Molecular mechanisms of T cell co-stimulation and co-inhibition

Clinical significance of tumor-infiltrating immune cells focusing on BTLA and Cbl-b in patients with gallbladder cancer

The host immune system plays a significant role in tumor control, although most cancers escape immune surveillance through a variety of mechanisms. The aim of the present study was to evaluate the clinicopathological significance of a novel co‐inhibitory receptor, B and T lymphocyte attenuator (BTLA), the anergy cell marker Casitas–B‐lineage lymphoma protein‐b (Cbl‐b), and clinical implications of tumor‐infiltrating immune cells in gallbladder cancer (GBC) tissues. We investigated 211 cases of GBC, 21 cases of chronic cholecystitis (CC), and 11 cases of xanthogranulomatous cholecystitis (XGC) using immunohistochemistry to detect tissue‐infiltrating immune cells and their expression of BTLA and Cbl‐b, and carried out correlation and survival analyses. The density of infiltrating T cells was significantly higher in CC and XGC than in GBC. The density ratio of BTLA⁺ cells to CD8⁺ T cells (BTLA/CD8) and that of Cbl‐b⁺ cells to CD8⁺T cells (Cbl‐b/CD8) were significantly higher in GBC than in CC and XGC. The FOXP3/CD4, BTLA/CD8, and Cbl‐b/CD8 ratios were significantly correlated with each other, and also with malignant phenotypes. Survival analyses revealed that a lower density of tumor‐infiltrating CD8⁺ cells, and higher Foxp3/CD4, BTLA/CD8, and Cbl‐b/CD8 ratios were significantly associated with shorter overall survival and disease‐free survival in GBC patients. Multivariate analyses showed that M factor, perineural invasion, BTLA/CD8, and Cbl‐b/CD8 were closely associated with shorter overall survival. These findings suggest that higher ratios of BTLA/CD8 and Cbl‐b/CD8 are independent indicators of unfavorable outcome in GBC patients, and that upregulation of BTLA in cancer tissues is involved in inhibition of antitumor immunity.

Roles of PD-1, Tim-3 and CTLA-4 in immunoregulation in regulatory T cells among patients with sepsis

OBJECTIVE

This study aims to elucidate the roles of PD-1, Tim-3 and CTLA-4 in sepsis.

METHODS

Sepsis patients (n = 182) were selected as sepsis group and divided into three subgroups: mild sepsis group, severe sepsis group and septic shock group; 185 healthy volunteers were enrolled as control group. Flow cytometry and blood routine examination were performed for T lymphocytes and surface co-stimulatory molecules expressions. Pearson correlation test was applied for the correlation of co-stimulatory molecules expressions on T lymphocytes with critical illness in sepsis. Logistic regression analysis was conducted for risk factors in sepsis.

RESULTS

Heart rate and WBC in subgroups were higher than control group (P < 0.05). The differences in APACHE II, SAP II and SOFA score among subgroups were statistically significant (P < 0.05). Compared with control group, lymphocyte ratio and percentage of CD4(+) T cells reduced in subgroups (P < 0.05). The differences in expression levels of CD4(+)PD-1(+), CD8(+)PD-1(+), and CD8(+)CTLA-4(+) showed statistical significances (P < 0.05). Apparently, expression levels of CD4(+)TIM-3(+), CD8(+)TIM-3(+), CD4(+)PD-1(+), CD8(+)PD-1(+), and CD4(+)CTLA-4(+) were positively correlated with APACHE II score (all P < 0.05). Logistic regression analysis showed that heart rate and expression level of CD4(+)PD-1(+) might be risk factors while the percentage of CD4(+) T cells might be a protective factor for sepsis (P < 0.05).

CONCLUSION

PD-1 aggravates immune responses consistent with promotion of T cell exhaustion in sepsis. Expression level of CD4(+)PD-1(+) and heart rate are potential risk factors while percentage of CD4(+) T cells is a possible protective factor for sepsis.

Comparing the Primary and Recall Immune Response Induced by a New EV71 Vaccine Using Systems Biology Approaches

Three inactivated EV71 whole-virus vaccines have completed Phase III clinical trials in mainland China, with high efficacy, satisfactory safety, and sustained immunogenicity. However, the molecular mechanisms how this new vaccine elicit potent immune response remain poorly understood. To characterize the primary and recall responses to EV71 vaccines, PBMC from 19 recipients before and after vaccination with EV71 vaccine are collected and their gene expression signatures after stimulation with EV71 antigen were compared. The results showed that primary and recall response to EV71 antigen have both activated an IRF7 regulating type I interferon and antiviral immune response network. However, up-regulated genes involved in T cell activation regulated by IRF1, inflammatory response, B-cell activation and humoral immune response were only observed in recall response. The specific secretion of IL-10 in primary response and IL-2,IP-10,CCL14a, CCL21 in recall response was consistent with the activation of immune response process found in genes. Furthermore, the expression of MX1 and secretion of IP-10 in recall response were strongly correlated with NTAb level at 180d after vaccination (r = 0.81 and 0.99). In summary, inflammatory response, adaptive immune response and a stronger antiviral response were indentified in recall response.

Structural Design of Engineered Costimulation Determines Tumor Rejection Kinetics and Persistence of CAR T Cells

T cell engineering is a powerful means to rapidly generate anti-tumor T cells. The costimulatory properties of second-generation chimeric antigen receptors (CARs) determine the overall potency of adoptively transferred T cells. Using an in vivo "stress test" to challenge CD19-targeted T cells, we studied the functionality and persistence imparted by seven different CAR structures providing CD28 and/or 4-1BB costimulation. One configuration, which uses two signaling domains (CD28 and CD3ζ) and the 4-1BB ligand, provided the highest therapeutic efficacy, showing balanced tumoricidal function and increased T cell persistence accompanied by an elevated CD8/CD4 ratio and decreased exhaustion. Remarkably, induction of the IRF7/IFNβ pathway was required for optimal anti-tumor activity. Thus, 1928z-41BBL T cells possess strikingly potent intrinsic and immunomodulatory qualities.

Regulatory T cells and minimal change nephropathy: in the midst of a complex network

Minimal change nephrosis (MCN) is an important cause of morbidity in children. In spite of successful therapies having been developed in the last three decades, most aspects related to pathogenesis still remain poorly defined. Evolution in basic immunology and results deriving from animal models of the disease suggest a complex interaction of factors and cells starting from activation of innate immunity and continuing with antigen presentation. Oxidants, CD80 and CD40/CD40L have probably a relevant role at the start. Studies in animal models and in human beings also suggest the possibility that the same molecules (i.e. CD80, CD40) are expressed by podocytes under inflammatory stimuli, representing a direct potential mechanism for proteinuria. B and T cells could play a relevant role this contest. Implication of B cells is suggested indirectly by studies utilizing anti-CD20 monoclonal antibodies as the main therapy. The role of regulatory T cells (Tregs ) is supported mainly by results in animal models of nephrotic syndrome (i.e. adriamycin, puromycin, lipopolysaccharide), showing a protective effect of direct Treg infusion or stimulation by interleukin 2 (IL-2). Limited studies have also shown reduced amounts of circulating Tregs in patients with active MCN cells. The route from bench to bedside would be reduced if results from animal models were confirmed in human pathology. The expansion of Tregs with recombinant IL-2 and new anti-CD20 monoclonal antibodies is the beginning. Blocking antigen-presenting cells with cytotoxic T lymphocyte antigen (CTLA-4)-Ig fusion molecules inhibiting CD80 and/or with blockers of CD40-CD40 ligand interaction represent potential new approaches. The hope is that evolution in therapies of MCN could fill a gap lasting 30 years.

Redirection of CD4+ and CD8+ T lymphocytes via an anti-CD3 × anti-CD19 bi-specific antibody combined with cytosine arabinoside and the efficient lysis of patient-derived B-ALL cells

Background

B-acute lymphoblastic leukemia (B-ALL) is derived from B cell progenitors. Recently, the development of appropriate combinations of chemotherapy and immunotherapy represents a promising approach for eliminating cancer. We previously constructed an anti-CD3 × anti-CD19 bi-specific antibody in a diabody configuration and its disulfide-stabilized format (ds-diabody). The combination of the diabody or ds-diabody and Ara-C was highly effective in enhancing the cytotoxicity of T cells against the CD19+ human leukemia cell-line, Nalm-6, both in vitro and in vivo. This study verified whether B-ALL patient-derived cells were sensitive to the diabody or ds-diabody and low-dosage Ara-C combination.

Methods

This study aimed to detect the B7 family members B7.1 (CD80) and B7.2 (CD86) that were expressed in B-ALL patient-derived cells pre-treated by Ara-C (0.25 μM) and to determine the targeted killing ability of T cell subtypes induced by the diabody or ds-diabody combination with Ara-C both in vitro and in vivo. We also determined the levels of the cytokines that were released by activated CD4+ or CD8+ T cells during therapy.

Result

Low-dose Ara-C enhanced CD80 and CD86 expression in nearly 50 % of specimens of B-ALL patient-derived cells. A combination of diabody or ds-diabody and Ara-C enhanced T cell against B-ALL cells in vitro and in vivo. Both CD8+ and CD4+ T cells were potently activated. Expression of CD25 and CD69 was augmented equally by CD4+ or CD8+ T cells. However, CD8+ T cells made the major contribution by redirecting target cell lysis in a granzyme B and perforin-dependent mechanism. CD4+ T cells played an important immunomodulatory role by secreting IL2. Consequently, IL3, IL6, TNFα, and IFNγ were also released by CD4+ or CD8+ T cells following diabody-mediated T cell activation.

Conclusion

T cell therapy induced by diabody or ds-diabody combined with low dose of Ara-C was effective against cancer cell-lines and in clinical trials. In vivo, the ds-diabody was more efficient than its parent diabody due to its enhanced stability.

Integrated molecular analysis of adult T cell leukemia/lymphoma

Adult T cell leukemia/lymphoma (ATL) is a peripheral T cell neoplasm of largely unknown genetic basis, associated with human T cell leukemia virus type-1 (HTLV-1) infection. Here we describe an integrated molecular study in which we performed whole-genome, exome, transcriptome and targeted resequencing, as well as array-based copy number and methylation analyses, in a total of 426 ATL cases. The identified alterations overlap significantly with the HTLV-1 Tax interactome and are highly enriched for T cell receptor-NF-κB signaling, T cell trafficking and other T cell-related pathways as well as immunosurveillance. Other notable features include a predominance of activating mutations (in PLCG1, PRKCB, CARD11, VAV1, IRF4, FYN, CCR4 and CCR7) and gene fusions (CTLA4-CD28 and ICOS-CD28). We also discovered frequent intragenic deletions involving IKZF2, CARD11 and TP73 and mutations in GATA3, HNRNPA2B1, GPR183, CSNK2A1, CSNK2B and CSNK1A1. Our findings not only provide unique insights into key molecules in T cell signaling but will also guide the development of new diagnostics and therapeutics in this intractable tumor.

Novel insights into the pathophysiology and treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive, treatment-resistant tumor, which continues to increase in frequency throughout the world because the causative agent, asbestos, has high economic importance, particularly in developing countries. Patients typically present with breathlessness and chest pain with pleural effusions. Median survival is around 12 months from diagnosis. Palliative chemotherapy is beneficial for mesothelioma patients with high performance status. The role of aggressive surgery remains controversial. This review will outline some of the recent advances in the development of novel therapies for malignant pleural mesothelioma, with a focus on immunological approaches.

Immune outcomes in the liver: Is CD8 T cell fate determined by the environment?

The liver is known for its tolerogenic properties. This unique characteristic is associated with persistent infection of the liver by the hepatitis B and C viruses. Improper activation of cellular adaptive immune responses within the liver and immune exhaustion over time both contribute to ineffective cytotoxic T cell responses to liver-expressed antigens in animal models, and likely play a role in incomplete clearance of chronic hepatitis virus infections in humans. However, under some conditions, functional immune responses can be elicited against hepatic antigens, resulting in control of hepatotropic infections. In order to develop improved therapeutics in immune-mediated chronic liver diseases, including viral hepatitis, it is essential to understand how intrahepatic immunity is regulated. This review focuses on CD8 T cell immunity directed towards foreign antigens expressed in the liver, and explores how the liver environment dictates the outcome of intrahepatic CD8 T cell responses. Potential strategies to rescue unresponsive CD8 T cells in the liver are also discussed.

Potentiality of immunotherapy against hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the predominant form of primary liver cancer, is the fifth most common cancer worldwide and the second leading cause of cancer-related death. Despite the high incidence, treatment options remain limited for advanced HCC, and as a result prognosis continues to be poor. Current therapeutic options, surgery, chemotherapy and radiotherapy, have only modest efficacy. New treatment modalities to prolong survival and to minimize the risk of adverse response are desperately needed for patients with advanced HCC. Tumor immunotherapy is a promising, novel treatment strategy that may lead to improvements in both treatment-associated toxicity and outcome. The strategies have developed in part through genomic studies that have yielded candidate target molecules and in part through basic biology studies that have defined the pathways and cell types regulating immune response. Here, we summarize the various types of HCC immunotherapy and argue that the newfound field of HCC immunotherapy might provide critical advantages in the effort to improve prognosis of patients with advanced HCC. Already several immunotherapies, such as tumor-associated antigen therapy, immune checkpoint inhibitors and cell transfer immunotherapy, have demonstrated safety and feasibility in HCC patients. Unfortunately, immunotherapy currently has low efficacy in advanced stage HCC patients; overcoming this challenge will place immunotherapy at the forefront of HCC treatment, possibly in the near future.

Biomarkers for Sepsis: What Is and What Might Be?

Every year numerous individuals develop the morbid condition of sepsis. Therefore, novel biomarkers that might better inform clinicians treating such patients are sorely needed. Difficulty in identifying such markers is in part due to the complex heterogeneity of sepsis, resulting from the broad and vague definition of this state/condition based on numerous possible clinical signs and symptoms as well as an incomplete understanding of the underlying pathobiology of this complex condition. This review considers some of the attempts that have been made so far, looking at both the pro- and anti-inflammatory response to sepsis, as well as genomic analysis, as sources of potential biomarkers. Irrespective, for functional biomarker(s) of sepsis to successfully translate from the laboratory to a clinical setting, the biomarker must be target specific and sensitive as well as easy to implement/interpret, and be cost effective, such that they can be utilized routinely in patient diagnosis and treatment.

Transient Loss of Protection Afforded by a Live Attenuated Non-typhoidal Salmonella Vaccine in Mice Co-infected with Malaria

In immunocompetent individuals, non-typhoidal Salmonella serovars (NTS) are associated with gastroenteritis, however, there is currently an epidemic of NTS bloodstream infections in sub-Saharan Africa. Plasmodium falciparum malaria is an important risk factor for invasive NTS bloodstream in African children. Here we investigated whether a live, attenuated Salmonella vaccine could be protective in mice, in the setting of concurrent malaria. Surprisingly, mice acutely infected with the nonlethal malaria parasite Plasmodium yoelii 17XNL exhibited a profound loss of protective immunity to NTS, but vaccine-mediated protection was restored after resolution of malaria. Absence of protective immunity during acute malaria correlated with maintenance of antibodies to NTS, but a marked reduction in effector capability of Salmonella-specific CD4 and CD8 T cells. Further, increased expression of the inhibitory molecule PD1 was identified on memory CD4 T cells induced by vaccination. Blockade of IL-10 restored protection against S. Typhimurium, without restoring CD4 T cell effector function. Simultaneous blockade of CTLA-4, LAG3, and PDL1 restored IFN-γ production by vaccine-induced memory CD4 T cells but was not sufficient to restore protection. Together, these data demonstrate that malaria parasite infection induces a temporary loss of an established adaptive immune response via multiple mechanisms, and suggest that in the setting of acute malaria, protection against NTS mediated by live vaccines may be interrupted.

In children, malaria is a predisposing factor for invasive bacterial infections with non-typhoidal Salmonella (NTS) serovars, a frequent cause of morbidity and mortality in sub-Saharan Africa. Since development of vaccines against NTS has been proposed as a strategy to protect African children against disseminated NTS infection, we interrogated the effect of malaria on vaccine-induced memory responses to NTS. Our results from a mouse infection model show that infection with malaria parasites temporarily suspends protective immunity conferred by a live, attenuated vaccine and suppresses adaptive immune responses to NTS that are mediated by T cells. These results suggest that in the setting of acute malaria, live attenuated NTS vaccines may lose their effectiveness.

From DNA Damage to Nucleic Acid Sensing: A Strategy to Enhance Radiation Therapy

Local irradiation (IR) is widely used in the treatment of primary and metastatic tumors. However, the impact of IR on the immune response is currently being defined. Local and distant relapse after radiotherapy often occurs. The current rationale for the use of IR is based on direct cytotoxicity to cancer cells; however, recent studies have shown that reduction of tumor burden following ablative (large-dose) IR largely depends on type I IFN signaling and CD8(+) T-cell response. Here, we review recent findings indicating that antitumor effects of radiation are contributed by both innate and adaptive immune responses. We focus on immune mechanisms, including cytosolic DNA sensing pathways that bridge the traditional view of IR-mediated DNA damage to DNA-sensing immune pathways. Also, we discuss how the efficacy of radiotherapy might be enhanced by targeting nucleic acid-sensing pathways. These findings highlight the mechanisms governing tumor escape from the immune response and the therapeutic potential of synergistic strategies to improve the efficacy of radiotherapy via immunotherapeutic intervention.

HLA Class I Depleted hESC as a Source of Hypoimmunogenic Cells for Tissue Engineering Applications

BACKGROUND

Rapidly improving protocols for the derivation of autologous cells from stem cell sources is a welcome development. However, there are many circumstances when off-the-shelf universally immunocompatible cells may be needed. Embryonic stem cells (ESCs) provide a unique opportunity to modify the original source of differentiated cells to minimize their rejection by nonautologous hosts.

HYPOTHESIS

Immune rejection of nonautologous human embryonic stem cell (hESC) derivatives can be reduced by downregulating human leukocyte antigen (HLA) class I molecules, without affecting the ability of these cells to differentiate into specific lineages.

METHODS AND RESULTS

Beta-2-microglobulin (B2M) expression was decreased by lentiviral transduction using human anti-HLA class I light-chain B2M short hairpin RNA. mRNA levels of B2M were decreased by 90% in a RUES2-modified hESC line, as determined by quantitative real time-polymerase chain reaction analysis. The transduced cells were selected under puromycin pressure and maintained in an undifferentiated state. The latter was confirmed by Oct4 and Nanog expression, and by the formation of characteristic round-shaped colonies. B2M downregulation led to diminished HLA-I expression on the cell surface, as determined by flow cytometry. When used as target cells in a mixed lymphocyte reaction assay, transduced hESCs and their differentiated derivatives did not stimulate allogeneic T-cell proliferation. Using a cardiac differentiation protocol, transduced hESCs formed a confluent layer of cardiac myocytes and maintained a low level of B2M expression. Transduced hESCs were also successfully differentiated into a hepatic lineage, validating their capacity to differentiate into multiple lineages.

CONCLUSIONS

HLA-I depletion does not preclude hESC differentiation into cardiac or hepatic lineages. This methodology can be used to engineer tissue from nonautologous hESC sources with improved immunocompatibility.

The pharmacology of second-generation chimeric antigen receptors

Second-generation chimeric antigen receptors (CARs) retarget and reprogramme T cells to augment their antitumour efficacy. The combined activating and co-stimulatory domains incorporated in these CARs critically determine the function, differentiation, metabolism and persistence of engineered T cells. CD19-targeted CARs that incorporate CD28 or 4-1BB signalling domains are the best known to date. Both have shown remarkable complete remission rates in patients with refractory B cell malignancies. Recent data indicate that CD28-based CARs direct a brisk proliferative response and boost effector functions, whereas 4-1BB-based CARs induce a more progressive T cell accumulation that may compensate for less immediate potency. These distinct kinetic features can be exploited to further develop CAR-based T cell therapies for a variety of cancers. A new field of immunopharmacology is emerging.

The role of lymphocytes in the development and treatment of alopecia areata

Alopecia areata (AA) development is associated with both innate and adaptive immune cell activation, migration to peri- and intra-follicular regions, and hair follicle disruption. Both CD4(+) and CD8(+) lymphocytes are abundant in AA lesions; however, CD8(+) cytotoxic T lymphocytes are more likely to enter inside hair follicles, circumstantially suggesting that they have a significant role to play in AA development. Several rodent models recapitulate important features of the human autoimmune disease and demonstrate that CD8(+) cytotoxic T lymphocytes are fundamentally required for AA induction and perpetuation. However, the initiating events, the self-antigens involved, and the molecular signaling pathways, all need further exploration. Studying CD8(+) cytotoxic T lymphocytes and their fate decisions in AA development may reveal new and improved treatment approaches.

Immunoregulatory molecules in patients with gestational diabetes mellitus

Induction of maternal-fetal immune tolerance is essential for the development of normal pregnancy. Impaired expression of costimulatory molecules may lead to intense inflammatory reaction, a mechanism involved in the pathophysiology of gestational diabetes mellitus (GDM). The aim of this study was to investigate whether immunoregulatory molecules are involved in the physiopathology of GDM. This case-control study included 30 healthy pregnant women and 20 GDM patients. Flow cytometry was used to assess peripheral blood T subpopulations (CD4(+) and CD8(+)), the expression of immunoregulatory molecules (CD28, ICOS, CTLA-4, and PD-1) and activation markers (CD69 and HLA-DR). Compared to healthy women, GDM patients had a significantly higher frequency of CD4(+)CD69(+) and CD8(+)CD69(+) T cells; only patients with insulin-treated GDM had increased numbers of CD4(+)HLA-DR(+) T cells. We also observed significantly higher percentages of CD4(+)CD28(+)HLA-DR(+), CD3(+)CD4(+)ICOS(+), CD3(+)CD4(+)PD-1(+), CD8(+)CD28(+)CD69(+), CD8(+)CD28(+)HLA-DR(+), CD8(+)CTLA-4(+)HLA-DR(+), and CD3(+)CD8(+)ICOS(+) T cells and lower frequency of CD3(+)CD4(+)CTLA-4(+), CD3(+)CD8(+)CTLA-4(+), and CD8(+)ICOS(+)HLA-DR(+) T cells in GDM patients compared to healthy pregnant women. This first study assessing costimulatory molecules in GDM patients shows that these patients have exacerbated markers of T cell activation along with CTLA-4 deficiency, findings that indicate that the maternal-fetal tolerance is compromised in these patients.

IL-Y, a synthetic member of the IL-12 cytokine family, suppresses the development of type 1 diabetes in NOD mice

The IL-12 family of heterodimeric cytokines, consisting of IL-12, IL-23, IL-27, and IL-35, has important roles in regulating the immune response. IL-12 family members are comprised of a heterodimer consisting of α and β chains: IL-12 (p40 and p35), IL-23 (p40 and p19), IL-27 (Ebi3 and p28), and IL-35 (Ebi3 and p35). Given the combinatorial nature of the IL-12 family, we generated adenoviral vectors expressing two putative IL-12 family members not yet found naturally, termed IL-X (Ebi3 and p19) and IL-Y (p40 and p28), as single-chain molecules. Single chain IL-Y (scIL-Y), but not scIL-X, was able to stimulate significantly a unique cytokine/chemokine expression profile as well as activate STAT3 in mice, in part, through a pathway involving IL-27Rα in splenocytes. Adenoviral-mediated, intratumoral delivery of scIL-Y increased tumor growth in contrast to the anti-tumor effects of scIL-12 and scIL-23. Similarly, treatment of prediabetic NOD mice by intravenous injection of Ad.scIL-Y prevented the onset of hyperglycemia. Analysis of cells from Ad.scIL-Y-treated NOD mice demonstrated that scIL-Y reduced expression of inflammatory mediators such as IFN-γ. Our data demonstrate that a novel, synthetic member of the IL-12 family, termed IL-Y, confers unique immunosuppressive effects in two different disease models and thus could have therapeutic applications.

Perspectives in the treatment of pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable lethal disease whose incidence rate is growing. There is no effective screening for detection of early stage tumors and, in most cases, PDAC is diagnosed at advanced disease stages, when radical pancreatic resection is not possible. The aggressive nature of pancreatic tumor cells lies in the complex genetic mechanisms behind their uncontrolled capability to grow and metastasize, which involve essential adaptive changes in cellular metabolism, signaling, adhesion and immunoediting. In addition, PDAC cells promote a dense functional stroma that facilitates tumor resistance to chemotherapy and radiation. During the last two decades, gemcitabine has been the reference for the systemic treatment of PDAC. However, recently, a regimen combining fluorouracil, irinotecan, oxaliplatin, and leucovorin (FOLFIRINOX) and another combining albumin-bound paclitaxel with gemcitabine have shown clear therapeutic advantage in advanced PDAC, with survival outcomes of 11.3 and 8.5 mo on phase III trials, respectively, over single-agent gemcitabine. With the pending issue of their higher toxicities, these regimens set the reference for ongoing and future clinical studies in advanced PDAC. In addition, the efficacy of oral fluoropyrimidine (S-1) has been well documented in Asiatic PDAC patients. The development of therapeutic approaches other than cytotoxic drugs has proven difficult in the past, with only one drug (erlotinib) approved to date. Besides, a number of agents targeting signaling pathways in tumor or stroma cells are being investigated. Likewise, immunotherapies that target PDAC in various ways are the subject of a number of clinical trials. The search for reliable biomarkers with diagnostic and prognostic value using genomics and mass spectrometry methods may facilitate monitoring and refinement of therapies. This review focuses on current understanding of the pathogenesis of PDAC and the latest developments in the treatment of advanced PDAC.

T-cell ligands modulate the cytolytic activity of the CD33/CD3 BiTE antibody construct, AMG 330

Preclinical and emerging clinical studies demonstrate that bispecific T-cell engaging (BiTE) antibody constructs can potently lyse targeted tumor cells, but the determinants for their activity remain incompletely understood. Using human acute myeloid leukemia (AML) cell lines engineered to overexpress individual T-cell ligands, we found that expression of the inhibitory ligands, PD-L1 and PD-L2, reduced the cytolytic activity of the BiTE antibody construct targeting CD33, AMG 330; conversely, expression of the activating ligands, CD80 and CD86, augmented the cytotoxic activity of AMG 330. Consistent with these findings, treatment with an activating antibody directed at the co-stimulatory T-cell receptor, CD28, significantly increased AMG 330-induced cytotoxicity in human AML cell lines. Using specimens from 12 patients with newly diagnosed or relapsed/refractory AML, we found that activation of CD28 also increased the activity of AMG 330 in primary human AML cells (P=0.023). Together, our findings indicate that T-cell ligands and co-receptors modulate the anti-tumor activity of the CD33/CD3 BiTE antibody construct, AMG 330. These findings suggest that such ligands/co-receptors could serve as biomarkers of response and that co-treatment strategies with pharmacological modulators of T-cell receptor signaling could be utilized to further enhance the activity of this targeted therapeutic.

Novel Immune Check-Point Regulators in Tolerance Maintenance

The great success of anti-cytotoxic lymphocyte antigen 4 (CTLA4) and anti-programed cell death protein 1 (PD1) in cancer treatment has encouraged more effort in harnessing the immune response through immunomodulatory molecules in various diseases. The immunoglobulin (Ig) super family comprises the majority of immunomodulatory molecules. Discovery of novel Ig super family members has brought novel insights into the function of different immune cells in tolerance maintenance. In this review, we discuss the function of newly identified B7 family molecules, B7-H4 and V-domain Ig Suppressor of T cell Activation (VISTA), and the butyrophilin/butyrophilin-like family members. We discuss the current stages of immunomodulatory molecules in clinical trials of organ transplantation. The potential of engaging the novel Ig superfamily members in tolerance maintenance is also discussed. We conclude with the challenges remaining to manipulate these molecules in the immune response.

Characterization of the human T cell response to in vitro CD27 costimulation with varlilumab

Background

Clinical targeting of TNFR family of receptors (CD40, CD134 and CD137) with immunostimulatory monoclonal antibodies has been successful in cancer immunotherapy. However, targeting of CD27 with a mAb is a relatively new approach to provide costimulation of immune cells undergoing activation. Thus, activation of human CD27 (TNFRSF7) with a monoclonal antibody (varlilumab) has previously been demonstrated to result in T cell activation and anti-tumor activity in preclinical models, and is currently in early phase clinical trials in patients with advanced malignancies. In this study we used an in vitro system using human peripheral blood T cells to characterize the varlilumab-mediated costimulatory effects in combination with TCR stimulation in terms of phenotypic, transcriptional and functionality changes.

Methods

T cells were isolated from normal volunteer PBMCs using magnetic bead isolation kits and stimulated in vitro with plate bound anti-CD3 Ab (OKT3) and varlilumab or control Ab for 72 h. Activation profiles were monitored by ELISA or Luminex-based testing cytokine/chemokine releases, cell surface phenotyping for costimulatory and coinhibitory markers and CFSE dye dilution by proliferating T cells and Tregs. Changes in gene expression and transcriptome analysis of varlilumab-stimulated T cells was carried on Agilent Human whole genome microarray datasets using a suite of statistical and bioinformatic software tools.

Results

Costimulation of T cells with varlilumab required continuous TCR signaling as pre-activated T cells were unable to produce cytokines with CD27 signaling alone. Analysis of T cell subsets further revealed that memory CD4+ and CD8+ T cells were specifically activated with a bias toward CD8+ T lymphocyte proliferation. Activation was accompanied by upregulated cell surface expression of costimulatory [4-1BB, OX40, GITR and ICOS] and coinhibitory [PD-1] molecules. Importantly, varlilumab costimulation did not activate purified Tregs as measured by cytokine production, proliferation and suppression of dividing non-Treg T cells. Analysis of changes in gene expression during varlilumab stimulation of T cells revealed modulation of pro-inflammatory signatures consistent with cellular activation and proliferation, with the IL-2 pathway showing the highest frequency of gene modulation.

Conclusions

Altogether, the data reveal the requirements and T cell subtype-specific effects of CD27 costimulation, and helps select relevant biomarkers for studying the effects of varlilumab in patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-015-0080-2) contains supplementary material, which is available to authorized users.

1,25(OH)2D3 Promotes the Efficacy of CD28 Costimulation Blockade by Abatacept

Inhibition of the CD28:CD80/CD86 T cell costimulatory pathway has emerged as an effective strategy for the treatment of T cell–mediated inflammatory diseases. However, patient responses to CD28-ligand blockade by abatacept (CTLA-4-Ig) in conditions such as rheumatoid arthritis are variable and often suboptimal. In this study, we show that the extent to which abatacept suppresses T cell activation is influenced by the strength of TCR stimulation, with high-strength TCR stimulation being associated with relative abatacept insensitivity. Accordingly, cyclosporin A, an inhibitor of T cell stimulation via the TCR, synergized with abatacept to inhibit T cell activation. We also observed that 1,25-dihydroxyvitamin D3 enhanced the inhibition of T cell activation by abatacept, strongly inhibiting T cell activation driven by cross-linked anti-CD3, but with no effect upon anti-CD28 driven stimulation. Thus, like cyclosporin A, 1,25-dihydroxyvitamin D3 inhibits TCR-driven activation, thereby promoting abatacept sensitivity. Vitamin D3 supplementation may therefore be a useful adjunct for the treatment of conditions such as rheumatoid arthritis in combination with abatacept to promote the efficacy of treatment.

Progression of Lung Cancer Is Associated with Increased Dysfunction of T Cells Defined by Coexpression of Multiple Inhibitory Receptors

Dysfunctional T cells present in malignant lesions are characterized by a sustained and highly diverse expression of inhibitory receptors, also referred to as immune checkpoints. Yet, their relative functional significance in different cancer types remains incompletely understood. In this study, we provide a comprehensive characterization of the diversity and expression patterns of inhibitory receptors on tumor-infiltrating T cells from patients with non-small cell lung cancer. In spite of the large heterogeneity observed in the amount of PD-1, Tim-3, CTLA-4, LAG-3, and BTLA expressed on intratumoral CD8(+) T cells from 32 patients, a clear correlation was established between increased expression of these inhibitory coreceptors and progression of the disease. Notably, the latter was accompanied by a progressively impaired capacity of T cells to respond to polyclonal activation. Coexpression of several inhibitory receptors was gradually acquired, with early PD-1 and late LAG-3/BTLA expression. PD-1 blockade was able to restore T-cell function only in a subset of patients. A high percentage of PD-1(hi) T cells was correlated with poor restoration of T-cell function upon PD-1 blockade. Of note, PD-1(hi) expression marked a particularly dysfunctional T-cell subset characterized by coexpression of multiple inhibitory receptors and thus may assist in identifying patients likely to respond to inhibitory receptor-specific antibodies. Overall, these data may provide a framework for future personalized T-cell-based therapies aiming at restoration of tumor-infiltrating lymphocyte effector functions.

Blockade of the PD-1/PD-L1 axis augments lysis of AML cells by the CD33/CD3 BiTE antibody construct AMG 330: reversing a T-cell-induced immune escape mechanism

Bispecific T-cell engagers (BiTEs) are very effective in recruiting and activating T cells. We tested the cytotoxicity of the CD33/CD3 BiTE antibody construct AMG 330 on primary acute myeloid leukemia (AML) cells ex vivo and characterized parameters contributing to antileukemic cytolytic activity. The E:T ratio and the CD33 expression level significantly influenced lysis kinetics in long-term cultures of primary AML cells (n=38). AMG 330 induced T-cell-mediated proinflammatory conditions, favoring the upregulation of immune checkpoints on target and effector cells. Although not constitutively expressed at the time of primary diagnosis (n=123), PD-L1 was strongly upregulated on primary AML cells upon AMG 330 addition to ex vivo cultures (n=27, P<0.0001). This phenomenon was cytokine-driven as the sole addition of interferon (IFN)-γ and tumor necrosis factor-α also induced expression. Through blockade of the PD-1/PD-L1 interaction, AMG 330-mediated lysis (n=9, P=0.03), T-cell proliferation (n=9, P=0.01) and IFN-γ secretion (n=8, P=0.008) were significantly enhanced. The combinatorial approach was most beneficial in settings of protracted AML cell lysis. Taken together, we have characterized a critical resistance mechanism employed by primary AML cells under AMG 330-mediated proinflammatory conditions. Our results support the evaluation of checkpoint molecules in upcoming clinical trials with AMG 330 to enhance BiTE antibody construct-mediated cytotoxicity.

Cellular FLIP Inhibits Myeloid Cell Activation by Suppressing Selective Innate Signaling

Cellular FLIP (c-FLIP) specifically inhibits caspase-8 and suppresses death receptor-induced apoptosis. c-FLIP has also been reported to transmit activation signals. In this study, we report a novel function of c-FLIP involving inhibition of myeloid cell activation through antagonizing the selective innate signaling pathway. We found that conditional knockout of c-FLIP in dendritic cells (DCs) led to neutrophilia and splenomegaly. Peripheral DC populations, including CD11b(+) conventional DCs (cDCs), CD8(+) cDCs, and plasmacytoid DCs, were not affected by c-FLIP deficiency. We also found that c-FLIP knockout cDCs, plasmacytoid DCs, and bone marrow-derived DCs (BMDCs) displayed enhanced production of TNF-α, IL-2, or G-CSF in response to stimulation of TLR4, TLR2, and dectin-1. Consistent with the ability of c-FLIP to inhibit the activation of p38 MAPK, the enhanced activation of c-FLIP-deficient BMDCs could be partly linked to an elevated activation of p38 MAPK after engagement of innate receptors. Increased activation was also found in c-FLIP(+/-) macrophages. Additionally, the increased activation in c-FLIP-deficient DCs was independent of caspase-8. Our results reveal a novel inhibitory role of c-FLIP in myeloid cell activation and demonstrate the unexpected anti-inflammatory activity of c-FLIP. Additionally, our observations suggest that cancer therapy targeting c-FLIP downregulation may facilitate DC activation and increase T cell immunity.

Immune checkpoint inhibitors in melanoma

The potential to harness the power of the immune system and effectively treat patients with metastatic melanoma is finally being realized with the advent of immune checkpoint inhibitors. These new therapies herald a new era in the treatment of melanoma with the potential to produce very durable responses and possible cure for a subset of patients, though bring with them challenges including novel toxicities and nonconventional response patterns. This article reviews the currently available immune checkpoint inhibitors, potential biomarkers to predict response and promising investigational approaches including combination therapies.

Current advances in T-cell-based cancer immunotherapy

Cancer is a leading cause of death worldwide; due to the lack of ideal cancer biomarkers for early detection or diagnosis, most patients present with late-stage disease at the time of diagnosis, thus limiting the potential for successful treatment. Traditional cancer treatments, including surgery, chemotherapy and radiation therapy, have demonstrated very limited efficacy for patients with late-stage disease. Therefore, innovative and effective cancer treatments are urgently needed for cancer patients with late-stage and refractory disease. Cancer immunotherapy, particularly adoptive cell transfer, has shown great promise in the treatment of patients with late-stage disease, including those who are refractory to standard therapies. In this review, we will highlight recent advances and discuss future directions in adoptive cell transfer based cancer immunotherapy.

The Role of PKC-θ in CD4+ T Cells and HIV Infection: To the Nucleus and Back Again

Protein kinase C (PKC)-θ is the only member of the PKC family that has the ability to translocate to the immunological synapse between T cells and antigen-presenting cells upon T cell receptor and MHC-II recognition. PKC-θ interacts functionally and physically with other downstream effector molecules to mediate T cell activation, differentiation, and migration. It plays a critical role in the generation of Th2 and Th17 responses and is less important in Th1 and CTL responses. PKC-θ has been recently shown to play a role in the nucleus, where it mediates inducible gene expression in the development of memory CD4+ T cells. This novel PKC (nPKC) can up-regulate HIV-1 transcription and PKC-θ activators such as Prostratin have been used in early HIV-1 reservoir eradication studies. The exact manner of the activation of virus by these compounds and the role of PKC-θ, particularly its nuclear form and its association with NF-κB in both the cytoplasmic and nuclear compartments, needs further precise elucidation especially given the very important role of NF-κB in regulating transcription from the integrated retrovirus. Continued studies of this nPKC isoform will give further insight into the complexity of T cell signaling kinases.

High ratio of programmed cell death protein 1 (PD-1)(+)/CD8(+) tumor-infiltrating lymphocytes identifies a poor prognostic subset of extrahepatic bile duct cancer undergoing surgery plus adjuvant chemoradiotherapy

BACKGROUND AND PURPOSE

This study investigated the prognostic role of PD-L1 expression, PD-1(+) tumor-infiltrating lymphocytes (TILs), and the ratio of PD-1(+)/CD8(+) TILs in extrahepatic bile duct (EHBD) cancer.

MATERIALS AND METHODS

We analyzed 83 patients with EHBD cancer who underwent curative surgery plus fluoropyrimidine-based chemoradiotherapy (CRT). Expressions of PD-L1, PD-1, and CD8 were assessed by immunohistochemistry.

RESULTS

Fifty-six (68%) patients were PD-L1-positive, and its lower expression level was associated with hilar tumor location (P=0.044). A higher ratio of PD-1(+)/CD8(+) TILs was associated with poorer overall survival (OS) (P=0.032), relapse-free survival (RFS) (P=0.024), and distant metastasis-free survival (DMFS) (P=0.039) in Kaplan-Meier analyses, but survival differences were not observed according to the PD-L1 expression level. With Cox proportional hazards models, the ratio of PD-1(+)/CD8(+) TILs was the independent prognostic factor in OS (HR 2.47, 95% CI 1.04-5.86), RFS (HR 2.41, 95% CI 1.08-5.41), and DMFS (HR 2.67, 95% CI 1.00-7.11) after adjusting for other significant clinicopathologic variables.

CONCLUSION

A strong survival impact of the ratio of PD-1(+)/CD8(+) TILs was observed in EHBD cancer. In the poor prognostic subgroup, the blockade of the immune checkpoint in combination with conventional multimodality treatment needs to be considered.

Clinical significance of CD70 expression on T cells in human T-lymphotropic virus type-1 carriers and adult T cell leukemia/ lymphoma patients

Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL). Miscellaneous host immune surveillance systems control T-cell growth/leukemogenesis during HTLV-1 infection. We characterized CD70 and CD27 expression on lymphocytes of HTLV-1 carriers and patients with ATL (study approved by the local Medical Ethical Committee). High CD70 expression was observed on CD4 + CD25+ T cells from patients with acute-type ATL, while patients with smoldering- or chronic-type ATL and HTLV-1 carriers exhibited lower expression. Furthermore, significantly higher CD27 expression was observed on HTLV-1-specific CTLs. We found an association between CD70 expression on CD4 + T cells and HTLV-1 infection; increased CD70 expression was observed after exposure to Tax. Moreover, addition of anti-CD70 antibodies enhanced the CD107a surface mobilization of HTLV-1 Tax-specific CTLs following Tax-peptide stimulation in the PBMCs of carriers. These data demonstrate the important role of the CD70/CD27 axis in immune responses in HTLV-1 carriers and ATL patients.

Generation of lentivirus-induced dendritic cells under GMP-compliant conditions for adaptive immune reconstitution against cytomegalovirus after stem cell transplantation

Background

Reactivation of latent viruses such as human cytomegalovirus (HCMV) after allogeneic hematopoietic stem cell transplantation (HSCT) results in high morbidity and mortality. Effective immunization against HCMV shortly after allo-HSCT is an unmet clinical need due to delayed adaptive T cell development. Donor-derived dendritic cells (DCs) have a critical participation in stimulation of naïve T cells and immune reconstitution, and therefore adoptive DC therapy could be used to protect patients after HSCT. However, previous methods for ex vivo generation of adoptive donor-derived DCs were complex and inconsistent, particularly regarding cell viability and potency after thawing. We have previously demonstrated in humanized mouse models of HSCT the proof-of-concept of a novel modality of lentivirus-induced DCs (“SmyleDCpp65”) that accelerated antigen-specific T cell development.

Methods

Here we demonstrate the feasibility of good manufacturing practices (GMP) for production of donor-derived DCs consisting of monocytes from peripheral blood transduced with an integrase-defective lentiviral vector (IDLV, co-expressing GM-CSF, IFN-α and the cytomegalovirus antigen pp65) that were cryopreserved and thawed.

Results

Upscaling and standardized production of one lot of IDLV and three lots of SmyleDCpp65 under GMP-compliant conditions were feasible. Analytical parameters for quality control of SmyleDCpp65 identity after thawing and potency after culture were defined. Cell recovery, uniformity, efficacy of gene transfer, purity and viability were high and consistent. SmyleDCpp65 showed only residual and polyclonal IDLV integration, unbiased to proto-oncogenic hot-spots. Stimulation of autologous T cells by GMP-grade SmyleDCpp65 was validated.

Conclusion

These results underscore further developments of this individualized donor-derived cell vaccine to accelerate immune reconstitution against HCMV after HSCT in clinical trials.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0599-5) contains supplementary material, which is available to authorized users.

Harnessing the immune system for cancer therapy

PURPOSE OF REVIEW

Over the last 18 months, substantial progress has been made in demonstrating the clinical efficacy of harnessing the immune system to treat a variety of both solid and hematologic malignancies. This review summarizes and evaluates these seminal studies.

RECENT FINDINGS

The two treatment modalities most responsible for the success of immune based therapies in cancer are adoptive T-cell therapy and immunoregulatory antibodies. Specifically, immunotherapy is generating responses in malignancies that would otherwise have no traditional curative options such as CD19-targeted chimeric antigen receptors to treat relapsed/refractory acute lymphocytic leukemia and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and PD-1 blockade alone or in combination to treat metastatic melanoma and other solid tumors.

SUMMARY

We are at a turning point for the field of cancer immunotherapy. The scientific community is now, after decades of research, proving that these treatments have great promise for patients. Ongoing preclinical research and clinical trials over the next few years will determine the extent of impact cancer immunotherapy will have on the treatment of the general population.

Boosting Cancer Immunotherapy with Anti-CD137 Antibody Therapy

In the past 5 years, immunomodulatory antibodies have revolutionized cancer immunotherapy. CD137, a member of the tumor necrosis factor receptor superfamily, represents a promising target for enhancing antitumor immune responses. CD137 helps regulate the activation of many immune cells, including CD4(+) T cells, CD8(+) T cells, dendritic cells, and natural killer cells. Recent studies indicate that the antitumor efficacy of therapeutic tumor-targeting antibodies can be augmented by the addition of agonistic antibodies targeting CD137. As ligation of CD137 provides a costimulatory signal in multiple immune cell subsets, combination therapy of CD137 antibody with therapeutic antibodies and/or vaccination has the potential to improve cancer treatment. Recently, clinical trials of combination therapies with agonistic anti-CD137 mAbs have been launched. In this review, we discuss the recent advances and clinical promise of agonistic anti-CD137 monoclonal antibody therapy.

Antibody fusions with immunomodulatory proteins for cancer therapy

The potential of immunomodulatory proteins, in particular cytokines, for cancer therapy is well recognized, but hampered by the toxicity associated with their systemic application. In order to address this problem, targeted delivery by antibody fusion proteins has been early proposed and their development intensively pursued over the last decade. Here, factors influencing the selection and modification of cytokines and antibody formats for this approach are being discussed, indicating current developments and translational advances in the field.

Immune checkpoint blockade opens an avenue of cancer immunotherapy with a potent clinical efficacy

Recent progress in tumor immunology has revealed that tumors generate immunologically restrained milieu during the process of their growth, which facilitates the escape of tumors from host immune systems. Immune checkpoint molecules, which transduce co-inhibitory signals to immuno-competent cells, are one of the most important components conferring the immunosuppressive capacity in the tumor microenvironment. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death-1 (PD-1) are typical immune checkpoint molecules intimately involved in the suppression of anti-tumor immunity. Antibodies against those molecules have been developed, such as ipilimumab (anti-CTLA-4 antibody), nivolumab and pembrolizumab (anti-PD-1 antibody), and have been approved by regulatory agencies and used in some countries. Treatment with these antibodies demonstrates previously unobserved clinical efficacies superior to the conventional therapies. In this review, we first discuss the escape mechanisms of cancer from host immune systems, and then focus on the recent advances in immune checkpoint blockade therapy and on the new findings of related immune reactions, aiming to provide a better understanding of the novel cancer immunotherapies.

Inhibitory Receptors Beyond T Cell Exhaustion

Inhibitory receptors (iRs) are frequently associated with "T cell exhaustion". However, the expression of iRs is also dependent on T cell differentiation and activation. Therapeutic blockade of various iRs, also referred to as "checkpoint blockade", is showing -unprecedented results in the treatment of cancer patients. Consequently, the clinical potential in this field is broad, calling for increased research efforts and rapid refinements in the understanding of iR function. In this review, we provide an overview on the significance of iR expression for the interpretation of T cell functionality. We summarize how iRs have been strongly associated with "T cell exhaustion" and illustrate the parallel evidence on the importance of T cell differentiation and activation for the expression of iRs. The differentiation subsets of CD8 T cells (naïve, effector, and memory cells) show broad and inherent differences in iR expression, while activation leads to strong upregulation of iRs. Therefore, changes in iR expression during an immune response are often concomitant with T cell differentiation and activation. Sustained expression of iRs in chronic infection and in the tumor microenvironment likely reflects a specialized T cell differentiation. In these situations of prolonged antigen exposure and chronic inflammation, T cells are "downtuned" in order to limit tissue damage. Furthermore, we review the novel "checkpoint blockade" treatments and the potential of iRs as biomarkers. Finally, we provide recommendations for the immune monitoring of patients to interpret iR expression data combined with parameters of activation and differentiation of T cells.

PD-L1 and Survival in Solid Tumors: A Meta-Analysis

Background

Numerous agents targeting PD-L1/PD-1 check-point are in clinical development. However, the correlation between PD-L1expression and prognosis of solid tumor is still in controversial. Here, we elicit a systematic review and meta-analysis to investigate the potential value of PD-L1 in the prognostic prediction in human solid tumors.

Methods

Electronic databases were searched for studies evaluating the expression of PD-L1 and overall survival (OS) of patients with solid tumors. Odds ratios (ORs) from individual studies were calculated and pooled by using a random-effect model, and heterogeneity and publication bias analyses were also performed.

Results

A total of 3107 patients with solid tumor from 28 published studies were included in the meta-analysis. The median percentage of solid tumors with PD-L1 overexpression was 52.5%. PD-L1 overexpression was associated with worse OS at both 3 years (OR = 2.43, 95% confidence interval (CI) = 1.60 to 3.70, P < 0.0001) and 5 years (OR = 2.23, 95% CI = 1.40 to 3.55, P = 0.0008) of solid tumors. Among the tumor types, PD-L1 was associated with worse 3 year-OS of esophageal cancer, gastric cancer, hepatocellular carcinoma, and urothelial cancer, and 5 year-OS of esophageal cancer, gastric cancer and colorectal cancer.

Conclusions

These results suggest that expression of PD-L1 is associated with worse survival in solid tumors. However, the correlations between PD-L1 and prognosis are variant among different tumor types. More studies are needed to investigate the clinical value of PD-L1 expression in prognostic prediction and treatment option.

The intravenous injection of oxidized LDL- or Apolipoprotein B100--Coupled splenocytes promotes Th1 polarization in wildtype and Apolipoprotein E--Deficient mice

BACKGROUND

Th1 responses in atherosclerosis are mainly associated with the aggravation of atherosclerotic plaques, whereas Th2 responses lead to a less pronounced disease in mouse models. The fixation of antigens on cells by means of ethylene carbodiimide (ECDI), and subsequent injection of these antigen-coupled splenocytes (Ag-SP) to induce tolerance against the attached antigens, has been successfully used to treat murine type 1 diabetes or encephalomyelitis in. We analyzed this approach in a mouse model for atherosclerosis.

METHODS AND RESULTS

OTII-transgenic mice that were treated with a single dose of 5 × 10(7) OVA-coupled splenocytes (OVA-SP), had decreased splenocyte proliferation, and lower IFNγ production in vitro upon antigen recall. However, in vivo CD4 cell activation was increased. To try lipoprotein-derived, "atherosclerosis-associated" antigens, we first tested human oxidized LDL. In wild type mice, an increase of IFNγ production upon in vitro recall was detected in the oxLDL-SP group. In Apolipoprotein E - deficient (ApoE-/-) mice that received oxLDL-SP every 5 weeks for 20 weeks, we did not find any difference of atherosclerotic plaque burden, but again increased IFNγ production. To overcome xenogenous limitations, we then examined the effects of mouse Apolipoprotein B100 peptides P3 and P6. ApoB100-SP treatment again promoted a more IFNγ pronounced response upon in vitro recall. Flow cytometry analysis of cytokine secreting spleen cells revealed CD4 positive T cells to be mainly the source for IFNγ. In ApoE-/- mice that were administered ApoB100-SP during 20 weeks, the atherosclerotic plaque burden in aortic roots as well as total aorta was unchanged compared to PBS treated controls. Splenocyte proliferation upon antigen recall was not significantly altered in ApoB100-SP treated ApoE-/- mice.

CONCLUSION

Although we did not observe a relevant anti-atherosclerotic benefit, the treatment with antigen-coupled splenocytes in its present form already impacts the immune responses and deserves further exploration.

Hypoxia-induced soluble CD137 in malignant cells blocks CD137L-costimulation as an immune escape mechanism

Hypoxia is a common feature in solid tumors that has been implicated in immune evasion. Previous studies from our group have shown that hypoxia upregulates the co-stimulatory receptor CD137 on activated T lymphocytes and on vascular endothelial cells. In this study, we show that exposure of mouse and human tumor cell lines to hypoxic conditions (1% O₂) promotes CD137 transcription. However, the resulting mRNA is predominantly an alternatively spliced form that encodes for a soluble variant, lacking the transmembrane domain. Accordingly, soluble CD137 (sCD137) is detectable by ELISA in the supernatant of hypoxia-exposed cell lines and in the serum of tumor-bearing mice. sCD137, as secreted by tumor cells, is able to bind to CD137-Ligand (CD137L). Our studies on primed T lymphocytes in co-culture with stable transfectants for CD137L demonstrate that tumor-secreted sCD137 prevents co-stimulation of T lymphocytes. Such an effect results from preventing the interaction of CD137L with the transmembrane forms of CD137 expressed on T lymphocytes undergoing activation. Indeed, silencing CD137 with shRNA renders more immunogenic tumor-cell variants upon inoculation to immunocompetent mice but which readily grafted on immunodeficient or CD8⁺ T-cell-depleted mice. These mechanisms are interpreted as a molecular strategy deployed by tumors to repress lymphocyte co-stimulation via CD137/CD137L.

Surfing the Protein-Protein Interaction Surface Using Docking Methods: Application to the Design of PPI Inhibitors

Blocking protein-protein interactions (PPI) using small molecules or peptides modulates biochemical pathways and has therapeutic significance. PPI inhibition for designing drug-like molecules is a new area that has been explored extensively during the last decade. Considering the number of available PPI inhibitor databases and the limited number of 3D structures available for proteins, docking and scoring methods play a major role in designing PPI inhibitors as well as stabilizers. Docking methods are used in the design of PPI inhibitors at several stages of finding a lead compound, including modeling the protein complex, screening for hot spots on the protein-protein interaction interface and screening small molecules or peptides that bind to the PPI interface. There are three major challenges to the use of docking on the relatively flat surfaces of PPI. In this review we will provide some examples of the use of docking in PPI inhibitor design as well as its limitations. The combination of experimental and docking methods with improved scoring function has thus far resulted in few success stories of PPI inhibitors for therapeutic purposes. Docking algorithms used for PPI are in the early stages, however, and as more data are available docking will become a highly promising area in the design of PPI inhibitors or stabilizers.

Inhibition of Donor-Reactive CD8+ T Cell Responses by Selective CD28 Blockade Is Independent of Reduced ICOS Expression

Programmed T cell differentiation is critically influenced by the complement of costimulatory and coinhibitory signals transmitted during initial antigen encounter. We previously showed that selective CD28 blockade with novel domain antibodies that leave CTLA-4-mediated coinhibitory signaling intact resulted in more profound attenuation of donor-reactive T cell responses and improved graft survival in a murine transplant model. Selective CD28 blockade was also associated with decreased ICOS expression on donor-reactive CD8⁺ T cell responses as compared to CTLA-4 Ig, but the functional importance of this reduced ICOS expression was not known. In this study, we created retrogenic donor-reactive CD8⁺ T cells that overexpress ICOS in order to determine whether reduced ICOS expression mechanistically underlies the increased efficacy of selective CD28 blockade in controlling graft-specific T cell responses as compared to conventional costimulation blockade with CTLA-4 Ig. Results indicated that the ability of selective CD28 blockade to blunt donor-reactive CD8⁺ T cell expansion following transplantation was independent of its ability to inhibit ICOS expression. Furthermore, we have previously published that 2B4 coinhibitory signals are functionally important for controlling graft-specific CD8⁺ T cell responses in mice treated with CD28 blockade. Here we used a co-adoptive transfer approach to determine that 2B4 coinhibitory signals on antigen-specific CD8⁺ T cells function in a cell-intrinsic manner to limit ICOS expression in the setting of selective CD28 blockade.

Charting Immune Signaling Proteomes En Route to New Therapeutic Strategies

The activation state of an antitumor effector T cell in a tumor depends on the sum of all stimulatory signals and inhibitory signals that it receives in the tumor microenvironment. Accumulating data address the increasing complexity of these signals produced by a myriad of immune checkpoint molecules, cytokines, and metabolites. While reductionist experiments have identified key molecules and their importance in signaling, less clear is the integration of all these signals that allows T cells to guide their responses in health and in disease. Mass spectrometry-based proteomics is well poised to offer such insights, including monitoring emergence of resistance mechanisms to immunotherapeutics during treatments. A major application of this technology is in the discovery and characterization of small-molecule agents capable of enhancing the response to immunotherapeutic agents. Such an approach would reinvigorate small-molecule drug development aimed not at tumor cells but rather at tumor-resident T cells capable of producing dramatic and durable antitumor responses.

Clinical Development of Immune Checkpoint Inhibitors

Recent progress in cancer immunotherapy has been remarkable. Most striking are the clinical development and approval of immunomodulators, also known as immune checkpoint inhibitors. These monoclonal antibodies (mAb) are directed to immune checkpoint molecules, which are expressed on immune cells and mediate signals to attenuate excessive immune reactions. Although mAbs targeting tumor associated antigens, such as anti-CD20 mAb and anti-Her2 mAb, directly recognize tumor cells and induce cell death, immune checkpoint inhibitors restore and augment the antitumor immune activities of cytotoxic T cells by blocking immune checkpoint molecules on T cells or their ligands on antigen presenting and tumor cells. Based on preclinical data, many clinical trials have demonstrated the acceptable safety profiles and efficacies of immune checkpoint inhibitors in a variety of cancers. The first in class approved immune checkpoint inhibitor is ipilimumab, an anti-CTLA-4 (cytotoxic T lymphocyte antigen-4) mAb. Two pivotal phase III randomized controlled trials demonstrated a survival benefit in patients with metastatic melanoma. In 2011, the US Food and Drug Administration (FDA) approved ipilimumab for metastatic melanoma. Several clinical trials have since investigated new agents, alone and in combination, for various cancers. In this review, we discuss the current development status of and future challenges in utilizing immune checkpoint inhibitors.