PD-L2 is predominantly expressed by Th2 cells

Comparison of Clinical Trial Results of the Recently Approved Immunotherapeutic Drugs for Advanced Biliary Tract Cancers

The recently approved immunotherapeutic drugs are Keytruda (pembrolizumab) and Imfinzi (durvalumab) for advanced biliary tract cancers that inhibit PD-1 receptor and PD-L1 ligand, respectively. In this perspective, the results of the two clinical trials, i.e., TOPAZ-1 (NCT03875235) and KEYNOTE-966 (NCT04003636), are critically appraised, compared, and discussed to assess the benefits of these two drugs in the context of the treatment of advanced biliary tract cancers with a focus on PD-L1 status and MIS (microsatellite instability) status and therapy responsiveness in the subgroups. Analyzing the PD-L2 status in biliary tract cancer patients can aid in assessing the prognostic value of PD-L2 expression in determining the clinical response and this may aid in appropriate patient stratification.

KYNU-related transcriptome profile and clinical outcome from 2994 breast tumors

The Catabolism of tryptophan modulates the immunosuppressive microenvironment in tumors. KYNU (Kynureninase) served as an enzyme involved in amino acid tryptophan catabolism through the kynurenine pathway. The molecular and clinical characteristics of KYNU remain unclear, and the impact of KYNU on the immune response has not been reported until now. We analyzed large-scale transcriptome data and related clinical information on 2994 breast cancer patients to characterize KYNU's role in breast cancer. There was a strong correlation between KYNU expression and major molecular and clinical characteristics, and it was more likely to be overexpressed in patients with higher malignancy subtypes. Inflammatory and immune responses were strongly correlated with KYNU. KYNU was also associated with immune modulators at the pan-cancer level, particularly its potential synergistic role with other immune checkpoints in breast cancer. KYNU expression was linked to the malignancy grade of breast cancer and predicted poorer outcomes. Tryptophan catabolism might play an important role in modulating the tumor immune microenvironment through KYNU. More significantly, KYNU might synergize with CTLA4, PDL2, IDO1, and other immune checkpoints, contributing to the development of combination cancer immunotherapy targeting KYNU and other checkpoints. As far as we are aware, this is the biggest and most thorough study describing KYNU's role in breast cancer.

PD-L1 Over-Expression Varies in Different Subtypes of Lung Cancer: Will This Affect Future Therapies?

Programmed death-ligand (PD-L) 1 and 2 are ligands of programmed cell death 1 (PD-1) receptor. They are members of the B7/CD28 ligand-receptor family and the most investigated inhibitory immune checkpoints at present. PD-L1 is the main effector in PD-1-reliant immunosuppression, as the PD-1/PD-L pathway is a key regulator for T-cell activation. Activation of T-cells warrants the upregulation of PD-1 and production of cytokines which also upregulate PD-L1 expression, creating a positive feedback mechanism that has an important role in the prevention of tissue destruction and development of autoimmunity. In the context of inadequate immune response, the prolonged antigen stimulation leads to chronic PD-1 upregulation and T-cell exhaustion. In lung cancer patients, PD-L1 expression levels have been of special interest since patients with non-small cell lung cancer (NSCLC) demonstrate higher levels of expression and tend to respond more favorably to the evolving PD-1 and PD-L1 inhibitors. The Food and Drug Administration (FDA) has approved the PD-1 inhibitor, pembrolizumab, alone as front-line single-agent therapy instead of chemotherapy in patients with NSCLC and PD-L1 ≥1% expression and chemoimmunotherapy regimens are available for lower stage disease. The National Comprehensive Cancer Network (NCCN) guidelines also delineate treatment by low and high expression of PD-L1 in NSCLC. Thus, studying PD-L1 overexpression levels in the different histological subtypes of lung cancer can affect our approach to treating these patients. There is an evolving role of immunotherapy in the other sub-types of lung cancer, especially small cell lung cancer (SCLC). In addition, within the NSCLC category, squamous cell carcinomas and non-G12C KRAS mutant NSCLC have no specific targetable therapies to date. Therefore, assessment of the PD-L1 expression level among these subtypes of lung cancer is required, since lung cancer is one of the few malignances wherein PD-L1 expression levels is so crucial in determining the role of immunotherapy. In this study, we compared PD-L1 expression in lung cancer according to the histological subtype of the tumor.

PD-L1 and PD-L2 expression in pancreatic ductal adenocarcinoma and their correlation with immune infiltrates and DNA damage response molecules

Immunotherapy targeting programmed cell death‐1 (PD‐1) has considerably improved the prognosis of patients with advanced cancers; however, its efficacy in the treatment of pancreatic ductal adenocarcinoma (PDAC) is unfavourable. To address the issue of PDAC immunotherapy, we investigated the expression of two PD‐1 ligands, PD‐L1 and PD‐L2, in PDAC, analysed their role in survival, and explored their correlation with clinicopathological features, immune infiltration, and DNA damage response molecules. Immunohistochemistry was performed on 291 surgically resected PDAC samples. In tumour cells (TCs) and immune cells (ICs), the positivity of PD‐L1 expression was 30 and 20% and that of PD‐L2 expression was 40 and 20%, respectively. Moreover, PD‐L1 expression on TCs correlated with its expression on ICs (p < 0.0001); a similar result was observed for PD‐L2 (p < 0.0001). Nonetheless, no correlation was observed between PD‐L1 and PD‐L2 expression. Positive PD‐L1 expression on TCs was related to N1 stage (p = 0.011) and AJCC II stage (p = 0.002), whereas positive PD‐L2 expression on TCs was associated with high FOXP3⁺ cell infiltration (p = 0.001) and high BRCA2 expression (p < 0.0001). Survival analysis revealed that positive PD‐L1 (p = 0.046) and PD‐L2 (p = 0.028) expression on TCs was an independent risk factor for unfavourable disease‐specific survival (DSS). Furthermore, positive PD‐L2 expression on TCs was an independent risk factor for lower DSS in the pN0 (p = 0.023), moderate and well tumour differentiation (p = 0.004), low BRCA1 (p = 0.017), wild‐type p53 (p = 0.034), and proficient mismatch repair (p = 0.004) subgroups. Moreover, post‐operative adjuvant chemotherapy could significantly affect DSS, regardless of PD‐L1/PD‐L2 expression status (positive or negative) on TCs, while it only prolonged DSS in PDL1‐ICs⁽⁻⁾ (p < 0.0001) and PDL2‐ICs⁽⁻⁾ (p < 0.0001) subgroups. This study provides a comprehensive understanding of the roles of PD‐L1 and PD‐L2 in PDAC, supporting anti‐PD‐1 axis immunotherapy for PDAC.

The Role of Long Non-Coding RNAs in the Tumor Immune Microenvironment

Tumorigenesis is a complicated process caused by successive genetic and epigenetic alterations. The past decades demonstrated that the immune system affects tumorigenesis, tumor progression, and metastasis. Although increasing immunotherapies are revealed, only a tiny proportion of them are effective. Long non-coding RNAs (lncRNAs) are a class of single-stranded RNA molecules larger than 200 nucleotides and are essential in the molecular network of oncology and immunology. Increasing researches have focused on the connection between lncRNAs and cancer immunotherapy. However, the in-depth mechanisms are still elusive. In this review, we outline the latest studies on the functions of lncRNAs in the tumor immune microenvironment. Via participating in various biological processes such as neutrophil recruitment, macrophage polarization, NK cells cytotoxicity, and T cells functions, lncRNAs regulate tumorigenesis, tumor invasion, epithelial-mesenchymal transition (EMT), and angiogenesis. In addition, we reviewed the current understanding of the relevant strategies for targeting lncRNAs. LncRNAs-based therapeutics may represent promising approaches in serving as prognostic biomarkers or potential therapeutic targets in cancer, providing ideas for future research and clinical application on cancer diagnosis and therapies.

The Potential Advantage of Targeting Both PD-L1/PD-L2/PD-1 and IL-10-IL-10R Pathways in Acute Myeloid Leukemia

Tumor cells promote the suppression of host anti-tumor type 1 T cell responses by various mechanisms, including the upregulation of surface inhibitory molecules such as programmed death ligand (PD-L)-1, and the production of immunosuppressive cytokines such as interleukin-10 (IL-10). There are over 2000 trials investigating PD-L1 and/or its receptor programmed-death 1 (PD-1) blockade in cancer, leading to the approval of PD-1 or PD-L1 inhibitors in several types of solid cancers and in hematological malignancies. The available data suggest that the molecule PD-L1 on antigen-presenting cells suppresses type 1 T cell immune responses such as cytotoxicity, and that the cytokine IL-10, in addition to downregulating immune responses, increases the expression of inhibitory molecule PD-L1. We hypothesize that the manipulation of both the co-inhibitory network (with anti-PD-L1 blocking antibodies) and suppressor network (with anti-IL-10 blocking antibodies) is an attractive immunotherapeutic intervention for acute myeloid leukemia (AML) patients ineligible for standard treatment with chemotherapy and hematopoietic stem cell transplantation, and with less severe adverse reactions. The proposed combination of these two immunotherapies represents a new approach that can be readily translated into the clinic to improve the therapeutic efficacy of AML disease treatment.

Neutralization of PD-L2 is Essential for Overcoming Immune Checkpoint Blockade Resistance in Ovarian Cancer

PURPOSE

Ovarian cancer represents a major clinical hurdle for immune checkpoint blockade (ICB), with reported low patient response rates. We found that the immune checkpoint ligand PD-L2 is robustly expressed in patient samples of ovarian cancers and other malignancies exhibiting suboptimal response to ICB but not in cancers that are ICB sensitive. Therefore, we hypothesize that PD-L2 can facilitate immune escape from ICB through incomplete blockade of the PD-1 signaling pathway.

EXPERIMENTAL DESIGN

We engineered a soluble form of the PD-1 receptor (sPD-1) capable of binding and neutralizing both PD-L2 and PD-L1 with ×200 and ×10,000 folds improvement in binding affinity over wild-type PD-1 leading to superior inhibition of ligand-mediated PD-1 activities.

RESULTS

Both in vitro and in vivo analyses performed in this study demonstrated that the high-affinity sPD-1 molecule is superior at blocking both PD-L1- and PD-L2-mediated immune evasion and reducing tumor growth in immune-competent murine models of ovarian cancer.

CONCLUSIONS

The data presented in this study provide justification for using a dual targeting, high-affinity sPD-1 receptor as an alternative to PD-1 or PD-L1 therapeutic antibodies for achieving superior therapeutic efficacy in cancers expressing both PD-L2 and PD-L1.

Spatially Resolved and Quantitative Analysis of the Immunological Landscape in Human Meningiomas

The immunological status of human meningiomas is not well understood, hindering the development of rational immunotherapeutic strategies. We measured the levels of PD-L1, PD-L2, and immune cell subsets using multiplex quantitative immunofluorescence in a tissue microarray composed of 73 human meningiomas (56 WHO Grade 1, 13 WHO Grade 2, and 4 WHO Grade 3). We analyzed tumor-infiltrating immune cell populations, T-cell activation/dysfunction, and macrophage phenotypes. PD-L1 and PD-L2 were detected in 5.8% and 68.7% of cases, respectively. There was a higher PD-L1 expression in CD68+ macrophages compared with tumor cells (p < 0.001). There was a weak positive correlation between PD-L1 expression and CD3+ T-cell infiltration. The level of CD3+ cells and T-cell activation/proliferation in human meningiomas were highly variable with an increased CD4-to-CD8 ratio in higher grade tumors (p < 0.05). There was a stronger correlation between GZMB/Ki67 with PD-L2 than PD-L1. We found that 15.23%, 6.66%, and 5.49% of macrophages were CD163+, CD68+, and CD163+CD68+, respectively. In cases where there is high CD3+ T-cell infiltration, 23.5% and 76.5% had dormant and activated T-cell phenotypes, respectively. We conclude that human meningiomas are either PD-L1low TILlow or PD-L1low TILhigh tumors and harbor variable TIL infiltration and phenotypes.

Significance of PD1 Alternative Splicing in Celiac Disease as a Novel Source for Diagnostic and Therapeutic Target

Background

We have focused on the alteration of the PD-1/PD-L1 pathway in celiac disease and discussed the roles of the PD1 pathway in regulating the immune response. We explored the idea that the altered mRNA splicing process in key regulatory proteins could represent a novel source to identify diagnostic, prognostic, and therapeutic targets in celiac disease.

Methods

We characterized the PD1 mRNA variants' profile in CD patients and in response to gluten peptides' incubation after in vitro experiments. Total RNA from whole blood was isolated, and the coding region of the human PD-1 mRNA was amplified by cDNA PCR.

Results

PCR amplification of the human PD-1 coding sequence revealed an association between the over-expression of the sPD-1 protein and the PD-1Δex3 transcript in celiac disease. Thus, we have found three novel alternative spliced isoforms, two of which result in a truncated protein and the other isoform with a loss of 14 aa of exon 2 and complete exon 3 (Δ3) which could encode a new soluble form of PD1 (sPD-1).

Conclusions

Our study provides evidence that dietary gluten can modulate processes required for cell homeostasis through the splicing of pre-mRNAs encoding key regulatory proteins, which represents an adaptive mechanism in response to different nutritional conditions.

Emerging concepts in PD-1 checkpoint biology

The PD-1 pathway is a cornerstone in immune regulation. While the PD-1 pathway has received considerable attention for its role in contributing to the maintenance of T cell exhaustion in chronic infection and cancer, the PD-1 pathway plays diverse roles in regulating host immunity beyond T cell exhaustion. Here, we discuss emerging concepts in the PD-1 pathway, including (1) the impact of PD-1 inhibitors on diverse T cell differentiation states including effector and memory T cell development during acute infection, as well as T cell exhaustion during chronic infection and cancer, (2) the role of PD-1 in regulating Treg cells, NK cells, and ILCs, and (3) the functions of PD-L1/B7-1 and PD-L2/RGMb/neogenin interactions. We then discuss the emerging use of neoadjuvant PD-1 blockade in the treatment of early-stage cancers and how the timing of PD-1 blockade may improve clinical outcomes. The diverse binding partners of PD-1 and its associated ligands, broad expression patterns of the receptors and ligands, differential impact of PD-1 modulation on cells depending on location and state of differentiation, and timing of PD-1 blockade add additional layers of complexity to the PD-1 pathway, and are important considerations for improving the efficacy and safety of PD-1 pathway therapeutics.

A Tumor-Specific Super-Enhancer Drives Immune Evasion by Guiding Synchronous Expression of PD-L1 and PD-L2

PD-L1 and PD-L2 are important targets for immune checkpoint blockade, but how tumor cells achieve their expression remains to be addressed. Here, we find that PD-L1 and PD-L2 are co-expressed in cancer cell lines and tissues across different cancer types. In breast cancer, MDA-MB-231 and SUM-159 cells show high expression of both PD-L1 and PD-L2. The expression of both PD-L1 and PD-L2 is greatly reduced upon treatment of inhibitors of super-enhancers. Bioinformatic analysis identifies a potential super-enhancer (PD-L1L2-SE) that is located between the CD274 and CD273 genes. Genetic deletion of PD-L1L2-SE profoundly reduces the expression of PD-L1 and PD-L2. PD-L1L2-SE-deficient cancer cells fail to generate immune evasion and are sensitive to T cell-mediated killing. Notably, epigenetic activation of such a region (PD-L1L2-SE) is correlated with PD-L1 and PD-L2. Taken together, we identify a super-enhancer (PD-L1L2-SE) that is responsible for the overexpression of PD-L1 and PD-L2 as well as immune evasion in cancer.

Differential Accumulation and Activation of Monocyte and Dendritic Cell Subsets in Inflamed Synovial Fluid Discriminates Between Juvenile Idiopathic Arthritis and Septic Arthritis

Despite their distinct etiology, several lines of evidence suggest that innate immunity plays a pivotal role in both juvenile idiopathic arthritis (JIA) and septic arthritis (SA) pathophysiology. Indeed, monocytes and dendritic cells (DC) are involved in the first line of defense against pathogens and play a critical role in initiating and orchestrating the immune response. The aim of this study was to compare the number and phenotype of monocytes and DCs in peripheral blood (PB) and synovial fluid (SF) from patients with JIA and SA to identify specific cell subsets and activation markers associated with pathophysiological mechanisms and that could be used as biomarkers to discriminate both diseases. The proportion of intermediate and non-classical monocytes in the SF and PB, respectively, were significantly higher in JIA than in SA patients. In contrast the proportion of classical monocytes and their absolute numbers were higher in the SF from SA compared with JIA patients. Higher expression of CD64 on non-classical monocyte was observed in PB from SA compared with JIA patients. In SF, higher expression of CD64 on classical and intermediate monocyte as well as higher CD163 expression on intermediate monocytes was observed in SA compared with JIA patients. Moreover, whereas the number of conventional (cDC), plasmacytoid (pDC) and inflammatory (infDC) DCs was comparable between groups in PB, the number of CD141⁺ cDCs and CD123⁺ pDCs in the SF was significantly higher in JIA than in SA patients. CD14⁺ infDCs represented the major DC subset in the SF of both groups with potent activation assessed by high expression of HLA-DR and CD86 and significant up-regulation of HLA-DR expression in SA compared with JIA patients. Finally, higher activation of SF DC subsets was monitored in SA compared with JIA with significant up-regulation of CD86 and PDL2 expression on several DC subsets. Our results show the differential accumulation and activation of innate immune cells between septic and inflammatory arthritis. They strongly indicate that the relative high numbers of CD141⁺ cDC and CD123⁺ pDCs in SF are specific for JIA while the over-activation of DC and monocyte subsets is specific for SA.

The PD-1/PD-L pathway in rheumatic diseases

BACKGROUND/PURPOSE

Autoimmune diseases are diseases in which the body produces an abnormal immune response to self-antigens and damages its own tissues. Programmed death-1 (PD-1) and its ligands (PD-Ls) have been discovered to be important negative regulators of the immune system, playing crucial roles in autoimmunity.

METHODS

We analyzed the existing scientific literature dealing with this issue. In this review, the PD-1/PD-L pathway in the genetic susceptibility to and pathogenesis of rheumatic diseases is discussed. The PD-1/PD-L pathway might be helpful for diagnosing, evaluating the disease activity of and treating rheumatic diseases.

RESULTS

PD-1/PD-L gene polymorphisms are associated with a genetic predisposition to rheumatic disorders, which can provide reference information for diagnosis and disease activity. The conclusion of the crucial role of the PD-1/PD-L pathway in the pathogenesis of rheumatic diseases is consistent, but the details remain controversial. In some animal models, manipulating the PD-1/PD-L pathway could decrease disease severity. PD-1/PD-Ls may enable us to develop new therapeutics for patients with rheumatic diseases in the future.

CONCLUSION

The PD-1/PD-L pathway plays crucial roles in rheumatic disease. More work is needed to provide a better mechanistic understanding of the PD-1/PD-L pathway and to facilitate the precise therapeutic manipulation of this pathway.

Circulating PD-1 mRNA in Peripheral Blood is a Potential Biomarker for Predicting Survival of Breast Cancer Patients

BACKGROUND

Programmed cell death 1 (PD-1) inhibitors have shown significant therapeutic promise in various cancers. However, the clinical significance of PD-1 expression remains not fully understood. In this study, we evaluated the clinical and prognostic relevance of PD-1 expression in breast cancer (BC).

METHODS

First, we analyzed PD-1 mRNA expression in BC tissues and performed a survival analysis using a dataset from The Cancer Genome Atlas. Next, we measured PD-1 mRNA expression in peripheral blood (PB) in BC patients by quantitative reverse-transcription polymerase chain reaction. We performed a survival analysis and evaluated the association between PD-1 mRNA expression in PB and the clinicopathological features of 372 BC patients who underwent curative resection. Flow cytometry (FCM) analysis was performed to identify PD-1-expressing cells in PB. Finally, we determined whether there was a correlation of PD-1 mRNA expression in PB and tumor tissue.

RESULTS

PD-1 mRNA expression was significantly higher in tumor tissues compared with normal tissues. Decreased PD-1 mRNA expression in tumor tissue was associated with poor overall survival (OS). PD-1 mRNA expression in PB of BC patients was higher than that of healthy volunteers, and increased PD-1 mRNA expression in PB was associated with poor OS. FCM revealed that PD-1 was mostly expressed on T cells in PB, predominantly in CD4⁺ T cells. PD-1 mRNA expression in PB was negatively correlated with PD-1 mRNA expression in tumor tissue.

CONCLUSION

High expression of PD-1 mRNA in preoperative PB could serve as an effective biomarker that indicates poor prognosis in BC.

Regulation of PD-1/PD-L1 Pathway in Cancer by Noncoding RNAs

Immune checkpoint blockade has demonstrated significant anti-tumor immunity in an array of cancer types, yet the underlying regulatory mechanism of it is still obscure, and many problems remain to be solved. As an inhibitory costimulatory signal of T-cells, the programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) pathway can paralyze T-cells at the tumor site, enabling the immune escape of tumor cells. Although many antibodies targeting PD-1/PD-L1 have been developed to block their interaction for the treatment of cancer, the reduced response rate and resistance to the therapies call for further comprehension of this pathway in the tumor microenvironment. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are two main types of noncoding RNAs that play critical parts in the regulation of immune response in tumorigenesis, including the PD-1/PD-L1 pathway. Here we summarize the most recent studies on the control of this pathway by noncoding RNAs in cancer and hopefully will offer new insights into immune checkpoint blockade therapies.

Identification of a monoclonal antibody that targets PD-1 in a manner requiring PD-1 Asn58 glycosylation

Programmed cell death 1 (PD-1) is inhibitory receptor and immune checkpoint protein. Blocking the interaction of PD-1 and its ligands PD-L1/ L2 is able to active T-cell-mediated antitumor response. Monoclonal antibody-based drugs targeting PD-1 pathway have exhibited great promise in cancer therapy. Here we show that MW11-h317, an anti-PD-1 monoclonal antibody, displays high affinity for PD-1 and blocks PD-1 interactions with PD-L1/L2. MW11-h317 can effectively induce T-cell-mediated immune response and inhibit tumor growth in mouse model. Crystal structure of PD-1/MW11-h317 Fab complex reveals that both the loops and glycosylation of PD-1 are involved in recognition and binding, in which Asn58 glycosylation plays a critical role. The unique glycan epitope in PD-1 to MW11-h317 is different from the first two approved clinical PD-1 antibodies, nivolumab and pembrolizumab. These results suggest MW11-h317 as a therapeutic monoclonal antibody of PD-1 glycosylation-targeting which may become efficient alternative for cancer therapy.

Expression of Programmed Cell Death-Ligands in Hepatocellular Carcinoma: Correlation With Immune Microenvironment and Survival Outcomes

The quantity of programmed cell death-ligand 1 (PD-L1) is regarded as a predicting factor of clinical response to anti-PD-1 axis immunotherapy. However, the expression of PD-L1 and its prognostic value in hepatocellular carcinoma (HCC) patients remain debated. Meanwhile, the molecular features of PD-1's other ligand, namely PD-L2, as well as its correlation with clinicopathological parameters and HCC tumor microenvironment (TME), are still poorly understood. In this study, immunohistochemistry (IHC) data from 304 HCC patients were used to determine the clinicopathological features of PD-L1 and PD-L2 and their correlation with CD8⁺ T cells in HCC. Moreover, fresh clinical HCC samples were used to identify the immune cell subtypes expressing PD-L1 and PD-L2. By using The Cancer Genome Atlas (TCGA) dataset, we further assessed the correlation between mutation signature, copy number variation (CNV), number of neoepitopes, immune gene expression, immune/stromal cell infiltration to the expression of PD-L1 and PD-L2. While membrane expression of PD-L2 was observed in 19.1% of tumor samples, no obvious expression of PD-L1 was detected on tumor cell membranes. High expression of PD-L2 on tumor membranes and PD-L1 in immune stroma were both significantly associated with poorer overall survival (OS) and disease-free survival (DFS) outcomes. Flow cytometry analysis and immunofluorescence showed that macrophages were the main immune cell subtype expressing both PD-L1 and PD-L2. Moreover, positive expression of PD-Ls was correlated with higher CD8⁺ T cells infiltration in immune stroma. CNV analysis showed a similarity between PD-L1 and PD-L2 in affecting gene expression. In addition, higher levels of PD-Ls correlated with higher expression of immune related genes, enhanced cytolytic activity, and larger proportions of immune/stromal cell infiltration. Collectively, our study reveals the impact of both PD-L1 and PD-L2 on the HCC tumor microenvironment for the first time, providing insight for new therapeutic options.

Clinicopathological significance and prognostic implication of programmed death-1 ligand 2 expression in colorectal cancer

PURPOSE

The aim of this study was to evaluate the clinicopathological significance and prognostic role of programmed death-1 ligand 2 (PD-L2) expression in colorectal cancer according to intratumoral components.

METHODS

We used immunohistochemical analysis to investigate the impact of PD-L2 expression on clinicopathological characteristics and survival in 264 human colorectal cancer tissues. We also evaluated the correlation between PD-L2 expression and PD-L1 expression.

RESULTS

PD-L2 was expressed in 17.4% of the tumors (T-PD-L2) and in 19.3% of the immune cells (I-PD-L2) of the 264 CRC tissues. I-PD-L2 expression was significantly correlated with favorable tumor behaviors, including lower pathologic tumor stage, less lymph node metastasis, less distant metastasis, and lower pathologic tumor node metastasis stage. There was no significant correlation between I-PD-L2 expression and T-PD-L2 expression (P = 0.091). However, I-PD-L2 expression was correlated with PD-L1 expression in the immune cells (P < 0.001). There was also a significant correlation between high Immunoscore and I-PD-L2, but not T-PD-L2 (P < 0.001 and P = 0.190, respectively). The prognosis was better for patients who expressed I-PD-L2 than for patients who did not. In patients who expressed I-PD-L2, there was a significant difference in the survival rate between subgroups according to the presence or absence of T-PD-L2 expression.

CONCLUSIONS

Our results suggest that I-PD-L2 expression is significantly correlated with favorable tumor behaviors and better survival rates. There is also a significant correlation between PD-L2 expression and PD-L1 expression in immune cells.

Prognostic significance of PD-L2 expression in patients with oral squamous cell carcinoma-A comparison to the PD-L1 expression profile

BACKGROUND

Despite the observed association of increased PD-L1 expression in peripheral blood of oral squamous cell carcinoma (OSCC) patients with histomorphologic parameters, the role of the PD1 ligands-PD-L1 and PD-L2-is insufficiently understood. Aim of the study was to investigate whether the alterations of PD-L1 and PD-L2 expression in blood are associated with survival and could serve as immune monitoring parameter. Moreover, it should be analyzed if PD-L2 is differentially expressed in tissue and blood samples of OSCC patients compared to healthy controls and if there is an association of PD-L2 expression with histomorphologic and prognostic tumor parameters.

METHODS

PD-L2 mRNA expression was analyzed in tumors and healthy oral mucosa specimens and in corresponding peripheral blood samples of 48 OSCC patients and 26 healthy controls using RT-qPCR. A cutoff point (COP) was determined and a chi-square test (χ² test) was carried out. Survival analysis of PD-L2 and previously reported PD-L1 expression data was performed using Kaplan-Meier analysis (Log-rank test).

RESULTS

PD-L2 expression in tissue samples was significantly (P < 0.001) higher in OSCC patients compared to healthy controls. A significant association of PD-L2 expression above the COP (positive) with malignancy was ascertained (P < 0.001). A significant (P = 0.01) association of previously reported PD-L1 expression rates in peripheral blood with survival could be shown.

CONCLUSION

Peripheral blood PD-L1 expression might be a prognostic marker for OSCC patients and a possible parameter to monitor immune dysfunction in malign diseases. In the peripheral blood, PD-L1 might be more relevant for immune tolerance than PD-L2. Local PD-L2 expression in tissue samples might be useful as a diagnostic parameter for malignancy and could contribute to the immunosuppressive local microenvironment in OSCC.

PD-L2 Expression in Human Tumors: Relevance to Anti-PD-1 Therapy in Cancer

Purpose: Tumor-associated PD-L1 expression is predictive of clinical response to PD-1-directed immunotherapy. However, PD-L1-negative patients may also respond to PD-1 checkpoint blockade, suggesting that other PD-1 ligands may be relevant to the clinical activity of these therapies. The prevalence of PD-L2, the other known ligand of PD-1, and its relationship to response to anti-PD-1 therapy were evaluated.Experimental Design: PD-L2 expression was assessed in archival tumor tissue from seven indications using a novel immunohistochemical assay. In addition, relationships between clinical response and PD-L2 status were evaluated in tumor tissues from patients with head and neck squamous cell carcinoma (HNSCC) with recurrent or metastatic disease, treated with pembrolizumab.Results: PD-L2 expression was observed in all tumor types and present in stromal, tumor, and endothelial cells. The prevalence and distribution of PD-L2 correlated significantly with PD-L1 (P = 0.0012-<0.0001); however, PD-L2 was detected in the absence of PD-L1 in some tumor types. Both PD-L1 and PD-L2 positivity significantly predicted clinical response to pembrolizumab on combined tumor, stromal and immune cells, with PD-L2 predictive independent of PD-L1. Response was greater in patients positive for both PD-L1 and PD-L2 (27.5%) than those positive only for PD-L1 (11.4%). PD-L2 status was also a significant predictor of progression-free survival (PFS) with pembrolizumab independent of PD-L1 status. Longer median times for PFS and overall survival were observed for PD-L2-positive than PD-L2-negative patients.Conclusions: Clinical response to pembrolizumab in patients with HNSCC may be related partly to blockade of PD-1/PD-L2 interactions. Therapy targeting both PD-1 ligands may provide clinical benefit in these patients. Clin Cancer Res; 23(12); 3158-67. ©2017 AACR.

Transcriptional Landscape of Human Tissue Lymphocytes Unveils Uniqueness of Tumor-Infiltrating T Regulatory Cells

Tumor-infiltrating regulatory T lymphocytes (Treg) can suppress effector T cells specific for tumor antigens. Deeper molecular definitions of tumor-infiltrating-lymphocytes could thus offer therapeutic opportunities. Transcriptomes of T helper 1 (Th1), Th17, and Treg cells infiltrating colorectal or non-small-cell lung cancers were compared to transcriptomes of the same subsets from normal tissues and validated at the single-cell level. We found that tumor-infiltrating Treg cells were highly suppressive, upregulated several immune-checkpoints, and expressed on the cell surfaces specific signature molecules such as interleukin-1 receptor 2 (IL1R2), programmed death (PD)-1 Ligand1, PD-1 Ligand2, and CCR8 chemokine, which were not previously described on Treg cells. Remarkably, high expression in whole-tumor samples of Treg cell signature genes, such as LAYN, MAGEH1, or CCR8, correlated with poor prognosis. Our findings provide insights into the molecular identity and functions of human tumor-infiltrating Treg cells and define potential targets for tumor immunotherapy.

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Transcriptome analysis performed on tumor-resident CD4⁺ Th1, Th17, and Treg cells

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Tumor-infiltrating Treg cells are defined by the expression of signature genes

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Treg-specific signature genes correlate with patients’ survival in both CRC and NSCLC

Immune checkpoint blockade: the role of PD-1-PD-L axis in lymphoid malignancies

The co-inhibitory receptor programmed cell death (PD)-1, expressed by immune effector cells, is credited with a protective role for normal tissue during immune responses, by limiting the extent of effector activation. Its presently known ligands, programmed death ligands (PD-Ls) 1 and 2, are expressed by a variety of cells including cancer cells, suggesting a role for these molecules as an immune evasion mechanism. Blocking of the PD-1-PD-L signaling axis has recently been shown to be effective and was clinically approved in relapsed/refractory tumors such as malignant melanoma and lung cancer, but also classical Hodgkin’s lymphoma. A plethora of trials exploring PD-1 blockade in cancer are ongoing. Here, we review the role of PD-1 signaling in lymphoid malignancies, and the latest results of trials investigating PD-1 or PD-L1 blocking agents in this group of diseases. Early phase studies proved very promising, leading to the clinical approval of a PD-1 blocking agent in Hodgkin’s lymphoma, and Phase III clinical studies are either planned or ongoing in most lymphoid malignancies.

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.

Checkpoint inhibitors in lung cancer: latest developments and clinical potential

Lung cancer is the leading cause of cancer death in the United States. The vast majority of patients are diagnosed with metastatic disease with a 5-year survival rate of less than 5%. After first-line chemotherapy or biomarker-matched targeted therapy, only suitable for a small group of patients, further systemic therapy options rendered very limited, if any, benefit until recently. Checkpoint inhibitors have significantly improved outcomes in patients with metastatic non-small cell lung cancer (NSCLC) and are currently an established second-line therapeutic option. In this manuscript, we review the mechanism of action of checkpoint inhibitors, present the available data with approved and experimental agents, discuss the progress that has already been made in the field, as well as toxicity awareness, and future perspectives.

Immunotherapy for lung cancer

Treatment of lung cancer remains a challenge, and lung cancer is still the leading cause of cancer-related mortality. Immunotherapy has previously failed in lung cancer but has recently emerged as a very effective new therapy, and there is now growing worldwide enthusiasm in cancer immunotherapy. We summarize why immune checkpoint blockade therapies have generated efficacious and durable responses in clinical trials and why this has reignited interest in this field. Cancer vaccines have also been explored in the past with marginal success. Identification of optimal candidate neoantigens may improve cancer vaccine efficacy and may pave the way to personalized immunotherapy, alone or in combination with other immunotherapy such as immune checkpoint blockade. Understanding the steps in immune recognition and eradication of cancer cells is vital to understanding why previous immunotherapies failed and how current therapies can be used optimally. We hold an optimistic view for the future prospect in lung cancer immunotherapy.

PD-1/PD-L1 blockades in non-small-cell lung cancer therapy

Lung cancer is the leading cause of cancer death in males and the second leading cause of death in females worldwide. Non-small-cell lung cancer (NSCLC) is the main pathological type of lung cancer, and most newly diagnosed NSCLC patients cannot undergo surgery because the disease is already locally advanced or metastatic. Despite chemoradiotherapy and targeted therapy improving clinical outcomes, overall survival remains poor. Immune checkpoint blockade, especially blockade of programmed death-1 (PD-1) receptor and its ligand PD-L1, achieved robust responses and improved survival for patients with locally advanced/metastatic NSCLC in preclinical and clinical studies. However, with regard to PD-1/PD-L1 checkpoint blockade as monotherapy or in combination with other antitumor therapies, such as chemotherapy, radiotherapy (including conventional irradiation and stereotactic body radiotherapy), and target therapy, there are still many unknowns in treating patients with NSCLC. Despite this limited understanding, checkpoint blockade as a novel therapeutic approach may change the treatment paradigm of NSCLC in the future. Here we review the main results from completed and ongoing studies to investigate the feasibility of PD-1/PD-L1 inhibitors, as monotherapy or combinatorial agents in patients with locally advanced and metastatic NSCLC, and explore optimal strategy in such patients.

A novel regulation of PD-1 ligands on mesenchymal stromal cells through MMP-mediated proteolytic cleavage

Whether fibroblasts regulate immune response is a crucial issue in the modulation of inflammatory responses. Herein, we demonstrate that foreskin fibroblasts (FFs) potently inhibit CD3⁺ T cell proliferation through a mechanism involving early apoptosis of activated T cells. Using blocking antibodies, we demonstrate that the inhibition of T cell proliferation occurs through cell-to-cell interactions implicating PD-1 receptor expressed on T cells and its ligands, PD-L1 and PD-L2, on fibroblasts. Dual PD-1 ligand neutralization is required to abrogate (i) binding of the PD-1-Fc fusion protein, (ii) early apoptosis of T cells, and (iii) inhibition of T cell proliferation. Of utmost importance, we provide the first evidence that PD-1 ligand expression is regulated through proteolytic cleavage by endogenous matrix metalloproteinases (MMPs) without transcriptional alteration during culture-time. Using (i) different purified enzymatic activities, (ii) MMP-specific inhibitors, and (iii) recombinant human MMP-9 and MMP-13, we demonstrated that in contrast to CD80/CD86, PD-L1 was selectively cleaved by MMP-13, while PD-L2 was sensitive to broader MMP activities. Their cleavage by exogenous MMP-9 and MMP-13 with loss of PD-1 binding domain resulted in the reversion of apoptotic signals on mitogen-activated CD3⁺ T cells. We suggest that MMP-dependent cleavage of PD-1 ligands on fibroblasts may limit their immunosuppressive capacity and thus contribute to the exacerbation of inflammation in tissues. In contrast, carcinoma-associated fibroblasts appear PD-1 ligand-depleted through MMP activity that may impair physical deletion of exhausted defective memory T cells through apoptosis and facilitate their regulatory functions. These observations should be considered when using the powerful PD-1/PD-L1 blocking immunotherapies.

Negative immune checkpoints on T lymphocytes and their relevance to cancer immunotherapy

The term 'inhibitory checkpoint' refers to the broad spectrum of co-receptors expressed by T cells that negatively regulate T cell activation thus playing a crucial role in maintaining peripheral self-tolerance. Co-inhibitory receptor ligands are highly expressed by a variety of malignancies allowing evasion of anti-tumour immunity. Recent studies demonstrate that manipulation of these co-inhibitory pathways can remove the immunological brakes that impede endogenous immune responses against tumours. Antibodies that block the interactions between co-inhibitory receptors and their ligands have delivered very promising clinical responses, as has been shown by recent successful trials targeting the CTLA-4 and PD-1 pathways. In this review, we discuss the mechanisms of action and expression pattern of co-inhibitory receptors on different T cells subsets, emphasising differences between CD4(+) and CD8(+) T cells. We also summarise recent clinical findings utilising immune checkpoint blockade.

Human Cancer Immunotherapy with PD-1/PD-L1 Blockade

The ligation of programmed cell death-1 (PD-1) to its ligands PD-L1 and PD-L2 counteracts T-cell activation, which is critical in immune tolerance. The persistent high expression of PD-1 and PD-L1 are also observed on tumor-infiltrating lymphocytes and various tumor cells, maintaining the highly suppressive microenvironment in tumor sites and promoting tumor malignancies. The blockade of PD-1 axis with PD-L2 fusion protein or monoclonal antibodies against either PD-1 or PD-L1 has been clinically evaluated in various tumor types. This short review summarizes the progress of PD-1 axis blockade in clinical trials to evaluate its effectiveness in the antitumor immunotherapy.

Programmed death-1 & its ligands: promising targets for cancer immunotherapy

Novel strategies for cancer treatment involving blockade of immune inhibitors have shown significant progress toward understanding the molecular mechanism of tumor immune evasion. The preclinical findings and clinical responses associated with programmed death-1 (PD-1) and PD-ligand pathway blockade seem promising, making these targets highly sought for cancer immunotherapy. In fact, the anti-PD-1 antibodies, pembrolizumab and nivolumab, were recently approved by the US FDA for the treatment of unresectable and metastatic melanoma resistant to anticytotoxic T-lymphocyte antigen-4 antibody (ipilimumab) and BRAF inhibitor. Here, we discuss strategies of combining PD-1/PD-ligand interaction inhibitors with other immune checkpoint modulators and standard-of-care therapy to break immune tolerance and induce a potent antitumor activity, which is currently a research area of key scientific pursuit.

PD-1/PD-L1 expression on CD(4+) T cells and myeloid DCs correlates with the immune pathogenesis of atrial fibrillation

Although immuno-inflammatory response contributes to pathogenesis of AF, molecular and cellular mechanism in this process remains poorly understood. Recently, increasing evidence suggests that Programmed death-1 (PD-1)/PD-1 ligand (PD-L) pathway may be a potential pathway participating in AF pathogenesis. In this study, we detected the PD-1 and PD-L1, 2 expression on peripheral blood function cells by flow cytometry in 91 atrial fibrillation (AF) patients and 35 healthy volunteers. The expression of PD-1 on CD⁴⁺ T cells and PD-L1 on myeloid dendritic cells (mDCs) in AF patients is significantly down-regulated compared with healthy volunteers. In addition, the extent of PD-1/PD-L1 down-regulation is closely related with AF burden. More importantly, Allogeneic mixed leukocyte reactions (MLR) shows that the mDCs PD-L1 down-regulation is associated with increased T cell (CD⁴⁺ and CD⁸⁺) proliferation, increased type 1 effector cytokines (IL-2 and IFN-γ) secretion, and decreased type 2 effector cytokine (IL-10) secretion. Then, PD-L1 up-regulation by the stimulation of IFN-α can significantly convert this representation. Collectively, our report suggest that T(CD⁴⁺)/mDCs-associated PD-1/PD-L1 pathway plays a key role in AF immune regulation. PD-1/PD-L1 down-regulation in AF patients promotes T cells function and may contribute to AF pathogenesis.

Combining chemotherapy and checkpoint blockade in thoracic cancer: how to proceed?

SUMMARY 

Given the impressive efficacy of immune checkpoint blockade in thoracic malignancies, and the recently discovered immune-stimulating properties of many cytotoxic drugs, a logical next step would be to combine these treatments. However, the rational design of clinical trials investigating these combinations is hampered by a lack of knowledge regarding the overall immunogenic effects of the different chemotherapeutics. Here, we give an overview of the field with regard to checkpoint blockade and the immunological effects of cytotoxic chemotherapeutics, with particular focus on preclinical and clinical studies investigating the combination of these two treatment modalities. We discuss the hurdles that need to be overcome in order to optimally exploit chemotherapy and immune checkpoint blockade combinations in thoracic cancers.

The perspective of immunotherapy: new molecules and new mechanisms of action in immune modulation

PURPOSE OF REVIEW

Targeting CTLA-4, the patriarch of immune checkpoint modulators, is currently the only immunotherapeutic approach that has achieved significant clinical benefit in melanoma phase III trials. In this review, recent new ideas about the mechanism of action of anti-CTLA antibodies, other new molecules to target, and rationales for combination therapies will be discussed.

RECENT FINDINGS

Although the clinical efficacy of the anti-CTLA-4 monoclonal antibody (mAb) ipilimumab is meanwhile without doubt, its mechanism of action is still not fully understood. Recent data indicate that, besides modulation of the TCR signal, CTLA-4 mAbs can mediate regulatory T-cell depletion in an Fc gamma receptor dependent manner.Blockade of the molecules PD-1 and PD-L1 has given promising clinical responses (and this beyond melanoma), whereas their complex expression and interaction pattern makes a clear statement about the mechanism of action challenging.Additional other co-inhibitory and co-stimulatory molecules have been identified recently. Combinations of immune checkpoint modulators themselves or with other therapies, such as adoptive cell therapy, targeted therapy or radiotherapy, will improve the outcomes further.

SUMMARY

Immune checkpoint blockade is currently the most promising systemic therapeutic approach to achieve long-lasting responses or even cure in melanoma and other malignancies.

The PD-1/PD-Ls pathway and autoimmune diseases

The programmed death (PD)-1/PD-1 ligands (PD-Ls) pathway, is a new member of the B7/CD28 family, and consists of the PD-1 receptor and its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC, CD273). Recently, it is reported that PD-1, PD-L1 and PD-L2 also have soluble forms aside from their membrane bound forms. The soluble forms increase the diversity and complexity of PD-1/PD-Ls pathway in both composition and function. The PD-1/PD-Ls pathway is broadly expressed and exerts a wider range of immunoregulatory roles in T-cell activation and tolerance compared with other B7/CD28 family members. Studies show that the PD-1/PD-Ls pathway regulates the induction and maintenance of peripheral tolerance and protects tissues from autoimmune attack in physiological conditions. In addition, it is also involved in various diseases mediated by T cells, such as autoimmunity, tumor immunity, chronic viral infections, and transplantation immunity. In this review, we will summarize the relevance of the soluble forms and the latest researches on the role of PD-1/PD-Ls pathway in autoimmune diseases.

RGMb is a novel binding partner for PD-L2 and its engagement with PD-L2 promotes respiratory tolerance

Interaction between the inhibitory molecule PD-L2 on dendritic cells and repulsive guidance molecule b (RGMb) on lung macrophages is required to establish respiratory tolerance.

We report that programmed death ligand 2 (PD-L2), a known ligand of PD-1, also binds to repulsive guidance molecule b (RGMb), which was originally identified in the nervous system as a co-receptor for bone morphogenetic proteins (BMPs). PD-L2 and BMP-2/4 bind to distinct sites on RGMb. Normal resting lung interstitial macrophages and alveolar epithelial cells express high levels of RGMb mRNA, whereas lung dendritic cells express PD-L2. Blockade of the RGMb–PD-L2 interaction markedly impaired the development of respiratory tolerance by interfering with the initial T cell expansion required for respiratory tolerance. Experiments with PD-L2–deficient mice showed that PD-L2 expression on non–T cells was critical for respiratory tolerance, but expression on T cells was not required. Because PD-L2 binds to both PD-1, which inhibits antitumor immunity, and to RGMb, which regulates respiratory immunity, targeting the PD-L2 pathway has therapeutic potential for asthma, cancer, and other immune-mediated disorders. Understanding this pathway may provide insights into how to optimally modulate the PD-1 pathway in cancer immunotherapy while minimizing adverse events.

RGMb is a novel binding partner for PD-L2 and its engagement with PD-L2 promotes respiratory tolerance

We report that programmed death ligand 2 (PD-L2), a known ligand of PD-1, also binds to repulsive guidance molecule b (RGMb), which was originally identified in the nervous system as a co-receptor for bone morphogenetic proteins (BMPs). PD-L2 and BMP-2/4 bind to distinct sites on RGMb. Normal resting lung interstitial macrophages and alveolar epithelial cells express high levels of RGMb mRNA, whereas lung dendritic cells express PD-L2. Blockade of the RGMb-PD-L2 interaction markedly impaired the development of respiratory tolerance by interfering with the initial T cell expansion required for respiratory tolerance. Experiments with PD-L2-deficient mice showed that PD-L2 expression on non-T cells was critical for respiratory tolerance, but expression on T cells was not required. Because PD-L2 binds to both PD-1, which inhibits antitumor immunity, and to RGMb, which regulates respiratory immunity, targeting the PD-L2 pathway has therapeutic potential for asthma, cancer, and other immune-mediated disorders. Understanding this pathway may provide insights into how to optimally modulate the PD-1 pathway in cancer immunotherapy while minimizing adverse events.

Expression analysis of programmed death ligand 2 in tumors caused by the avian oncovirus Marek's disease virus

PD-L2 is a ligand of the immunoinhibitory receptor PD-1. Here, we report functional and expression analyses of PD-L2 in tumor lesions and spleens from chickens infected with gallid herpesvirus 2 (GaHV-2, Marek's disease virus), which induces malignant lymphomas in chickens. We show that the expression of IFN-γ protein was decreased in PBMCs and splenocytes co-cultured with PD-L2-expressing cells and that the expression of PD-L2 mRNA was significantly higher in the spleens of infected chickens in the latent phase and in tumor lesions caused by GaHV-2. These results suggest that chicken PD-L2 has an immunoinhibitory function and is involved in the establishment of latency and tumor formation by GaHV-2.

Invariant NKT cells increase drug-induced osteosarcoma cell death

BACKGROUND AND PURPOSE

In osteosarcoma (OS) patients, only a limited number of drugs are active and the regimens currently in use include a combination of at least two of these drugs: doxorubicin, cisplatin, methotrexate and ifosfamide. Today, 30-40% of patients still die of OS highlighting the urgent need for new treatments. Invariant NKT (iNKT) cells are a lymphocyte lineage with features of both T and NK cells, playing important roles in tumour suppression. Our aim was to test whether the cytoxicity induced by cisplatin, doxorubicin and methotrexate against OS cells can be enhanced by iNKT cell treatment.

EXPERIMENTAL APPROACH

iNKT cells were purified from human peripheral blood mononuclear cells by cell sorting (Vα24Vβ11(+) cells) and used as effector cells against OS cells (U2-OS, HOS, MG-63). Cell death (calcein-AM method), perforin/granzyme B and Fas/FasL expressions were determined by flow cytometry. CD1d expression was analysed at both the gene and protein level.

KEY RESULTS

iNKT cells were cytotoxic against OS cells through a CD1d-dependent mechanism. This activity was specific for tumour cells, because human CD1d(+) mesenchymal stem cells and CD1d(-) osteoblasts were not affected. iNKT cell treatment enhanced drug-induced OS cell death in a concentration-dependent manner and this effect was reduced in CD1d-silenced OS cells.

CONCLUSION AND IMPLICATIONS

iNKT cells kill malignant, but not non-malignant, cells. iNKT cell treatment enhances the cytotoxicity of anti-neoplastic drugs against OS cells in a CD1d-dependent manner. The present data encourage further studies on the use of iNKT cells in OS therapy.

Programmed cell death ligand 2 regulates TH9 differentiation and induction of chronic airway hyperreactivity

BACKGROUND

Asthma is defined as a chronic inflammatory disease of the airways; however, the underlying physiologic and immunologic processes are not fully understood.

OBJECTIVE

The aim of this study was to determine whether TH9 cells develop in vivo in a model of chronic airway hyperreactivity (AHR) and what factors control this development.

METHOD

We have developed a novel chronic allergen exposure model using the clinically relevant antigen Aspergillus fumigatus to determine the time kinetics of TH9 development in vivo.

RESULTS

TH9 cells were detectable in the lungs after chronic allergen exposure. The number of TH9 cells directly correlated with the severity of AHR, and anti-IL-9 treatment decreased airway inflammation. Moreover, we have identified programmed cell death ligand (PD-L) 2 as a negative regulator of TH9 cell differentiation. Lack of PD-L2 was associated with significantly increased TGF-β and IL-1α levels in the lungs, enhanced pulmonary TH9 differentiation, and higher morbidity in the sensitized mice.

CONCLUSION

Our findings suggest that PD-L2 plays a pivotal role in the regulation of TH9 cell development in chronic AHR, providing novel strategies for modulating adaptive immunity during chronic allergic responses.

Programmed death ligand 2 in cancer-induced immune suppression

Inhibitory molecules of the B7/CD28 family play a key role in the induction of immune tolerance in the tumor microenvironment. The programmed death-1 receptor (PD-1), with its ligands PD-L1 and PD-L2, constitutes an important member of these inhibitory pathways. The relevance of the PD-1/PD-L1 pathway in cancer has been extensively studied and therapeutic approaches targeting PD-1 and PD-L1 have been developed and are undergoing human clinical testing. However, PD-L2 has not received as much attention and its role in modulating tumor immunity is less clear. Here, we review the literature on the immunobiology of PD-L2, particularly on its possible roles in cancer-induced immune suppression and we discuss the results of recent studies targeting PD-L2 in cancer.