IL-27 induces the expression of IDO and PD-L1 in human cancer cells

Adenosine increases PD-L1 expression in mesenchymal stromal cells derived from cervical cancer through its interaction with A2AR/A2BR and the production of TGF-β1

Mesenchymal stromal cells (MSCs) together with malignant cells present in the tumor microenvironment (TME), participate in the suppression of the antitumor immune response through the production of immunosuppressive factors, such as transforming growth factor beta 1 (TGF-β1). In previous studies, we reported that adenosine (Ado), generated by the adenosinergic activity of cervical cancer (CeCa) cells, induces the production of TGF-β1 by interacting with A2AR/A2BR. In the present study, we provide evidence that Ado induces the production of TGF-β1 in MSCs derived from CeCa tumors (CeCa-MSCs) by interacting with both receptors and that TGF-β1 acts in an autocrine manner to induce the expression of programmed death ligand 1 (PD-L1) in CeCa-MSCs, resulting in an increase in their immunosuppressive capacity on activated CD8+ T lymphocytes. The addition of the antagonists ZM241385 and MRS1754, specific for A2AR and A2BR, respectively, or SB-505124, a selective TGF-β1 receptor inhibitor, in CeCa-MSC cultures significantly inhibited the expression of PD-L1. Compared with CeCa-MSCs, MSCs derived from normal cervical tissue (NCx-MSCs), used as a control and induced with Ado to express PD-L1, showed a lower response to TGF-β1 to increase PD-L1 expression. Those results strongly suggest the presence of a feedback mechanism among the adenosinergic pathway, the production of TGF-β1, and the induction of PD-L1 in CeCa-MSCs to suppress the antitumor response of CD8+ T lymphocytes. The findings of this study suggest that this pathway may have clinical importance as a therapeutic target.

IL-27 in combination with anti-PD-1 can be anti-cancer or pro-cancer

Interleukin-27 (IL-27) is known to play opposing roles in immunology. The present paper considers, specifically, the role IL-27 plays in cancer immunotherapy when combined with immune checkpoint inhibitor anti-PD-1. We first develop a mathematical model for this combination therapy, by a system of Partial Differential Equations, and show agreement with experimental results in mice injected with melanoma cells. We then proceed to simulate tumor volume with IL-27 injection at a variable dose F and anti-PD-1 at a variable dose g. We show that in some range of "small" values of g, as f increases tumor volume decreases as long as fFc(g), where Fc(g) is a monotone increasing function of g. This demonstrates that IL-27 can be both anti-cancer and pro-cancer, depending on the ranges of both anti-PD-1 and IL-27.

From immune checkpoints to therapies: understanding immune checkpoint regulation and the influence of natural products and traditional medicine on immune checkpoint and immunotherapy in lung cancer

Lung cancer is a disease of global concern, and immunotherapy has brought lung cancer therapy to a new era. Besides promising effects in the clinical use of immune checkpoint inhibitors, immune-related adverse events (irAEs) and low response rates are problems unsolved. Natural products and traditional medicine with an immune-modulating nature have the property to influence immune checkpoint expression and can improve immunotherapy's effect with relatively low toxicity. This review summarizes currently approved immunotherapy and the current mechanisms known to regulate immune checkpoint expression in lung cancer. It lists natural products and traditional medicine capable of influencing immune checkpoints or synergizing with immunotherapy in lung cancer, exploring both their effects and underlying mechanisms. Future research on immune checkpoint modulation and immunotherapy combination applying natural products and traditional medicine will be based on a deeper understanding of their mechanisms regulating immune checkpoints. Continued exploration of natural products and traditional medicine holds the potential to enhance the efficacy and reduce the adverse reactions of immunotherapy.

The expression mechanism of programmed cell death 1 ligand 1 and its role in immunomodulatory ability of mesenchymal stem cells

Programmed cell death 1 ligand 1 (PD-L1) is an important immunosuppressive molecule, which inhibits the function of T cells and other immune cells by binding to the receptor programmed cell death-1. The PD-L1 expression disorder plays an important role in the occurrence, development, and treatment of sepsis or other inflammatory diseases, and has become an important target for the treatment of these diseases. Mesenchymal stem cells (MSCs) are a kind of pluripotent stem cells with multiple differentiation potential. In recent years, MSCs have been found to have a strong immunosuppressive ability and are used to treat various inflammatory insults caused by hyperimmune diseases. Moreover, PD-L1 is deeply involved in the immunosuppressive events of MSCs and plays an important role in the treatment of various diseases. In this review, we will summarize the main regulatory mechanism of PD-L1 expression, and discuss various biological functions of PD-L1 in the immune regulation of MSCs.

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.

Serum sPD-L1 levels are elevated in patients with viral diseases, bacterial sepsis or in patients with impaired renal function compared to healthy blood donors

OBJECTIVES

Immune checkpoints play an important role in maintaining the balance of the immune system and in the development of autoimmune diseases. A central checkpoint molecule is the programmed cell death protein 1 (PD-1, CD279) which is typically located on the surface of T cells. Its primary ligand PD-L1 is expressed on antigen presenting cells and on cancer cells. Several variants of PD-L1 exist, among these soluble molecules (sPD-L1) present in serum at low concentrations. sPD-L1 was found elevated in cancer and several other diseases. sPD-L1 in infectious diseases has received relatively little attention so far and is therefore subject of this study.

METHODS

sPD-L1 serum levels were determined in 170 patients with viral infections (influenza, varicella, measles, Dengue fever, SARS-CoV2) or bacterial sepsis by ELISA and compared to the levels obtained in 11 healthy controls.

RESULTS

Patients with viral infections and bacterial sepsis generally show significantly higher sPD-L1 serum levels compared to healthy donors, except for varicella samples where results do not reach significance. sPD-L1 is increased in patients with impaired renal function compared to those with normal renal function, and sPD-L1 correlates significantly with serum creatinine. Among sepsis patients with normal renal function, sPD-L1 serum levels are significantly higher in Gram-negative sepsis compared to Gram-positive sepsis. In addition, in sepsis patients with impaired renal function, sPD-L1 correlates positively with ferritin and negatively with transferrin.

CONCLUSIONS

sPD-L1 serum levels are significantly elevated in patients with sepsis, influenza, mesasles, Dengue fever or SARS-CoV2. Highest levels are detectable in patients with measles and Dengue fever. Also impaired renal function causes an increase in levels of sPD-L1. As a consequence, renal function has to be taken into account in the interpretation of sPD-L1 levels in patients.

IL-1β mediates the induction of immune checkpoint regulators IDO1 and PD-L1 in lung adenocarcinoma cells

INTRODUCTION

Inflammation plays a significant role in various cancers, including lung cancer, where the inflammatory cytokine IL-1β is often elevated in the tumor microenvironment. Patients with lung adenocarcinoma show higher levels of serum IL-1β compared to healthy individual. Moreover, IL-1β blockade reduces the incidence and mortality of lung cancer. Our prior studies revealed that alveolar type-II cells, the precursors for lung adenocarcinoma, display an induction in the expression of the enzyme tryptophan 2,3-dioxygenase (TDO2) during normal lung development. This induction of TDO2 coincides with an increase in IL-1β levels and is likely caused by IL-1β. Given that cancer cells can co-opt developmentally regulated pathways, we hypothesized that IL-1β may exert its pro-tumoral function by stimulating TDO2 and indoleamine 2, 3-dioxygenase-1 (IDO1), parallel enzymes involved in the conversion of tryptophan (Trp) into the immune-suppressive oncometabolite kynurenine (Kyn). Our goal was to determine whether IL-1β is a common upstream regulator of immune checkpoint regulators.

METHODS

To determine whether IL-1β regulates IDO1, TDO2, PD-L1, and PD-L2, we measured mRNA and protein levels in lung adenocarcinoma cells lines (A549, H1792, H1838, H2347, H2228, HCC364 and HCC827) grown in 2D or 3D and in immortalized normal lung epithelial cells (HBEC3-KT and HSAEC1-KT). To determine the importance of the NFκB pathway in mediating IL-1β -regulated cellular effects, we used siRNA to knockdown RelA/p65 in IL-1β treated cells. The levels of Trp and Kyn in the IL-1β-treated cells and media were measured by mass spectrometry.

RESULTS

Upon IL-1β stimulation, lung adenocarcinoma cells exhibited significant increases in IDO1 mRNA and protein levels, a response that depended on the NFκB pathway. Interestingly, this induction was more pronounced in 3D spheroid cultures compared to monolayer cultures and was not observed in normal immortalized lung epithelial cells. Furthermore, the conversion of Trp to Kyn increased in cells exposed to IL-1β, aligning with the heightened IDO1 expression. Remarkably, IL-1β also upregulated the expression of programmed death ligand-1 (PD-L1) and PD-L2 in multiple cell lines, indicating that IL-1β triggers parallel immune-suppressive mechanisms in lung adenocarcinoma cells.

CONCLUSIONS

Our studies demonstrate that lung adenocarcinoma cells, but not normal immortalized lung epithelial cells, respond to IL-1β signaling by inducing the expression of parallel immune checkpoint proteins that have the potential to promote immune evasion. Video Abstract.

Interleukin-27 potentiates CD8+ T-cell-mediated antitumor immunity in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) cells are highly dependent on interactions with the immunosuppressive tumor microenvironment (TME) for survival and proliferation. In the search for novel treatments, pro-inflammatory cytokines have emerged as candidates to reactivate the immune system. Among those, interleukin 27 (IL-27) has recently gained attention, but its effects differ among malignancies. Here, we utilized the Eμ-TCL1 and EBI3 knock-out mouse models as well as clinical samples from patients to investigate the role of IL-27 in CLL. Characterization of murine leukemic spleens revealed that the absence of IL-27 leads to enhanced CLL development and a more immunosuppressive TME in transgenic mice. Gene-profiling of T-cell subsets from EBI3 knock-out highlighted transcriptional changes in the CD8+ T-cell population associated with T-cell activation, proliferation, and cytotoxicity. We also observed an increased anti-tumor activity of CD8+ T cells in the presence of IL-27 ex vivo with murine and clinical samples. Notably, IL-27 treatment led to the reactivation of autologous T cells from CLL patients. Finally, we detected a decrease in IL-27 serum levels during CLL development in both pre-clinical and patient samples. Altogether, we demonstrated that IL-27 has a strong anti-tumorigenic role in CLL and postulate this cytokine as a promising treatment or adjuvant for this malignancy.

Interactions of IDO and the Kynurenine Pathway with Cell Transduction Systems and Metabolism at the Inflammation-Cancer Interface

The mechanisms underlying a relationship between inflammation and cancer are unclear, but much emphasis has been placed on the role of tryptophan metabolism to kynurenine and downstream metabolites, as these make a substantial contribution to the regulation of immune tolerance and susceptibility to cancer. The proposed link is supported by the induction of tryptophan metabolism by indoleamine-2,3-dioxygenase (IDO) or tryptophan-2,3-dioxygenase (TDO), in response to injury, infection or stress. This review will summarize the kynurenine pathway and will then focus on the bi-directional interactions with other transduction pathways and cancer-related factors. The kynurenine pathway can interact with and modify activity in many other transduction systems, potentially generating an extended web of effects other than the direct effects of kynurenine and its metabolites. Conversely, the pharmacological targeting of those other systems could greatly enhance the efficacy of changes in the kynurenine pathway. Indeed, manipulating those interacting pathways could affect inflammatory status and tumor development indirectly via the kynurenine pathway, while pharmacological modulation of the kynurenine pathway could indirectly influence anti-cancer protection. While current efforts are progressing to account for the failure of selective IDO1 inhibitors to inhibit tumor growth and to devise means of circumventing the issue, it is clear that there are wider factors involving the relationship between kynurenines and cancer that merit detailed consideration as alternative drug targets.

HIF1α-dependent and independent pathways regulate the expression of PD-L1 in prostate cancer

PD-L1/PD-1 pathway is a major pathway exploited by human cancer types, which is a target for current immunotherapy. We investigated tumor microenvironmental factors involved in PD-L1 induction in prostate cancer (PC). We studied the expression of PD-L1 in a series of 66 PCs, in parallel with the expression of hypoxia- and acidity-related immunohistochemical markers (Hypoxia-inducible factor HIF1α, and lactate dehydrogenase LDHA) and tumor-infiltrating lymphocyte TIL density. Experiments with three PC cell lines, the 22Rv1, DU145, and PC3 were conducted focusing on the inducibility of PD-L1 by hypoxia, acidity, lymphocyte interactions, and radiation. In tissues, PD-L1 expression by cancer cells was directly related to PD-L1 expression by  TILs and macrophages (p < 0.05), and the overexpression of HIF1α and LDH5 (p < 0.05). TIL density was inversely related to ΗΙF1α (p = 0.02). Exposure of PC cell lines to hypoxia strongly induced PD-L1 and protein and mRNA levels, directly controlled by HIF1α function (p < 0.001). Irradiation with 20 Gy had no apparent effect on PD-L1 expression. Culturing PC cell lines with culture medium (CM) from PBMCs strongly induced PD-L1 at protein and mRNA levels, independently from HIF1α, which was also confirmed when cells were incubated with Interferon-γ (p < 0.001). It is concluded that the combination of anti-PD-L1/PD-1 immunotherapy with hypoxia/HIF-targeting may be important in the treatment of specific subgroups of PC patients.

IFN-β activates cytotoxic function of human natural killer cells toward IL-27 and poly(I:C) stimulated PC3 and DU145 cells

Natural killer (NK) cell phenotype and function are altered in patients with prostate cancer, and increased NK cell activity is associated with a better prognosis in patients with disease. For patients with advanced stage prostate cancer, immunotherapies are a promising approach when standard treatment options have been exhausted. With the rapid emergence of NK cell-based therapies, it is important to understand the mechanisms by which NK cells can be triggered to kill cancer cells that have developed immune-evasive strategies. Altering the cytokine profiles of advanced prostate cancer cells may be an area to explore when considering ways in which NK cell activation can be modulated. We have previously demonstrated that combining the cytokine, IL-27, with TLR3 agonist, poly(I:C), changes cytokine secretion in the advanced prostate cancer models, PC3 and DU145 cells. Herein, we extend our previous work to study the effect of primary human NK cells on prostate cancer cell death in an in vitro co-culture model. Stimulating PC3 and DU145 cells with IL-27 and poly(I:C) induced IFN-β secretion, which was required for activation of primary human NK cells to kill these stimulated prostate cancer cells. PC3 cells were more sensitized to NK cell-mediated killing when compared to DU145 cells, which was attributed to differential levels of IFN-β produced in response to stimulation with IL-27 and poly(I:C). IFN-β increased granzyme B secretion and membrane-bound TRAIL expression by co-cultured NK cells. We further demonstrated that these NK cells killed PC3 cells in a partially TRAIL-dependent manner. This work provides mechanistic insight into how the cytotoxic function of NK cells can be improved to target cancer cells.

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.

Upregulation of programmed death ligand-1 in tumor-associated macrophages affects chemotherapeutic response in ovarian cancer cells

To better understand the mechanism of chemoresistance in ovarian cancer cells, we aimed to investigate the influence of macrophages on the tumor cell response to carboplatin and identify the genes associated with chemoresistance. We mimicked the tumor microenvironment (TME) using a co-culture technique and compared the proliferation of ovarian cells with and without macrophages. We also examined M1 and M2 marker expression and the expression of key TME genes. Post the co-culture, we treated ovarian cancer cells with carboplatin and elucidated the function of programmed death-ligand 1 (PD-L1) in carboplatin chemoresistance. We investigated CD68 and PD-L1 expression in normal and cancerous ovarian tissues using immunohistochemistry (IHC). Finally, we analyzed the association between CD68 or PD-L1 expression and survival outcomes. Inducible nitric oxide synthase (iNOS) was downregulated, while the gene expression of M2 macrophage markers was increased in ovarian cancer cells. PD-L1, vascular endothelial growth factor (VEGF), Interleukin (IL)-6, IL-10, IL-12, signal transducer and activator of transcription 3 (STAT3), B-cell lymphoma 2 (BCL2), multidrug resistance 1 (MDR1), and colony stimulating factor 1 (CSF-1) were upregulated. Notably, PD-L1 was upregulated in both the ovarian cancer cells and macrophages. Ovarian cancer cells co-cultured with macrophages exhibited statistically significant carboplatin resistance compared to single-cultured ovarian cancer cells. PD-L1 silencing induced chemosensitivity in both types of co-cultured ovarian cancer cells. However, IHC results revealed no correlation between PD-L1 expression and patient survival or cancer stage. CD68 expression was significantly increased in cancer cells compared to normal or benign ovarian tumor cells, but it was not associated with the survival outcomes of ovarian cancer patients. Our study demonstrated that ovarian cancer cells interact with macrophages to induce the M2 phenotype. We also established that PD-L1 upregulation in both ovarian cancer cells and macrophages is a key factor for carboplatin chemoresistance.

Research progress of therapeutic effects and drug resistance of immunotherapy based on PD-1/PD-L1 blockade

The binding of programmed death-1 (PD-1) on the surface of T cells and PD-1 ligand 1 (PD-L1) on tumor cells can prevent the immune-killing effect of T cells on tumor cells and promote the immune escape of tumor cells. Therefore, immune checkpoint blockade targeting PD-1/PD-L1 is a reliable tumor therapy with remarkable efficacy. However, the main challenges of this therapy are low response rate and acquired resistance, so that the outcomes of this therapy are usually unsatisfactory. This review begins with the description of biological structure of the PD-1/PD-L1 immune checkpoint and its role in a variety of cells. Subsequently, the therapeutic effects of immune checkpoint blockers (PD-1 / PD-L1 inhibitors) in various tumors were introduced and analyzed, and the reasons affecting the function of PD-1/PD-L1 were systematically analyzed. Then, we focused on analyzing, sorting out and introducing the possible underlying mechanisms of primary and acquired resistance to PD-1/PD-L1 blockade including abnormal expression of PD-1/PD-L1 and some factors, immune-related pathways, tumor immune microenvironment, and T cell dysfunction and others. Finally, promising therapeutic strategies to sensitize the resistant patients with PD-1/PD-L1 blockade treatment were described. This review is aimed at providing guidance for the treatment of various tumors, and highlighting the drug resistance mechanisms to offer directions for future tumor treatment and improvement of patient prognosis.

Therapeutic Management of Metastatic Clear Cell Renal Cell Carcinoma: A Revolution in Every Decade

Clear cell renal cell carcinoma (RCC) oncogenesis is mainly driven by VHL gene inactivation, leading to overexpression of vascular endothelial growth factor (VEGF). The use of tyrosine-kinase inhibitors (TKIs) directed against VEGF and its receptor (VEGFR) revolutionised the management of metastatic renal cancer in the 2000s. The more recent development of next-generation TKIs such as cabozantinib or lenvatinib has made it possible to bypass some of the mechanisms of resistance to first-generation anti-VEGFR TKIs. During the decade 2010-2020, the development of immune checkpoint blockade (ICB) therapies revolutionised the management of many solid cancers, including RCC, in first- and subsequent-line settings. Dual ICB or ICB plus anti-VEGFR TKI combinations are now the standard of care for patients with advanced clear cell RCC. To optimise these combination therapies while preserving patient quality of life, escalation and de-escalation strategies are being evaluated in prospective randomised trials, based on patient selection according to their prognosis risk. Finally, new therapeutic approaches, such as targeting hypoxia-inducible factor (HIF) and the development of innovative treatments using antibody-drug conjugates (ADCs), CAR-T cells, or radiopharmaceuticals, are all potential candidates to improve further patient survival.

Pathways of Angiogenic and Inflammatory Cytokines in Multiple Myeloma: Role in Plasma Cell Clonal Expansion and Drug Resistance

Multiple myeloma (MM) is the second most common hematological malignancy, and despite the introduction of innovative therapies, remains an incurable disease. Identifying early and minimally or non-invasive biomarkers for predicting clinical outcomes and therapeutic responses is an active field of investigation. Malignant plasma cells (PCs) reside in the bone marrow (BM) microenvironment (BMME) which comprises cells (e.g., tumour, immune, stromal cells), components of the extracellular matrix (ECM) and vesicular and non-vesicular (soluble) molecules, all factors that support PCs’ survival and proliferation. The interaction between PCs and BM stromal cells (BMSCs), a hallmark of MM progression, is based not only on intercellular interactions but also on autocrine and paracrine circuits mediated by soluble or vesicular components. In fact, PCs and BMSCs secrete various cytokines, including angiogenic cytokines, essential for the formation of specialized niches called “osteoblastic and vascular niches”, thus supporting neovascularization and bone disease, vital processes that modulate the pathophysiological PCs–BMME interactions, and ultimately promoting disease progression. Here, we aim to discuss the roles of cytokines and growth factors in pathogenetic pathways in MM and as prognostic and predictive biomarkers. We also discuss the potential of targeted drugs that simultaneously block PCs’ proliferation and survival, PCs–BMSCs interactions and BMSCs activity, which may represent the future goal of MM therapy.

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.

Multi-Omics Approaches for the Prediction of Clinical Endpoints after Immunotherapy in Non-Small Cell Lung Cancer: A Comprehensive Review

Immune checkpoint inhibitors (ICI) have revolutionized the management of locally advanced and advanced non-small lung cancer (NSCLC). With an improvement in the overall survival (OS) as both first- and second-line treatments, ICIs, and especially programmed-death 1 (PD-1) and programmed-death ligands 1 (PD-L1), changed the landscape of thoracic oncology. The PD-L1 level of expression is commonly accepted as the most used biomarker, with both prognostic and predictive values. However, even in a low expression level of PD-L1, response rates remain significant while a significant number of patients will experience hyperprogression or adverse events. The dentification of such subtypes is thus of paramount importance. While several studies focused mainly on the prediction of the PD-L1 expression status, others aimed directly at the development of prediction/prognostic models. The response to ICIs depends on a complex physiopathological cascade, intricating multiple mechanisms from the molecular to the macroscopic level. With the high-throughput extraction of features, omics approaches aim for the most comprehensive assessment of each patient. In this article, we will review the place of the different biomarkers (clinical, biological, genomics, transcriptomics, proteomics and radiomics), their clinical implementation and discuss the most recent trends projecting on the future steps in prediction modeling in NSCLC patients treated with ICI.

Ezrin Contributes to the Plasma Membrane Expression of PD-L1 in A2780 Cells

Programmed death ligand–1 (PD–L1) is one of the immune checkpoint molecule localized on the plasma membrane of numerous cancer cells that negatively regulates T-cell-mediated immunosurveillance. Despite the remarkable efficacy and safety profile of immune checkpoint inhibitors (ICIs), such as anti-PD–L1 antibodies, restricted poor therapeutic responses to ICIs are often observed in patients with ovarian cancer. Because higher expression of PD–L1 in advanced ovarian cancer is associated with a decreased survival rate, identifying the potential molecules to regulate the plasma membrane expression of PD–L1 may provide a novel therapeutic strategy to improve the efficacy of ICIs against ovarian cancers. Here, we reveal the involvement of the ezrin/radixin/moesin (ERM) family, which crosslinks transmembrane proteins with the actin cytoskeleton by serving as a scaffold protein, in the plasma membrane expression of PD–L1 in the human epithelial ovarian cancer cell line A2780. Our results demonstrate that PD–L1 and all three ERMs were expressed at the mRNA and protein levels in A2780 cells, and that PD–L1 was highly colocalized with ezrin and moesin, but moderately with radixin, in the plasma membrane. Interestingly, RNA interference-mediated gene silencing of ezrin, but not of radixin or moesin, substantially reduced the plasma membrane expression of PD–L1 without altering its mRNA expression. In conclusion, our results indicate that ezrin may be responsible for the plasma membrane expression of PD–L1, possibly by serving as a scaffold protein in A2780 cells. Ezrin is a potential therapeutic target for improving the efficacy of ICIs against ovarian cancers.

Interleukin-27 Regulates the Function of the Gastrointestinal Epithelial Barrier in a Human Tissue-Derived Organoid Model

A treatment with direct healing effects on the gastrointestinal epithelial barrier is desirable for inflammatory bowel disease (IBD). Interleukin-27 (IL-27) is an immunoregulatory cytokine, and oral delivery is an effective treatment in murine models of IBD. We aimed to define IL-27 effects on the human gastrointestinal epithelial barrier. We characterised gene and protein expression of permeability mediators in a human colon-derived organoid model. Functional permeability was determined in an organoid-derived 2D monolayer by transepithelial electrical resistance. IL-27 effects on epithelial innate immune responses were assessed through expression of cytokines, anti-microbial peptides and MUC genes. IL-27 effects on wound healing and proliferation were determined in human colon epithelial cell lines. IL-27 led to restoration of permeability regulation following inflammatory cytokine insult (p = 0.001), associated with differential expression of tight junction mediators with decrease in claudin 2 (p = 0.024) and increase in claudin 4 (p < 0.001), E-cadherin (p < 0.001) and zona occludens (p = 0.0014). IL-27 evoked differential gene expression of epithelial-derived innate immune responses (reduced IL1B and IL18, and increased IL33, HBD1, MUC1 and MUC2; p < 0.012). IL-27 induced epithelial barrier wound healing through restitution (p < 0.001), and increased proliferation (p < 0.001) following injury. Overall, IL-27 provokes mucosal healing of the human gastrointestinal epithelial barrier.

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.

The Lymph Node Microenvironment May Invigorate Cancer Cells With Enhanced Metastatic Capacities

Cancer metastasis, a typical malignant biological behavior involving the distant migration of tumor cells from the primary site to other organs, contributed majorly to cancer-related deaths of patients. Although constant efforts have been paid by researchers to elucidate the mechanisms of cancer metastasis, we are still far away from the definite answer. Recently, emerging evidence demonstrated that cancer metastasis is a continuous coevolutionary process mediated by the interactions between tumor cells and the host organ microenvironment, and epigenetic reprogramming of metastatic cancer cells may confer them with stronger metastatic capacities. The lymph node served as the first metastatic niche for many types of cancer, and the appearance of lymph node metastasis predicted poor prognosis. Importantly, multiple immune cells and stromal cells station and linger in the lymph nodes, which constitutes the complexity of the lymph node microenvironment. The active cross talk between cancer cells and immune cells could happen unceasingly within the metastatic environment of lymph nodes. Of note, diverse immune cells have been found to participate in the formation of malignant properties of tumor, including stemness and immune escape. Based on these available evidence and data, we hypothesize that the metastatic microenvironment of lymph nodes could drive cancer cells to metastasize to further organs through epigenetic mechanisms.

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.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review (Part 6): Correlation of PD-L1 Expression with the Status of Mismatch Repair System, BRCA, PTEN, and Other Genes

Pembrolizumab (anti-PD-1) is allowed in selected metastatic castration-resistant prostate cancer (PC) patients showing microsatellite instability/mismatch repair system deficiency (MSI-H/dMMR). BRCA1/2 loss-of-function is linked to hereditary PCs and homologous recombination DNA-repair system deficiency: poly-ADP-ribose-polymerase inhibitors can be administered to BRCA-mutated PC patients. Recently, docetaxel-refractory metastatic castration-resistant PC patients with BRCA1/2 or ATM somatic mutations had higher response rates to pembrolizumab. PTEN regulates cell cycle/proliferation/apoptosis through pathways including the AKT/mTOR, which upregulates PD-L1 expression in PC. Our systematic literature review (PRISMA guidelines) investigated the potential correlations between PD-L1 and MMR/MSI/BRCA/PTEN statuses in PC, discussing few other relevant genes. Excluding selection biases, 74/677 (11%) PCs showed dMMR/MSI; 8/67 (12%) of dMMR/MSI cases were PD-L1+. dMMR-PCs included ductal (3%) and acinar (14%) PCs (all cases tested for MSI were acinar-PCs). In total, 15/39 (39%) PCs harbored BRCA1/2 aberrations: limited data are available for PD-L1 expression in these patients. 13/137 (10%) PTEN- PCs were PD-L1+; 10/29 (35%) PD-L1+ PCs showed PTEN negativity. SPOP mutations may increase PD-L1 levels, while the potential correlation between PD-L1 and ERG expression in PC should be clarified. Further research should verify how the efficacy of PD-1 inhibitors in metastatic castration-resistant PCs is related to dMMR/MSI, DNA-damage repair genes defects, or PD-L1 expression.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 7: PD-L1 Expression in Liquid Biopsy

Liquid biopsy is an accessible, non-invasive diagnostic tool for advanced prostate cancer (PC) patients, potentially representing a real-time monitoring test for tumor evolution and response to treatment through the analysis of circulating tumor cells (CTCs) and exosomes. We performed a systematic literature review (PRISMA guidelines) to describe the current knowledge about PD-L1 expression in liquid biopsies of PC patients: 101/159 (64%) cases revealed a variable number of PD-L1+ CTCs. Outcome correlations should be investigated in larger series. Nuclear PD-L1 expression by CTCs was occasionally associated with worse prognosis. Treatment (abiraterone, enzalutamide, radiotherapy, checkpoint-inhibitors) influenced PD-L1+ CTC levels. Discordance in PD-L1 status was detected between primary vs. metastatic PC tissue biopsies and CTCs vs. corresponding tumor tissues. PD-L1 is also released by PC cells through soluble exosomes, which could inhibit the T cell function, causing immune evasion. PD-L1+ PC-CTC monitoring and genomic profiling may better characterize the ongoing aggressive PC forms compared to PD-L1 evaluation on primary tumor biopsies/prostatectomy specimens (sometimes sampled a long time before recurrence/progression). Myeloid-derived suppressor cells and dendritic cells (DCs), which may have immune-suppressive effects in tumor microenvironment, have been found in PC patients circulation, sometimes expressing PD-L1. Occasionally, their levels correlated to clinical outcome. Enzalutamide-progressing castration-resistant PC patients revealed increased PD-1+ T cells and circulating PD-L1/2+ DCs.

Regulation of the Immune Checkpoint Indoleamine 2,3-Dioxygenase Expression by Epstein-Barr Virus

Epstein-Barr virus (EBV) is an oncovirus ubiquitously distributed and associated with different types of cancer. The reason why only a group of infected people develop cancer is still unknown. EBV-associated cancers represent about 1.8% of all cancer deaths worldwide, with more than 150,000 new cases of cancer being reported annually. Since EBV-associated cancers are described as more aggressive and more resistant to the usual treatment compared to EBV-negative ones, the recent introduction of monoclonal antibodies (mAbs) targeting immune checkpoints (ICs) in the treatment of cancer patients represents a possible therapy for EBV-associated diseases. However, the current mAb therapies available still need improvement, since a group of patients do not respond well to treatment. Therefore, the main objective of this review is to summarize the progress made regarding the contribution of EBV infection to the expression of the IC indoleamine 2,3-dioxygenase (IDO) thus far. This IC has the potential to be used as a target in new immune therapies, such as mAbs. We hope that this work helps the development of future immunotherapies, improving the prognosis of EBV-associated cancer patients.

Crosstalk between macrophages and natural killer cells in the tumor microenvironment

The tumor microenvironment (TME) is jointly constructed by a variety of cell types, including tumor cells, immune cells, fibroblasts, and epithelial cells, among others. The cells within the TME interact with each other and with tumor cells to influence tumor development and progression. As the most abundant immune cells in the TME, macrophages regulate the immune network by not only secreting a large amount of versatile cytokines but also expressing a series of ligands or receptors on the surface to interact with other cells directly. Due to their strong plasticity, they exert both immunostimulatory and immunosuppressive effects in the complex TME. The major effector cells of the immune system that directly target cancer cells include but are not limited to natural killer cells (NKs), dendritic cells (DCs), macrophages, polymorphonuclear leukocytes, mast cells, and cytotoxic T lymphocytes (CTLs). Among them, NK cells are the predominant innate lymphocyte subsets that mediate antitumor and antiviral responses. The activation and inhibition of NK cells are regulated by cytokines and the balance between activating and inhibitory receptors. There is an inextricable regulatory relationship between macrophages and NK cells. Herein, we systematically elaborate on the regulatory network between macrophages and NK cells through soluble mediator crosstalk and cell-to-cell interactions. We believe that a better understanding of the crosstalk between macrophages and NKs in the TME will benefit the development of novel macrophage- or NK cell-focused therapeutic strategies with superior efficacies in cancer therapy.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 5: Epigenetic Regulation of PD-L1

Epigenetic alterations (including DNA methylation or miRNAs) influence oncogene/oncosuppressor gene expression without changing the DNA sequence. Prostate cancer (PC) displays a complex genetic and epigenetic regulation of cell-growth pathways and tumor progression. We performed a systematic literature review (following PRISMA guidelines) focused on the epigenetic regulation of PD-L1 expression in PC. In PC cell lines, CpG island methylation of the CD274 promoter negatively regulated PD-L1 expression. Histone modifiers also influence the PD-L1 transcription rate: the deletion or silencing of the histone modifiers MLL3/MML1 can positively regulate PD-L1 expression. Epigenetic drugs (EDs) may be promising in reprogramming tumor cells, reversing epigenetic modifications, and cancer immune evasion. EDs promoting a chromatin-inactive transcriptional state (such as bromodomain or p300/CBP inhibitors) downregulated PD-L1, while EDs favoring a chromatin-active state (i.e., histone deacetylase inhibitors) increased PD-L1 expression. miRNAs can regulate PD-L1 at a post-transcriptional level. miR-195/miR-16 were negatively associated with PD-L1 expression and positively correlated to longer biochemical recurrence-free survival; they also enhanced the radiotherapy efficacy in PC cell lines. miR-197 and miR-200a-c positively correlated to PD-L1 mRNA levels and inversely correlated to the methylation of PD-L1 promoter in a large series. miR-570, miR-34a and miR-513 may also be involved in epigenetic regulation.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 3: PD-L1, Intracellular Signaling Pathways and Tumor Microenvironment

The tumor microenvironment (TME) includes immune (T, B, NK, dendritic), stromal, mesenchymal, endothelial, adipocytic cells, extracellular matrix, and cytokines/chemokines/soluble factors regulating various intracellular signaling pathways (ISP) in tumor cells. TME influences the survival/progression of prostate cancer (PC), enabling tumor cell immune-evasion also through the activation of the PD-1/PD-L1 axis. We have performed a systematic literature review according to the PRISMA guidelines, to investigate how the PD-1/PD-L1 pathway is influenced by TME and ISPs. Tumor immune-escape mechanisms include suppression/exhaustion of tumor infiltrating cytotoxic T lymphocytes, inhibition of tumor suppressive NK cells, increase in immune-suppressive immune cells (regulatory T, M2 macrophagic, myeloid-derived suppressor, dendritic, stromal, and adipocytic cells). IFN-γ (the most investigated factor), TGF-β, TNF-α, IL-6, IL-17, IL-15, IL-27, complement factor C5a, and other soluble molecules secreted by TME components (and sometimes increased in patients' serum), as well as and hypoxia, influenced the regulation of PD-L1. Experimental studies using human and mouse PC cell lines (derived from either androgen-sensitive or androgen-resistant tumors) revealed that the intracellular ERK/MEK, Akt-mTOR, NF-kB, WNT and JAK/STAT pathways were involved in PD-L1 upregulation in PC. Blocking the PD-1/PD-L1 signaling by using immunotherapy drugs can prevent tumor immune-escape, increasing the anti-tumor activity of immune cells.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 1: Focus on Immunohistochemical Results with Discussion of Pre-Analytical and Interpretation Variables

Immunotherapy targeting the PD-1-PD-L1 axis yielded good results in treating different immunologically ''hot'' tumors. A phase II study revealed good therapeutic activity of pembrolizumab in selected prostatic carcinoma (PC)-patients. We performed a systematic literature review (PRISMA guidelines), which analyzes the immunohistochemical expression of PD-L1 in human PC samples and highlights the pre-analytical and interpretation variables. Interestingly, 29% acinar PCs, 7% ductal PCs, and 46% neuroendocrine carcinomas/tumors were PD-L1+ on immunohistochemistry. Different scoring methods or cut-off criteria were applied on variable specimen-types, evaluating tumors showing different clinic-pathologic features. The positivity rate of different PD-L1 antibody clones in tumor cells ranged from 3% (SP142) to 50% (ABM4E54), excluding the single case tested for RM-320. The most tested clone was E1L3N, followed by 22C3 (most used for pembrolizumab eligibility), SP263, SP142, and 28-8, which gave the positivity rates of 35%, 11-41% (depending on different scoring systems), 6%, 3%, and 15%, respectively. Other clones were tested in <200 cases. The PD-L1 positivity rate was usually higher in tumors than benign tissues. It was higher in non-tissue microarray specimens (41-50% vs. 15%), as PC cells frequently showed heterogenous or focal PD-L1-staining. PD-L1 was expressed by immune or stromal cells in 12% and 69% cases, respectively. Tumor heterogeneity, inter-institutional preanalytics, and inter-observer interpretation variability may account for result biases.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 4: Experimental Treatments in Pre-Clinical Studies (Cell Lines and Mouse Models)

In prostate cancer (PC), the PD-1/PD-L1 axis regulates various signaling pathways and it is influenced by extracellular factors. Pre-clinical experimental studies investigating the effects of various treatments (alone or combined) may discover how to overcome the immunotherapy-resistance in PC-patients. We performed a systematic literature review (PRISMA guidelines) to delineate the landscape of pre-clinical studies (including cell lines and mouse models) that tested treatments with effects on PD-L1 signaling in PC. NF-kB, MEK, JAK, or STAT inhibitors on human/mouse, primary/metastatic PC-cell lines variably down-modulated PD-L1-expression, reducing chemoresistance and tumor cell migration. If PC-cells were co-cultured with NK, CD8+ T-cells or CAR-T cells, the immune cell cytotoxicity increased when PD-L1 was downregulated (opposite effects for PD-L1 upregulation). In mouse models, radiotherapy, CDK4/6-inhibitors, and RB deletion induced PD-L1-upregulation, causing PC-immune-evasion. Epigenetic drugs may reduce PD-L1 expression. In some PC experimental models, blocking only the PD-1/PD-L1 pathway had limited efficacy in reducing the tumor growth. Anti-tumor effects could be increased by combining the PD-1/PD-L1 blockade with other approaches (inhibitors of tyrosine kinase, PI3K/mTOR or JAK/STAT3 pathways, p300/CBP; anti-RANKL and/or anti-CTLA-4 antibodies; cytokines; nitroxoline; DNA/cell vaccines; radiotherapy/Radium-223).

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 2: Clinic-Pathologic Correlations

Many studies have investigated the potential prognostic and predictive role of PD-L1 in prostatic carcinoma (PC). We performed a systematic literature review (PRISMA guidelines) to critically evaluate human tissue-based studies (immunohistochemistry, molecular analysis, etc.), experimental research (cell lines, mouse models), and clinical trials. Despite some controversial results and study limitations, PD-L1 expression by tumor cells may be related to clinic-pathologic features of adverse outcome, including advanced tumor stage (high pT, presence of lymph node, and distant metastases), positivity of surgical margins, high Grade Group, and castration resistance. Different PD-L1 positivity rates may be observed in matched primary PCs and various metastatic sites of the same patients. Over-fixation, type/duration of decalcification, and PD-L1 antibody clone may influence the immunohistochemical analysis of PD-L1 on bone metastases. PD-L1 seemed expressed more frequently by castration-resistant PCs (49%) as compared to hormone-sensitive PCs (17%). Some series found that PD-L1 positivity was associated with decreased time to castration resistance. Treatment with ipilimumab, cyclophosphamide/GVAX/degarelix, or degarelix alone may increase PD-L1 expression. Correlation of PD-L1 positivity with overall survival and outcomes related to tumor recurrence were rarely investigated; the few analyzed series produced conflicting results and sometimes showed limitations. Further studies are required. The testing and scoring of PD-L1 should be standardized.

Folate receptor-mediated delivery of 1-MDT-loaded mesoporous silica magnetic nanoparticles to target breast cancer cells

Aims: The efficiency of mesoporous silica magnetic nanoparticles (MSMNP) as a targeted drug-delivery system was investigated. Methods: The superparamagnetic iron oxide nanoparticles (NP) were synthesized, coated with mesoporous silica and conjugated with polyethylene glycol and methotrexate. Next, 1-methyl-D-tryptophan was loaded into the prepared nanosystems (NS). They were characterized using transmission electron microscopy, scanning electron microscopy, dynamic light scattering, vibrating sample magnetometer, x-ray powder diffraction, Fourier transform-infrared spectroscopy and the Brunauer-Emmett-Teller method and their biological impacts on breast cancer cells were evaluated. Results: The prepared NSs displayed suitable properties and showed enhanced internalization by folate-receptor-expressing cells, exerting efficient cytotoxicity, which was further enhanced by the near-infrared radiation irradiation. Conclusion: On the basis of our findings, the engineered NS is a promising multifunctional nanomedicine/theranostic for solid tumors.

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.

IL-27 Mediates PD-L1 Expression and Release by Human Mesothelioma Cells

Malignant mesothelioma (MM) is a rare tumor with an unfavorable prognosis. MM genesis involves asbestos-mediated local inflammation, supported by several cytokines, including IL-6. Recent data showed that targeting PD-1/PD-L1 is an effective therapy in MM. Here, we investigated the effects of IL-6 trans-signaling and the IL-6-related cytokine IL-27 on human MM cells in vitro by Western blot analysis of STAT1/3 phosphorylation. The effects on PD-L1 expression were tested by qRT-PCR and flow-cytometry and the release of soluble (s)PD-L1 by ELISA. We also measured the concentrations of sPD-L1 and, by multiplexed immunoassay, IL-6 and IL-27 in pleural fluids obtained from 77 patients in relation to survival. IL-27 predominantly mediates STAT1 phosphorylation and increases PD-L1 gene and surface protein expression and sPD-L1 release by human MM cells in vitro. IL-6 has limited activity, whereas a sIL-6R/IL-6 chimeric protein mediates trans-signaling predominantly via STAT3 phosphorylation but has no effect on PD-L1 expression and release. IL-6, IL-27, and sPD-L1 are present in pleural fluids and show a negative correlation with overall survival, but only IL-27 shows a moderate albeit significant correlation with sPD-L1 levels. Altogether these data suggest a potential role of IL-27 in PD-L1-driven immune resistance in MM.

Intravenous administration of LPS activates the kynurenine pathway in healthy male human subjects: a prospective placebo-controlled cross-over trial

Background

Administration of lipopolysaccharide (LPS) from Gram-negative bacteria, also known as the human endotoxemia model, is a standardized and safe model of human inflammation. Experimental studies have revealed that peripheral administration of LPS leads to induction of the kynurenine pathway followed by depressive-like behavior and cognitive dysfunction in animals. The aim of the present study is to investigate how acute intravenous LPS administration affects the kynurenine pathway in healthy male human subjects.

Methods

The present study is a prospective, single-blinded, randomized, placebo-controlled cross-over study to investigate the effects of intravenously administered LPS (Escherichia coli O113, 2 ng/kg) on tryptophan and kynurenine metabolites over 48 h and their association with interleukin-6 (IL-6) and C-reactive protein (CRP). The study included 10 healthy, non-smoking men (18–40 years) free from medication. Statistical differences in tryptophan and kynurenine metabolites as well as associations with IL-6 and CRP in LPS and placebo treated subjects were assessed with linear mixed-effects models.

Results

Systemic injection of LPS was associated with significantly lower concentrations of plasma tryptophan and kynurenine after 4 h, as well as higher concentrations of quinolinic acid (QUIN) after 48 h compared to the placebo injection. No differences were found in kynurenic acid (KYNA) or picolinic acid plasma concentrations between LPS or placebo treatment. The KYNA/kynurenine ratio peaked at 6 h post LPS injection while QUIN/kynurenine maintained significantly higher from 3 h post LPS injection until 24 h. The kynurenine/tryptophan ratio was higher at 24 h and 48 h post LPS treatment. Finally, we report an association between the kynurenine/tryptophan ratio and CRP.

Conclusions

Our findings strongly support the concept that an inflammatory challenge with LPS induces the kynurenine pathway in humans, activating both the neurotoxic (QUIN) and neuroprotective (KYNA) branch of the kynurenine pathway.

Trial registration

This study is based on a study registered at ClinicalTrials.gov, NCT03392701. Registered 21 December 2017.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02196-x.

EGR3-HDAC6-IL-27 Axis Mediates Allergic Inflammation and Is Necessary for Tumorigenic Potential of Cancer Cells Enhanced by Allergic Inflammation-Promoted Cellular Interactions

The objective of this study was to investigate mechanisms of allergic inflammation both in vitro and in vivo in details. For this, RNA sequencing was performed. Early growth response 3 gene (Egr3) was one of the most highly upregulated genes in rat basophilic leukemia (RBL2H3) cells stimulated by antigen. The role of Egr3 in allergic inflammation has not been studied extensively. Egr3 was necessary for passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA). Egr3 promoter sequences contained potential binding site for NF-κB p65. NF-κB p65 directly regulated Egr3 expression and mediated allergic inflammation in vitro. Histone deacetylases (HDACs) is known to be involved in allergic airway inflammation. HDAC6 promoter sequences contained potential binding site for EGR3. EGR3 showed binding to promoter sequences of HDAC6. EGR3 was necessary for increased expression of histone deacetylase 6 (HDAC6) in antigen-stimulated RBL2H3 cells. HDAC6 mediated allergic inflammation in vitro and PSA. TargetScan analysis predicted that miR-182-5p was a negative regulator of EGR3. Luciferase activity assay confirmed that miR-182-5p was a direct regulator of EGR3. MiR-182-5p mimic inhibited allergic inflammation both in vitro and in vivo. Cytokine array showed that HDAC6 was necessary for increased interleukin-27 (IL-27) expression in BALB/C mouse model of PSA. Antigen stimulation did not affect expression of EBI3, another subunit of IL-27 in RBL2H3 cells or BALB/C mouse model of PCA or PSA. IL-27 receptor alpha was shown to be able to bind to HDAC6. IL-27 p28 mediated allergic inflammation in vitro, PCA, and PSA. Mouse recombinant IL-27 protein promoted features of allergic inflammation in an antigen-independent manner. HDAC6 was necessary for tumorigenic and metastatic potential enhanced by PSA. PSA enhanced the metastatic potential of mouse melanoma B16F1 cells in an IL-27-dependent manner. Experiments employing culture medium and mouse recombinant IL-27 protein showed that IL-27 mediated and promoted cellular interactions involving B16F1 cells, lung macrophages, and mast cells during allergic inflammation. IL-27 was present in exosomes of antigen-stimulated RBL2H3 cells. Exosomes from antigen-stimulated RBL2H3 cells enhanced invasion of B16F1 melanoma cells in an IL-27-dependemt manner. These results present evidence that EGR3-HDAC6-IL-27 axis can regulate allergic inflammation by mediating cellular interactions.

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.

IL-30† (IL-27A): a familiar stranger in immunity, inflammation, and cancer

Over the years, interleukin (IL)-27 has received much attention because of its highly divergent, sometimes even opposing, functions in immunity. IL-30, the p28 subunit that forms IL-27 together with Ebi3 and is also known as IL-27p28 or IL-27A, has been considered a surrogate to represent IL-27. However, it was later discovered that IL-30 can form complexes with other protein subunits, potentially leading to overlapping or discrete functions. Furthermore, there is emerging evidence that IL-30 itself may perform immunomodulatory functions independent of Ebi3 or other binding partners and that IL-30 production is strongly associated with certain cancers in humans. In this review, we will discuss the biology of IL-30 and other IL-30-associated cytokines and their functions in inflammation and cancer.

Studying the ways that interleukin IL-30 regulates immune responses may provide novel insights into tumor development and inflammatory conditions. Interleukins are a diverse family of proteins involved in intercellular communications and immunity, where they can exert divergent and even opposing functions. Booki Min at Northwestern University in Chicago, USA, and co-workers reviewed the current understanding of IL-30 and its links to inflammation and cancer. IL-30 forms the IL-27 complex with the Ebi3 protein and was thought to be a surrogate for IL-27 in terms of activity. However, recent insights suggest that IL-30 may perform discrete immune modulation functions. Elevated IL-30 secretion is linked to prostate and breast cancer development. Extensive research is needed into the formation of IL-30, its associated protein interactions, and the development of a suitable animal model.

Mechanisms of PD-L1 Regulation in Malignant and Virus-Infected Cells

Programmed cell death protein 1 (PD-1), a receptor on T cells, and its ligand, PD-L1, have been a topic of much interest in cancer research. Both tumour and virus-infected cells can upregulate PD-L1 to suppress cytotoxic T-cell killing. Research on the PD-1/PD-L1 axis has led to the development of anti-PD-1/PD-L1 immune checkpoint blockades (ICBs) as promising cancer therapies. Although effective in some cancer patients, for many, this form of treatment is ineffective due to a lack of immunogenicity in the tumour microenvironment (TME). Despite the development of therapies targeting the PD-1/PD-L1 axis, the mechanisms and pathways through which these proteins are regulated are not completely understood. In this review, we discuss the latest research on molecules of inflammation and innate immunity that regulate PD-L1 expression, how its expression is regulated during viral infection, and how it is modulated by different cancer therapies. We also highlight existing research on the development of different combination therapies with anti-PD-1/PD-L1 antibodies. This information can be used to develop better cancer immunotherapies that take into consideration the pathways involved in the PD-1/PD-L1 axis, so these molecules do not reduce their efficacy, which is currently seen with some cancer therapies. This review will also assist in understanding how the TME changes during treatment, which will provide further rationale for combination therapies.

Indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors in clinical trials for cancer immunotherapy

Indoleamine 2,3-dioxygenase 1 (IDO1) is a heme enzyme that catalyzes the oxidation of L-tryptophan. Functionally, IDO1 has played a pivotal role in cancer immune escape via catalyzing the initial step of the kynurenine pathway, and overexpression of IDO1 is also associated with poor prognosis in various cancers. Currently, several small-molecule candidates and peptide vaccines are currently being assessed in clinical trials. Furthermore, the "proteolysis targeting chimera" (PROTAC) technology has also been successfully used in the development of IDO1 degraders, providing novel therapeutics for cancers. Herein, we review the biological functions of IDO1, structural biology and also extensively summarize medicinal chemistry strategies for the development of IDO1 inhibitors in clinical trials. The emerging PROTAC-based IDO1 degraders are also highlighted. This review may provide a comprehensive and updated overview on IDO1 inhibitors and their therapeutic potentials.

The Dual Role of STAT1 in Ovarian Cancer: Insight Into Molecular Mechanisms and Application Potentials

The signal transducer and activator of transcription 1 (STAT1) is a transducer protein and acts as a transcription factor but its role in ovarian cancer (OC) is not completely understood. Practically, there are two-faced effects of STAT1 on tumorigenesis in different kinds of cancers. Existing evidence reveals that STAT1 has both tumor-suppressing and tumor-promoting functions involved in angiogenesis, cell proliferation, migration, invasion, apoptosis, drug resistance, stemness, and immune responses mainly through interacting and regulating target genes at multiple levels. The canonical STAT1 signaling pathway shows that STAT1 is phosphorylated and activated by the receptor-activated kinases such as Janus kinase in response to interferon stimulation. The STAT1 signaling can also be crosstalk with other signaling such as transforming growth factor-β signaling involved in cancer cell behavior. OC is often diagnosed at an advanced stage due to symptomless or atypical symptoms and the lack of effective detection at an early stage. Furthermore, patients with OC often develop chemoresistance and recurrence. This review focuses on the multi-faced role of STAT1 and highlights the molecular mechanisms and biological functions of STAT1 in OC.

Tryptophan Metabolism via Kynurenine Pathway: Role in Solid Organ Transplantation

Solid organ transplantation is a gold standard treatment for patients suffering from an end-stage organ disease. Patient and graft survival have vastly improved during the last couple of decades; however, the field of transplantation still encounters several unique challenges, such as a shortage of transplantable organs and increasing pool of extended criteria donor (ECD) organs, which are extremely prone to ischemia-reperfusion injury (IRI), risk of graft rejection and challenges in immune regulation. Moreover, accurate and specific biomarkers, which can timely predict allograft dysfunction and/or rejection, are lacking. The essential amino acid tryptophan and, especially, its metabolites via the kynurenine pathway has been widely studied as a contributor and a therapeutic target in various diseases, such as neuropsychiatric, autoimmune disorders, allergies, infections and malignancies. The tryptophan-kynurenine pathway has also gained interest in solid organ transplantation and a variety of experimental studies investigating its role both in IRI and immune regulation after allograft implantation was first published. In this review, the current evidence regarding the role of tryptophan and its metabolites in solid organ transplantation is presented, giving insights into molecular mechanisms and into therapeutic and diagnostic/prognostic possibilities.

IFN-γ and CD38 in Hyperprogressive Cancer Development

Immune checkpoint inhibitors (ICIs) improve the survival of patients with multiple types of cancer. However, low response rates and atypical responses limit their success in clinical applications. The paradoxical acceleration of tumor growth after treatment, defined as hyperprogressive disease (HPD), is the most difficult problem facing clinicians and patients alike. The mechanisms that underlie hyperprogression (HP) are still unclear and controversial, although different factors are associated with the phenomenon. In this review, we propose two factors that have not yet been demonstrated to be directly associated with HP, but upon which it is important to focus attention. IFN-γ is a key cytokine in antitumor response and its levels increase during ICI therapy, whereas CD38 is an alternative immune checkpoint that is involved in immunosuppressive responses. As both factors are associated with resistance to ICI therapy, we have discussed their possible involvement in HPD with the conclusion that IFN-γ may contribute to HP onset through the activation of the inflammasome pathway, immunosuppressive enzyme IDO1 and activation-induced cell death (AICD) in effector T cells, while the role of CD38 in HP may be associated with the activation of adenosine receptors, hypoxia pathways and AICD-dependent T-cell depletion.

PD-L1/PD-1 Pattern of Expression Within the Bone Marrow Immune Microenvironment in Smoldering Myeloma and Active Multiple Myeloma Patients

Background

The PD-1/PD-L1 axis has recently emerged as an immune checkpoint that controls antitumor immune responses also in hematological malignancies. However, the use of anti-PD-L1/PD-1 antibodies in multiple myeloma (MM) patients still remains debated, at least in part because of discordant literature data on PD-L1/PD-1 expression by MM cells and bone marrow (BM) microenvironment cells. The unmet need to identify patients which could benefit from this therapeutic approach prompts us to evaluate the BM expression profile of PD-L1/PD-1 axis across the different stages of the monoclonal gammopathies.

Methods

The PD-L1/PD-1 axis was evaluated by flow cytometry in the BM samples of a total cohort of 141 patients with monoclonal gammopathies including 24 patients with Monoclonal Gammopathy of Undetermined Significance (MGUS), 38 patients with smoldering MM (SMM), and 79 patients with active MM, including either newly diagnosed or relapsed-refractory patients. Then, data were correlated with the main immunological and clinical features of the patients.

Results

First, we did not find any significant difference between MM and SMM patients in terms of PD-L1/PD-1 expression, on both BM myeloid (CD14⁺) and lymphoid subsets. On the other hand, PD-L1 expression by CD138⁺ MM cells was higher in both SMM and MM as compared to MGUS patients. Second, the analysis on the total cohort of MM and SMM patients revealed that PD-L1 is expressed at higher level in CD14⁺CD16⁺ non-classical monocytes compared with classical CD14⁺CD16⁻ cells, independently from the stage of disease. Moreover, PD-L1 expression on CD14⁺ cells was inversely correlated with BM serum levels of the anti-tumoral cytokine, IL-27. Interestingly, relapsed MM patients showed an inverted CD4⁺/CD8⁺ ratio along with high levels of pro-tumoral IL-6 and a positive correlation between %CD14⁺PD-L1⁺ and %CD8⁺PD-1⁺ cells as compared to both SMM and newly diagnosed MM patients suggesting a highly compromised immune-compartment with low amount of CD4⁺ effector cells.

Conclusions

Our data indicate that SMM and active MM patients share a similar PD-L1/PD-1 BM immune profile, suggesting that SMM patients could be an interesting target for PD-L1/PD-1 inhibition therapy, in light of their less compromised and more responsive immune-compartment.

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.

IL-12 Family Cytokines in Cancer and Immunotherapy

The IL-12 family cytokines are a group of unique heterodimeric cytokines that include IL-12, IL-23, IL-27, IL-35 and, most recently, IL-39. Recent studies have solidified the importance of IL-12 cytokines in shaping innate and adaptive immune responses in cancer and identified multipronged roles for distinct IL-12 family members, ranging from effector to regulatory immune functions. These cytokines could serve as promising candidates for the development of immunomodulatory therapeutic approaches. Overall, IL-12 can be considered an effector cytokine and has been found to engage anti-tumor immunity by activating the effector Th1 response, which is required for the activation of cytotoxic T and NK cells and tumor clearance. IL-23 and IL-27 play dual roles in tumor immunity, as they can both activate effector immune responses and promote tumor growth by favoring immune suppression. IL-35 is a potent regulatory cytokine and plays a largely pro-tumorigenic role by inhibiting effector T cells. In this review, we summarize the recent findings on IL-12 family cytokines in the control of tumor growth with an emphasis primarily on immune regulation. We underscore the clinical implications for the use of these cytokines either in the setting of monotherapy or in combination with other conventional therapies for the more effective treatment of malignancies.