Tumor immunogenicity determines the effect of B7 costimulation on T cell-mediated tumor immunity

Phase I studies of davoceticept (ALPN-202), a PD-L1-dependent CD28 co-stimulator and dual PD-L1/CTLA-4 inhibitor, as monotherapy and in combination with pembrolizumab in advanced solid tumors (NEON-1 and NEON-2)

BACKGROUND

Davoceticept (ALPN-202) is an Fc fusion of a CD80 variant immunoglobulin domain designed to mediate programmed death-ligand 1 (PD-L1)-dependent CD28 co-stimulation while inhibiting the PD-L1 and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) checkpoints. The safety and efficacy of davoceticept monotherapy and davoceticept and pembrolizumab combination therapy in adult patients with advanced solid tumors were explored in NEON-1 and NEON-2, respectively.

METHODS

In NEON-1 (n=58), davoceticept 0.001-10 mg/kg was administered intravenous either once weekly (Q1W) or once every 3 weeks (Q3W). In NEON-2 (n=29), davoceticept was administered intravenously at 2 dose levels (0.1 or 0.3 mg/kg) Q1W or Q3W with pembrolizumab (400 mg once every 6 weeks). In both studies, primary endpoints included incidence of dose-limiting toxicities (DLT); type, incidence, and severity of adverse events (AEs) and laboratory abnormalities; and seriousness of AEs. Secondary endpoints included antitumor efficacy assessed using RECIST v1.1, pharmacokinetics, anti-drug antibodies, and pharmacodynamic biomarkers.

RESULTS

The incidence of treatment-related AEs (TRAEs) and immune-related adverse events (irAEs) was 67% (39/58) and 36% (21/58) with davoceticept monotherapy, and 62% (18/29) and 31% (9/29) with davoceticept and pembrolizumab combination, respectively. The incidence of ≥grade (Gr)3 TRAEs and ≥Gr3 irAEs was 12% (7/58) and 5% (3/58) with davoceticept monotherapy, and 24% (7/29) and 10% (3/29) with davoceticept and pembrolizumab combination, respectively. One DLT of Gr3 immune-related gastritis occurred during davoceticept monotherapy 3 mg/kg Q3W. During davoceticept combination with pembrolizumab, two Gr5 cardiac DLTs occurred; one instance each of cardiogenic shock (0.3 mg/kg Q3W, choroidal melanoma metastatic to the liver) and immune-mediated myocarditis (0.1 mg/kg Q3W, microsatellite stable metastatic colorectal adenocarcinoma), prompting early termination of both studies. Across both studies, five patients with renal cell carcinoma (RCC) exhibited evidence of clinical benefit (two partial response, three stable disease).

CONCLUSIONS

Davoceticept was generally well tolerated as monotherapy at intravenous doses up to 10 mg/kg. Evidence of clinical activity was observed with davoceticept monotherapy and davoceticept in combination with pembrolizumab, notably in RCC. However, two fatal cardiac events occurred with the combination of low-dose davoceticept and pembrolizumab. Future clinical investigation with davoceticept should not consider combination with programmed death-1-inhibitor anticancer mechanisms, until its safety profile is more fully elucidated.

TRIAL REGISTRATION NUMBER

NEON-1 (NCT04186637) and NEON-2 (NCT04920383).

Up-regulated PLA2G10 in cancer impairs T cell infiltration to dampen immunity

T cells are often absent from human cancer tissues during both spontaneously induced immunity and therapeutic immunotherapy, even in the presence of a functional T cell-recruiting chemokine system, suggesting the existence of T cell exclusion mechanisms that impair infiltration. Using a genome-wide in vitro screening platform, we identified a role for phospholipase A2 group 10 (PLA2G10) protein in T cell exclusion. PLA2G10 up-regulation is widespread in human cancers and is associated with poor T cell infiltration in tumor tissues. PLA2G10 overexpression in immunogenic mouse tumors excluded T cells from infiltration, resulting in resistance to anti-PD-1 immunotherapy. PLA2G10 can hydrolyze phospholipids into small lipid metabolites, thus inhibiting chemokine-mediated T cell mobility. Ablation of PLA2G10's enzymatic activity enhanced T cell infiltration and sensitized PLA2G10-overexpressing tumors to immunotherapies. Our study implicates a role for PLA2G10 in T cell exclusion from tumors and suggests a potential target for cancer immunotherapy.

Clinicopathologic Evaluation of CD80, CD86, and PD-L1 Expressions with Immunohistochemical Methods in Malignant Melanoma Patients

OBJECTIVE

Diagnostic and prognostic biomarkers for malignant melanoma are crucial for treatment and for developing targeted therapies. Malignant melanoma is a highly immunogenic tumor, and its regression, treatment, and prognostic evaluation are directly related to escape from immune destruction. Therefore, we aimed to determine the expression levels of CD80, CD86, and PD -L1 in malignant melanoma tissue samples by immunohistochemistry and to investigate the possible relationship between these proteins and the clinicopathological features in this study.

MATERIAL AND METHODS

Hematoxylin and eosin staining and immunohistochemical staining for CD80, CD86, and PD-L1 were evaluated for clinical data, survival, prognosis, tumor location, malignant melanoma subtypes, tumor size, and prognostic findings.

RESULTS

Higher survival rates were observed in patients with lower PD-L1 staining scores in the tumor. The 5-year survival was higher in patients with CD80-positive and CD86-positive biopsies. Mortality was lower in superficial spreading melanoma and Lentigo maligna melanoma types, whereas staining positivity of CD80 and CD86 was higher. Furthermore, a relationship between clinical stage and Breslow thickness ( < 2mm/≥2mm), tumor ulceration, lymph node metastasis, and CD80 and CD86 expression was also identified.

CONCLUSION

Our findings suggest that PD-L1, CD80, and CD86 expression are essential in malignant melanoma and could be used as prognostic markers.

Immunobiology of Melanoma

Despite the ability of immune-based interventions to dramatically increase the survival of patients with melanoma, a significant subset fail to benefit from this treatment, underscoring the need for accurate means to identify the patient population likely to respond to immunotherapy. Understanding how melanoma evades natural or manipulated immune responses could provide the information needed to identify such resistant individuals. Efforts to address this challenge are hampered by the vast immune diversity characterizing tumor microenvironments that remain largely understudied. It is thus important to more clearly elucidate the complex interactions that take place between the tumor microenvironment and host immune system.

Using Dictyostelium to Develop Therapeutics for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) involves damage to lungs causing an influx of neutrophils from the blood into the lung airspaces, and the neutrophils causing further damage, which attracts more neutrophils in a vicious cycle. There are ∼190,000 cases of ARDS per year in the US, and because of the lack of therapeutics, the mortality rate is ∼40%. Repelling neutrophils out of the lung airspaces, or simply preventing neutrophil entry, is a potential therapeutic. In this minireview, we discuss how our lab noticed that a protein called AprA secreted by growing Dictyostelium cells functions as a repellent for Dictyostelium cells, causing cells to move away from a source of AprA. We then found that AprA has structural similarity to a human secreted protein called dipeptidyl peptidase IV (DPPIV), and that DPPIV is a repellent for human neutrophils. In animal models of ARDS, inhalation of DPPIV or DPPIV mimetics blocks neutrophil influx into the lungs. To move DPPIV or DPPIV mimetics into the clinic, we need to know how this repulsion works to understand possible drug interactions and side effects. Combining biochemistry and genetics in Dictyostelium to elucidate the AprA signal transduction pathway, followed by drug studies in human neutrophils to determine similarities and differences between neutrophil and Dictyostelium chemorepulsion, will hopefully lead to the safe use of DPPIV or DPPIV mimetics in the clinic.

Tumor-targeted CD28 bispecific antibodies enhance the antitumor efficacy of PD-1 immunotherapy

Monoclonal antibodies that block the programmed cell death 1 (PD-1) checkpoint have revolutionized cancer immunotherapy. However, many major tumor types remain unresponsive to anti-PD-1 therapy, and even among responsive tumor types, most of the patients do not develop durable antitumor immunity. It has been shown that bispecific antibodies activate T cells by cross-linking the TCR/CD3 complex with a tumor-specific antigen (TSA). The class of TSAxCD3 bispecific antibodies have generated exciting results in early clinical trials. We have recently described another class of "costimulatory bispecifics" that cross-link a TSA to CD28 (TSAxCD28) and cooperate with TSAxCD3 bispecifics. Here, we demonstrate that these TSAxCD28 bispecifics (one specific for prostate cancer and the other for epithelial tumors) can also synergize with the broader anti-PD-1 approach and endow responsiveness-as well as long-term immune memory-against tumors that otherwise do not respond to anti-PD-1 alone. Unlike CD28 superagonists, which broadly activate T cells and induce cytokine storm, TSAxCD28 bispecifics display little or no toxicity when used alone or in combination with a PD-1 blocker in genetically humanized immunocompetent mouse models or in primates and thus may provide a well-tolerated and "off the shelf" combination approach with PD-1 immunotherapy that can markedly enhance antitumor efficacy.

Nanomedicine-Combined Immunotherapy for Cancer

BACKGROUND

Immunotherapy for cancer includes Chimeric Antigen Receptor (CAR)-T cells, CAR-natural Killer (NK) cells, PD1, and the PD-L1 inhibitor. However, the proportion of patients who respond to cancer immunotherapy is not satisfactory. Concurrently, nanotechnology has experienced a revolution in cancer diagnosis and therapy. There are few clinically approved nanoparticles that can selectively bind and target cancer cells and incorporate molecules, although many therapeutic nanocarriers have been approved for clinical use. There are no systematic reviews outlining how nanomedicine and immunotherapy are used in combination to treat cancer.

OBJECTIVE

This review aims to illustrate how nanomedicine and immunotherapy can be used for cancer treatment to overcome the limitations of the low proportion of patients who respond to cancer immunotherapy and the rarity of nanomaterials in clinical use.

METHODS

A literature review of MEDLINE, PubMed / PubMed Central, and Google Scholar was performed. We performed a structured search of literature reviews on nanoparticle drug-delivery systems, which included photodynamic therapy, photothermal therapy, photoacoustic therapy, and immunotherapy for cancer. Moreover, we detailed the advantages and disadvantages of the various nanoparticles incorporated with molecules to discuss the challenges and solutions associated with cancer treatment.

CONCLUSION

This review identified the advantages and disadvantages associated with improving health care and outcomes. The findings of this review confirmed the importance of nanomedicinecombined immunotherapy for improving the efficacy of cancer treatment. It may become a new way to develop novel cancer therapeutics using nanomaterials to achieve synergistic anticancer immunity.

The Origin and Immune Recognition of Tumor-Specific Antigens

The dominant paradigm holds that spontaneous and therapeutically induced anti-tumor responses are mediated mainly by CD8 T cells and directed against tumor-specific antigens (TSAs). The presence of specific TSAs on cancer cells can only be proven by mass spectrometry analyses. Bioinformatic predictions and reverse immunology studies cannot provide this type of conclusive evidence. Most TSAs are coded by unmutated non-canonical transcripts that arise from cancer-specific epigenetic and splicing aberrations. When searching for TSAs, it is therefore important to perform mass spectrometry analyses that interrogate not only the canonical reading frame of annotated exome but all reading frames of the entire translatome. The majority of aberrantly expressed TSAs (aeTSAs) derive from unstable short-lived proteins that are good substrates for direct major histocompatibility complex (MHC) I presentation but poor substrates for cross-presentation. This is an important caveat, because cancer cells are poor antigen-presenting cells, and the immune system, therefore, depends on cross-presentation by dendritic cells (DCs) to detect the presence of TSAs. We, therefore, postulate that, in the untreated host, most aeTSAs are undetected by the immune system. We present evidence suggesting that vaccines inducing direct aeTSA presentation by DCs may represent an attractive strategy for cancer treatment.

Membrane insertion and intercellular transfer of glycosylphosphatidylinositol-anchored proteins: potential therapeutic applications

Anchorage of a subset of cell surface proteins in eukaryotic cells is mediated by a glycosylphosphatidylinositol (GPI) moiety covalently attached to the carboxy-terminus of the protein moiety. Experimental evidence for the potential of GPI-anchored proteins (GPI-AP) of being released from cells into the extracellular environment has been accumulating, which involves either the loss or retention of the GPI anchor. Release of GPI-AP from donor cells may occur spontaneously or in response to endogenous or environmental signals. The experimental evidence for direct insertion of exogenous GPI-AP equipped with the complete anchor structure into the outer plasma membrane bilayer leaflets of acceptor cells is reviewed as well as the potential underlying molecular mechanisms. Furthermore, promiscuous transfer of certain GPI-AP between plasma membranes of different cells in vivo under certain (patho)physiological conditions has been reported. Engineering of target cell surfaces using chimeric GPI-AP with complete GPI anchor may be useful for therapeutic applications.

Multimodel preclinical platform predicts clinical response of melanoma to immunotherapy

Although immunotherapy has revolutionized cancer treatment, only a subset of patients demonstrate durable clinical benefit. Definitive predictive biomarkers and targets to overcome resistance remain unidentified, underscoring the urgency to develop reliable immunocompetent models for mechanistic assessment. Here we characterize a panel of syngeneic mouse models, representing a variety of molecular and phenotypic subtypes of human melanomas and exhibiting their diverse range of responses to immune checkpoint blockade (ICB). Comparative analysis of genomic, transcriptomic and tumor-infiltrating immune cell profiles demonstrated alignment with clinical observations and validated the correlation of T cell dysfunction and exclusion programs with resistance. Notably, genome-wide expression analysis uncovered a melanocytic plasticity signature predictive of patient outcome in response to ICB, suggesting that the multipotency and differentiation status of melanoma can determine ICB benefit. Our comparative preclinical platform recapitulates melanoma clinical behavior and can be employed to identify mechanisms and treatment strategies to improve patient care.

Whole leukemia cell vaccines: Past progress and future directions

It has long been recognized that allogeneic hematopoietic stem cell transplantation can reduce the risk of leukemia relapse by inducing the graft-versus-leukemia effect. However, allogeneic stem cell transplantation is also known to be able to cause graft-versus-host disease, which can cause considerable morbidity and even mortality in patients receiving allogeneic hematopoietic stem cell transplantation. Therefore, to elicit leukemia-specific immune responses without alloimmune reaction, the possibilities of active immunotherapy methods such as leukemia vaccines have been studied for decades. Among various types of leukemia vaccines, whole leukemia cell vaccines are known to be able to induce immune responses against multiple unknown antigens without the need for adoptive transfer of dendritic cells. In this review, we will discuss the past progress of whole leukemia cell vaccines, with a focus on strategies to enhance their immunogenicity. We will also present the future directions of whole leukemia cell vaccines along with addressing newly emerging concepts, such as immunogenic cell death and necroptosis. We will not discuss in detail other factors that can reduce the therapeutic efficacy of whole leukemia cell vaccines such as various immunosuppressive mechanisms of leukemia.

PD-L1 Detection-Pearls and Pitfalls Associated With Current Methodologies Focusing on Entities Relevant to Dermatopathology

PD-L1 is a transmembrane glycoprotein with an extracellular as well as an intracellular cytoplasmic domain. Physiologically, it plays a pivotal role in regulating T-cell activation and tolerance. Many tumor cells have exploited this regulatory mechanism by overexpressing PD-L1 in an effort to escape immunologic surveillance. In this review, we parse the literature regarding the prognostic value of tumoral PD-L1 expression before discussing the various methodologies as well as the pearls and pitfalls associated with each for predicting response to anti-PD-1/PD-L1 therapies. Special attention is given to cutaneous entities in which PD-L1 expression has been documented with an emphasis on cutaneous malignancies that have seen the broadest applications of anti-PD-L1/PD-1 therapies. Currently, immunohistochemistry is the method that is most commonly used for detection of PD-L1. However, with the wide array of immunohistochemistry protocols and staining platforms available in the market, there seems to be different cutoffs not just for different entities but also for the same entity. This review is an attempt to address the need for standardization and validation of existing protocols for PD-L1 detection.

Siglec-15 as an immune suppressor and potential target for normalization cancer immunotherapy

Overexpression of the B7-H1 (PD-L1) molecule in the tumor microenvironment (TME) is a major immune evasion mechanism in some patients with cancer, and antibody blockade of the B7-H1/PD-1 interaction can normalize compromised immunity without excessive side-effects. Using a genome-scale T cell activity array, we identified Siglec-15 as a critical immune suppressor. While only expressed on some myeloid cells normally, Siglec-15 is broadly upregulated on human cancer cells and tumor-infiltrating myeloid cells, and its expression is mutually exclusive to B7-H1, partially due to its induction by macrophage colony-stimulating factor and downregulation by IFN-γ. We demonstrate that Siglec-15 suppresses antigen-specific T cell responses in vitro and in vivo. Genetic ablation or antibody blockade of Siglec-15 amplifies anti-tumor immunity in the TME and inhibits tumor growth in some mouse models. Taken together, our results support Siglec-15 as a potential target for normalization cancer immunotherapy.

From the Hellstrom paradox toward cancer cure

Several decades ago we published some of the first papers showing that both murine and human cancers are recognized in vitro as immunologically foreign and that this is the case also in the presence of a growing tumor. The latter situation, sometimes referred to as the Hellstrom paradox, implies that the tumor is protected in vivo by a highly immunosuppressive environment. After many disappointments, the discovery that tumor-related immunosuppression can be counteracted by administrating monoclonal antibodies (mAbs) to checkpoint inhibitors such as CTLA-4, PD-1, and PD-L1 is now revolutionizing cancer therapy. Over the past several years we have applied mouse models in attempts to further improve the ability of such mAbs to cause long-term complete tumor rejection. This review is focused on that work and emphasizes that successful immunotherapy is associated with a shift from a tumor-promoting Th2 inflammation to a tumor-inhibiting Th1 response.

Fibrinogen-like Protein 1 Is a Major Immune Inhibitory Ligand of LAG-3

Lymphocyte-activation gene 3 (LAG-3) is an immune inhibitory receptor, with major histocompatibility complex class II (MHC-II) as a canonical ligand. However, it remains controversial whether MHC-II is solely responsible for the inhibitory function of LAG-3. Here, we demonstrate that fibrinogen-like protein 1 (FGL1), a liver-secreted protein, is a major LAG-3 functional ligand independent from MHC-II. FGL1 inhibits antigen-specific T cell activation, and ablation of FGL1 in mice promotes T cell immunity. Blockade of the FGL1-LAG-3 interaction by monoclonal antibodies stimulates tumor immunity and is therapeutic against established mouse tumors in a receptor-ligand inter-dependent manner. FGL1 is highly produced by human cancer cells, and elevated FGL1 in the plasma of cancer patients is associated with a poor prognosis and resistance to anti-PD-1/B7-H1 therapy. Our findings reveal an immune evasion mechanism and have implications for the design of cancer immunotherapy.

Adjuvant effect of the novel TLR1/TLR2 agonist Diprovocim synergizes with anti-PD-L1 to eliminate melanoma in mice

Successful cancer immunotherapy entails activation of innate immune receptors to promote dendritic cell (DC) maturation, antigen presentation, up-regulation of costimulatory molecules, and cytokine secretion, leading to activation of tumor antigen-specific cytotoxic T lymphocytes (CTLs). Here we screened a synthetic library of 100,000 compounds for innate immune activators using TNF production by THP-1 cells as a readout. We identified and optimized a potent human and mouse Toll-like receptor (TLR)1/TLR2 agonist, Diprovocim, which exhibited an EC₅₀ of 110 pM in human THP-1 cells and 1.3 nM in primary mouse peritoneal macrophages. In mice, Diprovocim-adjuvanted ovalbumin immunization promoted antigen-specific humoral and CTL responses and synergized with anti-PD-L1 treatment to inhibit tumor growth, generating long-term antitumor memory, curing or prolonging survival of mice engrafted with the murine melanoma B16-OVA. Diprovocim induced greater frequencies of tumor-infiltrating leukocytes than alum, of which CD8 T cells were necessary for the antitumor effect of immunization plus anti-PD-L1 treatment.

Local Activation of p53 in the Tumor Microenvironment Overcomes Immune Suppression and Enhances Antitumor Immunity

Mutations in tumor suppressor p53 remain a vital mechanism of tumor escape from apoptosis and senescence. Emerging evidence suggests that p53 dysfunction also fuels inflammation and supports tumor immune evasion, thereby serving as an immunological driver of tumorigenesis. Therefore, targeting p53 in the tumor microenvironment (TME) also represents an immunologically desirable strategy for reversing immunosuppression and enhancing antitumor immunity. Using a pharmacological p53 activator nutlin-3a, we show that local p53 activation in TME comprising overt tumor-infiltrating leukocytes (TILeus) induces systemic antitumor immunity and tumor regression, but not in TME with scarce TILeus, such as B16 melanoma. Maneuvers that recruit leukocytes to TME, such as TLR3 ligand in B16 tumors, greatly enhanced nutlin-induced antitumor immunity and tumor control. Mechanistically, nutlin-3a-induced antitumor immunity was contingent on two nonredundant but immunologically synergistic p53-dependent processes: reversal of immunosuppression in the TME and induction of tumor immunogenic cell death, leading to activation and expansion of polyfunctional CD8 CTLs and tumor regression. Our study demonstrates that unlike conventional tumoricidal therapies, which rely on effective p53 targeting in each tumor cell and often associate with systemic toxicity, this immune-based strategy requires only limited local p53 activation to alter the immune landscape of TME and subsequently amplify immune response to systemic antitumor immunity. Hence, targeting the p53 pathway in TME can be exploited to reverse immunosuppression and augment therapeutic benefits beyond tumoricidal effects to harness tumor-specific, durable, and systemic antitumor immunity with minimal toxicity. Cancer Res; 77(9); 2292-305. ©2017 AACR.

Facilitating T Cell Infiltration in Tumor Microenvironment Overcomes Resistance to PD-L1 Blockade

Immune checkpoint blockade therapies fail to induce responses in the majority of cancer patients, so how to increase the objective response rate becomes an urgent challenge. Here, we demonstrate that sufficient T cell infiltration in tumor tissues is a prerequisite for response to PD-L1 blockade. Targeting tumors with tumor necrosis factor superfamily member LIGHT activates lymphotoxin β-receptor signaling, leading to the production of chemokines that recruit massive numbers of T cells. Furthermore, targeting non-T cell-inflamed tumor tissues by antibody-guided LIGHT creates a T cell-inflamed microenvironment and overcomes tumor resistance to checkpoint blockade. Our data indicate that targeting LIGHT might be a potent strategy to increase the responses to checkpoint blockades and other immunotherapies in non-T cell-inflamed tumors.

CpG-1826 immunotherapy potentiates chemotherapeutic and anti-tumor immune responses to metronomic cyclophosphamide in a preclinical glioma model

Cyclophosphamide administered on an intermittent metronomic schedule induces strong immune-dependent regression in several glioma models. Here we investigate whether this immunogenic chemotherapy can be potentiated by combination with the immune stimulatory TLR9 agonist CpG-1826. CpG-1826 treatment of GL261 gliomas implanted in immune competent mice induced tumor growth delay associated with increased tumor recruitment of macrophages and B cells. Anti-tumor responses varied between individuals, with CpG-1826 inducing robust tumor growth delay in ~50% of treated mice. Both high and low CpG-1826-responsive mice showed striking improvements when CpG-1826 was combined with cyclophosphamide treatment. Tumor-associated macrophages, B cells, dendritic cells, and cytotoxic T cells were increased, T regulatory cells were not induced, and long-term GL261 glioma regression with immune memory was achieved when CpG-1826 was combined with either single cyclophosphamide dosing (90 mg/kg) or metronomic cyclophosphamide treatment (two cycles at 45 mg/kg, spaced 12-days apart). B16F10 melanoma, a low immunogenic tumor model, also showed enhanced immune and anti-tumor responses to cyclophosphamide/CpG-1826 chemoimmunotherapy, but unlike GL261 tumors, did not regress. TLR9-based immunotherapy can thus be effectively combined with immunogenic cyclophosphamide treatment to enhance immune-based anti-tumor responses, even in poorly immunogenic cancer models.

Prognosis Relevance of Serum Cytokines in Pancreatic Cancer

The overall survival of patients with pancreatic ductal adenocarcinoma is extremely low. Although gemcitabine is the standard used chemotherapy for this disease, clinical outcomes do not reflect significant improvements, not even when combined with adjuvant treatments. There is an urgent need for prognosis markers to be found. The aim of this study was to analyze the potential value of serum cytokines to find a profile that can predict the clinical outcome in patients with pancreatic cancer and to establish a practical prognosis index that significantly predicts patients' outcomes. We have conducted an extensive analysis of serum prognosis biomarkers using an antibody array comprising 507 human cytokines. Overall survival was estimated using the Kaplan-Meier method. Univariate and multivariate Cox's proportional hazard models were used to analyze prognosis factors. To determine the extent that survival could be predicted based on this index, we used the leave-one-out cross-validation model. The multivariate model showed a better performance and it could represent a novel panel of serum cytokines that correlates to poor prognosis in pancreatic cancer. B7-1/CD80, EG-VEGF/PK1, IL-29, NRG1-beta1/HRG1-beta1, and PD-ECGF expressions portend a poor prognosis for patients with pancreatic cancer and these cytokines could represent novel therapeutic targets for this disease.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.

Mouse model for pre-clinical study of human cancer immunotherapy

This unit describes protocols for developing tumors in mice, including subcutaneous growth, pulmonary metastases of B16 melanoma, and spontaneous melanoma in B-Raf V600E/PTEN deletion transgenic mouse models. Two immunization methods to prevent B16 tumor growth are described using B16.GM-CSF and recombinant vaccinia virus. A therapeutic approach is also included that uses adoptive transfer of tumor antigen-specific T cells. Methods including CTL induction, isolation, testing, and genetic modification of mouse T cells for adoptive transfer by using retrovirus-expressing genes of interest are provided. Additional sections, including growing B16 melanoma, enumerating pulmonary metastases, tumor imaging technique, and use of recombinant viruses for vaccination, are discussed together with safety concerns.

Immunogenicity of murine solid tumor models as a defining feature of in vivo behavior and response to immunotherapy

Immune profiling has been widely used to probe mechanisms of immune escape in cancer and identify novel targets for therapy. Two emerging uses of immune signatures are to identify likely responders to immunotherapy regimens among individuals with cancer and to understand the variable responses seen among subjects with cancer in immunotherapy trials. Here, the immune profiles of 6 murine solid tumor models (CT26, 4T1, MAD109, RENCA, LLC, and B16) were correlated to tumor regression and survival in response to 2 immunotherapy regimens. Comprehensive profiles for each model were generated using quantitative reverse transcriptase polymerase chain reaction, immunohistochemistry, and flow cytometry techniques, as well as functional studies of suppressor cell populations (regulatory T cells and myeloid-derived suppressor cells), to analyze intratumoral and draining lymphoid tissues. Tumors were stratified as highly or poorly immunogenic, with highly immunogenic tumors showing a significantly greater presence of T-cell costimulatory molecules and immune suppression in the tumor microenvironment. An absence of tumor-infiltrating cytotoxic T lymphocytes and mature dendritic cells was seen across all models. Delayed tumor growth and increased survival with suppressor cell inhibition and tumor-targeted chemokine+/-dendritic cells vaccine immunotherapy were associated with high tumor immunogenicity in these models. Tumor MHC class I expression correlated with the overall tumor immunogenicity level and was a singular marker to predict immunotherapy response with these regimens. By using experimental tumor models as surrogates for human cancers, these studies demonstrate how select features of an immune profile may be utilized to identify patients most likely to respond to immunotherapy regimens.

CD137 stimulation and p38 MAPK inhibition improve reactivity in an in vitro model of glioblastoma immunotherapy

Dendritic cell vaccination has become an interesting option for cancer immunotherapy. Tumor-lysate-pulsed dendritic cells (DC) can prime naïve T cells and induce the regression of established tumors including gliomas as shown in various animal models. Despite hopeful results even in clinical studies, the outcome for many patients is still unsatisfying. In the present study, we tested the combination of tumor-lysate-pulsed dendritic cells (TPDC) with a monoclonal antibody against CD137, a monoclonal antibody against CD25 (daclizumab) and a specific p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (SB203580) for improving immunostimulation in an in vitro model of immunotherapy for human gliomas. We observed a higher secretion of interferon gamma by TPDC-primed peripheral blood mononuclear cells (PBMC) that were incubated with an antibody against CD137 or the p38 MAPK inhibitor. In addition, we observed higher specific lysis of tumor cells after incubation of PBMC with the p38 MAPK inhibitor or the anti-CD137 antibody. In contrast, incubation of TPDC-primed PBMC with the anti-CD25 antibody did enhance neither interferon gamma secretion nor cellular cytotoxicity. Cell depletion experiments demonstrated that the immune reaction induced by TPDC is strongly dependent on CD4-positive and CD8-positive cells. Incubation of DC during maturation and antigen loading with the anti-CD137 antibody did not enhance cytotoxicity and interferon gamma secretion in comparison with application of the anti-CD137 antibody during priming. In conclusion, our data suggest that p38 MAPK inhibition and anti-CD137 antibodies can enhance the immune response against glioblastoma cells.

The Tumor-Selective Cytotoxic Agent β-Lapachone is a Potent Inhibitor of IDO1

β-lapachone is a naturally occurring 1,2-naphthoquinone-based compound that has been advanced into clinical trials based on its tumor-selective cytotoxic properties. Previously, we focused on the related 1,4-naphthoquinone pharmacophore as a basic core structure for developing a series of potent indoleamine 2,3-dioxygenase 1 (IDO1) enzyme inhibitors. In this study, we identified IDO1 inhibitory activity as a previously unrecognized attribute of the clinical candidate β-lapachone. Enzyme kinetics-based analysis of β-lapachone indicated an uncompetitive mode of inhibition, while computational modeling predicted binding within the IDO1 active site consistent with other naphthoquinone derivatives. Inhibition of IDO1 has previously been shown to breach the pathogenic tolerization that constrains the immune system from being able to mount an effective anti-tumor response. Thus, the finding that β-lapachone has IDO1 inhibitory activity adds a new dimension to its potential utility as an anti-cancer agent distinct from its cytotoxic properties, and suggests that a synergistic benefit can be achieved from its combined cytotoxic and immunologic effects.

Recent developments in oncolytic adenovirus-based immunotherapeutic agents for use against metastatic cancers

Recurrent or metastatic cancer in most cases remains an incurable disease, and thus alternative treatment strategies, such as oncolytic virotherapy, are of great interest for clinical application. Oncolytic adenoviruses (Ads) have many advantages as virotherapeutic agents and have been safely employed in the clinics. However, the efficacy of oncolytic Ads is insufficient to eradicate tumors and current clinical applications are restricted to local administration against primary tumors because of immunological obstacles and poor tumor-cell targeting. Thus, alternative viable approaches are needed to establish therapies based on oncolytic Ad that will eliminate both primary and metastatic cancers. To this end, rational design of oncolytic Ads that express immunostimulatory genes has been employed. Even when restricted to local viral delivery, these oncolytic Ad-based immunotherapeutics have been shown to exert systemic antitumor immunity and result in eradication of both primary and metastatic cancers. Moreover, oncolytic Ad-based immunotherapeutics in combination with either dendritic cell-based vaccine or radiotherapy further strengthen the systemic tumor-specific immunity, resulting in complete suppression of both local and distant tumor metastatic growth. This review will focus on the most recent updates in strategies to develop potent oncolytic Ad-based immunotherapeutics for use in cancer gene therapy.

A therapeutic vaccine using Salmonella-modified tumor cells combined with interleukin-2 induces enhanced antitumor immunity in B-cell lymphoma

Therapeutic vaccination holds potential as complementary treatment for non-Hodgkin's lymphoma (NHL). B-NHL cells are antigen-presenting cells, but they cannot elicit proper antitumor responses because they lack expression of co-stimulatory molecules. Here, we report a novel approach to design improved whole tumor cell vaccines for B-NHL. We demonstrated that Salmonella infection significantly up-regulates CD80, CD86, CD40 and MHC II expression in lymphoma cells, and that therapeutic vaccination with infected and then irradiated lymphoma cells combined with IL-2 elicits strong anti-tumor specific immunity and extended survival in lymphoma-bearing mice. This may represent the basis of an effective immunotherapy against B-NHL that could be easily translated into the clinics.

Chemokines, costimulatory molecules and fusion proteins for the immunotherapy of solid tumors

In this article, the role of chemokines and costimulatory molecules in the immunotherapy of experimental murine solid tumors and immunotherapy used in ongoing clinical trials are presented. Chemokine networks regulate physiologic cell migration that may be disrupted to inhibit antitumor immune responses or co-opted to promote tumor growth and metastasis in cancer. Recent studies highlight the potential use of chemokines in cancer immunotherapy to improve innate and adaptive cell interactions and to recruit immune effector cells into the tumor microenvironment. Another critical component of antitumor immune responses is antigen priming and activation of effector cells. Reciprocal expression and binding of costimulatory molecules and their ligands by antigen-presenting cells and naive lymphocytes ensures robust expansion, activity and survival of tumor-specific effector cells in vivo. Immunotherapy approaches using agonist antibodies or fusion proteins of immunomodulatory molecules significantly inhibit tumor growth and boost cell-mediated immunity. To localize immune stimulation to the tumor site, a series of fusion proteins consisting of a tumor-targeting monoclonal antibody directed against tumor necrosis and chemokines or costimulatory molecules were generated and tested in tumor-bearing mice. While several of these reagents were initially shown to have therapeutic value, combination therapies with methods to delete suppressor cells had the greatest effect on tumor growth. In conclusion, a key conclusion that has emerged from these studies is that successful immunotherapy will require both advanced methods of immunostimulation and the removal of immunosuppression in the host.

Exploiting the mutanome for tumor vaccination

Multiple genetic events and subsequent clonal evolution drive carcinogenesis, making disease elimination with single-targeted drugs difficult. The multiplicity of gene mutations derived from clonal heterogeneity therefore represents an ideal setting for multiepitope tumor vaccination. Here, we used next generation sequencing exome resequencing to identify 962 nonsynonymous somatic point mutations in B16F10 murine melanoma cells, with 563 of those mutations in expressed genes. Potential driver mutations occurred in classical tumor suppressor genes and genes involved in proto-oncogenic signaling pathways that control cell proliferation, adhesion, migration, and apoptosis. Aim1 and Trrap mutations known to be altered in human melanoma were included among those found. The immunogenicity and specificity of 50 validated mutations was determined by immunizing mice with long peptides encoding the mutated epitopes. One-third of these peptides were found to be immunogenic, with 60% in this group eliciting immune responses directed preferentially against the mutated sequence as compared with the wild-type sequence. In tumor transplant models, peptide immunization conferred in vivo tumor control in protective and therapeutic settings, thereby qualifying mutated epitopes that include single amino acid substitutions as effective vaccines. Together, our findings provide a comprehensive picture of the mutanome of B16F10 melanoma which is used widely in immunotherapy studies. In addition, they offer insight into the extent of the immunogenicity of nonsynonymous base substitution mutations. Lastly, they argue that the use of deep sequencing to systematically analyze immunogenicity mutations may pave the way for individualized immunotherapy of cancer patients.

A mathematical model of tumor-immune interactions

A mathematical model of the interactions between a growing tumor and the immune system is presented. The equations and parameters of the model are based on experimental and clinical results from published studies. The model includes the primary cell populations involved in effector T-cell mediated tumor killing: regulatory T cells, helper T cells, and dendritic cells. A key feature is the inclusion of multiple mechanisms of immunosuppression through the main cytokines and growth factors mediating the interactions between the cell populations. Decreased access of effector cells to the tumor interior with increasing tumor size is accounted for. The model is applied to tumors with different growth rates and antigenicities to gauge the relative importance of various immunosuppressive mechanisms. The most important factors leading to tumor escape are TGF-β-induced immunosuppression, conversion of helper T cells into regulatory T cells, and the limitation of immune cell access to the full tumor at large tumor sizes. The results suggest that for a given tumor growth rate, there is an optimal antigenicity maximizing the response of the immune system. Further increases in antigenicity result in increased immunosuppression, and therefore a decrease in tumor killing rate. This result may have implications for immunotherapies which modulate the effective antigenicity. Simulation of dendritic cell therapy with the model suggests that for some tumors, there is an optimal dose of transfused dendritic cells.

Establishment of a CBRH7919 cell line expressing rat IL-2 and B7-1

AIM: To establish a CBRH7919 cell line CBRH7919 expressing rat IL-2 and B7-1 genes and to examine their ability to express the IL-2 and B7-1 genes in vitro.

METHODS: The IL-2 and B7-1 genes were amplified by RT-PCR and subcloned into retroviral vectors pBaBe-puro and pMSCV-neo, respectively, to obtain the recombinant retroviral vectors pBaBe-puro-IL-2 and pMSCV-neo-B7-1. The recombinant plasmids were then transfected into the 293FT packaging cells. The obtained infectious viruses were used to infect the CBRH7919 cell line, and puro/G418-resistant clones were acquired after puro/G418 selection. The expression of IL-2 and B7-1 was detected using Q-PCR, Western blot and ELISA.

RESULTS: The rat IL-2 and B7-1 genes were successfully amplified by RT-PCR, and the recombinant plasmids pBaBe-puro-IL-2 and pMSCV-neo-B7-1 were successfully constructed and verified by direct sequencing. A CBRH7919 cell line (CBRH7919/IL-2/B7-1) expressing rat IL-2 and B7-1 was established. Q-PCR analysis showed that the expression levels of IL-2 and B7-1 mRNAs in CBRH-7919/IL-2/B7-1 cells were 4.15 and 17.04 times higher than those in CBRH-7919-pmscv-neo cells. Western blot analysis showed that the expression level of B7-1 protein in CBRH-7919/IL-2/B7-1 cells was 3 times more than that in unmodified cells, while ELISA showed that expression level of IL-2 was 190 times more than that in unmodified cells.

CONCLUSION: A CBRH7919 cell line stably and effectively expressing rat IL-2 and B7-1 genes was obtained and provides a good basis for further research of immuno-gene therapy of liver cancer.

CpG-conjugated apoptotic tumor cells elicit potent tumor-specific immunity

The primary goal of cancer immunotherapy is to elicit an immune response capable of eradicating established tumors and preventing tumor metastasis. One strategy to achieve this goal utilizes whole killed tumor cells as the primary immunogen. Killed tumor cells provide a comprehensive source of tumor-associated antigens (TAAs), thereby eliminating the need to identify individual antigens. Unfortunately, killed tumor cells tend to be poorly immunogenic. To overcome this limitation, we covalently conjugated immunostimulatory CpG oligodeoxynucleotides (ODN) to apoptotic tumor cells and examined their ability to induce TAA-specific immune responses. Results indicate that CpG conjugation enhances the uptake of cell-based vaccines by dendritic cells (DCs), up-regulates co-stimulatory molecule expression, and promotes the production of immunostimulatory cytokines. Vaccination with CpG-conjugated tumor cells triggers the expansion of tumor-specific cytotoxic T lymphocytes (CTL) that reduce the growth of established tumors and prevents their metastatic spread. Thus, conjugating CpG ODN to cell-based tumor vaccines is an important step toward improving cancer immunotherapy.

AAV2-mediated in vivo immune gene therapy of solid tumours

Background

Many strategies have been adopted to unleash the potential of gene therapy for cancer, involving a wide range of therapeutic genes delivered by various methods. Immune therapy has become one of the major strategies adopted for cancer gene therapy and seeks to stimulate the immune system to target tumour antigens. In this study, the feasibility of AAV2 mediated immunotherapy of growing tumours was examined, in isolation and combined with anti-angiogenic therapy.

Methods

Immune-competent Balb/C or C57 mice bearing subcutaneous JBS fibrosarcoma or Lewis Lung Carcinoma (LLC) tumour xenografts respectively were treated by intra-tumoural administration of AAV2 vector encoding the immune up-regulating cytokine granulocyte macrophage-colony stimulating factor (GM-CSF) and the co-stimulatory molecule B7-1 to subcutaneous tumours, either alone or in combination with intra-muscular (IM) delivery of AAV2 vector encoding Nk4 14 days prior to tumour induction. Tumour growth and survival was monitored for all animals. Cured animals were re-challenged with tumourigenic doses of the original tumour type. In vivo cytotoxicity assays were used to investigate establishment of cell-mediated responses in treated animals.

Results

AAV2-mediated GM-CSF, B7-1 treatment resulted in a significant reduction in tumour growth and an increase in survival in both tumour models. Cured animals were resistant to re-challenge, and induction of T cell mediated anti-tumour responses were demonstrated. Adoptive transfer of splenocytes to naïve animals prevented tumour establishment. Systemic production of Nk4 induced by intra-muscular (IM) delivery of Nk4 significantly reduced subcutaneous tumour growth. However, combination of Nk4 treatment with GM-CSF, B7-1 therapy reduced the efficacy of the immune therapy.

Conclusions

Overall, this study demonstrates the potential for in vivo AAV2 mediated immune gene therapy, and provides data on the inter-relationship between tumour vasculature and immune cell recruitment.

Structural immunology of costimualtory and coinhibitory molecules

The T cell costimulatory pathways are central to regulating immune responses, and targeting these pathways represents one of the most promising approaches for achieving immunotherapy. The molecular structures of costimulation revealed invaluable mechanistic insights underlying costimulatory receptor/ligand specificity, affinity, oligomeric state, and valency, which provided the bases for better manipulation of these signaling pathways. The incredible growth of this field led to identification of new members and unexpected interactions, revealing a complicated regulatory network of immune responses. The advances in structural biology of costimulation will promise unprecedented opportunities for furthering our understanding and therapeutic application of T cell costimulatory pathways.

Enhancement of effector CD8+ T-cell function by tumour-associated B7-H3 and modulation of its counter-receptor triggering receptor expressed on myeloid cell-like transcript 2 at tumour sites

SUMMARY

B7-H3 is a B7-family co-stimulatory molecule and is broadly expressed on various tissues and immune cells. Transduction of B7-H3 into some tumours enhances anti-tumour responses. We have recently found that a triggering receptor expressed on myeloid cell-like transcript 2 (TLT-2) is a receptor for B7-H3. Here, we examined the roles of tumour-associated B7-H3 and the involvement of TLT-2 in anti-tumour immunity. Ovalbumin (OVA)(257-264)-specific OT-I CD8(+) T cells exhibited higher cytotoxicity against B7-H3-transduced OVA-expressing tumour cells (B7-H3/E.G7) in vitro and selectively eliminated B7-H3/E.G7 cells in vivo. The presence of B7-H3 on target cells efficiently augmented CD8(+) T-cell-mediated cytotoxicity against alloantigen or OVA, whereas the presence of B7-H3 in the priming phase did not affect the induced cytotoxicity. B7-H3 transduction into five tumour cell lines efficiently reduced their tumorigenicity and regressed growth. Treatment with either anti-B7-H3 or anti-TLT-2 monoclonal antibody accelerated growth of a tumour that expressed endogenous B7-H3, suggesting a co-stimulatory role of the B7-H3-TLT-2 pathway. The TLT-2 was preferentially expressed on CD8(+) T cells in regional lymph nodes, but was down-regulated in tumour-infiltrating CD8(+) T cells. Transduction of TLT-2 into OT-I CD8(+) T cells enhanced antigen-specific cytotoxicity against both parental and B7-H3-transduced tumour cells. Our results suggest that tumour-associated B7-H3 directly augments CD8(+) T-cell effector function, possibly by ligation of TLT-2 on tumour-infiltrating CD8(+) T cells at the local tumour site.

Immunobiology of cancer therapies targeting CD137 and B7-H1/PD-1 cosignal pathways

Cancer immunotherapy is finally entering a new era with manipulation of cosignaling pathways as a therapeutic approach, for which the principle was proved nearly two decades ago. In addition to CTLA-4, CD137 and B7-H1/PD-1 pathways are two new targets in the stage. CD137 pathway is costimulatory and its agonistic antibody delivers potent signal to drive T cell growth and activation. On the other hand, blockade of B7-H1/PD-1 pathway with antagonistic antibody has shown to protect ongoing T cell responses from impairment by immune evasion mechanism in cancer microenvironment. With these tools in hand, a mechanism-based design of combined immunotherapy with high efficacy is becoming a reality.

Immunotherapy for neuroblastoma: turning promise into reality

Neuroblastoma is one of the commonest and most aggressive paediatric malignancies. The majority of children present with metastatic disease for which long-term survival remains poor despite intensive multi-modal therapies. Toxicity from current treatment regimes is already significant, and there is little room to further intensify therapy. Alternative treatment strategies are therefore needed in order to improve survival. Immunotherapy is an attractive therapeutic option for these children as it potentially offers a much more specific and less toxic treatment than conventional therapies. This review discusses the different immunotherapy strategies that may be useful in neuroblastoma, their advantages and disadvantages and the challenges that need to be overcome to successfully use them clinically.

Promises and Limitations of Murine Models in the Development of Anticancer T-Cell Vaccines

Murine models have been instrumental in defining the basic mechanisms of antitumor immunity. Most of these mechanisms have since been shown to operate in humans as well. Based on these similarities, active vaccination strategies aimed at eliciting antitumor T-cell responses have been elaborated and successfully implemented in various mouse models. However, the results of human antitumor vaccination trials have been rather disappointing thus far. This review summarizes the different experimental approaches used in mice to induce antitumor T-cell responses and identifies some critical parameters that should be considered when evaluating results from murine models.

Inhibition of TGFbeta1 makes nonimmunogenic tumor cells effective for therapeutic vaccination

We have previously demonstrated that transplanted cells from the SW1 clone of the K1735 melanoma and the Ag104 sarcoma grow progressively in syngeneic C3H mice even after transfection to engage CD137, a procedure that increases the immunogenicity of many other tumors. We now show that SW1 and Ag104 cells produce high levels of transforming growth factor (TGF) beta1, and that they can induce an antitumor response if they are transfected with a nonreplicating lentivirus vector to "silence" the TGFbeta1 gene via short hairpin RNA. Importantly, vaccination with SW1 or Ag104 cells, which do not make TGFbeta1, is therapeutically efficacious against small wild type tumors, including SW1 micrometastases in the lung. An analogous approach may be applicable to human tumors that produce TGFbeta1 or other immunosuppressive molecules to improve the efficacy of tumor cell-based therapeutic vaccines.

Checkpoint blockade in cancer immunotherapy

The progression of a productive immune response requires that a number of immunological checkpoints be passed. Passage may require the presence of excitatory costimulatory signals or the avoidance of negative or coinhibitory signals, which act to dampen or terminate immune activity. The immunoglobulin superfamily occupies a central importance in this coordination of immune responses, and the CD28/cytotoxic T-lymphocyte antigen-4 (CTLA-4):B7.1/B7.2 receptor/ligand grouping represents the archetypal example of these immune regulators. In part the role of these checkpoints is to guard against the possibility of unwanted and harmful self-directed activities. While this is a necessary function, aiding in the prevention of autoimmunity, it may act as a barrier to successful immunotherapies aimed at targeting malignant self-cells that largely display the same array of surface molecules as the cells from which they derive. Therapies aimed at overcoming these mechanisms of peripheral tolerance, in particular by blocking the inhibitory checkpoints, offer the potential to generate antitumor activity, either as monotherapies or in synergism with other therapies that directly or indirectly enhance presentation of tumor epitopes to the immune system. Such immunological molecular adjuvants are showing promise in early clinical trials. This review focuses on the results of the archetypal example of checkpoint blockade, anti-CTLA-4, in preclinical tumor models and clinical trials, while also highlighting other possible targets for immunological checkpoint blockade.