The programmed death-1 ligand 1:B7-1 pathway restrains diabetogenic effector T cells in vivo

SAKK 19/17: safety analysis of first-line durvalumab in patients with PD-L1 positive, advanced nonsmall cell lung cancer and a performance status of 2

INTRODUCTION

The safety of first-line (1L) durvalumab in patients with advanced nonsmall-cell lung cancer (NSCLC) and an Eastern Cooperative Oncology Group (ECOG) performance status of 2 (PS2) is unknown. This is an interim unplanned safety analysis of the study SAKK 19/17 for patients with metastatic NSCLC with programmed death-ligand 1 (PD-L1) expression in ≥ 25% of tumor cells and an ECOG PS2 treated with 1L durvalumab. This safety analysis was triggered by the SAKK data and safety monitoring board due to a high mortality rate observed after the recruitment of the first 21 patients.

METHODS

This single-arm phase II study recruited patients with metastatic NSCLC with PD-L1 in ≥ 25% and ECOG PS2. Patients received durvalumab 1500 mg every four weeks. The trial aims to recruit 48 patients in total. This report includes safety analyses only. Adverse events (AEs) were assessed using National Cancer Institute Common Terminology Criteria for AEs (NCI CTCAE) Version 5.0. Efficacy data including the primary endpoint overall survival at 6 months and secondary endpoints (objective response rate, progression-free survival, and quality of life) will be reported at a later time point.

RESULTS

The data from 21 patients were available at this interim safety analysis. Among these, 13 deaths (13/21; 62%) were reported, including one treatment-related fatal colonic perforation at 9 months after treatment initiation (1/13; 8%). Twelve deaths were not treatment-related (12/13; 92%), and mostly attributed to tumor progression (10/13; 77%). Of note, seven deaths (7/13; 54%) occurred during the first 5 weeks (range 0.6-4.7 weeks) after treatment initiation. Four (4/7; 57%) were respiratory failures attributed to tumor progression. One of these patients (25%) had pre-existing COPD, and three (75%) had baseline dyspnea grade 2-3 related to the tumor. Grade ≥ 3 treatment-related AEs (TRAEs) included colonic perforation (grade 5), abdominal pain, and colitis (grade 3 each) in one patient, and fatigue (grade 3) in another. Other Grade ≥ 3 AEs unrelated to treatment were all of pulmonary origin: lung infections (19%), dyspnea (24%), cough (5%), and bronchial obstruction (5%).

CONCLUSIONS

1L durvalumab in patients with ECOG PS2 and metastatic NSCLC with PD-L1 expression ≥ 25% resulted in an unexpectedly high number of fatal early events due to rapid tumor progression. We recommend to avoid treatment with 1 L durvalumab of patients who are highly symptomatic from the tumor, particularly those with respiratory symptoms. The study is continuing its accrual after an amendment excluding these patients.

89Zr-Labeled Anti-PD-L1 Antibody PET Monitors Gemcitabine Therapy-Induced Modulation of Tumor PD-L1 Expression

We developed an ⁸⁹Zr-labeled anti-programmed death ligand 1 (anti-PD-L1) immune PET that can monitor chemotherapy-mediated modulation of tumor PD-L1 expression in living subjects. Methods: Anti-PD-L1 underwent sulfohydryl moiety-specific conjugation with maleimide-deferoxamine followed by ⁸⁹Zr radiolabeling. CT26 colon cancer cells and PD-L1-overexpressing CT26/PD-L1 cells underwent binding assays, flow cytometry, and Western blotting. In vivo pharmacokinetics, biodistribution, and PET imaging were evaluated in mice. Results: ⁸⁹Zr-anti-PD-L1 synthesis was straightforward and efficient. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that reduction produced half-antibody fragments, and matrix-assisted laser desorption ionization time-of-flight analysis estimated 2.18 conjugations per antibody, indicating specific conjugation at the hinge-region disulfide bonds. CT26/PD-L1 cells showed 102.2 ± 6.7-fold greater ⁸⁹Zr-anti-PD-L1 binding than that of weakly expressing CT26 cells. Excellent target specificity was confirmed by a drastic reduction in binding by excess cold antibody. Intravenous ⁸⁹Zr-anti-PD-L1 followed biexponential blood clearance. PET/CT image analysis demonstrated decreases in major organ activity over 7 d, whereas high CT26/PD-L1 tumor activity was maintained. Again, this was suppressed by excess cold antibody. Treatment of CT26 cells with gemcitabine for 24 h augmented PD-L1 protein to 592.4% ± 114.2% of the control level and increased ⁸⁹Zr-anti-PD-L1 binding, accompanied by increased AKT (protein kinase B) activation and reduced phosphatase and tensin homolog (PTEN). In CT26 tumor-bearing mice, gemcitabine treatment substantially increased tumor uptake from 1.56% ± 0.48% to 6.24% ± 0.37% injected dose per gram (tumor-to-blood ratio, 34.7). Immunoblots revealed significant increases in tumor PD-L1 and activated AKT and a decrease in PTEN. Conclusion: ⁸⁹Zr-anti-PD-L1 showed specific targeting with favorable imaging properties. Gemcitabine treatment upregulated cancer cell and tumor PD-L1 expression and increased ⁸⁹Zr-anti-PD-L1 uptake. ⁸⁹Zr-anti-PD-L1 PET may thus be useful for monitoring chemotherapy-mediated tumor PD-L1 modulation in living subjects.

Evaluation of the role of B7-H3 haplotype in association with impaired B7-H3 expression and protection against type 1 diabetes in Chinese Han population

BACKGROUND

Type 1 Diabetes (T1D) is a T cell-mediated autoimmune disorder caused by the destruction of insulin-secreting cells. B7-H3 (CD276) plays a vital role in T cell response. However, B7-H3 expression and its clinical significance in T1D remain unclear. The aim of this study was to investigate the correlations between the expression of B7-H3 and clinical parameters in T1D patients. The possible role of B7-H3 gene variants with T1D was also discussed.

METHODS

Four B7-H3 single nucleotide polymorphisms (SNPs) were genotyped in 121 T1D patients and 120 healthy controls by polymerase chain reaction (PCR) direct sequencing. Expression of membrane B7-H3 (mB7-H3) in peripheral blood lymphocytes was determined by flow cytometry. Levels of soluble B7-H3 (sB7-H3) in serum were analyzed by enzyme linked immunosorbent assay (ELISA).

RESULTS

The B7-H3 haplotype T-A-C-T was less frequently observed in T1D patients compared to the controls (OR: 0.31, 95% CI: 0.16-0.61). B7-H3 expression on monocytes showed significant upregulation in T1D patients and was positively correlated with several clinical features including ALT, fast C-peptide 120 min, HbAlc, IFN-γ, IL-6 and TNF-α (P < 0.05). The concentration of sB7-H3 in serum increased in T1D patients (P < 0.0001). We also observed that B7-H3-T-A-C-T was associated with the decreased release of sB7-H3 but not the membrane form.

CONCLUSIONS

B7-H3 may act as a potential biomarker related to the pathogenesis of T1D. The B7-H3-T-A-C-T polymorphism variant is associated with the low risk of T1D as well as less release of sB7-H3.

The relative and absolute benefit of programmed death receptor-1 vs programmed death ligand 1 therapy in advanced non-small-cell lung cancer: A systematic review and meta-analysis

INTRODUCTION

Programmed death receptor-1 (PD-1) and its ligand (PD-L1) inhibitors have shown promising results in treating advanced non-small-cell lung cancer (NSCLC). Our objective was to compare the relative and absolute benefits between PD-1 and PD-L1 inhibitors in advanced NSCLC.

MATERIALS AND METHODS

PubMed, EMBASE and the Cochrane Library were searched up to Dec 1, 2019, for randomized controlled trials of PD-1/PD-L1 inhibitors that had available overall survival (OS) data in NSCLC. Random-effects models were used to calculate the pooled estimates.

RESULTS

Twenty-three randomized controlled trials (15,797 patients) of PD-1/PD-L1 inhibitors were included in the analysis. PD-1 inhibitors significantly extended OS compared with standard of care therapy (difference in means, 4.80 months, 95% CI 3.41-6.18; HR 0.72, 95% CI 0.66-0.78; P < 0.01 for both). PD-L1 inhibitors also significantly improved OS compared with standard of care therapy (difference in means, 2.59 months 95% CI 1.47-3.71; HR 0.83, 95% CI 0.79-0.88; P < 0.01 for both). More importantly, PD-1 inhibitors had significantly higher OS than PD-L1 inhibitors (difference in means, P = 0.015; HR, P = 0.006). The same increased OS benefit was observed in patients with PD-L1 ≥1% (P = 0.035) and PD-L1 <1% (P = 0.007). However, OS did not differ between PD-1 and PD-L1 inhibitors in patients with an EGFR mutation-positive status (P = 0.724) and who were never smokers (P = 0.999).

CONCLUSIONS

PD-1 inhibitors showed superior relative and absolute OS benefits compared with PD-L1 inhibitors in the treatment of advanced NSCLC. These findings have implications for treatment selection in current clinical practice and future study design.

Mechanistic dissection of the PD-L1:B7-1 co-inhibitory immune complex

The B7 family represents one of the best-studied subgroups within the Ig superfamily, yet new interactions continue to be discovered. However, this binding promiscuity represents a major challenge for defining the biological contribution of each specific interaction. We developed a strategy for addressing these challenges by combining cell microarray and high-throughput FACS methods to screen for promiscuous binding events, map binding interfaces, and generate functionally selective reagents. Applying this approach to the interactions of mPD-L1 with its receptor mPD-1 and its ligand mB7-1, we identified the binding interface of mB7-1 on mPD-L1 and as a result generated mPD-L1 mutants with binding selectivity for mB7-1 or mPD-1. Next, using a panel of mB7-1 mutants, we mapped the binding sites of mCTLA-4, mCD28 and mPD-L1. Surprisingly, the mPD-L1 binding site mapped to the dimer interface surface of mB7-1, placing it distal from the CTLA-4/CD28 recognition surface. Using two independent approaches, we demonstrated that mPD-L1 and mB7-1 bind in cis, consistent with recent reports from Chaudhri A et al. and Sugiura D et al. We further provide evidence that while CTLA-4 and CD28 do not directly compete with PD-L1 for binding to B7-1, they can disrupt the cis PD-L1:B7-1 complex by reorganizing B7-1 on the cell surface. These observations offer new functional insights into the regulatory mechanisms associated with this group of B7 family proteins and provide new tools to elucidate their function in vitro and in vivo.

Ectopic PD-L1 expression in JAK2 (V617F) myeloproliferative neoplasm patients is mediated via increased activation of STAT3 and STAT5

Escalated PD-L1 expression has been identified during malignant transformation in a number of cancer types and helps cancer cells escape an effective anti-tumor immune response. The mechanisms underlying escalated production of PD-L1 in many cancers, however, are still far from clear. We studied PD-L1, STAT3 and STAT5 mRNA expression using qRT-PCR in 72 BCR/ABL1 negative myeloproliferative neoplasm (MPN) patients (39 polycythemia vera and 33 essential thrombocythemia). Furthermore, phosphorylation status of STAT3 and STAT5 was studied using immunoblotting in the same patients. All MPN patients were first screened for JAK2 (V617F) mutation by tetra-primer ARMS-PCR, followed by quantification of JAK2 (V617F) mutation burden in all V617F positive MPN patients by ASO-PCR. Patients were screened for BCR/ABL1 fusion gene transcripts to rule out Ph positive status. Our findings showed that mRNA levels of PD-L1 and STAT3 were significantly higher in JAK2 (V617F) MPN patients, while as STAT5 was insignificantly upregulated. STAT3 and STAT5 phosphorylation was seen to be higher in JAK2 (V617F) MPN patients compared to the JAK2 (WT) patients. Upregulation of PD-L1, STAT3 and STAT5 was significantly associated with JAK2 (V617F) percentage in MPN patients. PD-L1, STAT3 and STAT5 expression significantly and positively correlated with JAK2 (V617F) allele burden. In addition, significant coexpression of PD-L1 with STAT3 and STAT5 was observed in MPN patients. In summary, JAK2 (V617F) mutation is accompanied by increased PD-L1 expression and this PD-L1 over expression is mediated by JAK2 (V617F) mainly through STAT3, while as STAT5 may play a minor role.

Localized Immunomodulation with PD-L1 Results in Sustained Survival and Function of Allogeneic Islets without Chronic Immunosuppression

Allogeneic islet transplantation is limited by adverse effects of chronic immunosuppression used to control rejection. The programmed cell death 1 pathway as an important immune checkpoint has the potential to obviate the need for chronic immunosuppression. We generated an oligomeric form of programmed cell death 1 ligand chimeric with core streptavidin (SA-PDL1) that inhibited the T effector cell response to alloantigens and converted T conventional cells into CD4⁺Foxp3⁺ T regulatory cells. The SA-PDL1 protein was effectively displayed on the surface of biotinylated mouse islets without a negative impact islet viability and insulin secretion. Transplantation of SA-PDL1-engineered islet grafts with a short course of rapamycin regimen resulted in sustained graft survival and function in >90% of allogeneic recipients over a 100-d observation period. Long-term survival was associated with increased levels of intragraft transcripts for innate and adaptive immune regulatory factors, including IDO-1, arginase-1, Foxp3, TGF-β, IL-10, and decreased levels of proinflammatory T-bet, IL-1β, TNF-α, and IFN-γ as assessed on day 3 posttransplantation. T cells of long-term graft recipients generated a proliferative response to donor Ags at a similar magnitude to T cells of naive animals, suggestive of the localized nature of tolerance. Immunohistochemical analyses showed intense peri-islet infiltration of T regulatory cells in long-term grafts and systemic depletion of this cell population resulted in prompt rejection. The transient display of SA-PDL1 protein on the surface of islets serves as a practical means of localized immunomodulation that accomplishes sustained graft survival in the absence of chronic immunosuppression with potential clinical implications.

Type 1 diabetes pathogenesis and the role of inhibitory receptors in islet tolerance

Type 1 diabetes (T1D) affects over a million Americans, and disease incidence is on the rise. Despite decades of research, there is still no cure for this disease. Exciting beta cell replacement strategies are being developed, but in order for such approaches to work, targeted immunotherapies must be designed. To selectively halt the autoimmune response, researchers must first understand how this response is regulated and which tolerance checkpoints fail during T1D development. Herein, we discuss the current understanding of T1D pathogenesis in humans, genetic and environmental risk factors, presumed roles of CD4+ and CD8+ T cells as well as B cells, and implicated autoantigens. We also highlight studies in non-obese diabetic mice that have demonstrated the requirement for CD4+ and CD8+ T cells and B cells in driving T1D pathology. We present an overview of central and peripheral tolerance mechanisms and comment on existing controversies in the field regarding central tolerance. Finally, we discuss T cell- and B cell-intrinsic tolerance mechanisms, with an emphasis on the roles of inhibitory receptors in maintaining islet tolerance in humans and in diabetes-prone mice, and strategies employed to date to harness inhibitory receptor signaling to prevent or reverse T1D.

Landscape of Immune Checkpoint Inhibition in Carcinosarcoma (MMMT): Analysis of IDO-1, PD-L1 and PD-1

BACKGROUND

Carcinosarcoma (CS) or malignant mixed Müllerian tumor (MMMT), is a rare malignant biphasic tumor, which contains both a malignant epithelial and mesenchymal component. That being said, they have an aggressive clinical course. Given that immune checkpoint inhibitors have mustered significant excitement in the oncology world - immunotherapy could offer significant promise to this poor prognostic cancer subtype. A total of 75 carcinosarcoma cases were identified in our institutional database from 2010 to 2019 and immunohistochemistry for PD-L1, PD-1 and IDO-1 was performed. Out of the 75 patients, 65(87 %) demonstrated >1 % PD-1 expression and 50(67 %) expressed >1 % PD-L1 in either the tumoral and immune stromal components. 29 (39 %) cases demonstrated >20 % PD-1 expression and 14 (19 %) cases expressed >20 % PD-L1. 41(55 %) cases demonstrating co-expression of PD-1 and PD-L1. For IDO-1 64 (85 %) patients showed at least >5 %, while 34 (45 %) showed staining above 20 %. 45 patients (60 %) showed co-expression of IDO-1 and PD-L1, while 59 (79 %) patients had co-expression of IDO and PD-1 above 5 and 1 % respectively. Regarding clinicopathologcial features; older patients (> 65) were more likely to express PD-L1 (>1 %) and IDO-1 (>20 %). For tumor size, IDO-1 expression (>5 %), along with PD-1/IDO-1 Co-expression (>1/5 %), was associated with larger tumor size (>5cm). For myometrial invasion, CSs with >50 % invasion were more likely to express IDO-1 (>20 %) and PD-1/IDO-1 (>1/5 %). Ultimately, the effect of IDO-1, PD-1 and PD-L1 on the clinical profile may be less important than its potential use as a immunotherapeutic, where safe and effective corresponding drugs could be used to treat particular patient populations. Future clinical trials are needed to decipher the association between immune check point inhibitor expression and therapeutic response. This is the only way to definitively prove immune checkpoint immunohistochemistry as predictive biomarkers in this cancer subtype.

Role of the PD-1/PD-L1 Dyad in the Maintenance of Pancreatic Immune Tolerance for Prevention of Type 1 Diabetes

The human pancreas, like almost all organs in the human body, is immunologically tolerated despite the presence of innate and adaptive immune cells that promptly mediate protective immune responses against pathogens in situ. The PD-1/PD-L1 inhibitory pathway seems to play a key role in the maintenance of immune tolerance systemically and within the pancreatic tissue. Tissue resident memory T cells (TRM), T regulatory cells (Treg), macrophages and even β cells exhibit PD-1 or PD-L1 expression that contributes in controlling pancreatic immune homeostasis and tolerance. Dysregulation of the PD-1/PD-L1 axis as shown by animal studies and our recent experience with checkpoint inhibitory blockade in humans can lead to immune dysfunctions leading to chronic inflammatory disease and to type 1 diabetes (T1D) in genetically susceptible individuals. In this review, we discuss the role of the PD-1/PD-L1 axis in pancreatic tissue homeostasis and tolerance, speculate how genetic and environmental factors can regulate the PD-1/PD-L1 pathway, and discuss PD-1/PD-L1-based therapeutic approaches for pancreatic islet transplantation and T1D treatment.

[New Advances in the Treatment for Small Cell Lung Cancer]

Small cell lung cancer (SCLC) is a refractory cancer with high degree of malignancy, rapid disease progression, poor prognosis and easy recurrence. In the past 30 years, the traditional treatment of SCLC, mainly chemotherapy and radiotherapy, has not changed significantly, and the effective treatment method for clinical needs is extremely urgent. The rapid development of precision medicine has revealed the molecular biological characteristics of SCLC, so its diagnosis and treatment will into a new era. At present, some studies have shown that anti-angiogenic drugs, immunotherapy and so on have improved the efficacy of SCLC treatment to some extent, and there are more studies on the diagnosis and treatment of SCLC, so a new field of SCLC treatment are coming and bringing more survival benefits to patients. New studies on targeted therapy, anti-angiogenesis drugs and immunotherapy of molecular pathology of SCLC are emerging. This paper reviews the new diagnosis and treatment methods of SCLC to provide new guidance for its clinical treatment.
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Immune checkpoint inhibitors of PD-L1 as cancer therapeutics

Since the discovery of immune checkpoint proteins, there has been a special interest in developing antibodies that block programmed cell death 1 receptor (PD-1) and programmed cell death receptor ligand 1 (PD-L1) for a subset of cancer patients. PD-1 signaling negatively regulates T cell-mediated immune responses and serves as a mechanism for tumors to evade an antigen-specific T cell immunologic response. It plays a role in promoting cancer development and progression by enhancing tumor cell survival. With this background, PD-1 signaling represents a valuable therapeutic target for novel and effective cancer immunotherapy. Clinical data shows that blockade of this PD-1 signaling significantly enhance antitumor immunity, produce durable clinical responses, and prolong survival. Currently, there are three FDA-approved PD-L1 inhibitors for various malignancies ranging from non-small cell lung cancer to Merkel cell carcinoma. This review is to summarize many ongoing phase II/III trials of atezolizumab, durvalumab, avelumab, and new PD-L1 inhibitors in clinical developments. In particular, we focus on key trials that paved the pathway to FDA-approved indications for atezolizumab, durvalumab, and avelumab. Despite the popularity and accelerated FDA approval of PD-L1 inhibitors, further considerations into predictive biomarkers, mechanisms of resistance, treatment duration, immune-related toxicities, and PD-L1 expression threshold are needed to optimize anticancer potential in this class of immunotherapy.

Immune checkpoint inhibitors and type 1 diabetes mellitus: a case report and systematic review

OBJECTIVE

To better define the rare adverse event (AE) of diabetes mellitus associated with immune checkpoint inhibitors (ICIs).

DESIGN AND METHODS

We report the case of a lung cancer patient with diabetic ketoacidosis (DKA) and autoimmune thyroiditis during pembrolizumab treatment. We provide a systematic review of all published cases (PubMed/Web of Science/Cochrane, through November 2018) of autoimmune diabetes mellitus related to blockade of the cytotoxic T-lymphocyte antigen 4 (CTLA-4)-, programmed cell death 1 (PD-1) receptor or its ligand (PD-L1) or combination (ICI) therapy.

RESULTS

Our literature search identified 90 patient cases (our case excluded). Most patients were treated with anti-PD-1 or anti-PD-L1 as monotherapy (79%) or in combination with CTLA-4 blockade (15%). On average, diabetes mellitus was diagnosed after 4.5 cycles; earlier for combination ICI at 2.7 cycles. Early-onset diabetes mellitus (after one or two cycles) was observed during all treatment regimens. Diabetic ketoacidosis was present in 71%, while elevated lipase levels were detected in 52% (13/25). Islet autoantibodies were positive in 53% of patients with a predominance of glutamic acid decarboxylase antibodies. Susceptible HLA genotypes were present in 65% (mostly DR4). Thyroid dysfunction was the most frequent other endocrine AE at 24% incidence in this patient population.

CONCLUSION

ICI-related diabetes mellitus is a rare but often life-threatening metabolic urgency of which health-care professionals and patients should be aware. Close monitoring of blood glucose and prompt endocrine investigation in case of hyperglycemia is advisable. Predisposing factors such as HLA genotype might explain why some individuals are at risk.

Anti-PD-1 monoclonal antibody MEDI0680 in a phase I study of patients with advanced solid malignancies

BACKGROUND

The safety, efficacy, pharmacokinetics, and pharmacodynamics of the anti-programmed cell death-1 antibody MEDI0680 were evaluated in a phase I, multicenter, dose-escalation study in advanced solid malignancies.

METHODS

MEDI0680 was administered intravenously once every 2 weeks (Q2W) or once every 3 weeks at 0.1, 0.5, 2.5, 10 or 20 mg/kg. Two cohorts received 20 mg/kg once a week for 2 or 4 weeks, then 20 mg/kg Q2W. All were treated for 12 months or until progression. The primary endpoint was safety. Secondary endpoints were efficacy and pharmacokinetics. Exploratory endpoints included pharmacodynamics.

RESULTS

Fifty-eight patients were treated. Median age was 62.5 years and 81% were male. Most had kidney cancer (n = 36) or melanoma (n = 9). There were no dose-limiting toxicities. Treatment-related adverse events occurred in 83% and were grade ≥ 3 in 21%. Objective clinical responses occurred in 8/58 patients (14%): 5 with kidney cancer, including 1 with a complete response, and 3 with melanoma. The relationship between dose and serum levels was predictable and linear, with apparent receptor saturation at 10 mg/kg Q2W and all 20 mg/kg cohorts.

CONCLUSIONS

MEDI0680 induced peripheral T-cell proliferation and increased plasma IFNγ and associated chemokines regardless of clinical response. CD8+ T-cell tumor infiltration and tumoral gene expression of IFNG, CD8A, CXCL9, and granzyme K (GZMK) were also increased following MEDI0680 administration.

TRIAL REGISTRATION

NCT02013804 ; date of registration December 12, 2013.

Exosomal PD-L1 promotes tumor growth through immune escape in non-small cell lung cancer

Programmed cell death protein-1/programmed cell death ligand-1 (PD-1/PD-L1) pathway blockade is a promising new cancer therapy. Although PD-1/PD-L1 treatment has yielded clinical benefits in several types of cancer, further studies are required to clarify predictive biomarkers for drug efficacy and to understand the fundamental mechanism of PD-1/PD-L1 interaction between host and tumor cells. Here, we show that exosomes derived from lung cancer cells express PD-L1 and play a role in immune escape by reducing T-cell activity and promoting tumor growth. The abundance of PD-L1 on exosomes represented the quantity of PD-L1 expression on cell surfaces. Exosomes containing PD-L1 inhibited interferon-gamma (IFN-γ) secretion by Jurkat T cells. IFN-γ secretion was restored by PD-L1 knockout or masking on the exosomes. Both forced expression of PD-L1 on cells without PD-L1 and treatment with exosomes containing PD-L1 enhanced tumor growth in vivo. PD-L1 was present on exosomes isolated from the plasma of patients with non-small cell lung cancer, and its abundance in exosomes was correlated with PD-L1 positivity in tumor tissues. Exosomes can impair immune functions by reducing cytokine production and inducing apoptosis in CD8⁺ T cells. Our findings indicate that tumor-derived exosomes expressing PD-L1 may be an important mediator of tumor immune escape.

An immune suppressant protein expressed by non-small cell lung cancer cells (NSCLC) to facilitate tumor growth could be a valuable therapeutic target. NSCLC is often diagnosed at advanced stages, making treatment challenging. Therapies that inhibit an immune suppressant protein called programmed cell death ligand-1 (PD-L1) have shown promise for other cancers, but how PD-L1 interacts with host and tumor cells in NSCLC needs clarification. In experiments on human cell lines and mice, Jae Cheol Lee and Jin Kyung Rho at the University of Ulsan in Seoul, South Korea, and co-workers found that microvesicles (or ‘exosomes’) released by NSCLC cells carry PD-L1, which interacts with tumor-infiltrating immune cells, inhibiting their activity. The amount of PD-L1 in exosomes directly correlates with PD-L1 expression levels on tumor cell surfaces, providing a useful indication of disease activity.

The canonical TGF-β/Smad signalling pathway is involved in PD-L1-induced primary resistance to EGFR-TKIs in EGFR-mutant non-small-cell lung cancer

Background

Approximately 30% of patients with epidermal growth factor receptor (EGFR)-activating mutations have no response to EGFR-tyrosine kinase inhibitors (TKIs) (primary resistance). However, little is known about the molecular mechanism involved in primary resistance to EGFR-TKIs in EGFR-mutant non-small cell lung cancer (NSCLC). Programmed death ligand-1 (PD-L1) plays important regulatory roles in intracellular functions and leads to acquired resistance to EGFR-TKIs in NSCLC. Here, we investigated the mechanistic role of PD-L1 in primary resistance to EGFR-TKIs in EGFR-mutant NSCLC cells.

Methods

The expression levels of PD-L1 and the sensitivity to gefitinib in H1975, HCC827 and PC-9 cells were determined by quantitative real-time PCR analysis (qRT-PCR) and Cell Counting Kit-8 (CCK-8) assays, respectively. Molecular manipulations (silencing or overexpression) were performed to assess the effect of PD-L1 on sensitivity to gefitinib, and a mouse xenograft model was used for in vivo confirmation. Western blotting and qRT-PCR were used to analyse the expression of epithelial-mesenchymal transition (EMT) markers. The effect of PD-L1 on migratory and invasive abilities was evaluated using the Transwell assay and mice tail intravenous injection.

Results

Higher expression of PD-L1 was related to less sensitivity to gefitinib in EGFR-mutant NSCLC cell lines. The overexpression or knockdown of PD-L1 presented diametrical sensitivity to gefitinib in vitro and in vivo. Furthermore, the overexpression of PD-L1 led to primary resistance to gefitinib through the induction of EMT, which was dependent on the upregulation of Smad3 phosphorylation. Moreover, in the mouse model, the knockdown of PD-L1 inhibited transforming growth factor (TGF)-β1-induced cell metastasis in vivo.

Conclusion

PD-L1 contributes to primary resistance to EGFR-TKI in EGFR-mutant NSCLC cells, which may be mediated through the induction of EMT via the activation of the TGF-β/Smad canonical signalling pathway.

Cost-effectiveness of second-line atezolizumab in Canada for advanced non-small cell lung cancer (NSCLC)

Aim: To assess the cost-effectiveness in Canada of atezolizumab compared with docetaxel or nivolumab for the treatment of advanced NSCLC after first-line platinum-doublet chemotherapy. Materials and methods: A three-state partitioned-survival model was developed. Clinical inputs were obtained from the phase III OAK trial comparing atezolizumab with docetaxel in patients with advanced NSCLC who progressed after first-line platinum-doublet chemotherapy. Overall survival (OS) and progression-free survival (PFS) were extrapolated beyond the trial period using parametric models. A cure model assuming a 1% cure fraction was fitted to the OS data for atezolizumab. Outcomes for nivolumab were informed by a network meta-analysis (NMA) vs atezolizumab. Resource use and costs were informed by clinical expert opinion and published Canadian sources. Utility values were obtained from the OAK trial. The perspective of the analysis was that of the Canadian publicly-funded healthcare system. The base case time horizon was 10 years, and the discount rate was 1.5% annually for both costs and effects. Scenario analyses were performed to test the robustness of the results and all analyses were performed probabilistically. Results: Atezolizumab demonstrated a quality-adjusted life-year (QALY) gain of 0.60 compared with docetaxel at an incremental cost of $85,073, resulting in an incremental cost-effectiveness ratio (ICER) of $142,074/QALY. Atezolizumab dominated nivolumab (regardless of dosing regimen), based on modest differences in both QALYs and costs. Docetaxel was most likely to be cost effective at willingness-to-pay (WTP) thresholds below $125,000/QALY gained, while atezolizumab was most likely to be cost effective beyond this WTP threshold. In most scenario analyses, the results remained robust to changes in parameters. A reduced time horizon and alternative approaches to the NMA had the greatest impact on cost-effectiveness results. Conclusion: Atezolizumab represents a cost-effective therapeutic option in Canada for the treatment of patients with advanced NSCLC who progress after first-line platinum doublet chemotherapy.

A Model for Apoptotic-Cell-Mediated Adaptive Immune Evasion via CD80-CTLA-4 Signaling

Apoptotic cells carry a plethora of self-antigens but they suppress eliciting of innate and adaptive immune responses to them. How apoptotic cells evade and subvert adaptive immune responses has been elusive. Here, we propose a novel model to understand how apoptotic cells regulate T cell activation in different contexts, leading mostly to tolerogenic responses, mainly via taking control of the CD80-CTLA-4 coinhibitory signal delivered to T cells. This model may facilitate understanding of the molecular mechanisms of autoimmune diseases associated with dysregulation of apoptosis or apoptotic cell clearance, and it highlights potential therapeutic targets or strategies for treatment of multiple immunological disorders.

Recent advances in the clinical development of immune checkpoint blockade therapy

BACKGROUND

The discovery of immune checkpoint proteins and the mechanisms by which cancer cells utilize them to evade the immune system has transformed our approach to cancer immunotherapy. Checkpoint blockade antibodies targeting cytotoxic T lymphocyte antigen 4 (CTLA-4), programmed cell death 1 (PD-1) and its ligands such as programmed cell death ligand 1 (PD-L1) have already revolutionized the treatment of multiple types of cancer and have significantly improved treatment and survival outcomes of patients affected by these malignancies.

CONCLUSIONS

Herein, we summarize current knowledge about the role of, and the mechanisms underlying PD-1/PD-L1 signaling pathways in antitumor immune responses, with particular emphasis on clinical studies evaluating the efficacy of anti-PD-1/PD-L1 blockade in various tumor types. Preliminary clinical investigations with immune-checkpoint blockers highlight broad opportunities with a high potential to enhance antitumor immunity and, as such, to generate significant clinical responses. These preliminary successes open up new avenues towards efficient therapeutics offered to patients.

By Binding CD80 and CD86, the Vaccinia Virus M2 Protein Blocks Their Interactions with both CD28 and CTLA4 and Potentiates CD80 Binding to PD-L1

The vaccinia virus harbors in its genome several genes dedicated to the inhibition of the host immune response. Among them, M2L was reported to inhibit the intracellular NF-κB pathway. We report here several new putative immunosuppressive activities of M2 protein. M2 protein is secreted and binds cornerstone costimulatory molecules (CD80/CD86). M2 binding to CD80/CD86 blocks their interaction with soluble CD28/CTLA4 but also favors the soluble PD-L1-CD80 association. These findings open the way for new investigations deciphering the immune system effects of soluble M2 protein. Moreover, a vaccinia virus with a deletion of its M2L has been generated and characterized as a new oncolytic platform. The replication and oncolytic activities of the M2L-deleted vaccinia virus are indistinguishable from those of the parental virus. More investigations are needed to characterize in detail the immune response triggered against both the tumor and the virus by this M2-defective vaccinia virus.

In this article we report that the M2 protein encoded by the vaccinia virus is secreted as a homo-oligomer by infected cells and binds two central costimulation molecules, CD80 (B7-1) and CD86 (B7-2). These interactions block the ligation of the two B7 proteins to both soluble CD28 and soluble cytotoxic T-lymphocyte associated protein 4 (CTLA4) but favor the binding of soluble PD-L1 to soluble CD80. M2L gene orthologues are found in several other poxviruses, and the B7-CD28/CTLA4 blocking activity has been identified for several culture supernatants of orthopoxvirus-infected cells and for a recombinant myxoma virus M2 protein homolog (i.e., Gp120-like protein, or Gp120LP). Overall, these data indicate that the M2 poxvirus family of proteins may be involved in immunosuppressive activities broader than the NF-κB inhibition already reported (R. Gedey, X. L. Jin, O. Hinthong, and J. L. Shisler, J Virol 80:8676–8685, 2006, https://doi.org/10.1128/JVI.00935-06). A Copenhagen vaccinia virus with a deletion of the nonessential M2L locus was generated and compared with its parental virus. This M2L-deleted vaccinia virus, unlike the parental virus, does not generate interference with the B7-CD28/CTLA4/PD-L1 interactions. Moreover, this deletion did not affect any key features of the virus (in vitro replication, oncolytic activities in vitro and in vivo, and intratumoral expression of a transgene in an immunocompetent murine model). Altogether, these first results suggest that the M2 protein has the potential to be used as a new immunosuppressive biotherapeutic and that the M2L-deleted vaccinia virus represents an attractive new oncolytic platform with an improved immunological profile.

IMPORTANCE The vaccinia virus harbors in its genome several genes dedicated to the inhibition of the host immune response. Among them, M2L was reported to inhibit the intracellular NF-κB pathway. We report here several new putative immunosuppressive activities of M2 protein. M2 protein is secreted and binds cornerstone costimulatory molecules (CD80/CD86). M2 binding to CD80/CD86 blocks their interaction with soluble CD28/CTLA4 but also favors the soluble PD-L1-CD80 association. These findings open the way for new investigations deciphering the immune system effects of soluble M2 protein. Moreover, a vaccinia virus with a deletion of its M2L has been generated and characterized as a new oncolytic platform. The replication and oncolytic activities of the M2L-deleted vaccinia virus are indistinguishable from those of the parental virus. More investigations are needed to characterize in detail the immune response triggered against both the tumor and the virus by this M2-defective vaccinia virus.

Bacillus Calmette-Guérin Induces PD-L1 Expression on Antigen-Presenting Cells via Autocrine and Paracrine Interleukin-STAT3 Circuits

Bacillus Calmette-Guérin (BCG) is the only licensed vaccine for tuberculosis (TB), and is also used as an immunotherapy for bladder cancer and other malignancies due to its immunostimulatory properties. Mycobacteria spp., however, are well known for their numerous immune evasion mechanisms that limit the true potential of their therapeutic use. One such major mechanism is the induction of programmed death ligand-1 (PD-L1), which mitigates adaptive immune responses. Here, we sought to unravel the molecular pathways behind PD-L1 up-regulation on antigen-presenting cells (APCs) by BCG. We found that infection of APCs with BCG induced PD-L1 up-regulation, but that this did not depend on direct infection, suggesting a soluble mediator for this effect. BCG induced potent quantities of IL-6 and IL-10, and the downstream transcription factor STAT3 was hyper-phosphorylated. Intracellular analyses revealed that levels of PD-L1 molecules were associated with the STAT3 phosphorylation state, suggesting a causal link. Neutralisation of the IL-6 or IL-10 cytokine receptors dampened STAT3 phosphorylation and BCG-mediated up-regulation of PD-L1 on APCs. Pharmacological inhibition of STAT3 achieved the same effect, confirming an autocrine-paracrine cytokine loop as a mechanism for BCG-mediated up-regulation of PD-L1. Finally, an in vivo immunisation model showed that BCG vaccination under PD-L1 blockade could enhance antigen-specific memory CD4 T-cell responses. These novel findings could lead to refinement of BCG as both a vaccine for infectious disease and as a cancer immunotherapy.

Prospects and challenges of immunotherapy for pancreatic cancer

Pancreatic cancer is a highly malignant digestive system tumor with an extremely poor prognosis. It has been reported that pancreatic cancer has now surpassed breast cancer as the third leading cause of cancer death in the United States. Due to its low early diagnosis rate, most patients have lost the chance of surgery at the time of diagnosis. However, various treatment strategies (like radiotherapy, chemotherapy, targeted therapy, etc.) have not been able to significantly improve their survival rate. A large body of evidence suggests that an important cause of high lethality in pancreatic cancer is the immune privilege of tumors driven by factors such as immunosuppressive microenvironment, low T cell infiltration, and low gene mutation load. In recent years, tumor immunotherapy has become a hot spot in the field of oncology, and significant progress has been made in the treatment of pancreatic cancer. At present, various new immunotherapies such as immunological checkpoint blockers, adoptive cell therapy, and tumor vaccine have entered the clinical or preclinical stage, and all of them have hope to become a new treatment strategy to improve the treatment of patients with pancreatic cancer. Here, we briefly summarize the recent advances in immunotherapy for pancreatic cancer that is being researched and promising in recent years, as well as the challenges and prospects, with an aim to open up new horizons for the development of new and effective immunotherapy for pancreatic tumors.

Regulation of GVHD and GVL Activity via PD-L1 Interaction With PD-1 and CD80

Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for hematological malignancies (i.e. leukemia and lymphoma), because graft-versus-leukemia (GVL) activity mediated by alloreactive T cells can eliminate residual malignant cells and prevent relapse. However, the same alloreactive T cells also mediate a severe side effect, graft-versus-host disease (GVHD), and prevention of GVHD while preserving GVL activity remains an elusive goal. The immune checkpoint molecule PD-L1 and its interaction with PD-1 receptor in regulating cancer immunity is under intensive and wide-spread study, but knowledge about this interaction in regulating GVHD and GVL activity is very limited. In this review, we summarize the literature exploring how PD-L1 interaction with its receptors PD-1 and CD80 regulate GVHD and GVL activities, how PD-L1 signaling regulates T cell metabolic profiles, and how a differential role of PD-L1 interaction with PD-1, CD80 or both may provide a novel avenue to prevent GVHD while preserving strong GVL effects.

Treatment of advanced hepatocellular carcinoma: immunotherapy from checkpoint blockade to potential of cellular treatment

The absence of potent therapeutic option accounts for the dismal prognosis of advanced hepatocellular carcinoma (HCC) with high mortality and recurrence rate. For a decade, sorafenib is the only approved systemic drug in the first-line setting and warrants as the standard-of-care for HCC in the advanced stage. Given the common failures of chemotherapies and targeted therapies in the field of HCC treatment, promising breakthroughs were eagerly needed and until recently, immunotherapies have opened a new era of anticancer treatment. The liver organ is perceived as "immunotolerant" owing to its functional role, and the hepatic immune balance is found to be deregulated during chronic liver inflammation and HCC tumorigenesis. Restoring a competent immunity by mitigation of immunosuppression signals is a contemporary approach. In this regard, novel immune checkpoint inhibitors have revolutionized cancer pharmacological treatment options with remarkable clinical outcomes in hematologic malignancy and multiple solid tumors including advanced HCC. Nivolumab, an immunotherapeutic agent to block programmed cell death protein 1 (PD-1), showed high efficacy potential for patients progressed with sorafenib and granted accelerated approval by the US Food and Drug Administration (FDA) recently. The development of this class of immunotherapeutic drug is currently based on myriad studies established on the role of T-cell mediated immunosuppression through immune checkpoints. Heterogeneous results have led to further explorations to the profile of oncogenic processes and signaling pathways associated with PD1/PD-L1 axis. Emerging evidence from preclinical studies implicate natural killer (NK) cells as a mediator to the PD-1 checkpoint signaling immunoevasion. The strategy of adopting immunomodulating ability of NK cells by immune checkpoints inhibitors is potential to additive effects in stimulating anticancer immunity. This idea is not entirely newfound but has recently gained prominence because of advances in defining phenotypic heterogeneity of NK cell populations. The physiological significance and synergistic value of NK cells await further investigation in clinical trials. In this review, an overview of the treatment paradigm shift of HCC management is presented. Current knowledge concerning immunological mechanisms of immune checkpoints attributed to T cell is further discussed and relevant ongoing clinical trials are summarized. We proposed that NK cells should be viewed as part of the network of checkpoint immunoevasion and delineate current evidence of translational clinical research in this area. It is conceivable that immune checkpoint inhibitors in combination with NK cell-based therapeutic strategies will be great promise for treatment of advanced HCC.

PD-L1 expression on tumor cells associated with favorable prognosis in surgically resected esophageal squamous cell carcinoma

There is limited evidence regarding the relationship between programmed cell death ligand 1 (PD-L1) expression on tumor cells (TCs) and prognosis of esophageal squamous cell carcinoma (ESCC). This retrospective study aimed to investigate the clinical significance of PD-L1 expression in ESCC. To assess PD-L1 expression, we conducted immunohistochemistry studies using a tissue microarray encompassing 233 ESCC cases, stages I, II, and III, with detailed clinical data. PD-L1 expression on TCs was observed in 55.4% (129/233) of ESCC cases and was not associated with clinicopathological factors. ESCC patients with PD-L1-positive tumors showed significantly better overall survival and disease-free survival than did those with PD-L1-negative tumors (P = .023 and P = .026, respectively). When patients were stratified into those with stage I-II (127; 54.5%) and stage III (106; 45.5%) disease and those without (134; 57.5%) and with (99; 42.5%) lymph node metastasis, the prognostic effect was inconsistent. The overall survival and disease-free survival of patients with positive PD-L1 expression were significantly better in patients with stage I-II disease (P = .021 and P = .015, respectively) and without lymph node metastasis (P = .009 and P = .07, respectively) than their counterparts. Our results showed that PD-L1 expression on TCs was an independent predictor of prognosis of ESCC patients. However, the effect varied in patients with different stages and lymph node status. Positive PD-L1 expression was a favorable predictor in ESCC patients with stage I-II disease or without lymph node metastasis but not in patients with stage III disease or lymph node metastasis.

Immunomodulators targeting the PD-1/PD-L1 protein-protein interaction: From antibodies to small molecules

Cancer immunotherapy has made great strides in the recent decade, especially in the area of immune checkpoint blockade. The outstanding efficacy, prolonged durability of effect, and rapid assimilation of anti-PD-1 and anti-PD-L1 monoclonal antibodies in clinical practice have been nothing short of a medical breakthrough in the treatment of numerous malignancies. The major advantages of these therapeutic antibodies over their small molecule counterparts have been their high binding affinity and target specificity. However, antibodies do have their flaws including immune-related toxicities, inadequate pharmacokinetics and tumor penetration, and high cost burden to manufacturers and consumers. These limitations hinder broader clinical applications of the antibodies and have heightened interests in developing the alternative small molecule platform that includes peptidomimetics and peptides to target the PD-1/PD-L1 immune checkpoint system. The progress on these small molecule alternatives has been relatively slow compared to that of the antibodies. Fortunately, recent structural studies of the interactions among PD-1, PD-L1, and their respective antibodies have revealed key hotspots on PD-1 and PD-L1 that may facilitate drug discovery efforts for small molecule immunotherapeutics. This review is intended to discuss key concepts in immuno-oncology, describe the successes and shortcomings of PD-1/PD-L1 antibody-based therapies, and to highlight the recent development of small molecule inhibitors of the PD-1/PD-L1 protein-protein interaction.

Atezolizumab Treatment Beyond Progression in Advanced NSCLC: Results From the Randomized, Phase III OAK Study

INTRODUCTION

Cancer immunotherapy may alter tumor biology such that treatment effects can extend beyond radiographic progression. In the randomized, phase III OAK study of atezolizumab (anti-programmed death-ligand 1) versus docetaxel in advanced NSCLC, overall survival (OS) benefit with atezolizumab was observed in the overall patient population, without improvement in objective response rate (ORR) or progression-free survival (PFS). We examine the benefit-risk of atezolizumab treatment beyond progression (TBP).

METHODS

Eight hundred fifty patients included in the OAK primary efficacy analysis were evaluated. Atezolizumab was continued until loss of clinical benefit. Docetaxel was administered until Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) disease progression (PD)/unacceptable toxicity; no crossover to atezolizumab was allowed. ORR, PFS, post-PD OS, target lesion change, and safety were evaluated.

RESULTS

In atezolizumab-arm patients, ORR was 16% versus 14% and median PFS was 4.2 versus 2.8 months per immune-modified RECIST versus RECIST v1.1. The median post-PD OS was 12.7 months (95% confidence interval [CI]: 9.3-14.9) in 168 atezolizumab-arm patients continuing TBP, 8.8 months (95% CI: 6.0-12.1) in 94 patients switching to nonprotocol therapy, and 2.2 months (95% CI: 1.9-3.4) in 70 patients receiving no further therapy. Of the atezolizumab TBP patients, 7% achieved a post-progression response in target lesions and 49% had stable target lesions. Atezolizumab TBP was not associated with increased safety risks.

CONCLUSIONS

Within the limitations of this retrospective analysis, the post-PD efficacy and safety data from OAK are consistent with a positive benefit-risk profile of atezolizumab TBP in patients performing well clinically at the time of PD.

PD-L1 Binds to B7-1 Only In Cis on the Same Cell Surface

Programmed death ligand 1 (PD-L1)-mediated immunosuppression regulates peripheral tolerance and is often co-opted by tumors to evade immune attack. PD-L1 binds to PD-1 but also binds to B7-1 (CD80) to regulate T-cell function. The binding interaction of PD-L1 with B7-1 and its functional role need further investigation to understand differences between PD-1 and PD-L1 tumor immunotherapy. We examined the molecular orientation of PD-L1 binding to B7-1 using cell-to-cell binding assays, ELISA, and flow cytometry. As expected, PD-L1-transfected cells bound to PD-1-transfected cells, and B7-1 cells bound to CD28 or CTLA-4-transfected cells; however, PD-L1 cells did not bind to B7-1 cells. By ELISA and flow cytometry with purified proteins, we found PD-L1 and B7-1 had a strong binding interaction only when PD-L1 was flexible. Soluble PD-1 and B7-1 competed for binding to PD-L1. Binding of native PD-L1 and B7-1 in cis on the same cell surface was demonstrated with NanoBiT proximity assays. Thus, PD-L1-B7-1 interaction can occur in cis on the same cell but not in trans between two cells, which suggests a model in which PD-L1 can bend via its 11-amino acid, flexible stalk to bind to B7-1 in cis, in a manner that can competitively block the binding of PD-L1 to PD-1 or of B7-1 to CD28. This binding orientation emphasizes the functional importance of coexpression of PD-L1 and B7-1 on the same cell. We found such coexpression on tumor-infiltrating myeloid cells. Our findings may help better utilize these pathways in cancer immunotherapy. Cancer Immunol Res; 6(8); 921-9. ©2018 AACR.

Interferon-gamma drives programmed death-ligand 1 expression on islet β cells to limit T cell function during autoimmune diabetes

Type 1 diabetes is caused by autoreactive T cell-mediated β cell destruction. Even though co-inhibitory receptor programmed death-1 (PD-1) restrains autoimmunity, the expression and regulation of its cognate ligands on β cell remains unknown. Here, we interrogated β cell-intrinsic programmed death ligand-1 (PD-L1) expression in mouse and human islets. We measured a significant increase in the level of PD-L1 surface expression and the frequency of PD-L1+ β cells as non-obese diabetic (NOD) mice aged and developed diabetes. Increased β cell PD-L1 expression was dependent on T cell infiltration, as β cells from Rag1-deficient mice lacked PD-L1. Using Rag1-deficient NOD mouse islets, we determined that IFN-γ promotes β cell PD-L1 expression. We performed analogous experiments using human samples, and found a significant increase in β cell PD-L1 expression in type 1 diabetic samples compared to type 2 diabetic, autoantibody positive, and non-diabetic samples. Among type 1 diabetic samples, β cell PD-L1 expression correlated with insulitis. In vitro experiments with human islets from non-diabetic individuals showed that IFN-γ promoted β cell PD-L1 expression. These results suggest that insulin-producing β cells respond to pancreatic inflammation and IFN-γ production by upregulating PD-L1 expression to limit self-reactive T cells.

A Network Meta-analysis Comparing the Efficacy and Safety of Anti-PD-1 with Anti-PD-L1 in Non-small Cell Lung Cancer

Background: This network meta-analysis aimed at comparing anti-programmed death 1 (anti-PD-1) with anti-programmed death ligand 1(anti-PD-L1) immunotherapy in patients with metastatic, previously treated non-small cell lung cancer (NSCLC) who failed first-line treatment.

Methods: We searched electronic databases to identify all eligible clinical trials. End-points included overall survival (OS), progression-free survival (PFS) and objective response. Hazard ratios (HRs) or odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were extracted. Network meta-analysis was performed using the frequentist approach for multiple treatment comparisons.

Results: In total, 3024 patients were randomly assigned: 1117 received anti-PD-1 therapy (nivolumab + pembrolizumab), 569 received anti-PD-L1 (atezolizumab) and 1338 received docetaxel. Anti-PD-1 (HR, 0.56; 95% CI, 0.48-0.66) and anti-PD-L1 (HR, 0.64; 95% CI, 0.51-0.79) achieved better OS than docetaxel, and anti-PD-1 was superior to docetaxel in terms of PFS (HR, 0.75; 95% CI, 0.62-0.89). Moreover, anti-PD-1 achieved the highest effect on OS and PFS, with a P-score of 91.2% and 95.5%, respectively. With regard to tumor response, anti-PD-1 group had a higher rate of responders than that in anti-PD-L1 (HR, 0.35; 95% CI, 0.19-0.65) and docetaxel (HR, 0.36; 95% CI, 0.25-0.52) groups. Undoubtedly, anti-PD-1 and anti-PD-L1 obtained less toxicity profile than docetaxel, and no significant difference was observed between anti-PD-1 and anti-PD-L1 groups.

Conclusions: Anti-PD-1 may be a better choice for patients with metastatic and previously treated NSCLC who failed first-line treatment in terms of the treatment ranking.

Combination Immunotherapy Approaches for Pancreatic Cancer Treatment

Pancreatic ductal adenocarcinoma is a lethal malignant disease with a very low medium survival. Currently, metastatic pancreatic cancer poorly responds to conventional treatments and exhibits an acute resistance to most chemotherapy. Few approaches have been shown to be effective for metastatic pancreatic cancer treatment. Novel therapeutic approaches to treat patients with pancreatic adenocarcinoma are in great demand. Last decades, immunotherapies have been evaluated in clinical trials and received great success in many types of cancers. However, it has very limited success in treating pancreatic cancer. As pancreatic cancer poorly responds to many single immunotherapeutic agents, combination immunotherapy was introduced to improve efficacy. The combination therapies hold great promise for enhancing immune responses to achieve better therapeutic effects. This review summarizes the existing and potential combination immunotherapies for the treatment of pancreatic cancer.

Prognostic value of PD-L1 in esophageal squamous cell carcinoma: a meta-analysis

Accumulated evidence has shown that the programmed cell death receptor 1/programmed cell death receptor 1 ligand 1 (PD-1/PD-L1) pathway is a promising therapeutic target for cancer immunotherapy. However, the association between PD-L1 and esophageal squamous cell carcinoma (ESCC) patient survival remains unclear. We performed a meta-analysis to investigate the prognostic value of PD-L1 in ESCC. We searched PubMed, Embase, Web of Knowledge, and Cochrane Central Register of Controlled Trials databases for relevant studies that evaluated PD-L1 expression and ESCC patient survival. Fixed- and random-effects meta-analyses were conducted according to the heterogeneity of the included studies. Sensitivity analysis was performed according to Metan-based influence analysis. Publication bias was evaluated using Egger's and Begg's tests. Overall, 13 studies with 2,877 patients were included. Twelve studies demonstrated the association between overall survival (OS), and 6 studies described the relation between disease-free survival (DFS). PD-L1 overexpression was found in 43.7% (1,258 of 2,877) of the patients with ESCC. High PD-L1 expression was associated with distant metastasis in patients with ESCC (P = 0.04). Moreover, high PD-L1 expression was significantly associated with poor OS (hazard ratio [HR] 1.38, 95% confidence interval [CI] = 1.02-1.86, P = 0.04) and especially in Asian populations (HR 1.49, 95% CI = 1.11-1.99, P = 0.008). But it did not have an impact on disease-free survival (HR 1.15, 95% CI = 0.76-1.74, P = 0.52). Further well-designed clinical studies with uniform assessment approaches for PD-L1 expression are warranted to verify its prognostic value.

RSAD2 and AIM2 Modulate Coxsackievirus A16 and Enterovirus A71 Replication in Neuronal Cells in Different Ways That May Be Associated with Their 5' Nontranslated Regions

Coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) are closely related enteroviruses that cause the same hand, foot, and mouth disease (HFMD), but neurological complications occur only very rarely in CV-A16 compared to EV-A71 infections. To elucidate host responses that may be able to explain these differences, we performed transcriptomic analysis and real-time quantitative PCR (RT-qPCR) in CV-A16-infected neuroblastoma cells (SK-N-SH), and the results showed that the radical S-adenosylmethionine domain containing 2 (RSAD2) was the highest upregulated gene in the antimicrobial pathway. Increased RSAD2 expression was correlated with reduced viral replication, while RSAD2 knockdown cells were correlated with increased replication. EV-A71 replication showed no apparent correlation to RSAD2 expressions. Absent in melanoma 2 (AIM2), which is associated with pyroptotic cell death, was upregulated in EV-A71-infected neurons but not in CV-A16 infection, suggesting that the AIM2 inflammasome played a significant role in suppressing EV-A71 replication. Chimeric viruses derived from CV-A16 and EV-A71 but containing swapped 5' nontranslated regions (5' NTRs) showed that RSAD2 expression/viral replication and AIM2 expression/viral replication patterns may be linked to the 5' NTRs of parental viruses. Differences in secondary structure of internal ribosomal entry sites within the 5' NTR may be responsible for these findings. Overall, our results suggest that CV-A16 and EV-A71 elicit different host responses to infection, which may help explain the apparent lower incidence of CV-A16-associated neurovirulence in HFMD outbreaks compared to EV-A71 infection.IMPORTANCE Although coxsackievirus A16 (CV-A16) and enterovirus A17 (EV-A71) both cause hand, foot, and mouth disease, EV-A71 has emerged as a leading cause of nonpolio, enteroviral fatal encephalomyelitis among young children. The significance of our research is in the identification of the possible differing and novel mechanisms of CV-A16 and EV-A71 inhibition in neuronal cells that may impact viral neuropathogenesis. We further showed that viral 5' NTRs may play significant roles in eliciting different host response mechanisms.

Affinity purification mass spectrometry analysis of PD-1 uncovers SAP as a new checkpoint inhibitor

Programmed cell death-1 (PD-1) is an essential inhibitory receptor in T cells. Antibodies targeting PD-1 elicit durable clinical responses in patients with multiple tumor indications. Nevertheless, a significant proportion of patients do not respond to anti-PD-1 treatment, and a better understanding of the signaling pathways downstream of PD-1 could provide biomarkers for those whose tumors respond and new therapeutic approaches for those whose tumors do not. We used affinity purification mass spectrometry to uncover multiple proteins associated with PD-1. Among these proteins, signaling lymphocytic activation molecule-associated protein (SAP) was functionally and mechanistically analyzed for its contribution to PD-1 inhibitory responses. Silencing of SAP augmented and overexpression blocked PD-1 function. T cells from patients with X-linked lymphoproliferative disease (XLP), who lack functional SAP, were hyperresponsive to PD-1 signaling, confirming its inhibitory role downstream of PD-1. Strikingly, signaling downstream of PD-1 in purified T cell subsets did not correlate with PD-1 surface expression but was inversely correlated with intracellular SAP levels. Mechanistically, SAP opposed PD-1 function by acting as a molecular shield of key tyrosine residues that are targets for the tyrosine phosphatase SHP2, which mediates PD-1 inhibitory properties. Our results identify SAP as an inhibitor of PD-1 function and SHP2 as a potential therapeutic target in patients with XLP.

Stromal PD-L1-Positive Regulatory T cells and PD-1-Positive CD8-Positive T cells Define the Response of Different Subsets of Non-Small Cell Lung Cancer to PD-1/PD-L1 Blockade Immunotherapy

INTRODUCTION

Inhibition of programmed cell death-1 (PD-1) and its ligand programmed death ligand 1 (PD-L1) by using an immune checkpoint inhibitor has emerged as a promising immunotherapy for NSCLC. The correlation of PD-L1 expression in tumor cells with treatment outcomes has been reported in many pivotal trials; however, the relationship remains unclear. Here, we demonstrate that those patients with both high density of PD-1-positive CD8 and PD-L1-positive CD4-positive CD25-positive (PD-1^hi PD-L1^hi) regulatory T cells (Tregs) have a better response to PD1/PD-L1 blockade.

METHODS

In our study between April 1, 2014, and May 30, 2017, a total of 73 NSCLC peripheral blood samples and fresh tumor specimens were collected for study. Of these, 42 large (10-mm³) fresh tumor specimens were obtained from surgical procedures and checked for expression of immunology biomarkers, including PD-L1, PD-1, CD8, CD4, and CD25, in tumor cells and tumor-infiltrating lymphocytes (TILs) by flow cytometry, immunohistochemistry, and immunofluorescence (IF). Moreover, 31 small biopsy specimens from patients who received immunotherapy (pembrolizumab or nivolumab) were analyzed by immunohistochemistry and IF. The correlation between flow cytometry and IF detected for TILs' density was evaluated by Spearman's rank correlation test; the primary end point was progression-free survival. For the PD-1/PD-L1 blockade assay, the TILs and peripheral blood mononuclear CD8 T cells were cultured (1×10⁵ per well) with anti-PD-1 (clone MIH4), anti-PD-L1 (clone MIH1). The cytotoxic activity of TILs in killing NSCLC cells after stimulation by anti-PD-1 and anti-PD-L1 was measured by a conventional ⁵¹Cr release assay.

RESULTS

We first identified a population of high-PD-L1-expressing CD25-positive CD4-positive T cells (PD-L1^hi Tregs) in the tumor microenvironment. The frequency of PD-L1^hi Tregs was higher in tumor tissue (mean 48.6 ± 14.3% in CD25-positive CD3-positive CD4-positive T cells) than in blood (mean 35.4 ± 10.2% in CD25-positive CD3-positive CD4-positive T cells) and normal tissue (mean 38.6 ± 9.7% in CD25-positive CD3-positive CD4-positive T cells) (p < 0.05), as determined by flow cytometry. The frequency of PD-L1^hi Tregs was positively correlated with PD-1-positive CD8 in Tregs. In addition, the TILs from these patients (PD-1^hi PD-L1^hi) showed PD-1/PD-L1 pathway dependence and could induce a greater killing effect of TILs by PD-1/PD-L1 blockade treatment. The patients with PD-L1-positive NSCLC with PD-1^hi PD-L1^hi TILs showed a better clinical outcome than those with a low frequency of PD-1^hi CD8 or PD-L1^hi Tregs (median progression-free survival not reached versus 2 months).

CONCLUSIONS

Our findings suggested that the density of PD-L1-positive CD4-positive CD25-positive Tregs in the tumor microenvironment can serve as a diagnostic factor to supplement PD-L1 expression in tumor cells and predict the response to PD-1/PD-L1 blockade immunotherapy in NSCLC.

Therapeutic Antibodies in Cancer Therapy

The therapeutic arsenal in solid tumors comprises different anticancer strategies with diverse chemotherapeutic agents and a growing number of biological substances. Large clinical study-based chemotherapeutic protocols combined with biologicals have become an important component in (neo-) adjuvant therapy alongside surgery in solid cancers as well as radiation therapy in some instances. In recent years, monoclonal antibodies have entered the mainstream of cancer therapy. Their first use was as antagonists of oncogenic receptor tyrosine kinases, but today monoclonal antibodies have emerged as long-sought vehicles for the targeted delivery of potent chemotherapeutic agents and as powerful tools to manipulate anticancer immune responses. There is a growing number of FDA approved monoclonal antibodies and small molecules targeting specific types of cancer suggestive of the clinical relevance of this approach.Targeted cancer therapies , also referred to as personalized medicine, are being studied for use alone, in combination with other targeted therapies, and in combination with chemotherapy. The use of monoclonal antibodies in colorectal and gastric cancer for example have shown best outcome when combined with chemotherapy, even though single agent anti-EGFR antibodies seem to be active in particular setting of metastatic colorectal cancer patients. However, it is not well defined whether the addition of anti-VEGF - and anti-EGFR strategies to chemotherapy could improve outcome in those patients susceptible to colorectal cancer-related metastases resection. Among the most promising approaches to activating therapeutic antitumor immunity is the blockade of immune checkpoints, exemplified by the recently FDA-approved agent, Ipilimumab, an antibody that blocks the coinhibitory receptor CTLA-4. Capitalizing on the success of Ipilimumab, agents that target a second coinhibitory receptor, PD-1, or its ligand, PD-L1, are in clinical development. This section attempts to discuss recent progress of targeted agents and in tackling a more general target applicable to gastrointestinal cancer .

Patterns of PD-1, PD-L1, and PD-L2 expression in pediatric solid tumors

BACKGROUND

Significant antitumor effects have been observed in a variety of malignancies via blockade of immune checkpoints. Interaction of programmed death 1 (PD-1) with its ligands PD-L1 and PD-L2 suppresses T-cell function and restricts immune-mediated tumor killing. We examined expression of these proteins in children with solid tumors, as expression may serve as biomarkers of response to this class of drugs.

METHODS

Sections cut from formalin-fixed paraffin-embedded (FFPE) tissue blocks were processed and evaluated for PD-1, PD-L1, and PD-L2 by immunohistochemistry (IHC) as well as by mRNA expression. A semiquantitative 0-5 IHC scoring system (0 = negative to 5 = very high) was applied, with scores incorporating combined prevalence of tumor cell and nontumor cell labeling. Expression profiling was performed using the NanoString nCounter™ system. Data analysis was performed using quantile normalization. All quantile-normalized data underwent subsequent log10 transformation.

RESULTS

One hundred twenty-four FFPE blocks were included in the analysis. PD-1, PD-L1, and PD-L2 IHC were not evaluable in 8, 0, and 12 blocks, respectively. PD-1, PDL-1, and PDL-2 expression was negative to moderate by both IHC (range 0-3) and mRNA expression (range 0-2.62). Correlation between IHC score and mRNA expression was poor for all three tested proteins (PD-1, r² = 0.06; PDL-1, r² = 0.007; and PDL-2, r² = 0.15).

CONCLUSIONS

Expression of PD-1, PD-L1, and PD-L2 is low in pediatric solid tumors. At low levels of expression, IHC score and mRNA expression correlate poorly. Current and planned clinical trials will determine whether this low level of expression predicts limited response to immune checkpoint inhibitors.

CD80 Expressed by CD8+ T Cells Contributes to PD-L1-Induced Apoptosis of Activated CD8+ T Cells

Tumor cells are capable of limiting antitumor CD8⁺ T cell responses through their cell surface expression of PD-L1. In addition to PD-1 expressed by CD8⁺ T cells, PD-L1 also binds to CD80 expressed by CD8⁺ T cells. The influence of the PD-L1/CD80 interaction on CD8⁺ T cell function has not been fully characterized, so we sought to investigate the impact of the PD-L1/CD80 interaction on PD-L1-induced apoptosis of activated CD8⁺ T cells. We found that CD8⁺ T cells that lacked CD80 expression got activated to the same extent as wild-type CD8⁺ T cells, but when cultured with anti-CD3 and PD-L1/Fc protein, activated CD8⁺ T cells that lacked CD80 expression survived better than activated wild-type CD8⁺ T cells. These findings indicate that PD-L1 induces apoptosis in activated CD8⁺ T cells in part by signaling through CD80. Thus, in the design and implementation of checkpoint blockade therapies that target PD-L1, it is essential that both binding partners for PD-L1, PD-1, and CD80 are considered.

Immune Checkpoint Inhibitor-Associated Type 1 Diabetes Mellitus: Case Series, Review of the Literature, and Optimal Management

With the introduction of immune checkpoint inhibitors into clinical practice, various autoimmune toxicities have been described. Antibodies targeting the receptor:ligand pairing of programmed death receptor-1 (PD-1) and its cognate ligand programmed death-ligand 1 (PD-L1) in rare reports have been associated with autoimmune diabetes mellitus. We report 2 cases of rapid-onset, insulin-dependent, type 1 diabetes mellitus in the setting of administration of nivolumab, a fully human monoclonal antibody to PD-1, and atezolizumab, a humanized monoclonal antibody to PD-L1. This appears to be the first report of autoimmune diabetes mellitus associated with atezolizumab. In addition, we provide a brief review of similar cases reported in the literature and a discussion of potential mechanisms for this phenomenon and propose a diagnostic and treatment algorithm.

PD-L1 inhibitors in the pipeline: Promise and progress

Checkpoint inhibitors have improved survival for patients with melanoma, non-small-cell lung cancer (NSCLC), bladder, head and neck and other cancers. Antibodies against PD-L1, including atezolizumab, avelumab and durvalumab, are also being developed and have been approved for various cancers. Compared with anti-CTLA-4 drugs, studies with anti-PD-1/PD-L1 agents have suggested higher response rates and improved survival. Targeting PD-L1 rather than PD-1 may also theoretically offer further benefit, with the potential for improved efficacy and reduced toxicity, although this has not been clearly shown by clinical experience to date. Anti-PD-L1 agents have shown good efficacy and manageable toxicity in several tumor types.

Determination of PD-L1 expression in effusions from mesothelioma by immuno-cytochemical staining

BACKGROUND

Malignant mesothelioma (MM) is an aggressive, fatal tumor. Current therapeutic options only marginally improve survival. Programmed cell death ligand 1 (PD-L1) is a dominant mediator of immunosuppression, binding to programmed cell death 1 (PD-1). PD-L1 is up-regulated in cancer cells, and the PD-1/PD-L1 pathway plays a critical role in tumor immune evasion, thus providing a target for antitumor therapy. Further, a correlation between PD-L1 expression and prognosis has been reported. Studies performed on histological material have revealed expression of PD-L1 in MM, but no study has been performed on MM effusions thus far.

METHODS

PD-L1 expression was determined by a commercially available antibody (clone 28-8) in 74 formalin-fixed, paraffin-embedded cell blocks from body effusions obtained at diagnosis from patients with MM. The presence of MM cells was confirmed with CK5/6, calretinin, and EMA and the admixture of macrophages was assessed with CD68. Only cases containing more than 100 tumor cells were assessed. Membranous staining in tumor cells was considered positive. Survival time was calculated from the appearance of the first malignant effusion until death.

RESULTS

Reactivity was observed in 23 of 61 (38%) of cases and was classified as ≥1%-5% (n = 9 cases), >5%-10% (n = 4 cases), >10%-50% (n = 4 cases), and >50% (n = 6 cases) positive cells. Survival times did not differ significantly between patients with PD-L1-positive and PD-L1-negative tumors.

CONCLUSION

MM effusions are suitable for immune-cytochemical assessment of PD-L1 expression in malignant cells and the results are similar to those reported for histological specimens. Cancer Cytopathol 2017;125:908-17. © 2017 American Cancer Society.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

PD-L1 induced by IFN-γ from tumor-associated macrophages via the JAK/STAT3 and PI3K/AKT signaling pathways promoted progression of lung cancer

BACKGROUND

Interferon-γ (IFN-γ) is conventionally regarded as an inflammatory cytokine that has a pivotal role in anti-infection and tumor immune surveillance. It has been used clinically to treat a variety of malignancies. However, increased evidence has suggested IFN-γ can act to induce tumor progression. The role of IFN-γ in regulating antitumor immunity appears to be complex and paradoxical. The mechanism underlying the dual aspects of IFN-γ function in antitumor immunity is not clear.

METHODS

(1) Lung cancer cells (A549 cells) were cultured with pleural effusion or supernatant of tumor-associated macrophages (TAMs supernatant), and the expression levels of PD-L1 were detected by flow cytometer. The invasion capacity was measured in vitro using trans-well migration assays. (2) Pleural effusion mononuclear cells (PEMC) were separated by Ficoll Hypaque gradient. The expression of interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α, and INF-γ in the tumor-associated macrophages was analyzed by flow cytometry. (3) A549 cells were stimulated with IL-6, IL-10, TNF-α, or IFN-γ and then the expression levels were detected by flow cytometry. (4) The expression levels of phospho-ERK (p-ERK), phospho-AKT (p-AKT), and phospho-Sat3 (p-Stat3) were analyzed with Western blot after stimulation with IFN-γ. (5) Cotreatment of the A549 cells with MAPK/ERK-specific inhibitor PD98059, PI3K/AKT-specific inhibitor LY294002, or JAK/STAT3-specific inhibitor AG490, respectively, blocked IFN-γ-induced PD-L1 expression, and then PD-L1 expression was detected by flow cytometry.

RESULTS

We demonstrated that TAMs could induce the expression of PD-L1 by the secretion of IFN-γ through the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway and the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway in A549 cells. Furthermore, the signal pathway blockers LY294002 or AG490 could block the induced expression of PD-L1 by IFN-γ.

CONCLUSIONS

IFN-γ was not always successful as an antitumor agent. It also can promote tumor cells to evade immune surveillance. Researchers should be cautious in using IFN-γ as a therapeutic agent for cancer treatment.

Folic acid-functionalized polyethylenimine superparamagnetic iron oxide nanoparticles as theranostic agents for magnetic resonance imaging and PD-L1 siRNA delivery for gastric cancer

Programmed death ligand-1 (PD-L1), which is highly expressed in gastric cancers, interacts with programmed death-1 (PD-1) on T cells and is involved in T-cell immune resistance. To increase the therapeutic safety and accuracy of PD-1/PD-L1 blockade, RNA interference through targeted gene delivery was performed in our study. We developed folic acid (FA)- and disulfide (SS)–polyethylene glycol (PEG)-conjugated polyethylenimine (PEI) complexed with superparamagnetic iron oxide Fe₃O₄ nanoparticles (SPIONs) as a siRNA-delivery system for PD-L1 knockdown. The characterization, binding ability, cytotoxicity, transfection efficiency, and cellular internalization of the polyplex were determined. At nitrogen:phosphate (N:P) ratios of 10 or above, the FA-PEG-SS-PEI-SPIONs bound to PD-L1 siRNA to form a polyplex with a diameter of approximately 120 nm. Cell-viability assays showed that the polyplex had minimal cytotoxicity at low N:P ratios. The FA-conjugated polyplex showed higher transfection efficiency and cellular internalization in the folate receptor-overexpressing gastric cancer cell line SGC-7901 than a non-FA-conjugated polyplex. Subsequently, we adopted the targeted FA-PEG-SS-PEI-SPION/siRNA polyplexes at an N:P ratio of 10 for function studies. Cellular magnetic resonance imaging (MRI) showed that the polyplex could also act as a T₂-weighted contrast agent for cancer MRI. Furthermore, one of four PD-L1 siRNAs exhibited effective PD-L1 knockdown in PD-L1-overexpressing SGC-7901. To determine the effects of the functionalized polyplex on T-cell function, we established a coculture model of activated T cells and SGC-7901 cells and demonstrated changes in secreted cytokines. Our findings highlight the potential of this class of multifunctional theranostic nanoparticles for effective targeted PD-L1-knockdown therapy and MRI diagnosis in gastric cancers.

AIM2 Inflammasome-Mediated Pyroptosis in Enterovirus A71-Infected Neuronal Cells Restricts Viral Replication

Encephalomyelitis is a well-known complication of hand, foot, and mouth disease (HFMD) due to Enterovirus 71 (EV71) infection. Viral RNA/antigens could be detected in the central nervous system (CNS) neurons in fatal encephalomyelitis but the mechanisms of neuronal cell death is not clearly understood. We investigated the role of absent in melanoma 2 (AIM2) inflammasome in neuronal cell death, and its relationship to viral replication. Our transcriptomic analysis, RT-qPCR, Western blot, immunofluorescence and flow cytometry studies consistently showed AIM2 gene up-regulation and protein expression in EV-A71-infected SK-N-SH cells. Downstream AIM2-induced genes, CARD16, caspase-1 and IL-1β were also up-regulated and caspase-1 was activated to form cleaved caspase-1 p20 subunits. As evidenced by 7-AAD positivity, pyroptosis was confirmed in infected cells. Overall, these findings have a strong correlation with decreases in viral titers, copy numbers and proteins, and reduced proportions of infected cells. AIM2 and viral antigens were detected by immunohistochemistry in infected neurons in inflamed areas of the CNS in EV-A71 encephalomyelitis. In infected AIM2-knockdown cells, AIM2 and related downstream gene expressions, and pyroptosis were suppressed, resulting in significantly increased virus infection. These results support the notion that AIM2 inflammasome-mediated pyroptosis is an important mechanism of neuronal cell death and it could play an important role in limiting EV-A71 replication.