Blockade of PD-L1 (B7-H1) augments human tumor-specific T cell responses in vitro

CRISPR-Cas9 mediated efficient PD-1 disruption on human primary T cells from cancer patients

Strategies that enhance the function of T cells are critical for immunotherapy. One negative regulator of T-cell activity is ligand PD-L1, which is expressed on dentritic cells (DCs) or some tumor cells, and functions through binding of programmed death-1 (PD-1) receptor on activated T cells. Here we described for the first time a non-viral mediated approach to reprogram primary human T cells by disruption of PD-1. We showed that the gene knockout of PD-1 by electroporation of plasmids encoding sgRNA and Cas9 was technically feasible. The disruption of inhibitory checkpoint gene PD-1 resulted in significant reduction of PD-1 expression but didn't affect the viability of primary human T cells during the prolonged in vitro culture. Cellular immune response of the gene modified T cells was characterized by up-regulated IFN-γ production and enhanced cytotoxicity. These results suggest that we have demonstrated an approach for efficient checkpoint inhibitor disruption in T cells, providing a new strategy for targeting checkpoint inhibitors, which could potentialy be useful to improve the efficacy of T-cell based adoptive therapies.

Expression of programmed death 1 ligand 1 on periodontal tissue cells as a possible protective feedback mechanism against periodontal tissue destruction

Programmed death 1 ligand 1 (PD-L1) is a negative co-stimulatory molecule in immune responses. Previous reports have indicated that inflammatory cytokines can upregulate the expression of PD-L1 in tumor cells, which in turn suppresses host immune responses. Periodontitis is characterized by persistent inflammation of the periodontium, which is initiated by infection with oral bacteria and results in damage to cells and the matrices of the periodontal connective tissues. In the present study, the expression and function of PD-L1 in periodontal tissue destruction were examined. Periodontal ligament cells (PDLCs) were stimulated by inflammatory cytokines and periodontal pathogens. The expression and function of PD-L1 on the surface of PDLCs was investigated using flow cytometry in vitro. Periodontal disease was induced by the injection of Porphyromonas gingivalis in mouse models. The expression levels of PD-L1 in the periodontal tissues of the mice were analyzed using flow cytometry and immunohistochemistry. PD-L1 was inducibly expressed on the PDLCs by the inflammatory cytokines and periodontal pathogens. The inflammation-induced expression of PD-L1 was shown to cause the apoptosis of activated T lymphocytes and improve the survival of PDLCs. Furthermore, in the mouse model of experimental periodontitis, the expression of PD-L1 in severe cases of periodontitis was significantly lower, compared with that in mild cases. By contrast, no significant differences were observed between the healthy control and severe periodontitis groups. The results of the present study showed that the expression of PD-L1 may inhibit the destruction of periodontal tissues, indicating the involvement of a possible protective feedback mechanism against periodontal infection.

Low immunogenicity in non-small cell lung cancer; do new developments and novel treatments have a role?

Approximately 1.6 million new cases of lung cancer are diagnosed annually (Jemal et al. CA: A Cancer Journal for Clinicians, 61, 69-90, 2011) and it remains the leading cause of cancer-related mortality worldwide. Despite decades of bench and clinical research to attempt to improve outcome for locally advanced, good performance status patients, the 5-year survival remains less than 15 % (Molina et al. 2008). Immune checkpoint inhibitor (ICH) therapies have shown a significant promise in preclinical and clinical trails to date in the treatment of non-small cell lung cancer (NSCLC). The idea of combining these systemic immune therapies with local ablative techniques is one that is gaining momentum. Electrochemotherapy (ECT) is a unique atraumatic local therapy that has had very promising objective response rates and a number of advantages including but not limited to its immunostimulatory effects. ECT in combination with ICHs offers a novel approach for dealing with this difficult disease process.

PDL1 Regulation by p53 via miR-34

BACKGROUND

Although clinical studies have shown promise for targeting PD1/PDL1 signaling in non-small cell lung cancer (NSCLC), the regulation of PDL1 expression is poorly understood. Here, we show that PDL1 is regulated by p53 via miR-34.

METHODS

p53 wild-type and p53-deficient cell lines (p53(-/-) and p53(+/+) HCT116, p53-inducible H1299, and p53-knockdown H460) were used to determine if p53 regulates PDL1 via miR-34. PDL1 and miR-34a expression were analyzed in samples from patients with NSCLC and mutated p53 vs wild-type p53 tumors from The Cancer Genome Atlas for Lung Adenocarcinoma (TCGA LUAD). We confirmed that PDL1 is a direct target of miR-34 with western blotting and luciferase assays and used a p53(R172HΔ)g/+K-ras(LA1/+) syngeneic mouse model (n = 12) to deliver miR-34a-loaded liposomes (MRX34) plus radiotherapy (XRT) and assessed PDL1 expression and tumor-infiltrating lymphocytes (TILs). A two-sided t test was applied to compare the mean between different treatments.

RESULTS

We found that p53 regulates PDL1 via miR-34, which directly binds to the PDL1 3' untranslated region in models of NSCLC (fold-change luciferase activity to control group, mean for miR-34a = 0.50, SD = 0.2, P < .001; mean for miR-34b = 0.52, SD = 0.2, P = .006; and mean for miR-34c = 0.59, SD = 0.14, and P = .006). Therapeutic delivery of MRX34, currently the subject of a phase I clinical trial, promoted TILs (mean of CD8 expression percentage of control group = 22.5%, SD = 1.9%; mean of CD8 expression percentage of MRX34 = 30.1%, SD = 3.7%, P = .016, n = 4) and reduced CD8(+)PD1(+) cells in vivo (mean of CD8/PD1 expression percentage of control group = 40.2%, SD = 6.2%; mean of CD8/PD1 expression percentage of MRX34 = 20.3%, SD = 5.1%, P = .001, n = 4). Further, MRX34 plus XRT increased CD8(+) cell numbers more than either therapy alone (mean of CD8 expression percentage of MRX34 plus XRT to control group = 44.2%, SD = 8.7%, P = .004, n = 4). Finally, miR-34a delivery reduced the numbers of radiation-induced macrophages (mean of F4-80 expression percentage of control group = 52.4%, SD = 1.7%; mean of F4-80 expression percentage of MRX34 = 40.1%, SD = 3.5%, P = .008, n = 4) and T-regulatory cells.

CONCLUSIONS

We identified a novel mechanism by which tumor immune evasion is regulated by p53/miR-34/PDL1 axis. Our results suggest that delivery of miRNAs with standard therapies, such as XRT, may represent a novel therapeutic approach for lung cancer.

Sunitinib pretreatment improves tumor-infiltrating lymphocyte expansion by reduction in intratumoral content of myeloid-derived suppressor cells in human renal cell carcinoma

Targeted therapy with sunitinib, pazopanib or everolimus has improved treatment outcome for patients with metastatic renal cell carcinoma patients (RCC). However, despite considerable efforts in sequential or combined modalities, durable remissions are rare. Immunotherapy like cytokine therapy with interleukin-2, T cell checkpoint blockade or adoptive T cell therapies can achieve long-term benefit and even cure. This raises the question of whether combining targeted therapy with immunotherapy could also be an effective treatment option for RCC patients. Sunitinib, one of the most frequently administered therapeutics in RCC patients has been implicated in impairing T cell activation and proliferation in vitro. In this work, we addressed whether this notion holds true for expansion of tumor-infiltrating lymphocytes (TILs) in sunitinib-treated patients. We compared resected primary RCC tumor material of patients pretreated with sunitinib with resection specimen from sunitinib-naïve patients. We found improved TIL expansion from sunitinib-pretreated tumor digests. These TIL products contained more PD-1 expressing TIL, while the regulatory T cell infiltration was not altered. The improved TIL expansion was associated with reduced intratumoral myeloid-derived suppressor cell (MDSC) content. Depletion of MDSCs from sunitinib-naïve RCC tissue-digest improved TIL expansion, proving the functional relevance of the MDSC alteration by sunitinib. Our in vivo results do not support previous in vitro observations of sunitinib inhibiting T cell function, but do provide a possible rationale for the combination of sunitinib with immunotherapy.

Targeting immune checkpoints: New opportunity for mesothelioma treatment?

Malignant pleural mesothelioma is an aggressive cancer linked to asbestos exposure in most patients. Due to the long latency between exposure and presentation, incidence is expected to further increase in the next decade, despite the ban on asbestos import which occurred at the end of last century in industrialized countries. Platinum-based palliative chemotherapy is the only treatment with proven benefit on outcome, resulting in selected patients in a median overall survival of about 1 year. Therefore, there is room for therapeutic improvement using a new strategy to prolong survival. Dealing with cancer cell induced immunosuppression is a promising approach. Reactivating immune responses that are silenced by immune checkpoints recently gained a lot of interest. Checkpoint blockade has already shown promising preclinical and clinical results in several cancer types and is currently also being investigated in mesothelioma. Here, we discuss the expression patterns and mechanisms of action of CTLA-4 and PD-1 as the two most studied and of TIM-3 and LAG-3 as two interesting upcoming immune checkpoints. Furthermore, we review the clinical results of molecules blocking these immune checkpoints and point out their future opportunities with a special focus on mesothelioma.

Overcoming tumor-mediated immunosuppression

Mechanisms of tumor-mediated immunosuppression have been described for several solid and hematological tumors. Tumors inhibit immune responses by attraction of immunosuppressive lymphocytic populations, secretion of immunosuppressive cytokines or expression of surface molecules, which inhibit immune responses by induction of anergy or apoptosis in tumor-infiltrating lymphocytes. This tumor-mediated immunosuppression represents a major obstacle to many immunotherapeutic or conventional therapeutic approaches. In this review we discuss how tumor-mediated immunosuppression interferes with different immunotherapeutic approaches and then give an overview of strategies to overcome it. Particular emphasis is placed on agents or approaches already transferred into clinical settings. Finally the success of immune checkpoint inhibitors targeting CTLA-4 or the PD-1 pathway highlights the enormous therapeutic potential of an effective overcoming of tumor-mediated immunosuppression.

Assessing a novel immuno-oncology-based combination therapy: Ipilimumab plus electrochemotherapy

Melanoma is responsible for most skin cancer-related deaths and is one of the most common cancers diagnosed in young adults. In melanoma, tumors can become established by activation of the negative regulator of cytotoxic T lymphocytes (CTLs), CTL antigen-4 (CTLA-4). Ipilimumab blocks the interaction of CTLA-4 with CD80/CD86 and augments T-cell activation and proliferation. In electrochemotherapy (ECT), local application of short high-voltage pulses renders cell membranes transiently permeable to chemotherapeutic drugs. The combination of ipilimumab and ECT may be beneficial for the treatment of metastatic melanoma; however, no prospective data are available to date. Here, we report the retrospective analysis of patients treated with ipilimumab in an expanded access program (EAP) who also received ECT. Fifteen patients with previously treated metastatic melanoma who received ipilimumab 3 mg/kg every three weeks for four cycles and underwent ECT for local disease control and/or palliation of cutaneous lesions with bleomycin 15 mg/m2 after the first ipilimumab infusion were included in the analysis. Over the study period, a local objective response was observed in 67% of patients (27% complete response [CR] and 40% partial response [PR]). According to immune-related response criteria, a systemic response was observed in nine patients (five PR and four stable disease [SD]), resulting in a disease control rate of 60%. Evaluation of circulating T-regulatory (T-reg) cells demonstrated significant differences between responders and non-responders. Overall, treatment was well-tolerated and without notable toxicity. In conclusion, the combination of ipilimumab and ECT appears to be beneficial to patients with advanced melanoma, warranting further investigation in prospective trials.

Arming oncolytic viruses to leverage antitumor immunity

INTRODUCTION

Over the past decade, the cytolytic capabilities of oncolytic viruses (OVs), exploited to selectively eliminate neoplastic cells, have become secondary to their use to elicit a tumor-directed immune response.

AREAS COVERED

Here, based on an NCBI-PubMed literature survey, we review the efforts undertaken to arm OVs in order to improve therapeutic antitumor responses upon administration of these agents. Specifically, we explore the different options to modulate immune suppression in the tumor microenvironment (TME) and to facilitate the generation of effective antitumor responses that have been investigated in conjunction with OVs in recent years.

EXPERT OPINION

Their induction of immunogenic tumor cell death and association with pro-inflammatory signals make OVs attractive immunotherapeutic modalities. The first promising clinical results with immunologically armed OVs warrant their further optimization and development. OVs should be modified to avoid detrimental effects of pre-existent anti-OV immunity as well as for increased tumor targeting and selectivity, so as to ultimately allow for systemic administration while achieving local immune potentiation and tumor elimination in the TME. In particular, a combination of trans-genes encoding bispecific T-cell engagers, immune checkpoint blockers and antigen-presenting cell enhancers will remove suppressive hurdles in the TME and allow for optimal antitumor efficacy of armed OVs.

From humble beginnings to success in the clinic: Chimeric antigen receptor-modified T-cells and implications for immunotherapy

In the past 50 years, disease burden has steadily shifted from infectious disease to cancer. Standard chemotherapy has long been the mainstay of cancer medical management, and despite vast efforts towards more targeted and personalized drug therapy, many cancers remain refractory to treatment, with high rates of relapse and poor prognosis. Recent dramatic immunotherapy clinical trials have demonstrated that engineering T-cells with chimeric antigen receptors (CARs) to target CD19 can lead to complete remission in relapsed or refractory B-cell malignancies, generating a great deal of enthusiasm in the field. Here we provide a comprehensive overview of the history of adoptive T-cell therapy, including CARs, in solid tumors as well as hematologic malignancies. CAR therapy has the potential to fundamentally transform cancer treatment with specific and even personalized targeting of tissue- and tumor-specific antigens. However, before CARs become standard first-line treatment modalities, critical issues regarding efficacy, combinatorial regimens, and mechanisms of treatment failure and toxicity will need to be addressed.

Identification and Characterization of MEDI4736, an Antagonistic Anti-PD-L1 Monoclonal Antibody

Programmed cell-death 1 ligand 1 (PD-L1) is a member of the B7/CD28 family of proteins that control T-cell activation. Many tumors can upregulate expression of PD-L1, inhibiting antitumor T-cell responses and avoiding immune surveillance and elimination. We have identified and characterized MEDI4736, a human IgG1 monoclonal antibody that binds with high affinity and specificity to PD-L1 and is uniquely engineered to prevent antibody-dependent cell-mediated cytotoxicity. In vitro assays demonstrate that MEDI4736 is a potent antagonist of PD-L1 function, blocking interaction with PD-1 and CD80 to overcome inhibition of primary human T-cell activation. In vivo MEDI4736 significantly inhibits the growth of human tumors in a novel xenograft model containing coimplanted human T cells. This activity is entirely dependent on the presence of transplanted T cells, supporting the immunological mechanism of action for MEDI4736. To further determine the utility of PD-L1 blockade, an anti-mouse PD-L1 antibody was investigated in immunocompetent mice. Here, anti-mouse PD-L1 significantly improved survival of mice implanted with CT26 colorectal cancer cells. The antitumor activity of anti-PD-L1 was enhanced by combination with oxaliplatin, which resulted in increased release of HMGB1 within CT26 tumors. Taken together, our results demonstrate that inhibition of PD-L1 function can have potent antitumor activity when used as monotherapy or in combination in preclinical models, and suggest it may be a promising therapeutic approach for the treatment of cancer. MEDI4736 is currently in several clinical trials both alone and in combination with other agents, including anti-CTLA-4, anti-PD-1, and inhibitors of IDO, MEK, BRAF, and EGFR.

Clinicopathological and prognostic significance of programmed cell death ligand1 (PD-L1) expression in patients with non-small cell lung cancer: a meta-analysis

OBJECTIVE

Programmed cell death 1 (PD-1) and one of its ligands, PD-L1, are key immune checkpoint proteins. Evidences showed PD-L1 is an emerging biomarker for immunotherapy by anti-PD-1 and anti-PD-L1 antibody in non-small cell lung cancer (NSCLC). To investigate the association of PD-L1 protein expression with clinicopathological features and its impact on survival outcome, we conducted a meta-analysis.

METHODS

A comprehensive literature search of electronic databases (up to July 10, 2014) was performed. Correlation between PD-L1 expression and clinicopathological features and overall survival (OS) was analyzed by synthesizing the qualified data. Publication biases were examined.

RESULTS

A total of 1,550 NSCLC patients from 9 studies were included. The pooled odds ratios (ORs) indicated high PD-L1 expression was associated with poor tumor differentiation [OR =0.53, 95% confidence interval (CI): 0.39-0.72, P<0.0001]. Whereas, none of other clinicopathological characteristics [gender, smoking status, histological type, invasive depth of tumor, status of lymph node metastasis and tumor node metastasis (TNM) stage] were correlated with PD-L1 expression in current analysis. The combined hazard ratio (HR) for OS showed high expression of PD-L1 impaired the OS in NSCLC (HRpositive/negative =1.47, 95% CI: 1.19-1.83, P=0.0004).

CONCLUSIONS

Our meta-analysis indicated PD-L1 protein expression in NSCLC was not associated with common clinicopathological characteristics, except tumor differentiation. It was a poor prognostic biomarker for NSCLC. Further research should be performed to investigate the precise clinicopathological and prognostic significance of PD-L1 in NSCLC under uniform testing standard.

PD-L1 over-expression and survival in patients with non-small cell lung cancer: a meta-analysis

BACKGROUND

Observational studies on the prognostic role of programmed cell death-ligand 1 (PD-L1) in non-small cell lung cancer (NSCLC) are controversial.

METHODS

To clarify the impact of PD-L1 in NSCLC survival, we performed this meta-analysis that included eligible studies. The combined hazard ratios (HR) and their corresponding 95% confidence intervals (CIs) were calculated in terms of overall survival.

RESULTS

A total of five studies with 877 patients were evaluable for this meta-analysis. Our results suggested that PD-L1 overexpression had a poor impact on survival of patients with NSCLC, the HR (95% CI) was 1.43 (1.24-1.63) overall, 1.51 (1.24-1.7954) in Asian patients, 1.35 (1.08-1.63) in non-Asian patients. Moreover, there was no heterogeneity between the studies.

CONCLUSIONS

PD-L1 overexpression indicates a poor prognosis for patients with NSCLC.

Survival, Durable Response, and Long-Term Safety in Patients With Previously Treated Advanced Renal Cell Carcinoma Receiving Nivolumab

PURPOSE

Blockade of the programmed death-1 inhibitory cell-surface molecule on immune cells using the fully human immunoglobulin G4 antibody nivolumab mediates tumor regression in a portion of patients with advanced treatment-refractory solid tumors. We report clinical activity, survival, and long-term safety in patients with advanced renal cell carcinoma (RCC) treated with nivolumab in a phase I study with expansion cohorts.

PATIENTS AND METHODS

A total of 34 patients with previously treated advanced RCC, enrolled between 2008 and 2012, received intravenous nivolumab (1 or 10 mg/kg) in an outpatient setting once every two weeks for up to 96 weeks and were observed for survival and duration of response after treatment discontinuation.

RESULTS

Ten patients (29%) achieved objective responses (according to RECIST [version 1.0]), with median response duration of 12.9 months; nine additional patients (27%) demonstrated stable disease lasting > 24 weeks. Three of five patients who stopped treatment while in response continued to respond for ≥ 45 weeks. Median overall survival in all patients (71% with two to five prior systemic therapies) was 22.4 months; 1-, 2-, and 3-year survival rates were 71%, 48%, and 44%, respectively. Grade 3 to 4 treatment-related adverse events occurred in 18% of patients; all were reversible.

CONCLUSION

Patients with advanced treatment-refractory RCC treated with nivolumab demonstrated durable responses that in some responders persisted after drug discontinuation. Overall survival is encouraging, and toxicities were generally manageable. Ongoing randomized clinical trials will further assess the impact of nivolumab on overall survival in patients with advanced RCC.

Novel strategies for inhibiting PD-1 pathway-mediated immune suppression while simultaneously delivering activating signals to tumor-reactive T cells

We previously developed cell-based vaccines as therapeutics for metastatic cancers. The vaccines were aimed at activating type I CD4(+)T cells and consisted of tumor cells transfected with genes encoding syngeneic MHC class II and CD80 costimulatory molecules, and lacking the MHC II-associated invariant chain. The vaccines showed some efficacy in mice with sarcoma, melanoma, and breast cancer and activated MHC class II syngeneic T cells from breast, lung, and melanoma patients. During the course of the vaccine studies, we observed that CD80 not only costimulated naïve T cells, but also bound to PD-L1 and prevented tumor cell-expressed PD-L1 from binding to its receptor PD-1 on activated T cells. A soluble form of CD80 (CD80-Fc) had the same effect and sustained IFNγ production by both human and murine PD-1(+) activated T cells in the presence of PD-L1(+) human or mouse tumor cells, respectively. In vitro studies with human tumor cells indicated that CD80-Fc was more effective than antibodies to either PD-1 or PD-L1 in sustaining T cell production of IFNγ. Additionally, in vivo studies with a murine tumor demonstrated that CD80-Fc was more effective than antibodies to PD-L1 in extending survival time. Studies with human T cells blocked for CD28 and with T cells from CD28 knockout mice demonstrated that CD80-Fc simultaneously inhibited PD-L1/PD-1-mediated immune suppression and delivered costimulatory signals to activated T cells, thereby amplifying T cell activation. These results suggest that CD80-Fc may be a useful monotherapy that minimizes PD-1 pathway immune suppression while simultaneously activating tumor-reactive T cells.

OX40 Agonists and Combination Immunotherapy: Putting the Pedal to the Metal

Recent studies have highlighted the therapeutic efficacy of immunotherapy, a class of cancer treatments that utilize the patient’s own immune system to destroy cancerous cells. Within a tumor the presence of a family of negative regulatory molecules, collectively known as “checkpoint inhibitors,” can inhibit T cell function to suppress anti-tumor immunity. Checkpoint inhibitors, such as CTLA-4 and PD-1, attenuate T cell proliferation and cytokine production. Targeted blockade of CTLA-4 or PD-1 with antagonist monoclonal antibodies (mAbs) releases the “brakes” on T cells to boost anti-tumor immunity. Generating optimal “killer” CD8 T cell responses also requires T cell receptor activation plus co-stimulation, which can be provided through ligation of tumor necrosis factor receptor family members, including OX40 (CD134) and 4-1BB (CD137). OX40 is of particular interest as treatment with an activating (agonist) anti-OX40 mAb augments T cell differentiation and cytolytic function leading to enhanced anti-tumor immunity against a variety of tumors. When used as single agents, these drugs can induce potent clinical and immunologic responses in patients with metastatic disease. However, each of these agents only benefits a subset of patients, highlighting the critical need for more effective combinatorial therapeutic strategies. In this review, we will discuss our current understanding of the cellular and molecular mechanisms by which OX40 agonists synergize with checkpoint inhibitor blockade to augment T cell-mediated anti-tumor immunity and the potential opportunities for clinical translation of combinatorial immunotherapeutic strategies.

B7-H1 enhances proliferation ability of gastric cancer stem-like cells as a receptor

Cancer stem-like cells (CSCs) are a rare tumorigenic population with the ability to self-renew in numerous cancer types. Their existence is considered a pivotal contributor to tumor recurrence. B7-H1 is a ligand of inhibitory inducible co-stimulator (ICOS) that is broadly expressed on various human cancers. ICOS acts as a ligand of programmed death-1 (PD-1) on T cells, induces the immune escape of cancer cells and also acts as a receptor mediating anti-apoptotic effects on cancer cells. However, the expression and function of B7-H1 on CSCs is not yet clear. In the present study, gastric cancer samples were collected and the B7-H1 expression in gastric cancer CSCs was detected. Ki67, a proliferation marker, was found to be expressed at a higher rate in B7-H1⁺ CSCs compared with the B7-H1^- counterparts. SGC-7901 cells, a gastric cancer cell line, were cultured in serum-free medium to form sphere cells that possessed stem cell characteristics and could express B7-H1 with the stimulation of interferon-γ. The proliferative ability of sphere cells was enhanced following B7-H1 activation with recombinant PD-1 in vivo and in vitro. This effect could be eliminated by neutralizing B7-H1. Overall, B7-H1 can act as a stimulating receptor for CSCs, and induce CSC proliferation. Blocking B7-H1 on CSCs may possess therapeutic potential for treating gastric cancer.

The prognostic value of PD-L1 expression for non-small cell lung cancer patients: a meta-analysis

BACKGROUND

A meta-analysis was conducted to investigate the much-debated relationship between the gene expression of programmed cell death-ligand 1 (PD-L1) and cancer patient prognosis. The prognostic value of measuring PD-L1 expression in non-small cell lung cancer (NSCLC) patients was analyzed.

METHODS

We searched PubMed for studies about the relationship between PD-L1 expression and NSCLC patient prognosis. Only studies with patient survival data related to PD-L1 expression in NSCLC patients with different characteristics were included. The effect size (ES) for this analysis was the hazard ratio (HR) with 95% confidence intervals (CI) for overall survival (OS).

RESULTS

Six studies with 1157 patients were included with the defined including and excluding criteria. There is no significant heterogeneity among the studies (I(2) = 0%, p = 0.683). PD-L1 expression was significantly associated with the differentiation of tumor (poor vs. well: OR = 1.91, 95% CI: 1.33-2.75, p = 0.001). High PD-L1 expression was also correlated with poor prognosis in terms of the OS of patients with NSCLC (pooled HR = 1.75, 95% CI: 140-2.20, p < 0.001; heterogeneity test: I(2) = 0%, p = 0.643).

CONCLUSIONS

NSCLC patients with positive PD-L1 expression exhibited poor OS. The PD-L1 expression was higher in tumors with poor differentiation.

Genetic evolution of T-cell resistance in the course of melanoma progression

PURPOSE

CD8(+) T lymphocytes can kill autologous melanoma cells, but their activity is impaired when poorly immunogenic tumor phenotypes evolve in the course of disease progression. Here, we analyzed three consecutive melanoma lesions obtained within one year of developing stage IV disease for their recognition by autologous T cells.

EXPERIMENTAL DESIGN

One skin (Ma-Mel-48a) and two lymph node (Ma-Mel-48b, Ma-Mel-48c) metastases were analyzed for T-cell infiltration. Melanoma cell lines established from the respective lesions were characterized, determining the T-cell-stimulatory capacity, expression of surface molecules involved in T-cell activation, and specific genetic alterations affecting the tumor-T-cell interaction.

RESULTS

Metastases Ma-Mel-48a and Ma-Mel-48b, in contrast with Ma-Mel-48c, were infiltrated by T cells. The T-cell-stimulatory capacity was found to be strong for Ma-Mel-48a, lower for Ma-Mel-48b, and completely abrogated for Ma-Mel-48c cells. The latter proved to be HLA class I-negative due to an inactivating mutation in one allele of the beta-2-microglobulin (B2M) gene and concomitant loss of the other allele by a deletion on chromosome 15q. The same deletion was already present in Ma-Mel-48a and Ma-Mel-48b cells, pointing to an early acquired genetic event predisposing to development of β2m deficiency. Notably, the same chronology of genetic alterations was also observed in a second β2m-deficient melanoma model.

CONCLUSION

Our study reveals a progressive loss in melanoma immunogenicity during the course of metastatic disease. The genetic evolvement of T-cell resistance suggests screening tumors for genetic alterations affecting immunogenicity could be clinically relevant in terms of predicting patient responses to T-cell-based immunotherapy.

Peptide-MHC multimer-based monitoring of CD8 T-cells in HIV-1 infection and AIDS vaccine development

The use of MHC multimers allows precise and direct detecting and analyzing of antigen-specific T-cell populations and provides new opportunities to characterize T-cell responses in humans and animals. MHC-multimers enable us to enumerate specific T-cells targeting to viral, tumor and vaccine antigens with exceptional sensitivity and specificity. In the field of HIV/SIV immunology, this technique provides valuable information about the frequencies of HIV- and SIV-specific CD8(+) cytotoxic T lymphocytes (CTLs) in different tissues and sites of infection, AIDS progression, and pathogenesis. Peptide-MHC multimer technology remains a very sensitive tool in detecting virus-specific T -cells for evaluation of the immunogenicity of vaccines against HIV-1 in preclinical trials. Moreover, it helps to understand how immune responses are formed following vaccination in the dynamics from priming point until T-cell memory is matured. Here we review a diversity of peptide-MHC class I multimer applications for fundamental immunological studies in different aspects of HIV/SIV infection and vaccine development.

Scientific contributions toward successful cancer immunotherapy in The Netherlands

This historical overview shows that immunologists and clinicians from The Netherlands have contributed in a major way to better insights in the nature of cancer immunity. This work involved elucidation of the nature of cancer-associated antigens in autologous and allogeneic settings in addition to understanding of the cellular basis of natural immune responses against cancers and of important immune evasion mechanisms. Insight into such basic immunological mechanisms has contributed to the development of innovating therapies.

Inhibition of mitogen-activated protein kinase pathway can induce upregulation of human leukocyte antigen class I without PD-L1-upregulation in contrast to interferon-γ treatment

Recently, we reported that human leukocyte antigen (HLA) class I expression is predominantly regulated by the mitogen-activated protein kinase (MAPK) pathway as one of the oncogenic regulations of HLA class I expression. In the present study, we examined mechanisms of how HLA class I and PD-L1 are regulated by MAPK inhibitors and interferon-γ (IFN-γ). Furthermore, we evaluated the expression of major signal transduction molecules by Western blot and anti-tumor CTL activity by a cytotoxic assay when HLA class I and PD-L1 were modulated by MAPK inhibitors and/or IFN-γ. As a result, we confirmed, as a more general phenomenon, that the inhibition of MAPK could upregulate HLA class I expression in a panel of human solid tumors (n = 26). Of note, we showed that MAPK inhibitors act on the upregulation of HLA class I expression through a different pathway from IFN-γ; there was an additive effect in the upregulation of HLA class I when treated with the combination of MAPK inhibitors and IFN-γ, and there was no overlapping activation of JAK2/STAT1 and Erk1/2 molecules when treated with either IFN-γ or MAPK inhibitors. Furthermore, we showed that IFN-γ–treatment impaired the tumor-specific CTL activity due to the upregulation of PD-L1 in spite of the upregulation of HLA class I, while MAPK inhibitors can augment the tumor-specific CTL activity due to the upregulated HLA class I without PD-L1 alterations. In conclusion, in addition to the original anti-proliferative activity, MAPK inhibitors may work toward the enhancement of T-cell-mediated anti-tumor immunity through the upregulation of HLA class I without the upregulation of PD-L1.

Blocking tumor escape in hematologic malignancies: the anti-PD-1 strategy

Immunotherapy remains an important tool for treatment of hematologic malignancies. The Programmed Death-1 (PD-1) immune checkpoint pathway has emerged as a mechanism of tumor evasion from the anti-tumor immune response. The recent development of anti-PD-1 monoclonal antibodies has offered a targeted approach to cancer therapy. Several agents are in various stages of development and have shown clinical responses across a broad spectrum of both solid and hematologic malignancies. The use of anti-PD-1 therapy in hematologic malignancies is limited but has demonstrated clinical responses in relapsed/refractory disease following multiple lines of therapy. PD-1 blockade may reduce relapse rates for patients who fail to obtain a complete remission prior to autologous hematopoietic cell transplant. The role of the PD-1 pathway for tumor escape is reviewed. We explore the use of anti-PD-1 therapy in hematologic malignancies. The proposed mechanism of PD-1 blockade as a modulator of the innate and acquired immune response is considered. Finally, the challenges of anti-PD-1 therapy and the future direction of investigation in this area are reviewed.

Attenuation of IFN-γ-induced B7-H1 expression by 15-deoxy-delta(12,14)-prostaglandin J2 via downregulation of the Jak/STAT/IRF-1 signaling pathway

AIM

B7-H1, which belongs to the B7 family of costimulatory molecules, is implicated in the ability of tumors to evade the host immune response. The development of evasion mechanisms within the tumor microenvironment may be responsible for poor therapeutic responses. In this manuscript, we report that the 15-deoxy-δ(12,14)-prostaglandin J2 (15d-PGJ2), peroxisome proliferator-activated receptor gamma (PPARγ) activator leads to the downregulation of the cancer-associated expression of B7-H1 in response to interferon-gamma (IFN-γ) and the associated signaling cascades.

MAIN METHODS

The expression of B7-H1 from IFN-γ-induced B16F10 melanoma cells was measured with flow cytometric analysis. The regulatory mechanisms of 15d-PGJ2 on cellular signaling pathways were examined using Western blot and electrophoretic mobility shift assays.

KEY FINDINGS

The flow cytometric analysis revealed that the B7-H1 costimulatory molecule is significantly upregulated in B16F10 melanoma cells by stimulation with IFN-γ. However, 15d-PGJ2 strongly downregulates B7-H1 expression in IFN-γ-stimulated B16F10 melanoma cells. Furthermore, the significant damping effect of 15d-PGJ2 on B7-H1 expression involves the inhibition of the tyrosine phosphorylation of Janus kinase (Jak) and signal transducer(s) and activator(s) of transcription (STAT) and, thereby, the interferon regulatory factor-1 (IRF-1) trans-activation of STAT. These effects of 15d-PGJ2 were not abrogated by the PPARγ antagonist GW9662, indicating that they occur through a PPARγ-independent mechanism.

SIGNIFICANCE

In this study, we demonstrate that 15d-PGJ2 suppresses the IFN-γ-elicited expression of B7-H1 by the inhibition of IRF-1 transcription via the Jak/STAT signaling pathway through a PPARγ-independent mechanism in mouse melanoma cells.

PD-1 as an emerging therapeutic target in renal cell carcinoma: current evidence

Renal cell carcinoma (RCC) is the most common primary malignant tumor of the kidney in adults, representing approximately 4% of all adult cancers in the United States. Metastatic RCC is poorly responsive to conventional cytotoxic chemotherapies but can be sensitive to T-cell-directed immunotherapies such as interferon-α or interleukin-2. Despite recent progress in the application of antiangiogenic "targeted therapies" for metastatic RCC, high-dose interleukin-2 remains an appropriate first-line therapy for select patients and is associated with durable complete remissions in a small fraction of treated patients. Thus, advanced RCC provides a unique opportunity to investigate the requirements for effective antitumor immunotherapy. Accumulating evidence suggests that resistance mechanisms exploited by RCC and other tumor types may play a dominant role in limiting the effectiveness of tumor-reactive adaptive immune responses. Expression of the inhibitory coreceptor programmed cell death-1 (PD-1) on tumor-infiltrating lymphocytes within RCC tumors, as well as the expression of the PD-1 ligand (PD-L1) on RCC tumor cells, are strong negative prognostic markers for disease-specific death in RCC patients. Monoclonal antibodies targeting either PD-1 or PD-L1 have now entered clinic trials and have demonstrated promising antitumor effects for refractory metastatic RCC. This review summarizes the results of published and reported studies of PD-1- and PD-L1-targeted therapies enrolling patients with advanced RCC, focusing on key safety, toxicity, and efficacy end points. Prospects for advanced phase clinical testing and novel therapy combinations with PD-1- and PD-L1-targeted agents are discussed.

Synergistic effects of IL-4 and TNFα on the induction of B7-H1 in renal cell carcinoma cells inhibiting allogeneic T cell proliferation

Background

The importance of B7-H molecules for the T cell/tumor communication and its impact on renal cell carcinoma (RCC) progression and prognosis has been recently described. Cytokine treatment of RCC has earlier been shown to be beneficial in preclinical settings, but its clinical implementation has not proven to be as effective. This might be partially explained by the yet incomplete picture of cellular alterations in tumor cells upon cytokine treatment investigated in detail in this study.

Methods

RCC tumor cell lines were treated with different cytokines alone or in combination. The constitutive and/or cytokine-induced expression of cytokine receptors signaling components and B7-H molecules in RCC cells were analysed by qPCR and flow cytometry. A mcherry reporter gene construct containing B7-H1 promoter was cloned and its activity was determined upon transfection in cytokine-stimulated cells. Cytokine pretreated tumor cells were co-cultured with allogeneic CD8⁺ T cells from healthy donors and T cell proliferation as well as cytokine secretion was determined.

Results

A heterogeneous, but constitutive B7-H1,-H2,-H3 and H4 expression was found on human RCC cell lines. IL-4 and TNFα treatment led to strong synergistic induction of B7-H1 in RCC cells, whereas B7-H2 was only increased by TNFα. In contrast, B7-H3 and B7-H4 expression were not altered by these cytokines. Treatment of RCC cells with TNFα and IL-4 was accompanied by an activation of signaling molecules like NF-κB, IκB and STAT6. The cytokine-mediated up-regulation of B7-H1 was due to transcriptional control as determined by an increased B7-H1 promoter activity in the presence of IL-4 and TNFα. Despite HLA class I and LFA-1 were also increased, the cytokine-mediated up-regulation of B7-H1 was more pronounced and caused an inhibition of allospecifc CD8⁺ T cell proliferation.

Conclusion

Thus, IL-4 and TNFα, which could be released by immune cells of the tumor microenvironment, are able to control the B7-H1 expression in RCC thereby altering T cell responses. These data are of importance for understanding the complex interplay of tumor cells with immune cells orchestrated by a number of different soluble and membrane bound mediators and for the implementation of check point antibodies directed against B7-H1.

In vitro characterization of the anti-PD-1 antibody nivolumab, BMS-936558, and in vivo toxicology in non-human primates

The programmed death-1 (PD-1) receptor serves as an immunologic checkpoint, limiting bystander tissue damage and preventing the development of autoimmunity during inflammatory responses. PD-1 is expressed by activated T cells and downmodulates T-cell effector functions upon binding to its ligands, PD-L1 and PD-L2, on antigen-presenting cells. In patients with cancer, the expression of PD-1 on tumor-infiltrating lymphocytes and its interaction with the ligands on tumor and immune cells in the tumor microenvironment undermine antitumor immunity and support its rationale for PD-1 blockade in cancer immunotherapy. This report details the development and characterization of nivolumab, a fully human IgG4 (S228P) anti-PD-1 receptor-blocking monoclonal antibody. Nivolumab binds to PD-1 with high affinity and specificity, and effectively inhibits the interaction between PD-1 and its ligands. In vitro assays demonstrated the ability of nivolumab to potently enhance T-cell responses and cytokine production in the mixed lymphocyte reaction and superantigen or cytomegalovirus stimulation assays. No in vitro antibody-dependent cell-mediated or complement-dependent cytotoxicity was observed with the use of nivolumab and activated T cells as targets. Nivolumab treatment did not induce adverse immune-related events when given to cynomolgus macaques at high concentrations, independent of circulating anti-nivolumab antibodies where observed. These data provide a comprehensive preclinical characterization of nivolumab, for which antitumor activity and safety have been demonstrated in human clinical trials in various solid tumors.

Response to BRAF inhibition in melanoma is enhanced when combined with immune checkpoint blockade

BRAF-targeted therapy results in objective responses in the majority of patients; however, the responses are short lived (∼6 months). In contrast, treatment with immune checkpoint inhibitors results in a lower response rate, but the responses tend to be more durable. BRAF inhibition results in a more favorable tumor microenvironment in patients, with an increase in CD8(+) T-cell infiltrate and a decrease in immunosuppressive cytokines. There is also increased expression of the immunomodulatory molecule PDL1, which may contribute to the resistance. On the basis of these findings, we hypothesized that BRAF-targeted therapy may synergize with the PD1 pathway blockade to enhance antitumor immunity. To test this hypothesis, we developed a BRAF(V600E)/Pten(-/-) syngeneic tumor graft immunocompetent mouse model in which BRAF inhibition leads to a significant increase in the intratumoral CD8(+) T-cell density and cytokine production, similar to the effects of BRAF inhibition in patients. In this model, CD8(+) T cells were found to play a critical role in the therapeutic effect of BRAF inhibition. Administration of anti-PD1 or anti-PDL1 together with a BRAF inhibitor led to an enhanced response, significantly prolonging survival and slowing tumor growth, as well as significantly increasing the number and activity of tumor-infiltrating lymphocytes. These results demonstrate synergy between combined BRAF-targeted therapy and immune checkpoint blockade. Although clinical trials combining these two strategies are ongoing, important questions still remain unanswered. Further studies using this new melanoma mouse model may provide therapeutic insights, including optimal timing and sequence of therapy.

Unmet needs in squamous cell carcinoma of the lung: potential role for immunotherapy

Squamous cell carcinoma of the lung accounts for 20–30 % of non-small cell lung cancers (NSCLC). Despite the differences in disease characteristics between squamous and non-squamous NSCLC, both have historically been treated similarly in the clinic. Recently approved drugs have revealed differences in activity and safety profiles across histologic subtypes and have applicability in treating non-squamous, but not typically squamous, NSCLC. Exploration of immune checkpoints—co-inhibitory molecules used to regulate immune responses—has resulted in novel immunotherapies designed to interrupt signaling through the cytotoxic T lymphocyte-associated antigen-4 or programmed cell death protein-1 pathways on lymphocytes. Modulation of these pathways can lead to restored antitumor immune responses, and preliminary evidence shows that agents targeting these pathways have activity in lung cancer, including squamous NSCLC.

Immunologic and clinical effects of targeting PD-1 in lung cancer

Therapeutic antibodies that block the programmed cell death protein-1 (PD-1) immune checkpoint pathway prevent T-cell downregulation and promote immune responses against cancer. Several PD-1 pathway inhibitors have shown robust activity in initial trials. This article reviews the preclinical evidence, rationale, and clinical pharmacology of blockade of PD-1 or its ligands as therapy for lung cancer and provides an overview of agents in development, clinical evidence to date, and implications for clinical application.

HTLV-1 specific CD8+ T cell function augmented by blockade of 2B4/CD48 interaction in HTLV-1 infection

CD8+ T cell response is important in the response to viral infections; this response though is regulated by inhibitory receptors. Expression of inhibitory receptors has been positively correlated with CD8+ T cell exhaustion; the consequent effect of simultaneous blockade of these inhibitory receptors on CD8+ T cell response in viral infections have been studied, however, the role of individual blockade of receptor-ligand pair is unclear. 2B4/CD48 interaction is involved in CD8+T cell regulation, its signal transducer SAP (signaling lymphocyte activation molecule (SLAM)-associated protein) is required for stimulatory function of 2B4/CD244 on lymphocytes hence, we analyzed 2B4/CD244 (natural killer cell receptor) and SAP (signaling lymphocyte activation molecule(SLAM)-associated protein) on total CD8+ and HTLV-1 specific CD8+T cells in HTLV-1 infection and the effect of blockade of interaction with ligand CD48 on HTLV-1 specific CD8+ T cell function. We observed a high expression of 2B4/CD244 on CD8+ T cells relative to uninfected and further upregulation on HTLV-1 specific CD8+ T cells. 2B4+ CD8+ T cells exhibited more of an effector and terminally differentiated memory phenotype. Blockade of 2B4/CD48 interaction resulted in improvement in function via perforin expression and degranulation as measured by CD107a surface mobilization on HTLV-1 specific CD8+ T cells. In the light of these findings, we thus propose an inhibitory role for 2B4/CD48 interaction on CD8+T cell function.

B7-H abnormalities in melanoma and clinical relevance

Melanoma have been shown to escape immune surveillance by different mechanisms such as loss of HLA class I antigens, upregulation of nonclassical HLA-G antigen and Fas, increased secretion of immune suppressive cytokines and metabolites as well as altered expression of co-stimulatory and coinhibitory signals. Recently, an important role of B7-H1 and B7-H4 in the immune escape of melanoma has been described. High mRNA and/or protein expression levels of these coinhibitory molecules were detected in both melanoma cell lines and melanoma lesions when compared to melanocytes. However, their clinical relevance is currently controversially discussed regarding a correlation of B7-H family members with tumor grading and staging as well as survival of patients in melanoma.

Tumor infiltrating PD1-positive lymphocytes and the expression of PD-L1 predict poor prognosis of soft tissue sarcomas

Recently, the possibility of PD1 pathway-targeted therapy has been extensively studied in various human malignant tumors. However, no previous study has investigated their potential application for soft-tissue sarcomas (STS). In this study, we evaluated the clinical impact of intra-tumoral infiltration of PD1-positive lymphocytes and PD-L1 expression in tumor cells in 105 cases of STS. Intra-tumoral infiltration of PD1-positive lymphocytes and PD-L1 expression were seen in 65% and 58% of STS, respectively. Both PD1-positivity and PD-L1 expression were significantly associated with advanced clinicopathological parameters such as higher clinical stage, presence of distant metastasis, higher histological grade, poor differentiation of tumor, and tumor necrosis. Moreover, both PD1-positivity and PD-L1 positivity were independent prognostic indicators of overall survival (OS) and event-free survival (EFS) of STS by multivariate analysis. In addition, the combined pattern of PD1- and PD-L1-positivity was also an independent prognostic indicator for OS and EFS by multivariate analysis. The patents with a PD1(+)/PD-L1(+) pattern had the shortest survival time. In conclusion, this study is the first to demonstrate that the infiltration of PD1 positive lymphocytes and PD-L1 expression in STS cells could be used as novel prognostic indicators for STS. Moreover, the evaluation of PD1- and PD-L1-positivity in STS is also available as possible criteria for selection of patients suitable for PD1-based immunotherapy.

Interferon-induced programmed death-ligand 1 (PD-L1/B7-H1) expression increases on human acute myeloid leukemia blast cells during treatment

INTRODUCTION

While current treatment for acute myeloid leukemia is characterized by high response rates, patients' long-term outcome is still disappointing, due to frequent relapse and ineligibility of the often elderly patients for stem cell transplantation approaches. Considerable efforts have, thus, been made to incorporate immunotherapeutic approaches in the acute myeloid leukemia (AML) consolidation, with so far disappointing clinical benefit. The B7 family ligand programmed-death receptor-ligand 1 (PD-L1, B7-H1, CD274) has been recently described (with conflicting results) to be expressed on AML blast cells, and interaction with its receptor on T cells, programmed death receptor-1 (PD-1, CD279), has been shown to suppress T-cell functions and to allow survival of dormant AML cells in animal models.

DESIGN AND METHODS

In this work, we analyzed freshly isolated myeloid precursor cells from healthy donors and from AML patients for PD-L1 expression with or without interferon-γ exposure at different time points during their treatment.

RESULTS

While without IFN exposure, only minor differences were observed, we found IFN-γ-induced PD-L1 expression most prominent after initial treatment and independent of treatment outcome.

CONCLUSIONS

Our observations support the recently suggested PD-L1-mediated adaptive immune resistance and argue for a targeting of the PD-L1/PD-1 pathway during the consolidation phase of AML treatment.

Strategies to reverse melanoma-induced T-cell dysfunction

Patients with advanced melanoma can develop spontaneous cellular and humoral responses to tumor antigens. Understanding the failure of spontaneous or vaccine-induced tumor antigen-specific T-cell responses to promote the immunologic clearance of melanomas is critical. Multiple mechanisms of melanoma-induced immune escape, which are likely to cause the failure of the spontaneous or vaccine-induced immune responses to promote tumor regression in humans, have been elucidated. In addition, a number of negative factors in the tumor microenvironment dampen antitumor immune responses, including cytokines (like transforming growth factor-β or interleukin-10), suppressive cells (regulatory T cells and myelosuppressive dendritic cells), defective antigen presentation by tumor cells (human leukocyte antigen or T antigen expression loss, antigen processing machinery defects), amino acid catabolizing enzymes (indoleamine-2-3 dioxygenase, arginase), and immune inhibitory pathways (like cytotoxic T-lymphocyte antigen 4/cluster of differentiation 28, programmed death 1/programmed death 1 ligand 1). This information has been used to develop a number of therapies to specifically target these negative regulators of antimelanoma immune responses to enhance tumor antigen-specific immune responses and to increase the likelihood of clinical benefits in patients with advanced melanoma.

Clonal expansion of renal cell carcinoma-infiltrating T lymphocytes

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

Rational combinations of immunotherapeutics that target discrete pathways

An effective anti-tumor immune response requires the coordinated action of the innate and adaptive phases of the immune system. Critical processes include the activation of dendritic cells to present antigens, produce cytokines including type I interferons, and express multiple costimulatory ligands; induction of a productive T cell response within lymph nodes; migration of activated T cells to the tumor microenvironment in response to chemokines and homing receptor expression; and having effector T cells gain access to antigen-expressing tumor cells and maintain sufficient functionality to destroy them. However, tumors can become adept at escaping the immune response, developing multiple mechanisms to disrupt key processes. In general, tumors can be assigned into two different, major groups depending on whether the tumor there is an 'inflamed' or 'non-inflamed' tumor microenvironment. Improvements in our understanding of the interactions between the immune system and cancer have resulted in the development of various strategies to improve the immune-mediated control of tumors in both sub-groups. Categories of major immunotherapeutic intervention include methods to increase the frequency of tumor antigen-specific effector T cells in the circulation, strategies to block or uncouple a range of immune suppressive mechanisms within the tumor microenvironment, and tactics to induce de novo immune inflammation within the tumor microenvironment. The latter may be particularly important for eliciting immune recognition of non-inflamed tumor phenotypes. The premise put forth in this review is that synergistic therapeutic effects in vivo may be derived from combination therapies taken from distinct "bins" based on these mechanisms of action. Early data in both preclinical and some clinical studies provide support for this model. We also suggest that optimal application of these combinations may be aided by appropriate patient selection based on predictive biomarkers.

PD-1 blockage delays murine squamous cell carcinoma development

Engagement of programmed death-1 (PD-1) with its two ligands [programmed death ligand-1 (PD-L1) and PD-L2] has been associated with the suppression of tumor-reactive T cells; however, the underlying mechanism for this T-cell dysfunction is not clear. We hypothesized that PD-1 and PD-L1 signals are, in part, responsible for squamous cell carcinoma (SCC) escape from immune antitumor regulation by modulation of the tumor environment. In the present study, we used a multistage model of SCC to examine the role of PD-1/PD-L1 activation during tumor development. Tumor sites presented an increased percentage of CD4(+) and CD8(+) T cells expressing PD-1 when compared with non-tumorigenic control mice, whereas the expression of PD-L1 was particularly increased in F4/80(+) macrophages in tumor sites. Further, the systemic immune neutralization of PD-1 resulted in a decreased number and delayed incidence rate of papillomas followed by a differential expression of cytokeratins, suggesting that the PD-1-PD-L1 interaction contributes to the progression of SCC by downregulation of antitumor responses. In fact, blocking PD-1 increased the percentage of CD8(+) and CD4(+) T cells, and the levels of interferon-γ in the tumor sites. Our results indicated involvement of PD-1(+) T cells in SCC development and in the modulation of the inflammatory immune response.

B7-H1 protein vaccine induces protective and therapeutic antitumor responses in SP2/0 myeloma-bearing mice

B7-H1 is a co-inhibitory molecule belonging to the B7 family. The B7-H1 protein is only expressed on macrophage lineage of cells in normal tissues, but is overexpressed in most types of tumor. The aberrant expression of cell surface B7-H1 on cancer cells is generally associated with high-risk prognostic factors. The tumor-associated B7-H1 increases apoptosis of antigen-specific T cells through interaction with its receptor PD-1 on CD8+ T cells and contributes to tumor immune evasion. These features suggest that B7-H1 may be a therapeutic target for the B7-H1-expressing tumors. We developed a therapeutic vaccine by coupling a tetanus toxoid T-helper cell epitope with the N-terminal of B7-H1 IgV-like domain. This vaccine was able to induce high titers of antibodies against B7-H1 in mice which were able to bind to native cell surface B7-H1. We chose the B7-H1-expressing SP2/0 myeloma and its syngeneic host (the BALB/c mouse) as the model to study the antitumor activity of the rhB7-H1M vaccine. Vaccination with this modified B7-H1 protein resulted in almost complete protection from SP2/0 tumor challenge and efficiently eliminated pre-established tumors in mice. In addition, B7-H1 vaccination was able to decrease the percentage of CD4+ Foxp3+ regulatory T cells in tumor-bearing mice and which might improve antitumor immunity. These data demonstrate the potential of B7-H1-based vaccine as a therapeutic agent for the treatment of cancer overexpressing B7-H1.

Immune alterations in malignant melanoma and current immunotherapy concepts

INTRODUCTION

Malignant melanoma is a highly aggressive, immunogenic tumor that has the ability to modulate the immune system to its own advantage. Patients with melanoma present numerous cellular immune defects and cytokine abnormalities, all leading to suppression of the host anti-tumor immune response. Innovative treatment strategies can be achieved through employing our knowledge of the melanoma-induced immune alterations.

AREAS COVERED

The authors review comprehensively the immune abnormalities in individuals with melanoma, and provide a summary of currently available melanoma immunotherapy agents that are currently on the market or undergoing clinical trials.

EXPERT OPINION

Ipilimumab, a monoclonal antibody directed against the CTLA-4, is one of the current forefront treatment strategies in malignant melanoma. Novel immunomodulating agents have shown clear activity in patients with malignant melanoma. These include anti-PD-1 and anti-PD-1 ligand antibodies that may soon become important items in the anti-melanoma armamentarium. Combinations of different immunotherapy agents, between themselves or with other agents, are currently being studied in an attempt to further enhance the antineoplastic effect in patients with malignant melanoma.

Soluble CD80 restores T cell activation and overcomes tumor cell programmed death ligand 1-mediated immune suppression

Many tumor cells escape anti-tumor immunity through their expression of programmed death ligand-1 (PDL1 or B7-H1), which interacts with T cell-expressed PD1 and results in T cell apoptosis. We previously reported that transfection of human tumor cells with a membrane-bound form of the human costimulatory molecule CD80 prevented PD1 binding and restored T cell activation. We now report that a membrane-bound form of murine CD80 similarly reduces PDL1-PD1-mediated suppression by mouse tumor cells and that a soluble protein consisting of the extracellular domains of human or mouse CD80 fused to the Fc domain of IgG1 (CD80-Fc) overcomes PDL1-mediated suppression by human and mouse tumor cells, respectively. T cell activation experiments with human and mouse tumor cells indicate that CD80-Fc facilitates T cell activation by binding to PDL1 to inhibit PDL1-PD1 interactions and by costimulating through CD28. CD80-Fc is more effective in preventing PD1-PDL1-mediated suppression and restoring T cell activation compared with treatment with mAb to either PD1 or PDL1. These studies identify CD80-Fc as an alternative and potentially more efficacious therapeutic agent for overcoming PDL1-induced immune suppression and facilitating tumor-specific immunity.

PD-1 as a potential target in cancer therapy

Recently, an improved understanding of the molecular mechanisms governing the host response to tumors has led to the identification of checkpoint signaling pathways involved in limiting the anticancer immune response. One of the most critical checkpoint pathways responsible for mediating tumor-induced immune suppression is the programmed death-1 (PD-1) pathway, normally involved in promoting tolerance and preventing tissue damage in settings of chronic inflammation. Many human solid tumors express PD ligand 1 (PD-L1), and this is often associated with a worse prognosis. Tumor-infiltrating lymphocytes from patients with cancer typically express PD-1 and have impaired antitumor functionality. Proof-of-concept has come from several preclinical studies in which blockade of PD-1 or PD-L1 enhanced T-cell function and tumor cell lysis. Three monoclonal antibodies against PD-1, and one against PD-L1, have reported phase 1 data. All four agents have shown encouraging preliminary activity, and those that have been evaluated in larger patient populations appear to have encouraging safety profiles. Additional data are eagerly awaited. This review summarizes emerging clinical data and potential of PD-1 pathway–targeted antibodies in development. If subsequent investigations confirm the initial results, it is conceivable that agents blocking the PD-1/PD-L1 pathway will prove valuable additions to the growing armamentarium of targeted immunotherapeutic agents.

Next-generation immunotherapy agents that target the PD-1 checkpoint pathway are demonstrating antitumor activity and encouraging safety profiles in early clinical trials. Current and future clinical trials will provide new insights, and the evaluation of biomarkers and rational combination therapies is ongoing.

Tumor-specific T cells in human Merkel cell carcinomas: a possible role for Tregs and T-cell exhaustion in reducing T-cell responses

Merkel cell carcinomas (MCCs) are rare but highly malignant skin cancers associated with a recently described polyomavirus. MCC tumors were infiltrated by T cells, including effector, central memory, and regulatory T cells. Infiltrating T cells showed markedly reduced activation as evidenced by reduced expression of CD69 and CD25. Treatment of MCC tumors in vitro with IL-2 and IL-15 led to T-cell activation, proliferation, enhanced cytokine production, and loss of viable tumor cells from cultures. Expanded tumor-infiltrating lymphocytes showed TCR repertoire skewing and upregulation of CD137. MCC tumors implanted into immunodeficient mice failed to grow unless human T cells in the tumor grafts were depleted with denileukin diftitox, suggesting that tumor-specific T cells capable of controlling tumor growth were present in MCC. Both CD4(+) and CD8(+) FOXP3(+) regulatory T cells were frequent in MCC. Fifty percent of nonactivated T cells in MCC-expressed PD-1, a marker of T-cell exhaustion, and PD-L1 and PD-L2 were expressed by a subset of tumor dendritic cells and macrophages. In summary, we observed tumor-specific T cells with suppressed activity in MCC tumors. Agents that stimulate T-cell activity, block regulatory T cell function, or inhibit PD-1 signaling may be effective in the treatment of this highly malignant skin cancer.