Stimulation of natural killer cells with a CD137-specific antibody enhances trastuzumab efficacy in xenotransplant models of breast cancer

Anticalin® Proteins as Therapeutic Agents in Human Diseases

Anticalin proteins are an emerging class of clinical-stage biopharmaceuticals with high potential as an alternative to antibodies. Anticalin molecules are generated by combinatorial design from natural lipocalins, which are abundant plasma proteins in humans, and reveal a simple, compact fold dominated by a central β-barrel, supporting four structurally variable loops that form a binding site. Reshaping of this loop region results in Anticalin proteins that can recognize and tightly bind a wide range of medically relevant targets, from small molecules to peptides and proteins, as validated by X-ray structural analysis. Their robust format allows for modification in several ways, both as fusion proteins and by chemical conjugation, for example, to tune plasma half-life. Antagonistic Anticalin therapeutics have been developed for systemic administration (e.g., PRS-080: anti-hepcidin) or pulmonary delivery (e.g. PRS-060/AZD1402: anti-interleukin [IL]-4-Rα). Moreover, Anticalin proteins allow molecular formatting as bi- and even multispecific fusion proteins, especially in combination with antibodies that provide a second specificity. For example, PRS-343, which has recently entered clinical-stage development, combines an agonistic Anticalin targeting the costimulatory receptor 4-1BB with an antibody directed against the cancer antigen human epidermal growth factor receptor 2 (HER2), thus offering a novel treatment option in immuno-oncology.

Breast Cancer Immunotherapy: An Update

The immune system plays a major role in cancer surveillance. Harnessing its power to treat many cancers is now a reality that has led to cures in hopeless situations where no other solutions were available from traditional anticancer drugs. These spectacular achievements rekindled the oncology community's interest in extending the benefits to all cancers including breast cancer. The first section of this article reviews the biological foundations of the immune response to different subtypes of breast cancer and the ways cancer may overcome the immune attack leading to cancer disease. The second section is dedicated to the actual immune treatments including breast cancer vaccines, checkpoint inhibitors, monoclonal antibodies, and the "unconventional" immune role of chemotherapy.

Bispecific antibodies in cancer immunotherapy

Following the clinical success of immune checkpoint antibodies targeting CTLA-4, PD-1 or PD-L1 in cancer treatment, bispecific antibodies are now emerging as a growing class of immunotherapies with potential to further improve clinical efficacy and safety. We describe three classes of immunotherapeutic bispecific antibodies: (a) cytotoxic effector cell redirectors; (b) tumor-targeted immunomodulators; and (c) dual immunomodulators. Cytotoxic effector cell redirectors are dominated by T-cell redirecting compounds, bispecific compounds engaging a tumor-associated antigen and the T-cell receptor/CD3 complex, thereby redirecting T-cell cytotoxicity to malignant cells. This is the most established class of bispecific immunotherapies, with two compounds having reached the market and numerous compounds in clinical development. Tumor-targeted immunomodulators are bispecific compounds binding to a tumor-associated antigen and an immunomodulating receptor, such as CD40 or 4-1BB. Such compounds are usually designed to be inactive until binding the tumor antigen, thereby localizing immune stimulation to the tumor environment, while minimizing immune activation elsewhere. This is expected to induce powerful activation of tumor-specific T cells with reduced risk of immune-related adverse events. Finally, dual immunomodulators are bispecific compounds that bind two distinct immunomodulating targets, often combining targeting of PD-1 or PD-L1 with that of LAG-3 or TIM-3. The rationale is to induce superior tumor immunity compared to monospecific antibodies to the same targets. In this review, we describe each of these classes of bispecific antibodies, and present examples of compounds in development.

A Phase 1 Trial of CNDO-109-Activated Natural Killer Cells in Patients with High-Risk Acute Myeloid Leukemia

Natural killer (NK) cells are an emerging immunotherapy approach to acute myeloid leukemia (AML); however, the optimal approach to activate NK cells before adoptive transfer remains unclear. Human NK cells that are primed with the CTV-1 leukemia cell line lysate CNDO-109 exhibit enhanced cytotoxicity against NK cell-resistant cell lines. To translate this finding to the clinic, CNDO-109-activated NK cells (CNDO-109-NK cells) isolated from related HLA-haploidentical donors were evaluated in a phase 1 dose-escalation trial at doses of 3 × 10⁵ (n = 3), 1 × 10⁶ (n = 3), and 3 × 10⁶ (n = 6) cells/kg in patients with AML in first complete remission (CR1) at high risk for recurrence. Before CNDO-109-NK cell administration, patients were treated with lymphodepleting fludarabine/cyclophosphamide. CNDO-109-NK cells were well tolerated, and no dose-limiting toxicities were observed at the highest tested dose. The median relapse-free survival (RFS) by dose level was 105 (3 × 10⁵), 156 (1 × 10⁶), and 337 (3 × 10⁶) days. Two patients remained relapse-free in post-trial follow-up, with RFS durations exceeding 42.5 months. Donor NK cell microchimerism was detected on day 7 in 10 of 12 patients, with 3 patients having evidence of donor cells on day 14 or later. This trial establishes that CNDO-109-NK cells generated from related HLA haploidentical donors, cryopreserved, and then safely administered to AML patients with transient persistence without exogenous cytokine support. Three durable complete remissions of 32.6 to 47.6+ months were observed, suggesting additional clinical investigation of CNDO-109-NK cells for patients with myeloid malignancies, alone or in combination with additional immunotherapy strategies, is warranted.

Strategies to activate NK cells to prevent relapse and induce remission following hematopoietic stem cell transplantation

Natural killer (NK) cells are lymphocytes of innate immunity that respond to virus infected and tumor cells. After allogeneic transplantation, NK cells are the first reconstituting lymphocytes, but are dysfunctional. Manipulating this first wave of lymphocytes could be instrumental in reducing the 40% relapse rate following transplantation with reduced-intensity conditioning. NK cells express numerous activating and inhibitory receptors. Some recognize classical or nonclassical HLA class I ligands, others recognize class I-like ligands or unrelated ligands. Dominant in the NK-cell transplant literature are killer cell immunoglobulin-like receptors (KIRs), encoded on chromosome 19q. Inhibitory KIR recognition of the cognate HLA class I ligand is responsible for NK-cell education, which makes them tolerant of healthy cells, but responsive to unhealthy cells having reduced expression of HLA class I. KIR A and KIR B are functionally distinctive KIR haplotype groups that differ in KIR gene content. Allogeneic transplant donors having a KIR B haplotype and lacking a recipient HLA-C epitope provide protection against relapse from acute myeloid leukemia. Cytomegalovirus infection stimulates and expands a distinctive NK-cell population that expresses the NKG2C receptor and exhibits enhanced effector functions. These adaptive NK cells display immune memory and methylation signatures like CD8 T cells. As potential therapy, NK cells, including adaptive NK cells, can be adoptively transferred with, or without, agents such as interleukin-15 that promote NK-cell survival. Strategies combining NK-cell infusions with CD16-binding antibodies or immune engagers could make NK cells antigen specific. Together with checkpoint inhibitors, these approaches have considerable potential as anticancer therapies.

Augmentation of CD134 (OX40)-dependent NK anti-tumour activity is dependent on antibody cross-linking

CD134 (OX40) is a member of the tumour necrosis factor receptor superfamily (TNFRSF). It acts as a costimulatory receptor on T cells, but its role on NK cells is poorly understood. CD137, another TNFRSF member has been shown to enhance the anti-tumour activity of NK cells in various malignancies. Here, we examine the expression and function of CD134 on human and mouse NK cells in B-cell lymphoma. CD134 was transiently upregulated upon activation of NK cells in both species. In contrast to CD137, induction of CD134 on human NK cells was dependent on close proximity to, or cell-to-cell contact with, monocytes or T cells. Stimulation with an agonistic anti-CD134 mAb but not CD134 ligand, increased IFNγ production and cytotoxicity of human NK cells, but this was dependent on simultaneous antibody:Fcγ receptor binding. In complementary murine studies, intravenous inoculation with BCL1 lymphoma into immunocompetent syngeneic mice resulted in transient upregulation of CD134 on NK cells. Combination treatment with anti-CD20 and anti-CD134 mAb produced a synergistic effect with durable remissions. This therapeutic benefit was abrogated by NK cell depletion and in Fcγ chain -/- mice. Hence, anti-CD134 agonists may enhance NK-mediated anti-tumour activity in an Fcγ receptor dependent fashion.

Characterizing CD137 upregulation on NK cells in patients receiving monoclonal antibody therapy

Background

In the era of personalized cancer medicine, identifying techniques for effectively matching patients to efficacious treatments is a critical step in the treatment process. The advent of anti-cancer immunotherapies necessitates novel approaches to biomarker identification beyond traditional genomic profiling. One promising approach is incorporation of nomograms into treatment decisions. Nomograms are prediction tools, based on statistical modeling, designed to predict treatment outcomes. As a first step toward developing a nomogram, we conducted analyses to predict CD137 expression of natural killer cells after monoclonal antibody (mAb) treatment.

Patients and methods

Patient, tumor and immune characteristics were collected from 199 patients with breast cancer (N = 62), head/neck cancers (N = 46) and non-Hodgkin's lymphoma (NHL) (N = 91), who were receiving mAb therapy as part of clinical trials. The difference in CD137 expression before and after mAb therapy was assessed by flow cytometry. To evaluate those who respond to mAb therapy via increased CD137 expression, we applied classification and regression trees (CART), multivariable lasso regression tools and Random Forest.

Results

The CD137 expression was significantly different for each cancer type [mean (SD): Breast: 6.6 (6.5); Head/Neck: 11.0 (7.0); NHL: 7.5 (7.1), P < 0.0001]. For breast cancer and NHL, FcR polymorphism and baseline CD137 expression were significant predictors of increased CD137 expression; for head/neck cancer, FcR polymorphism and age were significant predictors of increased expression.

Conclusions

Our preliminary results suggest that FcR polymorphism, pre-treatment CD137 expression and age are significant predictors of CD137 upregulation in patients. This study demonstrates that the development of a nomogram for therapy response is feasible. Further work validating our models in an independent cohort will provide the next steps in developing a nomogram that may be used to individualize this therapeutic approach for patients (NCT01114256).

Resistance to anticancer immunity in cancer patients: potential strategies to reverse resistance

In the 1990s, the application of immunotherapy approaches to target cancer cells resulted in significant clinical responses in patients with advanced malignancies who were refractory to conventional therapies. While early immunotherapeutics were focused on T cell-mediated cytotoxic activity, subsequent efforts were centered on targeted antibody-mediated anticancer therapy. The initial success with antibody therapy encouraged further studies and, consequently, there are now more than 25 FDA-approved antibodies directed against a range of targets. Although both T cell and antibody therapies continue to result in significant clinical responses with minimal toxicity, a significant subset of patients does not respond to immunotherapy and another subset develops resistance following an initial response. This review is focused on describing examples showing that cancer resistance to immunotherapies indeed occurs. In addition, it reviews the mechanisms being used to overcome the resistance to immunotherapies by targeting the tumor cell directly and/or the tumor microenvironment.

Targeting immune checkpoints in breast cancer: an update of early results

The immune tumour microenvironment has been shown to play a crucial role in the development and progression of cancer. Expression of gene signatures, reflecting immune activation, and the presence of tumour-infiltrating lymphocytes were associated with favourable outcomes in HER2-positive and triple-negative breast cancer. Recently, immunotherapy with immune checkpoint blockade induced long-lasting responses and improved survival in hard-to-treat malignancies (ie, melanoma and non-small cell lung cancer) and are changing treatment paradigms in a variety of neoplastic diseases. Immune checkpoint blockade has been evaluated in breast cancer, particularly in the triple-negative subtype, with promising results observed in monotherapy or in combination with chemotherapy in the metastatic and neoadjuvant settings. However, identification of patients who are most likely to benefit from immune checkpoint blockade remains challenging, with many patients not responding to treatments and a significant financial cost. The combination of immune checkpoint blockade with conventional cancer treatments such as chemotherapy, radiotherapy, targeted therapies or with other immunotherapies is a promising strategy to potentiate its efficacy in breast cancer although further research is required to effectively identify who will respond to these immunotherapies. In this review we report the most recent results that emerged from trials testing immune checkpoint blockade and potential predictive biomarkers and emphasise the new strategies that are under clinical development in breast cancer.

Interplay between Natural Killer Cells and Anti-HER2 Antibodies: Perspectives for Breast Cancer Immunotherapy

Overexpression of the human epidermal growth factor receptor 2 (HER2) defines a subgroup of breast tumors with aggressive behavior. The addition of HER2-targeted antibodies (i.e., trastuzumab, pertuzumab) to chemotherapy significantly improves relapse-free and overall survival in patients with early-stage and advanced disease. Nonetheless, considerable proportions of patients develop resistance to treatment, highlighting the need for additional and co-adjuvant therapeutic strategies. HER2-specific antibodies can trigger natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity and indirectly enhance the development of tumor-specific T cell immunity; both mechanisms contributing to their antitumor efficacy in preclinical models. Antibody-dependent NK cell activation results in the release of cytotoxic granules as well as the secretion of pro-inflammatory cytokines (i.e., IFNγ and TNFα) and chemokines. Hence, NK cell tumor suppressive functions include direct cytolytic killing of tumor cells as well as the regulation of subsequent antitumor adaptive immunity. Albeit tumors with gene expression signatures associated to the presence of cytotoxic lymphocyte infiltrates benefit from trastuzumab-based treatment, NK cell-related biomarkers of response/resistance to HER2-specific therapeutic antibodies in breast cancer patients remain elusive. Several variables, including (i) the configuration of the patient NK cell repertoire; (ii) tumor molecular features (i.e., estrogen receptor expression); (iii) concomitant therapeutic regimens (i.e., chemotherapeutic agents, tyrosine kinase inhibitors); and (iv) evasion mechanisms developed by progressive breast tumors, have been shown to quantitatively and qualitatively influence antibody-triggered NK cell responses. In this review, we discuss possible interventions for restoring/enhancing the therapeutic activity of HER2 therapeutic antibodies by harnessing NK cell antitumor potential through combinatorial approaches, including immune checkpoint blocking/stimulatory antibodies, cytokines and toll-like receptor agonists.

Role of Cytotoxic Tumor-Infiltrating Lymphocytes in Predicting Outcomes in Metastatic HER2-Positive Breast Cancer: A Secondary Analysis of a Randomized Clinical Trial

Importance

Accumulating evidence indicates that tumor-infiltrating lymphocytes (TILs) are associated with clinical outcomes and may predict the efficacy of chemotherapy and human epidermal growth factor receptor 2 (HER2, encoded by the gene ERBB2)-targeted therapy in patients with HER2-positive breast cancer.

Objective

To investigate the role of TILs, particularly cytotoxic CD8+ T cells, in the prediction of outcomes in patients with HER2-positive metastatic breast cancer randomized to an antibody-based (trastuzumab) vs a small molecule-based (lapatinib) anti-HER2 therapy.

Design, Setting, and Participants

The Canadian Cancer Trials Group MA.31 phase 3 clinical trial accrued patients from 21 countries and randomized 652 with HER2-positive metastatic breast cancer to receive trastuzumab or lapatinib, in combination with a taxane, from January 17, 2008, through December 1, 2011. Patients had received no prior chemotherapy or HER2-targeted therapy in the metastatic setting. The median follow-up was 21.5 months (interquartile range, 14.3-31.0). The tumor tissue collected for primary diagnosis was used in this ad hoc substudy. Sections were scored for TILs on hematoxylin-eosin (H&E)-stained sections, and immunohistochemical analysis was performed to assess CD8, FOXP3, CD56, and programmed cell death protein 1 (PD-1) expression on stromal (sTILs) and intratumoral TILs. Data were analyzed from July 15, 2015, through July 27, 2016.

Interventions

Treatment with trastuzumab or lapatinib in combination with taxane chemotherapy (paclitaxel or docetaxel) for 24 weeks.

Main Outcomes and Measures

Prognostic effects of biomarkers were evaluated for progression-free survival by stratified univariate log-rank test with Kaplan-Meier curves and by multivariate Cox proportional hazards regression; predictive effects were examined with a test of interaction between treatment allocation and biomarker classification.

Results

Of the 647 treated women (mean [SD] age, 55.0 [10.8] years), 614 had tumor tissue samples scored for H&E sTILs and 427 for CD8 biomarker assessments. Overall H&E sTIL counts of greater than 5% (high) were present in 215 cases (35%) but did not show significant prognostic or predictive effects. Univariate stratified analyses detected a significant predictive effect on risk for progression with lapatinib compared with trastuzumab among patients with low CD8+ sTIL counts (observed hazard ratio, 2.94; 95% CI, 1.40-6.17; P = .003) and among those with high CD8+ sTIL counts (observed hazard ratio, 1.36; 95% CI, 1.05-1.75; P = .02), confirmed in stepwise multivariate analysis (interaction P = .04). Other immunohistochemistry biomarkers were not associated with prognostic or predictive effects.

Conclusions and Relevance

In this secondary analysis of a phase 3 randomized clinical trial, a low level of preexisting cytotoxic sTILs predicted the most benefit from an antibody- vs a small molecule-based drug against the same target.

Trial Registration

clinicaltrials.gov Identifier: NCT00667251.

Immunotherapy targeting 4-1BB: mechanistic rationale, clinical results, and future strategies

4-1BB (CD137, tumor necrosis factor receptor superfamily 9) is an inducible costimulatory receptor expressed on activated T and natural killer (NK) cells. 4-1BB ligation on T cells triggers a signaling cascade that results in upregulation of antiapoptotic molecules, cytokine secretion, and enhanced effector function. In dysfunctional T cells that have a decreased cytotoxic capacity, 4-1BB ligation demonstrates a potent ability to restore effector functions. On NK cells, 4-1BB signaling can increase antibody-dependent cell-mediated cytotoxicity. Agonistic monoclonal antibodies targeting 4-1BB have been developed to harness 4-1BB signaling for cancer immunotherapy. Preclinical results in a variety of induced and spontaneous tumor models suggest that targeting 4-1BB with agonist antibodies can lead to tumor clearance and durable antitumor immunity. Clinical trials of 2 agonist antibodies, urelumab and utomilumab, are ongoing. Despite initial signs of efficacy, clinical development of urelumab has been hampered by inflammatory liver toxicity at doses >1 mg/kg. Utomilumab has a superior safety profile, but is a less potent 4-1BB agonist relative to urelumab. Both antibodies have demonstrated promising results in patients with lymphoma and are being tested in combination therapy trials with other immunomodulatory agents. In an effort to optimally leverage 4-1BB-mediated immune activation, the next generation of 4-1BB targeting strategies attempts to decouple the observed antitumor efficacy from the on-target liver toxicity. Multiple therapeutics that attempt to restrict 4-1BB agonism to the tumor microenvironment and minimize systemic exposure have emerged. 4-1BB is a compelling target for cancer immunotherapy and future agents show great promise for achieving potent immune activation while avoiding limiting immune-related adverse events.

Immunotherapy-based combinations: current status and perspectives

PURPOSE OF REVIEW

Since the approval of ipilimumab, different immune checkpoint inhibitors, vaccines and costimulatory agonists have been developed with success, improving patient's survival in a number of different tumour types. However, immunotherapy results in durable responses but only in a fraction of patients. In order to improve this, combination of different immune agents is currently being attempted in the clinic with the potential of becoming one day the next wave of immune treatments available for our cancer patients.

RECENT FINDINGS

Combinatory regimens may have synergistic effects by acting at different points of the cancer immune cycle, from initiation and propagation of anticancer immunity, to stimulation of neoantigen presentation and priming, promotion of trafficking of immune cells to access the tumour and, finally, cancer-cell recognition and killing.

SUMMARY

In this article, the most relevant combination strategies that are currently under research are reviewed, as they are expected to become a new standard of care in the near future.

Roles for Innate Immunity in Combination Immunotherapies

Immunity to infectious agents involves a coordinated response of innate and adaptive immune cells working in concert, with many feed-forward and regulatory interactions between both arms of the immune system. In contrast, many therapeutic strategies to augment immunity against tumors have focused predominantly on stimulation of adaptive immunity. However, a growing appreciation of the potential contributions of innate immune effectors to antitumor immunity, especially in the context of combination immunotherapy, is leading to novel strategies to elicit a more integrated immune response against cancer. Here we review antitumor activities of innate immune cells, mechanisms of their synergy with adaptive immune responses against tumors, and discuss recent studies highlighting the potential of combination therapies recruiting both innate and adaptive immune effectors to eradicate established tumors. Cancer Res; 77(19); 5215-21. ©2017 AACR.

Anti-CD137 Suppresses Tumor Growth by Blocking Reverse Signaling by CD137 Ligand

CD137 (4-1BB) is a T-cell costimulatory molecule, and agonstic CD137 antibodies are currently being evaluated in the clinic as cancer immunotherapy. Recently, it was found that CD137^-/- mice or mice injected with agonistic anti-CD137 antibodies exhibit heightened antitumor responses, contrary to expectations based on other knowledge of CD137 function. Here, we report findings related to reverse signaling by CD137 ligand (CD137L) in antigen-presenting dendritic cells (DC) in tumors that address these paradoxical results. Specifically, CD137L suppressed intratumoral differentiation of IL12-producing CD103⁺ DC and type 1 tumor-associated macrophages (TAM). Differentiation of these cell types is important because they are required to generate IFNγ-producing CD8⁺ cytotoxic T lymphocytes (Tc1). Notably, CD137L blockade increased levels of IL12 and IFNγ, which promoted intratumoral differentiation of IFNγ-producing Tc1, IL12-producing CD103⁺ DC, and type 1 TAM within tumors. Our results offer an explanation for the paradoxical effects of CD137 blockade, based on differential immunomodulatory effects of CD137 signaling and reverse signaling in T cells and DC, respectively. Further, they show how CD137L blockade can seed a forward-feedback loop for activation of CD103⁺ DC/type 1 TAM and Tc1 that can create a self-perpetuating cycle of highly effective immunosurveillance. Cancer Res; 77(21); 5989-6000. ©2017 AACR.

New Combination Strategies Using Programmed Cell Death 1/Programmed Cell Death Ligand 1 Checkpoint Inhibitors as a Backbone

The discovery of immune checkpoints and subsequent clinical development of checkpoint inhibitors have revolutionized the field of oncology. The durability of the antitumor immune responses has raised the hope for long-term patient survival and potential cure; however, currently, only a minority of patients respond. Combination strategies to help increase antigen release and T-cell priming, promote T-cell activation and homing, and improve the tumor immune microenvironment, all guided by predictive biomarkers, can help overcome the tumor immune-evasive mechanisms and maximize efficacy to ultimately benefit the majority of patients. Great challenges remain because of the complex underlying biology, unpredictable toxicity, and accurate assessment of response. Carefully designed clinical trials guided by translational studies of paired biopsies will be key to develop reliable predictive biomarkers to choose which patients would most likely benefit from each strategy.

Nimotuzumab Induces NK Cell Activation, Cytotoxicity, Dendritic Cell Maturation and Expansion of EGFR-Specific T Cells in Head and Neck Cancer Patients

Survival benefit and long-term duration of clinical response have been seen using the epidermal growth factor receptor (EGFR)-targeted monoclonal antibody (mAb) nimotuzumab. Blocking EGFR signaling may not be the only mechanism of action underlying its efficacy. As an IgG1 isotype mAb, nimotuzumab's capacity of killing tumor cells by antibody dependent cellular cytotoxicity (ADCC) and to induce an immune response in cancer patients have not been studied. ADCC-induced by nimotuzumab was determined using a ⁵¹Cr release assay. The in vitro effect of nimotuzumab on natural killer (NK) cell activation and dendritic cell (DC) maturation and the in vivo frequency of circulating regulatory T cells (Tregs) and NK cells were assessed by flow cytometry. Cytokine levels in supernatants were determined by ELISA. ELISpot was carried out to quantify EGFR-specific T cells in nimotuzumab-treated head and neck cancer (HNSCC) patients. Nimotuzumab was able to kill EGFR+ tumor cells by NK cell-mediated ADCC. Nimotuzumab-activated NK cells promoted DC maturation and EGFR-specific CD8+ T cell priming. Interestingly, nimotuzumab led to upregulation of some immune checkpoint molecules on NK cells (TIM-3) and DC (PD-L1), to a lower extent than another EGFR mAb, cetuximab. Furthermore, circulating EGFR-specific T cells were identified in nimotuzumab-treated HNSCC patients. Notably, nimotuzumab combined with cisplatin-based chemotherapy and radiation increased the frequency of peripheral CD4+CD39+FOXP3+Tregs which otherwise were decreased to baseline values when nimotuzumab was used as monotherapy. The frequency of circulating NK cells remained constant during treatment. Nimotuzumab-induced, NK cell-mediated DC priming led to induction of anti-EGFR specific T cells in HNSCC patients. The association between EGFR-specific T cells and patient clinical benefit with nimotuzumab treatment should be investigated.

Blockade of CD112R and TIGIT signaling sensitizes human natural killer cell functions

Trastuzumab is the first-line drug to treat breast cancer with high Her2 expression. However, many cancers failed to respond, largely due to their resistance to NK cell-triggered antibody-dependent cellular cytotoxicity (ADCC). Poliovirus receptor (PVR)-like molecules are known to be important for lymphocyte functions. We found that all PVR-like receptors are expressed on human NK cells, and only TIGIT is preferentially expressed on the CD16+ NK cell subset. Disrupting the interactions of PVR-like receptors with their ligands on cancer cells regulates NK cell activity. More importantly, TIGIT is upregulated upon NK cell activation via ADCC. Blockade of TIGIT or CD112R, separately or together, enhances trastuzumab-triggered antitumor response by human NK cells. Thus, our findings suggest that PVR-like receptors regulate NK cell functions and can be targeted for improving trastuzumab therapy for breast cancer.

Immunotherapeutic properties of chemotherapy

Impressive remissions driven by immunological checkpoint blockade in cancer patients have prompted the scientific community to investigate afresh the crosstalk between cancer cells and the patient's immune system. Preclinical and clinical studies have highlighted that the anticancer efficacy of some conventional chemotherapeutics is based on their ability to restore anticancer immune responses. The current challenge is to understand and circumvent immune resistance mechanisms to chemo- and immunotherapies to design relevant immunotherapy and chemotherapy combinations. In this review, we will summarize which immunological processes are involved in the anticancer action of some cytotoxic agents and discuss the recently unraveled contribution of the gut microbiota into the immunogenicity of anticancer drugs. We will eventually introduce the scientific rationale for therapeutic strategies combining chemotherapeutic drugs and immune checkpoint blockers.

Immunotherapy of head and neck cancer: Emerging clinical trials from a National Cancer Institute Head and Neck Cancer Steering Committee Planning Meeting

Recent advances have permitted successful therapeutic targeting of the immune system in head and neck squamous cell carcinoma (HNSCC). These new immunotherapeutic targets and agents are being rapidly adopted by the oncologic community and hold considerable promise. The National Cancer Institute sponsored a Clinical Trials Planning Meeting to address the issue of how to further investigate the use of immunotherapy in patients with HNSCC. The goals of the meeting were to consider phase 2 or 3 trial designs primarily in 3 different patient populations: those with previously untreated, human papillomavirus-initiated oropharyngeal cancers; those with previously untreated, human papillomavirus-negative HNSCC; and those with recurrent/metastatic HNSCC. In addition, a separate committee was formed to develop integrative biomarkers for the clinical trials. The meeting started with an overview of key immune components and principles related to HNSCC, including immunosurveillance and immune escape. Four clinical trial concepts were developed at the meeting integrating different immunotherapies with existing standards of care. These designs were presented for implementation by the head and neck committees of the National Cancer Institute-funded National Clinical Trials Network. This article summarizes the proceedings of this Clinical Trials Planning Meeting, the purpose of which was to facilitate the rigorous development and design of randomized phase 2 and 3 immunotherapeutic trials in patients with HNSCC. Although reviews usually are published immediately after the meeting is held, this report is unique because there are now tangible clinical trial designs that have been funded and put into practice and the studies are being activated to accrual. Cancer 2017;123:1259-1271. © 2016 American Cancer Society.

Results of a Phase Ib Trial of Combination Immunotherapy with a CD8+ T Cell Eliciting Vaccine and Trastuzumab in Breast Cancer Patients

BACKGROUND

CD8+ T cell-eliciting vaccines are being investigated in breast cancer patients. Preclinical data showed that trastuzumab increases the susceptibility of tumor cells to lysis by vaccine-generated CD8+ T cells, suggesting potential benefit of a combination immunotherapy strategy. The current trial was undertaken to demonstrate the safety of this approach.

METHODS

This study was designed as a dose-escalation trial enrolling clinically disease-free, human leukocyte antigen A2+ or A3+ , human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients. Patients received 6-monthly inoculations of GP2+ granulocyte-macrophage colony-stimulating factor (GM-CSF) administered concurrently with standard-of-care trastuzumab. Local and systemic toxicity, as well as left ventricular ejection fraction (LVEF) were monitored. Immunologic responses were assessed in vivo by measuring the local reaction and in vitro using an interferon-γ enzyme-linked immunosorbent spot (ELISPOT) assay.

RESULTS

Seventeen disease-free breast cancer patients were vaccinated. There were no dose-limiting or grade 3-5 local or systemic toxicities, and the median LVEF was unchanged from baseline after vaccination. Mean local reaction at initial inoculation was 28 ± 10 mm, increasing to 68 ± 8 mm at the final inoculation (p < 0.01). Mean ELISPOT response to GP2 increased from 47 ± 19 at baseline to 144 ± 60 (p = 0.13) after vaccination. Based on safety and immunologic data, the appropriate dose was determined to be 1000 μg of GP2 + 250 μg of GM-CSF.

CONCLUSION

The GP2 + GM-CSF vaccine is safe and stimulates an immunologic response when administered concurrently with trastuzumab. An ongoing phase II trial is evaluating the efficacy of combining a CD8 T-cell-eliciting vaccine with trastuzumab in HER2-positive breast cancer patients.

Targeting NK-cell checkpoints for cancer immunotherapy

Natural Killer (NK) cells are cytotoxic lymphocytes specialized in early defense against virus-infected and transformed cells. NK-cell function is regulated by activating and inhibitory surface receptors recognizing their ligands on transformed cells. Modulation of NK numbers and/or function by a variety of agents such as cytokines and monoclonal antibodies may result in enhanced anti-tumor activity. Recombinant cytokines (i.e., IL-15 and IL-2), antibodies blocking inhibitory receptors (i.e., KIR, NKG2A and TIGIT) and agonists delivering signals via CD137, NKG2D and CD16 stand out as the most suitable opportunities. These agents can be used to potentiate NKcell- mediated antibody-dependent cellular cytotoxicity (ADCC) against antibody-coated tumor cells, offering potential for multiple combinatorial immunotherapy strategies against cancer.

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.

New Immunotherapy Strategies in Breast Cancer

Breast cancer is the most commonly diagnosed cancer among women. Therapeutic treatments for breast cancer generally include surgery, chemotherapy, radiotherapy, endocrinotherapy and molecular targeted therapy. With the development of molecular biology, immunology and pharmacogenomics, immunotherapy becomes a promising new field in breast cancer therapies. In this review, we discussed recent progress in breast cancer immunotherapy, including cancer vaccines, bispecific antibodies, and immune checkpoint inhibitors. Several additional immunotherapy modalities in early stages of development are also highlighted. It is believed that these new immunotherapeutic strategies will ultimately change the current status of breast cancer therapies.

Manipulating the Immune System With Checkpoint Inhibitors for Patients With Metastatic Sarcoma

Sarcomas are a rare group of malignant tumors of mesenchymal origin that comprise 1% of all adult cancers. Despite initial surgery, distant metastatic disease will develop in approximately 25% of patients, and standard chemotherapy has limited durable efficacy. There is a dire need for more effective and less toxic therapies for the treatment of metastatic sarcoma. The immune system plays a major role in cancer control and progression. There have been tremendous breakthroughs in other malignancies by manipulating the immune system with checkpoint inhibitors. These agents, either alone or in combination with other approaches such as radiation, chemotherapy, targeted agents, or immunotherapeutics, have generally led to improved efficacy in selected malignancies thus far. Although promising, these drugs can cause specific immune-related adverse events that require prompt recognition and treatment. In addition, characterizing response and progression radiographically has become somewhat more challenging. Identifying predictive biomarkers of benefit will be essential. There remains optimism and hope that the strides made in other cancers will be emulated in sarcoma.

Taxanes enhance trastuzumab-mediated ADCC on tumor cells through NKG2D-mediated NK cell recognition

Recent clinical data indicate a synergistic therapeutic effect between trastuzumab and taxanes in neoadjuvantly treated HER2-positive breast cancer (BC) patients. In HER2+ BC experimental models and patients, we investigated whether this synergy depends on the ability of drug-induced stress to improve NK cell effectiveness and thus trastuzumab-mediated ADCC. HER2+ BC cell lines BT474 and MDAMB361 treated with docetaxel showed up-modulation of NK activator ligands both in vitro and in vivo, accompanied by a 15-40% increase in in vitro trastuzumab-mediated ADCC; antibodies blocking the NKG2D receptor significantly reduced this enhancement. NKG2D receptor expression was increased by docetaxel treatment in circulating and splenic NK cells from mice xenografted with tumor cells, an increase related to expansion of the CD11b+Ly6G+ cell population. Accordingly, NK cells derived from HER2+ BC patients after treatment with taxane-containing therapy expressed higher levels of NKG2D receptor than before treatment. Moreover, plasma obtained from these patients recapitulated the modulation of NKG2D on healthy donors' NK cells, improving their trastuzumab-mediated activity in vitro. This enhancement occurred mainly using plasma from patients with low NKG2D basal expression. Our results indicate that taxanes increase tumor susceptibility to ADCC by acting on tumor and NK cells, and suggest that taxanes concomitantly administered with trastuzumab could maximize the antibody effect, especially in patients with low basal immune effector cytotoxic activity.

Clinical significance of tumor-infiltrating lymphocytes in breast cancer

Tumor infiltrating lymphocytes (TIL) play an essential role in mediating response to chemotherapy and improving clinical outcomes in all subtypes of breast cancer. Triple negative breast cancers (TN) are most likely to have tumors with >50 % lymphocytic infiltrate, termed lymphocyte predominant breast cancer, and derive the greatest survival benefit from each 10 % increase in TIL. The majority of HER2+ breast cancers have similar level of immune infiltrate as TN breast cancer yet the presence of TILs has not shown the same survival benefit. For HER2+ breast cancers, type 1 T-cells, either increased TBET+ tumor infiltration or increased type 1 HER2-specific CD4+ T-cells in the peripheral blood, are associated with better outcomes. Hormone receptor positive HER2 negative tumors tend to have the least immune infiltrate yet are the only breast cancer subtype to show worse prognosis with increased FOXP3 regulatory T-cell infiltrate. Notably, all breast cancer subtypes have tumors with low, intermediate, or high TIL infiltrate. Tumors with high TILs may also have increased PD-L1 expression which might be the reason that TN breast cancer seems to demonstrate the most robust clinical response to immune checkpoint inhibitor therapy but further investigation is needed. Tumors with intermediate or low levels of pre-treatment immune infiltrate, on the other hand, may benefit from an intervention that may increase TIL, particularly type 1 T-cells. Examples of these interventions include specific types of cytotoxic chemotherapy, radiation, or vaccine therapy. Therefore, the systematic evaluation of TIL and specific populations of TIL may be able to both guide prognosis and the appropriate sequencing of therapies in breast cancer.

4-1BB agonism: adding the accelerator to cancer immunotherapy

The success of checkpoint inhibitors has validated immunomodulatory agents as a valuable class of anticancer therapeutics. A promising co-stimulatory immunologic target is 4-1BB, or CD137, a member of the tumor necrosis factor receptor superfamily. Ligation of 4-1BB induces an activating signal in CD8(+) T cells and natural killer cells, resulting in increased pro-inflammatory cytokine secretion, cytolytic function, and antibody-dependent cell-mediated cytotoxicity. Targeting 4-1BB with agonistic monoclonal antibody (mAb) therapy demonstrated potent antitumor effects in murine tumor models. While anti-4-1BB mAbs have entered clinical trials, optimal efficacy of 4-1BB-targeted agents will inevitably come from combination therapeutic strategies. Checkpoint blockade is a compelling combination partner for 4-1BB agonism. This novel immunotherapeutic approach has the potential to active antitumor immune effectors by a complementary mechanism: simultaneously "removing the brakes" via blocking inhibitory signaling and "stepping on the accelerator" via co-stimulation. While important considerations should be given to 4-1BB-mediated toxicities, the current understanding of 4-1BB biology suggests it may play a key role in advancing the capabilities of cancer combination therapy.

Novel anti-EPHA2 antibody, DS-8895a for cancer treatment

Overexpression of EPHA2 has been observed in multiple cancers and reported to be associated with poor prognosis. Here, we produced an afucosylated humanized anti-EPHA2 monoclonal antibody (mAb), DS-8895a for cancer treatment. The antibody recognizes the extracellular juxtamembrane region of EPHA2 and therefore can bind to both full-length and truncated forms of EPHA2, which are anchored to cell membranes and recently reported to be produced by post-translational cleavage in tumors. DS-8895a exhibited markedly increased antibody dependent cellular cytotoxicity (ADCC) in vitro and also inhibited tumor growth in EPHA2-positive human breast cancer MDA-MB-231 and human gastric cancer SNU-16 xenograft mouse models. Moreover, DS-8895a in combination with cisplatin (CDDP) showed better efficacy than each of the monotherapies did in the human gastric cancer model. These results suggest that a novel antibody, DS-8895a has therapeutic potential against EPHA2-expressing tumors.

Rituximab induces phenotypical and functional changes of NK cells in a non-malignant experimental setting

Background

Rituximab has broad and increasing application in rheumatic diseases. It is known from lymphoma studies that natural killer (NK) cells can lyse rituximab-coated transformed B cells. However, the role of NK cells in mediating rituximab-induced depletion of non-malignant B cells is unknown. The purpose of this study was to provide fundamental data on rituximab-mediated effects on NK cells in PBMCs without tumor cells, in order to simulate effects that could be relevant in patients with rheumatic disease.

Methods

Freshly isolated peripheral blood mononuclear cells (PBMCs) from healthy donors were cultured overnight with therapeutic antibodies. NK cells were isolated using a commercial kit or depleted from PBMCs using anti-CD56 and anti-CD16 monoclonal antibodies and magnetic beads. Cells were analyzed by multicolor flow cytometry. Cytotoxicity assays were performed using ⁵¹Cr-labeled K562 target cells.

Results

Addition of rituximab to PBMCs resulted in depletion of B cells, which was dependent on NK cells and serum factors. The extent of B cell depletion correlated with the percentage of NK cells. Following incubation with rituximab, NK cells within PBMCs were activated, degranulated and downregulated the low affinitiy Fc-γ-receptor CD16 (FcγRIIIA). The co-activating receptor CD137 (41BB) was upregulated on a fraction of NK cells. NK cell function was altered in some donors in whom we observed rituximab-dependent reduction in NK cell cytotoxicity towards K562 tumor cells.

Conclusions

NK cells mediate rituximab-induced B cell depletion. Rituximab induces altered NK cell phenotype and function.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1101-3) contains supplementary material, which is available to authorized users.

Anti-CD137 enhances anti-CD20 therapy of systemic B-cell lymphoma with altered immune homeostasis but negligible toxicity

Studies of sequential anti-CD137/anti-CD20 therapy have previously shown that the efficacy of anti-CD20 was heavily reliant upon anti-CD137; however, the exact mechanism of the anti-B-cell lymphoma efficacy, and whether this correlates with enhanced adverse effects or toxicity, had not been elucidated. Here, we observed that sequential anti-CD137 administration with anti-CD20 resulted in a synergistic therapy, largely dependent upon Fc receptors (FcR), to prolong survival in an experimental B-cell lymphoma therapy model. Tumor suppression was accompanied by B cell depletion, which was not dependent on one activating FcR. Surprisingly, the B-cell activating factor (BAFF) was elevated in the plasma of mice receiving anti-CD137 alone or in combination with anti-CD20, while a selective increase in some plasma cytokines was also noted and triggered by anti-CD137. These effects were independent of activating FcR. Sustained treatment of advanced lymphoma revealed increased lymphocyte infiltrates into the liver and a significant decrease in the metabolic capability of the liver in mice receiving anti-CD137. Importantly, these effects were not exacerbated in mice receiving the anti-CD20/CD137 combination, and elevations in classical liver damage markers such as alanine aminotransferase (ALT) were less than that caused by the lymphoma itself. Thus, combined anti-CD20/anti-CD137 treatment increases the therapeutic index of anti-CD20 or anti-CD137 alone. These mouse data were corroborated by ongoing clinical development studies to assess safety, tolerability and pharmacodynamic activity of human patients treated by this approach. Together, these data support the use of this sequential antibody therapeutic strategy to improve the efficacy of rituximab in B-cell lymphoma patients.

Designing multivalent proteins based on natural killer cell receptors and their ligands as immunotherapy for cancer

INTRODUCTION

Natural killer (NK) cells are an important component of the innate immune system that play a key role in host immunity against cancer. NK cell recognition and activation is based on cell surface receptors recognizing specific ligands that are expressed on many types of tumor cells. Some of these receptors are capable of activating NK cell function while other receptors inhibit NK cell function. Therapeutic approaches to treat cancer have been developed based on preventing NK cell inhibition or using NK cell receptors and their ligands to activate NK cells or T cells to destroy tumor cells.

AREAS COVERED

This article describes the various strategies for targeting NK cell receptors and NK cell receptor ligands using multivalent proteins to activate immunity against cancer.

EXPERT OPINION

NK cell receptors work in synergy to activate NK cell effector responses. Effective anti-cancer strategies will need to not only kill tumor cells but must also lead to the destruction of the tumor microenvironment. Immunotherapy based on NK cells and their receptors has the capacity to accomplish this through triggering lymphocyte cytotoxicity and cytokine production.

Immunomodulatory antibodies for the treatment of lymphoma: Report on the CALYM Workshop

In November 2015, the CALYM Carnot Institute held a 2-d workshop to discuss the current and future development of immunomodulatory antibodies for the treatment of lymphoma. Highlights from the workshop are presented in this article.

Emerging therapeutic targets in metastatic progression: A focus on breast cancer

Metastasis is the underlying cause of death for the majority of breast cancer patients. Despite significant advances in recent years in basic research and clinical development, therapies that specifically target metastatic breast cancer remain inadequate, and represents the single greatest obstacle to reducing mortality of late-stage breast cancer. Recent efforts have leveraged genomic analysis of breast cancer and molecular dissection of tumor-stromal cross-talk to uncover a number of promising candidates for targeted treatment of metastatic breast cancer. Rational combinations of therapeutic agents targeting tumor-intrinsic properties and microenvironmental components provide a promising strategy to develop precision treatments with higher specificity and less toxicity. In this review, we discuss the emerging therapeutic targets in breast cancer metastasis, from tumor-intrinsic pathways to those that involve the host tissue components, including the immune system.

Deciphering CD137 (4-1BB) signaling in T-cell costimulation for translation into successful cancer immunotherapy

CD137 (4-1BB, TNF-receptor superfamily 9) is a surface glycoprotein of the TNFR family which can be induced on a variety of leukocyte subsets. On T and NK cells, CD137 is expressed following activation and, if ligated by its natural ligand (CD137L), conveys polyubiquitination-mediated signals via TNF receptor associated factor 2 that inhibit apoptosis, while enhancing proliferation and effector functions. CD137 thus behaves as a bona fide inducible costimulatory molecule. These functional properties of CD137 can be exploited in cancer immunotherapy by systemic administration of agonist monoclonal antibodies, which increase anticancer CTLs and enhance NK-cell-mediated antibody-dependent cell-mediated cytotoxicity. Reportedly, anti-CD137 mAb and adoptive T-cell therapy strongly synergize, since (i) CD137 expression can be used to select the T cells endowed with the best activities against the tumor, (ii) costimulation of the lymphocyte cultures to be used in adoptive T-cell therapy can be done with CD137 agonist antibodies or CD137L, and (iii) synergistic effects upon coadministration of T cells and antibodies are readily observed in mouse models. Furthermore, the signaling cytoplasmic tail of CD137 is a key component of anti-CD19 chimeric antigen receptors that are used to redirect T cells against leukemia and lymphoma in the clinic. Ongoing phase II clinical trials with agonist antibodies and the presence of CD137 sequence in these successful chimeric antigen receptors highlight the importance of CD137 in oncoimmunology.

Natural and therapy-induced immunosurveillance in breast cancer

The immunosurveillance theory postulates that tumors evolve and progress in an uncontrolled fashion only when anticancer immune responses fail. Natural immunosurveillance clearly influences human breast cancer (BC) progression because the prognosis of BC patients is dictated by the density, composition and activity of the tumor immune infiltrate at diagnosis. Moreover, chemotherapeutic and radiotherapeutic regimens commonly employed for the treatment of BC affect the tumor immune infiltrate, and accumulating data suggest that the clinical efficacy of these treatments is largely determined by T cell-dependent tumor-specific immune responses. In addition, the mechanism of action of targeted anticancer therapeutics, such as the erb-b2 receptor tyrosine kinase 2 (ERBB2)-targeting agent trastuzumab, involves the innate and adaptive arms of the immune system. In this Review, we discuss these findings as well as preliminary evidence indicating that immunotherapy constitutes a promising option for the treatment of BC. Moreover, we point out that the successful implementation of immunotherapy to BC management requires the optimization of current immunotherapeutic regimens and the identification of immunological biomarkers that enable improved risk stratification and the design of personalized, dynamic treatment plans.

Mouse Models of Tumor Immunotherapy

Immunotherapy is now evolving into a major therapeutic option for cancer patients. Such clinical advances also promote massive interest in the search for novel immunotherapy targets, and to understand the mechanism of action of current drugs. It is projected that a series of novel immunotherapy agents will be developed and assessed for their therapeutic activity. In light of this, in vivo experimental mouse models that recapitulate human malignancies serve as valuable tools to validate the efficacy and safety profile of immunotherapy agents, before their transition into clinical trials. In this review, we will discuss the major classes of experimental mouse models of cancer commonly used for immunotherapy assessment and provide examples to guide the selection of appropriate models. We present some new data concerning the utility of a carcinogen-induced tumor model for comparing immunotherapies and combining immunotherapy with chemotherapy. We will also highlight some recent advances in experimental modeling of human malignancies in mice that are leading towards personalized therapy in patients.

Identification of CD245 as myosin 18A, a receptor for surfactant A: A novel pathway for activating human NK lymphocytes

CD245 is a human surface antigen expressed on peripheral blood lymphocytes, initially delineated by two monoclonal antibodies DY12 and DY35. Until now, CD245 molecular and functional characteristics remained largely unknown. We combined immunological and proteomic approaches and identified CD245 as the unconventional myosin 18A, a highly conserved motor enzyme reported as a receptor for the surfactant protein A (SP-A), that plays a critical role in cytoskeleton organization and Golgi budding. We report that the recruitment of CD245 strongly enhanced NK cell cytotoxicity. Further, we show that the enhancement of the NK lymphocytes killing ability toward CD137-ligand expressing target cells could result from the induction of CD137 expression following CD245 engagement. The SP-A receptor could therefore represent a novel and promising target in cancer immunotherapy.

The Role of Adaptive Immunity in the Efficacy of Targeted Cancer Therapies

Accumulating evidence indicates that the efficacy of tumor-targeted therapies relies on the host immune response, including targeted small-molecule and antibody approaches that were not previously thought to have an immune component. Here, we review the current understanding of how targeted therapies on tumor cells could have a major impact on the immune response, and how this relates to the therapeutic efficacy of these approaches. In this context, we evaluate different strategies that combine targeted therapies with immunotherapy approaches, and discuss past and ongoing clinical trials. We highlight gaps in knowledge, and argue that significant progress for combined therapies will require a better understanding of the complex interactions between immune cells, the tumor, and the tumor microenvironment (TME) in different cancer settings.

Rationale for anti-CD137 cancer immunotherapy

The consideration of the complex interplay between the tumour microenvironment (TME) and the immune response is the key for designing effective immunotherapies. Therapeutic strategies that harness co-stimulatory receptors have recently gained momentum in the clinic. One such strategy with promising clinical applications is the targeting of CD137, a member of the tumour necrosis factor receptor superfamily. Its expression on both innate and adaptive immune cells, coupled with its unique ability to potentiate antitumour responses through modulating the TME and to ameliorate autoimmune responses, has established it as an appealing target. In this review, we will discuss the various CD137-targeted immunotherapeutics that have reached clinical development, with a focus on recent advances and novel modalities such as CD137 chimeric antigen receptors and CD137 bispecific antibodies. We will also highlight the effect of CD137 targeting on the TME and discuss the importance of probing TME changes for predicting and testing the efficacy of CD137-mediated immunotherapy.

NK cells and cancer: you can teach innate cells new tricks

Natural killer (NK) cells are the prototype innate lymphoid cells endowed with potent cytolytic function that provide host defence against microbial infection and tumours. Here, we review evidence for the role of NK cells in immune surveillance against cancer and highlight new therapeutic approaches for targeting NK cells in the treatment of cancer.

Tumour necrosis factor receptor superfamily member 9 (TNFRSF9) is up-regulated in reactive astrocytes in human gliomas

AIMS

The prognosis of patients with malignant gliomas is still dismal despite maximum treatment. Novel therapeutic alternatives targeting tumorigenic pathways are, therefore, demanded. In murine glioma models, targeting of tumour necrosis factor receptor superfamily (TNFRSF) 9 led to complete tumour eradication. Thus, TNFRSF9 might also constitute a promising target in human diffuse gliomas. As there is a lack of data, we aimed to define the expression pattern and cellular source of TNFRSF9 in human gliomas.

METHODS

We investigated TNFRSF9 expression in normal human central nervous system (CNS) tissue and glioma specimens using immunohistochemistry, immunofluorescence and Western blotting techniques.

RESULTS

Our results show that TNFRSF9 is considerably up-regulated in human gliomas when compared with normal brain tissue. In addition, our data provides evidence for an immune cell-independent de novo expression pattern of TNFRSF9 in mainly non-neoplastic reactive astrocytes and excludes classic immunological cell types, namely lymphocytes and microglia as the source of TNFRSF9. Moreover, TNFRSF9 is predominantly expressed in a perivascular and peritumoural distribution with significantly higher expression in IDH-1 mutant gliomas.

CONCLUSIONS

Our findings provide a novel, TNFRSF9-positive, reactive astrocytic phenotype and challenge the therapeutic suitability of TNFRSF9 as a promising target for human gliomas.

Combination cancer immunotherapies tailored to the tumour microenvironment

Evidence suggests that cancer immunotherapy will be a major part of the combination treatment plan for many patients with many cancer types in the near future. There are many types of immune processes involving different antitumour and tumour-promoting leucocytes, and tumour cells use many strategies to evade the immune response. The tumour microenvironment can help determine which immune suppressive pathways become activated to restrain antitumour immunity. This includes immune checkpoint receptors on effector T-cells and myeloid cells, and release of inhibitory cytokines and metabolites. Therapeutic approaches that target these pathways, particularly immune-checkpoint receptors, can induce durable antitumour responses in patients with advanced-stage cancers, including melanoma. Nevertheless, many patients do not have a good response to monotherapy approaches and alternative strategies are required to achieve optimal therapeutic benefit. These strategies include eliminating the bulk of tumour cells to provoke tumour-antigen release and antigen-presenting cell (APC) function, using adjuvants to enhance APC function, and using agents that enhance effector-cell activity. In this Review, we discuss the stratification of the tumour microenvironment according to tumour-infiltrating lymphocytes and PD-L1 expression in the tumour, and how this stratification enables the design of optimal combination cancer therapies tailored to target different tumour microenvironments.

Signaling pathway and dysregulation of PD1 and its ligands in lymphoid malignancies

Tumor cells evade immune destruction, at least partially, by upregulating inhibitory signals to limit effector T cell activation. Programmed death 1 (PD-1) is one of the most critical co-inhibitory molecules limiting the T-cell antitumor response. PD-1 and its ligands, PD-L1 and PD-L2, are overexpressed by various types of tumors as well as reactive cells in the tumor microenvironment. A growing body of evidence has shown the clinical efficiency and minimal toxicity of PD-1 pathway inhibitors in patients with solid tumors, but the role of these inhibitors in lymphoid malignancies is much less well studied. In this review, we analyze the pathologic role of the PD-1 pathway in most common lymphoid malignancies and we organize the clinical data from clinical trials of PD-1 pathway inhibitors. Several anti-PD-1 regimens have shown encouraging therapeutic effects in patients with relapsed or refractory Hodgkin lymphoma, follicular lymphoma, and diffuse large B-cell lymphoma. Additional progress is needed to foster an improved understanding of the role of anti-PD-1 therapy in reconstituting antitumor immunity in patients with lymphoid malignancies. Upcoming trials will explore the clinical efficiency of combining PD-1 pathway inhibitors and various agents with diverse mechanisms of action and create more therapeutic possibilities for afflicted patients.