utility of the CD40-CD40L system as a viable therapeutic target for atherosclerosis.

Reprogramming macrophage by targeting VEGF and CD40 potentiates OX40 immunotherapy

The low clinical response rate of checkpoint blockades, such as PD-1 and CTLA-4, highlighted the requirements of agonistic antibodies to boost optimal T cell responses. OX40, a co-stimulatory receptor on the T cells, plays a crucial role in promoting T cell survival and differentiation. However, the clinical efficacy of anti-OX40 agonistic antibodies was unimpressive. To explore the mechanism underlying the action of anti-OX40 agonists to improve the anti-tumor efficacy, we analyzed the dynamic changes of tumor-infiltrating immune cells at different days post-treatments using single-cell RNA-sequencing (scRNA-seq). In this study, we found that tumor-infiltrating regulatory T (Treg) cells were reduced after two rounds of anti-OX40 treatment, but the increase of infiltration and activation of CD8+ effector T cells, as well as M1 polarization in the tumor were only observed after three rounds of treatments. Moreover, our group first analyzed the antitumor effect of anti-OX40 treatments on regulating the macrophages and discovered the dynamic changes of vascular endothelial growth factor (VEGF) and CD40 signaling pathways on macrophages, indicating their possibility to being potential combination targets to improve the anti-OX40 agonists efficacy. The combination of VEGFR inhibitors or anti-CD40 agonist antibody with anti-OX40 agonists exhibited more remarkable inhibition of tumor growth. Therefore, the mechanism-driven combination of anti-OX40 agonists with VEGFR inhibitors or anti-CD40 agonists represented promising strategies.

Harnessing the potential of CD40 agonism in cancer therapy

CD40 is a member of the tumor necrosis factor (TNF) receptor superfamily of receptors expressed on a variety of cell types. The CD40-CD40L interaction gives rise to many immune events, including the licensing of dendritic cells to activate CD8+ effector T cells, as well as the facilitation of B cell activation, proliferation, and differentiation. In malignant cells, the expression of CD40 varies among cancer types, mediating cellular proliferation, apoptosis, survival and the secretion of cytokines and chemokines. Agonistic human anti-CD40 antibodies are emerging as an option for cancer treatment, and early-phase clinical trials explored its monotherapy or combination with radiotherapy, chemotherapy, immune checkpoint blockade, and other immunomodulatory approaches. In this review, we present the current understanding of the mechanism of action for CD40, along with results from the clinical development of agonistic human CD40 antibodies in cancer treatment (selicrelumab, CDX-1140, APX005M, mitazalimab, 2141-V11, SEA-CD40, LVGN7409, and bispecific antibodies). This review also examines the safety profile of CD40 agonists in both preclinical and clinical settings, highlighting optimized dosage levels, potential adverse effects, and strategies to mitigate them.

Pre-Clinical Investigations of the Pharmacodynamics of Immunogenic Smart Radiotherapy Biomaterials (iSRB)

The use of an immunogenic smart radiotherapy biomaterial (iSRB) for the delivery of anti-CD40 is effective in treating different cancers in animal models. This study further characterizes the use of iSRBs to evaluate any associated toxicity in healthy C57BL6 mice. iSRBs were fabricated using a poly-lactic-co-glycolic-acid (PLGA) polymer mixed with titanium dioxide (TiO2) nanoparticles incorporated into its matrix. Animal studies included investigations of freely injected anti-CD40, anti-CD40-loaded iSRBs, unloaded iSRBs and control (healthy) animal cohorts. Mice were euthanized at pre-determined time points post-treatment to evaluate the serum chemistry pertaining to kidney and liver toxicity and cell blood count parameters, as well as pathology reports on organs of interest. Results showed comparable liver and kidney function in all cohorts. The results indicate that using iSRBs with or without anti-CD40 does not result in any significant toxicity compared to healthy untreated animals. The findings provide a useful reference for further studies aimed at optimizing the therapeutic efficacy and safety of iSRBs and further clinical translation work.

Exploiting innate immunity for cancer immunotherapy

Immunotherapies have revolutionized the treatment paradigms of various types of cancers. However, most of these immunomodulatory strategies focus on harnessing adaptive immunity, mainly by inhibiting immunosuppressive signaling with immune checkpoint blockade, or enhancing immunostimulatory signaling with bispecific T cell engager and chimeric antigen receptor (CAR)-T cell. Although these agents have already achieved great success, only a tiny percentage of patients could benefit from immunotherapies. Actually, immunotherapy efficacy is determined by multiple components in the tumor microenvironment beyond adaptive immunity. Cells from the innate arm of the immune system, such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, natural killer cells, and unconventional T cells, also participate in cancer immune evasion and surveillance. Considering that the innate arm is the cornerstone of the antitumor immune response, utilizing innate immunity provides potential therapeutic options for cancer control. Up to now, strategies exploiting innate immunity, such as agonists of stimulator of interferon genes, CAR-macrophage or -natural killer cell therapies, metabolic regulators, and novel immune checkpoint blockade, have exhibited potent antitumor activities in preclinical and clinical studies. Here, we summarize the latest insights into the potential roles of innate cells in antitumor immunity and discuss the advances in innate arm-targeted therapeutic strategies.

Macrophage-Based Therapeutic Strategies in Hematologic Malignancies

Macrophages are types of immune cells, with ambivalent functions in tumor growth, which depend on the specific environment in which they reside. Tumor-associated macrophages (TAMs) are a diverse population of immunosuppressive myeloid cells that play significant roles in several malignancies. TAM infiltration in malignancies has been linked to a poor prognosis and limited response to treatments, including those using checkpoint inhibitors. Understanding the precise mechanisms through which macrophages contribute to tumor growth is an active area of research as targeting these cells may offer potential therapeutic approaches for cancer treatment. Numerous investigations have focused on anti-TAM-based methods that try to eliminate, rewire, or target the functional mediators released by these cells. Considering the importance of these strategies in the reversion of tumor resistance to conventional therapies and immune modulatory vaccination could be an appealing approach for the immunosuppressive targeting of myeloid cells in the tumor microenvironment (TME). The combination of reprogramming and TAM depletion is a special feature of this approach compared to other clinical strategies. Thus, the present review aims to comprehensively overview the pleiotropic activities of TAMs and their involvement in various stages of cancer development as a potent drug target, with a focus on hematologic tumors.

Cell targeting and immunostimulatory properties of a novel Fcγ-receptor-independent agonistic anti-CD40 antibody in rhesus macaques

Targeting CD40 by agonistic antibodies used as vaccine adjuvants or for cancer immunotherapy is a strategy to stimulate immune responses. The majority of studied agonistic anti-human CD40 antibodies require crosslinking of their Fc region to inhibitory FcγRIIb to induce immune stimulation although this has been associated with toxicity in previous studies. Here we introduce an agonistic anti-human CD40 monoclonal IgG1 antibody (MAB273) unique in its specificity to the CD40L binding site of CD40 but devoid of Fcγ-receptor binding. We demonstrate rapid binding of MAB273 to B cells and dendritic cells resulting in activation in vitro on human cells and in vivo in rhesus macaques. Dissemination of fluorescently labeled MAB273 after subcutaneous administration was found predominantly at the site of injection and specific draining lymph nodes. Phenotypic cell differentiation and upregulation of genes associated with immune activation were found in the targeted tissues. Antigen-specific T cell responses were enhanced by MAB273 when given in a prime-boost regimen and for boosting low preexisting responses. MAB273 may therefore be a promising immunostimulatory adjuvant that warrants future testing for therapeutic and prophylactic vaccination strategies.

Dynamic polarization of tumor-associated macrophages and their interaction with intratumoral T cells in an inflamed tumor microenvironment: from mechanistic insights to therapeutic opportunities

Immunotherapy has brought a paradigm shift in the treatment of tumors in recent decades. However, a significant proportion of patients remain unresponsive, largely due to the immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play crucial roles in shaping the TME by exhibiting dual identities as both mediators and responders of inflammation. TAMs closely interact with intratumoral T cells, regulating their infiltration, activation, expansion, effector function, and exhaustion through multiple secretory and surface factors. Nevertheless, the heterogeneous and plastic nature of TAMs renders the targeting of any of these factors alone inadequate and poses significant challenges for mechanistic studies and clinical translation of corresponding therapies. In this review, we present a comprehensive summary of the mechanisms by which TAMs dynamically polarize to influence intratumoral T cells, with a focus on their interaction with other TME cells and metabolic competition. For each mechanism, we also discuss relevant therapeutic opportunities, including non-specific and targeted approaches in combination with checkpoint inhibitors and cellular therapies. Our ultimate goal is to develop macrophage-centered therapies that can fine-tune tumor inflammation and empower immunotherapy.

Single-cell atlas of the human neonatal small intestine affected by necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a gastrointestinal complication of premature infants with high rates of morbidity and mortality. A comprehensive view of the cellular changes and aberrant interactions that underlie NEC is lacking. This study aimed at filling in this gap. We combine single-cell RNA sequencing (scRNAseq), T-cell receptor beta (TCRβ) analysis, bulk transcriptomics, and imaging to characterize cell identities, interactions, and zonal changes in NEC. We find an abundance of proinflammatory macrophages, fibroblasts, endothelial cells as well as T cells that exhibit increased TCRβ clonal expansion. Villus tip epithelial cells are reduced in NEC and the remaining epithelial cells up-regulate proinflammatory genes. We establish a detailed map of aberrant epithelial-mesenchymal-immune interactions that are associated with inflammation in NEC mucosa. Our analyses highlight the cellular dysregulations of NEC-associated intestinal tissue and identify potential targets for biomarker discovery and therapeutics.

Translatable Drug-Loaded Iron Oxide Nanophore Sensitizes Murine Melanoma Tumors to Monoclonal Antibody Immunotherapy

Macrophages comprise a significant portion of the immune cell compartment within tumors and are known contributors to tumor pathology; however, cancer immunotherapies targeting these cells are not clinically available. The iron oxide nanoparticle, ferumoxytol (FH), may be utilized as a nanophore for drug delivery to tumor-associated macrophages. We have demonstrated that a vaccine adjuvant, monophosphoryl lipid A (MPLA), can be stably captured within the carbohydrate shell of ferumoxytol without chemical modification of either the drug or the nanophore. This drug-nanoparticle combination (FH-MPLA) activated macrophages to an antitumorigenic phenotype at clinically relevant concentrations. In the immunotherapy-resistant B16-F10 model of murine melanoma, FH-MPLA treatment induced tumor necrosis and regression in combination with agonistic α-CD40 monoclonal antibody therapy. FH-MPLA, composed of clinically approved nanoparticle and drug payload, represents a potential cancer immunotherapy with translational relevance. FH-MPLA may be useful as an adjunctive therapy to existing antibody-based cancer immunotherapies which target only lymphocytic cells, reshaping the tumor immune environment.

Immunotoxin-αCD40 therapy activates innate and adaptive immunity and generates a durable antitumor response in glioblastoma models

D2C7-immunotoxin (IT), a dual-specific IT targeting wild-type epidermal growth factor receptor (EGFR) and mutant EGFR variant III (EGFRvIII) proteins, demonstrates encouraging survival outcomes in a subset of patients with glioblastoma. We hypothesized that immunosuppression in glioblastoma limits D2C7-IT efficacy. To improve the response rate and reverse immunosuppression, we combined D2C7-IT tumor cell killing with αCD40 costimulation of antigen-presenting cells. In murine glioma models, a single intratumoral injection of D2C7-IT+αCD40 treatment activated a proinflammatory phenotype in microglia and macrophages, promoted long-term tumor-specific CD8+ T cell immunity, and generated cures. D2C7-IT+αCD40 treatment increased intratumoral Slamf6+CD8+ T cells with a progenitor phenotype and decreased terminally exhausted CD8+ T cells. D2C7-IT+αCD40 treatment stimulated intratumoral CD8+ T cell proliferation and generated cures in glioma-bearing mice despite FTY720-induced peripheral T cell sequestration. Tumor transcriptome profiling established CD40 up-regulation, pattern recognition receptor, cell senescence, and immune response pathway activation as the drivers of D2C7-IT+αCD40 antitumor responses. To determine potential translation, immunohistochemistry staining confirmed CD40 expression in human GBM tissue sections. These promising preclinical data allowed us to initiate a phase 1 study with D2C7-IT+αhCD40 in patients with malignant glioma (NCT04547777) to further evaluate this treatment in humans.

Antibody-induced erythrophagocyte reprogramming of Kupffer cells prevents anti-CD40 cancer immunotherapy-associated liver toxicity

BACKGROUND

Agonistic anti-CD40 monoclonal antibodies (mAbs) have emerged as promising immunotherapeutic compounds with impressive antitumor effects in mouse models. However, preclinical and clinical studies faced dose-limiting toxicities mediated by necroinflammatory liver disease. An effective prophylactic treatment for liver immune-related adverse events that does not suppress specific antitumor immunity remains to be found.

METHODS

We used different mouse models and time-resolved single-cell RNA-sequencing to characterize the pathogenesis of anti-CD40 mAb induced liver toxicity. Subsequently, we developed an antibody-based treatment protocol to selectively target red blood cells (RBCs) for erythrophagocytosis in the liver, inducing an anti-inflammatory liver macrophage reprogramming.

RESULTS

We discovered that CD40 signaling in Clec4f+ Kupffer cells is the non-redundant trigger of anti-CD40 mAb-induced liver toxicity. Taking advantage of the highly specific functionality of liver macrophages to clear antibody-tagged RBCs from the blood, we hypothesized that controlled erythrophagocytosis and the linked anti-inflammatory signaling by the endogenous metabolite heme could be exploited to reprogram liver macrophages selectively. Repeated low-dose administration of a recombinant murine Ter119 antibody directed RBCs for selective phagocytosis in the liver and skewed the phenotype of liver macrophages into a Hmoxhigh/Marcohigh/MHCIIlow anti-inflammatory phenotype. This unique mode of action prevented necroinflammatory liver disease following high-dose administration of anti-CD40 mAbs. In contrast, extrahepatic inflammation, antigen-specific immunity, and antitumor activity remained unaffected in Ter119 treated animals.

CONCLUSIONS

Our study offers a targeted approach to uncouple CD40-augmented antitumor immunity in peripheral tissues from harmful inflammatoxicity in the liver.

Extensive involvement of CD40 and CD154 costimulators in multiple T cell-mediated responses in a perciform fish Larimichthys crocea

CD40 and CD154 are well-characterized costimulatory molecules involved in adaptive humoral immunity in humans and other mammals. These two costimulatory molecules were found to be originated from teleost fish during vertebrate evolution. However, the functionality of fish CD40 and CD154 remains to be explored. In this study, we identified the CD40 and CD154 homologs (LcCD40 and LcCD154) from large yellow croaker (Larimichthys crocea), a marine species of the perciform fish family. The LcCD40 and LcCD154 share conserved structural features to their mammalian counterparts, and are widely expressed in immune-relevant tissues and leukocytes at different transcriptional levels. Immunofluorescence staining and FCM analysis showed that LcCD40 and LcCD154 proteins are distributed on MHC-II⁺ APCs and CD4-2⁺ T cells, and are significantly upregulated in response to antigen stimulation. Co-IP assay exhibited strong association between LcCD40 and LcCD154 proteins. Blockade of LcCD154 with anti-LcCD154 antibody (Ab) or recombinant soluble LcCD40-Ig fusion protein remarkably decreased the MHC-II⁺ APC-initiated CD4⁺ T cell response upon Aeromonas hydrophila stimulation, and alloreactive T cell activation as examined by mixed lymphocyte reaction (MLR). These findings highlight the costimulatory role of LcCD40 and LcCD154 in T cell activities in Larimichthys crocea. Thus, the CD40 and CD154 costimulators may extensively participate in the regulation of multiple T cell-mediated immune responses in teleost fish. It is anticipated that this study would provide a cross-species understanding of the evolutionary history of CD40 and CD154 costimulatory signals from fish to mammals.

CD40 Agonists Alter the Pancreatic Cancer Microenvironment by Shifting the Macrophage Phenotype toward M1 and Suppress Human Pancreatic Cancer in Organotypic Slice Cultures

Background/Aims

CD40 agonists are thought to generate antitumor effects on pancreatic cancer via macrophages and T cells. We aimed to investigate the role of CD40 agonists in the differentiation of macrophages and treatment of human pancreatic adenocarcinoma.

Methods

Immunohistochemistry was performed on paraffin-embedded surgical blocks from patients with pancreatic cancers to evaluate macrophage phenotypes and their relationship with survival. The effects of CD40 agonists on macrophage phenotypes and human pancreatic cancer were evaluated utilizing cell cocultures and organotypic slice cultures.

Results

CD163+ (predominant in M2 macrophages) and FOXP3+ (predominant in regulatory T cells) expression levels in the tumors were significantly lower in patients with stage IB pancreatic cancer than in those with stage II or III disease (p=0.002 and p=0.003, respectively). Patients with high CD163+ expression had shorter overall survival than those with low CD163+ expression (p=0.002). In vitro treatment of THP-1 macrophages with a CD40 agonist led to an increase in HLA-DR+ (predominant in M1 macrophages) and a decrease in CD163+ expression in THP-1 cells. Cell cocultures showed that CD40 agonists facilitate the suppression of PANC-1 human pancreatic cancer cells by THP-1 macrophages. Organotypic slice cultures showed that CD40 agonists alter the pancreatic cancer microenvironment by shifting the macrophage phenotype toward M1 (increase HLA-DR+ and decrease CD163+ expression), decreasing the abundance of regulatory T cells, and increasing tumor cell apoptosis.

Conclusions

CD163 is related to advanced human pancreatic cancer stages and shorter overall survival. CD40 agonists alter macrophage phenotype polarization to favor the M1 phenotype and suppress human pancreatic cancer.

Myeloid CD40 deficiency reduces atherosclerosis by impairing macrophages' transition into a pro-inflammatory state

AIMS

CD40 and its ligand, CD40L, play a critical role in driving atherosclerotic plaque development. Disrupted CD40-signaling reduces experimental atherosclerosis and induces a favourable stable plaque phenotype. We recently showed that small molecule-based inhibition of CD40-TNF Receptor Associated Factor-6 interactions attenuates atherosclerosis in hyperlipidaemic mice via macrophage-driven mechanisms. The present study aims to detail the function of myeloid CD40 in atherosclerosis using myeloid-specific CD40-deficient mice.

METHOD AND RESULTS

Cd40flox/flox and LysM-cre Cd40flox/flox mice on an Apoe-/- background were generated (CD40wt and CD40mac-/-, respectively). Atherosclerotic lesion size, as well as plaque macrophage content, were reduced in CD40mac-/- compared to CD40wt mice and their plaques displayed a reduction in necrotic core size. Transcriptomics analysis of the CD40mac-/- atherosclerotic aorta revealed downregulated pathways of immune pathways and inflammatory responses.Loss of CD40 in macrophages changed the representation of aortic macrophage subsets. Mass cytometry analysis revealed a higher content of a subset of alternative or resident-like CD206 + CD209b- macrophages in the atherosclerotic aorta of CD40mac-/- compared to CD40wt mice. RNA-sequencing of bone marrow-derived macrophages (BMDMs) of CD40mac-/- mice demonstrated upregulation of genes associated with alternatively activated macrophages (including Folr2, Thbs1, Sdc1 and Tns1).

CONCLUSIONS

We here show that absence of CD40 signalling in myeloid cells reduces atherosclerosis and limits systemic inflammation by preventing a shift in macrophage polarization towards pro-inflammatory states. Our study confirms the merit of macrophage-targeted inhibition of CD40 as a valuable therapeutic strategy to combat atherosclerosis.

Synthesis, Characterization, and In Vivo Cytokinome Profile of IL-12-Loaded PLGA Nanospheres

We report the successful encapsulation and elution of recombinant murine IL-12 (rmIL-12) from poly(lactide-co-glycolic) acid (PLGA) nanospheres (IL-12-NS) synthesized using the double emulsion/solvent evaporation (DESE) technique with microsphere depletion through ultracentrifugation. Images obtained with scanning electron microscopy (SEM) showcased a characteristic spherical shape with a mean particle diameter of 138.1 ± 10.8 nm and zeta potential of −15.1 ± 1.249 mV. These values suggest minimal flocculation when in solution, which was reflected in an in vivo biodistribution study that reported no observed morbidity/mortality. Encapsulation efficiency (EE) was determined to be 0.101 ± 0.009% with average particle concentration obtained per batch of 1.66 × 10⁹ ± 4.45 × 10⁸ particles/mL. Disparate zeta (ζ) potentials obtained from both protein-loaded and protein-unloaded batches suggested surface adsorption of protein, and confocal microscopy of BSA-FITC-loaded nanospheres confirmed the presence of protein within the polymeric shell. Furthermore, elution of rmIL-12 from IL-12-NS at a concentration of 500 million particles/mL was characterized using enzyme-linked immunosorbent assay (ELISA). When IL-12-NS was administered in vivo to female BALB/c mice through retroorbital injection, IL-12-NS produced a favorable systemic cytokine profile for tumoricidal activity within the peripheral blood. Whereas IFN-γ nadir occurred at 72 hours, levels recovered quickly and displayed positive correlations postburst out to 25 days postinjection. IL-12-NS administration induced proinflammatory changes while prompting minimal counterregulatory increases in anti-inflammatory IL-10 and IL-4 cytokine levels. Further, while IL-6 levels increased to 30 folds of the baseline during the burst phase, they normalized by 72 hours and trended negatively throughout the sill phase. Similar trends were observed with IL-1β and CXCL-1, suggesting a decreased likelihood of progression to a systemic inflammatory response syndrome-like state. As IL-12-NS delivers logarithmically lower amounts of IL-12 than previously administered during human clinical trials, our data reflect the importance of IL-12-NS which safely create a systemic immunostimulatory environment.

Enabling the next steps in cancer immunotherapy: from antibody-based bispecifics to multispecifics, with an evolving role for bioconjugation chemistry

In the past two decades, immunotherapy has established itself as one of the leading strategies for cancer treatment, as illustrated by the exponentially growing number of related clinical trials. This trend was, in part, prompted by the clinical success of both immune checkpoint modulation and immune cell engagement, to restore and/or stimulate the patient's immune system's ability to fight the disease. These strategies were sustained by progress in bispecific antibody production. However, despite the decisive progress made in the treatment of cancer, toxicity and resistance are still observed in some cases. In this review, we initially provide an overview of the monoclonal and bispecific antibodies developed with the objective of restoring immune system functions to treat cancer (cancer immunotherapy), through immune checkpoint modulation, immune cell engagement or a combination of both. Their production, design strategy and impact on the clinical trial landscape are also addressed. In the second part, the concept of multispecific antibody formats, notably MuTICEMs (Multispecific Targeted Immune Cell Engagers & Modulators), as a possible answer to current immunotherapy limitations is investigated. We believe it could be the next step to take for cancer immunotherapy research and expose why bioconjugation chemistry might play a key role in these future developments.

Immunotherapy for glioblastoma: the promise of combination strategies

Glioblastoma (GBM) treatment has remained almost unchanged for more than 20 years. The current standard of care involves surgical resection (if possible) followed by concomitant radiotherapy and chemotherapy. In recent years, immunotherapy strategies have revolutionized the treatment of many cancers, increasing the hope for GBM therapy. However, mostly due to the high, multifactorial immunosuppression occurring in the microenvironment, the poor knowledge of the neuroimmune system and the presence of the blood-brain barrier, the efficacy of immunotherapy in GBM is still low. Recently, new strategies for GBM treatments have employed immunotherapy combinations and have provided encouraging results in both preclinical and clinical studies. The lessons learned from clinical trials highlight the importance of tackling different arms of immunity. In this review, we aim to summarize the preclinical evidence regarding combination immunotherapy in terms of immune and survival benefits for GBM management. The outcomes of recent studies assessing the combination of different classes of immunotherapeutic agents (e.g., immune checkpoint blockade and vaccines) will be discussed. Finally, future strategies to ameliorate the efficacy of immunotherapy and facilitate clinical translation will be provided to address the unmet medical needs of GBM.

Myeloid-Derived Suppressive Cell Expansion Promotes Melanoma Growth and Autoimmunity by Inhibiting CD40/IL27 Regulation in Macrophages

The relationship between cancer and autoimmunity is complex. However, the incidence of solid tumors such as melanoma has increased significantly among patients with previous or newly diagnosed systemic autoimmune disease (AID). At the same time, immune checkpoint blockade (ICB) therapy of cancer induces de novo autoinflammation and exacerbates underlying AID, even without evident antitumor responses. Recently, systemic lupus erythematosus (SLE) activity was found to drive myeloid-derived suppressor cell (MDSC) formation in patients, a known barrier to healthy immune surveillance and successful cancer immunotherapy. Cross-talk between MDSCs and macrophages generally drives immune suppressive activity in the tumor microenvironment. However, it remains unclear how peripheral pregenerated MDSC under chronic inflammatory conditions modulates global macrophage immune functions and the impact it could have on existing tumors and underlying lupus nephritis. Here we show that pathogenic expansion of SLE-generated MDSCs by melanoma drives global macrophage polarization and simultaneously impacts the severity of lupus nephritis and tumor progression in SLE-prone mice. Molecular and functional data showed that MDSCs interact with autoimmune macrophages and inhibit cell surface expression of CD40 and the production of IL27. Moreover, low CD40/IL27 signaling in tumors correlated with high tumor-associated macrophage infiltration and ICB therapy resistance both in murine and human melanoma exhibiting active IFNγ signatures. These results suggest that preventing global macrophage reprogramming induced by MDSC-mediated inhibition of CD40/IL27 signaling provides a precision melanoma immunotherapy strategy, supporting an original and advantageous approach to treat solid tumors within established autoimmune landscapes. SIGNIFICANCE: Myeloid-derived suppressor cells induce macrophage reprogramming by suppressing CD40/IL27 signaling to drive melanoma progression, simultaneously affecting underlying autoimmune disease and facilitating resistance to immunotherapy within preexisting autoimmune landscapes.

Radiation Augments the Local Anti-Tumor Effect of In Situ Vaccine With CpG-Oligodeoxynucleotides and Anti-OX40 in Immunologically Cold Tumor Models

Introduction

Combining CpG oligodeoxynucleotides with anti-OX40 agonist antibody (CpG+OX40) is able to generate an effective in situ vaccine in some tumor models, including the A20 lymphoma model. Immunologically "cold" tumors, which are typically less responsive to immunotherapy, are characterized by few tumor infiltrating lymphocytes (TILs), low mutation burden, and limited neoantigen expression. Radiation therapy (RT) can change the tumor microenvironment (TME) of an immunologically "cold" tumor. This study investigated the effect of combining RT with the in situ vaccine CpG+OX40 in immunologically "cold" tumor models.

Methods

Mice bearing flank tumors (A20 lymphoma, B78 melanoma or 4T1 breast cancer) were treated with combinations of local RT, CpG, and/or OX40, and response to treatment was monitored. Flow cytometry and quantitative polymerase chain reaction (qPCR) experiments were conducted to study differences in the TME, secondary lymphoid organs, and immune activation after treatment.

Results

An in situ vaccine regimen of CpG+OX40, which was effective in the A20 model, did not significantly improve tumor response or survival in the "cold" B78 and 4T1 models, as tested here. In both models, treatment with RT prior to CpG+OX40 enabled a local response to this in situ vaccine, significantly improving the anti-tumor response and survival compared to RT alone or CpG+OX40 alone. RT increased OX40 expression on tumor infiltrating CD4+ non-regulatory T cells. RT+CpG+OX40 increased the ratio of tumor-infiltrating effector T cells to T regulatory cells and significantly increased CD4+ and CD8+ T cell activation in the tumor draining lymph node (TDLN) and spleen.

Conclusion

RT significantly improves the local anti-tumor effect of the in situ vaccine CpG+OX40 in immunologically "cold", solid, murine tumor models where RT or CpG+OX40 alone fail to stimulate tumor regression.

Soluble CD40 Levels in Plasma Are Associated with Cardiovascular Disease and in Carotid Plaques with a Vulnerable Phenotype

BACKGROUND AND PURPOSE

CD40 and CD40 ligand (CD40L) are costimulatory molecules of the tumor necrosis factor receptor superfamily and well known for their involvement in inflammatory diseases: atherosclerotic mouse models with disrupted CD40 signalling develop lesions of reduced size with a more stable plaque profile. This study investigated the potential of plasma and intraplaque levels of CD40 and CD40L as markers for cardiovascular disease (CVD) in humans and their association with plaque stability.

METHODS

Soluble CD40 and CD40L (sCD40L) were measured in plasma in 1,437 subjects from The SUrrogate markers for Micro- and Macro-vascular hard endpoints for Innovative diabetes Tools (SUMMIT) cohort. Intra-plaque levels of sCD40 and sCD40L were measured in atherosclerotic plaque homogenates from 199 subjects of the Carotid Plaque Imaging Project (CPIP) cohort.

RESULTS

Both plasma sCD40 and sCD40L levels were elevated in individuals with prevalent stroke, while sCD40 levels also were higher in individuals with a prior acute myocardial infarction. Plasma levels of sCD40 correlated with carotid intima-media thickness and total carotid plaque area and were associated with risk of cardiovascular events over a 3-year follow-up period. Intra-plaque levels of sCD40 and sCD40L were associated with plaque components characteristic for plaque vulnerability and extracellular matrix remodelling.

CONCLUSIONS

Higher plasma sCD40 and sCD40L levels are associated with prevalent CVD. Plasma sCD40 levels also correlate with the severity of carotid atherosclerosis and predict future cardiovascular events, while intra-plaque levels correlate with a vulnerable plaque phenotype. Our findings thus demonstrate that elevated levels of sCD40 and sCD40L are markers of CVD.

Bringing Macrophages to the Frontline against Cancer: Current Immunotherapies Targeting Macrophages

Macrophages are found in all tissues and display outstanding functional diversity. From embryo to birth and throughout adult life, they play critical roles in development, homeostasis, tissue repair, immunity, and, importantly, in the control of cancer growth. In this review, we will briefly detail the multi-functional, protumoral, and antitumoral roles of macrophages in the tumor microenvironment. Our objective is to focus on the ever-growing therapeutic opportunities, with promising preclinical and clinical results developed in recent years, to modulate the contribution of macrophages in oncologic diseases. While the majority of cancer immunotherapies target T cells, we believe that macrophages have a promising therapeutic potential as tumoricidal effectors and in mobilizing their surroundings towards antitumor immunity to efficiently limit cancer progression.

CD40 agonist-induced IL-12p40 potentiates hepatotoxicity

Background

CD40 is a compelling target for cancer immunotherapy, however, attempts to successfully target this pathway have consistently been hampered by dose-limiting toxicity issues in the clinic that prevents the administration of efficacious doses.

Methods

Here, using cytokine and cytokine receptor depletion strategies in conjunction with a potent CD40 agonist, we investigated mechanisms underlying the two primary sources of CD40 agonist-associated toxicity, hepatotoxicity and cytokine release syndrome (CRS).

Results

We demonstrate that CD40 agonist -induced hepatotoxicity and CRS are mechanistically independent. Historical data have supported a role for interleukin-6 (IL-6) in CRS-associated wasting, however, our findings instead show that an inflammatory cytokine network involving TNF, IL-12p40, and IFNγ underlie this process. Deficiency of TNF or IFNγ did not influence CD40-induced hepatitis however loss of IL-12p40 significantly decreased circulating concentrations of liver enzymes and reduced the frequency of activated CD14⁺MHCII⁺ myeloid cells in the liver, indicating a role for IL-12p40 in liver pathology.

Conclusions

As clinical research programs aim to circumnavigate toxicity concerns while maintaining antitumor efficacy it will be essential to understand which features of CD40 biology mediate antitumor function to develop both safe and efficacious agonists.

The Role of Macrophages in Cancer Development and Therapy

Macrophages are critical mediators of tissue homeostasis and influence various aspects of immunity. Tumor-associated macrophages are one of the main cellular components of the tumor microenvironment. Depending on their activation status, macrophages can exert a dual influence on tumorigenesis by either antagonizing the cytotoxic activity of immune cells or, less frequently, by enhancing antitumor responses. In most situations, TAMs suppress T cell recruitment and function or regulate other aspects of tumor immunity. The importance of TAMs targeting in cancer therapy is derived from the strong association between the high infiltration of TAMs in the tumor tissue with poor patient prognosis. Several macrophage-targeting approaches in anticancer therapy are developed, including TAM depletion, inhibition of new TAM differentiation, or re-education of TAM activation for cancer cell phagocytosis. In this review, we will describe the role of TAMs in tumor development, including such aspects as protumorigenic inflammation, immune suppression, neoangiogenesis, and enhancement of tissue invasion and distant metastasis. Furthermore, we will discuss therapeutic approaches that aim to deplete TAMs or, on the contrary, re-educate TAMs for cancer cell phagocytosis and antitumor immunity.

Combined Effects of Myeloid Cells in the Neuroblastoma Tumor Microenvironment

Despite multimodal treatment, survival chances for high-risk neuroblastoma patients remain poor. Immunotherapeutic approaches focusing on the activation and/or modification of host immunity for eliminating tumor cells, such as chimeric antigen receptor (CAR) T cells, are currently in development, however clinical trials have failed to reproduce the preclinical results. The tumor microenvironment is emerging as a major contributor to immune suppression and tumor evasion in solid cancers and thus has to be overcome for therapies relying on a functional immune response. Among the cellular components of the neuroblastoma tumor microenvironment, suppressive myeloid cells have been described as key players in inhibition of antitumor immune responses and have been shown to positively correlate with more aggressive disease, resistance to treatments, and overall poor prognosis. This review article summarizes how neuroblastoma-driven inflammation induces suppressive myeloid cells in the tumor microenvironment and how they in turn sustain the tumor niche through suppressor functions, such as nutrient depletion and generation of oxidative stress. Numerous preclinical studies have suggested a range of drug and cellular therapy approaches to overcome myeloid-derived suppression in neuroblastoma that warrant evaluation in future clinical studies.

Targeting Innate Immunity in Cancer Therapy

The majority of current cancer immunotherapy strategies target and potentiate antitumor adaptive immune responses. Unfortunately, the efficacy of these treatments has been limited to a fraction of patients within a subset of tumor types, with an aggregate response rate of approximately 20% to date across all malignancies. The success of therapeutic inhibition of programmed death protein 1 (PD-1), protein death ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) with immune checkpoint inhibitors (ICI) has been limited to “hot” tumors characterized by preexisting T cell infiltration, whereas “cold” tumors, which lack T cell infiltration, have not achieved durable benefit. There are several mechanisms by which “cold” tumors fail to generate spontaneous immune infiltration, which converge upon the generation of an immunosuppressive tumor microenvironment (TME). The role of the innate immune system in tumor immunosurveillance and generation of antitumor immune responses has been long recognized. In recent years, novel strategies to target innate immunity in cancer therapy have emerged, including therapeutic stimulation of pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs); the DNA sensing cGAS/STING pathway; nucleotide-binding oligomerization domain-like receptors (NLRs), such as NLRP3; and the retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs). In addition, therapeutic modulation of key innate immune cell types, such as macrophages and natural killer cells, has been investigated. Herein, we review therapeutic approaches to activate innate immunity within the TME to enhance antitumor immune responses, with the goal of disease eradication in “cold” tumors. In addition, we discuss rational immune-oncology combination strategies that activate both innate and adaptive immunity, with the potential to enhance the efficacy of current immunotherapeutic approaches.

Myeloid-like γδ T cell subset in the immune response to an experimental Rift Valley fever vaccine in sheep

γδ T cells are a numerically significant subset of immune cells in ruminants, where they may comprise up to 70 % of all peripheral blood mononuclear cells (PBMCs) in young animals and 25 % in adults. These cells can be activated through traditional TCR-dependent mechanisms, or alternatively in a TCR-independent manner by pattern recognition receptors and have been shown to uptake antigen, as well as process and present it to αβ T cells. We have identified a novel CD11b+ subset of γδ T cells in normal sheep peripheral blood. An increase in the frequency of these cells in sheep peripheral blood in response to immunization with an experimental recombinant subunit Rift Valley fever (RVF) vaccine was observed. However, injection of the vaccine adjuvant ISA-25VG alone without the recombinant RVF virus antigens demonstrated the same effect, pointing to an antigen-independent innate immune function of CD11b+ γδ T cells in response to the adjuvant. In vitro studies showed repeatable increases of CD11b-, CD14-, CD86-, CD40-, CD72-, and IFNγ- expressing γδ T cells in PBMCs after 24 h of incubation in the absence of a mitogen. Moreover, the majority of these myeloid-like γδ T cells were demonstrated to process exogenous antigen even in the absence of mitogen. ConA activation increased CD25- and MHCII- expression in γδ T cells, but not the myeloid associated receptors CD14 or CD11b or co-stimulatory molecules such as CD86 and CD40. Considering the role of CD11b and CD14 in the activation of innate immunity, we hypothesize that this subpopulation of sheep γδ T cells may function as innate antigen presenting and pro-inflammatory cells during immune responses. The results presented here also suggest that stress molecules and/or damage-associated molecular patterns may be involved in triggering antigen presenting and pro-inflammatory functions of γδ T cells, given their appearance in vitro in the absence of specific stimulation. Taken together, these data suggest that the early appearance of γδ T cells following adjuvant administration and their possible role in early activation of αβ T cell subsets may non-specifically contribute to augmented innate immunity and may promote strong initiation of the adaptive immune response to vaccines in general.

Pathology of macrophage activation syndrome in humanized NSGS mice

"Humanized" immunodeficient mice generated via the transplantation of CD34+ human hematopoietic stem cells (hHSC) are an important preclinical model system. The triple transgenic NOD.Cg-Prkdc^scidIl2rg^tm1Wjl Tg(CMV-IL3,CSF2,KITLG)1Eav/MloySzJ (NSGS) mouse line is increasingly used as recipient for CD34+ hHSC engraftment. NSGS mice combine the features of the highly immunodeficient NSG mice with transgenic expression of the human myeloid stimulatory cytokines GM-CSF, IL-3, and Kit ligand. While generating humanized NSGS (huNSGS) mice from two independent cohorts, we encountered a fatal macrophage activation syndrome (MAS)-like phenotype resulting from the transplantation of CD34+ hHSC. huNSGS mice exhibiting this phenotype declined clinically starting at approximately 10 weeks following CD34+ hHSC engraftment, with all mice requiring euthanasia by 16 weeks. Gross changes comprised small, irregular liver, splenomegaly, cardiomegaly, and generalized pallor. Hematological abnormalities included severe thrombocytopenia and anemia. Pathologically, huNSGS spontaneously developed a disseminated histiocytosis with infiltrates of activated macrophages and hemophagocytosis predominantly affecting the liver, spleen, bone marrow, and pancreas. The infiltrates were chimeric with a mixture of human and mouse macrophages. Immunohistochemistry suggested activation of the inflammasome in both human and murine macrophages. Active Epstein-Barr virus infection was not a feature. Although the affected mice exhibited robust chimerism of the spleen and bone marrow, the phenotype often developed in the face of low chimerism of the peripheral blood. Given the high penetrance and early lethality associated with the MAS-like phenotype here described, we urge caution when considering the use of huNSGS mice for the development of long-term studies.

Reprogramming the tumour microenvironment by radiotherapy: implications for radiotherapy and immunotherapy combinations

Radiotherapy (RT) is a highly effective anti-cancer therapy delivered to around 50-60% of patients. It is part of therapy for around 40% of cancer patients who are cured of their disease. Until recently, the focus of this anti-tumour efficacy has been on the direct tumour cytotoxicity and RT-induced DNA damage. Recently, the immunomodulatory effects of RT on the tumour microenvironment have increasingly been recognized. There is now intense interest in potentially using RT to induce an anti-tumour immune response, which has led to rethinking into how the efficacy of RT could be further enhanced. Following the breakthrough of immune check point inhibitors (ICIs), a new era of immuno-oncology (IO) agents has emerged and established immunotherapy as a routine part of cancer treatment. Despite ICI improving outcomes in many cancer types, overall durable responses occur in only a minority of patients. The immunostimulatory effects of RT make combinations with ICI attractive to potentially amplify anti-tumour immunity resulting in increased tumour responses and improved outcomes. In contrast, tumours with profoundly immunosuppressive tumour microenvironments, dominated by myeloid-derived cell populations, remain a greater clinical challenge and RT may potentially further enhance the immunosuppression. To harness the full potential of RT and IO agent combinations, further insights are required to enhance our understanding of the role these immunosuppressive myeloid populations play, how RT influences these populations and how they may be therapeutically manipulated in combination with RT to improve outcomes further. These are exciting times with increasing numbers of IO targets being discovered and IO agents undergoing clinical evaluation. Multidisciplinary research collaborations will be required to establish the optimal parameters for delivering RT (target volume, dose and fractionation) in combination with IO agents, including scheduling to achieve maximal therapeutic efficacy.

"Re-educating" Tumor Associated Macrophages as a Novel Immunotherapy Strategy for Neuroblastoma

Neuroblastoma is the most common extracranial pediatric tumor and often presents with metastatic disease, and patients with high-risk neuroblastoma have survival rates of ~50%. Neuroblastoma tumorigenesis is associated with the infiltration of various types of immune cells, including myeloid derived suppressor cells, tumor associated macrophages (TAMs), and regulatory T cells, which foster tumor growth and harbor immunosuppressive functions. In particular, TAMs predict poor clinical outcomes in neuroblastoma, and among these immune cells, TAMs with an M2 phenotype comprise an immune cell population that promotes tumor metastasis, contributes to immunosuppression, and leads to failure of radiation or checkpoint inhibitor therapy. This review article summarizes the role of macrophages in tumor angiogenesis, metastasis, and immunosuppression in neuroblastoma and discusses the recent advances in "macrophage-targeting strategies" in neuroblastoma with a focus on three aspects: (1) inhibition of macrophage recruitment, (2) targeting macrophage survival, and (3) reprogramming of macrophages into an immunostimulatory phenotype.

Dendritic cell vaccination and CD40-agonist combination therapy licenses T cell-dependent antitumor immunity in a pancreatic carcinoma murine model

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is notoriously resistant to treatment including checkpoint-blockade immunotherapy. We hypothesized that a bimodal treatment approach consisting of dendritic cell (DC) vaccination to prime tumor-specific T cells, and a strategy to reprogram the desmoplastic tumor microenvironment (TME) would be needed to break tolerance to these pancreatic cancers. As a proof-of-concept, we investigated the efficacy of combined DC vaccination with CD40-agonistic antibodies in a poorly immunogenic murine model of PDAC. Based on the rationale that mesothelioma and pancreatic cancer share a number of tumor associated antigens, the DCs were loaded with either pancreatic or mesothelioma tumor lysates.

METHODS

Immune-competent mice with subcutaneously or orthotopically growing KrasG12D/+;Trp53R172H/+;Pdx-1-Cre (KPC) PDAC tumors were vaccinated with syngeneic bone marrow-derived DCs loaded with either pancreatic cancer (KPC) or mesothelioma (AE17) lysate and consequently treated with FGK45 (CD40 agonist). Tumor progression was monitored and immune responses in TME and lymphoid organs were analyzed using multicolor flow cytometry and NanoString analyzes.

RESULTS

Mesothelioma-lysate loaded DCs generated cross-reactive tumor-antigen-specific T-cell responses to pancreatic cancer and induced delayed tumor outgrowth when provided as prophylactic vaccine. In established disease, combination with stimulating CD40 antibody was necessary to improve survival, while anti-CD40 alone was ineffective. Extensive analysis of the TME showed that anti-CD40 monotherapy did improve CD8 +T cell infiltration, but these essential effector cells displayed hallmarks of exhaustion, including PD-1, TIM-3 and NKG2A. Combination therapy induced a strong change in tumor transcriptome and mitigated the expression of inhibitory markers on CD8 +T cells.

CONCLUSION

These results demonstrate the potency of DC therapy in combination with CD40-stimulation for the treatment of pancreatic cancer and provide directions for near future clinical trials.

The unique immune microenvironment of liver metastases: Challenges and opportunities

Liver metastases from gastrointestinal and non-gastrointestinal malignancies remain a major cause of cancer-related mortality and a major clinical challenge. The liver has unique properties that facilitate metastatic expansion, including a complex immune system that evolved to dampen immunity to neoantigens entering the liver from the gut, through the portal circulation. In this review, we describe the unique microenvironment encountered by cancer cells in the liver, focusing on elements of the innate and adaptive immune response that can act as a double-edge sword, contributing to the elimination of cancer cells on the one hand and promoting their survival and growth, on the other. We discuss this microenvironment in a clinical context, particularly for colorectal carcinoma, and highlight how a better understanding of the role of the microenvironment has spurred an intense effort to develop novel and innovative strategies for targeting liver metastatic disease, some of which are currently being tested in the clinic.

The dark side of immunotherapy: pancreatic cancer

Since the journal Science deemed cancer immunotherapy as the "breakthrough of the year" in 2014, there has been an explosion of clinical trials involving immunotherapeutic approaches that, in the last decade - thanks also to the renaissance of the immunosurveillance theory (renamed the three Es theory) - have been continuously and successfully developed. In the latest update of the development of the immuno-oncology drug pipeline, published last November by Nature Review Drug Discovery, it was clearly reported that the immunoactive drugs under study almost doubled in just two years. Of the different classes of passive and active immunotherapies, "cell therapy" is the fastest growing. The aim of this review is to discuss the preclinical and clinical studies that have focused on different immuno-oncology approaches applied to pancreatic cancer, which we assign to the "dark side" of immunotherapy, in the sense that it represents one of the solid tumors showing less response to this type of therapeutic strategy.

The Hexavalent CD40 Agonist HERA-CD40L Induces T-Cell-mediated Antitumor Immune Response Through Activation of Antigen-presenting Cells

CD40 ligand (TNFSF5/CD154/CD40L), a member of the tumor necrosis factor (TNF) superfamily is a key regulator of the immune system. The cognate receptor CD40 (TNFRSF5) is expressed broadly on antigen-presenting cells and many tumor types, and has emerged as an attractive target for immunologic cancer treatment. Most of the CD40 targeting drugs in clinical development are antibodies which display some disadvantages: their activity typically depends on Fcγ receptor-mediated crosslinking, and depletion of CD40-expressing immune cells by antibody-dependent cellular cytotoxicity compromises an efficient antitumor response. To overcome the inadequacies of antibodies, we have developed the hexavalent receptor agonist (HERA) Technology. HERA compounds are fusion proteins composed of 3 receptor binding domains in a single chain arrangement, linked to an Fc-silenced human IgG1 thereby generating a hexavalent molecule. HERA-CD40L provides efficient receptor agonism on CD40-expressing cells and, importantly, does not require FcγR-mediated crosslinking. Strong activation of NFκB signaling was observed upon treatment of B cells with HERA-CD40L. Monocyte treatment with HERA-CD40L promoted differentiation towards the M1 spectrum and repolarization of M2 spectrum macrophages towards the M1 spectrum phenotype. Treatment of in vitro co-cultures of T and B cells with HERA-CD40L-triggered robust antitumor activation of T cells, which depended upon direct interaction with B cells. In contrast, bivalent anti-CD40 antibodies and trivalent soluble CD40L displayed weak activity which critically depended on crosslinking. In vivo, a murine surrogate of HERA-CD40L-stimulated clonal expansion of OT-I-specific murine CD8 T cells and showed single agent antitumor activity in the CD40 syngeneic MC38-CEA mouse model of colorectal cancer, suggesting an involvement of the immune system in controlling tumor growth. We conclude that HERA-CD40L is able to establish robust antitumor immune responses both in vitro and in vivo.

Concepts for agonistic targeting of CD40 in immuno-oncology

TNF Receptor Superfamily (TNF-R-SF) signaling is a structurally well-defined event that requires proper receptor clustering and trimerization. While the TNF-SF ligands naturally exist as trivalent functional units, the receptors are usually separated on the cell surface. Critically, receptor assembly into functional trimeric signaling complexes occurs through binding of the natural ligand unit. TNF-R-SF members, including CD40, have been key immunotherapeutic targets for over 20 years. CD40, expressed by antigen-presenting cells, endothelial cells, and many tumors, plays a fundamental role in connecting innate and adaptive immunity. The multiple investigated strategies to induce CD40 signaling can be broadly grouped into antibody-based or CD40L-based approaches. Currently, seven different antibodies and one CD40L-based hexavalent fusion protein are in active clinical trials. In this review, we describe the biology and structural properties of CD40, requirements for agonistic signal transduction through CD40 and summarize current attempts to exploit the CD40 signaling pathway for the treatment of cancer.

CD40 Agonist Antibodies in Cancer Immunotherapy

CD40 is a cell-surface member of the TNF (tumor necrosis factor) receptor superfamily. Upon activation, CD40 can license dendritic cells to promote antitumor T cell activation and re-educate macrophages to destroy tumor stroma. Numerous agonist CD40 antibodies of varying formulations have been evaluated in the clinic and found to be tolerable and feasible. Administration is associated with mild to moderate (but transient) cytokine release syndrome, readily managed in the outpatient setting. Antitumor activity with or without anti-CTLA4 monoclonal antibody (mAb) therapy has been observed in patients with melanoma, and major tumor regressions have been observed in patients with pancreatic cancer, mesothelioma, and other tumors in combination with chemotherapy. In a recent study of chemotherapy plus CD40 mAb, with or without PD-1 mAb, the objective response rate in patients with untreated, metastatic pancreatic cancer was >50%. Mechanistically, the combination of chemotherapy followed by CD40 mAb functions as an in situ vaccine; in addition, destruction of stroma by CD40-activated macrophages may enhance chemotherapy delivery. Evidence to date suggests that CD40 activation is a critical and nonredundant mechanism to convert so-called cold tumors to hot ones (with prominent tumor infiltration of T cells), sensitizing them to checkpoint inhibition.

The Use of Anti-CD40 mAb in Cancer

Immunomodulatory monoclonal antibody (mAb) therapy is at the forefront of developing cancer therapeutics with numerous targeted agents proving highly effective in selective patients at stimulating protective host immunity, capable of eradicating established tumours and leading to long-term disease-free states. The cell surface marker CD40 is expressed on a range of immune cells and transformed cells in malignant states whose signalling plays a critical role in modulating adaptive immune responses. Anti-CD40 mAb therapy acts via multiple mechanisms to stimulate anti-tumour immunity across a broad range of lymphoid and solid malignancies. A wealth of preclinical research in this field has led to the successful development of multiple anti-CD40 mAb agents that have shown promise in early-phase clinical trials. Significant progress has been made to enhance the engagement of antibodies with immune effectors through their interactions with Fcγ receptors (FcγRs) by the process of Fc engineering. As more is understood about how to best optimise these agents, principally through the fine-tuning of mAb structure and choice of synergistic partnerships, our ability to generate robust, clinically beneficial anti-tumour activity will form the foundation for the next generation of cancer therapeutics.

Experimental Combined Immunotherapy of Tumours with Major Histocompatibility Complex Class I Downregulation

Combined immunotherapy constitutes a novel, advanced strategy in cancer treatment. In this study, we investigated immunotherapy in the mouse TC-1/A9 model of human papillomavirus type 16 (HPV16)-associated tumors characterized by major histocompatibility complex class I (MHC-I) downregulation. We found that the induction of a significant anti-tumor response required a combination of DNA vaccination with the administration of an adjuvant, either the synthetic oligodeoxynucleotide ODN1826, carrying immunostimulatory CpG motifs, or α-galactosylceramide (α-GalCer). The most profound anti-tumor effect was achieved when these adjuvants were applied in a mix with a one-week delay relative to DNA immunization. Combined immunotherapy induced tumor infiltration with various subsets of immune cells contributing to tumor regression, of which cluster of differentiation (CD) 8⁺ T cells were the predominant subpopulation. In contrast, the numbers of tumor-associated macrophages (TAMs) were not markedly increased after immunotherapy but in vivo and in vitro results showed that they could be repolarized to an anti-tumor M1 phenotype. A blockade of T cell immunoglobulin and mucin-domain containing-3 (Tim-3) immune checkpoint had a negligible effect on anti-tumor immunity and TAMs repolarization. Our results demonstrate a benefit of combined immunotherapy comprising the activation of both adaptive and innate immunity in the treatment of tumors with reduced MHC-I expression.

Role of MDA5 and interferon-I in dendritic cells for T cell expansion by anti-tumor peptide vaccines in mice

Cytotoxic T lymphocytes (CTLs) are effective components of the immune system capable of destroying tumor cells. Generation of CTLs using peptide vaccines is a practical approach to treat cancer. We have previously described a peptide vaccination strategy that generates vast numbers of endogenous tumor-reactive CTLs after two sequential immunizations (prime-boost) using poly-ICLC adjuvant, which stimulates endosomal toll-like receptor 3 (TLR3) and cytoplasmic melanoma differentiation antigen 5 (MDA5). Dendritic cells (DCs) play an important role not only in antigen presentation but are critical in generating costimulatory cytokines that promote CTL expansion. Poly-ICLC was shown to be more effective than poly-IC in generating type-I interferon (IFN-I) in various DC subsets, through its enhanced ability to escape the endosomal compartment and stimulate MDA5. In our system, IFN-I did not directly function as a T cell costimulatory cytokine, but enhanced CTL expansion through the induction of IL15. With palmitoylated peptide vaccines, CD8α+ DCs were essential for peptide crosspresentation. For vaccine boosts, non-professional antigen-presenting cells were able to present minimal epitope peptides, but DCs were still required for CTL expansions through the production of IFN-I mediated by poly-ICLC. Overall, these results clarify the roles of DCs, TLR3, MDA5, IFN-I and IL15 in the generation of vast and effective antitumor CTL responses using peptide and poly-IC vaccines.

MicroRNA: Dynamic Regulators of Macrophage Polarization and Plasticity

The ability of a healthy immune system to clear the plethora of antigens it encounters incessantly relies on the enormous plasticity displayed by the comprising cell types. Macrophages (MΦs) are crucial member of the mononuclear phagocyte system (MPS) that constantly patrol the peripheral tissues and are actively recruited to the sites of injury and infection. In tissues, infiltrating monocytes replenish MΦ. Under the guidance of the local micro-milieu, MΦ can be activated to acquire specialized functional phenotypes. Similar to T cells, functional polarization of macrophage phenotype viz., inflammatory (M1) and reparative (M2) is proposed. Equipped with diverse toll-like receptors (TLRs), these cells of the innate arm of immunity recognize and phagocytize antigens and secrete cytokines that activate the adaptive arm of the immune system and perform key roles in wound repair. Dysregulation of MΦ plasticity has been associated with various diseases and infection. MicroRNAs (miRNAs) have emerged as critical regulators of transcriptome output. Their importance in maintaining health, and their contribution toward disease, encompasses virtually all aspects of human biology. Our understanding of miRNA-mediated regulation of MΦ plasticity and polarization can be utilized to modulate functional phenotypes to counter their role in the pathogenesis of numerous disease, including cancer, autoimmunity, periodontitis, etc. Here, we provide an overview of current knowledge regarding the role of miRNA in shaping MΦ polarization and plasticity through targeting of various pathways and genes. Identification of miRNA biomarkers of diagnostic/prognostic value and their therapeutic potential by delivery of miRNA mimics or inhibitors to dynamically alter gene expression profiles in vivo is highlighted.

Nanomedicine Strategies to Target Tumor-Associated Macrophages

In recent years, the influence of the tumor microenvironment (TME) on cancer progression has been better understood. Macrophages, one of the most important cell types in the TME, exist in different subtypes, each of which has a different function. While classically activated M1 macrophages are involved in inflammatory and malignant processes, activated M2 macrophages are more involved in the wound-healing processes occurring in tumors. Tumor-associated macrophages (TAM) display M2 macrophage characteristics and support tumor growth and metastasis by matrix remodeling, neo-angiogenesis, and suppressing local immunity. Due to their detrimental role in tumor growth and metastasis, selective targeting of TAM for the treatment of cancer may prove to be beneficial in the treatment of cancer. Due to the plastic nature of macrophages, their activities may be altered to inhibit tumor growth. In this review, we will discuss the therapeutic options for the modulation and targeting of TAM. Different therapeutic strategies to deplete, inhibit recruitment of, or re-educate TAM will be discussed. Current strategies for the targeting of TAM using nanomedicine are reviewed. Passive targeting using different nanoparticle systems is described. Since TAM display a number of upregulated surface proteins compared to non-TAM, specific targeting using targeting ligands coupled to nanoparticles is discussed in detail.

Effective Combination of Innate and Adaptive Immunotherapeutic Approaches in a Mouse Melanoma Model

Most cancer immunotherapies include activation of either innate or adaptive immune responses. We hypothesized that the combined activation of both innate and adaptive immunity will result in better antitumor efficacy. We have previously shown the synergy of an agonistic anti-CD40 mAb (anti-CD40) and CpG-oligodeoxynucleotides in activating macrophages to induce tumor cell killing in mice. Separately, we have shown that a direct intratumoral injection of immunocytokine (IC), an anti-GD2 Ab linked to IL-2, can activate T and NK cells resulting in antitumor effects. We hypothesized that activation of macrophages with anti-CD40/CpG, and NK cells with IC, would cause innate tumor destruction, leading to increased presentation of tumor Ags and adaptive T cell activation; the latter could be further augmented by anti-CTLA-4 Ab to achieve tumor eradication and immunological memory. Using the mouse GD2⁺ B78 melanoma model, we show that anti-CD40/CpG treatment led to upregulation of T cell activation markers in draining lymph nodes. Anti-CD40/CpG + IC/anti-CTLA-4 synergistically induced regression of advanced s.c. tumors, resulting in cure of some mice and development of immunological memory against B78 and wild type B16 tumors. Although the antitumor effect of anti-CD40/CpG did not require T cells, the antitumor effect of IC/anti-CTLA-4 was dependent on T cells. The combined treatment with anti-CD40/CpG + IC/anti-CTLA-4 reduced T regulatory cells in the tumors and was effective against distant solid tumors and lung metastases. We suggest that a combination of anti-CD40/CpG and IC/anti-CTLA-4 should be developed for clinical testing as a potentially effective novel immunotherapy strategy.

Murine mesothelioma induces locally-proliferating IL-10(+)TNF-α(+)CD206(-)CX3CR1(+) M3 macrophages that can be selectively depleted by chemotherapy or immunotherapy

We used a murine model to monitor changes to myeloid cell subsets, i.e., myeloid-derived suppressor cells (MDSCs), M1 macrophages that secrete pro-inflammatory cytokines and express CD40 and CD80 and suppressive M2 macrophages that secrete anti-inflammatory cytokines and express CD206 and CX3CR1, during mesothelioma progression and during chemotherapy or immunotherapy-induced tumor regression. In vitro studies showed that mesothelioma-conditioned media generated CD206(-)CX3CR1(+)MCP-1(+)TGF-β(+) macrophages that induced T cell proliferation but prevented T cell IFNγ production. In vivo studies showed that co-inoculation of macrophages with mesothelioma cells led to faster tumor growth, and depleting macrophages using anti-F4/80 antibody induced tumor regression. Flow cytometry revealed increasing levels of different suppressive myeloid cells in lymphoid organs: MDSCs dominated bone marrow (BM) and spleens, M2 macrophages dominated tumor-draining lymph nodes (DLN) and a mixed IL-10(+)TNF-α(+)CD206(-)CX3CR1(+) M1/M2 (M3) macrophage subset dominated the mesothelioma microenvironment. Ki67 staining and cell cycle analysis showed that tumor-associated M1 and M3, but not M2, macrophages were proliferating in situ, with M1 cells arrested in the G1 phase while M3 cells progressed to mitosis. Immunohistochemistry showed that M1 and M3 cells were co-located supporting the hypothesis that M1 cells transition to M3 cells during proliferation. Gemcitabine reduced tumor-associated M3 and MDSCs, but not M2 macrophages, the latter likely contributing to the tumor outgrowth seen following treatment cessation. In contrast, IL-2/agonist anti-CD40 antibody therapy reduced M3 cells and polarized macrophages into M1 cells coinciding with tumor regression. These data show that myeloid cells, particularly M3 cells, represent a therapeutic target for the generation of antitumor immunity.

IFNγ and CCL2 Cooperate to Redirect Tumor-Infiltrating Monocytes to Degrade Fibrosis and Enhance Chemotherapy Efficacy in Pancreatic Carcinoma

Dense fibrosis and a robust macrophage infiltrate are key therapeutic barriers in pancreatic ductal adenocarcinoma (PDAC). CD40 activation can circumvent these barriers by inducing macrophages, originating from peripheral blood monocytes, to deplete fibrosis. The precise mechanism and therapeutic implications of this antifibrotic activity, though, remain unclear. Here, we report that IFNγ and CCL2 released systemically in response to a CD40 agonist cooperate to redirect a subset of Ly6C(+)CCR2(+)monocytes/macrophages to infiltrate tumors and deplete fibrosis. Whereas CCL2 is required for Ly6C(+)monocyte/macrophage infiltration, IFNγ is necessary for tumor-infiltrating monocytes/macrophages to shift the profile of matrix metalloproteinases (MMP) in tumors, leading to MMP-dependent fibrosis degradation. In addition, MMP13-dependent loss of extracellular matrix components induced by a CD40 agonist increased PDAC sensitivity to chemotherapy. Our findings demonstrate that fibrosis in PDAC is a bidirectional process that can be rapidly altered by manipulating a subset of tumor-infiltrating monocytes, leading to enhanced chemotherapy efficacy.

SIGNIFICANCE

We report that CD40 agonists improve chemotherapy efficacy in pancreatic carcinoma by redirecting tumor-infiltrating monocytes/macrophages to induce fibrosis degradation that is dependent on MMPs. These findings provide novel insight into the plasticity of monocytes/macrophages in cancer and their capacity to regulate fibrosis and modulate chemotherapy efficacy in pancreatic carcinoma.

Intratumoral injection of Ad-ISF35 (Chimeric CD154) breaks tolerance and induces lymphoma tumor regression

Ad-ISF35, an adenovirus vector encoding a membrane-bound engineered CD154 chimeric protein (ISF35), induces complete A20 lymphoma tumor regression in mice after intratumoral direct injection (IDI). Ad-ISF35 induced durable local and systemic antitumor responses associated with a rapid tumor infiltration of macrophages and neutrophils as well as increased levels of proinflammatory cytokines in the tumor microenvironment. Ad-ISF35 IDI transduced preferentially fibroblasts and macrophages present in the tumor microenvironment, and ISF35 protein expression was observed in only 0.25% of cells present in the tumor. Moreover, Ad-ISF35 IDI induced upregulation of CD40 in tumor and immune regulatory cells, including those that did not express ISF35, suggesting the presence of a strong bystander effect. These responses resulted in the generation of IFN-γ-secreting cytotoxic lymphocytes and the production of specific cytotoxic antibodies against lymphoma cells. Overall, cellular immune therapy based on ISF35 induced phenotypic changes in the tumor cells and tumor microenvironment that were associated with a break in tumor immune tolerance and a curative antitumor effect in this lymphoma mouse model. Our data highlight the potential activity that modulation of costimulatory signaling has in cancer therapy.

Bone marrow macrophages in Waldenström's macroglobulinemia: a report of four cases

It is well known that some B-cell lymphomas are accompanied by a prominent epithelioid cell response, caused by activated macrophages, such as marginal zone B-cell lymphoma of a mucosa-associated lymphoid tissue. We investigated six bone marrow samples from four cases of Waldenström's macroglobulinemia and report a unique observation that large conjugates of tumor cells around a macrophage were prominent in all cases, particularly in one case, the bone marrow of which contained increased CD163-positive macrophages. Mast cells were increased in all the samples, some of which seemed to be in close contact with tumor cells. We consider that the conjugates represented close interactions of tumor cells, macrophages, and mast cells by cell-to-cell contact. Three of the present cases showed a favorable course. On the other hand, one case suffered from severe anemia and thrombocytopenia due to hemophagocytic syndrome at the second admission and showed a severe clinical course. Clinicians should be aware of the risk of lymphoma-associated hemophagocytic syndrome in this low-grade lymphoma, although many of the patients with hemophagocytic syndrome in Japan have aggressive lymphomas such as diffuse large B-cell lymphoma.