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

Delivery technologies for cancer immunotherapy

Immunotherapy has become a powerful clinical strategy for treating cancer. The number of immunotherapy drug approvals has been increasing, with numerous treatments in clinical and preclinical development. However, a key challenge in the broad implementation of immunotherapies for cancer remains the controlled modulation of the immune system, as these therapeutics have serious adverse effects including autoimmunity and nonspecific inflammation. Understanding how to increase the response rates to various classes of immunotherapy is key to improving efficacy and controlling these adverse effects. Advanced biomaterials and drug delivery systems, such as nanoparticles and the use of T cells to deliver therapies, could effectively harness immunotherapies and improve their potency while reducing toxic side effects. Here, we discuss these research advances, as well as the opportunities and challenges for integrating delivery technologies into cancer immunotherapy, and we critically analyse the outlook for these emerging areas.

CTLA-4 antibody ipilimumab negatively affects CD4+ T-cell responses in vitro

Immune checkpoint inhibitors targeting coinhibitory pathways in T cells possess efficacy in combating cancer. In addition to PD-1/PD-L1 and CTLA-4 antibodies which are already established in tumor immunotherapy, immune checkpoints such as LAG-3 or BTLA are emerging, which may have the potential to enhance T-cell responses alone or in combination with PD-1 blockers. CD4⁺ T cells play a central role in the immune system and contribute to productive immune responses in multiple ways. The effects of immune checkpoint inhibitors on this cell subset may thus critically influence therapeutic outcomes. Here, we have used in vitro responses to tetanus toxoid (TT) as a model system to study the effects of immune checkpoint inhibitors on CD4⁺ T-cell responses. CFSE-labeled PBMCs of 65 donors were stimulated with TT in the presence of blocking antibodies to PD-L1, CTLA-4, LAG-3, or BTLA for 7 days. We found that the PD-L1 antibody greatly enhanced cytokine production and antigen-specific CD4⁺ T-cell proliferation, whereas blocking antibodies to BTLA or LAG-3 did not augment responses to TT. Surprisingly, the presence of the therapeutic CTLA-4 antibody ipilimumab resulted in a significant reduction of CD4⁺ T-cell proliferation and cytokine production. Stimulation experiments with an IgG4 variant of ipilimumab indicated that the inhibitory effect of ipilimumab was dependent on its IgG1 isotype. Our results indicate that the therapeutic CTLA-4 antibody ipilimumab can impair CD4⁺ effector T-cell responses and that this activity is mediated by its Fc part and CD16-expressing cells.

OCT4&SOX2-specific cytotoxic T lymphocytes plus programmed cell death protein 1 inhibitor presented with synergistic effect on killing lung cancer stem-like cells in vitro and treating drug-resistant lung cancer mice in vivo

This study aimed to investigate the synergistic effect of octamer-binding transcription factor 4 and sex determining region Y-box 2 (OCT4&SOX2)-specific cytotoxic T lymphocytes (CTLs) and programmed cell death protein 1 (PD-1) inhibitor on killing lung cancer stem-like cells (LCSCs) and their efficacy in treating drug-resistant lung cancer (DRLC) mice. OCT4&SOX2-specific CTLs and PD-1 inhibitor with differed doses were applied to treat PC9 cells and PC9 LCSCs. Cell counting kit-8 (CCK8) assay and flow cytometry (FCM) assay with carboxyfluorescein diacetate/succinimidyl ester staining target cells before treatment and propidium iodide (PI) staining dead cells after treatment were conducted to detect the cytotoxic activity. DRLC mice were constructed by injection of PC9 LCSCs suspension and Matrigel into left lung of SD mice. DRLC mice were randomly divided into five groups: control group, cytomegalovirus (CMV) pp65 CTLs group, OCT4&SOX2 CTLs group, PD-1 inhibitor group, and OCT4&SOX2 CTLs + PD-1 inhibitor group. In vitro, both CCK8 assay and FCM assay disclosed that OCT4&SOX2-specific CTLs plus PD-1 inhibitor presented with elevated cytotoxic activity on PC9 cells and PC9 LCSCs. In vivo, tumor volume and tumor weight were decreased, while tumor necrosis and tumor apoptosis were increased in OCT4&SOX2 CTLs group than CMV pp65 CTLs group and control group, and in OCT4&SOX2 CTLs + PD-1 inhibitor group than OCT4&SOX2 CTLs group and PD-1 inhibitor group. In addition, CD8 expression was increased while OCT4&SOX2 expressions were decreased in OCT4&SOX2 CTLs + PD-1 inhibitor group than OCT4&SOX2 CTLs group and PD-1 inhibitor group. In conclusion, OCT4&SOX2-specific CTLs and PD-1 inhibitor presented with the synergistic effect on killing LCSCs in vitro and treating DRLC mice in vivo.

Inhibitory Receptors and Pathways of Lymphocytes: The Role of PD-1 in Treg Development and Their Involvement in Autoimmunity Onset and Cancer Progression

Regulatory T (Treg) cells represent a subpopulation of suppressor CD4⁺ T cells critically involved in the establishment of peripheral tolerance through the inhibition of effector T (Teff) cells and the suppression of the immune-mediated tissue destruction toward self-antigens. Treg generation, their suppressive properties and also Treg-Teff cell interactions could be modulated at least in part by programmed cell death-1 (PD-1) expression on their surface and through binding between PD-1 and programmed cell death ligand-1 (PD-L1). Defects involving PD-1 and Tregs can lead to the development of pathological conditions, including autoimmune disorders or promote cancer progression by favoring tumor evasion from the host immune response. At the same time, PD-1 and Tregs could represent attractive targets for treatment, as demonstrated by the therapeutic blockade of PD-L1 applied for the management of different cancer conditions in humans. In the present Review, we focus specifically the role of PD-1/PD-L1 on Treg development and activity.

The intracellular signalosome of PD-L1 in cancer cells

Programmed cell death-1 ligand-1 (PD-L1) overexpression in cancer cells accelerates tumor progression. PD-L1 possesses two main pro-oncogenic functions. First, PD-L1 is a strong immunosuppressive molecule that inactivates tumor-specific T cells by binding to the inhibitory receptor PD-1. Second, PD-L1 function relies on the delivery of intrinsic intracellular signals that enhance cancer cell survival, regulate stress responses and confer resistance toward pro-apoptotic stimuli, such as interferons. Here, we review the current knowledge on intracellular signal transduction pathways regulated by PD-L1, describe its associated signalosome and discuss potential combinations of targeted therapies against the signalosome with PD-L1/PD-1 blockade therapies.

Intratumoral Delivery of an Adenoviral Vector Carrying the SOCS-1 Gene Enhances T-Cell-Mediated Antitumor Immunity By Suppressing PD-L1

Ovarian cancer is the leading cause of gynecologic cancer-related deaths and novel therapeutic strategies are required. Programmed cell death 1 and programmed cell death ligand 1 (PD-L1), which are key mediators of host immune tolerance, are associated with ovarian cancer progression. Recent evidence indicates the importance of IFNγ-induced PD-L1 for immune tolerance in ovarian cancer. This study aimed to reveal the therapeutic potential of suppressor of cytokine signaling 1 (SOCS-1), an endogenous inhibitor of the Janus kinase (JAK)-STAT signaling pathway, for the treatment of ovarian cancer. IHC assessment revealed that patients with ovarian cancer with high intratumoral STAT1 activation exhibited poor prognosis compared with patients with low STAT1 activation (P < 0.05). Stimulation of OVISE, OVTOKO, OV2944-HM-1 (HM-1), and CT26 cell lines with IFNγ induced STAT1 phosphorylation and PD-L1 expression. Adenovirus-mediated SOCS-1 gene delivery (AdSOCS-1) in HM-1 and CT26 cells in vitro potently inhibited IFNγ-induced STAT1 phosphorylation and PD-L1 upregulation, similar to the addition of JAK inhibitor I, but failed to inhibit their proliferation. Notably, intratumoral injection of AdSOCS-1, but not AdLacZ, significantly inhibited the tumor growth of HM-1 and CT26 cells subcutaneously transplanted in immunocompetent syngeneic mice. AdSOCS-1 reduced PD-L1 expression on tumors and restored the activation of tumor-infiltrating CD8⁺ T cells. Moreover, the antitumor effect of AdSOCS-1 was significantly attenuated by PD-L1 Fc-fusion protein administration in vivo, suggesting that the effect of AdSOCS-1 is mainly attributable to enhancement of tumor immunity. This study highlights the potential clinical utility of SOCS-1 as an immune checkpoint inhibitor. Mol Cancer Ther; 17(9); 1941-50. ©2018 AACR.

An evaluation of nivolumab for the treatment of metastatic renal cell carcinoma

INTRODUCTION

The treatment paradigm for metastatic renal cell carcinoma (mRCC) has undergone a revolution with the rapid market approval of multiple agents over a three-year period. The immunogenicity of renal cell carcinoma (RCC) provided the biological rationale to assess the clinical efficacy of nivolumab, an immune checkpoint inhibitor. Nivolumab is approved for second-line treatment after failure of angiogenesis-targeted therapy and in combination therapy with ipilimumab for previously untreated intermediate- or poor-risk advanced RCC. Areas covered: The authors review the preclinical and clinical data supporting nivolumab employment in mRCC. Discussion of the underlying mechanisms of immunotherapy, data on objective responses, safety and tolerability, regulatory affairs, and future directions of nivolumab therapy are highlighted. Expert opinion: Nivolumab serves as a proof-of-principle of the efficacy of immunotherapy with checkpoint inhibition in mRCC. Nivolumab may be considered the leading monotherapy in the second-line setting for patients with low tumor volume considering its risks and benefits. Nivolumab was recently approved in the first-line setting as part of combination therapy with another immune modulator. Moreover, nivolumab use may offer clinicians the option for treatment beyond progression as emerging data has indicated possible overall survival benefits in this setting. Ongoing clinical studies may result in nivolumab use in the first-line setting, as monotherapy or in combination therapy with antiangiogenesis agents.

Self-Delivering RNAi Targeting PD-1 Improves Tumor-Specific T Cell Functionality for Adoptive Cell Therapy of Malignant Melanoma

Adoptive cell therapy (ACT) is becoming a prominent alternative therapeutic treatment for cancer patients relapsing on traditional therapies. In parallel, antibodies targeting immune checkpoint molecules, such as cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4) and cell death protein 1 pathway (PD-1), are rapidly being approved for multiple cancer types, including as first line therapy for PD-L1-expressing non-small-cell lung cancer. The combination of ACT and checkpoint blockade could substantially boost the efficacy of ACT. In this study, we generated a novel self-delivering small interfering RNA (siRNA) (sdRNA) that knocked down PD-1 expression on healthy donor T cells as well as patient-derived tumor-infiltrating lymphocytes (TIL). We have developed an alternative chemical modification of RNA backbone for improved stability and increased efficacy. Our results show that T cells treated with sdRNA specific for PD-1 had increased interferon γ (IFN-γ) secreting capacity and that this modality of gene expression interference could be utilized in our rapid expansion protocol for production of TIL for therapy. TIL expanded in the presence of PD-1-specific sdRNA performed with increased functionality against autologous tumor as compared to control TIL. This method of introducing RNAi into T cells to modify the expression of proteins could easily be adopted into any ACT protocol and will lead to the exploration of new combination therapies.

Genetic abrogation of immune checkpoints in antigen-specific cytotoxic T-lymphocyte as a potential alternative to blockade immunotherapy

T cell function can be compromised during chronic infections or through continuous exposure to tumor antigens by the action of immune checkpoint receptors, such as programmed cell death protein 1 (PD-1). Systemic administration of blocking antibodies against the PD-1 pathway can restore T cell function, and has been approved for the treatment of several malignancies, although there is a risk of adverse immune-related side-effects. We have developed a method for generating gene knockouts in human antigen (Ag)-specific cytotoxic T-Lymphocyte (CTLs) using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) genome editing. Using this method, we generated several transduced CD4⁺ or CD8⁺ antigen-specific polyclonal CTL lines and clones, and validated gene modifications of the PD-1 gene. We compared these T-cell lines and clones with control groups in the presence of programmed death-ligand 1 (PD-L1) and observed improved effector functions in the PD1-disrupted cell group. Overall, we have developed a versatile tool for functional genomics in human antigen-specific CTL studies. Furthermore, we provide an alternative strategy for current cell-based immunotherapy that will minimize the side effects caused by antibody blockade therapy.

Cytosolic high-mobility group box protein 1 (HMGB1) and/or PD-1+ TILs in the tumor microenvironment may be contributing prognostic biomarkers for patients with locally advanced rectal cancer who have undergone neoadjuvant chemoradiotherapy

Rectal cancer, which comprises 30% of all colorectal cancer cases, is one of the most common forms of cancer in the world. Patients with locally advanced rectal cancer (LARC) are often treated with neoadjuvant chemoradiotherapy (neoCRT) followed by surgery. However, after neoCRT treatment, approximately one-third of the patients progress to local recurrence or distant metastasis. In these studies, we found that patients with tumors that exhibited cytosolic HMGB1(Cyto-HMGB1) translocation and/or the presence of PD-1+ tumor-infiltrating lymphocytes (TILs) before treatment had a better clinical outcome. The better outcome is likely due to the release of HMGB1, which triggers the maturation of dendritic cells (DCs) via TLR4 activation, and the subsequent recruitment of PD-1+ tumor-infiltrating lymphocytes to the tumor site, where they participate in immune-scavenging. In conclusion, our results provide evidence that cyto-HMGB1 and/or PD-1+TIL are not only predictive biomarkers before treatment, but they can also potentially designate patients for personalized oncological management including immunotherapy.

Targeting LAG-3 and PD-1 to Enhance T Cell Activation by Antigen-Presenting Cells

Immune checkpoint inhibition has been shown to successfully reactivate endogenous T cell responses directed against tumor-associated antigens, resulting in significantly prolonged overall survival in patients with various tumor entities. For malignancies with low endogenous immune responses, this approach has not shown a clear clinical benefit so far. Therapeutic vaccination, particularly dendritic cell (DC) vaccination, is a strategy to induce T cell responses. Interaction of DCs and T cells is dependent on receptor-ligand interactions of various immune checkpoints. In this study, we analyzed the influence of blocking antibodies targeting programmed cell death protein 1 (PD-1), HVEM, CD244, TIM-3, and lymphocyte activation gene 3 (LAG-3) on the proliferation and cytokine secretion of T cells after stimulation with autologous TLR-matured DCs. In this context, we found that LAG-3 blockade resulted in superior T cell activation compared to inhibition of other pathways, including PD-1/PD-L1. This result was consistent across different methods to measure T cell stimulation (proliferation, IFN-γ secretion), various stimulatory antigens (viral and bacterial peptide pool, specific viral antigen, specific tumor antigen), and seen for both CD4⁺ and CD8⁺ T cells. Only under conditions with a weak antigenic stimulus, particularly when combining antigen presentation by peripheral blood mononuclear cells with low concentrations of peptides, we observed the highest T cell stimulation with dual blockade of LAG-3 and PD-1 blockade. We conclude that priming of novel immune responses can be strongly enhanced by blockade of LAG-3 or dual blockade of LAG-3 and PD-1, depending on the strength of the antigenic stimulus.

PD-1 and its ligands are important immune checkpoints in cancer

Checkpoint programmed death-1 (PD-1)/programmed cell death ligands (PD-Ls) have been identified as negative immunoregulatory molecules that promote immune evasion of tumor cells. The interaction of PD-1 and PD-Ls inhibits the function of T cells and tumor-infiltrating lymphocytes (TIL) while increasing the function of immunosuppressive regulatory T cells (Tregs). This condition causes the tumor cells to evade immune response. Thus, the blockade of PD-1/PD-L1 enhances anti-tumor immunity by reducing the number and/or the suppressive activity of Tregs and by restoring the activity of effector T cells. Furthermore, some monoclonal antibodies blockading PD-1/PD-Ls axis have achieved good effect and received Food and Drug Administration approval. The role of PD-1/PD-Ls in tumors has been well studied, but little is known on the mechanism by which PD-1 blocks T-cell activation. In this study, we provide a brief overview on the discovery and regulatory mechanism of PD-1 and PD-L1 dysregulation in tumors, as well as the function and signaling pathway of PD-1 and its ligands; their roles in tumor evasion and clinical treatment were also studied.

Electrochemotherapy with anti-PD-1 treatment induced durable complete response in heavily pretreated metastatic melanoma patient

Metastatic melanoma (MM) is one of the most lethal types of cancer. Although novel immunotherapeutics have been developed recently, still, these drugs fail to save the lives of a third of MM patients. Electrochemotherapy (ECT) is a local treatment of cancer based on a combination of electroporesis and low-dose chemotherapy. In this case report, we present the treatment history of a MM patient treated successfully with ECT and immunotherapy combination as a fifth-line treatment. Our patient was a 39 year-old woman who was diagnosed with nodulary melanoma stage II. Due to a local recurrence, she was given interferon-α treatment. After 6 months, her disease relapsed in the axillary lymph nodes, and temozolamide treatment 150 mg/m2 was initiated. After six cycles on temozolamide, she progressed both in the axillary site and in the lungs. Her BRAF mutation analysis revealed V600E positivity. Hence, BRAF inhibitor-vemurafenib 2'4 tablets per day was initiated. Within 3 months, she responded dramatically both in the axillary site and in the lungs. At the ninth month of treatment, she progressed again, at which time ipilimumab 3 mg/kg was started as a fourth line treatment. However, shortly after, she progressed again and developed a solitary brain metastasis. She was operated and had whole brain radiotherapy. At that point, nivolumab, an antiprogrammed cell death ligand-1 blocker, was the only remaining option. She showed a biphenotypical response to nivolumab; a mass on the anterior axilla was progressing while the other lymph nodes had regressed. Owing to the accessibility of the subcutaneous lesion with external electrodes, ECT was performed using IGEA Cliniprator device through a hexagonal electrode on the progressive mass, while on nivolumab treatment. A complete response was achieved, with no evidence of disease at 4 years since her local recurrence. Eradication of symptomatic, refractory lesions using ECT meets an important clinical need. Whenever a disseminated disease presents with cutaneous/subcutaneous lesions, high efficacy of ECT should be deployed to augment tumor immunogenicity and complement systemic immunotherapies.

Clinical Significance of Programmed Death-1 Ligand-1 Expression in Patients with Non-Small Cell Lung Cancer: A 5-year-follow-up Study

Aims and background

The programmed death-1-ligand 1 (PD-L1) has been recently suggested to play a pivotal role in the immune evasion of tumors from host immune system. In the study, we tried to reveal the clinical significance of PD-L1 in patients with non-small cell lung cancer (NSCLC), which is one of the most aggressive and intractable malignant tumors.

Methods and study design

PD-L1 expression in 120 NSCLC tissue specimens and 10 benign control samples embedded with wax were retrospectively detected by immunohistochemistry.

Results

No PD-L1 was detected in the 10 benign controls, whereas 57.5% of NSCLC tissue specimens showed PD-L1 expression. There was no relationship between PD-L1 expression and patient age, gender or histopathological type. However, PD-L1 expression was significantly correlated to the degree of tumor cell differentiation, stage of tumor node metastasis (TNM) and patient survival. Poor tumor cell differentiation and advanced TNM stage were related to higher PD-L1 expression. PD-L1-negative NSCLC patients had longer overall 5-year survival than PD-L1-positive patients (P <0.0001). PD-L1 status was a significant independent prognostic factor of NSCLC (χ2 = 18.153, RR = 2.946, P <0.001).

Conclusions

Up-regulated PD-L1 expression in NSCLC is related to the degree of tumor cell differentiation and TNM stage. PD-L1 status may be a new predictor of prognosis for patients with NSCLC.

Cell death-based treatments of melanoma:conventional treatments and new therapeutic strategies

The incidence of malignant melanoma has continued to rise during the past decades. However, in the last few years, treatment protocols have significantly been improved thanks to a better understanding of the key oncogenes and signaling pathways involved in its pathogenesis and progression. Anticancer therapy would either kill tumor cells by triggering apoptosis or permanently arrest them in the G1 phase of the cell cycle. Unfortunately, melanoma is often refractory to commonly used anticancer drugs. More recently, however, some new anticancer strategies have been developed that are “external” to cancer cells, for example stimulating the immune system’s response or inhibiting angiogenesis. In fact, the increasing knowledge of melanoma pathogenetic mechanisms, in particular the discovery of genetic mutations activating specific oncogenes, stimulated the development of molecularly targeted therapies, a form of treatment in which a drug (chemical or biological) is developed with the goal of exclusively destroying cancer cells by interfering with specific molecules that drive growth and spreading of the tumor. Again, after the initial exciting results associated with targeted therapy, tumor resistance and/or relapse of the melanoma lesion have been observed. Hence, very recently, new therapeutic strategies based on the modulation of the immune system function have been developed. Since cancer cells are known to be capable of evading immune-mediated surveillance, i.e., to block the immune system cell activity, a series of molecular strategies, including monoclonal antibodies, have been developed in order to “release the brakes” on the immune system igniting immune reactivation and hindering metastatic melanoma cell growth. In this review we analyze the various biological strategies underlying conventional chemotherapy as well as the most recently developed targeted therapies and immunotherapies, pointing at the molecular mechanisms of cell injury and death engaged by the different classes of therapeutic agents.

CRISPR knock out of programmed cell death protein 1 enhances anti-tumor activity of cytotoxic T lymphocytes

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that functions to attenuate T cell activation. In this study, we knocked out (KO) PD-1 in cytotoxic T lymphocytes (CTLs) using CRISPR-Cas9 system to evaluate its effect on the anti-tumor activity of the CTLs against multiple myeloma (MM). Results show that PD-1 KO CTLs facilitate apoptosis and caspase activation of the co-cultured MM cells and enhanced MM cell death by 36% compared with the control. PD-1 KO also increased TNF-α and IFN-γ secretion of the CTLs by 2.4 and 1.9-fold respectively. The effectiveness of PD-1 KO in enhancing anti-tumor activity of the CTLs was verified in vivo using mouse xenograft model. The xenografted mice treated with PD-1 KO CTLs demonstrated repressed MM tumor growth and prolonged survival compared with the control group. We conclude that CRISPR-Cas9 is an efficient system to knock out PD-1 from CTLs and PD-1 KO could significantly enhance the anti-tumor activity of CTLs.

PD-1/PD-L1 Blockade: Have We Found the Key to Unleash the Antitumor Immune Response?

PD-1–PD-L1 interaction is known to drive T cell dysfunction, which can be blocked by anti-PD-1/PD-L1 antibodies. However, studies have also shown that the function of the PD-1–PD-L1 axis is affected by the complex immunologic regulation network, and some CD8⁺ T cells can enter an irreversible dysfunctional state that cannot be rescued by PD-1/PD-L1 blockade. In most advanced cancers, except Hodgkin lymphoma (which has high PD-L1/L2 expression) and melanoma (which has high tumor mutational burden), the objective response rate with anti-PD-1/PD-L1 monotherapy is only ~20%, and immune-related toxicities and hyperprogression can occur in a small subset of patients during PD-1/PD-L1 blockade therapy. The lack of efficacy in up to 80% of patients was not necessarily associated with negative PD-1 and PD-L1 expression, suggesting that the roles of PD-1/PD-L1 in immune suppression and the mechanisms of action of antibodies remain to be better defined. In addition, important immune regulatory mechanisms within or outside of the PD-1/PD-L1 network need to be discovered and targeted to increase the response rate and to reduce the toxicities of immune checkpoint blockade therapies. This paper reviews the major functional and clinical studies of PD-1/PD-L1, including those with discrepancies in the pathologic and biomarker role of PD-1 and PD-L1 and the effectiveness of PD-1/PD-L1 blockade. The goal is to improve understanding of the efficacy of PD-1/PD-L1 blockade immunotherapy, as well as enhance the development of therapeutic strategies to overcome the resistance mechanisms and unleash the antitumor immune response to combat cancer.

PD-L1 expression is mainly regulated by interferon gamma associated with JAK-STAT pathway in gastric cancer

Despite multidisciplinary treatment for patients with advanced gastric cancer, their prognosis remains poor. Therefore, the development of novel therapeutic strategies is urgently needed, and immunotherapy utilizing anti‐programmed death 1/‐programmed death ligand‐1 mAb is an attractive approach. However, as there is limited information on how programmed death ligand‐1 is upregulated on tumor cells within the tumor microenvironment, we examined the mechanism of programmed death ligand‐1 regulation with a particular focus on interferon gamma in an in vitro setting and in clinical samples. Our in vitro findings showed that interferon gamma upregulated programmed death ligand‐1 expression on solid tumor cells through the JAK‐signal transducer and activator of transcription pathway, and impaired the cytotoxicity of tumor antigen‐specific CTL against tumor cells. Following treatment of cells with anti‐programmed death ligand‐1 mAb after interferon gamma‐pre‐treatment, the reduced anti‐tumor CTL activity by interferon gamma reached a higher level than the non‐treatment control targets. In contrast, programmed death ligand‐1 expression on tumor cells also significantly correlated with epithelial‐mesenchymal transition phenotype in a panel of solid tumor cells. In clinical gastric cancer samples, tumor membrane programmed death ligand‐1 expression significantly positively correlated with the presence of CD8‐positive T cells in the stroma and interferon gamma expression in the tumor. The results suggest that gastric cancer patients with high CD8‐positive T‐cell infiltration may be more responsive to anti‐programmed death 1/‐programmed death ligand‐1 mAb therapy.

Recurrent glioma clinical trial, CheckMate-143: the game is not over yet

Glioblastoma (GBM) is the most common, and aggressive, primary brain tumor in adults. With a median patient survival of less than two years, GBM represents one of the biggest therapeutic challenges of the modern era. Even with the best available treatment, recurrence rates are nearly 100% and therapeutic options at the time of relapse are extremely limited. Nivolumab, an anti-programmed cell death-1 (PD-1) monoclonal antibody, has provided significant clinical benefits in the treatment of various advanced cancers and represented a promising therapy for primary and recurrent GBM. CheckMate 143 (NCT 02017717) was the first large randomized clinical trial of PD pathway inhibition in the setting of GBM, including a comparison of nivolumab and the anti-VEGF antibody, bevacizumab, in the treatment of recurrent disease. However, preliminary results, recently announced in a WFNOS 2017 abstract, demonstrated a failure of nivolumab to prolong overall survival of patients with recurrent GBM, and this arm of the trial was prematurely closed. In this review, we discuss the basic concepts underlying the rational to target PD pathway in GBM, address implications of using immune checkpoint inhibitors in central nervous system malignancies, provide a rationale for possible reasons contributing to the failure of nivolumab to prolong survival in patients with recurrent disease, and analyze the future role of immune checkpoint inhibitors in the treatment of GBM.

An Archaeosome-Adjuvanted Vaccine and Checkpoint Inhibitor Therapy Combination Significantly Enhances Protection from Murine Melanoma

Archaeosomes constitute archaeal lipid vesicle vaccine adjuvants that evoke a strong CD8⁺ T cell response to antigenic cargo. Therapeutic treatment of murine B16-ovalbumin (B16-OVA) melanoma with archaeosome-OVA eliminates small subcutaneous solid tumors; however, they eventually resurge despite an increased frequency of circulating and tumor infiltrating OVA-CD8⁺ T cells. Herein, a number of different approaches were evaluated to improve responses, including dose number, interval, and the combination of vaccine with checkpoint inhibitors. Firstly, we found that tumor protection could not be enhanced by repetitive and/or delayed boosting to maximize the CD8⁺ T cell number and/or phenotype. The in vivo cytotoxicity of vaccine-induced OVA-CD8⁺ T cells was impaired in tumor-bearing mice. Additionally, tumor-infiltrating OVA-CD8⁺ T cells had an increased expression of programmed cell death protein-1 (PD-1) compared to other organ compartments, suggesting impaired function. Combination therapy of tumor-bearing mice with the vaccine archaeosome-OVA, and α-CTLA-4 administered concurrently as well as α-PD-1 and an α-PD-L1 antibody administered starting 9 days after tumor challenge given on a Q3Dx4 schedule (days 9, 12, 15 and 18), significantly enhanced survival. Following multi-combination therapy ~70% of mice had rapid tumor recession, with no detectable tumor mass after >80 days in comparison to a median survival of 17-22 days for untreated or experimental groups receiving single therapies. Overall, archaeosomes offer a powerful platform for delivering cancer antigens when used in combination with checkpoint inhibitor immunotherapies.

Exhaustion of T lymphocytes in the tumor microenvironment: Significance and effective mechanisms

T lymphocytes play crucial roles in adaptive immune responses to tumors. However, due to different tolerance mechanisms and inhibitory effects of the tumor microenvironment (TME) on T cells, responses to tumors are insufficient. In fact, cellular and molecular suppressive mechanisms repress T cell responses in the TME, resulting in senescent, anergic and exhausted lymphocytes. Exhaustion is a poor responsive status of T cells, with up-regulated expression of inhibitory receptors, decreased production of effective cytokines, and reduced cytotoxic activity. Low immunogenicity of tumor antigens and inadequate presentation of tumor-specific antigens results in inappropriate activation of naive T lymphocytes against tumor antigens. Moreover, when effector cytotoxic T cells enter TME, they encounter a complicated network of cells and cytokines that suppress their effectiveness and turn them into exhausted T cells. Thus, the mechanism of T cell exhaustion in cancer is different from that in chronic infections. In this review we will discuss the main components such as inhibitory receptors, inflammatory cells, stromal cells, cytokine milieu as well as environmental and metabolic conditions in TME which play role in development of exhaustion. Furthermore, recent therapeutic methods available to overcome exhaustion will be discussed.

A canine chimeric monoclonal antibody targeting PD-L1 and its clinical efficacy in canine oral malignant melanoma or undifferentiated sarcoma

Immunotherapy targeting immune checkpoint molecules, programmed cell death 1 (PD-1) and PD-ligand 1 (PD-L1), using therapeutic antibodies has been widely used for some human malignancies in the last 5 years. A costimulatory receptor, PD-1, is expressed on T cells and suppresses effector functions when it binds to its ligand, PD-L1. Aberrant PD-L1 expression is reported in various human cancers and is considered an immune escape mechanism. Antibodies blocking the PD-1/PD-L1 axis induce antitumour responses in patients with malignant melanoma and other cancers. In dogs, no such clinical studies have been performed to date because of the lack of therapeutic antibodies that can be used in dogs. In this study, the immunomodulatory effects of c4G12, a canine-chimerised anti-PD-L1 monoclonal antibody, were evaluated in vitro, demonstrating significantly enhanced cytokine production and proliferation of dog peripheral blood mononuclear cells. A pilot clinical study was performed on seven dogs with oral malignant melanoma (OMM) and two with undifferentiated sarcoma. Objective antitumour responses were observed in one dog with OMM (14.3%, 1/7) and one with undifferentiated sarcoma (50.0%, 1/2) when c4G12 was given at 2 or 5 mg/kg, every 2 weeks. c4G12 could be a safe and effective treatment option for canine cancers.

PD-L1 and gastric cancer prognosis: A systematic review and meta-analysis

The expression of Programmed cell Death Ligand 1 (PD-L1) is observed in many malignant tumors and is associated with poor prognosis including Gastric Cancer (GC). The relationship between PD-L1 expression and prognosis, however, is controversial in GC. This paper purports to use a meta-analysis to investigate the relationship between PD-L1 expression and prognosis in GC. For this study, the following databases were searched for articles published from June 2003 until February 2017: PubMed, EBSCO, Web of Science and Cochrane Library. The baseline information extracted were: authors, year of publication, country where the study was performed, study design, sample size, follow-up time, baseline characteristics of the study population, pathologic data, overall survival (OS). A total of 15 eligible studies covering 3291 patients were selected for a meta-analysis based on specified inclusion and exclusion criteria. The analysis showed that the expression level of PD-L1 was associated with the overall survival in GC (Hazard Ratio, HR = 1.46, 95%CI = 1.08-1.98, P = 0.01, random-effect). In addition to the above, subgroup analysis showed that GC patients with deeper tumor infiltration, positive lymph-node metastasis, positive venous invasion, Epstein-Barr virus infection positive (EBV+), Microsatellite Instability (MSI) are more likely to expression PD-L1. The results of this meta-analysis suggest that GC patients, specifically EBV+ and MSI, may be prime candidates for PD-1 directed therapy. These findings support anti-PD-L1/PD-1 antibodies as a kind of immunotherapy which is promising for GC.

Clinical and Histologic Features of Lichenoid Mucocutaneous Eruptions Due to Anti-Programmed Cell Death 1 and Anti-Programmed Cell Death Ligand 1 Immunotherapy

Importance

Antagonist antibodies to programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) have shown remarkable activity in multiple tumor types. Recent US Food and Drug Administration approval of such agents for advanced melanoma, non-small cell lung cancer, and renal cell carcinoma has hastened the need to better characterize their unique toxicity profiles.

Objective

To provide a clinical and pathologic description of the lichenoid mucocutaneous adverse effects seen in patients receiving anti-PD-1/PD-L1 treatment.

Design, Setting, and Participants

Patients with advanced cancer who were referred to dermatology at Yale-New Haven Hospital, a tertiary care hospital, after developing cutaneous adverse effects while receiving an anti-PD-1 or PD-L1 antibody therapy either as monotherapy or in combination with another agent were identified. Medical records from 2010 to 2015 and available skin biopsy specimens were retrospectively reviewed.

Main Outcomes and Measures

Patient demographic characteristics, concurrent medications, therapeutic regimen, type of disease, previous oncologic therapies, clinical morphology of cutaneous lesions, treatment of rash, peripheral blood eosinophil count, tumor response, and skin histologic characteristics if biopsies were available.

Results

Patients were 13 men and 7 women, with a mean (range) age of 64 (46-86) years. The majority of cases (16 [80%]) had a clinical morphology consisting of erythematous papules with scale in a variety of distributions. Biopsies were available from 17 patients; 16 (94%) showed features of lichenoid interface dermatitis. Eighteen patients were treated with topical corticosteroids, and only 1 patient required discontinuation of anti-PD-1/PD-L1 therapy. Only 4 of 20 patients (20%) developed peripheral eosinophilia. Sixteen patients (80%) were concurrently taking medications that have been previously reported to cause lichenoid drug eruptions.

Conclusions and Relevance

Papular and nodular eruptions with scale, as well as mucosal erosions, with lichenoid features on histologic analysis were a distinct finding seen with anti-PD-1/PD-L1 therapies and were generally manageable with topical steroids. Concurrent medications may play a role in the development of this cutaneous adverse effect.

Farnesyltransferase inhibitor FTI-277 inhibits PD-L1 expression on septic spleen lymphocytes and promotes spleen lymphocyte activation

Farnesyltransferase inhibitors have been tested in clinical trials for the treatment of tumours. In sepsis, the binding of programmed death 1 (PD-1) to programmed death ligand 1 (PD-L1) promotes lymphocyte apoptosis and decreases cytokine expression, thus affecting survival rates. The PD-1/PD-L1 pathway plays an important role in chronic viral infection, bacterial infection and sepsis. However, the precise immunosuppressive and anti-inflammatory functions of this pathway remain poorly understood. In our previous study, the induction of sepsis by caecal ligation and puncture (CLP) resulted in increased farnesyltransferase activity and farnesylated protein levels in the spleen relative to sham treatment. However, the effect of inhibition of farnesyltransferase activity on overall survival rates in patients with sepsis and the specific signalling pathway involved remain to be investigated. In this study, mice with CLP-induced sepsis were treated with farnesyltransferase inhibitor (FTI-277), and PD-L1 expression on septic spleen lymphocytes was examined. Flow cytometric analysis revealed that PD-L1 is expressed constitutively on lymphocytes and that PD-L1 protein expression was up-regulated strongly following CLP. FTI-277 down-regulated PD-L1 mRNA and protein expression on septic spleen lymphocytes in a dose-dependent manner. This effect was associated closely with nuclear factor kappa B (NF-κB). In addition, the significant damping effect of FTI-277 on the PD-L1 signal promoted interferon (IFN)-γ secretion, interleukin (IL)-2 production and splenocyte proliferation in response to anti-CD3⁺ CD28⁺ antibodies in mice. Furthermore, FTI-277 reduced spleen lymphocyte apoptosis in septic mice. Therefore, FTI-277 regulates spleen lymphocyte activity via the PD-L1 signalling pathway, with significant anti-inflammatory effects attributable to suppression of the NF-κB pathway. Farnesyltransferase represents a valuable therapeutic target for the treatment of sepsis.

Tim-3 and its role in regulating anti-tumor immunity

Immunotherapy is being increasingly recognized as a key therapeutic modality to treat cancer and represents one of the most exciting treatments for the disease. Fighting cancer with immunotherapy has revolutionized treatment for some patients and therapies targeting the immune checkpoint molecules such as CTLA-4 and PD-1 have achieved durable responses in melanoma, renal cancer, Hodgkin's diseases and lung cancer. However, the success rate of these treatments has been low and a large number of cancers, including colorectal cancer remain largely refractory to CTLA-4 and PD-1 blockade. This has provided impetus to identify other co-inhibitory receptors that could be exploited to enhance response rates of current immunotherapeutic agents and achieve responses to the cancers that are refectory to immunotherapy. Tim-3 is a co-inhibitory receptor that is expressed on IFN-g-producing T cells, FoxP3+ Treg cells and innate immune cells (macrophages and dendritic cells) where it has been shown to suppress their responses upon interaction with their ligand(s). Tim-3 has gained prominence as a potential candidate for cancer immunotherapy, where it has been shown that in vivo blockade of Tim-3 with other check-point inhibitors enhances anti-tumor immunity and suppresses tumor growth in several preclinical tumor models. This review discusses the recent findings on Tim-3, the role it plays in regulating immune responses in different cell types and the rationale for targeting Tim-3 for effective cancer immunotherapy.

Targeted Therapy in Head and Neck Cancer: An Update on Current Clinical Developments in Epidermal Growth Factor Receptor-Targeted Therapy and Immunotherapies

Most patients diagnosed with head and neck squamous cell carcinoma (HNSCC) will present with locally advanced disease, requiring multimodality therapy. Despite this curative approach, a significant subset of these patients will develop locoregional failure and/or distant metastases. Despite significant progress in the treatment and subsequent prognosis of locally advanced HNSCC, the prognosis of those patients with recurrent and/or metastatic (R/M) HNSCC is poor, with short-lived responses to palliative chemotherapy and few therapeutic agents available. The discovery of the integral role of epidermal growth factor receptor overexpression in the pathogenesis of HNSCC, coupled with emerging data on the role of tumor evasion of the immune system, has opened new pathways in the development of novel therapeutic agents for the treatment of R/M HNSCC. As a result, cetuximab, a monoclonal antibody targeting epidermal growth factor receptor, as well as pembrolizumab and nivolumab, monoclonal antibodies targeting programmed cell death 1 (PD-1), are now US Food and Drug Administration approved for the treatment of R/M HNSCC. This review will detail the data supporting the use of these agents, as well as clinical trials evaluating the efficacy of other novel and promising drugs.

PD-1 Blockade Promotes Emerging Checkpoint Inhibitors in Enhancing T Cell Responses to Allogeneic Dendritic Cells

Immune checkpoint inhibitors, which target coinhibitory T cell molecules to promote anticancer immune responses, are on the rise to become a new pillar of cancer therapy. However, current immune checkpoint-based therapies are successful only in a subset of patients and acquired resistances pose additional challenges. Finding new targets and combining checkpoint inhibitors might help to overcome these limitations. In this study, human T cells stimulated with allogeneic dendritic cells (DCs) were used to compare immune checkpoint inhibitors targeting TIM-3, BTLA, LAG-3, CTLA-4, and TIGIT alone or in combination with a PD-1 antibody. We found that PD-1 blockade bears a unique potency to enhance T cell proliferation and cytokine production. Other checkpoint inhibitors failed to significantly augment T cell responses when used alone. However, antibodies to TIM-3, BTLA, LAG-3, and CTLA-4 enhanced T cell proliferation in presence of a PD-1 antibody. Upregulation of coinhibitory T cell receptors upon PD-1 blockade was identified as a potential mechanism for synergistic effects between checkpoint inhibitors. Donor-specific variation in response to immune checkpoint inhibitors was attributed to the T cells rather than DCs. Additionally, we analyzed the regulation of checkpoint molecules and their ligands on T cells and allogeneic DCs in coculture, which suggested a PD-1 blockade-dependent crosstalk between T cells and APC. Our results indicate that several immune checkpoint inhibitors have the capacity to enhance T cell responses when combined with PD-1 blockade. Additional in vitro studies on human T cells will be useful to identify antibody combinations with the potential to augment T cell responses in cancer patients.

[What is the place of the combinations for immunotherapy with chemotherapy or with other immune checkpoint inhibitors?]

Immune checkpoint blockade by the use of anti-PD(L)1 or anti-CTLA4 antibodies can induce long lasting disease response and maybe cure in a lot of advanced cancer patients. This ongoing immunotherapy revolution has given new hope to cancer patients and oncologists. However, still the majority of cancer patients do not respond to immune checkpoint blockade and novel therapeutical possibilities are being tested in several clinical trials. One of the possibilities to enhance responses to immune checkpoint blockade is the combination with chemotherapy or with other immune checkpoint blockade molecules. In this review, we explore the preclinical rational for this synergism and the potential consequences for immunotherapy in oncology.

Function and Clinical Implications of Long Non-Coding RNAs in Melanoma

Metastatic melanoma is the most deadly type of skin cancer. Despite the success of immunotherapy and targeted agents, the majority of patients experience disease recurrence upon treatment and die due to their disease. Long non-coding RNAs (lncRNAs) are a new subclass of non-protein coding RNAs involved in (epigenetic) regulation of cell growth, invasion, and other important cellular functions. Consequently, recent research activities focused on the discovery of these lncRNAs in a broad spectrum of human diseases, especially cancer. Additional efforts have been undertaken to dissect the underlying molecular mechanisms employed by lncRNAs. In this review, we will summarize the growing evidence of deregulated lncRNA expression in melanoma, which is linked to tumor growth and progression. Moreover, we will highlight specific molecular pathways and modes of action for some well-studied lncRNAs and discuss their potential clinical implications.

Transcriptional activation of PD-L1 by Sox2 contributes to the proliferation of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common and lethal malignancies in the world. Sox2 is a potential oncogene in the pathogenesis of HCC, however, the actual mechanisms of Sox2 functions in HCC has not emerged yet. In this study, we explored the expression, function and the relationship between Sox2 and PD-L1 in HCC. We found that both Sox2 and PD-L1 were expressed at a markedly higher level in HCC tissues in comparison to adjacent non-tumor tissues. Moreover, the expression levels of both genes were correlated with each other. Knockdown of Sox2 reduced the cell proliferation ability and induces apoptosis of HCC cells, suggesting the function of Sox2 in regulating both the cell proliferation and apoptosis. Noteworthy, the depletion of Sox2 also reduced the expression of PD-L1. Further analysis showed that there is a consensus Sox2 binding site in the promoter region of PD-L1. Through in vitro EMSA assay and in vivo chromatin immunoprecipitation assays, we demonstrated that Sox2 directly bound to the PD-L1 promoter through the consensus Sox2 motif. Further evidence by luciferase reporter assays revealed that Sox2 promoted the transcription activity of PD-L1 promoter region through the Sox2 motif. Collectively, our data provide a novel insight into the function and the interplay of Sox2 and PD-L1 in HCC.

The role of anti-PD-1 and anti-PD-L1 agents in the treatment of diffuse large B-cell lymphoma: The future is now

Immune checkpoints inhibitors have been incorporated into standard treatment protocols for advanced solid tumors. The aim of T-cell-based immune therapy in cancer has been to generate durable clinical benefits for patients, paired with enhanced side effect profiles. The beneficial antitumoral activity of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) has been thoroughly demonstrated in certain metastatic malignancies (e.g. melanoma, non-small cell lung cancer, renal cell carcinoma); however, the therapeutic role in lymphoid cancers is complex. Nonetheless, the striking clinical activity seen in early clinical trials of various subtypes of relapsed lymphoma have paved the way for these exciting innovative therapeutic alternatives in these tumors. In this article we assess the literature on the role of the PD-1/PD-L1 pathway in Diffuse Large B-cell lymphoma (DLBCL), and describe future strategies involving these new anticancer agents in this lymphoid neoplasm.

SOCS1 favors the epithelial-mesenchymal transition in melanoma, promotes tumor progression and prevents antitumor immunity by PD-L1 expression

Silencing of SOCS1 protein with shRNAi lentivirus (shR-SOCS1) led to partial reversion of the tumorigenic phenotype of B16F10-Nex2 melanoma cells. SOCS1 silencing inhibited cell migration and invasion as well as in vitro growth by cell cycle arrest at S phase with increased cell size and nuclei. Down-regulation of SOCS1 decreased the expression of epidermal growth factor receptor, Ins-Rα, and fibroblast growth factor receptors. The present work aimed at analyzing the SOCS1 cell signaling and expression of proteins relevant to tumor development. An RNA microarray analysis of B16F10-Nex2 melanoma cells with SOCS1 silenced by shRNAi-SOCS1 was undertaken in comparison with cells transduced with the empty vector. Among 609 differentially expressed genes, c-Kit, Met and EphA3 cytokine/tyrosine-kinase (TK) receptors were down regulated. A significant decrease in the expression of TK receptors, the phosphorylation of mediators of ERK1/2 and p38 pathways and STAT3 (S727) were observed. Subcutaneous immunization with shR-SOCS1-transduced viable tumor cells rendered protection against melanoma in a syngeneic model, with decreased expression of PD-L1 and of matrix metallo-proteinases (MMPs) and CD-10 in those cells. The present work shows the role of SOCS1 in murine melanoma development and the potential of SOCS1-silenced tumor cells in raising an effective anti-melanoma immune response.

Helicobacter Pylori Promote B7-H1 Expression by Suppressing miR-152 and miR-200b in Gastric Cancer Cells

The most common cause of gastric cancer is infection with helicobacter pylori (HP), but the associated molecular mechanism is not well understood. In the present study, we found a marked increase in the expression of B7-H1, a member of the B7 co-stimulatory family of molecules that bind to programmed death-1 (PD-1) and play a critical immunoregulatory role in the cell-mediated immune response, in HP-positive gastric cancer tissue. Infection of cultured gastric cancer cells with HP promoted B7-H1 expression and inhibited miR-152 and miR-200b expression. We further demonstrated that these two miRNAs targeted B7-H1 mRNA and suppressed B7-H1 expression in gastric cancer cells. Finally, B7-H1 expression was found to correlate with miR-152 and miR-200b levels in gastric tumor tissues from human patients. Our findings suggest a novel mechanism by which HP infection promotes gastric cancer and also suggest potential targets, i.e., miR-152 and miR-200b, for the prevention and treatment of gastric cancer.

Emerging biomarkers for PD-1 pathway cancer therapy

The field of immuno-oncology has witnessed unprecedented success in recent years, with several PD=1 and PD-L1 inhibitors obtaining US FDA registration and breakthrough drug therapy designation in multiple tumor types. Despite its clear efficacy in certain cancers, treatment with these agents carries a risk of immune-related toxicities and substantial financial burden. It is, therefore, critical to identify patients likely to benefit from such immunotherapies and develop strategies to differentiate responders from nonresponders early during treatment. Here we discuss the development of predictive and treatment response biomarkers for immune checkpoint inhibitors. We first examine the role of PD-L1 expression, the most extensively studied predictive biomarker of response, and further discuss emerging putative predictive biomarkers. We also detail challenges faced in the development of response assessments for immunotherapeutics and propose other biomarkers that may be useful as surrogate intermediate end points of response.

Implication of combined PD-L1/PD-1 blockade with cytokine-induced killer cells as a synergistic immunotherapy for gastrointestinal cancer

Cytokine-induced killer (CIK) cells represent a realistic approach in cancer immunotherapy with confirmed survival benefits in the context of metastatic solid tumors. However, therapeutic effects are limited to a fraction of patients. In this study, immune-resistance elements and ideal combination therapies were explored. Initially, phenotypic analysis was performed to document CD3, CD56, NKG2D, DNAM-1, PD-L1, PD-1, CTLA-4, TIM-3, 2B4, and LAG-3 on CIK cells. Upon engagement of CIK cells with the tumor cells, expression of PD-1 on CIK cells and PD-L1 on both cells were up-regulated. Over-expression of PD-L1 levels on tumor cells via lentiviral transduction inhibited tumoricidal activity of CIK cells, and neutralizing of PD-L1/PD-1 signaling axis could enhance their tumor-killing effect. Conversely, blockade of NKG2D, a major activating receptor of CIK cells, largely caused dysfunction of CIK cells. Functional study showed an increase of NKG2D levels along with PD-L1/PD-1 blockade in the presence of other immune effector molecule secretion. Additionally, combined therapy of CIK infusion and PD-L1/PD-1 blockade caused a delay of in vivo tumor growth and exhibited a survival advantage over untreated mice. These results provide a preclinical proof-of-concept for simultaneous PD-L1/PD-1 pathways blockade along with CIK infusion as a novel immunotherapy for unresectable cancers.

Crystal clear: visualizing the intervention mechanism of the PD-1/PD-L1 interaction by two cancer therapeutic monoclonal antibodies

Antibody-based PD-1/PD-L1 blockade therapies have taken center stage in immunotherapies for cancer, with multiple clinical successes. PD-1 signaling plays pivotal roles in tumor-driven T-cell dysfunction. In contrast to prior approaches to generate or boost tumor-specific T-cell responses, antibody-based PD-1/PD-L1 blockade targets tumor-induced T-cell defects and restores pre-existing T-cell function to modulate antitumor immunity. In this review, the fundamental knowledge on the expression regulations and inhibitory functions of PD-1 and the present understanding of antibody-based PD-1/PD-L1 blockade therapies are briefly summarized. We then focus on the recent breakthrough work concerning the structural basis of the PD-1/PD-Ls interaction and how therapeutic antibodies, pembrolizumab targeting PD-1 and avelumab targeting PD-L1, compete with the binding of PD-1/PD-L1 to interrupt the PD-1/PD-L1 interaction. We believe that this structural information will benefit the design and improvement of therapeutic antibodies targeting PD-1 signaling.

Seeing is believing: anti-PD-1/PD-L1 monoclonal antibodies in action for checkpoint blockade tumor immunotherapy

Structural immunology, focusing on structures of host immune related molecules, enables the immunologists to see what the molecules look like, and more importantly, how they work together. Antibody-based PD-1/PD-L1 blockade therapy has achieved brilliant successes in clinical applications. The recent breakthrough of the complex structures of checkpoint blockade antibodies with their counterparts, pembrolizumab with PD-1 and avelumab with PD-L1, have made it clear how these monoclonal antibodies compete the binding of PD-1/PD-L1 and function to blockade the receptor-ligand interaction. Herein, we summarize the structural findings of these two reports and look into the future for how this information would facilitate the development of more efficient PD-1/PD-L1 targeting antibodies, small molecule drugs, and other protein or non-protein inhibitors.

Immune checkpoint therapy for pancreatic cancer

Novel treatment modalities are necessary for pancreatic cancer. Immunotherapy with immune checkpoint inhibition has shown effect in other solid tumors, and could have a place in pancreatic cancer treatment. Most available clinical studies on immune checkpoint inhibitors for pancreatic cancer are not yet completed and are still recruiting patients. Among the completed trials, there have been findings of a preliminary nature such as delayed disease progression and enhanced overall survival after treatment with immune checkpoint inhibitors in mono- or combination therapy. However, due to small sample sizes, major results are not yet identifiable. The present article provides a clinical overview of immune checkpoint inhibition in pancreatic cancer. PubMed, ClinicalTrials.gov and American Society of Clinical Oncology’s meeting abstracts were systematically searched for relevant clinical studies. Four articles, five abstracts and 25 clinical trials were identified and analyzed in detail.

Response to Programmed Cell Death-1 Blockade in a Murine Melanoma Syngeneic Model Requires Costimulation, CD4, and CD8 T Cells

The programmed cell death protein 1 (PD-1) limits effector T-cell functions in peripheral tissues, and its inhibition leads to clinical benefit in different cancers. To better understand how PD-1 blockade therapy modulates the tumor-host interactions, we evaluated three syngeneic murine tumor models, the BRAF^V600E-driven YUMM1.1 and YUMM2.1 melanomas, and the carcinogen-induced murine colon adenocarcinoma MC38. The YUMM cell lines were established from mice with melanocyte-specific BRAF^V600E mutation and PTEN loss (BRAF^V600E/PTEN^-/-). Anti-PD-1 or anti-PD-L1 therapy engendered strong antitumor activity against MC38 and YUMM2.1, but not YUMM1.1. PD-L1 expression did not differ between the three models at baseline or upon interferon stimulation. Whereas mutational load was high in MC38, it was lower in both YUMM models. In YUMM2.1, the antitumor activity of PD-1 blockade had a critical requirement for both CD4 and CD8 T cells, as well as CD28 and CD80/86 costimulation, with an increase in CD11c⁺CD11b⁺MHC-II^high dendritic cells and tumor-associated macrophages in the tumors after PD-1 blockade. Compared with YUMM1.1, YUMM2.1 exhibited a more inflammatory profile by RNA sequencing analysis, with an increase in expression of chemokine-trafficking genes that are related to immune cell recruitment and T-cell priming. In conclusion, response to PD-1 blockade therapy in tumor models requires CD4 and CD8 T cells and costimulation that is mediated by dendritic cells and macrophages. Cancer Immunol Res; 4(10); 845-57. ©2016 AACR.

Malignant Mesothelioma Effusions Are Infiltrated by CD3+ T Cells Highly Expressing PD-L1 and the PD-L1+ Tumor Cells within These Effusions Are Susceptible to ADCC by the Anti-PD-L1 Antibody Avelumab

INTRODUCTION

The functional aspects of programmed death 1 (PD-1) and PD ligand 1 (PD-L1) immune checkpoints in malignant mesothelioma have not been studied.

METHODS

Tumor samples from 65 patients with mesothelioma were evaluated for PD-L1 expression by immunohistochemistry, and its prognostic significance was examined. Malignant effusions from patients with pleural and peritoneal mesothelioma were evaluated for PD-1-positive and PD-L1-positive infiltrating lymphocytes and their role in inducing PD-L1 expression in tumor cells. Antibody-dependent cellular cytotoxicity (ADCC) of avelumab, a fully humanized immunoglobulin G1 anti PD-L1 antibody against primary mesothelioma cell lines, was evaluated in presence of autologous and allogeneic natural killer cells.

RESULTS

Of 65 pleural and peritoneal mesothelioma tumors examined, 41 (63%) were PD-L1-positive, which was associated with slightly inferior overall survival compared to patients with PD-L1-negative tumors (median 23.0 versus 33.3 months, p = 0.35). The frequency of PD-L1 expression was similar in patients with pleural and peritoneal mesothelioma, with 62% and 64% of samples testing positive, respectively. In nine mesothelioma effusion samples evaluated, the fraction of cells expressing PD-L1 ranged from 12% to 83%. In seven patients with paired malignant effusion and peripheral blood mononuclear cell (PBMC) samples, PD-L1 expression was significantly higher on CD3-positive T cells present in malignant effusions as compared with PBMCs (p = 0.016). In addition, the numbers of CD14-positive PD-1-positive cells were increased in malignant effusions compared with PBMCs (p = 0.031). The lymphocytes present in malignant effusions recognized autologous tumor cells and induced interferon-γ-mediated PD-L1 expression on the tumor cell surface. Of the three primary mesothelioma cell lines tested, two were susceptible to avelumab-mediated ADCC in the presence of autologous natural killer cells.

CONCLUSIONS

Most pleural as well as peritoneal mesotheliomas express PD-L1. Malignant effusions in this disease are characterized by the presence of tumor cells and CD3-positive T cells that highly express PD-L1. In addition, mesothelioma tumor cells are susceptible to ADCC by the anti-PD-L1 antibody avelumab.

The evolving role of monoclonal antibodies in the treatment of patients with advanced renal cell carcinoma: a systematic review

INTRODUCTION

While the majority of the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) inhibitors currently used for the therapy of metastatic renal cell carcinoma (mRCC) are small molecule agents inhibiting multiple targets, monoclonal antibodies are inhibitors of specific targets, which may decrease off-target effects while preserving on-target activity. A few monoclonal antibodies have already been approved for mRCC (bevacizumab, nivolumab), while many others may play an important role in the therapeutic scenario of mRCC.

AREAS COVERED

This review describes emerging monoclonal antibodies for treating RCC. Currently, bevacizumab, a VEGF monoclonal antibody, is approved in combination with interferon for the therapy of metastatic RCC, while nivolumab, a Programmed Death (PD)-1 inhibitor, is approved following prior VEGF inhibitor treatment. Other PD-1 and PD-ligand (L)-1 inhibitors are undergoing clinical development.

EXPERT OPINION

Combinations of inhibitors of the PD1/PD-L1 axis with VEGF inhibitors or cytotoxic T-lymphocyte antigen (CTLA)-4 inhibitors have shown promising efficacy in mRCC. The development of biomarkers predictive for benefit and rational tolerable combinations are both important pillars of research to improve outcomes in RCC.

Intratumoral expression of programmed death ligand 1 (PD-L1) in patients with clear cell renal cell carcinoma (ccRCC)

The immunological checkpoints of programmed death 1 and its ligand (PD-L1) are currently in focus as novel therapeutic targets in renal cell carcinoma (RCC). The aim of this study was to evaluate the prognostic association of PD-L1 expression in clear cell (cc) RCC with clinical parameters, tumor aggressiveness and overall survival (OS). Patients who underwent renal surgery due to RCC between 1994 and 2003 were retrospectively evaluated. Tumor specimens were analyzed for PD-L1 expression by immunohistochemistry. One hundred and seventy-seven ccRCC patients were eligible for analysis, in which 140 (79.1 %) were negative and 37 (20.9 %) were positive for PD-L1 expression. PD-L1 positivity was associated with female gender (p = 0.001), lymph node metastasis (p = 0.004), distant metastasis (p = 0.002), higher AJCC stage (p = 0.004), as well as advanced disease (pT3/4 and/or N+ and/or M1) (p < 0.001). Kaplan-Meier analysis revealed a significantly diminished 5- and 10-year overall survival of 46.7 and 28.3 % for PD-L1(+) compared to PD-L1(-) tumors with 66 and 53.4 % (p = 0.005), respectively. Univariate analysis showed a significant negative association of OS with PD-L1 positivity [p = 0.005; HR: 2 (95 % CI 1.2-3.3)], even though PD-L1 positivity only tends to predict independently the OS using multivariate analyses [p = 0.066; HR: 1.6 (95 % CI 0.98-2.7)]. PD-L1 expression in ccRCC is associated with parameters of aggressiveness, as well as with poor OS, even though PD-L1 status was not identified as a significant independent prognostic parameter. However, further studies in larger cohorts are warranted.

Immunohistochemical Analysis of PD-L1 Expression in Canine Malignant Cancers and PD-1 Expression on Lymphocytes in Canine Oral Melanoma

Spontaneous cancers are common diseases in dogs. Among these, some malignant cancers such as oral melanoma, osteosarcoma, hemangiosarcoma, and mast cell tumor are often recognized as clinical problems because, despite their high frequencies, current treatments for these cancers may not always achieve satisfying outcomes. The absence of effective systemic therapies against these cancers leads researchers to investigate novel therapeutic modalities, including immunotherapy. Programmed death 1 (PD-1) is a costimulatory receptor with immunosuppressive function. When it binds its ligands, PD-ligand 1 (PD-L1) or PD-L2, PD-1 on T cells negatively regulates activating signals from the T cell receptor, resulting in the inhibition of the effector function of cytotoxic T lymphocytes. Aberrant PD-L1 expression has been reported in many human cancers and is considered an immune escape mechanism for cancers. In clinical trials, anti-PD-1 or anti-PD-L1 antibodies induced tumor regression for several malignancies, including advanced melanoma, non-small cell lung carcinoma, and renal cell carcinoma. In this study, to assess the potential of the PD-1/PD-L1 axis as a novel therapeutic target for canine cancer immunotherapy, immunohistochemical analysis of PD-L1 expression in various malignant cancers of dogs was performed. Here, we show that dog oral melanoma, osteosarcoma, hemangiosarcoma, mast cell tumor, mammary adenocarcinoma, and prostate adenocarcinoma expressed PD-L1, whereas some other types of cancer did not. In addition, PD-1 was highly expressed on tumor-infiltrating lymphocytes obtained from oral melanoma, showing that lymphocytes in this cancer type might have been functionally exhausted. These results strongly encourage the clinical application of PD-1/PD-L1 inhibitors as novel therapeutic agents against these cancers in dogs.

Process of hepatic metastasis from pancreatic cancer: biology with clinical significance

PURPOSE

Pancreatic cancer shows a remarkable preference for the liver to establish secondary tumors. Selective metastasis to the liver is attributed to the development of potential microenvironment for the survival of pancreatic cancer cells. This review aims to provide a full understanding of the hepatic metastatic process from circulating pancreatic cancer cells to their settlement in the liver, serving as a basic theory for efficient prediction and treatment of metastatic diseases.

METHODS

A systematic search of relevant original articles and reviews was performed on PubMed, EMBASE and Cochrane Library for the purpose of this review.

RESULTS

Three interrelated phases are delineated as the contributions of the interaction between pancreatic cancer cells and the liver to hepatic metastasis process. Chemotaxis of disseminated pancreatic cancer cells and simultaneous defensive formation of platelets or neutrophils facilitate specific metastasis toward the liver. Remodeling of extracellular matrix and stromal cells in hepatic lobules and angiogenesis induced by proangiogenic factors support the survival and growth of clinical micrometastasis colonizing the liver. The bimodal role of the immune system or prevalence of cancer cells over the immune system makes metastatic progression successfully proceed from micrometastasis to macrometastasis.

CONCLUSIONS

Pancreatic cancer is an appropriate research object of cancer metastasis representing more than a straight cascade. If any of the successive or simultaneous phases, especially tumor-induced immunosuppression, is totally disrupted, hepatic metastasis will be temporarily under control or even cancelled forever. To shrink cancers on multiple fronts and prolong survival for patients, novel oral or intravenous anti-cancer agents covering one or different phases of metastatic pancreatic cancer are expected to be integrated into innovative strategies on the premise of safety and efficacious biostability.

Prognostic significance of PD-L1 expression in patients with gastric cancer in East Asia: a meta-analysis

The overexpression of programmed cell death-ligand 1(PD-L1) has been observed in gastric cancer (GC). However, whether the expression of PD-L1 in tumor cells or blood serum is associated with the prognosis of patients with GC remains unclear. Therefore, we performed a meta-analysis to evaluate the prognostic significance of PD-L1 expression in GC. Electronic databases were searched systematically. Studies that met the inclusion criteria were included in the meta-analysis. Data concerning the hazard ratio (HR) for overall survival and disease-free survival with a 95% confidence interval (CI) according to the expression status of PD-L1 evaluated by immunohistochemistry or enzyme-linked immunosorbent assay were extracted. The data were analyzed using a random effects model. Subgroup analyses were proposed. Our results showed that eight studies with 950 patients met the inclusion criteria and were included in the meta-analysis. The pooled HR for overall survival indicated that patients with PD-L1-positive expression had significantly shorter survival time compared with the PD-L1-negative group (HR 1.60, 95% CI 1.09-2.36, P=0.012). The pooled HR for disease-free survival demonstrated that the difference between the two groups was not statistically significant (HR 1.02, 95% CI 0.32-3.20, P=0.98). In conclusion, our results indicate that the evaluation of PD-L1 overexpression in GC tissue or blood serum may be useful in the future as a novel prognostic factor.

Anti-Programmed Cell Death (PD)-1 Immunotherapy for Malignant Tumor: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis evaluated anti–programmed cell death (PD)-1 immunotherapy (nivolumab or pembrolizumab) for overall efficacy, safety, and effective dose relative to standard chemotherapy or other conventional drugs in the treatment of malignant tumors. We searched the following databases, PubMed, Medline, Embase, Cochrane, Wangfang Data, Weipu, and China National Knowledge Infrastructure, and the reference lists of the selected articles for randomized controlled trials (RCTs) of anti–PD-1 therapies in humans. The outcome measures were overall survival, treatment response, and adverse events. Only four randomized controlled trials met our inclusion criteria. Three of these evaluated responses to nivolumab, whereas one tested pembrolizumab. The result of our analysis suggested that nivolumab may improve the overall response rate in treating melanoma relative to chemotherapy and has few associated adverse events. Similarly, in metastatic melanoma patients, nivolumab had a significant advantage over dacarbazine in terms of 1-year survival, progression-free survival, and objective response rate. Regarding dose levels of nivolumab for patients with metastatic renal cell carcinoma, the outcomes in response to 2 and 10 mg/kg were similar, but both had significant advantages over 0.3 mg/kg. In addition, pembrolizumab showed similar outcomes in response to 2- and 10-mg/kg treatment. Anti–PD-1 immunotherapy appears to be safe and effective for patients with melanoma or metastatic renal cell carcinoma. Our meta-analysis is limited, but additional clinical trials are warranted to verify this preliminary evidence of positive outcomes and before anti–PD-1 therapy can be recommended for routine clinical use.