Cancer immunotherapy: co-stimulatory agonists and co-inhibitory antagonists

Ablation of B7-H3 but Not B7-H4 Results in Highly Increased Tumor Burden in a Murine Model of Spontaneous Prostate Cancer

The costimulatory molecules B7-H3 and B7-H4 are overexpressed in a variety of human tumors and have been hypothesized as possible biomarkers and immunotherapeutic targets. Despite this potential, the predominating uncertainty about their functional implication in tumor-host interaction hampers their evaluation as a target for cancer therapy. By means of a highly physiologic, spontaneous tumor model in mice, we establish a causal link between B7-H3 and host tumor control and found B7-H4 to be redundant.

Expression of inhibitory receptors on intratumoral T cells modulates the activity of a T cell-bispecific antibody targeting folate receptor

T-cell bispecific antibodies (TCBs) are a novel therapeutic tool designed to selectively recruit T-cells to tumor cells and simultaneously activate them. However, it is currently unknown whether the dysfunctional state of T-cells, embedded into the tumor microenvironment, imprints on the therapeutic activity of TCBs. We performed a comprehensive analysis of activation and effector functions of tumor-infiltrating T-cells (TILs) in different tumor types, upon stimulation by a TCB targeting folate receptor 1 and CD3 (FolR1-TCB). We observed a considerable heterogeneity in T-cell activation, cytokine production and tumor cell killing upon exposure to FolR1-TCB among different FolR1-expressing tumors. Of note, tumors presenting with a high frequency of PD-1^hi TILs displayed significantly impaired tumor cell killing and T-cell function. Further characterization of additional T-cell inhibitory receptors revealed that PD-1^hi TILs defined a T-cell subset with particularly high levels of multiple inhibitory receptors compared with PD-1^int and PD-1^neg T-cells. PD-1 blockade could restore cytokine secretion but not cytotoxicity of TILs in a subset of patients with scarce PD-1^hi expressing cells; in contrast, patients with abundance of PD-1^hi expressing T-cells did not benefit from PD-1 blockade. Our data highlight that FolR1-TCB is a promising novel immunotherapeutic treatment option which is capable of activating intratumoral T-cells in different carcinomas. However, its therapeutic efficacy may be substantially hampered by a pre-existing dysfunctional state of T-cells, reflected by abundance of intratumoral PD-1^hi T-cells. These findings present a rationale for combinatorial approaches of TCBs with other therapeutic strategies targeting T-cell dysfunction.

Polymeric microparticles for sustained and local delivery of antiCD40 and antiCTLA-4 in immunotherapy of cancer

This study investigated the feasibility of the use of polymeric microparticles for sustained and local delivery of immunomodulatory antibodies in immunotherapy of cancer. Local delivery of potent immunomodulatory antibodies avoids unwanted systemic side effects while retaining their anti-tumor effects. Microparticles based on poly(lactic-co-hydroxymethyl-glycolic acid) (pLHMGA) and loaded with two distinct types of immunomodulatory antibodies (CTLA-4 antibody blocking inhibitory receptors on T cells or CD40 agonistic antibody stimulating dendritic cells) were prepared by double emulsion solvent evaporation technique. The obtained particles had a diameter of 12-15 μm to avoid engulfment by phagocytes and were slightly porous as shown by SEM analysis. The loading efficiency of the antibodies in the microparticles was >85%. The in vitro release profile of antiCD40 and antiCTLA-4 from microparticles showed a burst release of about 20% followed by a sustained release of the content up to 80% of the loading in around 30 days. The therapeutic efficacy of the microparticulate formulations was studied in colon carcinoma tumor model (MC-38). Mice bearing subcutaneous MC-38 tumors were treated with the same dose of immunomodulatory antibodies formulated either in incomplete Freund's adjuvant (IFA) or in microparticles. The antibody-loaded microparticles showed comparable therapeutic efficacy to the IFA formulation with no local adverse effects. The biodegradable microparticles were fully resorbed in vivo and no remnants of inflammatory depots as observed with IFA were present in the cured mice. Moreover the microparticles exhibited lower antibody serum levels in comparison with IFA formulations which lowers the probability of systemic adverse effects. In conclusion, pLHMGA microparticles are excellent delivery systems in providing long-lasting and non-toxic antibody therapy for immunotherapy of cancer.

Immune checkpoint blockade in hematologic malignancies

Therapeutic blockade of immune checkpoint pathways, in particular cytotoxic T-lymphocyte associated protein 4 and programmed-death 1 (PD-1), has become a paradigm-shifting treatment in solid tumor oncology. Hematologic malignancies (HMs), many of which are known to have clinically exploitable immune sensitivity, are a natural target for this type of treatment. Several clinical trials of checkpoint blockade have been conducted in HM, with preliminary results suggesting the therapeutic usefulness of this approach across several tumor types. In particular, the results of PD-1 blockade in Hodgkin lymphoma (HL) are remarkable, and raise hope that it may alter the treatment landscape in this disease. However, numerous questions remain about the optimal role of checkpoint blockade both in HL and beyond. Those questions are the focus of this review, in the hope that, if we are at the dawn of a new day in HM immunotherapy, we may begin to envision its morning.

Phase II DeCOG-study of ipilimumab in pretreated and treatment-naïve patients with metastatic uveal melanoma

Purpose

Up to 50% of patients with uveal melanoma (UM) develop metastatic disease with limited treatment options. The immunomodulating agent ipilimumab has shown an overall survival (OS) benefit in patients with cutaneous metastatic melanoma in two phase III trials. As patients with UM were excluded in these studies, the Dermatologic Cooperative Oncology Group (DeCOG) conducted a phase II to assess the efficacy and safety of ipilimumab in patients with metastatic UM.

Patients and Methods

We undertook a multicenter phase II study in patients with different subtypes of metastatic melanoma. Here we present data on patients with metastatic UM (pretreated and treatment-naïve) who received up to four cycles of ipilimumab administered at a dose of 3 mg/kg in 3 week intervals. Tumor assessments were conducted at baseline, weeks 12, 24, 36 and 48 according to RECIST 1.1 criteria. Adverse events (AEs), including immune-related AEs were graded according to National Cancer Institute Common Toxicity Criteria (CTC) v.4.0. Primary endpoint was the OS rate at 12 months.

Results

Forty five pretreated (85%) and eight treatment-naïve (15%) patients received at least one dose of ipilimumab. 1-year and 2-year OS rates were 22% and 7%, respectively. Median OS was 6.8 months (95% CI 3.7–8.1), median progression-free survival 2.8 months (95% CI 2.5–2.9). The disease control rate at weeks 12 and 24 was 47% and 21%, respectively. Sixteen patients had stable disease (47%), none experienced partial or complete response. Treatment-related AEs were observed in 35 patients (66%), including 19 grade 3–4 events (36%). One drug-related death due to pancytopenia was observed.

Conclusions

Ipilimumab has very limited clinical activity in patients with metastatic UM. Toxicity was manageable when treated as per protocol-specific guidelines.

Trial Registration

ClinicalTrials.gov NCT01355120

Association between co-inhibitory molecule gene tagging single nucleotide polymorphisms and the risk of colorectal cancer in Chinese

PURPOSE

T lymphocyte immune responses are controlled by both co-stimulatory and co-inhibitory signaling through T cell co-receptors. Cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed death 1 (PD-1) and B and T lymphocyte attenuator (BTLA) are all co-inhibitory molecules that negatively regulate the activation of T cells. In this study, we investigated the relationship between ten tagging SNPs in three co-inhibitory molecule genes and colorectal cancer (CRC).

METHODS

We conducted a hospital-based case-control study consisting of 601 cases with CRC and 627 CRC-free individuals from the Heilongjiang Province of China.

RESULTS

The rs7421861 CT genotype was significantly associated with the risk of colorectal cancer compared to the wild-type TT genotype (adjusted OR 1.314, 95% CI 1.012-1.706, P = 0.041). The rs2705535 TT genotype was associated with the risk of rectal cancer [OR 1.819 (1.093-3.027), P = 0.021]. There was statistical interaction between the PD-1/rs2227982 (CT + TT) genotypes and high seafood intake (>once/week), as well as the CTLA-4/rs231777 variant and high pungent food intake (>3 times/week). The AG + AA genotypes of CTLA-4/rs3087243 statistically and antagonistically interacted with soybeans, pork and alcohol intake and were associated with CRC risk. Analogously, BTLA/rs1844089 interacted with pork intake, PD-1/rs7421861 with beef and lamb consumption and PD-1/rs6710479 with barbecue consumption. Haplotype G-C-G-A-T-T-A was significantly associated with CRC risk (OR 1.221 P = 0.034).

CONCLUSIONS

These data indicate potential associations between BTLA and PD-1 polymorphisms and CRC susceptibility. Additionally, the three co-inhibitory molecule gene SNPs have environmental interactions associated with CRC risk.

PD-1/PD-L1 pathway in non-small-cell lung cancer and its relation with EGFR mutation

Immunotherapy has become a crucial modality for non-small-cell lung cancer treatment. Recently, two immune checkpoints, PD-1 and PD-L1, have emerged as important targets for immunotherapy. Their antitumor efficacy has been confirmed by in vitro and in vivo studies. But the correlation between PD-1/PD-L1 expression and EGFR expression was controversial and needs more evidences to support the combination of PD-1/PD-L1 inhibitors and tyrosine kinase inhibitors.

Combinations of immunotherapy and radiation in cancer therapy

The immune system has the ability to recognize and specifically reject tumors, and tumors only become clinically apparent once they have evaded immune destruction by creating an immunosuppressive tumor microenvironment. Radiotherapy (RT) can cause immunogenic tumor cell death resulting in cross-priming of tumor-specific T-cells, acting as an in situ tumor vaccine; however, RT alone rarely induces effective anti-tumor immunity resulting in systemic tumor rejection. Immunotherapy can complement RT to help overcome tumor-induced immune suppression, as demonstrated in pre-clinical tumor models. Here, we provide the rationale for combinations of different immunotherapies and RT, and review the pre-clinical and emerging clinical evidence for these combinations in the treatment of cancer.

CAR T cells for solid tumors: armed and ready to go?

Chimeric antigen receptor (CAR) T cells face a unique set of challenges in the context of solid tumors. To induce a favorable clinical outcome, CAR T cells have to surmount a series of increasingly arduous tasks. First, they have to be made specific for an antigen whose expression clearly demarcates tumor from normal tissue. Then, they must be able to home and penetrate the desmoplastic stroma that surrounds the tumor. Once within the tumor, they must expand, persist, and mediate cytotoxicity in a hostile milieu largely composed of immunosuppressive modulators. Whereas a seemingly herculean task, all of the aforementioned requirements can potentially be met effectively through both intrinsic and/or extrinsic modifications of CAR T cells. In this review, we delineate the barriers imposed by solid tumors on CARs and strategies that have and should be undertaken to improve therapeutic response.

Renal cell carcinoma

The treatment of renal cell carcinoma (RCC) has changed greatly over the past 15 years. Progress in the surgical management of the primary tumor and increased understanding of the molecular biology and genomics of the disease have led to the development of new therapeutic agents. The management of the primary tumor has changed owing to the realization that clean margins around the primary lesion are sufficient to prevent local recurrence, as well as the development of more sophisticated tools and techniques that increase the safety of partial nephrectomy. The management of advanced disease has altered even more dramatically as a result of new agents that target the tumor vasculature or that attenuate the activation of intracellular oncogenic pathways. This review summarizes data from prospective randomized phase III studies on the surgical management and systemic treatment of RCC, and provides an up to date summary of the histology, genomics, staging, and prognosis of RCC. It describes the management of the primary tumor and offers an overview of systemic agents that form the mainstay of treatment for advanced disease. The review concludes with an introduction to the exciting new class of immunomodulatory agents that are currently in clinical trials and may form the basis of a new therapeutic approach for patients with advanced RCC.

Immunity and Immunopathology in the Tuberculous Granuloma

Granulomas, organized aggregates of immune cells, are a defining feature of tuberculosis (TB). Granuloma formation is implicated in the pathogenesis of a variety of inflammatory disorders. However, the tuberculous granuloma has been assigned the role of a host protective structure which "walls-off" mycobacteria. Work conducted over the past decade has provided a more nuanced view of its role in pathogenesis. On the one hand, pathogenic mycobacteria accelerate and exploit granuloma formation for their expansion and dissemination by manipulating host immune responses to turn leukocyte recruitment and cell death pathways in their favor. On the other hand, granuloma macrophages can preserve granuloma integrity by exerting a microbicidal immune response, thus preventing an even more rampant expansion of infection in the extracellular milieu. Even this host-beneficial immune response required to maintain the bacteria intracellular must be tempered, as an overly vigorous immune response can also cause granuloma breakdown, thereby directly supporting bacterial growth extracellularly. This review will discuss how mycobacteria manipulate inflammatory responses to drive granuloma formation and will consider the roles of the granuloma in pathogenesis and protective immunity, drawing from clinical studies of TB in humans and from animal models--rodents, zebrafish, and nonhuman primates. A deeper understanding of TB pathogenesis and immunity in the granuloma could suggest therapeutic approaches to abrogate the host-detrimental aspects of granuloma formation to convert it into the host-beneficial structure that it has been thought to be for nearly a century.

Localized oncolytic virotherapy overcomes systemic tumor resistance to immune checkpoint blockade immunotherapy

Preexisting lymphocytic infiltration of tumors is associated with superior prognostic outcomes in a variety of cancers. Recent studies also suggest that lymphocytic responses may identify patients more likely to benefit from therapies targeting immune checkpoints, suggesting that therapeutic efficacy of immune checkpoint blockade can be enhanced through strategies that induce tumor inflammation. To achieve this effect, we explored the immunotherapeutic potential of oncolytic Newcastle disease virus (NDV). We find that localized intratumoral therapy of B16 melanoma with NDV induces inflammatory responses, leading to lymphocytic infiltrates and antitumor effect in distant (nonvirally injected) tumors without distant virus spread. The inflammatory effect coincided with distant tumor infiltration with tumor-specific CD4(+) and CD8(+) T cells, which was dependent on the identity of the virus-injected tumor. Combination therapy with localized NDV and systemic CTLA-4 blockade led to rejection of preestablished distant tumors and protection from tumor rechallenge in poorly immunogenic tumor models, irrespective of tumor cell line sensitivity to NDV-mediated lysis. Therapeutic effect was associated with marked distant tumor infiltration with activated CD8(+) and CD4(+) effector but not regulatory T cells, and was dependent on CD8(+) cells, natural killer cells, and type I interferon. Our findings demonstrate that localized therapy with oncolytic NDV induces inflammatory immune infiltrates in distant tumors, making them susceptible to systemic therapy with immunomodulatory antibodies, which provides a strong rationale for investigation of such combination therapies in the clinic.

Reducing CD73 expression by IL1β-Programmed Th17 cells improves immunotherapeutic control of tumors

T cells of the T helper (Th)17 subset offer promise in adoptive T-cell therapy for cancer. However, current protocols for ex vivo programming of Th17 cells, which include TGFβ exposure, increase the expression of CD39 and CD73, two cell surface ATP ectonucleotidases that reduce T-cell effector functions and promote immunosuppression. Here, we report that ATP-mediated suppression of IFNγ production by Th17 cells can be overcome by genetic ablation of CD73 or by using IL1β instead of TGFβ to program Th17 cells ex vivo. Th17 cells cultured in IL1β were also highly polyfunctional, expressing high levels of effector molecules and exhibiting superior short-term control of melanoma in mice, despite reduced stem cell-like properties. TGFβ addition at low doses that did not upregulate CD73 expression but induced stemness properties drastically improved the antitumor effects of IL1β-cultured Th17 cells. Effector properties of IL1β-dependent Th17 cells were likely related to their high glycolytic capacity, since ex vivo programming in pyruvate impaired glycolysis and antitumor effects. Overall, we show that including TGFβ in ex vivo cultures used to program Th17 cells blunts their immunotherapeutic potential and demonstrate how this potential can be more fully realized for adoptive T-cell therapy.

Design and development of therapies using chimeric antigen receptor-expressing T cells

Investigators developed chimeric antigen receptors (CARs) for expression on T cells more than 25 years ago. When the CAR is derived from an antibody, the resultant cell should combine the desirable targeting features of an antibody (e.g. lack of requirement for major histocompatibility complex recognition, ability to recognize non-protein antigens) with the persistence, trafficking, and effector functions of a T cell. This article describes how the past two decades have seen a crescendo of research which has now begun to translate these potential benefits into effective treatments for patients with cancer. We describe the basic design of CARs, describe how antigenic targets are selected, and the initial clinical experience with CAR-T cells. Our review then describes our own and other investigators' work aimed at improving the function of CARs and reviews the clinical studies in hematological and solid malignancies that are beginning to exploit these approaches. Finally, we show the value of adding additional engineering features to CAR-T cells, irrespective of their target, to render them better suited to function in the tumor environment, and discuss how the safety of these heavily modified cells may be maintained.

Protein kinase C-η controls CTLA-4-mediated regulatory T cell function

Regulatory T cells (T_reg cells), which maintain immune homeostasis and self-tolerance, form an immunological synapse (IS) with antigen-presenting cells (APCs). However, signaling events at the T_reg IS remain unknown. Here we show that protein kinase C-η (PKC-η) associated with CTLA-4 and was recruited to the T_reg IS. PKC-η-deficient T_reg cells displayed defective suppressive activity, including suppression of tumor immunity but not autoimmune colitis. Phosphoproteomic analysis revealed an association between CTLA-4-PKC-η and the GIT-PIX-PAK complex, an IS-localized focal adhesion complex. Defective activation of this complex in PKC-η-deficient T_reg cells was associated with reduced CD86 depletion from APCs by T_reg cells. These results reveal a novel CTLA-4-PKC-η signaling axis required for contact-dependent suppression, implicating this pathway as a potential cancer immunotherapy target.

Reversal of tumor immune inhibition using a chimeric cytokine receptor

The success of adoptively transferred tumor-directed T cells requires them to survive and expand in vivo. Most tumors, however, employ immune evasion mechanisms, including the production of inhibitory cytokines that limit in vivo T-cell persistence and effector function. To protect tumor-directed T cells from such negative influences, we generated a chimeric cytokine receptor in which the interleukin (IL) 4 receptor exodomain was fused to the IL7 receptor endodomain. We thereby inverted the effects of tumor-derived IL4 so that the proliferation and activation of tumor directed cytotoxic T cells was enhanced rather than inhibited in the tumor microenvironment, resulting in superior antitumor activity. These transgenic T cells were only activated in the tumor environment since triggering required exposure to both tumor antigen (signal 1) and tumor-derived IL4 (signal 2). This selectivity supports future clinical adaptation.

Eomesodermin is required for antitumor immunity mediated by 4-1BB-agonist immunotherapy

CD8⁺ T cells in progressing tumors frequently fail to mount an effective antitumor response often in association with the expression of inhibitory receptors, including programmed cell death-1 (PD-1) and lymphocyte-activation gene 3 (Lag3). Using a lymphoma tumor model, we demonstrate that tumor-infiltrating CD8⁺ T cells from growing tumors co-express inhibitory receptors and co-stimulatory receptors, including 4-1BB (TNFRSF9) as well as high levels of 2 transcription factors, Eomesodermin (Eomes) and T-bet (Tbx21), critical determinants of CD8⁺ T cell fate. Immunotherapy with an agonistic anti-4–1-BB antibody altered the ratio of Eomes to T-bet expression in tumor-infiltrating CD8⁺ T cells by increasing Eomes and decreasing T-bet expression. 4-1BB-agonist immunotherapy was also associated with downregulated expression of the inhibitory receptors PD-1 and Lag3 on tumor-infiltrating CD8⁺ T cells, a molecular phenotype associated with subsequent attenuation of tumor growth. Furthermore, 4-1BB-agonist immunotherapy failed to effect tumor progression in mice with Eomes deficient T cells. However, upon resumption of tumor growth, tumor-infiltrating CD8⁺ T cells from treated animals continued to express high levels of Eomes as well as elevated levels of the inhibitory receptors PD-1 and Lag3. Our data suggest that tumor-infiltrating CD8⁺ T cells are poised between activation and inhibition as dictated by expression of both co-stimulatory receptors and inhibitory receptors and demonstrate that T cell expression of Eomes is necessary, but not sufficient, for efficacious 4-1BB-agonist-mediated immunotherapy.

Liver environment and HCV replication affect human T-cell phenotype and expression of inhibitory receptors

BACKGROUND & AIMS

There is an unclear relationship between inhibitory receptor expression on T cells and their ability to control viral infections. Studies of human immune cells have been mostly limited to T cells from blood, which is often not the site of infection. We investigated the relationship between T-cell location, expression of inhibitory receptors, maturation, and viral control using blood and liver T cells from patients with hepatitis C virus (HCV) and other viral infections.

METHODS

We analyzed 36 liver samples from HCV antibody-positive patients (30 from patients with chronic HCV infection, 5 from patients with sustained virological responses to treatment, and 1 from a patient with spontaneous clearance) with 19 paired blood samples and 51 liver samples from HCV-negative patients with 17 paired blood samples. Intrahepatic and circulating lymphocytes were extracted; T-cell markers and inhibitory receptors were quantified for total and virus-specific T cells by flow cytometry.

RESULTS

Levels of the markers PD-1 and 2B4 (but not CD160, TIM-3, or LAG-3) were increased on intrahepatic T cells from healthy and diseased liver tissues compared with T cells from blood. HCV-specific intrahepatic CD8(+) T cells from patients with chronic HCV infection were distinct in that they expressed TIM-3 along with PD-1 and 2B4. In comparison, HCV-specific CD8(+) T cells from patients with sustained virological responses and T cells that recognized cytomegalovirus lacked TIM-3 but expressed higher levels of LAG-3; these cells also had different memory phenotypes and proliferative capacity.

CONCLUSIONS

T cells from liver express different inhibitory receptors than T cells from blood, independent of liver disease. HCV-specific and cytomegalovirus-specific CD8(+) T cells can be differentiated based on their expression of inhibitory receptors; these correlate with their memory phenotype and levels of proliferation and viral control.

Genetically modified T-cell therapy for osteosarcoma

T-cell immunotherapy may offer an approach to improve outcomes for patients with osteosarcoma, who fail current therapies. In addition, it has the potential to reduce treatment-related complications for all patients. Generating tumor-specific T cells with conventional antigen presenting cells ex vivo is time consuming and often results in T-cell products with a low frequency of tumor-specific T cells. In addition, the generated T cells remain sensitive to the immunosuppressive tumor microenvironment. Genetic modification of T cells is one strategy to overcome these limitations. For example, T cells can be genetically modified to render them antigen specific, resistant to inhibitory factors, or increase their ability to home to tumor sites. Most genetic modification strategies have only been evaluated in preclinical models, however early phase clinical trials are in progress. In this chapter we review the current status of gene-modified T-cell therapy with special focus on osteosarcoma, highlighting potential antigenic targets, preclinical and clinical studies, and strategies to improve current T-cell therapy approaches.

Genetically modified T cells to target glioblastoma

Despite advances in surgical procedures, radiation, and chemotherapy the outcome for patients with glioblastoma (GBM) remains poor. While GBM cells express antigens that are potentially recognized by T cells, GBMs prevent the induction of GBM-specific immune responses by creating an immunosuppressive microenvironment. The advent of gene transfer has allowed the rapid generation of antigen-specific T cells as well as T cells with enhanced effector function. Here we review recent advances in the field of cell therapy with genetically modified T cells and how these advances might improve outcomes for patients with GBM in the future.

Clonal expansion of renal cell carcinoma-infiltrating T lymphocytes

T lymphocytes can mediate the destruction of cancer cells by virtue of their ability to recognize tumor-derived antigenic peptides that are presented on the cell surface in complex with HLA molecules and expand. Thus, the presence of clonally expanded T cells within neoplastic lesions is an indication of ongoing HLA-restricted T cell-mediated immune responses. Multiple tumors, including renal cell carcinomas (RCCs), are often infiltrated by significant amounts of T cells, the so-called tumor-infiltrating lymphocytes (TILs). In the present study, we analyzed RCC lesions (n = 13) for the presence of expanded T-cell clonotypes using T-cell receptor clonotype mapping. Surprisingly, we found that RCCs comprise relatively low numbers of distinct expanded T-cell clonotypes as compared with melanoma lesions. The numbers of different T-cell clonotypes detected among RCC-infiltrating lymphocytes were in the range of 1–17 (median = 5), and in several patients, the number of clonotypes expanded within tumor lesions resembled that observed among autologous peripheral blood mononuclear cells. Moreover, several of these clonotypes were identical in TILs and PBMCs. Flow cytometry data demonstrated that the general differentiation status of CD8⁺ TILs differed from that of circulating CD8⁺ T cells. Furthermore, PD-1 and LAG-3 were expressed by a significantly higher percentage of CD8⁺ RCC-infiltrating lymphocytes as compared with PBMCs obtained from RCC patients or healthy individuals. Thus, CD8⁺ TILs display a differentiated phenotype and express activation markers as well as surface molecules associated with the inhibition of T-cell functions. However, TILs are characterized by a low amount of expanded T-cell clonotypes.

The delicate balance of melanoma immunotherapy

The strategy of immune modulation for the treatment of cancer is being refined with the introduction of multiple new therapeutic agents into the clinic. Melanoma is a disease where many of these agents have demonstrated efficacy. The mechanisms of action of these agents exploit the counter-regulatory mechanisms of the immune response. However, these agents are also associated with immune-related adverse events (IRAEs), which represent tissue-specific inflammatory responses. These IRAEs highlight the delicate balance of immunologic homeostasis and, with some interventions, may occur more frequently in patients who sustain a therapeutic response. This review will discuss melanoma immunogenicity and immunotherapy. Furthermore, the spectrum and distinction between a reversible immune adverse event and autoimmunity will be highlighted.

Induced and natural regulatory T cells in the development of inflammatory bowel disease

The mucosal immune system mediates contact between the host and the trillions of microbes that symbiotically colonize the gastrointestinal tract. Failure to tolerate the antigens within this "extended self" can result in inflammatory bowel disease (IBD). Within the adaptive immune system, the most significant cells modulating this interaction are Foxp3 regulatory T (Treg) cells. Treg cells can be divided into 2 primary subsets: "natural" Treg cells and "adaptive" or "induced" Treg. Recent research suggests that these subsets serve to play both independent and synergistic roles in mucosal tolerance. Studies from both mouse models and human patients suggest that defects in Treg cells can play distinct causative roles in IBD. Numerous genetic, microbial, nutritional, and environmental factors that associate with IBD may also affect Treg cells. In this review, we summarize the development and function of Treg cells and how their regulatory mechanisms may fail, leading to a loss of mucosal tolerance. We discuss both animal models and studies of patients with IBD suggesting Treg cell involvement in IBD and consider how Treg cells may be used in future therapies.

Ipilimumab activity in advanced uveal melanoma

Uveal melanoma (UM) is a rare disease with a distinct molecular profile. About half of the patients with UM eventually develop metastatic disease. The prognosis of these patients remains poor. Treatment options are limited and none of them have been able to show a survival benefit. Ipilimumab was the first agent to show a survival benefit in patients with cutaneous melanoma in a randomized trial; however, there is limited published evidence for its role in the management of advanced UM. Here, we report our experience of ipilimumab in five patients with advanced UM treated at an academic cancer centre in the UK. Two patients had durable stable disease and three developed progressive disease. Of the patients with stable disease, one maintained disease control at 11 months from the commencement of treatment with ∼10% reduction in tumour volume compared with the baseline, and the second patient progressed after 15 months. We also examined the tumour kinetics and response patterns that resembled that of ipilimumab in cutaneous melanoma. Given the lack of randomized trial data, our findings indicate that ipilimumab might be a reasonable treatment option for patients with advanced UM.

At the bedside: CTLA-4- and PD-1-blocking antibodies in cancer immunotherapy

It is increasingly appreciated that cancers are recognized by the immune system, and under some circumstances, the immune system may control or even eliminate tumors. The modulation of signaling via coinhibitory or costimulatory receptors expressed on T cells has proven to be a potent way to amplify antitumor immune responses. This approach has been exploited successfully for the generation of a new class of anticancer therapies, "checkpoint-blocking" antibodies, exemplified by the recently FDA-approved agent, ipilimumab, an antibody that blocks the coinhibitory receptor CTLA-4. Capitalizing on the success of ipilimumab, agents that target a second coinhibitory receptor, PD-1, or its ligand, PD-L1, are in clinical development. Lessons learned from treating patients with CTLA-4 and PD-1 pathway-blocking antibodies will be reviewed, with a focus on concepts likely to inform the clinical development and application of agents in earlier stages of development. See related review At the bench: Preclinical rationale for CTLA-4 and PD-1 blockade as cancer immunotherapy.

Immunomodulatory monoclonal antibodies combined with peptide vaccination provide potent immunotherapy in an aggressive murine neuroblastoma model

PURPOSE

Neuroblastoma is one of the commonest extracranial tumors of childhood. The majority of patients present with metastatic disease for which outcome remains poor. Immunotherapy is an attractive therapeutic approach for this disease, and a number of neuroblastoma tumor antigens have been identified. Here, we examine the therapeutic potential of combining immunomodulatory monoclonal antibodies (mAb) with peptide vaccination in murine neuroblastoma models.

EXPERIMENTAL DESIGN

Neuroblastoma-bearing mice were treated with mAb targeting 4-1BB, CD40, and CTLA-4 alone, or in combination with a peptide derived from the tumor antigen survivin (GWEDPPNDI). Survivin-specific immune response and therapeutic efficacy were assessed.

RESULTS

In the Neuro2a model, treatment of established tumor with anti-4-1BB, anti-CD40, or anti-CTLA-4 mAb results in tumor regression and long-term survival in 40% to 60% of mice. This is dependent on natural killer (NK) and CD8(+) T cells and is associated with tumor CD8(+) lymphocyte infiltrate. Successful therapy is achieved only if mAb is given to mice once tumors are established, suggesting dependence on sufficient tumor to provide antigen. In the more aggressive AgN2a and NXS2 models, single-agent mAb therapy provides ineffective therapy. However, if mAb (anti-CTLA-4) is given in conjunction with survivin peptide vaccination, then 60% long-term survival is achieved. This is associated with the generation of survivin-specific T-cell immunity, which again is only shown in the presence of tumor antigen.

CONCLUSIONS

These data suggest that the combination of antigen and costimulatory mAb may provide effective immunotherapy against neuroblastoma and may be of particular use in the minimal residual disease setting.

FcγRΙΙB controls the potency of agonistic anti-TNFR mAbs

Isotype plays a crucial role in therapeutic monoclonal antibody (mAb) function, mediated in large part through differences in Fcγ receptor (FcγR) interaction. Monoclonal Abs such as rituximab and alemtuzumab, which bind target cells directly, are designed for efficient recruitment of immune effector cells through their activatory FcγR engagement to mediate maximal target cell killing. In this setting, binding to inhibitory FcγRIIB is thought to inhibit function, making mAbs with high activatory/inhibitory (A/I) FcγR binding ratios, such as mouse IgG2a and human IgG1, the first choice for this role. In contrast, exciting new data show that agonistic mAbs directed against the tumour necrosis factor receptor superfamily member CD40 require interaction with FcγRIIB for in vivo function. Such ligation activates antigen-presenting cells, promotes myeloid and CTL responses and potentially stimulates effective anti-cancer immunity. It appears that the role of FcγRIIB is to mediate mAb hyper-crosslinking to allow CD40 downstream intracellular signalling. Previous work has shown that mAbs directed against other TNFR family members, Fas and death receptor 5 and probably death receptor 4, also require FcγRIIB hyper-crosslinking to promote target cell apoptosis, suggesting a common mechanism of action. In mouse models, IgG1 is optimal for these agents as it binds to FcγRIIB with tenfold higher affinity than IgG2a and hence has a relatively low A:I FcγR binding ratio. In contrast, human IgG isotypes have a universally low affinity for FcγRIIB, but in the case of human IgG1, engineering the Fc to increase its affinity for FcγRIIB can potentially overcome this problem. Thus, modifying the A/I binding ratio of human IgG Fc can be used to optimise different types of therapeutic activity by enhancing cytotoxic or hyper-crosslinking function.

Exploiting CTLA-4, PD-1 and PD-L1 to reactivate the host immune response against cancer

The past few years have witnessed something of a renaissance in the field of cancer immunotherapy, relating largely to the clinical advances that have been associated with the development of monoclonal antibodies targeting the immune inhibitory co-receptors CTLA-4 and PD-1 and to the pursuit of genetically modified antigen-redirected adoptive T-cell therapies. These advances are based on a more substantial understanding of the factors restricting effective immune therapies that has been derived from the study of pre-clinical models of tumour growth in immune competent mice. Just as the recognition of the importance of positive co-stimulatory signaling has been instrumental to recent advances in the development of genetically modified antigen-specific adoptive cellular therapies, an increasing awareness of the ability of tumours to subvert multiple immune inhibitory pathways, effectively blunting the development or expansion of any anti-tumour immunity, is fostering the development of novel therapies that appear active as monotherapies but may achieve their greatest impact in combinatorial regimens. This mini-review will focus on attempts to target co-inhibitory members of the immunoglobulin superfamily.

Combination immunotherapy approaches

Combination immunotherapy approaches involving radiation, chemotherapy, androgen manipulation and T-cell modulation have been studied extensively in animal models, setting the stage for clinical trials. Radiation therapy, in particular, is an interesting modality in this regard, leading to synergistic efficacy when used in combination with immunotherapies in several models. Chemotherapy, the foundation of treatment of metastatic disease, may also augment the immune response to cancer; however, the potential immunosuppressive effects of chemotherapy render issues of dosing and timing critical. Perhaps, the most exciting combinatorial approach may be the co-administration of multiple immunological treatments. For example, in preclinical investigations, combined blockade of programmed death-1 (PD1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), which have key roles in the negative regulation of T-cell activation, has been shown to enhance antitumour immune responses compared with either agent alone. Taken together, the available data provide a strong rationale for initiating combination clinical trials, but lend a note of caution in that issues of dosing and timing likely require careful exploration in a phase II setting.

Harnessing the power of the immune system to target cancer

For many years, immunotherapeutic approaches for cancer held more promise than actual clinical benefit for the majority of patients. However, several recent key advances in tumor immunology have now turned the tide in favor of immunotherapy for the treatment of many different cancer types. In this review, we describe four of the most effective immunotherapeutic approaches currently used in the clinic: cancer vaccines, immunostimulatory agents, adoptive T cell therapy, and immune checkpoint blockade. In addition, we discuss some of the most promising future strategies that aim to utilize multiple immunotherapies or combine them with other approaches to more effectively target cancer.

Advances in the development of cancer immunotherapies

Manipulating the immune system in order to induce clinically relevant responses against cancer is a longstanding goal. Interventions to enhance tumor-specific immunity through vaccination, sustaining effector T cell activation, or increasing the numbers of tumor-specific T cells using ex vivo expansion, have all resulted in clinical successes. Here, we examine recent clinical advances and major ongoing studies in the field of cancer immunotherapy. Single agents have so far benefited a limited proportion of patients, and future studies combining different types of immunotherapies and other therapeutic modalities, such as drugs against specific signaling pathways driving cancer cell growth, are needed to pave the way for the development of effective anticancer treatments causing durable responses.

Oncolytic Newcastle disease virus for cancer therapy: old challenges and new directions

Newcastle disease virus (NDV) is an avian paramyxovirus, which has been demonstrated to possess significant oncolytic activity against mammalian cancers. This review summarizes the research leading to the elucidation of the mechanisms of NDV-mediated oncolysis, as well as the development of novel oncolytic agents through the use of genetic engineering. Clinical trials utilizing NDV strains and NDV-based autologous tumor cell vaccines will expand our knowledge of these novel anticancer strategies and will ultimately result in the successful use of the virus in the clinical setting.

Inhibitory receptors on lymphocytes: insights from infections

Costimulatory and inhibitory receptors are critical regulators of adaptive immune cell function. These pathways regulate the initiation and termination of effective immune responses to infections while limiting autoimmunity and/or immunopathology. This review focuses on recent advances in our understanding of inhibitory receptor pathways and their roles in different diseases and/or infections, emphasizing potential clinical applications and important unanswered mechanistic questions. Although significant progress has been made in defining the influence of inhibitory receptors at the cellular level, relatively little is known about the underlying molecular pathways. We discuss our current understanding of the molecular mechanisms for key inhibitory receptor pathways, highlight major gaps in knowledge, and explore current and future clinical applications.

Recombinant human CD137L for cancer immunotherapy: effects of different fusions and linkers on its activity

Co-stimulatory molecules can be efficiently produced as a recombinant protein in E. coli with a large range of applications in the fields of immunotherapy. However, whether, different fusions that would affect their functions have rarely been analyzed. To explore the effects of different fusions and linkers on the molecular conformation and activity of CD137 ligand (CD137L), a recombinant human CD137L protein (rhCD137L) library, which consists of the entire extracellular domain of human CD137L fused to N- or C-terminal His-tag through different linkers, was constructed and all rhCD137Ls were, respectively, expressed in E. coli BL21 (DE3) strain carrying a chaperone plasmid pG-Tf2. After purification of the soluble rhCD137Ls, the recombinant fusion proteins could markedly promote the growth of activated T cells, but their effects on cytokine productions were different from each other. The present work indicated that, although all rhCD137Ls have desired biological activity, different fusions and linkers did affect their structures and functions. Consequently, rational design of a library is a necessary and feasible approach for fusion proteins in order to obtain a satisfactory drug candidate for further development.

Soluble expression of recombinant human CD137 ligand in Escherichia coli by co-expression of chaperones

CD137 ligand (CD137L) is a member of the tumor-necrosis factor superfamily that binds CD137 to provide positive co-stimulatory signals for T cells activation. Co-stimulation through CD137/CD137L has become one of the promising approaches for cancer therapy. Previous reports have shown that CD137L expressed in Escherichia coli resulted in inclusion bodies or low yield. In this study, the effects of five different chaperone teams on the soluble expression of recombinant human CD137L protein were explored and analyzed. The poor expression of CD137L in the cytoplasm of E. coli was improved significantly by co-expression of chaperone GroES-GroEL-Tf. After dual induction and affinity chromatography, purified recombinant CD137L was obtained at a yield of 3 mg protein per liter with purity greater than 98% from original undetectable level. Additionally, the purified recombinant CD137L could bind CD137-positive cells in a dose-dependent manner, markedly promote the growth of activated mice T cells, and elevate the release of IL-2. The present work provides an effective system for soluble expression of functional human co-stimulatory molecule CD137L, which will facilitate the clinical developments of recombinant protein drugs.

Chimeric antigen receptors: a costimulatory boost promotes immunological memory to B-cell malignancies

Cellular immunotherapies offer perhaps the best proof of concept of the ability of immune cells to eradicate malignancy. However, the majority of these data derive from either the use of expanded tumor-infiltrating lymphocytes to treat metastatic melanoma or the use of donor lymphocytes in relapsed hematological malignancies following allogeneic hematopoietic stem cell transplantation. Genetic engineering of T cells to redirect specificity against tumor-associated antigens potentially overcomes one of the major hurdles to more widespread application. Despite early evidence of possible activity, limited in vivo expansion and persistence of adoptively transferred cells has been associated with disappointing clinical efficacy. A report from Porter and colleagues now demonstrates more fully the potential of such genetic modification in a patient with chronic lymphocytic leukemia, illustrating that when delivered in the right setting with appropriate costimulatory signaling, these cells can expand and persist, and in doing so effect quite remarkable anti-tumor activity.

The CD4-like molecule LAG-3, biology and therapeutic applications

IMPORTANCE OF THE FIELD

Promising immunotherapeutic agents targeting co-stimulatory pathways are currently being tested in clinical trials. One player in this array of regulatory pathways is the LAG-3/MHC class II axis. The lymphocyte activation gene-3 (LAG-3) is a negative co-stimulatory receptor that modulates T cell homeostasis, proliferation and activation. A recombinant soluble dimeric form of LAG-3 (sLAG-3-Ig, IMP321) shows adjuvant properties and enhances immunogenicity of tumor vaccines. Recent clinical trials produced encouraging results, especially when the human dimeric soluble form of LAG-3 (hLAG-3-Ig) was used in combination with chemotherapy.

AREAS COVERED IN THIS REVIEW

The biological relevance of LAG-3 in vivo. Pre-clinical data demonstrating adjuvant properties, as well as the improvement of tumor immunity by sLAG-3-Ig. Recent advances in the clinical development of the therapeutic reagent IMP321, hLAG-3-Ig, for cancer treatment.

WHAT THE READER WILL GAIN

This review summarizes preclinical and clinical data on the biological functions of LAG-3.

TAKE HOME MESSAGE

The LAG-3 inhibitory pathway is attracting attention, in the light of recent studies demonstrating its role in T cell unresponsiveness, and Treg function after chronic antigen stimulation. As a soluble recombinant dimer, the sLAG-3-Ig protein acts as an adjuvant for therapeutic induction of T cell responses, and may be beneficial to cancer patients when used in combination therapies.

Vascular disrupting agent DMXAA enhances the antitumor effects generated by therapeutic HPV DNA vaccines

Antigen-specific immunotherapy using DNA vaccines has emerged as an attractive approach for the control of tumors. Another novel cancer therapy involves the employment of the vascular disrupting agent, 5,6-dimethylxanthenone-4-acetic acid (DMXAA). In the current study, we aimed to test the combination of DMXAA treatment with human papillomavirus type 16 (HPV-16) E7 DNA vaccination to enhance the antitumor effects and E7-specific CD8+ T cell immune responses in treated mice. We determined that treatment with DMXAA generates significant therapeutic effects against TC-1 tumors but does not enhance the antigen-specific immune responses in tumor bearing mice. We then found that combination of DMXAA treatment with E7 DNA vaccination generates potent antitumor effects and E7-specific CD8+ T cell immune responses in the splenocytes of tumor bearing mice. Furthermore, the DMXAA-mediated enhancement or suppression of E7-specific CD8+ T cell immune responses generated by CRT/E7 DNA vaccination was found to be dependent on the time of administration of DMXAA and was also applicable to other antigen-specific vaccines. In addition, we determined that inducible nitric oxide synthase (iNOS) plays a role in the immune suppression caused by DMXAA administration before DNA vaccination. Our study has significant implications for future clinical translation.

Ipilimumab: attenuation of an inhibitory immune checkpoint improves survival in metastatic melanoma

Evaluation of: Hodi FS, O'Day SJ, McDermott DF et al. Improved survival with ipilimumab in patients with metastatic melanoma. N. Engl. J. Med. 363(8), 711-723 (2010). Interference with the inhibitory immune regulatory checkpoints that act to constrain overly exuberant immune responses and help to maintain peripheral tolerance represents an exciting new paradigm in tumor immunotherapy. We review the study of Hodi and colleagues evaluating the role of blockade of one of these pathways (cytotoxic T-lymphocyte antigen-4) with a monoclonal antibody (ipilimumab, developed by Medarex, NJ, USA and Bristol-Myers Squibb, NY, USA) in patients with advanced melanoma who had failed prior treatments. The randomized Phase III study demonstrates superior overall survival in patients receiving ipilimumab, either alone or in combination with a gp100 peptide vaccine, compared with those receiving the vaccine alone. The results represent the first positive randomized clinical trial ever reported in patients with metastatic melanoma in terms of overall survival, the first showing a beneficial effect of a melanoma treatment in the second-line setting, and the first demonstration that blockade of an immune-inhibitory pathway can be an effective cancer therapeutic.

Translating p53 into the clinic

Mutations in the TP53 gene are a feature of 50% of all reported cancer cases. In the other 50% of cases, the TP53 gene itself is not mutated but the p53 pathway is often partially inactivated. Cancer therapies that target specific mutant genes are proving to be highly active and trials assessing agents that exploit the p53 system are ongoing. Many trials are aimed at stratifying patients on the basis of TP53 status. In another approach, TP53 is delivered as a gene therapy; this is the only currently approved p53-based treatment. The p53 protein is overexpressed in many cancers and p53-based vaccines are undergoing trials. Processed cell-surface p53 is being exploited as a target for protein-drug conjugates, and small-molecule drugs that inhibit the activity of MDM2, the E3 ligase that regulates p53 levels, have been developed by several companies. The first MDM2 inhibitors are being trialed in both hematologic and solid malignancies. Finally, the first agent found to restore the active function of mutant TP53 has just entered the clinic. Here we discuss the basis of these trials and the future of p53-based therapy.