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

Interplay between inflammasomes and PD-1/PD-L1 and their implications in cancer immunotherapy

The inflammasomes play crucial roles in inflammation and cancer development, while the PD-1/PD-L1 pathway is critical for immune suppression in the tumor microenvironment (TME). Recent research indicates a reciprocal regulatory relationship between inflammasomes and PD-1/PD-L1 signaling in cancer development and PD-1 blockade treatment. By activating in diverse cells in tumor tissues, inflammasome upregulates PD-L1 level in the TME. Moreover, the regulation of PD-1/PD-L1 activity by inflammasome activation involves natural killer cells, tumor-associated macrophages and myeloid-derived suppressor cells. Conversely, PD-1 blockade can activate the inflammasome, potentially influencing treatment outcomes. The interplay between inflammasomes and PD-1/PD-L1 has profound and intricate effects on cancer development and treatment. In this review, we discuss the crosstalk between inflammasomes and PD-1/PD-L1 in cancers, exploring their implications for tumorigenesis, metastasis and immune checkpoint inhibitor (ICI) resistance. The combined therapeutic strategies targeting both inflammasomes and checkpoint molecules hold promising potential as treatments for cancer.

Radiation-associated secondary malignancies: a novel opportunity for applying immunotherapies

Radiation is commonly used as a treatment intended to cure or palliate cancer patients. Despite remarkable advances in the precision of radiotherapy delivery, even the most advanced forms inevitably expose some healthy tissues surrounding the target site to radiation. On rare occasions, this results in the development of radiation-associated secondary malignancies (RASM). RASM are typically high-grade and carry a poorer prognosis than their non-radiated counterparts. RASM are characterized by a high mutation burden, increased T cell infiltration, and a microenvironment that bears unique inflammatory signatures of prior radiation, including increased expression of various cytokines (e.g., TGF-β, TNF-α, IL4, and IL10). Interestingly, these cytokines have been shown to up-regulate the expression of PD-1 and/or PD-L1-an immune checkpoint receptor/ligand pair that is commonly targeted by immune checkpoint blocking immunotherapies. Here, we review the current understanding of the tumor-immune interactions in RASM, highlight the distinct clinical and molecular characteristics of RASM that may render them immunologically "hot," and propose a rationale for the formal testing of immune checkpoint blockade as a treatment approach for patients with RASM.

Metabolic interventions combined with CTLA-4 and PD-1/PD-L1 blockade for the treatment of tumors: mechanisms and strategies

Immunotherapies based on immune checkpoint blockade (ICB) have significantly improved patient outcomes and offered new approaches to cancer therapy over the past decade. To date, immune checkpoint inhibitors (ICIs) of CTLA-4 and PD-1/PD-L1 represent the main class of immunotherapy. Blockade of CTLA-4 and PD-1/PD-L1 has shown remarkable efficacy in several specific types of cancers, however, a large subset of refractory patients presents poor responsiveness to ICB therapy; and the underlying mechanism remains elusive. Recently, numerous studies have revealed that metabolic reprogramming of tumor cells restrains immune responses by remodeling the tumor microenvironment (TME) with various products of metabolism, and combination therapies involving metabolic inhibitors and ICIs provide new approaches to cancer therapy. Nevertheless, a systematic summary is lacking regarding the manner by which different targetable metabolic pathways regulate immune checkpoints to overcome ICI resistance. Here, we demonstrate the generalized mechanism of targeting cancer metabolism at three crucial immune checkpoints (CTLA-4, PD-1, and PD-L1) to influence ICB therapy and propose potential combined immunotherapeutic strategies co-targeting tumor metabolic pathways and immune checkpoints.

Interferon-gamma and tumor necrosis factor-alpha synergistically enhance the immunosuppressive capacity of human umbilical-cord-derived mesenchymal stem cells by increasing PD-L1 expression

BACKGROUND

The immunosuppressive capacity of mesenchymal stem cells (MSCs) is dependent on the "license" of several proinflammatory factors to express immunosuppressive factors such as programmed cell death 1 ligand 1 (PD-L1), which determines the clinical therapeutic efficacy of MSCs for inflammatory or immune diseases. In MSCs, interferon-gamma (IFN-γ) is a key inducer of PD-L1 expression, which is synergistically enhanced by tumor necrosis factor-alpha (TNF-α); however, the underlying mechanism is unclear.

AIM

To reveal the mechanism of pretreated MSCs express high PD-L1 and explore the application of pretreated MSCs in ulcerative colitis.

METHODS

We assessed PD-L1 expression in human umbilical-cord-derived MSCs (hUC-MSCs) induced by IFN-γ and TNF-α, alone or in combination. Additionally, we performed signal pathway inhibitor experiments as well as RNA interference experiments to elucidate the molecular mechanism by which IFN-γ alone or in combination with TNF-α induces PD-L1 expression. Moreover, we used luciferase reporter gene experiments to verify the binding sites of the transcription factors of each signal transduction pathway to the targeted gene promoters. Finally, we evaluated the immunosuppressive capacity of hUC-MSCs treated with IFN-γ and TNF-α in both an in vitro mixed lymphocyte culture assay, and in vivo in mice with dextran sulfate sodium-induced acute colitis.

RESULTS

Our results suggest that IFN-γ induction alone upregulates PD-L1 expression in hUC-MSCs while TNF-α alone does not, and that the co-induction of IFN-γ and TNF-α promotes higher expression of PD-L1. IFN-γ induces hUC-MSCs to express PD-L1, in which IFN-γ activates the JAK/STAT1 signaling pathway, up-regulates the expression of the interferon regulatory factor 1 (IRF1) transcription factor, promotes the binding of IRF1 and the PD-L1 gene promoter, and finally promotes PD-L1 mRNA. Although TNF-α alone did not induce PD-L1 expression in hUC-MSCs, the addition of TNF-α significantly enhanced IFN-γ-induced JAK/STAT1/IRF1 activation. TNF-α up-regulated IFN-γ receptor expression through activation of the nuclear factor kappa-B signaling pathway, which significantly enhanced IFN-γ signaling. Finally, co-induced hUC-MSCs have a stronger inhibitory effect on lymphocyte proliferation, and significantly ameliorate weight loss, mucosal damage, inflammatory cell infiltration, and up-regulation of inflammatory factors in colitis mice.

CONCLUSION

Overall, our results suggest that IFN-γ and TNF-α enhance both the immunosuppressive ability of hUC-MSCs and their efficacy in ulcerative colitis by synergistically inducing high expression of PD-L1.

Immunotherapy for Recurrent Glioma-From Bench to Bedside

Glioma is the most aggressive malignant tumor of the central nervous system, and most patients suffer from a recurrence. Unfortunately, recurrent glioma often becomes resistant to established chemotherapy and radiotherapy treatments. Immunotherapy, a rapidly developing anti-tumor therapy, has shown a potential value in treating recurrent glioma. Multiple immune strategies have been explored. The most-used ones are immune checkpoint blockade (ICB) antibodies, which are barely effective in monotherapy. However, when combined with other immunotherapy, especially with anti-angiogenesis antibodies, ICB has shown encouraging efficacy and enhanced anti-tumor immune response. Oncolytic viruses and CAR-T therapies have shown promising results in recurrent glioma through multiple mechanisms. Vaccination strategies and immune-cell-based immunotherapies are promising in some subgroups of patients, and multiple new tumor antigenic targets have been discovered. In this review, we discuss current applicable immunotherapies and related mechanisms for recurrent glioma, focusing on multiple preclinical models and clinical trials in the last 5 years. Through reviewing the current combination of immune strategies, we would like to provide substantive thoughts for further novel therapeutic regimes treating recurrent glioma.

Emerging phagocytosis checkpoints in cancer immunotherapy

Cancer immunotherapy, mainly including immune checkpoints-targeted therapy and the adoptive transfer of engineered immune cells, has revolutionized the oncology landscape as it utilizes patients' own immune systems in combating the cancer cells. Cancer cells escape immune surveillance by hijacking the corresponding inhibitory pathways via overexpressing checkpoint genes. Phagocytosis checkpoints, such as CD47, CD24, MHC-I, PD-L1, STC-1 and GD2, have emerged as essential checkpoints for cancer immunotherapy by functioning as "don't eat me" signals or interacting with "eat me" signals to suppress immune responses. Phagocytosis checkpoints link innate immunity and adaptive immunity in cancer immunotherapy. Genetic ablation of these phagocytosis checkpoints, as well as blockade of their signaling pathways, robustly augments phagocytosis and reduces tumor size. Among all phagocytosis checkpoints, CD47 is the most thoroughly studied and has emerged as a rising star among targets for cancer treatment. CD47-targeting antibodies and inhibitors have been investigated in various preclinical and clinical trials. However, anemia and thrombocytopenia appear to be formidable challenges since CD47 is ubiquitously expressed on erythrocytes. Here, we review the reported phagocytosis checkpoints by discussing their mechanisms and functions in cancer immunotherapy, highlight clinical progress in targeting these checkpoints and discuss challenges and potential solutions to smooth the way for combination immunotherapeutic strategies that involve both innate and adaptive immune responses.

Inhibiting efferocytosis reverses macrophage-mediated immunosuppression in the leukemia microenvironment

Background

Previous studies show that the spleen and bone marrow can serve as leukemia microenvironments in which macrophages play a significant role in immune evasion and chemoresistance. We hypothesized that the macrophage driven tolerogenic process of efferocytosis is a major contributor to the immunosuppressive leukemia microenvironment and that this was driven by aberrant phosphatidylserine expression from cell turnover and cell membrane dysregulation.

Methods

Since MerTK is the prototypic efferocytosis receptor, we assessed whether the MerTK inhibitor MRX2843, which is currently in clinical trials, would reverse immune evasion and enhance immune-mediated clearance of leukemia cells.

Results

We found that inhibition of MerTK decreased leukemia-associated macrophage expression of M2 markers PD-L1, PD-L2, Tim-3, CD163 and Arginase-1 compared to vehicle-treated controls. Additionally, MerTK inhibition led to M1 macrophage repolarization including elevated CD86 and HLA-DR expression, and increased production of T cell activating cytokines, including IFN-β, IL-18, and IL-1β through activation of NF-κB. Collectively, this macrophage repolarization had downstream effects on T cells within the leukemia microenvironment, including decreased PD-1+Tim-3+ and LAG3+ checkpoint expression, and increased CD69+CD107a+ expression.

Discussion

These results demonstrate that MerTK inhibition using MRX2843 altered the leukemia microenvironment from tumor-permissive toward immune responsiveness to leukemia and culminated in improved immune-mediated clearance of AML.

Regulation of programmed death ligand 1 expression by interferon-γ and tumour necrosis factor-α in canine tumour cell lines

Expression of programmed death ligand 1 (PD-L1) on tumour cells provides an immune evasion mechanism by inducing suppression of cytotoxic T cells. Various regulatory mechanisms of PD-L1 expression have been described in human tumours, however, little is known in canine tumours. To investigate whether inflammatory signalling is involved in PD-L1 regulation in canine tumours, the effects of interferon (IFN)-γ and tumour necrosis factor (TNF)-α treatment were examined in canine malignant melanoma cell lines (CMeC and LMeC) and an osteosarcoma cell line (HMPOS). The protein level of PD-L1 expression was upregulated by IFN-γ and TNF-α stimulation. Upon IFN-γ stimulation, all cell lines showed an increase in expression of PD-L1, signal transducer and activator of transcription (STAT)1, STAT3 and genes regulated by STAT activation. Upregulated expression of these genes was suppressed by the addition of a JAK inhibitor, oclacitinib. Contrastingly, upon TNF-α stimulation, all cell lines exhibited higher gene expression of the nuclear factor kappa B (NF-κB) gene RELA and genes regulated by NF-κB activation, whereas expression of PD-L1 was upregulated in LMeC only. Upregulated expression of these genes was suppressed by the addition of an NF-κB inhibitor, BAY 11-7082. The expression level of cell surface PD-L1 induced by IFN-γ and TNF-α treatment was reduced by oclacitinib and BAY 11-7082, respectively, indicating that upregulation of PD-L1 expression by IFN-γ and TNF-α stimulation is regulated via the JAK-STAT and NF-κB signalling pathways, respectively. These results provide insights into the role of inflammatory signalling in PD-L1 regulation in canine tumours.

Programmed Cell Death-Ligand 1 in Head and Neck Squamous Cell Carcinoma: Molecular Insights, Preclinical and Clinical Data, and Therapies

Aberrant expression of the programmed cell death protein ligand 1 (PD-L1) constitutes one of the main immune evasion mechanisms of cancer cells. The approval of drugs against the PD-1-PD-L1 axis has given new impetus to the chemo-therapy of many malignancies. We performed a literature review from 1992 to August 2022, summarizing evidence regarding molecular structures, physiological and pathological roles, mechanisms of PD-L1 overexpression, and immunotherapy evasion. Furthermore, we summarized the studies concerning head and neck squamous cell carcinomas (HNSCC) immunotherapy and the prospects for improving the associated outcomes, such as identifying treatment response biomarkers, new pharmacological combinations, and new molecules. PD-L1 overexpression can occur via four mechanisms: genetic modifications; inflammatory signaling; oncogenic pathways; microRNA or protein-level regulation. Four molecular mechanisms of resistance to immunotherapy have been identified: tumor cell adaptation; changes in T-cell function or proliferation; alterations of the tumor microenvironment; alternative immunological checkpoints. Immunotherapy was indeed shown to be superior to traditional chemotherapy in locally advanced/recurrent/metastatic HNSCC treatments.

TNF-α-dependent lung inflammation upregulates PD-L1 in monocyte-derived macrophages to contribute to lung tumorigenesis

Chronic inflammation, which is dominated by macrophage-involved inflammatory responses, is an instigator of cancer initiation. Macrophages are the most abundant immune cells in healthy lungs, and associated with lung tumor development and promotion. PD-L1 is a negative molecule in macrophages and correlated with an immunosuppressive function in tumor environment. Macrophages expressing PD-L1, rather than tumor cells, exhibits a critical role in tumor growth and progression. However, whether and how PD-L1 in macrophages contributes to inflammation-induced lung tumorigenesis requires further elucidation. Here, we found that higher expression of PD-L1 in CD11b⁺ CD206⁺ macrophages was positively correlated with tumor progression and PD-1⁺ CD8⁺ T cells population in human adenocarcinoma patients. In the urethane-induced inflammation-driven lung adenocarcinoma (IDLA) mouse model, the infiltration of circulating CD11b^high F4/80⁺ monocyte-derived macrophages (MoMs) was increased in pro-tumor inflamed lung tissues and lung adenocarcinoma. PD-L1 was mainly upregulated in MoMs associated with enhanced T cells exhaustion in lung tissues. Anti-PD-L1 treatment can reduce T cells exhaustion at pro-tumor inflammatory stage, and then inhibit tumorigenesis in IDLA. The pro-tumor lung inflammation depended on TNF-α to upregulate PD-L1 and CSN6 expression in MoMs, and induced cytokines production by alveolar type-II cells (AT-II). Furthermore, inflammatory AT-II cells could secret TNF-α to upregulate PD-L1 expression in bone-marrow driven macrophages (BM-M0). Inhibition of CSN6 decreased PD-L1 expression in TNF-α-activated macrophage in vitro, suggesting a critical role of CSN6 in PD-L1 upregulation. Thus, pro-tumor inflammation can depend on TNF-α to upregulate PD-L1 in recruited MoMs, which may be essential for lung tumorigenesis.

Tumor immune checkpoints and their associated inhibitors

Immunological evasion is one of the defining characteristics of cancers, as the immune modification of an immune checkpoint (IC) confers immune evasion capabilities to tumor cells. Multiple ICs, such as programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), can bind to their respective receptors and reduce tumor immunity in a variety of ways, including blocking immune cell activation signals. IC blockade (ICB) therapies targeting these checkpoint molecules have demonstrated significant clinical benefits. This is because antibody-based IC inhibitors and a variety of specific small molecule inhibitors can inhibit key oncogenic signaling pathways and induce durable tumor remission in patients with a variety of cancers. Deciphering the roles and regulatory mechanisms of these IC molecules will provide crucial theoretical guidance for clinical treatment. In this review, we summarize the current knowledge on the functional and regulatory mechanisms of these IC molecules at multiple levels, including epigenetic regulation, transcriptional regulation, and post-translational modifications. In addition, we provide a summary of the medications targeting various nodes in the regulatory pathway, and highlight the potential of newly identified IC molecules, focusing on their potential implications for cancer diagnostics and immunotherapy.

Transcriptomic Correlates of Tumor Cell PD-L1 Expression and Response to Nivolumab Monotherapy in Metastatic Clear Cell Renal Cell Carcinoma

PURPOSE

PD-L1 expression on tumor cells (TC) is associated with response to anti-PD-1-based therapies in some tumor types, but its significance in clear cell renal cell carcinoma (ccRCC) is uncertain. We leveraged tumor heterogeneity to identify molecular correlates of TC PD-L1 expression in ccRCC and assessed their role in predicting response to anti-PD-1 monotherapy.

EXPERIMENTAL DESIGN

RNA sequencing was performed on paired TC PD-L1 positive and negative areas isolated from eight ccRCC tumors and transcriptomic features associated with PD-L1 status were identified. A cohort of 232 patients with metastatic ccRCC from the randomized CheckMate-025 (CM-025) trial was used to confirm the findings and correlate transcriptomic profiles with clinical outcomes.

RESULTS

In both the paired samples and the CM-025 cohort, TC PD-L1 expression was associated with combined overexpression of immune- and cell proliferation-related pathways, upregulation of T-cell activation signatures, and increased tumor-infiltrating immune cells. In the CM-025 cohort, TC PD-L1 expression was not associated with clinical outcomes. A molecular RCC subtype characterized by combined overexpression of immune- and cell proliferation-related pathways (previously defined by unsupervised clustering of transcriptomic data) was enriched in TC PD-L1 positive tumors and displayed longer progression-free survival (HR, 0.32; 95% confidence interval, 0.13-0.83) and higher objective response rate (30% vs. 0%, P = 0.04) on nivolumab compared with everolimus.

CONCLUSIONS

Both TC-extrinsic (immune-related) and TC-intrinsic (cell proliferation-related) mechanisms are likely intertwined in the regulation of TC PD-L1 expression in ccRCC. The quantitation of these transcriptional programs may better predict benefit from anti-PD-1-based therapy compared with TC PD-L1 expression alone in ccRCC.

Understanding the functional inflammatory factors involved in therapeutic response to immune checkpoint inhibitors for pan-cancer

Immune checkpoint inhibitors (ICIs) fight tumor progression by activating immune conditions. The inflammatory factors are playing a functional role in programmed death-1 (PD-1) or other immune checkpoints. They are involved in regulating the expression of programmed death ligand-1 (PD-L1), the only predictor recognized by the guidelines in response to ICIs. In addition, abundant components of the tumor microenvironment (TME) all interact with various immune factors contributing to the response to ICIs, including infiltration of various immune cells, extracellular matrix, and fibroblasts. Notably, the occurrence of immune-related adverse events (irAEs) in patients receiving ICIs is increasingly observed in sundry organs. IrAEs are often regarded as an inflammatory factor-mediated positive feedback loop associated with better response to ICIs. It deserves attention because inflammatory factors were observed to be different when targeting different immune checkpoints or in the presence of different irAEs. In the present review, we address the research progresses on regulating inflammatory factors for an intentional controlling anti-cancer response with immune checkpoint inhibitors.

Aziz NH, Md Zin RR, Tan GC, Shafiee MN. PD-L1 Expression in Endometrial Cancer and Its Association with Clinicopathological Features: A Systematic Review and Meta-Analysis

Simple Summary

In women, endometrial cancer is a crucial cancer cause-death, which is still not fully explored in its pathogenesis and immune system. Early detection is essential for proper treatment and follow-up in affected patients. This systematic review and meta-analysis aim to pool the prevalence of PD-L1 in endometrial cancer and its association with clinicopathological features. The pooled prevalence of PD-L1 was 34.26% in tumour cells, and 51.39% in immune cells among endometrial cancer patients. There was significant association of PD-L1 expression in both tumour cells and immune cells with advanced stage endometrial cancer. The presence of lympho-vascular invasion and poor overall survival were also associated with PD-L1 expression in immune cells. These information enable clinicians to stratify endometrial cancer patients for anti-PD-1/PD-L1 immune therapy.

Abstract

Endometrial cancer (EC) is one of the most common malignancies of the female genital tract and its current treatment mainly relies on surgical removal of the tumour bulk, followed by adjuvant radiotherapy with or without chemotherapy/hormonal therapy. However, the outcomes of these approaches are often unsatisfactory and are associated with severe toxicity and a higher recurrence rate of the disease. Thus, more clinical research exploring novel medical intervention is needed. Involvement of the immune pathway in cancer has become important and the finding of a high positive expression of programmed cell death-ligand 1 (PD-L1) in EC may offer a better targeted therapeutic approach. Numerous studies on the PD-L1 role in EC have been conducted, but the results remained inconclusive. Hence, this systematic review was conducted to provide an update and robust analysis in order to determine the pooled prevalence of PD-L1 expression in EC and evaluate its association with clinicopathological features in different focuses of tumour cells (TC) and immune cells (IC). A comprehensive literature search was conducted using the PubMed, Web of Science, and Scopus databases. Twelve articles between 2016 and 2021 with 3023 EC cases met the inclusion criteria. The effect of PD-L1 expression on the outcome parameters was estimated by the odds ratios (ORs) with 95% confidence intervals (CIs) for each study. The pooled prevalence of PD-L1 was 34.26% and 51.39% in the tumour cell and immune cell, respectively, among women with EC. The PD-L1 expression was significantly associated with Stage III/IV disease (in both TC and IC) and correlated to the presence of lympho-vascular invasion in IC. However, the PD-L1 expression in TC was not associated with the age groups, histology types, myometrial invasion, and lympho-vascular invasion. In IC, PD-L1 expression was not associated with age group, histology type, and myometrial invasion. The meta-analysis survival outcomes of PD-L1 high expression had a significant association with worse OS in IC but not in TC.

Pharmacological Treatments Available for Immune-Checkpoint-Inhibitor-Induced Colitis

Immune checkpoint inhibitor treatment has shown revolutionary therapeutic effects in various carcinomas. However, immune-related adverse events (irAE) following this treatment can sometimes lead to treatment discontinuation. One such frequently encountered adverse event is immune-related colitis (irAE colitis). Corticosteroids (CS) are the first-line treatment for irAE colitis, but we often encounter CS-refractory or -resistant cases. The application of multiple biologics has been proposed as a therapy to be administered after CS treatment; however, the efficacy and safety of biologics for patients with irAE colitis who do not respond to CS have not been established. This review summarizes the treatment regimens available for irAE colitis, focusing on the mechanism of action of corticosteroids, infliximab, vedolizumab, and other drugs.

The generation of PD-L1 and PD-L2 in cancer cells: From nuclear chromatin reorganization to extracellular presentation

The immune checkpoint blockade (ICB) targeting on PD-1/PD-L1 has shown remarkable promise in treating cancers. However, the low response rate and frequently observed severe side effects limit its broad benefits. It is partially due to less understanding of the biological regulation of PD-L1. Here, we systematically and comprehensively summarized the regulation of PD-L1 from nuclear chromatin reorganization to extracellular presentation. In PD-L1 and PD-L2 highly expressed cancer cells, a new TAD (topologically associating domain) (chr9: 5,400,000-5,600,000) around CD274 and CD273 was discovered, which includes a reported super-enhancer to drive synchronous transcription of PD-L1 and PD-L2. The re-shaped TAD allows transcription factors such as STAT3 and IRF1 recruit to PD-L1 locus in order to guide the expression of PD-L1. After transcription, the PD-L1 is tightly regulated by miRNAs and RNA-binding proteins via the long 3'UTR. At translational level, PD-L1 protein and its membrane presentation are tightly regulated by post-translational modification such as glycosylation and ubiquitination. In addition, PD-L1 can be secreted via exosome to systematically inhibit immune response. Therefore, fully dissecting the regulation of PD-L1/PD-L2 and thoroughly detecting PD-L1/PD-L2 as well as their regulatory networks will bring more insights in ICB and ICB-based combinational therapy.

Extracellular vesicle PD-L1 in reshaping tumor immune microenvironment: biological function and potential therapy strategies

Programmed cell death 1 ligand 1 (PD-L1) is the ligand for programmed death protein-1 (PD-1), is associated with immunosuppression. Signaling via PD-1/PD-L1 will transmits negative regulatory signals to T cells, inducing T-cell inhibition, reducing CD8⁺ T-cell proliferation, or promoting T-cell apoptosis, which effectively reduces the immune response and leads to large-scale tumor growth. Accordingly, many antibody preparations targeting PD-1 or PD-L1 have been designed to block the binding of these two proteins and restore T-cell proliferation and cytotoxicity of T cells. However, these drugs are ineffective in clinical practice. Recently, numerous of studies have shown that, in addition to the surface of tumor cells, PD-L1 is also found on the surface of extracellular vesicles secreted by these cells. Extracellular vesicle PD-L1 can also interact with PD-1 on the surface of T cells, leading to immunosuppression, and has been proposed as a potential mechanism underlying PD-1/PD-L1-targeted drug resistance. Therefore, it is important to explore the production, regulation and tumor immunosuppression of PD-L1 on the surface of tumor cells and extracellular vesicles, as well as the potential clinical application of extracellular vesicle PD-L1 as tumor biomarkers and therapeutic targets.

Extracellular acidity in tumor tissue upregulates programmed cell death protein 1 expression on tumor cells via proton-sensing G protein-coupled receptors

Acidity in the tumor microenvironment has been reported to promote cancer growth and metastasis. In our study, we examined a potential relation between extracellular acidity and expression level of the immune checkpoint molecule programmed cell death protein 1 (PD-L1) in murine squamous cell carcinoma (SCC) and melanoma cell lines. PD-L1 expression in the tumor cells was upregulated by culturing in a low pH culture medium. Tumor-bearing mice were allowed to ingest sodium bicarbonate, resulting in neutralization of acidity in the tumor tissue, a decrease in PD-L1 expression in tumor cells and suppression of tumor growth in vivo. Proton-sensing G protein-coupled receptors, T-cell death-associated gene 8 (TDAG8) and ovarian cancer G-protein-coupled receptor 1 (OGR1), were upregulated by low pH, and essentially involved in the acidity-induced elevation of PD-L1 expression in the tumor cells. Human head and neck SCC RNAseq data from the Cancer Genome Atlas also suggested a statistically significant correlation between expression levels of the proton sensors and PD-L1 mRNA expression. These findings strongly suggest that neutralization of acidity in tumor tissue may result in reduction of PD-L1 expression, potentially leading to inhibition of an immune checkpoint and augmentation of antitumor immunity.

Autophagy controls programmed death-ligand 1 expression on cancer cells (Review)

Programmed death-ligand 1 (PD-L1) is a transmembrane protein mainly located on cancer cells, including renal cell carcinoma, breast, colorectal, gastric and non-small cell lung cancer. PD-L1 binds to the PD-1 receptor expressed on T lymphocytes to inhibit the activation of T lymphocytes, thus allowing tumour cells to escape immune surveillance, leading to tumour growth and the poor prognosis of patients with cancer. Inhibitors targeting the programmed death-1/PD-L1 axis have been widely used in the clinical treatment of a variety of solid tumours in recent years. However, the clinical efficacy of these inhibitors varies. Studies have demonstrated that the effect of the targeted drug is positively associated with the expression of PD-L1 on the tumour membrane. Hence, exploring the mechanism of PD-L1 expression is very important for the treatment of tumours. Autophagy is a physiological process that maintains the stability of the internal environment. Autophagy degrades aging organelles and long-lived proteins and produces nutrients for cell recycling. To the best of our knowledge, the present review is the first to summarize the research that has been conducted on autophagy-regulated PD-L1 expression, which may provide new avenues for tumour immunotherapy.

Perspectives on immune checkpoint ligands: expression, regulation, and clinical implications

In the tumor microenvironment, immune checkpoint ligands (ICLs) must be expressed in order to trigger the inhibitory signal via immune checkpoint receptors (ICRs). Although ICL expression frequently occurs in a manner intrinsic to tumor cells, extrinsic factors derived from the tumor microenvironment can fine-tune ICL expression by tumor cells or prompt non-tumor cells, including immune cells. Considering the extensive interaction between T cells and other immune cells within the tumor microenvironment, ICL expression on immune cells can be as significant as that of ICLs on tumor cells in promoting anti-tumor immune responses. Here, we introduce various regulators known to induce or suppress ICL expression in either tumor cells or immune cells, and concise mechanisms relevant to their induction. Finally, we focus on the clinical significance of understanding the mechanisms of ICLs for an optimized immunotherapy for individual cancer patients.

Increased antitumor efficacy of ginsenoside Rh2 via mixed micelles: in vivo and in vitro evaluation

The aim of this work is to apply Solutol^® HS15 and TPGS to prepare self-assembled micelles loading with ginsenoside Rh₂ to increase the solubility of ginsenoside Rh₂, hence, improving the antitumor efficacy. Ginsenoside Rh₂-mixed micelles (Rh₂-M) were prepared by thin film dispersion method. The optimal Rh₂-M was characterized by particle size, morphology, and drug encapsulation efficiency. The enhancement of in vivo anti-tumor efficacy of Rh₂-M was evaluated by nude mice bearing tumor model. The solubility of Rh₂ in self-assembled micelles was increased approximately 150-folds compared to free Rh₂. In vitro results demonstrated that the particle size of Rh₂-M is 74.72 ± 2.63 nm(PDI = 0.147 ± 0.15), and the morphology of Rh₂-M is spherical or spheroid, and the EE% and LE% are 95.27 ± 1.26% and 7.68 ± 1.34%, respectively. The results of in vitro cell uptake and in vivo imaging showed that Rh₂-M could not only increase the cell uptake of drugs, but also transport drug to tumor sites, prolonging the retention time. In vitro cytotoxicity and in vivo antitumor results showed that the anti-tumor effect of Rh₂ can be effectively improved by Rh₂-M. Therefore, Solutol^® HS15 and TPGS could be used to entrapping Rh₂ into micelles, enhancing solubility and antitumor efficacy.

Time-Programmed Delivery of Sorafenib and Anti-CD47 Antibody via a Double-Layer-Gel Matrix for Postsurgical Treatment of Breast Cancer

The highly immunosuppressive microenvironment after surgery has a crucial impact on the recurrence and metastasis in breast cancer patients. Programmable delivery of immunotherapy-involving combinations through a single drug delivery system is highly promising, yet greatly challenging, to reverse postoperative immunosuppression. Here, an injectable hierarchical gel matrix, composed of dual lipid gel (DLG) layers with different soybean phosphatidylcholine/glycerol dioleate mass ratios, was developed to achieve the time-programmed sequential delivery of combined cancer immunotherapy. The outer layer of the DLG matrix was thermally responsive and loaded with sorafenib-adsorbed graphene oxide (GO) nanoparticles. GO under manually controlled near-infrared irradiation generated mild heat and provoked the release of sorafenib first to reeducate tumor-associated macrophages (TAMs) and promote an immunogenic tumor microenvironment. The inner layer, loaded with anti-CD47 antibody (aCD47), could maintain the gel state for a much longer time, enabling the sustained release of aCD47 afterward to block the CD47-signal regulatory protein α (SIRPα) pathway for a long-term antitumor effect. In vivo studies on 4T1 tumor-bearing mouse model demonstrated that the DLG-based strategy efficiently prevented tumor recurrence and metastasis by locally reversing the immunosuppression and synergistically blocking the CD47-dependent immune escape, thereby boosting the systemic immune responses.

Regulatory mechanisms of immune checkpoints PD-L1 and CTLA-4 in cancer

The cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4)/B7 and programmed death 1 (PD-1)/ programmed cell death-ligand 1 (PD-L1) are two most representative immune checkpoint pathways, which negatively regulate T cell immune function during different phases of T-cell activation. Inhibitors targeting CTLA-4/B7 and PD1/PD-L1 pathways have revolutionized immunotherapies for numerous cancer types. Although the combined anti-CTLA-4/B7 and anti-PD1/PD-L1 therapy has demonstrated promising clinical efficacy, only a small percentage of patients receiving anti-CTLA-4/B7 or anti-PD1/PD-L1 therapy experienced prolonged survival. Regulation of the expression of PD-L1 and CTLA-4 significantly impacts the treatment effect. Understanding the in-depth mechanisms and interplays of PD-L1 and CTLA-4 could help identify patients with better immunotherapy responses and promote their clinical care. In this review, regulation of PD-L1 and CTLA-4 is discussed at the levels of DNA, RNA, and proteins, as well as indirect regulation of biomarkers, localization within the cell, and drugs. Specifically, some potential drugs have been developed to regulate PD-L1 and CTLA-4 expressions with high efficiency.

Differential expression of PD-L1 between primary and metastatic epithelial ovarian cancer and its clinico-pathological correlation

Ovarian cancer (OC) is one of the most common gynecologic cancer, which has the worst prognosis and highest mortality rate. The lack of curative treatment and the high relapse rate, especially in advanced OC, continues to present a clinical challenge, highlighting the need for new therapeutic strategies. This study was performed to compare the expression of PD-L1 in primary epithelial ovarian cancer (EOC) and their corresponding peritoneal metastases, as well as to evaluate its correlation with clinico-pathological parameters. In total, 194 treatment naïve paired EOC and peritoneal metastasis were analyzed by immunohistochemistry for PD-L1 expression. Clinico-pathological information was available for all patients. Significant differences in PD-L1 expression were found between primary EOC and peritoneal metastasis (p < 0.0001). We found discordant tumor cell PD-L1 expression between primary tumors and corresponding peritoneal metastasis in 34% (66/194) of cases. Furthermore, PD-L1 expression in peritoneal metastasis samples was significantly associated with adverse prognostic factors, such as high proliferative index (Ki67) (p = 0.0039) and high histologic grade (p = 0.0330). In conclusion, the discordance of PD-L1 expression between primary EOC and corresponding peritoneal metastases suggests that its assessment as a potential biomarker for predicting response to anti-PD-L1 therapy may require analysis of metastatic lesions.

Regulation of PD-L1 expression in the tumor microenvironment

Programmed death-ligand 1 (PD-L1) on cancer cells engages with programmed cell death-1 (PD-1) on immune cells, contributing to cancer immune escape. For multiple cancer types, the PD-1/PD-L1 axis is the major speed-limiting step of the anti-cancer immune response. In this context, blocking PD-1/PD-L1 could restore T cells from exhausted status and eradicate cancer cells. However, only a subset of PD-L1 positive patients benefits from α-PD-1/PD-L1 therapies. Actually, PD-L1 expression is regulated by various factors, leading to the diverse significances of PD-L1 positivity. Understanding the mechanisms of PD-L1 regulation is helpful to select patients and enhance the treatment effect. In this review, we focused on PD-L1 regulators at the levels of transcription, post-transcription, post-translation. Besides, we discussed the potential applications of these laboratory findings in the clinic.

Assessment of hazard immune-related genes and tumor immune infiltrations in renal cell carcinoma

BACKGROUND

The present study aimed to explore and validate a prognostic immune signature, to formulate a prognosis for ccRCC patients combined with immune-infiltration analysis.

METHODS

Public datasets were used as our source of multi-omics data. Differential analysis was performed via the edgeR package. A prognostic immune signature was identified by univariate Cox analysis, and we constructed an integrative tumor-associated immune genes (TAIG) model from the multivariate Cox results. In order to interrogate and identify the related crosstalk, functional analysis was deployed. Significantly, we implemented the CIBERSORT algorithm to estimate the immune cell fractions in the ccRCC samples, and analyzed the differential abundance of tumor-infiltrating immune cells in two TAIG groups, using a Wilcoxon rank-sum test. The prognostic role of differential immune cells was further assessed via a Kaplan-Meier analysis. In addition, we investigated the associations of a single immune signature with specific immune cells.

RESULTS

A total of 628 ccRCC patients were comprised in our integrative analysis, including 537 ccRCC patients in the discovery group and 91 patients in the validation group. Fourteen key immune signatures were subsequently identified. A figure of 0.802 was registered for AUC, and worse prognosis was evinced for those patients with a higher TAIG. Correlation analysis indicated that TAIG correlated closely with both clinical variables and TMB. Moreover, functional analysis implicated the immune-related GO items or crosstalk. Hence, we were able to identify the relationships obtaining between tumor-infiltrating immune cells and TAIG. The differential abundance of immune cells showed a significant prognostic difference and consisted of memory-activated CD4⁺ T cells, T follicular helper cells, T regulatory cells, and so on. Moreover, we also characterized the associations between identified signatures and specific immune cells. Finally, the five-year AUC in the ICGC cohort was 0.72, suggesting the robustness of the TAIG that we constructed.

CONCLUSIONS

Overall, our team characterized the tumor-associated immune signature in ccRCC, and further identified the prognostic tumor-infiltrating immune cells related to TAIG. This in turn provided a solid foundation for investigating individualized immunotherapy, as well as other relevant mechanisms.

A 14 immune-related gene signature predicts clinical outcomes of kidney renal clear cell carcinoma

Kidney renal clear cell carcinoma (KIRC) is the leading cause of kidney cancer-related deaths. Currently, there are no studies in tumor immunology investigating the use of signatures as a predictor of overall survival in KIRC patients. Our study attempts to establish an immune-related gene risk signature to predict clinical outcomes in KIRC. A total of 528 patients from The Cancer Genome Atlas (TCGA) database were included in our analysis and randomly divided into training (n = 315) and testing sets (n = 213). We collected 1,534 immune-related genes from the Immunology Database and Analysis Portal as candidates to construct our signature. LASSO-COX was used to find gene models with the highest predictive ability. We used survival and Cox analysis to test the model's independent prognostic ability. Univariate analysis identified 650 immune-related genes with prognostic abilities. After 1,000 iterations, we choose 14 of the most frequent and stable immune-related genes as our signature. We found that the signature was associated with M stage, T stage, and pathological staging. More importantly, the signature can independently predict clinical prognosis in KIRC patients. Gene Set Enrichment Analysis (GSEA) showed an association between our signature and critical metabolism pathways. Our research established a model based upon 14 immune-related genes that predicted the prognosis of KIRC patients based on tumor immune microenvironments.

Regulation of CD47 expression in cancer cells

CD47 is overexpressed in various types of cancers and it can directly bind with SIRPα, which is mainly located on macrophages. The binding of CD47-SIRPα transmits a “don't eat me” signal, which can prevent cancer cells from immune clearance. Targeting the phagocytosis checkpoint of CD47-SIRPα axis has shown remarkable anticancer effect in preclinical and clinical research, which indicates the potential application of CD47-SIRPα blockade for cancer treatment. In this case, the comprehensive description of the regulation of CD47 in different types of cancer cells has significant implications for furthering our understanding of the role of CD47 in cancer. Based on the current reports, we summarized the regulatory factors, i.e., cytokines, oncogenes, microRNAs as well as enzymes, of CD47 expression in cancer cells. Accordingly, we also proposed several points needing further research, hoping to provide useful insights for the future investigation on the regulation of CD47 in cancers.

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Cytokines, oncogenes, microRNAs and enzymes regulate CD47 expression in cancer.

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CD47 expression could be regulated at the transcriptional, post-transcriptional and post-translational modification level.

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Further studies are required to determine other factors that regulate CD47 expression.

Mechanistic insight of predictive biomarkers for antitumor PD‑1/PD‑L1 blockade: A paradigm shift towards immunome evaluation (Review)

Checkpoint inhibitor-based immunotherapy has exhibited unprecedented success in the treatment of advanced-stage cancer in recent years. Several therapeutic antibodies targeting programmed death-1 (PD-1) or its ligand (PD-L1) have received regulatory approvals for the treatment of multiple malignancies, including melanoma, non-small cell lung cancer, kidney cancer and Hodgkin's lymphoma. However, a substantial proportion of patients still do not benefit from these agents, let alone the risk of immune-associated toxicities and financial burden. Therefore, it is imperative to identify valid predictive biomarkers which can help optimize the selection of patients. In this review, a mechanism-based interpretation of tumor PD-L1 expression and other candidate biomarkers of response to antitumor PD-1/PD-L1 blockade was provided, particularly for the tumor microenvironment-derived ‘immunomes’, and the challenges faced in their clinical use was addressed. Directions for future biomarker development and the potential of combined biomarker strategies were also proposed.

Programmed cell death ligand-1: A dynamic immune checkpoint in cancer therapy

Antibody-based immunotherapies play a pivotal role in cancer research with efficient achievements in tumor suppression. Tumor survival is assisted by modulation of immune checkpoints to create imbalances between immune cells and cancer cell's environment. The modulation results in T-cell signal inhibition ultimately inert its proliferation and activation against various tumor cells. PD-L1, a 40 kDa transmembrane protein of B7 family, binds with PD-1 on the membrane of T cells which results in inhibition of T-cell proliferation and activation. PD-L1/PD-1 pathway has generated novel target sites for antibodies that can block PD-L1/PD-1 interactions. The blockage results in T-cell proliferation and tumor cell suppression. The PD-L1 immune checkpoint strategies' development, expression and regulations, signal inhibitions, and developmental stages of PD-L1/PD-1 antibodies are briefly discussed here in this review. All this information will provide a base for new therapeutic development against PD-L1 and PD-1 immune checkpoint interactions and will make available promising treatment options.

Prognostic value of programmed cell death ligand-1 expression in ovarian cancer: an updated meta-analysis

Objective

To investigate the prognostic significance of programmed cell death ligand-1 (PD-L1) in ovarian cancer.

Methods

PubMed, Embase, and Cochrane Library databases were searched to identify studies that examined the prognostic significance of immunohistochemically assessed PD-L1 expression in histologically confirmed ovarian cancer. Eleven studies on PD-L1 expression involving 1,296 patients with ovarian cancer were included in this meta-analysis. Pooled hazard ratios (HRs) with corresponding 95% confidence intervals (CIs) were analyzed. Relationship between PD-L1 expression, and overall survival (OS) or progression-free survival (PFS) among patients with ovarian cancer was assessed. Subgroup analysis was performed based on the race, histologic type, and tumor International Federation of Gynecology and Obstetrics stage to evaluate the source of heterogeneity. Begg's Funnel plot and Egger's linear test were used to evaluate publication bias. Random-effects model was implemented when significant between-study heterogeneity (I²>50%) was observed.

Results

We found no correlation between PD-L1 expression, and OS (HR, 1.13; 95% CI, 0.95–1.36; I²=78%) or PFS (HR, 1.07; 95% CI, 0.88–1.30; I²=75%) in ovarian cancer. Subgroup analyses showed that higher PD-L1 expression was associated with poor OS in non-Asian patients with ovarian cancer (HR, 1.26; 95% CI, 1.07–1.481; I²=59%). We found that upregulated PD-L1 expression to be a positive predictor for OS in serous ovarian cancer (HR, 0.98; 95% CI, 0.76–1.26; I²=74%) and a negative predictor for OS in non-serous ovarian cancer (HR, 1.29; 95% CI, 1.03–1.61; I²=64%) Furthermore, high PD-L1 expression was found to be a negative predictor for PFS of patients with non-serous ovarian cancer (HR, 1.12; 95% CI, 0.96–1.29; I²=37%).

Conclusion

Our meta-analysis suggests that PD-L1 expression is not associated with patient risk for ovarian cancer.

Roles of PD-1/PD-L1 Pathway: Signaling, Cancer, and Beyond

Immunotherapies that target PD-1/PD-L1 axis have shown unprecedented success in a wide variety of human cancers. PD-1 is one of the key coinhibitory receptors expressed on T cells upon T cell activation. After engagement with its ligands, mainly PD-L1, PD-1 is activated and recruits the phosphatase SHP-2 in proximity to T cell receptor (TCR) and CD28 signaling. This event results in dephosphorylation and attenuation of key molecules in TCR and CD28 pathway, leading to inhibition of T cell proliferation, activation, cytokine production, altered metabolism and cytotoxic T lymphocytes (CTLs) killer functions, and eventual death of activated T cells. Bodies evolve coinhibitory pathways controlling T cell response magnitude and duration to limit tissue damage and maintain self-tolerance. However, tumor cells hijack these inhibitory pathways to escape host immune surveillance by overexpression of PD-L1. This provides the scientific rationale for clinical application of immune checkpoint inhibitors in oncology. The aberrantly high expression of PD-L1 in tumor microenvironment (TME) can be attributable to the "primary" activation of multiple oncogenic signaling and the "secondary" induction by inflammatory factors such as IFN-γ. Clinically, antibodies targeting PD-1/PD-L1 reinvigorate the "exhausted" T cells in TME and show remarkable objective response and durable remission with acceptable toxicity profile in large numbers of tumors such as melanoma, lymphoma, and mismatch-repair deficient tumors. Nevertheless, most patients are still refractory to anti-PD-1/PD-L1 therapy. Identifying the predictive biomarkers and design rational PD-1-based combination therapy become the priorities in cancer immunotherapy. PD-L1 expression, cytotoxic T lymphocytes infiltration, and tumor mutation burden (TMB) are generally considered as the most important factors affecting the effectiveness of PD-1/PD-L1 blockade. The revolution in cancer immunotherapy achieved by PD-1/PD-L1 blockade offers the paradigm for scientific translation from bench to bedside. The next decades will without doubt witness the renaissance of immunotherapy.

Humanized Mice as an Effective Evaluation System for Peptide Vaccines and Immune Checkpoint Inhibitors

Peptide vaccination was developed for the prevention and therapy of acute and chronic infectious diseases and cancer. However, vaccine development is challenging, because the patient immune system requires the appropriate human leukocyte antigen (HLA) recognition with the peptide. Moreover, antigens sometimes induce a low response, even if the peptide is presented by antigen-presenting cells and T cells recognize it. This is because the patient immunity is dampened or restricted by environmental factors. Even if the immune system responds appropriately, newly-developed immune checkpoint inhibitors (ICIs), which are used to increase the immune response against cancer, make the immune environment more complex. The ICIs may activate T cells, although the ratio of responsive patients is not high. However, the vaccine may induce some immune adverse effects in the presence of ICIs. Therefore, a system is needed to predict such risks. Humanized mouse systems possessing human immune cells have been developed to examine human immunity in vivo. One of the systems which uses transplanted human peripheral blood mononuclear cells (PBMCs) may become a new diagnosis strategy. Various humanized mouse systems are being developed and will become good tools for the prediction of antibody response and immune adverse effects.

Mild photothermal therapy potentiates anti-PD-L1 treatment for immunologically cold tumors via an all-in-one and all-in-control strategy

One of the main challenges for immune checkpoint blockade antibodies lies in malignancies with limited T-cell responses or immunologically “cold” tumors. Inspired by the capability of fever-like heat in inducing an immune-favorable tumor microenvironment, mild photothermal therapy (PTT) is proposed to sensitize tumors to immune checkpoint inhibition and turn “cold” tumors “hot.” Here we present a combined all-in-one and all-in-control strategy to realize a local symbiotic mild photothermal-assisted immunotherapy (SMPAI). We load both a near-infrared (NIR) photothermal agent IR820 and a programmed death-ligand 1 antibody (aPD-L1) into a lipid gel depot with a favorable property of thermally reversible gel-to-sol phase transition. Manually controlled NIR irradiation regulates the release of aPD-L1 and, more importantly, increases the recruitment of tumor-infiltrating lymphocytes and boosts T-cell activity against tumors. In vivo antitumor studies on 4T1 and B16F10 models demonstrate that SMPAI is an effective and promising strategy for treating “cold” tumors.

Mechanisms Controlling PD-L1 Expression in Cancer

The engagement of programmed cell death protein 1 (PD-1; encoded by the PDCD1 gene) receptor expressed on activated T cells and its ligand, programmed death-ligand 1 (PD-L1; encoded by the CD274 gene), is a major co-inhibitory checkpoint signaling that controls T cell activities. Various types of cancers express high levels of PD-L1 and exploit PD-L1/PD-1 signaling to evade T cell immunity. Blocking the PD-L1/PD-1 pathway has consistently shown remarkable anti-tumor effects in patients with advanced cancers and is recognized as the gold standard for developing new immune checkpoint blockade (ICB) and combination therapies. However, the response rates of anti-PD-L1 have been limited in several solid tumors. Therefore, furthering our understanding of the regulatory mechanisms of PD-L1 can bring substantial benefits to patients with cancer by improving the efficacy of current PD-L1/PD-1 blockade or other ICBs. In this review, we provide current knowledge of PD-L1 regulatory mechanisms at the transcriptional, posttranscriptional, post-translational, and extracellular levels, and discuss the implications of these findings in cancer diagnosis and immunotherapy.

Recent Findings in the Regulation of Programmed Death Ligand 1 Expression

With the recent approvals for the application of monoclonal antibodies that target the well-characterized immune checkpoints, immune therapy shows great potential against both solid and hematologic tumors. The use of these therapeutic monoclonal antibodies elicits inspiring clinical results with durable objective responses and improvements in overall survival. Agents targeting programmed cell death protein 1 (PD-1; also known as PDCD1) and its ligand (PD-L1) achieve a great success in immune checkpoints therapy. However, the majority of patients fail to respond to PD-1/PD-L1 axis inhibitors. Expression of PD-L1 on the membrane of tumor and immune cells has been shown to be associated with enhanced objective response rates to PD-1/PD-L1 inhibition. Thus, an improved understanding of how PD-L1 expression is regulated will enable us to better define its role as a predictive marker. In this review, we summarize recent findings in the regulation of PD-L1 expression.

Prognostic effect of programmed death-ligand 1 (PD-L1) in ovarian cancer: a systematic review, meta-analysis and bioinformatics study

BACKGROUND

The expression of PD-L1 has been reported in ovarian cancer. However, the prognostic role of PD-L1 expression in ovarian carcinoma remained controversial. This study was performed to assess the prognostic value of PD-L1 expression on ovarian cancer.

METHODS

The PubMed, Embase, EBSCO, and Cochrane Library databases were searched to identify available publications. The pooled odds ratio (OR) or hazard ratios (HRs: multivariate analysis) with their 95% confidence intervals (95% CIs) were calculated in this analysis. A bioinformatics study based on The Cancer Genome Atlas (TCGA) sequencing and microarray datasets was used to further validate the results of PD-L1 mRNA expression. Kaplan-Meier (KM) survival curves were performed to evaluate the prognostic effect of PD-L1 mRNA expression.

RESULTS

Twelve studies with 1630 ovarian cancers regarding PD-L1 immunohistochemical expression were identified. Meta-analysis showed that PD-L1 protein expression was not associated with tumor grade, clinical stage, lymph node status, tumor histology, overall survival (OS), and progression-free survival (PFS). TCGA data showed no association between PD-L1 mRNA expression and ovarian cancer. Further validation using microarray data suggested that no association between PD-L1 mRNA expression and OS was found in large independent patient cohorts (1310 cases). PD-L1 mRNA expression was significantly linked to worse PFS in 1228 patients with ovarian cancer (227458_at: HR = 1.55, 95% CI = 1.28-1.88, P < 0.001; 223834_at: HR = 1.41, 95% CI = 1.14-1.75, P = 0.0015).

CONCLUSIONS

Meta-analysis showed that PD-L1 may not be a prognostic factor for ovarian cancer. But a bioinformatics study showed that PD-L1 expression was significantly associated with worse PFS of ovarian cancer. More clinical studies are needed to further validate these findings.

Prognostic effect of programmed death-ligand 1 (PD-L1) in ovarian cancer: a systematic review, meta-analysis and bioinformatics study

BACKGROUND

The expression of PD-L1 has been reported in ovarian cancer. However, the prognostic role of PD-L1 expression in ovarian carcinoma remained controversial. This study was performed to assess the prognostic value of PD-L1 expression on ovarian cancer.

METHODS

The PubMed, Embase, EBSCO, and Cochrane Library databases were searched to identify available publications. The pooled odds ratio (OR) or hazard ratios (HRs: multivariate analysis) with their 95% confidence intervals (95% CIs) were calculated in this analysis. A bioinformatics study based on The Cancer Genome Atlas (TCGA) sequencing and microarray datasets was used to further validate the results of PD-L1 mRNA expression. Kaplan-Meier (KM) survival curves were performed to evaluate the prognostic effect of PD-L1 mRNA expression.

RESULTS

Twelve studies with 1630 ovarian cancers regarding PD-L1 immunohistochemical expression were identified. Meta-analysis showed that PD-L1 protein expression was not associated with tumor grade, clinical stage, lymph node status, tumor histology, overall survival (OS), and progression-free survival (PFS). TCGA data showed no association between PD-L1 mRNA expression and ovarian cancer. Further validation using microarray data suggested that no association between PD-L1 mRNA expression and OS was found in large independent patient cohorts (1310 cases). PD-L1 mRNA expression was significantly linked to worse PFS in 1228 patients with ovarian cancer (227458_at: HR = 1.55, 95% CI = 1.28-1.88, P < 0.001; 223834_at: HR = 1.41, 95% CI = 1.14-1.75, P = 0.0015).

CONCLUSIONS

Meta-analysis showed that PD-L1 may not be a prognostic factor for ovarian cancer. But a bioinformatics study showed that PD-L1 expression was significantly associated with worse PFS of ovarian cancer. More clinical studies are needed to further validate these findings.

Prognostic effect of programmed death-ligand 1 (PD-L1) in ovarian cancer: a systematic review, meta-analysis and bioinformatics study

BACKGROUND

The expression of PD-L1 has been reported in ovarian cancer. However, the prognostic role of PD-L1 expression in ovarian carcinoma remained controversial. This study was performed to assess the prognostic value of PD-L1 expression on ovarian cancer.

METHODS

The PubMed, Embase, EBSCO, and Cochrane Library databases were searched to identify available publications. The pooled odds ratio (OR) or hazard ratios (HRs: multivariate analysis) with their 95% confidence intervals (95% CIs) were calculated in this analysis. A bioinformatics study based on The Cancer Genome Atlas (TCGA) sequencing and microarray datasets was used to further validate the results of PD-L1 mRNA expression. Kaplan-Meier (KM) survival curves were performed to evaluate the prognostic effect of PD-L1 mRNA expression.

RESULTS

Twelve studies with 1630 ovarian cancers regarding PD-L1 immunohistochemical expression were identified. Meta-analysis showed that PD-L1 protein expression was not associated with tumor grade, clinical stage, lymph node status, tumor histology, overall survival (OS), and progression-free survival (PFS). TCGA data showed no association between PD-L1 mRNA expression and ovarian cancer. Further validation using microarray data suggested that no association between PD-L1 mRNA expression and OS was found in large independent patient cohorts (1310 cases). PD-L1 mRNA expression was significantly linked to worse PFS in 1228 patients with ovarian cancer (227458_at: HR = 1.55, 95% CI = 1.28-1.88, P < 0.001; 223834_at: HR = 1.41, 95% CI = 1.14-1.75, P = 0.0015).

CONCLUSIONS

Meta-analysis showed that PD-L1 may not be a prognostic factor for ovarian cancer. But a bioinformatics study showed that PD-L1 expression was significantly associated with worse PFS of ovarian cancer. More clinical studies are needed to further validate these findings.

Regulatory mechanisms of PD-L1 expression in cancer cells

Immunotherapy targeting the PD-L1/PD-1 pathway using antibodies is effective in the clinical treatment of a multitude of cancers. This makes research of the regulatory mechanisms of PD-1 expression in cancer cells intriguing. PD-L1 expression can be categorized into inducible expression, attributed to extrinsic factors in the microenvironment, and constitutive expression, attributed to intrinsic cancer-driving gene alteration. The mechanisms of PD-L1 expression in cancer cells operate at multiple levels, including gene amplification, chromatin modification, transcription, posttranscription, translation and posttranslation. Moreover, some open questions in this field that need to be answered in future research are proposed. Studies of regulatory mechanisms of PD-L1 expression pave the way for the application of more effective approaches in the future of cancer immunotherapy.

Roles of Loss of Chromosome 14q Allele in the Prognosis of Renal Cell Carcinoma with C-reactive Protein Abnormity

Background:

Renal cell carcinoma (RCC) is frequently associated with paraneoplastic inflammatory syndrome (PIS). This study aimed at exploring the connections between the survival rate and specific gene alterations and the potential mechanism.

Methods:

We retrospectively studied 69 surgical RCC cases from August 2014 to February 2016, including 18 cases of clear cell RCC (ccRCC) demonstrating elevated pretreatment serum C-reactive protein (CRP, Group A). Twelve of the 18 cases were symptomized with febrile episode. We also selected 49 cases of ccRCC with normal pretreatment CRP (Group B). Using 22 microsatellite markers, we compared the incidence of loss of heterozygosity (LOH) between Group A and Group B. All statistical tests are two-sided.

Results:

The 3p LOH was common in both Group A (89%) and Group B (92%). The frequency of 14q LOH in Group A (16 of 18) was higher than Group B (4 of 49, χ² = 40.97 P < 0.0001). The 3p and 14q LOH were the characteristics of ccRCC with elevated acute phase reactants, including PIS, regardless of the presence of metastasis. On the contrary, 14q LOH was a rare genomic alternation in advanced-staged ccRCC without PIS. The overall survival of patients with elevated CRP (33.3%) was lower than its counterparts (6.1%, hazard ratio=1.852, P < 0.0001) in Kaplan-Meier curve.

Conclusions:

The results imply that the disruption of a 14q gene(s) might result in not only the inflammatory manifestations in the tumor host but also the poor survival rate as well. The isolation of the gene(s) on 14q might be a vital goal in the treatment of PIS-associated RCC.

Amphotericin B suppresses M2 phenotypes and B7-H1 expression in macrophages to prevent Raji cell proliferation

Background

Macrophages in the tumor microenvironment play a critical role in tumorigenesis and anti-cancer drug resistance. Burkitt’s lymphoma (BL) is a B-cell non-Hodgkin’s lymphoma with dense macrophage infiltration. However, the role for macrophages in BL remains largely unknown.

Methods

B7-H1, a transmembrane glycoprotein in the B7 family, suppresses T cell activation and proliferation and induces the apoptosis of activated T cells. The expression of B7-H1 in BL clinical tissues was determined by streptavidin-peroxidase immunohistochemistry. The mutual regulation between macrophages and BL Raji cells was investigated in a co-culture system. The cell proliferation and cell cycle distribution of Raji cells were determined using BrdU staining coupled with flow cytometry. CD163, CD204 and B7-H1 expression was assessed by flow cytometry and Western blot. Cell invasion was analyzed by Transwell assay. The expression of cytokines was detected by quantitative RT-PCR. Immunofluorescence and allogeneic T-cell proliferation assays were used to compare the expression of B7-H1, p-STAT6, or p-STAT3 and CD3+ T cell proliferation treated with or without amphotericin B.

Results

B7-H1 was highly expressed in tumor infiltration macrophages in most clinical BL tissues. In vitro, Raji cells synthesized IL-4, IL-6, IL-10 and IL-13 to induce CD163, CD204 and B7-H1 expression in co-cultured macrophages, which in turn promoted Raji cell proliferation and invasion. Interestingly, antifungal agent amphotericin B not only inhibited STAT6 phosphorylation to suppress the M2 polarization of macrophages, but also promoted CD3+ T cell proliferation by regulating B7-H1 protein expression in macrophages.

Conclusion

Amphotericin B might represent a novel immunotherapeutic approach to treat patients with BL.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4266-0) contains supplementary material, which is available to authorized users.

B7-H6 expression is induced by lipopolysaccharide and facilitates cancer invasion and metastasis in human gliomas

Although great progress has been made in treatment regimens, gliomas are still incurable and the 5-year survival remains poor. Studies focusing on molecules that regulate tumorigenesis or tumor immunity may provide potential therapeutic strategies for patients with glioma. B7-H6 is selectively expressed in tumor cells and plays vital roles in host immune responses. In this study, we demonstrated that B7-H6 was expressed in glioma cell lines, including CRT, U251, SHG-44, SF-295, TG-905 and U373, and tumor tissues isolated from glioma patients. Moreover, the expression levels of B7-H6 were significantly correlated with glioma grade. Previous studies reported that inflammatory mediators and cytokines induced the expression of B7 family members including programmed death-ligand 1, B7-H2 and B7-H4. Therefore, we explored the regulation of B7-H6 expression in gliomas and showed that lipopolysaccharide induced the expression of B7-H6 in glioma cells. To further analyze the roles of B7-H6 in gliomas, the expression of B7-H6 in glioma cells was knocked down. The results of cell counting kit-8, colony formation, wound healing, and transwell migration and invasion assays demonstrated that the proliferation, migration and invasion of glioma cells were inhibited after knocking down B7-H6. To elucidate the specific mechanisms of B7-H6 function in cancer progression, we examined the expression levels of proteins involved in cell apoptosis, migration and invasion. We demonstrated that the expression levels of E-cadherin and Bcl-2 associated X protein increased, and the expression levels of vimentin, N-cadherin, matrix metalloproteinase-2, matrix metalloproteinase-9 and survivin decreased after knocking down B7-H6. In conclusion, B7-H6 plays important roles in glioma, and targeting B7-H6 may provide a novel therapeutic strategy for glioma patients.

Regulation and Function of the PD-L1 Checkpoint

Expression of programmed death-ligand 1 (PD-L1) is frequently observed in human cancers. Binding of PD-L1 to its receptor PD-1 on activated T cells inhibits anti-tumor immunity by counteracting T cell-activating signals. Antibody-based PD-1-PD-L1 inhibitors can induce durable tumor remissions in patients with diverse advanced cancers, and thus expression of PD-L1 on tumor cells and other cells in the tumor microenviroment is of major clinical relevance. Here we review the roles of the PD-1-PD-L1 axis in cancer, focusing on recent findings on the mechanisms that regulate PD-L1 expression at the transcriptional, posttranscriptional, and protein level. We place this knowledge in the context of observations in the clinic and discuss how it may inform the design of more precise and effective cancer immune checkpoint therapies.

Prognostic value of PD-L1 overexpression for pancreatic cancer: evidence from a meta-analysis

Programmed death-ligand 1 (PD-L1) is an immune checkpoint that is often activated in cancer and plays a pivotal role in the initiation and progression of cancer. However, the clinicopathologic significance and prognostic value of PD-L1 in pancreatic cancer (PC) remains controversial. In this study, we conducted a meta-analysis to retrospectively evaluate the relationship between PD-L1 and PC. PubMed and other databases were searched for the clinical studies published up to March 21, 2017, to be included in the meta-analysis. Hazard ratios and their 95% CIs were calculated. Risk ratios (RRs) were extracted to assess the correlations between the clinicopathologic parameters and PD-L1 expression. Ten studies including 1,058 patients were included in the meta-analysis. The pooled results indicated that positive PD-L1 expression was correlated with a poor overall survival outcome in PC patients (hazard ratio =1.76, 95% CI: 1.43–2.17, P<0.00001). Interestingly, high PD-L1 expression was correlated with poor pathologic differentiation (RR =1.57, 95% CI: 1.25–1.98, P=0.0001) and neural invasion (RR =1.30, 95% CI: 1.03–1.64, P=0.03). However, there were no significant correlations between PD-L1 expression and other clinicopathologic characteristics. In summary, our meta-analysis implied that PD-L1 could serve as a negative predictor for the overall survival of PC patients, and high expression of PD-L1 was correlated with poor differentiation and neural invasion, indicating that anti-PD-L1 treatments should be evaluated in PC patients, especially in those who exhibit these two characteristics.

Regulation of PD-L1 expression on murine tumor-associated monocytes and macrophages by locally produced TNF-α

PD-L1 is an immune checkpoint protein that has emerged as a major signaling molecule involved with tumor escape from T cell immune responses. Studies have shown that intra-tumoral expression of PD-L1 can inhibit antitumor immune responses. However, it has recently been shown that expression of PD-L1 on myeloid cells from the tumor is a stronger indicator of prognosis than tumor cell PD-L1 expression. Therefore, it is important to understand the factors that govern the regulation of PD-L1 expression on tumor-infiltrating myeloid cells. We found that immature bone marrow monocytes in tumor-bearing mice had low levels of PD-L1 expression, while higher levels of expression were observed on monocytes in circulation. In contrast, macrophages found in tumor tissues expressed much higher levels of PD-L1 than circulating monocytes, implying upregulation by the tumor microenvironment. We demonstrated that tumor-conditioned media strongly induced increased PD-L1 expression by bone marrow-derived monocytes and TNF-α to be a cytokine that causes an upregulation of PD-L1 expression by the monocytes. Furthermore, we found production of TNF-α by the monocytes themselves to be a TLR2-dependent response to versican secreted by tumor cells. Thus, PD-L1 expression by tumor macrophages appears to be regulated in a different manner than by tumor cells themselves.

HLA-E expression and its clinical relevance in human renal cell carcinoma

The non-classical human leukocyte antigen E (HLA-E) expression is frequently overexpressed in tumor diseases, transplants and virus-infected cells and represents an immunomodulatory molecule by binding to the receptors CD94/NKG2A, -B and -C on NK and T cells. Due to its immune suppressive features HLA-E expression might represent an important mechanism of tumors to escape immune surveillance.While an aberrant expression of the non-classical HLA-G antigen in human renal cell carcinoma (RCC) has been demonstrated to be associated with a worse outcome of patients and reduced sensitivity to immune effector cell-mediated cytotoxicity, the expression and function of HLA-E has not yet been analyzed in this tumor entity.Higher levels of HLA-E transcripts were detected in all RCC cell lines and tumor lesions, which were tested in comparison to normal kidney epithelium. Immunohistochemical staining of a tissue microarray (TMA) using the HLA-E-specific monoclonal antibody TFL-033 recognizing the cytoplasmic HLA-E α-chain as monomer revealed a heterogeneous HLA-E expression in RCC lesions with the highest frequency in chromophobe RCC when compared to other RCC subtypes. HLA-E expression did not correlate with the frequency of CD3+, CD4+, CD8+ and FoxP3+ immune cell infiltrations, but showed an inverse correlation with infiltrating CD56+ cells. In contrast to HLA-G, HLA-E expression in RCCs was not statistically significant associated with a decreased disease specific survival. These data suggest that HLA-E overexpression frequently occurs in RCC and correlates with reduced immunogenicity.

Immune regulation of canine tumour and macrophage PD-L1 expression

Expression of programmed cell death receptor ligand 1 (PD-L1) on tumor cells has been associated with immune escape in human and murine cancers, but little is known regarding the immune regulation of PD-L1 expression by tumor cells and tumor-infiltrating macrophages in dogs. Therefore, 14 canine tumor cell lines, as well as primary cultures of canine monocytes and macrophages, were evaluated for constitutive PD-L1 expression and for responsiveness to immune stimuli. We found that PD-L1 was expressed constitutively on all canine tumor cell lines evaluated, although the levels of basal expression were very variable. Significant upregulation of PD-L1 expression by all tumor cell lines was observed following IFN-γ exposure and by exposure to a TLR3 ligand. Canine monocytes and monocyte-derived macrophages did not express PD-L1 constitutively, but did significantly upregulate expression following treatment with IFN-γ. These findings suggest that most canine tumors express PD-L1 constitutively and that both innate and adaptive immune stimuli can further upregulate PD-L1 expression. Therefore the upregulation of PD-L1 expression by tumor cells and by tumor-infiltrating macrophages in response to cytokines such as IFN-γ may represent an important mechanism of tumor-mediated T-cell suppression in dogs as well as in humans.