B7-H1 Is Expressed by Human Endothelial Cells and Suppresses T Cell Cytokine Synthesis

Reprogramming endothelial cells to empower cancer immunotherapy

Cancer immunity is subject to spatiotemporal regulation by leukocyte interaction with the tumor microenvironment. Growing evidence suggests an emerging role for the vasculature in tumor immune evasion and immunotherapy resistance. Beyond the conventional functions of the tumor vasculature, such as providing oxygen and nutrients to support tumor progression, we propose multiplex mechanisms for vascular regulation of tumor immunity: The immunosuppressive vascular niche locoregionally educates circulation-derived immune cells by angiocrines, aberrant endothelial metabolism induces T cell exclusion and inactivation, and topologically and biochemically abnormal vascularity forms a pathophysiological barrier that hampers lymphocyte infiltration. We postulate that genetic and metabolic reprogramming of endothelial cells may rewire the immunosuppressive vascular microenvironment to overcome immunotherapy resistance, serving as a next-generation vascular targeting strategy for cancer treatment.

PD-L1-positive circulating endothelial progenitor cells associated with immune response to PD-1 blockade in patients with head and neck squamous cell carcinoma

A number of the inhibitors against programmed death protein 1 (PD-1) have been approved to treat recurrent or metastatic squamous cell carcinoma of head and neck (HNSCC). The interaction between PD-1 and its ligand (PD-L1) serves as an immune checkpoint that governs cytotoxic immune effectors against tumors. Numerous clinical trials of PD-1/PD-L1 inhibitors have so far been discordant about having sufficient PD-L1 expression in the tumor as a prerequisite for a successful anti-PD-1 treatment. On the other hand, vascular endothelial cells modulate immune activities through PD-L1 expression, and thus it is possible that the expressions of circulating endothelial cells (CECs) and circulating endothelial progenitor cells (CPCs) could affect antitumor immunity as well as neoangiogenesis. Here we investigated the potential involvement of PD-L1+ CECs and PD-L1+ CPCs in PD-1 blockade treatments for HNSCC patients. We measured CD8+ T cells, CECs, and CPCs in the peripheral blood of the HNSCC patients treated by anti-PD-1 therapies. We found that their PD-L1+ CPC expression before anti-PD1 therapies was strongly correlated with treatment responses and overall survival. Moreover, if the first infusion of PD-1 inhibitors reduced ≥ 50% PD-L1+ CPCs, a significantly better outcome could be predicted. In these patients as well as in an animal model of oral cancer, Pd-l1+ CPC expression was associated with limited CD8+ T-cell infiltration into the tumors, and anti-PD-1 treatments also targeted Pd-l1+ CPCs and increased CD8+ T-cell infiltration. Our results highlight PD-L1+ CPC as a potential regulator in the anti-PD-1 treatments for HNSCC.

Sex-oriented perspectives in immunopharmacology

Several immunopharmacological agents are effective in the treatment of cancer and immune-mediated conditions, with a favorable impact on life expectancy and clinical outcomes for a large number of patients. Nevertheless, response variation and undesirable effects of these drugs represent major issues, and overall efficacy remains unpredictable. Males and females show a distinct difference in immune system responses, with females generally mounting stronger responses to a variety of stimuli. Therefore, exploring sex differences in the efficacy and safety of immunopharmacological agents would strengthen the practice of precision medicine. As a pharmacological target highlight, programmed cell death 1 ligand 1 (PD-L1) is the first functionally characterized ligand of the coinhibitory programmed death receptor 1 (PD-1). The PD-L1/PD-1 crosstalk plays an important role in the immune response and is relevant in cancer, infectious and autoimmune disease. Sex differences in the response to immune checkpoint inhibitors are well documented, with male patients responding better than female patients. Similarly, higher efficacy of and adherence to tumor necrosis factor inhibitors in chronic inflammatory conditions including rheumatoid arthritis and Crohn's disease have been reported in male patients. The pharmacological basis of sex-specific responses to immune system modulating drugs is actively investigated in other settings such as stroke and type 1 diabetes. Advances in therapeutics targeting the endothelium could soon be wielded against autoimmunity and metabolic disorders. Based on the established sexual dimorphism in immune-related pathophysiology and disease presentation, sex-specific immunopharmacological protocols should be integrated into clinical guidelines.

Targeting endothelial permeability in the EPR effect

The characteristics of the primary tumor blood vessels and the tumor microenvironment drive the enhanced permeability and retention (EPR) effect, which confers an advantage towards enhanced delivery of anti-cancer nanomedicine and has shown beneficial effects in preclinical models. Increased vascular permeability is a landmark feature of the tumor vessels and an important driver of the EPR. The main focus of this review is the endothelial regulation of vascular permeability. We discuss current challenges of targeting vascular permeability towards clinical translation and summarize the structural components and mechanisms of endothelial permeability, the principal mediators and signaling players, the targeted approaches that have been used and their outcomes to date. We also critically discuss the effects of the tumor-infiltrating immune cells, their interplay with the tumor vessels and the impact of immune responses on nanomedicine delivery, the impact of anti-angiogenic and tumor-stroma targeting approaches, and desirable nanoparticle design approaches for greater translational benefit.

Camrelizumab combined with apatinib in patients with first-line platinum-resistant or PD-1 inhibitor resistant recurrent/metastatic nasopharyngeal carcinoma: a single-arm, phase 2 trial

Immunotherapy combined with antiangiogenic targeted therapy has improved the treatment of certain solid tumors, but effective regimens remain elusive for refractory recurrent/metastatic nasopharyngeal carcinoma (RM-NPC). We conducted a phase 2 trial to evaluate the safety and activity of camrelizumab plus apatinib in platinum-resistant (cohort 1, NCT04547088) and PD-1 inhibitor resistant NPC (cohort 2, NCT04548271). Here we report on the primary outcome of objective response rate (ORR) and secondary endpoints of safety, duration of response, disease control rate, progression-free survival, and overall survival. The primary endpoint of ORR was met for cohort 1 (65%, 95% CI, 49.6-80.4, n = 40) and cohort 2 (34.3%; 95% CI, 17.0-51.8, n = 32). Grade ≥ 3 treatment-related adverse events (TRAE) were reported in 47 (65.3%) of 72 patients. Results of our predefined exploratory investigation of predictive biomarkers show: B cell markers are the most differentially expressed genes in the tumors of responders versus non-responders in cohort 1 and that tertiary lymphoid structure is associated with higher ORR; Angiogenesis gene expression signatures are strongly associated with ORR in cohort 2. Camrelizumab plus apatinib combination effectiveness is associated with high expression of PD-L1, VEGF Receptor 2 and B-cell-related genes signatures. Camrelizumab plus apatinib shows promising efficacy with a measurable safety profile in RM-NPC patients.

Interdependencies of the Neuronal, Immune and Tumor Microenvironment in Gliomas

Gliomas are the most common primary brain malignancy and are universally fatal. Despite significant breakthrough in understanding tumor biology, treatment breakthroughs have been limited. There is a growing appreciation that major limitations on effective treatment are related to the unique and highly complex glioma tumor microenvironment (TME). The TME consists of multiple different cell types, broadly categorized into tumoral, immune and non-tumoral, non-immune cells. Each group provides significant influence on the others, generating a pro-tumor dynamic with significant immunosuppression. In addition, glioma cells are highly heterogenous with various molecular distinctions on the cellular level. These variations, in turn, lead to their own unique influence on the TME. To develop future treatments, an understanding of this complex TME interplay is needed. To this end, we describe the TME in adult gliomas through interactions between its various components and through various glioma molecular phenotypes.

Sex-dependent PD-L1/sPD-L1 trafficking in human endothelial cells in response to inflammatory cytokines and VEGF

Programmed cell death 1 ligand 1 (PD-L1) expressed in non-immune cells is involved in immune-mediated tissue damage in the context of inflammatory conditions and tumor immune escape. Emerging evidence suggests soluble (s)PD-L1 as a marker of inflammation. Based on well-established sex-specific differences in immunity, we tested the novel hypotheses that (i) endothelial cell PD-L1 is modulated by inflammatory cytokines and vascular endothelial growth factor (VEGF) in a sex-specific fashion, and (ii) the endothelium is a source of sPD-L1. After exposure of human umbilical vein endothelial cells (HUVECs) to lipopolysaccharide, interleukin (IL)1β or VEGF for 24 h, total PD-L1 levels were upregulated solely in cells from female donors, while being unchanged in those from male donors. Accordingly, exposure to synovial fluids from patients with inflammatory arthritis upregulated PD-L1 levels in HUVECs from female donors only. Membrane PD-L1 expression as measured by flow cytometry was unchanged in response to inflammatory stimuli. However, exposure to 2 ng/mL IL-1β or 50 ng/mL VEGF time-dependently increased sPD-L1 release by HUVECs from female donors. Treatment with the metalloproteinase (MMP) inhibitor GM6001 (10 μM) prevented IL-1β-induced sPD-L1 release and enhanced membrane PD-L1 levels. The anti-VEGF agents bevacizumab and sunitinib reduced both VEGF-induced PD-L1 accumulation and sPD-L1 secretion. Thus, inflammatory agents and VEGF rapidly increased endothelial PD-L1 levels in a sex-specific fashion. Furthermore, the vascular endothelium may be a sPD-L1 source, whose production is MMP-dependent and modulated by anti-VEGF agents. These findings may have implications for sex-specific immunity, vascular inflammation and response to anti-angiogenic therapy.

Role of regulation of PD-1 and PD-L1 expression in sepsis

Long term immunosuppression is problematic during sepsis. The PD-1 and PD-L1 immune checkpoint proteins have potent immunosuppressive functions. Recent studies have revealed several features of PD-1 and PD-L1 and their roles in sepsis. Here, we summarize the overall findings of PD-1 and PD-L1 by first reviewing the biological features of PD-1 and PD-L1 and then discussing the mechanisms that control the expression of PD-1 and PD-L1. We then review the functions of PD-1 and PD-L1 in physiological settings and further discuss PD-1 and PD-L1 in sepsis, including their involvement in several sepsis-related processes and their potential therapeutic relevance in sepsis. In general, PD-1 and PD-L1 have critical roles in sepsis, indicating that their regulation may be a potential therapeutic target for sepsis.

Diagnostic Predictors of Immunotherapy Response in Head and Neck Squamous Cell Carcinoma

Programmed cell death ligand-1 (PD-L1) binds PD-1 on CD⁸⁺ lymphocytes, inhibiting their cytotoxic action. Its aberrant expression by head and neck squamous cell carcinoma (HNSCC) cells leads to immune escape. Pembrolizumab and nivolumab, two humanized monoclonal antibodies against PD-1, have been approved in HNSCC treatment, but ~60% of patients with recurrent or metastatic HNSCC fail to respond to immunotherapy and only 20 to 30% of treated patients have long-term benefits. The purpose of this review is to analyze all the fragmentary evidence present in the literature to identify what future diagnostic markers could be useful for predicting, together with PD-L1 CPS, the response to immunotherapy and its durability. We searched PubMed, Embase, and the Cochrane Register of Controlled Trials and we summarize the evidence collected in this review. We confirmed that PD-L1 CPS is a predictor of response to immunotherapy, but it should be measured across multiple biopsies and repeatedly over time. PD-L2, IFN-γ, EGFR, VEGF, TGF-β, TMB, blood TMB, CD73, TILs, alternative splicing, tumor microenvironment, and some macroscopic and radiological features are promising predictors worthy of further studies. Studies comparing predictors appear to give greater potency to TMB and CXCR9.

PD-1 expression in transbronchial biopsies of lung transplant recipients is a possible early predictor of rejection

Introduction

Chronic lung allograft dysfunction (CLAD) is the main cause of the reduced survival of lung transplanted (LTx) patients. The possible role of immune checkpoint molecules in establishing tolerance has been scarcely investigated in the setting of lung transplantation.

Methods

We conducted a retrospective, observational pilot study on a consecutive series of transbronchial cryobiopsies (TCB) obtained from 24 patients during LTx follow-up focusing on PD-1, one of the most investigated immune checkpoint molecules.

Results

Results showed that PD-1-expressing T lymphocytes were present in all TCB with a histological diagnosis of acute rejection (AR; 9/9), but not in most (11/15) of the TCB not resulting in a diagnosis of AR (p=0.0006). Notably, the presence of PD-1-expressing T lymphocytes in TCB resulted in a 10-times higher risk of developing chronic lung allograft dysfunction (CLAD), the main cause of the reduced survival of lung transplanted patients, thus being associated with a clearly worst clinical outcome.

Discussion

Results of this pilot study indicate a central role of PD-1 in the development of AR and its evolution towards CLAD and suggest that the evaluation of PD-1-expressing lymphocytes in TCB could offer a prognostic advantage in monitoring the onset of AR in patients who underwent lung transplantation.

An arginase1- and PD-L1-derived peptide-based vaccine for myeloproliferative neoplasms: A first-in-man clinical trial

Introduction

Arginase-1 (ARG1) and Programed death ligand-1 (PD-L1) play a vital role in immunosuppression in myeloproliferative neoplasms (MPNs) and directly inhibit T-cell activation and proliferation. We previously identified spontaneous T-cell responses towards PD-L1 and ARG1 derived peptide epitopes in patients with MPNs. In the present First-in-Man study we tested dual vaccinations of ARG1- derived and PD-L1-derived peptides, combined with Montanide ISA-51 as adjuvant, in patients with Janus Kinase 2 (JAK2) V617F-mutated MPN.

Methods

Safety and efficacy of vaccination with ARG1- derived and PD-L1-derived peptides with montanide as an adjuvant was tested in 9 patients with MPN The primary end point was safety and toxicity evaluation. The secondary end point was assessment of the immune response to the vaccination epitope (www.clinicaltrials.gov identifier NCT04051307).

Results

The study included 9 patients with JAK2-mutant MPN of which 8 received all 24 planned vaccines within a 9-month treatment period. Patients reported only grade 1 and 2 vaccine related adverse events. No alterations in peripheral blood counts were identified, and serial measurements of the JAK2V617F allelic burden showed that none of the patients achieved a molecular response during the treatment period. The vaccines induced strong immune responses against both ARG1 and PD-L1- derived epitopes in the peripheral blood of all patients, and vaccine-specific skin-infiltrating lymphocytes from 5/6 patients could be expanded in vitro after a delayed-type hypersensitivity test. In two patients we also detected both ARG1- and PD-L1-specific T cells in bone marrow samples at the end of trial. Intracellular cytokine staining revealed IFNγ and TNFγ producing CD4⁺- and CD8⁺- T cells specific against both vaccine epitopes. Throughout the study, the peripheral CD8/CD4 ratio increased significantly, and the CD8⁺ TEMRA subpopulation was enlarged. We also identified a significant decrease in PD-L1 mRNA expression in CD14⁺ myeloid cells in the peripheral blood in all treated patients and a decrease in ARG1 mRNA expression in bone marrow of 6 out of 7 evaluated patients.

Conclusion

Overall, the ARG1- and PD-L1-derived vaccines were safe and tolerable and induced strong T-cell responses in all patients. These results warrant further studies of the vaccine in other settings or in combination with additional immune-activating treatments.

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.

The role of immune checkpoints in cardiovascular disease

Immune checkpoint inhibitors (ICI) are monoclonal antibodies which bind to immune checkpoints (IC) and their ligands to prevent inhibition of T-cell activation by tumor cells. Currently, multiple ICI are approved targeting Cytotoxic T-lymphocyte antigen 4 (CTLA-4), Programmed Death Protein 1 (PD-1) and its ligand PD-L1, and Lymphocyte-activation gene 3 (LAG-3). This therapy has provided potent anti-tumor effects and improved prognosis for many cancer patients. However, due to systemic effects, patients can develop immune related adverse events (irAE), including possible life threatening cardiovascular irAE, like atherosclerosis, myocarditis and cardiomyopathy. Inhibition of vascular IC is associated with increased atherosclerotic burden and plaque instability. IC protect against atherosclerosis by inhibiting T-cell activity and cytokine production, promoting regulatory T-cell differentiation and inducing T-cell exhaustion. In addition, PD-L1 on endothelial cells might promote plaque stability by reducing apoptosis and increasing expression of tight junction molecules. In the heart, IC downregulate the immune response to protect against cardiac injury by reducing T-cell activity and migration. Here, inhibition of IC could induce life-threatening T-cell-mediated-myocarditis. One proposed purpose behind lymphocyte infiltration is reaction to cardiac antigens, caused by decreased self-tolerance, and thereby increased autoimmunity because of IC inhibition. In addition, there are several reports of ICI-mediated cardiomyopathy with immunoglobulin G expression on cardiomyocytes, indicating an autoimmune response. IC are mostly known due to their cardiotoxicity. However, t his review compiles current knowledge on mechanisms behind IC function in cardiovascular disease with the aim of providing an overview of possible therapeutic targets in prevention or treatment of cardiovascular irAEs.

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.

Beyond Cancer: Regulation and Function of PD-L1 in Health and Immune-Related Diseases

Programmed Cell Death 1 Ligand 1 (PD-L1, CD274, B7-H1) is a transmembrane protein which is strongly involved in immune modulation, serving as checkpoint regulator. Interaction with its receptor, Programmed Cell Death Protein 1 (PD-1), induces an immune-suppressive signal, which modulates the activity of T cells and other effector cells. This mediates peripheral tolerance and contributes to tumor immune escape. PD-L1 became famous due to its deployment in cancer therapy, where blockage of PD-L1 with the help of therapeutic antagonistic antibodies achieved impressive clinical responses by reactivating effector cell functions against tumor cells. Therefore, in the past, the focus has been placed on PD-L1 expression and its function in various malignant cells, whereas its role in healthy tissue and diseases apart from cancer remained largely neglected. In this review, we summarize the function of PD-L1 in non-cancerous cells, outlining its discovery and origin, as well as its involvement in different cellular and immune-related processes. We provide an overview of transcriptional and translational regulation, and expression patterns of PD-L1 in different cells and organs, and illuminate the involvement of PD-L1 in different autoimmune diseases as well as in the context of transplantation and pregnancy.

Immunorthodontics: PD-L1, a Novel Immunomodulator in Cementoblasts, Is Regulated by HIF-1α under Hypoxia

Recent studies have revealed that hypoxia alters the PD-L1 expression in periodontal cells. HIF-1α is a key regulator for PD-L1. As hypoxia presents a hallmark of an orthodontically induced microenvironment, hypoxic stimulation of PD-L1 expression may play vital roles in immunorthodontics and orthodontically induced inflammatory root resorption (OIIRR). This study aims to investigate the hypoxic regulation of PD-L1 in cementoblasts, and its interaction with hypoxia-induced HIF-1α expression. The cementoblast (OCCM-30) cells (M. Somerman, NIH, NIDCR, Bethesda, Maryland) were cultured in the presence and absence of cobalt (II) chloride (CoCl2). Protein expression of PD-L1 and HIF-1α as well as their gene expression were evaluated by Western blotting and RT-qPCR. Immunofluorescence was applied to visualize the localization of the proteins within cells. The HIF-1α inhibitor (HY-111387, MedChemExpress) was added, and CRISPR/Cas9 plasmid targeting HIF-1α was transferred for further investigation by flow cytometry analysis. Under hypoxic conditions, cementoblasts undergo an up-regulation of PD-L1 expression at protein and mRNA levels. Silencing of HIF-1α using CRISPR/Cas9 indicated a major positive correlation with HIF-1α in regulating PD-L1 expression. Taken together, these findings show the influence of hypoxia on PD-L1 expression is modulated in a HIF-1α dependent manner. The HIF-1α/PD-L1 pathway may play a role in the immune response of cementoblasts. Thus, combined HIF-1α/PD-L1 inhibition could be of possible therapeutic relevance for OIIRR prevention.

Treatment with eFT-508 increases chemosensitivity in breast cancer cells by modulating the tumor microenvironment

Background

Patients with triple-negative breast cancer (TNBC) are better responders to neoadjuvant chemotherapy; however, they are poor in the durability of response with decreased overall and progression-free survival.

Methods

Given that significant improvements have been reported with PD-L1-PD-1 blockade in different cancers, we evaluated the in vitro and in vivo effectiveness of Tomivosertib (eFT-508), an anthracycline, adriamycin, and MNK1/2 inhibitor, which has been previously shown to inhibit translation of PD-L1 in mice model of liver cancer, alone or in combination using BC cell lines and an orthotopic xenograft mice model using the TNBC cell line MDA-MB-231.

Results

Within the context of The Cancer Genome Atlas (TCGA) dataset, expression of CD274 mRNA, which encodes programmed death-ligand 1 (PD-L1), was found to be significantly overexpressed in TNBC patients compared to patients with HER2 + or luminal breast cancer (BC). Even within TNBC sub-types, CD274 expression was significantly higher in the immune modulatory subtype (TNBC-IM).

BC cells exhibited high IC₅₀ = 0.85 ± 0.07 nM with Adriamycin and significantly lower IC₅₀ = 0.23 ± 0.04 nM with eFT-508 (P < 0.01). Combination treatment showed in vitro synergism on chemosensitivity. Combination therapy also exhibited a synergistic effect on inhibition of tumor growth and lung colonization in vivo. Mass cytometry-based evaluation of the tumor microenvironment revealed significant attenuation of both PD-L1 and PD-L2 following mono- or combination therapy with eFT-508.

Conclusions

Treatment with eFT-508 restored effector and cytotoxic function of tumor-infiltrating CD8 + T cells in mice. The remarkable efficacy observed both in vitro and in vivo, and clinical synergism with adriamycin, highlights the potential of eFT-508 as an alternative, yet more efficacious, therapeutic option for patients with TNBC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03474-9.

Hypermutation as a potential predictive biomarker of immunotherapy efficacy in high-grade gliomas: a broken dream?

A high tumor mutational burden and mismatch repair deficiency are observed in 'hypermutated' high-grade gliomas (HGGs); however, the molecular characterization of this distinct subtype and whether it predicts the response to immune checkpoint inhibitors (ICIs) are largely unknown. Pembrolizumab is a valid therapeutic option for the treatment of hypermutated cancers of diverse origin, but only a few clinical trials have explored the activity of ICIs in hypermutated HGGs. HGGs appear to differ from other cancers, likely due to the prevalence of subclonal versus clonal neoantigens, which are unable to elicit an immune response with ICIs. The main aim of this review is to summarize the current knowledge on hypermutation in HGGs, focusing on the broken promises of tumor mutational burden and mismatch repair deficiency as potential biomarkers of response to ICIs.

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.

Targeting HIF-1α abrogates PD-L1-mediated immune evasion in tumor microenvironment but promotes tolerance in normal tissues

Anti-CTLA-4 + anti-PD-1/PD-L1 combination is the most effective cancer immunotherapy but causes high incidence of immune-related adverse events (irAE). Here we report that targeting of HIF-1α suppressed PD-L1 expression on tumor cells and tumor-infiltrated myeloid cells, but unexpectedly induced PD-L1 in normal tissues by an IFNγ-dependent mechanism. Targeting the HIF-1α-PD-L1 axis in tumor cells reactivated tumor-infiltrating lymphocytes (TILs) and caused tumor rejection. The HIF-1α inhibitor echinomycin potentiated cancer immunotherapeutic effects of anti-CTLA-4 therapy with efficacy comparable to anti-CTLA-4+anti-PD-1 antibodies. However, while anti-PD-1 exacerbated irAE triggered by Ipilimumab, echinomycin protected mice against irAE by increasing PD-L1 levels in normal tissues. Our data suggest that targeting HIF-1α fortifies the immune tolerance function of the PD-1:PD-L1 checkpoint in normal tissues but abrogates its immune evasion function in the tumor microenvironment (TME) to achieve safer and more effective immunotherapy.

Blockade or deficiency of PD-L1 expression in intestinal allograft accelerates graft tissue injury in mice

The importance of PD-1/PD-L1 interaction to alloimmune response is unknown in intestinal transplantation. We tested whether PD-L1 regulates allograft tissue injury in murine intestinal transplantation. PD-L1 expression was observed on the endothelium and immune cells in the intestinal allograft. Monoclonal antibody treatment against PD-L1 led to accelerated allograft tissue damage, characterized by severe cellular infiltrations, massive destruction of villi, and increased crypt apoptosis in the graft. Interestingly, PD-L1^-/- allografts were more severely rejected than wild-type allografts, but the presence or absence of PD-L1 in recipients did not affect the degree of allograft injury. PD-L1^-/- allografts showed increased infiltrating Ly6G⁺ and CD11b⁺ cells in lamina propria on day 4, whereas the degree of CD4⁺ or CD8⁺ T cell infiltration was comparable to wild-type allografts. Gene expression analysis revealed that PD-L1^-/- allografts had increased mRNA expressions of Cxcr2, S100a8/9, Nox1, IL1rL1, IL1r2, and Nos2 in the lamina propria cells on day 4. Taken together, study results suggest that PD-L1 expression in the intestinal allograft, but not in the recipient, plays a critical role in mitigating allograft tissue damage in the early phase after transplantation. The PD-1/PD-L1 interaction may contribute to immune regulation of the intestinal allograft via the innate immune system.

The cross-talk between tumor-associated macrophages and tumor endothelium: Recent advances in macrophage-based cancer immunotherapy

Tumor-associated macrophages (TAMs) are among the abundant cell populations of the tumor microenvironment (TME), which have pivotal roles in tumor development, chemoresistance, immune evasion, and metastasis. Growing evidence indicates that TAMs and the cross-talk between TAMs and tumoral endothelial cells can substantially contribute to tumor angiogenesis, which is considered a vital process for cancer development. Besides, tumoral endothelial cells can regulate the leukocyte infiltration to the TME in solid cancers and contribute to immune evasion. Therefore, targeting the immunosuppressive TAMs and the cross-talk between them can be a promising strategy for improving anti-tumoral immune responses. This review aims to summarize the biology of TAMs, their recently identified roles in tumor development/angiogenesis, and recent advances in macrophage-based cancer immunotherapy approaches for treating cancers.

Predictive molecular markers for the treatment with immune checkpoint inhibitors in colorectal cancer

Colorectal cancer is one of the most common malignant tumors and, hence, has become one of the most important public health issues in the world. Treatment with immune checkpoint inhibitors (ICIs) successfully improves the survival rate of patients with melanoma, non-small-cell lung cancer, and other malignancies, and its application in metastatic colorectal cancer is being actively explored. However, a few patients develop drug resistance. Predictive molecular markers are important tools to precisely screen patient groups that can benefit from treatment with ICIs. The current article focused on certain important predictive molecular markers for ICI treatment in colorectal cancer, including not only some of the mature molecular markers, such as deficient mismatch repair (d-MMR), microsatellite instability-high (MSI-H), tumor mutational burden (TMB), programmed death-ligand-1 (PD-L1), tumor immune microenvironment (TiME), and tumor-infiltrating lymphocytes (TILs), but also some of the novel molecular markers, such as DNA polymerase epsilon (POLE), polymerase delta 1 (POLD1), circulating tumor DNA (ctDNA), and consensus molecular subtypes (CMS). We have reviewed these markers in-depth and presented the results from certain important studies, which suggest their applicability in CRC and indicate their advantages and disadvantages. We hope this article is helpful for clinicians and researchers to systematically understand these markers and can guide the treatment of colorectal cancer.

Enabling CAR-T cells for solid tumors: Rage against the suppressive tumor microenvironment

Adoptive T cell therapies based on chimeric antigen receptors (CAR-T) are emerging as genuine therapeutic options for the treatment of hematological malignancies. The observed clinical success has not yet been extended into solid tumor indications as a result of multiple factors including immunosuppressive features of the tumor microenvironment (TME). In this context, an emerging strategy is to design CAR-T cells for the elimination of defined cellular components of the TME, with the objective of re-shaping the tumor immune contexture to control tumor growth. Relevant cell components that are currently under investigation as targets of CAR-T therapies include the tumor vasculature, cancer-associated fibroblasts (CAFs), and immunosuppressive tumor associated macrophages (TAMs) and myeloid derived suppressor cells (MDSCs). In this review, we recapitulate the rapidly expanding field of CAR-T cell therapies that directly target cellular components within the TME with the ultimate objective of promoting immune function, either alone or in combination with other cancer therapies.

Cisplatin and gemcitabine exert opposite effects on immunotherapy with PD-1 antibody in K-ras-driven cancer

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Two common chemotherapeutic drugs, cisplatin and gemcitabine, exert opposite effect on the efficacy of PD-1 antibody in K-ras-driven cancers.

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Gemcitabine antagonizes PD-1Ab due to its inhibition on T cell infiltration in tumor tissues.

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Combination PD-1Ab and cisplatin leads to complete tumor eradication in vivo due to activation of the cGAS-mediated immune response.

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The impact of drugs on T cell functions should be considered as a critical factor in selecting drugs for immunochemotherapy to achieve optimal therapeutic outcome.

Introduction

Immunochemotherapy using PD-1/PD-L1 antibodies in combination with chemotherapeutic agents has become a mainstream treatment for cancer patients, but it remains unclear which drug combinations would produce best therapeutic outcome.

Objectives

The purpose of this study was to investigate two common chemotherapeutic drugs, gemcitabine and cisplatin, for their impacts on the therapeutic efficacy of PD-1 antibody in K-ras-driven cancers known to overexpress PD-L1.

Methods

Both in vitro assays and syngeneic mouse tumor models were used in this study. Biochemical and molecular assays were used to determine the effects of drugs on T cell functions in cell culture models and in mouse/human tumor tissues. Allograft tumor models with K-ras mutation were used to investigate the combination effect of gemcitabine or cisplatin with immunotherapy. Data of lung cancer patients with K-ras mutation treated with cisplatin and toripalimab were analyzed to evaluate the clinical relevance of the lab findings.

Results

Cisplatin and gemcitabine unexpectedly exert opposite effect on the therapeutic activity of PD-1 antibody in vivo. Gemcitabine antagonizes the therapeutic effect of PD-1 antibody due to its significant inhibition on CD8⁺ T cell infiltration, which was observed both in mouse tumor allografts and in human pancreatic cancer tissues. In contrast, cisplatin shows synergistic activity with PD-1 antibody by activation of CD8⁺ T cells through the DNA damage-mediated cGAS-STING sensing mechanism, leading to increase of T cell infiltration and secretion of antitumor cytokines. Clinical data show that a combination of cisplatin with PD-1 antibody toripalimab could be effective in advanced lung cancer patients with K-ras mutation who failed prior therapies.

Conclusions

Our study shows that a key factor in selecting chemotherapeutic agents for immunochemotherapy is the drug’s impact on T cell functions, and that cisplatin-based chemotherapy is an excellent choice for combination with immune checkpoint antibody to achieve favorable clinical outcome.

PD-L1 (Programmed Death Ligand 1) Regulates T-Cell Differentiation to Control Adaptive Venous Remodeling

OBJECTIVE

Patients with end-stage renal disease depend on hemodialysis for survival. Although arteriovenous fistulae (AVF) are the preferred vascular access for hemodialysis, the primary success rate of AVF is only 30% to 50% within 6 months, showing an urgent need for improvement. PD-L1 (programmed death ligand 1) is a ligand that regulates T-cell activity. Since T cells have an important role during AVF maturation, we hypothesized that PD-L1 regulates T cells to control venous remodeling that occurs during AVF maturation. Approach and results: In the mouse aortocaval fistula model, anti-PD-L1 antibody (200 mg, 3×/wk intraperitoneal) was given to inhibit PD-L1 activity during AVF maturation. Inhibition of PD-L1 increased T-helper type 1 cells and T-helper type 2 cells but reduced regulatory T cells to increase M1-type macrophages and reduce M2-type macrophages; these changes were associated with reduced vascular wall thickening and reduced AVF patency. Inhibition of PD-L1 also inhibited smooth muscle cell proliferation and increased endothelial dysfunction. The effects of anti-PD-L1 antibody on adaptive venous remodeling were diminished in nude mice; however, they were restored after T-cell transfer into nude mice, indicating the effects of anti-PD-L1 antibody on venous remodeling were dependent on T cells.

CONCLUSIONS

Regulation of PD-L1 activity may be a potential therapeutic target for clinical translation to improve AVF maturation.

Increased soluble programed cell death-ligand 1 is associated with acute coronary syndrome

BACKGROUND

Programmed cell death (PD)-1 and its ligand (PD-L1) plays crucial roles in T-cell tolerance as immune checkpoint. Previous studies reported that increased serum levels of soluble PD-L1 (sPD-L1) reflect myocardial and vascular inflammation. However, little is known about the clinical relationship between sPD-L1 and acute coronary syndrome (ACS). We investigated the relation of sPD-L1 and ACS.

METHODS

We prospectively measured serum levels of sPD-L1 using a commercially available enzyme-linked immunosorbent assay kit in patients with coronary artery disease (CAD) and continuous non-CAD admitted to Kumamoto University Hospital between December 2017 and June 2019. All malignant diseases, patients who underwent hemodialysis, active collagen diseases, and severe infectious diseases were excluded.

RESULTS

Totally, 446 CAD patients [ACS, n = 124; chronic coronary syndrome (CCS), n = 322] and 24 non-CAD patients were analyzed. The levels of sPD-L1 were significantly higher in patients with ACS than those both with non-CAD and CCS {ACS, 188.7 (111.0-260.8) pg/mL, p < 0.001 vs. non-CAD [83.5 (70.8-130.4) pg/mL]; and p = 0.009 vs. CCS [144.2 (94.8-215.5) pg/mL], respectively}. Univariate logistic regression analysis identified that sPD-L1 was significantly associated with ACS [odds ratio (OR): 1.459, 95% confidence interval (CI): 1.198-1.778, p < 0.001]. Multivariable logistic regression analysis with nine significant factors identified from the univariate analysis revealed that sPD-L1 was significantly and independently associated with ACS (OR: 1.561, 95% CI: 1.215-2.006, p < 0.001).

CONCLUSIONS

This is the first clinical study to demonstrate the increased level of sPD-L1 in patients with CAD, and the significant association with ACS.

Programmed Cell Death Ligand 1 Is Enriched in Mammary Stem Cells and Promotes Mammary Development and Regeneration

Programmed cell death ligand 1 (PD-L1) is widely expressed in a variety of human tumors, and inhibition of the PD-L1/PD-1 pathway represents one of the most promising therapy for many types of cancer. However, the physiological function of PD-L1 in tissue development is still unclear, although PD-L1 mRNA is abundant in many tissues. To address this puzzle, we investigated the function of PD-L1 in mammary gland development. Interestingly, we found that PD-L1 is enriched in protein C receptor (Procr)-expressing mammary stem cells (MaSCs), and PD-L1-expressing mammary basal cells (PD-L1⁺ basal cells) exhibit robust mammary regeneration capacity in transplantation assay. The lineage tracing experiment showed that PD-L1⁺ cells can differentiate into all lineages of mammary epithelium cells, suggesting that PD-L1⁺ basal cells have the activities of MaSCs. Furthermore, PD-L1 deficiency significantly impairs mammary development and reduces mammary regeneration capacity of mammary basal cells, suggesting that PD-L1 is not only enriched in MaSCs but also improves activities of MaSCs. In summary, these results demonstrated that PD-L1 is enriched in MaSCs and promotes mammary gland development and regeneration. Mechanistically, our data indicated that PD-L1 expression is induced by continuous activation of Wnt/ß-catenin signaling. In conclusion, these results demonstrated that PD-L1 is a marker of MaSCs, and PD-L1 is essential for mammary development. Our study provides novel insight into the physiological functions of PD-L1 in tissue development.

Conjugation of glucosylated polymer chains to checkpoint blockade antibodies augments their efficacy and specificity for glioblastoma

Because of the blood-tumour barrier and cross-reactivity with healthy tissues, immune checkpoint blockade therapy against glioblastoma has inadequate efficacy and is associated with a high risk of immune-related adverse events. Here we show that anti-programmed death-ligand 1 antibodies conjugated with multiple poly(ethylene glycol) (PEG) chains functionalized to target glucose transporter 1 (which is overexpressed in brain capillaries) and detaching in the reductive tumour microenvironment augment the potency and safety of checkpoint blockade therapy against glioblastoma. In mice bearing orthotopic glioblastoma tumours, a single dose of glucosylated and multi-PEGylated antibodies reinvigorated antitumour immune responses, induced immunological memory that protected the animals against rechallenge with tumour cells, and suppressed autoimmune responses in the animals' healthy tissues. Drug-delivery formulations leveraging multivalent ligand interactions and the properties of the tumour microenvironment to facilitate the crossing of blood-tumour barriers and increase drug specificity may enhance the efficacy and safety of other antibody-based therapies.

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

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

Improved Immunotherapy Efficacy by Vascular Modulation

Several strategies have been developed to modulate the tumour vasculature for cancer therapy including anti-angiogenesis and vascular normalisation. Vasculature modulation results in changes to the tumour microenvironment including oxygenation and immune cell infiltration, therefore lending itself to combination with cancer therapy. The development of immunotherapies has led to significant improvements in cancer treatment. Particularly promising are immune checkpoint blockade and CAR T cell therapies, which use antibodies against negative regulators of T cell activation and T cells reprogrammed to better target tumour antigens, respectively. However, while immunotherapy is successful in some patients, including those with advanced or metastatic cancers, only a subset of patients respond. Therefore, better predictors of patient response and methods to overcome resistance warrant investigation. Poor, or periphery-limited, T cell infiltration in the tumour is associated with poor responses to immunotherapy. Given that (1) lymphocyte recruitment requires leucocyte-endothelial cell adhesion and (2) the vasculature controls tumour oxygenation and plays a pivotal role in T cell infiltration and activation, vessel targeting strategies including anti-angiogenesis and vascular normalisation in combination with immunotherapy are providing possible new strategies to enhance therapy. Here, we review the progress of vessel modulation in enhancing immunotherapy efficacy.

Immune Checkpoints Expression in Chronic Lung Allograft Rejection

Chronic lung allograft dysfunction (CLAD) is the main cause of poor survival and low quality of life of lung transplanted patients. Several studies have addressed the role of dendritic cells, macrophages, T cells, donor specific as well as anti-HLA antibodies, and interleukins in CLAD, but the expression and function of immune checkpoint molecules has not yet been analyzed, especially in the two CLAD subtypes: BOS (bronchiolitis obliterans syndrome) and RAS (restrictive allograft syndrome). To shed light on this topic, we conducted an observational study on eight consecutive grafts explanted from patients who received lung re-transplantation for CLAD. The expression of a panel of immune molecules (PD1/CD279, PDL1/CD274, CTLA4/CD152, CD4, CD8, hFoxp3, TIGIT, TOX, B-Cell-Specific Activator Protein) was analyzed by immunohistochemistry in these grafts and in six control lungs. Results showed that RAS compared to BOS grafts were characterized by 1) the inversion of the CD4/CD8 ratio; 2) a higher percentage of T lymphocytes expressing the PD-1, PD-L1, and CTLA4 checkpoint molecules; and 3) a significant reduction of exhausted PD-1-expressing T lymphocytes (PD-1^pos/TOX^pos) and of exhausted Treg (PD-1^pos/FOXP3^pos) T lymphocytes. Results herein, although being based on a limited number of cases, suggest a role for checkpoint molecules in the development of graft rejection and offer a possible immunological explanation for the worst prognosis of RAS. Our data, which will need to be validated in ampler cohorts of patients, raise the possibility that the evaluation of immune checkpoints during follow-up offers a prognostic advantage in monitoring the onset of rejection, and suggest that the use of compounds that modulate the function of checkpoint molecules could be evaluated in the management of chronic rejection in LTx patients.

The Role of Oncogenes and Redox Signaling in the Regulation of PD-L1 in Cancer

Tumor cells can evade the immune system via multiple mechanisms, including the dysregulation of the immune checkpoint signaling. These signaling molecules are important factors that can either stimulate or inhibit tumor immune response. Under normal physiological conditions, the interaction between programmed cell death ligand 1 (PD-L1) and its receptor, programmed cell death 1 (PD-1), negatively regulates T cell function. In cancer cells, high expression of PD-L1 plays a key role in cancer evasion of the immune surveillance and seems to be correlated with clinical response to immunotherapy. As such, it is important to understand various mechanisms by which PD-L1 is regulated. In this review article, we provide an up-to-date review of the different mechanisms that regulate PD-L1 expression in cancer. We will focus on the roles of oncogenic signals (c-Myc, EML4-ALK, K-ras and p53 mutants), growth factor receptors (EGFR and FGFR), and redox signaling in the regulation of PD-L1 expression and discuss their clinical relevance and therapeutic implications. These oncogenic signalings have common and distinct regulatory mechanisms and can also cooperatively control tumor PD-L1 expression. Finally, strategies to target PD-L1 expression in tumor microenvironment including combination therapies will be also discussed.

Tumor-associated macrophages (TAMs)-derived osteopontin (OPN) upregulates PD-L1 expression and predicts poor prognosis in non-small cell lung cancer (NSCLC)

Background

Programmed cell death ligand 1 (PD‐L1) is widely known as an immune checkpoint molecule in tumor cells. Osteopontin (OPN) is expressed by both tumor cells and tumor‐associated macrophages (TAMs), and both autocrine and paracrine of OPN are considered to be involved in tumor metastasis, proliferation and immunosuppression. However, little is known about the relationship between OPN expressed in TAMs (TOPN) and PD‐L1 in non‐small cell lung cancer (NSCLC).

Methods

Tissue microarray was used to detect the expression of TOPN, TAMs and PD‐L1 by multiple quantitative fluorescence staining in 509 NSCLC patients undergoing complete pulmonary resection. The correlations between TOPN, PD‐L1 and clinicopathological data were analyzed. An in vitro coculture system was established to investigate the crosstalk between TOPN and neoplastic PD‐L1. In vivo, the intrinsic features of PD‐L1 in NSCLC xenografts were evaluated after being coinjected with OPN‐positive TAMs, and a series of key cytokines and chemokines were detected in the tumor microenvironment.

Results

A positive association between the TOPN and PD‐L1 expression in tumor tissues from 509 patients with NSCLC was verified. In addition, TOPN and PD‐L1 were independent prognostic factors for overall survival (OS) and disease‐free survival (DFS) of NSCLC patients. Moreover, TOPN upregulated PD‐L1 expression in NSCLC cells through the nuclear factor‐κB (NF‐κB) pathway in vitro TOPN induced the PD‐L1 expression promoted the tumor growth in tumor‐bearing mice, altering immune‐related cytokines and chemokines.

Conclusions

TOPN regulates PD‐L1 expression through the NF‐κB pathway in NSCLS, which is a potential independent biomarker and target for prognosis as well as immunotherapy.

Clinical course of liver injury induced by immune checkpoint inhibitors in patients with advanced malignancies

BACKGROUND

The clinical course of liver injury induced by immune checkpoint inhibitors (ICIs) varies among individuals, and there were few reports on the therapeutic effects of corticosteroids based on the patterns of liver injury.

METHODS

We evaluated the characteristics and clinical course of immune-related liver injury in 1214 patients treated with ICIs for advanced malignancies except for hepatocellular carcinoma between August 2014 and May 2021.

RESULTS

During the follow-up period (median, 252 days), 58 patients (4.8%) had an immune-related liver injury (≥ Grade 3). The liver-injury patterns were hepatocellular (n = 26, 44.8%), mixed (n = 11, 19.0%), or cholestatic (n = 21, 36.2%), and the median time to onset of liver injury was 39, 81, and 53 days, respectively; the hepatocellular pattern occurred earlier than the other types (p = 0.047). Corticosteroids were administered to 30 (51.7%) patients; while liver injury was improved in almost all patients with the hepatocellular pattern (n = 13/14, 92.9%), that failed to show improvement in over half of the patients with the non-hepatocellular patterns, and three patients with mixed patterns needed secondary immunosuppression with mycophenolate mofetil. Liver biopsies performed in 13 patients mainly showed lobular injury, endothelialitis, and spotty necrosis with infiltration of T cells positive for CD3 and CD8, but not CD4 or CD20.

CONCLUSION

The incidence pattern and therapeutic response to corticosteroids in immune-related liver injury differ according to the injury type. Although corticosteroids were effective for the hepatocellular pattern, an additional strategy for refractory non-hepatocellular patterns is needed.

Anti-angiogenic agents - overcoming tumour endothelial cell anergy and improving immunotherapy outcomes

Immune checkpoint inhibitors have revolutionized medical oncology, although currently only a subset of patients has a response to such treatment. A compelling body of evidence indicates that anti-angiogenic therapy has the capacity to ameliorate antitumour immunity owing to the inhibition of various immunosuppressive features of angiogenesis. Hence, combinations of anti-angiogenic agents and immunotherapy are currently being tested in >90 clinical trials and 5 such combinations have been approved by the FDA in the past few years. In this Perspective, we describe how the angiogenesis-induced endothelial immune cell barrier hampers antitumour immunity and the role of endothelial cell anergy as the vascular counterpart of immune checkpoints. We review the antitumour immunity-promoting effects of anti-angiogenic agents and provide an update on the current clinical successes achieved when these agents are combined with immune checkpoint inhibitors. Finally, we propose that anti-angiogenic agents are immunotherapies - and vice versa - and discuss future research priorities.

Exploring the Pathogenic Role and Therapeutic Implications of Interleukin 2 in Autoimmune Hepatitis

Interleukin 2 is essential for the expansion of regulatory T cells, and low-dose recombinant interleukin 2 has improved the clinical manifestations of diverse autoimmune diseases in preliminary studies. The goals of this review are to describe the actions of interleukin 2 and its receptor, present preliminary experiences with low-dose interleukin 2 in the treatment of diverse autoimmune diseases, and evaluate its potential as a therapeutic intervention in autoimmune hepatitis. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Interleukin 2 is critical for the thymic selection, peripheral expansion, induction, and survival of regulatory T cells, and it is also a growth factor for activated T cells and natural killer cells. Interleukin 2 activates the signal transducer and activator of transcription 5 after binding with its trimeric receptor on regulatory T cells. Immune suppressor activity is increased; anti-inflammatory interleukin 10 is released; pro-inflammatory interferon-gamma is inhibited; and activation-induced apoptosis of CD8⁺ T cells is upregulated. Preliminary experiences with cyclic injections of low-dose recombinant interleukin 2 in diverse autoimmune diseases have demonstrated increased numbers of circulating regulatory T cells, preserved regulatory function, improved clinical manifestations, and excellent tolerance. Similar improvements have been recognized in one of two patients with refractory autoimmune hepatitis. In conclusion, interferon 2 has biological actions that favor the immune suppressor functions of regulatory T cells, and low-dose regimens in preliminary studies encourage its rigorous investigation in autoimmune hepatitis.

Differential Involvement of Programmed Cell Death Ligands in Skin Immune Responses

PD-1 is an immunoregulatory receptor that can bind PD-L1 or PD-L2 expressed on stimulated antigen-presenting cells. In this study, isolated antigen-presenting cells (macrophages and dendritic cells) were cultured with IFN-γ, IL-4, or IL-17A, and the expression of PD-L1 and PD-L2 was compared by flow cytometry. Strong upregulation of PD-L1 expression was observed on IFN-γ stimulation of both antigen-presenting cells as well as in response to IL-17A stimulation of macrophages compared with the expression in unstimulated controls. In contrast, only stimulation with IL-4 could upregulate PD-L2 expression on both antigen-presenting cells. Therefore, experiments were performed in murine models, including DNFB-induced contact hypersensitivity, calcipotriol-induced atopic dermatitis-like skin inflammation, and imiquimod-induced psoriasis-like dermatitis models, to trigger IFN-γ‒mediated T helper type (Th)1-, IL-4‒mediated Th2-, and IL-17A‒mediated Th17-type responses, respectively. In both Th1- and Th17-type immunity models, changes in ear thickness were more severe in Pd-l1‒deficient mice than in wild-type or Pd-l2‒deficient mice. In the Th2-type immunity model, changes in thickness in Pd-l2‒deficient mice were more severe than that in wild-type or Pd-l1‒deficient mice. Collectively, PD-L1 has predominant roles in Th1 and Th17 type immunity, whereas PD-L2 is involved in Th2-type immunity.

Single-Cell Transcriptome Analysis Reveals the M2 Macrophages and Exhausted T Cells and Intratumoral Heterogeneity in Triple-Negative Breast Cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a highly heterogeneous and invasive malignancy that is characterized by high recurrence and mortality rates as well as extremely poor prognosis.

OBJECTIVE

This study aimed to analyze T cells and macrophages in the tumor microenvironment with the aim of identifying targets with therapeutic potential.

METHOD

Single-cell sequencing data of TNBC patients from the GSE118389 dataset were analyzed to examine the immune environment and intratumoral heterogeneity of TNBC patients.

RESULT

Polarized alternatively activated macrophages (M2) and exhausted CD8+ T cells were identified in TNBC patients. Immunosuppressive checkpoint analysis revealed that levels of lymphocyte-activation gene 3 (LAG3) and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) of exhausted T cells were significantly higher than levels of programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). This indicates that these markers are potential immunotherapy targets. Furthermore, analysis of significantly altered immune cell markers showed that several markers are associated with the prognosis of TNBC.

CONCLUSION

Overall, these findings demonstrate inter-tissue heterogeneity of TNBC and provide novel therapeutic targets for the treatment of TNBC.

Aspects of the Tumor Microenvironment Involved in Immune Resistance and Drug Resistance

The tumor microenvironment (TME) is a complex and ever-changing "rogue organ" composed of its own blood supply, lymphatic and nervous systems, stroma, immune cells and extracellular matrix (ECM). These complex components, utilizing both benign and malignant cells, nurture the harsh, immunosuppressive and nutrient-deficient environment necessary for tumor cell growth, proliferation and phenotypic flexibility and variation. An important aspect of the TME is cellular crosstalk and cell-to-ECM communication. This interaction induces the release of soluble factors responsible for immune evasion and ECM remodeling, which further contribute to therapy resistance. Other aspects are the presence of exosomes contributed by both malignant and benign cells, circulating deregulated microRNAs and TME-specific metabolic patterns which further potentiate the progression and/or resistance to therapy. In addition to biochemical signaling, specific TME characteristics such as the hypoxic environment, metabolic derangements, and abnormal mechanical forces have been implicated in the development of treatment resistance. In this review, we will provide an overview of tumor microenvironmental composition, structure, and features that influence immune suppression and contribute to treatment resistance.

Increased PD-L1 Expression in Human Skin Acutely and Chronically Exposed to UV Irradiation

Overexpression of PD-L1 (CD274) on tumor cells may represent a hallmark of immune evasion, and overexpression has been documented in several tumors including cutaneous squamous cell carcinoma (cSCC). While PD-L1/PD-1 activity in the skin has been primarily described in inflammatory models, our goal was to examine PD-L1 expression in human keratinocytes exposed to UV irradiation. We assessed PD-L1 expression in human sun-protected (SP) and sun-damaged (SD) skin, actinic keratosis (AK), and cSCC using IHC and protein microarray. Both methods found low baseline levels of PD-L1 in SP and SD skin and significantly increased expression in cSCC. Next, we examined PD-L1 expression in acute models of UV exposure. In human SP skin exposed to 2-3 MED of UV (n = 20), epidermal PD-L1 was induced in 70% of subjects after 24 h (P = 0.0001). SKH-1 mice exposed to acute UV also showed significant epidermal PD-L1 induction at 16, 24 and 48 h. A time- and dose-dependent induction of PD-L1 was confirmed in cultured human keratinocytes after UV, which was markedly reduced in the presence of MEK/ERK, JNK or STAT3 inhibitors. These findings suggest that UV induces upregulation of PD-L1 through established, pharmacologically targetable stress-signaling pathways in keratinocytes.

Translational Research in Vitiligo

Vitiligo is a disease of the skin characterized by the appearance of white spots. Significant progress has been made in understanding vitiligo pathogenesis over the past 30 years, but only through perseverance, collaboration, and open-minded discussion. Early hypotheses considered roles for innervation, microvascular anomalies, oxidative stress, defects in melanocyte adhesion, autoimmunity, somatic mosaicism, and genetics. Because theories about pathogenesis drive experimental design, focus, and even therapeutic approach, it is important to consider their impact on our current understanding about vitiligo. Animal models allow researchers to perform mechanistic studies, and the development of improved patient sample collection methods provides a platform for translational studies in vitiligo that can also be applied to understand other autoimmune diseases that are more difficult to study in human samples. Here we discuss the history of vitiligo translational research, recent advances, and their implications for new treatment approaches.

The Updated Status and Future Direction of Immunotherapy Targeting B7-H1/PD-1 in Osteosarcoma

Although the mortality rate of osteosarcoma (OS) patients has improved, there are still many unsolved problems concerning how to reduce recurrence and metastasis. In the tumor microenvironment, immune escape plays a more important role in tumor progression and development. Many costimulatory molecules of the B7 family have been reported to be involved in regulating immunological interactions between OS cells and immune cells. Among these molecules, B7-H1 and its receptor, programmed death-1 (PD-1), have been the focus of the fields of tumor immunology and have been recently applied in clinical trials of therapies for several solid tumors. These therapies, referred to as B7-H1/PD-1 checkpoint blockade therapies, are designed to block the interaction between the two molecules. Although the mechanism has been reported in some malignancies, the specific impact of B7-H1/PD-1 expression on OS has not been well defined. Here, we review the expression, function, and regulatory mechanism of the B7-H1/PD-1 axis in OS and introduce and compare the advantages and disadvantages of B7-H1/PD-1 immunotherapies in OS.

Regulatory T Cells in the Tumor Microenvironment

Regulatory T cells (T_regs) are an immunosuppressive subpopulation of CD4⁺ T cells that are endowed with potent suppressive activity and function to limit immune activation and maintain homeostasis. These cells are identified by the hallmark transcription factor FOXP3 and the high-affinity interleukin-2 (IL-2) receptor chain CD25. T_regs can be recruited to and persist within the tumor microenvironment (TME), acting as a potent barrier to effective antitumor immunity. This chapter will discuss [i] the history and hallmarks of T_regs; [ii] the recruitment, development, and persistence of T_regs within the TME; [iii] T_reg function within TME; asnd [iv] the therapeutic targeting of T_regs in the clinic. This chapter will conclude with a discussion of likely trends and future directions.

The clinicopathological significance and prognostic value of programmed death-ligand 1 in prostate cancer: a meta-analysis of 3133 patients

Background: Programmed death-ligand 1 (PD-L1) is considered an adverse factor predicting poor prognosis in various cancers, but the significance of PD-L1 expression for the prognosis of prostate cancer (PCa) is still unclear. We aimed to investigate the clinicopathological significance and prognostic value of PD-L1 expression in PCa.

Methods: Studies were retrieved from PubMed, Web of Science, Cochrane Library and Embase before March 23, 2020. Odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs) were obtained to assess the results. Begg’s test was applied to evaluate publication bias.

Results: Fourteen studies involving 3133 cases were analyzed. The pooled data showed that both PD-L1 protein expression and PD-L1 DNA methylation (mPD-L1) were negatively associated with biochemical recurrence-free survival, with HRs of 1.67 (95% CI = 1.38-2.06, p < 0.001) and 2.23 (95% CI = 1.51-3.29, p < 0.001), respectively. In addition, PD-L1 overexpression was significantly related to advanced tumor stage (OR = 1.40, 95% CI= 1.13-1.75, p = 0.003), positive surgical margin (OR = 1.36, 95% CI = 1.03-1.78, p = 0.028), higher Gleason score (OR = 1.81, 95% CI = 1.35-2.42, p < 0.001) and androgen receptor positivity (OR = 2.20, 95% CI = 1.61-3.01, p < 0.001), while no significant correlation with age (p = 0.122), preoperative PSA (p = 0.796) or nodal status (p = 0.113) was observed.

Conclusions: The study revealed that high expression of PD-L1 was related to unfavorable prognosis and advanced clinicopathological factors in PCa patients.

Angiogenesis in Lymph Nodes Is a Critical Regulator of Immune Response and Lymphoma Growth

Tumor-induced remodeling of the microenvironment in lymph nodes (LNs) includes the formation of blood vessels, which goes beyond the regulation of metabolism, and shaping a survival niche for tumor cells. In contrast to solid tumors, which primarily rely on neo-angiogenesis, hematopoietic malignancies usually grow within pre-vascularized autochthonous niches in secondary lymphatic organs or the bone marrow. The mechanisms of vascular remodeling in expanding LNs during infection-induced responses have been studied in more detail; in contrast, insights into the conditions of lymphoma growth and lodging remain enigmatic. Based on previous murine studies and clinical trials in human, we conclude that there is not a universal LN-specific angiogenic program applicable. Instead, signaling pathways that are tightly connected to autochthonous and infiltrating cell types contribute variably to LN vascular expansion. Inflammation related angiogenesis within LNs relies on dendritic cell derived pro-inflammatory cytokines stimulating vascular endothelial growth factor-A (VEGF-A) expression in fibroblastic reticular cells, which in turn triggers vessel growth. In high-grade B cell lymphoma, angiogenesis correlates with poor prognosis. Lymphoma cells immigrate and grow in LNs and provide pro-angiogenic growth factors themselves. In contrast to infectious stimuli that impact on LN vasculature, they do not trigger the typical inflammatory and hypoxia-related stroma-remodeling cascade. Blood vessels in LNs are unique in selective recruitment of lymphocytes via high endothelial venules (HEVs). The dissemination routes of neoplastic lymphocytes are usually disease stage dependent. Early seeding via the blood stream requires the expression of the homeostatic chemokine receptor CCR7 and of L-selectin, both cooperate to facilitate transmigration of tumor and also of protective tumor-reactive lymphocytes via HEV structures. In this view, the HEV route is not only relevant for lymphoma cell homing, but also for a continuous immunosurveillance. We envision that HEV functional and structural alterations during lymphomagenesis are not only key to vascular remodeling, but also impact on tumor cell accessibility when targeted by T cell-mediated immunotherapies.

PD-L1 chimeric costimulatory receptor improves the efficacy of CAR-T cells for PD-L1-positive solid tumors and reduces toxicity in vivo

BACKGROUND

On-target off-tumor toxicity impedes the clinical application of chimeric antigen receptor-modified T cells (CAR-T cells) in the treatment of solid tumors. Previous reports proved that the combinatorial antigen recognition strategy could improve the safety profile of CAR-T cells by targeting two different tumor-associated antigens (TAAs), one as a CAR-T targeted antigen and the other as a chimeric costimulatory receptor (CCR) ligand. The programmed death-ligand 1 (PD-L1, also known as B7-H1) is preferentially overexpressed on multiple tumors, it will be highly interesting to explore the potential of PD-L1 as a universal target for designing CCR.

METHODS

A novel dual-targeted CAR, which is composed of first-generation CD19/HER2 CAR with CD3ζ signaling domain and PD-L1 CCR containing the CD28 costimulatory domain, was constructed and delivered into T cells by pseudotyped lentivirus. The cytokine release, cytotoxicity and proliferation of dual-targeted CAR-T cells were tested in vitro, and their safety and therapeutic efficacy were evaluated using a human tumor xenograft mouse model in vivo.

RESULTS

The dual-targeted CAR-T cells exerted a similar cytotoxic activity against CD19/HER2⁺ tumor cells with or without PD-L1 in vitro, however, enhanced cytokine releases and improved proliferative capacity were only observed in the presence of both CD19/HER2 and PD-L1. Importantly, the dual-targeted CAR-T cells displayed no cytotoxicity against PD-L1⁺ cells alone in the absence of tumor antigen CD19/HER2. In addition, the dual-targeted CAR-T cells preferably destroyed tumor xenografts bearing both CD19/HER2 and PD-L1, but spared only antigen-positive tumor xenografts without PD-L1 in vivo. Furthermore, PD-L1 CCR also improved the antitumor efficacy of the low-affinity HER2 CAR-T cells against PD-L1⁺ tumors expressing high levels of HER2.

CONCLUSION

Our observations demonstrated that PD-L1 could be used as a universal target antigen for designing CCR, and the dual-targeted CAR-T cells equipped with PD-L1 CCR could be used to reduce the risk of on-target off-tumor toxicity while retaining their potent antitumor efficacy in the treatment of PD-L1⁺ solid tumors.

The role of the programmed cell death protein-1/programmed death-ligand 1 pathway, regulatory T cells and T helper 17 cells in tumor immunity: a narrative review

Tumor immunotherapy, especially that involving programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) immunosuppressive checkpoint inhibitors, has become an important part of tumor treatment strategy in the past decade. Blocking PD-1/PD-L1 signaling pathway can reduce the inhibitory effect of PD-1 pathway on T cells, promote the anti-tumor activity of activated T cells, and prolong the remission period of tumor. While PD-1/PD-L1 immunotherapy is effective in the treatment of solid malignant tumors, it also has shortcomings, due to the complexity of the tumor microenvironment (TME). Regulatory T cells (Tregs) and T helper 17 (Th17) cells play an important role in the TME and are closely related to the occurrence and development of tumors. Tregs can inhibit the anti-tumor immune effect, while Th17 cells play a dual role in tumor immunity, which not only promotes tumorigenesis but also promotes anti-tumor immunity. In the occurrence and development of tumor, PD-1/PD-L1 pathway, Tregs and Th17 cells are interrelated. However, the complicated relationship between the PD-1/PD-L1 pathway, Tregs, and Th17 cells has not been fully clarified. Here, we summarize the immunoregulation mechanisms and discuss the crosstalk between the PD-1/PD-L1 pathway, Tregs, and Th17 cells, with the aim of providing novel insights for future cancer treatment.

Delicate Role of PD-L1/PD-1 Axis in Blood Vessel Inflammatory Diseases: Current Insight and Future Significance

Immune checkpoint molecules are the antigen-independent generator of secondary signals that aid in maintaining the homeostasis of the immune system. The programmed death ligand-1 (PD-L1)/PD-1 axis is one among the most extensively studied immune-inhibitory checkpoint molecules, which delivers a negative signal for T cell activation by binding to the PD-1 receptor. The general attributes of PD-L1's immune-suppressive qualities and novel mechanisms on the barrier functions of vascular endothelium to regulate blood vessel-related inflammatory diseases are concisely reviewed. Though targeting the PD-1/PD-L1 axis has received immense recognition-the Nobel Prize in clinical oncology was awarded in the year 2018 for this discovery-the use of therapeutic modulating strategies for the PD-L1/PD-1 pathway in chronic inflammatory blood vessel diseases is still limited to experimental models. However, studies using clinical specimens that support the role of PD-1 and PD-L1 in patients with underlying atherosclerosis are also detailed. Of note, delicate balances in the expression levels of PD-L1 that are needed to preserve T cell immunity and to curtail acute as well as chronic infections in underlying blood vessel diseases are discussed. A significant link exists between altered lipid and glucose metabolism in different cells and the expression of PD-1/PD-L1 molecules, and its possible implications on vascular inflammation are justified. This review summarizes the most recent insights concerning the role of the PD-L1/PD-1 axis in vascular inflammation and, in addition, provides an overview exploring the novel therapeutic approaches and challenges of manipulating these immune checkpoint proteins, PD-1 and PD-L1, for suppressing blood vessel inflammation.

Identification and Utilization of Biomarkers to Predict Response to Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICPI) have revolutionized cancer therapy and provided clinical benefit to thousands of patients. Despite durable responses in many tumor types, the majority of patients either fail to respond at all or develop resistance to the ICPI. Furthermore, ICPI treatment can be accompanied by serious adverse effects. There is an urgent need for identification of patient populations that will benefit from ICPI as single agents and when used in combinations. As ICPI have achieved regulatory approvals, accompanying biomarkers including PD-L1 immunohistochemistry (IHC) and tumor mutational burden (TMB) have also received approvals for some indications. The ICPI pembrolizumab was the first example of a tissue-agnostic FDA approval based on tumor microsatellite instability (MSI)/deficient mismatch repair (dMMR) biomarker status, rather than on tumor histology assessment. Several other ICPI-associated biomarkers are in the exploratory stage, including quantification of tumor-infiltrating lymphocytes (TILs), gene expression profiling (GEP) of an inflamed microenvironment, and neoantigen prediction. TMB and PD-L1 expression can predict a subset of responses, but they fail to predict all responses to checkpoint blockade. While a single biomarker is currently limited in its ability to fully capture the complexity of the tumor-immune microenvironment, a combination of biomarkers is emerging as a method to improve predictive power. Here we review the steadily growing impact of comprehensive genomic profiling (CGP) for development and utilization of predictive biomarkers by simultaneously capturing TMB, MSI, and the status of genomic targets that confer sensitivity or resistance to immunotherapy, as well as detecting inflammation through RNA expression signatures.