Notch signaling regulates PD-1 expression during CD8(+) T-cell activation

Notch signaling and cancer: Insights into chemoresistance, immune evasion, and immunotherapy

The Notch signaling pathway is a fundamental and highly conserved cell-to-cell communication system vital for embryonic development and tissue maintenance. However, its dysregulation has been associated with the initiation, progression, and chemoresistance of various cancers. In this comprehensive review, we will take an in-depth look at the multiple roles of the Notch family in cancer pathogenesis, immune response, and resistance to chemotherapy. We delve into the complicated mechanisms by which Notch signaling promotes tumor growth and development, including its influence on TME remodeling and immune evasion strategies. We will also be discussing recent studies that shed light on the connection between cancer stemness and chemoresistance mediated through the activation of Notch signaling pathways. Elucidation of the interplay between the Notch pathway and major constituents of the TME, including immune cells and cancer-associated fibroblasts, is necessary for the development of targeted therapies against Notch-driven tumors. We further discuss the potential of targeting Notch signaling alone or in combination with standard chemotherapy and immunotherapy as a potent strategy to overcome chemoresistance and improve patient outcomes. We conclude by discussing the challenges and future prospects of using Notch signaling as a therapeutic target in cancer treatment, focusing on how precision medicine and combination approaches are important.

Early Notch signals from fibroblastic reticular cells program effector CD8+ T cell differentiation

A better understanding of the mechanisms regulating CD8+ T cell differentiation is essential to develop new strategies to fight infections and cancer. Using genetic mouse models and blocking antibodies, we uncovered cellular and molecular mechanisms by which Notch signaling favors the efficient generation of effector CD8+ T cells. Fibroblastic reticular cells from secondary lymphoid organs, but not dendritic cells, were the dominant source of Notch signals in T cells via Delta-like1/4 ligands within the first 3 days of immune responses to vaccination or infection. Using transcriptional and epigenetic studies, we identified a unique Notch-driven T cell-specific signature. Early Notch signals were associated with chromatin opening in regions occupied by bZIP transcription factors, specifically BATF, known to be important for CD8+ T cell differentiation. Overall, we show that fibroblastic reticular cell niches control the ultimate molecular and functional fate of CD8+ T cells after vaccination or infection through the delivery of early Notch signals.

Bcor loss promotes Richter transformation of chronic lymphocytic leukemia associated with Notch1 activation in mice

Richter's transformation (RT) is an aggressive lymphoma occurring upon progression from chronic lymphocytic leukemia (CLL). Despite advances in deciphering the RT genetic architecture, the mechanisms driving this disease remain unknown. BCOR disruptive mutations were found in CLL and frequently associated with NOTCH1 aberrations, a common feature in CLL and RT. We engineered mice to knock-out Bcor in B and CLL cells of Eμ-TCL1 mice. Bcor loss resulted in alterations of the B cell compartment and favored CLL transformation into an aggressive lymphoma with reduced survival in Eμ-TCL1 mice. RNA-sequencing demonstrated a molecular signature reminiscent of human RT and implied the involvement of the T cell tumour microenvironment in the disease onset. Bcor deficiency was associated with Notch1 activation in splenic CD19 + CD5+ cells to accelerate Eμ-TCL1 mice lymphoproliferation. Notch1 inhibition progressively reduced circulating CD19+ CD5+ and RT cells infiltrating the spleen of diseased mice with concomitant reduction of PD-1 expressing T cells and improved survival. Our data demonstrated an interplay between the tumour suppressor activity of Bcor and Notch1 in RT pathogenesis with potential for tumour targeting. This model represented a new platform to uncover promising alternatives for this incurable tumour.

IL-18 primes T cells with an antigen-inexperienced memory phenotype for proliferation and differentiation into effector cells through Notch signaling

Recent studies have revealed that a subset of CD8+ T cells exhibit innate features and can be activated by cytokines. However, the precise mechanisms underlying the proliferation and differentiation of these cells remain unclear. Here, we demonstrated that CD44highCD8+ T cells in the mouse spleen express functional interleukin-18 (IL-18) receptors, whereas CD44lowCD8+ T cells do not. In response to IL-18 stimulation, these cells activated various metabolic pathways, upregulated the expression of surface molecules, such as c-Kit (CD117), CD25, and PD-1, and induced progression through the G1/S phase in the cell cycle. IL-18-primed cells, expressing a high-affinity receptor for IL-2, exhibited robust proliferation in response to IL-2 and underwent differentiation into effector cells. The splenic CD44highCD8+ T cells exhibited high expression levels of CD122, CD62L, CCR7, and CXCR3, along with CD5, indicating their potential for migration to the lymph nodes, where they could undergo expansion and terminal differentiation into effector cells. Additionally, in a tumor model, administration of IL-18 increased the accumulation of CD8+ T cells in both the lymph nodes and tumors. It is noteworthy that stimulation of CD44highCD8+ T cells with IL-18 upregulated the Notch-1 receptor and c-Myc. Moreover, inclusion of γ-secretase inhibitors attenuated the effect of IL-18 on both proliferation and interferon-γ production in the cells. These results demonstrate that IL-18 primes CD44highCD122highCXCR3highCD62LhighCD8+ T cells for expansion and differentiation into effector cells in a Notch signaling-dependent manner.

Notch Signaling and PD-1/PD-L1 Interaction in Hepatocellular Carcinoma: Potentialities of Combined Therapies

Immunotherapy has shown significant improvement in the survival of patients with hepatocellular carcinoma (HCC) compared to TKIs as first-line treatment. Unfortunately, approximately 30% of HCC exhibits intrinsic resistance to ICIs, making new therapeutic combinations urgently needed. The dysregulation of the Notch signaling pathway observed in HCC can affect immune cell response, reducing the efficacy of cancer immunotherapy. Here, we provide an overview of how Notch signaling regulates immune responses and present the therapeutic rationale for combining Notch signaling inhibition with ICIs to improve HCC treatment. Moreover, we propose using exosomes as non-invasive tools to assess Notch signaling activation in hepatic cancer cells, enabling accurate stratification of patients who can benefit from combined strategies.

ADAM10 modulates the efficacy of T-cell-mediated therapy in solid tumors

T-cell-mediated therapeutic strategies are the most potent effectors of cancer immunotherapy. However, an essential barrier to this therapy in solid tumors is disrupting the anti-cancer immune response, cancer-immunity cycle, T-cell priming, trafficking and T-cell cytotoxic capacity. Thus, reinforcing the anti-cancer immune response is needed to improve the effectiveness of T-cell-mediated therapy. Tumor-associated protease ADAM10, endothelial cells (ECs) and cytotoxic CD8+ T cells engage in complex communication via adhesion, transmigration and chemotactic mechanisms to facilitate an anti-cancer immune response. The precise impact of ADAM10 on the intricate mechanisms underlying these interactions remains unclear. This paper broadly explores how ADAM10, through different routes, influences the efficacy of T-cell-mediated therapy. ADAM10 cleaves CD8+ T-cell-targeting genes and impacts their expression and specificity. In addition, ADAM10 mediates the interactions of adhesion molecules with T cells and influences CD8+ T-cell activity and trafficking. Thus, understanding the role of ADAM10 in these events may lead to innovative strategies for advancing T-cell-mediated therapies.

Oncogenic GALNT5 confers FOLFIRINOX resistance via activating the MYH9/ NOTCH/ DDR axis in pancreatic ductal adenocarcinoma

Chemotherapy resistance has been a great challenge in pancreatic ductal adenocarcinoma(PDAC) treatments. Current first-line chemotherapy regimens for PDAC include gemcitabine-based regimens such as AG regimen (albumin paclitaxel and gemcitabine), fluorouracil-based regiments such as FOLFIRINOX regimen ((5-fluorouracil5-FU), oxaliplatin, Irinotecan) and platinum-based regimens for patients with BRCA mutations. large amounts of work have been done on exploring the mechanism underlying resistance of gemcitabine-based and platinum-based regimens, while little research has been achieved on the mechanism of FOLFIRINOX regimens resistance. Hence, we identified Polypeptide N-Acetylgalactosaminyltransferase 5, (GALNT5) as a vital regulator and a potential therapeutic target in FOLFIRINOX regimens resistance. Colony formation assays and flow cytometry assays were performed to explore the roles of GALNT5 in cell proliferation and apoptosis in PDAC treated with FOLFIRINOX. IC50 alterations were calculated in GALNT5 knockdown and overexpressed cell lines. RNA-seq followed by GSEA (gene set enrichment analysis) was displayed to explore the potential mechanism. WB (western blotting), real-time PCR, and IF (immunofluorescence) were performed to validate relative pathways. The mouse orthotopic xenograft PDAC model was established to examine GALNT5 functions in vivo. GALNT5 was highly expressed in PDAC tissues and predicted poor prognosis in PDAC. Upregulation of GALNT5 in PDAC cells conferred FOLFIRINOX resistance on PDAC by inhibiting DNA damage. Moreover, GALNT5 interacted with MYH9, thus participating in the activation of the NOTCH pathways, resulting in hampering FOI-induced DNA damage. Functions of GALNT5 promoting FOLFIRINOX resistance were validated in vivo. In this study, we found that aberrantly overexpressed GALNT5 in PDAC took part in the activation of the NOTCH pathway by interacting with MYH9, thus inhibiting the DDR to achieve FOLFIRINOX resistance and causing poor prognosis. We identified GALNT5 as a potential therapeutic target for PDAC patients resistant to FOLFIRINOX chemotherapy.

Exploring the Role of PD-1 in the Autoimmune Response: Insights into Its Implication in Systemic Lupus Erythematosus

Despite advances in understanding systemic lupus erythematosus (SLE), many challenges remain in unraveling the precise mechanisms behind the disease's development and progression. Recent evidence has questioned the role of programmed cell death protein 1 (PD-1) in suppressing autoreactive CD4+ T cells during autoimmune responses. Research has investigated the potential impacts of PD-1 on various CD4+ T-cell subpopulations, including T follicular helper (Tfh) cells, circulating Tfh (cTfh) cells, and T peripheral helper (Tph) cells, all of which exhibit substantial PD-1 expression and are closely related to several autoimmune disorders, including SLE. This review highlights the complex role of PD-1 in autoimmunity and emphasizes the imperative for further research to elucidate its functions during autoreactive T-cell responses. Additionally, we address the potential of PD-1 and its ligands as possible therapeutic targets in SLE.

Type I Interferon Activates PD-1 Expression through Activation of the STAT1-IRF2 Pathway in Myeloid Cells

PD-1 (Programmed cell death protein 1) regulates the metabolic reprogramming of myeloid-derived suppressor cells and myeloid cell differentiation, as well as the type I interferon (IFN-I) signaling pathway in myeloid cells in the tumor microenvironment. PD-1, therefore, is a key inhibitory receptor in myeloid cells. However, the regulation of PD-1 expression in myeloid cells is unknown. We report that the expression level of PDCD1, the gene that encodes the PD-1 protein, is positively correlated with the levels of IFNB1 and IFNAR1 in myeloid cells in human colorectal cancer. Treatment of mouse myeloid cell lines with recombinant IFNβ protein elevated PD-1 expression in myeloid cells in vitro. Knocking out IFNAR1, the gene that encodes the IFN-I-specific receptor, diminished the inductive effect of IFNβ on PD-1 expression in myeloid cells in vitro. Treatment of tumor-bearing mice with a lipid nanoparticle-encapsulated IFNβ-encoding plasmid (IFNBCOL01) increased IFNβ expression, resulting in elevated PD-1 expression in tumor-infiltrating myeloid cells. At the molecular level, we determined that IFNβ activates STAT1 (signal transducer and activator of transcription 1) and IRFs (interferon regulatory factors) in myeloid cells. Analysis of the cd279 promoter identified IRF2-binding consensus sequence elements. ChIP (chromatin immunoprecipitation) analysis determined that the pSTAT1 directly binds to the irf2 promoter and that IRF2 directly binds to the cd279 promoter in myeloid cells in vitro and in vivo. In colon cancer patients, the expression levels of STAT1, IRF2 and PDCD1 are positively correlated in tumor-infiltrating myeloid cells. Our findings determine that IFNβ activates PD-1 expression at least in part by an autocrine mechanism via the stimulation of the pSTAT1-IRF2 axis in myeloid cells.

Signaling pathways in colorectal cancer implications for the target therapies

Colorectal carcinoma (CRC) stands as a pressing global health issue, marked by the unbridled proliferation of immature cells influenced by multifaceted internal and external factors. Numerous studies have explored the intricate mechanisms of tumorigenesis in CRC, with a primary emphasis on signaling pathways, particularly those associated with growth factors and chemokines. However, the sheer diversity of molecular targets introduces complexity into the selection of targeted therapies, posing a significant challenge in achieving treatment precision. The quest for an effective CRC treatment is further complicated by the absence of pathological insights into the mutations or alterations occurring in tumor cells. This study reveals the transfer of signaling from the cell membrane to the nucleus, unveiling recent advancements in this crucial cellular process. By shedding light on this novel dimension, the research enhances our understanding of the molecular intricacies underlying CRC, providing a potential avenue for breakthroughs in targeted therapeutic strategies. In addition, the study comprehensively outlines the potential immune responses incited by the aberrant activation of signaling pathways, with a specific focus on immune cells, cytokines, and their collective impact on the dynamic landscape of drug development. This research not only contributes significantly to advancing CRC treatment and molecular medicine but also lays the groundwork for future breakthroughs and clinical trials, fostering optimism for improved outcomes and refined approaches in combating colorectal carcinoma.

Psoriasis de novo or exacerbation by PD-1 checkpoint inhibitors

PD-1 (programmed Death-1) immune checkpoint inhibitors have provided significant benefits to tumor patients. However, a considerable proportion of the patients develop immune-related adverse events (irAEs), of which cutaneous irAEs (cirAEs, e.g., psoriasis) occur relatively early. This review provides an overview of the current progress in psoriasis de novo or exacerbation by PD-1 checkpoint inhibitors. It not only describes the relevant influencing factors but also theoretically analyzes the immunological mechanisms that lead to the onset or exacerbation of psoriasis. Finally, the authors present guidelines for the treatment of psoriasis de novo or exacerbation by PD-1 checkpoint inhibitors. The review is intended to assist dermatologists in the early recognition and effective individualized management of such cirAE, which is helpful to continue or adjust the tumor-targeted immunotherapy on the basis of ensuring the quality of life of tumor patients.

Molecular profiling of a bladder cancer with very high tumour mutational burden

The increasing incidence of urothelial bladder cancer is a notable global concern, as evidenced by the epidemiological data in terms of frequency, distribution, as well as mortality rates. Although numerous molecular alterations have been linked to the occurrence and progression of bladder cancer, currently there is a limited knowledge on the molecular signature able of accurately predicting clinical outcomes. In this report, we present a case of a pT3b high-grade infiltrating urothelial carcinoma with areas of squamous differentiation characterized by very high tumor mutational burden (TMB), with up-regulations of immune checkpoints. The high TMB, along with elevated expressions of PD-L1, PD-L2, and PD1, underscores the rationale for developing a personalized immunotherapy focused on the use of immune-checkpoint inhibitors. Additionally, molecular analysis revealed somatic mutations in several other cancer-related genes, including TP53, TP63 and NOTCH3. Mutations of TP53 and TP63 genes provide mechanistic insights on the molecular mechanisms underlying disease development and progression. Notably, the above-mentioned mutations and the elevated hypoxia score make the targeting of p53 and/or hypoxia related pathways a plausible personalized medicine option for this bladder cancer, particularly in combination with immunotherapy. Our data suggest a requirement for molecular profiling in bladder cancer to possibly select appropriate immune-checkpoint therapy.

PD-1 regulation in immune homeostasis and immunotherapy

Harnessing the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis is pivotal in autoimmunity and cancer immunotherapy. PD-1 receptors on immune cells engage with one of its ligands, PD-L1 or PD-L2, expressed on antigen-presenting cells or tumor cells, driving T-cell dysfunction and tumor immune escape. Thus, targeting PD-1/PD-L1 revitalizes cytotoxic T cells for cancer elimination. However, a majority of cancer patients don't respond to PD-1/PD-L1 blockade, and the underlying mechanisms remain partially understood. Recent studies have revealed that PD-1 expression levels or modifications impact the effectiveness of anti-PD-1/PD-L1 treatments. Therefore, understanding the molecular mechanisms governing PD-1 expression and modifications is crucial for innovating therapeutic strategies to enhance the efficacy of PD-1/PD-L1 inhibition. This article presents a comprehensive overview of advancements in PD-1 regulation and highlights their potential in modulating immune homeostasis and cancer immunotherapy, aiming to refine clinical outcomes.

Prognostic value of CD8+T cells related genes and exhaustion regulation of Notch signaling pathway in hepatocellular carcinoma

Immunotherapy has emerged as the primary treatment modality for patients with advanced Hepatocellular carcinoma (HCC). However, its clinical efficacy remains limited, benefiting only a subset of patients, while most exhibit immune tolerance and face a grim prognosis. The infiltration of immune cells plays a pivotal role in tumor initiation and progression. In this study, we conducted an analysis of immune cell infiltration patterns in HCC patients and observed a substantial proportion of CD8+T cells. Leveraging the weighted gene co-expression network analysis (WGCNA), we identified 235 genes associated with CD8+T cell and constructed a risk prediction model. In this model, HCC patients were stratified into a high-risk and low-risk group. Patients in the high-risk group exhibited a lower survival rate, predominantly presented with intermediate to advanced stages of cancer, displayed compromised immune function, showed limited responsiveness to immunotherapy, and demonstrated elevated expression levels of the Notch signaling pathway. Further examination of clinical samples demonstrated an upregulation of the Notch1+CD8+T cell exhaustion phenotype accompanied by impaired cytotoxicity and cytokine secretion functions that worsened with increasing Notch activation levels. Our study not only presents a prognostic model but also highlights the crucial involvement of the Notch pathway in CD8+T cell exhaustion-a potential target for future immunotherapeutic interventions.

Notch signaling genes and CD8+ T-cell dynamics: Their contribution to immune-checkpoint inhibitor therapy in oral squamous cell carcinoma: A retrospective study

BACKGROUND

Aberrant Notch signaling pathway has been related with the tumorigenesis in head and neck region, involving oral cavity. Here, we report the correlation between mutations in the Notch signaling pathway and CD8+ T-cell infiltration via PD-L1, which lead to enhanced antitumor immunity and may target for immune-checkpoint inhibitors (ICIs) therapy.

METHODS

This retrospective study analyzed the results of immunohistochemical staining for PD-L1 and CD8+ T-cell infiltration in 10 patients and whole-exome sequencing (WES) was conducted on five of these patients to identify frequently mutated genes.

RESULTS

Four of 10 patients were positive for PD-L1 and CD8+ T. By analyzing WES in three of these four patients, we notably identified the mutations of NOTCH1, FBXW7, and noncoding RNA intronic mutation in NOTCH2NLR in two of these three patients. This study may enable better selection of ICI therapy with CD8+ T-cell infiltration via PD-L1 expression for oral squamous cell carcinoma patients with mutations in Notch signaling pathway.

The B7:CD28 family and friends: Unraveling coinhibitory interactions

Immune responses must be tightly regulated to ensure both optimal protective immunity and tolerance. Costimulatory pathways within the B7:CD28 family provide essential signals for optimal T cell activation and clonal expansion. They provide crucial inhibitory signals that maintain immune homeostasis, control resolution of inflammation, regulate host defense, and promote tolerance to prevent autoimmunity. Tumors and chronic pathogens can exploit these pathways to evade eradication by the immune system. Advances in understanding B7:CD28 pathways have ushered in a new era of immunotherapy with effective drugs to treat cancer, autoimmune diseases, infectious diseases, and transplant rejection. Here, we discuss current understanding of the mechanisms underlying the coinhibitory functions of CTLA-4, PD-1, PD-L1:B7-1 and PD-L2:RGMb interactions and less studied B7 family members, including HHLA2, VISTA, BTNL2, and BTN3A1, as well as their overlapping and unique roles in regulating immune responses, and the therapeutic potential of these insights.

Evaluation of Tcell exhaustion based on the expression of EOMES, Tbet and co-inhibitory receptors in severe and non-severe covid-19 patients

During viral infections, especially Covid-19, Tcell exhaustion plays a crucial role in reducing the activity of lymphocytes and the immune system's antiviral activities. This research aimed to investigate the co-inhibitory receptors and transcription factors involved in the Tcell exhaustion process in ICU-admitted (ICUA) compared to non-ICU admitted (non-ICUA) Covid-19 patients. A total of 60 Covid-19 patients (30 patients in the severe group who were admitted in the ICU (ICUA) and 30 patients in the mild group who were admitted in departments other than the ICU (non-ICUA)) and 10 healthy individuals were included in this study. Laboratory tests and the level of gene expressions related to 4 inhibitory co-receptors, including LAG-3, TIM-3, TIGIT, PD-1, and T-bet and Eomes transcription factors involved in the process of Tcell exhaustion in severe and mild patients of Covid-19 were investigated. The results showed lymphopenia and an increase in other hematologic laboratory factors such as NLR, PLR, CRP, ALT, and AST in people with a severe form of the disease (ICUA) compared to mild groups (non-ICUA) (P < 0.001). Furthermore, a significant increase in 3 co-inhibitory receptors, TIM-3, LAG-3, and PD-1, was observed in severe patients compared to mild and healthy people (P < 0.001). An increase in TIGIT gene expression was lesser than the other three mentioned receptors (P < 0.05). Concerning the transcription factors, we observed a significant increase in Eomes in ICUA patients compared to the non-ICUA group (P < 0.001), and this increment in T-bet gene expression was minor compared to Eomes (P < 0.05). In conclusion, Patients with a severe form of acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represented a higher level of gene expressions in terms of co-inhibitory receptors and transcription factors involved in the T cell exhaustion process.

Notch signaling pathway involved in Echinococcus granulosus infection regulates dendritic cell development and differentiation

Introduction

The Notch signaling pathway is involved in the development of many diseases; it regulates the development of dendritic cells (DCs), and affects the immune response of DC-mediated T cells. We previously found that ferritin and malate dehydrogenase (mMDH) in Echinococcus granulosus (E.granulosus) induced different immune responses through sensitized DCs. Therefore, in the study we explored whether the Notch signaling pathway affects the development and differentiation of DCs, causing changes in the immune response of DCs sensitized with E. granulosus antigens, and clarified whether it is involved in E.granulosus infection.

Methods

We used the Notch signaling pathway inhibitor [N-[3,5-difluorophenace-tyl] -L-alanyl]-S-phenylglycinet-butyl ester (DAPT) or activator Jagged1 to construct in vitro cell models with blocked or activated Notch signaling respectively. We analyzed the effect of Notch signaling on the development and differentiation of DCs by detecting their morphology, migration function, capacity to promote T cell proliferation, and cytokine secretion. We observed the changes in DC response to E. granulosus antigens and the mediated immune response.

Results

DAPT inhibited the development and maturation of DCs, which were in a non-responsive or incompetent state, reduced the sensitization of DCs to Eg.ferritin, weakened the migration ability of DCs, disrupted their ability to mediate T-cell proliferation, reduced DC expression of MHCII, CD80, CD60, and CD40 co-stimulatory molecules, prevented the secretion of cytokines and attenuated the expression of Notch1, Notch2, Notch3 receptors, Jagged1, Delta-like 4 (Delta4), and Hes1. Following Jagged1 addition, the function of DCs was restored to some extent, and the expression of Notch1, Delta4 and Hes1 was activated in response to the stimulation of Eg.ferritin. However, Eg.mMDH stimulated DCs to produce an immune response showing weak interference by DAPT and Jagged1.

Discussion

The study suggests that the Notc h signaling pathway is involved in the Eg.ferritin-sensitized DC-mediated immune response, which may become a new target for treating E.granulosus infection.

The Notch signaling pathway: a potential target for cancer immunotherapy

Dysregulation of the Notch signaling pathway, which is highly conserved across species, can drive aberrant epigenetic modification, transcription, and translation. Defective gene regulation caused by dysregulated Notch signaling often affects networks controlling oncogenesis and tumor progression. Meanwhile, Notch signaling can modulate immune cells involved in anti- or pro-tumor responses and tumor immunogenicity. A comprehensive understanding of these processes can help with designing new drugs that target Notch signaling, thereby enhancing the effects of cancer immunotherapy. Here, we provide an up-to-date and comprehensive overview of how Notch signaling intrinsically regulates immune cells and how alterations in Notch signaling in tumor cells or stromal cells extrinsically regulate immune responses in the tumor microenvironment (TME). We also discuss the potential role of Notch signaling in tumor immunity mediated by gut microbiota. Finally, we propose strategies for targeting Notch signaling in cancer immunotherapy. These include oncolytic virotherapy combined with inhibition of Notch signaling, nanoparticles (NPs) loaded with Notch signaling regulators to specifically target tumor-associated macrophages (TAMs) to repolarize their functions and remodel the TME, combining specific and efficient inhibitors or activators of Notch signaling with immune checkpoint blockers (ICBs) for synergistic anti-tumor therapy, and implementing a customized and effective synNotch circuit system to enhance safety of chimeric antigen receptor (CAR) immune cells. Collectively, this review aims to summarize how Notch signaling intrinsically and extrinsically shapes immune responses to improve immunotherapy.

PD-1 signalling defines and protects leukaemic stem cells from T cell receptor-induced cell death in T cell acute lymphoblastic leukaemia

T cell acute lymphoblastic leukaemia (T-ALL) is an aggressive malignancy with poor prognosis, but a decisive marker and effective treatment for leukaemia stem cells (LSCs) remain unclear. Here, using lineage tracing, limiting dilution assays and in vivo live imaging approaches, we identify rare inhibitory receptor programmed cell death 1 (PD-1)-expressing cells that reside at the apex of leukaemia hierarchy for initiation and relapse in T-ALL. Ablation of PD-1-expressing cells, deletion of PD-1 in T-ALL cells or blockade of PD-1 or PD-1 ligand 1 significantly eradicated LSCs and suppressed disease progression. Combination therapy using PD-1 blockade and chemotherapy substantially extended the survival of mice engrafted with mouse or human T-ALL cells. Mechanistically, PD-1⁺ LSCs had high NOTCH1-MYC activity for disease initiation. Furthermore, PD-1 signalling maintained quiescence and protected LSCs against T cell receptor-signal-induced apoptosis. Overall, our data highlight the hierarchy of leukaemia by identifying PD-1⁺ LSCs and provide a therapeutic approach for the elimination of LSCs through PD-1 blockade in T-ALL.

Disruption of CISH promotes the antitumor activity of human T cells and decreases PD-1 expression levels

Tumor cells and the immunosuppressive tumor microenvironment suppress the antitumor activity of T cells through immune checkpoints, including the PD-L1/PD-1 axis. Cytokine-inducible SH2-containing protein (CISH), a member of the suppressor of cytokine signaling (SOCS) family, inhibits JAK-STAT and T cell receptor (TCR) signaling in T and natural killer (NK) cells. However, its role in the regulation of immune checkpoints in T cells remains unclear. In this study, we ablated CISH in T cells with CRISPR-Cas9 and found that the sensitivity of T cells to TCR and cytokine stimulation was increased. In addition, chimeric antigen receptor T cells with CISH deficiency exhibited longer survival and higher cytokine secretion and antitumor activity. Notably, PD-1 expression was decreased in activated CISH-deficient T cells in vitro and in vivo. The level of FBXO38, a ubiquitination-regulating protein that reduces PD-1 expression, was elevated in activated T cells after CISH ablation. Hence, this study reveals a mechanism by which CISH promotes PD-1 expression by suppressing the expression of FBXO38 and proposes a new strategy for augmenting the therapeutic effect of CAR-T cells by inhibiting CISH.

Next-generation immunotherapy for solid tumors: combination immunotherapy with crosstalk blockade of TGFβ and PD-1/PD-L1

INTRODUCTION

In solid tumor immunotherapy, less than 20% of patients respond to anti-programmed cell death 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) agents. The role of transforming growth factor β (TGFβ) in diverse immunity is well-established; however, systemic blockade of TGFβ is associated with toxicity. Accumulating evidence suggests the role of crosstalk between TGFβ and PD-1/PD-L1 pathways.

AREAS COVERED

We focus on TGFβ and PD-1/PD-L1 signaling pathway crosstalk and the determinant role of TGFβ in the resistance of immune checkpoint blockade. We provide the rationale for combination anti-TGFβ and anti-PD-1/PD-L1 therapies for solid tumors and discuss the current status of dual blockade therapy in preclinical and clinical studies.

EXPERT OPINION

The heterogeneity of tumor microenvironment across solid tumors complicates patient selection, treatment regimens, and response and toxicity assessment for investigation of dual blockade agents. However, clinical knowledge from single-agent studies provides infrastructure to translate dual blockade therapies. Dual TGFβ and PD-1/PD-L1 blockade results in enhanced T-cell infiltration into tumors, a primary requisite for successful immunotherapy. A bifunctional fusion protein specifically targets TGFβ in the tumor microenvironment, avoiding systemic toxicity, and prevents interaction of PD-1+ cytotoxic cells with PD-L1+ tumor cells.

Pivotal role of PD-1/PD-L1 immune checkpoints in immune escape and cancer progression: Their interplay with platelets and FOXP3+Tregs related molecules, clinical implications and combinational potential with phytochemicals

Immune checkpoint proteins including programmed cell death protein 1 (PD-1), its ligand PD-L1 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are involved in proliferation, angiogenesis, metastasis, chemoresistance via immune escape and immune tolerance by disturbing cytotoxic T cell activation. Though many clinical trials have been completed in several cancers by using immune checkpoint inhibitors alone or in combination with other agents to date, recently multi-target therapy is considered more attractive than monotherapy, since immune checkpoint proteins work with other components such as surrounding blood vessels, dendritic cells, fibroblasts, macrophages, platelets and extracellular matrix within tumor microenvironment. Thus, in the current review, we look back on research history of immune checkpoint proteins and discuss their associations with platelets or tumor cell induced platelet aggregation (TCIPA) and FOXP3+ regulatory T cells (Tregs) related molecules involved in immune evasion and tumor progression, clinical implications of completed trial results and signaling networks by phytochemicals for combination therapy with immune checkpoint inhibitors and suggest future research perspectives.

Tumor accomplice: T cell exhaustion induced by chronic inflammation

The development and response to treatment of tumor are modulated by inflammation, and chronic inflammation promotes tumor progression and therapy resistance. This article summarizes the dynamic evolution of inflammation from acute to chronic in the process of tumor development, and its effect on T cells from activation to the promotion of exhaustion. We review the mechanisms by which inflammatory cells and inflammatory cytokines regulate T cell exhaustion and methods for targeting chronic inflammation to improve the efficacy of immunotherapy. It is great significance to refer to the specific state of inflammation and T cells at different stages of tumor development for accurate clinical decision-making of immunotherapy and improving the efficiency of tumor immunotherapy.

The role of neoantigens in tumor immunotherapy

Tumor neoantigens are aberrant polypeptides produced by tumor cells as a result of genomic mutations. They are also tumor-specific antigens (TSA). Neoantigens are more immunogenic than tumor-related antigens and do not induce autoimmunity. Based on the rapid development of bioinformatics and the continuous update of sequencing technology, cancer immunotherapy with tumor neoantigens has made promising breakthroughs and progress. In this review, the generation, prediction, and identification of novel antigens, as well as the individualized treatments of neoantigens, were first introduced. Secondly, the mechanism of Chimeric Antigen Receptor T-Cell Immunotherapy (CAR-T) therapy and immune checkpoint blockade therapy in the treatment of tumors were outlined, and the three treatment methods were compared. Thirdly, the application of neoantigens in CAR-T therapy and PD-1/PD-L1 blockade therapy was briefly described. The benefits of the neoantigen vaccines over common vaccines were summarized as well. Finally, the prospect of neoantigen therapy was presented.

The COX-2-PGE2 Pathway Promotes Tumor Evasion in Colorectal Adenomas

The mechanisms underlying the regulation of a checkpoint receptor, PD-1, in tumor-infiltrating immune cells during the development of colorectal cancer are not fully understood. Here we demonstrate that COX-2-derived PGE2, an inflammatory mediator and tumor promoter, induces PD-1 expression by enhancing NFκB's binding to the PD-1 promoter via an EP4-PI3K-Akt signaling pathway in both CD8+ T cells and macrophages. Moreover, PGE2 suppresses CD8+ T-cell proliferation and cytotoxicity against tumor cells and impairs macrophage phagocytosis of cancer cells via an EP4-PI3K-Akt-NFκB-PD-1 signaling pathway. In contrast, inhibiting the COX-2-PGE2-EP4 pathway increases intestinal CD8+ T-cell activation and proliferation and enhances intestinal macrophage phagocytosis of carcinoma cells accompanied by reduction of PD-1 expression in intestinal CD8+ T cells and macrophages in ApcMin/+ mice. PD-1 expression correlates well with COX-2 levels in human colorectal cancer specimens. Both elevated PD-1 and COX-2 are associated with poorer overall survival in patients with colorectal cancer. Our results uncover a novel role of PGE2 in tumor immune evasion. They may provide the rationale for developing new therapeutic approaches to subvert this process by targeting immune checkpoint pathways using EP4 antagonists. In addition, our findings reveal a novel mechanism explaining how NSAIDs reduce colorectal cancer risk by suppressing tumor immune evasion.

PREVENTION RELEVANCE

These findings provide a potential explanation underlying the chemopreventive effect of NSAIDs on reducing colorectal cancer incidence during premalignancy and provide a rationale for developing EP4 antagonists for colorectal cancer prevention and treatment. Simply targeting PGE2 signaling alone may be efficacious in colorectal cancer prevention and treatment, avoiding side effects associated with NSAIDs.

Effects of PD-1 Signaling on Immunometabolic Reprogramming

Programmed Death-1 (PD-1; CD279) is an inhibitory receptor induced in several activated immune cells and, after engagement with its ligands PD-L1 and PD-L2, serves as a key mediator of peripheral tolerance. However, PD-1 signaling also has detrimental effects on T cell function by posing breaks on antitumor and antiviral immunity. PD-1 blocking immunotherapy either alone or in combination with other therapeutic modalities has shown great promise in cancer treatment. However, it is unclear why only a small fraction of patients responds to this type of therapy. For this reason, efforts to better understand the mechanisms of PD-1 function have recently been intensified, with the goal to reveal new strategies to overcome current limitations. The signaling pathways that are inhibited by PD-1 impact key regulators of metabolism. Here, we provide an overview of the current knowledge about the effects of PD-1 on metabolic reprogramming of immune cells and their consequences on systemic metabolism.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

IL-7-Treated Periodontal Ligament Cells Regulate Local Immune Homeostasis by Modulating Treg/Th17 Cell Polarization

Both interleukin (IL)-7 and human periodontal ligament cells (hPDLCs) have immunomodulatory properties. However, their combined effect on CD4⁺T cells has never been studied. In this study, we aimed to investigate the effect of conditioned medium of hPDLCs treated with rhIL-7 on the differentiation of CD4⁺T cells into regulatory T cells/T helper 17 cells (Treg/Th17 cells) and observe the effect of IL-7 on the immunomodulatory properties of PDLCs. After hPDLCs were treated with different concentrations of rhIL-7 for 24 h, the collected supernatants were used to incubate CD4⁺T cells for 3 days. A gamma-secretase inhibitor (DAPT) was used to suppress the activation of the Notch1 signaling pathway. Cell proliferation, apoptosis, and necrosis were determined using the cell counting kit-8 (CCK-8) and flow cytometry (FCM). The expressions of forkhead box P3 (Foxp3) in CD4⁺T cells and transforming growth factor (TGF-β) and IL-6 in the supernatants were determined by ELISA. Reverse transcription-quantitative PCR (RT-qPCR), and the Western blot (WB) determined the mRNA levels and protein expression of various target factors. FCM was used to detect the mean fluorescence intensity of PD-L1 in hPDLCs and to analyze the differentiation of Treg/Th17 cells. Our results showed that IL-7 promoted proliferation and inhibited apoptosis in hPDLCs, promoted the expression of TGF-β, PD-L1, Notch1, Jagged1, and Hes1, and inhibited the levels of hypoxia-inducible factor (HIF)-1α and TCF7, whereas the addition of DAPT effectively reversed these effects. Importantly, we found that the conditioned medium of hPDLCs treated with rhIL-7 promoted the polarization of CD4⁺T cells into Treg cells but had no significant effect on the differentiation of Th17 cells. Our study indicated that treatment of PDLCs with IL-7 can promote the polarization of CD4⁺T cells into Treg cells by modulating the expression of inflammatory factors and signaling molecules through activating the Notch1 signaling pathway, thus participating in the regulation of immune homeostasis in the periodontal microenvironment.

Long Noncoding RNA lncNDEPD1 Regulates PD-1 Expression via miR-3619-5p in CD8+ T Cells

Therapies targeting programmed cell death protein 1 (PD-1) have gained great success in patients with multiple types of cancer. The regulatory mechanisms underlying PD-1 expression have been extensively explored. However, the impact of long noncoding RNAs on PD-1 expression remains elusive. In this study, we identified the Notch1/lncNDEPD1 axis, which plays a critical role in PD-1 expression in human CD8+ T cells. RNA sequencing and quantitative reverse transcription PCR data showed that lncNDEPD1 was upregulated in activated T cells, especially in PD-1high subsets. Fluorescence in situ hybridization demonstrated that lncNDEPD1 was localized in the cytoplasm. A mechanistic study showed that lncNDEPD1 could bind with miR-3619-5p and PDCD1 mRNA to prevent PDCD1 mRNA degradation and then upregulate PD-1 expression. A chromatin immunoprecipitation assay showed that Notch1 directly binds to the promoter of lncNDEPD1 instead of PDCD1 Furthermore, chimeric Ag receptor T cells expressing lncNDEPD1-specific short hairpin RNAs were generated. Chimeric Ag receptor T cells with decreased lncNDEPD1 expression showed enhanced tumoricidal effects when PD-L1 was present. Our work uncovered a new regulatory mechanism of PD-1 expression and thus provided a potential target to decrease PD-1 without affecting T cell function.

In PD-1+ human colon cancer cells NIVOLUMAB promotes survival and could protect tumor cells from conventional therapies

BACKGROUND

Colorectal cancer (CRC) is one of the most prevalent and deadly tumors worldwide. The majority of CRC is resistant to anti-programmed cell death-1 (PD-1)-based cancer immunotherapy, with approximately 15% with high-microsatellite instability, high tumor mutation burden, and intratumoral lymphocytic infiltration. Programmed death-ligand 1 (PD-L1)/PD-1 signaling was described in solid tumor cells. In melanoma, liver, and thyroid cancer cells, intrinsic PD-1 signaling activates oncogenic functions, while in lung cancer cells, it has a tumor suppressor effect. Our work aimed to evaluate the effects of the anti-PD-1 nivolumab (NIVO) on CRC cells.

METHODS

In vitro NIVO-treated human colon cancer cells (HT29, HCT116, and LoVo) were evaluated for cell growth, chemo/radiotherapeutic sensitivity, apoptosis, and spheroid growth. Total RNA-seq was assessed in 6-24 hours NIVO-treated human colon cancer cells HT29 and HCT116 as compared with NIVO-treated PES43 human melanoma cells. In vivo mice carrying HT29 xenograft were intraperitoneally treated with NIVO, OXA (oxaliplatin), and NIVO+OXA, and the tumors were characterized for growth, apoptosis, and pERK1/2/pP38. Forty-eight human primary colon cancers were evaluated for PD-1 expression through immunohistochemistry.

RESULTS

In PD-1+ human colon cancer cells, intrinsic PD-1 signaling significantly decreased proliferation and promoted apoptosis. On the contrary, NIVO promoted proliferation, reduced apoptosis, and protected PD-1+ cells from chemo/radiotherapy. Transcriptional profile of NIVO-treated HT29 and HCT116 human colon cancer cells revealed downregulation of BATF2, DRAM1, FXYD3, IFIT3, MT-TN, and TNFRSF11A, and upregulation of CLK1, DCAF13, DNAJC2, MTHFD1L, PRPF3, PSMD7, and SCFD1; the opposite regulation was described in NIVO-treated human melanoma PES43 cells. Differentially expressed genes (DEGs) were significantly enriched for interferon pathway, innate immune, cytokine-mediated signaling pathways. In vivo, NIVO promoted HT29 tumor growth, thus reducing OXA efficacy as revealed through significant Ki-67 increase, pERK1/2 and pP38 increase, and apoptotic cell reduction. Eleven out of 48 primary human colon cancer biopsies expressed PD-1 (22.9%). PD-1 expression is significantly associated with lower pT stage.

CONCLUSIONS

In PD-1+ human colon cancer cells, NIVO activates tumor survival pathways and could protect tumor cells from conventional therapies.

The foundations of immune checkpoint blockade and the ipilimumab approval decennial

Cancer immunity, and the potential for cancer immunotherapy, have been topics of scientific discussion and experimentation for over a hundred years. Several successful cancer immunotherapies - such as IL-2 and interferon-α (IFNα) - have appeared over the past 30 years. However, it is only in the past decade that immunotherapy has made a broad impact on patient survival in multiple high-incidence cancer indications. The emergence of immunotherapy as a new pillar of cancer treatment (adding to surgery, radiation, chemotherapy and targeted therapies) is due to the success of immune checkpoint blockade (ICB) drugs, the first of which - ipilimumab - was approved in 2011. ICB drugs block receptors and ligands involved in pathways that attenuate T cell activation - such as cytotoxic T lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1) and its ligand, PDL1 - and prevent, or reverse, acquired peripheral tolerance to tumour antigens. In this Review we mark the tenth anniversary of the approval of ipilimumab and discuss the foundational scientific history of ICB, together with the history of the discovery, development and elucidation of the mechanism of action of the first generation of drugs targeting the CTLA4 and PD1 pathways.

Distinct Hypoxia-Related Gene Profiling Characterizes Clinicopathological Features and Immune Status of Mismatch Repair-Deficient Colon Cancer

Despite dramatic responses to immune checkpoint inhibitors (ICIs) in patients with colon cancer (CC) harboring deficient mismatch repair (dMMR), more than half of these patients ultimately progress and experience primary or secondary drug resistance. There is no useful biomarker that is currently validated to accurately predict this resistance or stratify patients who may benefit from ICI-based immunotherapy. As hypoxic and acidic tumor microenvironment would greatly impair tumor-suppressing functions of tumor-infiltrating lymphocytes (TILs), we sought to explore distinct immunological phenotypes by analysis of the intratumoral hypoxia state using a well-established gene signature. Based on the Gene Expression Omnibus (GEO) (n = 88) and The Cancer Genome Atlas (TCGA) (n = 49) databases of patients with CC, we found that dMMR CC patients could be separated into normoxia subgroup (NS) and hypoxia subgroup (HS) with different levels of expression of hypoxia-related genes (lower in NS group and higher in HS group) using NMF package. Tumoral parenchyma in the HS group had a relatively lower level of immune cell infiltration, particularly CD8+ T cells and M1 macrophages than the NS group, and coincided with higher expression of immune checkpoint molecules and C-X-C motif chemokines, which might be associated with ICI resistance and prognosis. Furthermore, three genes, namely, MT1E, MT2A, and MAFF, were identified to be differentially expressed between NS and HS groups in both GEO and TCGA cohorts. Based on these genes, a prognostic model with stable and valuable predicting ability has been built for clinical application. In conclusion, the varying tumor-immune microenvironment (TIME) classified by hypoxia-related genes might be closely associated with different therapeutic responses of ICIs and prognosis of dMMR CC patients.

Differential Role of PD-1 Expressed by Various Immune and Tumor Cells in the Tumor Immune Microenvironment: Expression, Function, Therapeutic Efficacy, and Resistance to Cancer Immunotherapy

In the tumor immune microenvironment (TIME), tumor cells interact with various cells and operate various strategies to avoid antitumor immune responses. These immune escape strategies often make the TIME resistant to cancer immunotherapy. Neutralizing immune escape strategies is necessary to overcome resistance to cancer immunotherapy. Immune checkpoint receptors (ICRs) expressed in effector immune cells inhibit their effector function via direct interaction with immune checkpoint ligands (ICLs) expressed in tumor cells. Therefore, blocking ICRs or ICLs has been developed as a promising cancer immunotherapy by reinvigorating the function of effector immune cells. Among the ICRs, programmed cell death 1 (PD-1) has mainly been antagonized to enhance the survival of human patients with cancer by restoring the function of tumor-infiltrating (TI) CD8⁺ T cells. It has been demonstrated that PD-1 is expressed not only in TI CD8⁺ T cells, but also in other TI immune cells and even tumor cells. While PD-1 suppresses the function of TI CD8⁺ T cells, it is controversial whether PD-1 suppresses or amplifies the suppressive function of TI-suppressive immune cells (e.g., regulatory T cells, tumor-associated macrophages, and myeloid cells). There is also controversy regarding the role of tumor-expressing PD-1. Therefore, a precise understanding of the expression pattern and function of PD-1 in each cell subset is important for improving the efficacy of cancer immunotherapy. Here, we review the differential role of PD-1 expressed by various TI immune cells and tumor cells. We focused on how cell-type-specific ablation or blockade of PD-1 affects tumor growth in a murine tumor model. Furthermore, we will also describe how the blockade of PD-1 acts on TI immune cells in human patients with cancer.

Shooting at Moving and Hidden Targets-Tumour Cell Plasticity and the Notch Signalling Pathway in Head and Neck Squamous Cell Carcinomas

Head and Neck Squamous Cell Carcinoma (HNSCC) is often aggressive, with poor response to current therapies in approximately 40-50% of the patients. Current therapies are restricted to operation and irradiation, often combined with a small number of standard-of-care chemotherapeutic drugs, preferentially for advanced tumour patients. Only very recently, newer targeted therapies have entered the clinics, including Cetuximab, which targets the EGF receptor (EGFR), and several immune checkpoint inhibitors targeting the immune receptor PD-1 and its ligand PD-L1. HNSCC tumour tissues are characterized by a high degree of intra-tumour heterogeneity (ITH), and non-genetic alterations that may affect both non-transformed cells, such as cancer-associated fibroblasts (CAFs), and transformed carcinoma cells. This very high degree of heterogeneity likely contributes to acquired drug resistance, tumour dormancy, relapse, and distant or lymph node metastasis. ITH, in turn, is likely promoted by pronounced tumour cell plasticity, which manifests in highly dynamic and reversible phenomena such as of partial or hybrid forms of epithelial-to-mesenchymal transition (EMT), and enhanced tumour stemness. Stemness and tumour cell plasticity are strongly promoted by Notch signalling, which remains poorly understood especially in HNSCC. Here, we aim to elucidate how Notch signal may act both as a tumour suppressor and proto-oncogenic, probably during different stages of tumour cell initiation and progression. Notch signalling also interacts with numerous other signalling pathways, that may also have a decisive impact on tumour cell plasticity, acquired radio/chemoresistance, and metastatic progression of HNSCC. We outline the current stage of research related to Notch signalling, and how this pathway may be intricately interconnected with other, druggable targets and signalling mechanisms in HNSCC.

Various Uses of PD1/PD-L1 Inhibitor in Oncology: Opportunities and Challenges

The occurrence and development of cancer are closely related to the immune escape of tumor cells and immune tolerance. Unlike previous surgical, chemotherapy, radiotherapy and targeted therapy, tumor immunotherapy is a therapeutic strategy that uses various means to stimulate and enhance the immune function of the body, and ultimately achieves the goal of controlling tumor cells.With the in-depth understanding of tumor immune escape mechanism and tumor microenvironment, and the in-depth study of tumor immunotherapy, immune checkpoint inhibitors represented by Programmed Death 1/Programmed cell Death-Ligand 1(PD-1/PD-L1) inhibitors are becoming increasingly significant in cancer medication treatment. employ a variety of ways to avoid detection by the immune system, a single strategy is not more effective in overcoming tumor immune evasion and metastasis. Combining different immune agents or other drugs can effectively address situations where immunotherapy is not efficacious, thereby increasing the chances of success and alternative access to alternative immunotherapy. Immune combination therapies for cancer have become a hot topic in cancer treatment today. In this paper, several combination therapeutic modalities of PD1/PD-L1 inhibitors are systematically reviewed. Finally, an analysis and outlook are provided in the context of the recent advances in combination therapy with PD1/PD-L1 inhibitors and the pressing issues in this field.

Transcriptional and epigenetic regulation of PD-1 expression

Programmed cell death-1 (PD-1) is a co-inhibitory receptor that plays important roles in regulating T cell immunity and peripheral tolerance. PD-1 signaling prevents T cells from overactivation during acute infections, but it maintains T cell exhaustion during chronic infections. Tumor cells can exploit the PD-1 signaling pathway to evade antitumor immune responses. The PD-1 signaling pathway is also essential for maintaining peripheral tolerance and prevention of autoimmunity. PD-1 expression is strictly and differentially regulated by diverse mechanisms in immune cells. It is activated and repressed by distinct transcription factors in different circumstances. Moreover, epigenetic mechanisms are also involved in regulating PD-1 expression. In this review, we summarize the knowledge of the transcriptional and epigenetic regulation of PD-1 expression during different immune responses.

Progress in research on childhood T-cell acute lymphocytic leukemia, Notch1 signaling pathway, and its inhibitors: A review

Childhood leukemia is cancer that seriously threatens the life of children in China. Poor sensitivity to chemotherapy and susceptibility to drug resistance are the reasons for the treatment of T-cell acute lymphocytic leukemia (T-ALL) being extremely difficult. Moreover, traditional intensive chemotherapy regimens cause great damage to children. Therefore, it is highly important to search for targeted drugs and develop a precise individualized treatment for child patients. There are activating mutations in the NOTCH1 gene in more than 50% of human T-ALLs and the Notch signaling pathway is involved in the pathogenesis of T-ALL. In this review, we summarize the progress in research on T-ALL and Notch1 signaling pathway inhibitors to provide a theoretical basis for the clinical treatment of T-ALL.

The PD-1:PD-L1 axis in Inflammatory Arthritis

The activation of antigen specific T cells during an immune response is a tightly regulated process at the level of both costimulatory and coinhibitory receptors. One such coinhibitory receptor or checkpoint inhibitor which has received much attention in the field of oncology is the programmed cell death protein 1 (PD-1). Blockade of PD-1 or its ligand PD-L1 has proven successful in the treatment of a wide variety of cancers, therefore highlighting an important role for this pathway in anti-tumour immune responses. However, a caveat of PD-1 therapy and boosting anti-tumour immune responses is the development of self-reactive T cells which can lead to the induction of various autoimmune or inflammatory diseases, referred to as immune- related adverse events (irAEs). The emergence of rheumatological irAEs such as Inflammatory Arthritis (IA) in recent years has highlighted the importance of PD-1 in maintaining self-tolerance. Furthermore, the emergence of rheumatology related irAEs raises an important question as to how defects in this pathway can contribute to spontaneous rheumatological disease. In this review, we describe the biological distribution, function and regulation of the PD-1 pathway, its potential role in IA and irAE related IA.

NOTCH3 is a Prognostic Factor and Is Correlated With Immune Tolerance in Gastric Cancer

Introduction

Although traditional treatments confer survival benefits to patients with gastric cancer (GC), many patients experience relapse soon after postoperative adjuvant therapy. Immune-related mechanisms play an important role in GC, and immunotherapeutic strategies are considered to be a promising direction for the treatment of GC. Thus, our study aimed to investigate the expression and prognostic significance of immune-related genes in GC.

Methods

Formalin-fixed, paraffin-embedded samples were collected from 48 resectable GC patients. The transcriptome data of the tumor immune microenvironment were assessed using an immuno-oncology 395-gene panel RNA sequencing platform. The prognostic value of the 395 genes was analyzed and validated in the KM plotter and GEPIA databases. The data from The Cancer Genome Atlas (TCGA, downloaded from UCSC Xena repository) and Tumor IMmune Estimation Resource (TIMER) were used to evaluate the correlations between prognostic factors and immune signatures.

Results

Among the 395 genes, NOTCH3 was identified as a good prognostic factor for GC patients. Its prognostic value was also suggested in both our GC cohort from Zhongshan Hospital and the public databases (KM plotter and GEPIA database). Mechanistically, high NOTCH3 expression correlated with a lower infiltration of activated CD8⁺ T cells and a higher infiltration of immunosuppressive cells including Tregs and M2 macrophages in the tumor microenvironment. Moreover, high NOTCH3 expression was accompanied by the increased expression of a series of immune checkpoint inhibitors, resulting in a dampened immune response. Interestingly, NOTCH3 expression had a negative association with well-documented predictive biomarkers of immune checkpoint blockade (ICB) immunotherapy, including tumor mutation burden (TMB), gene expression profiling (GEP) score and innate anti-PD-1 resistance (IPRES) signature.

Conclusion

These findings uncovered a new mechanism by which NOTCH3 participates in the immune tolerance of GC, implying the potential of NOTCH3 as a therapeutic target or predictive marker for GC patients.

KLHL22 maintains PD-1 homeostasis and prevents excessive T cell suppression

Aberrant programmed cell death protein 1 (PD-1) expression on the surface of T cells is known to inhibit T cell effector activity and to play a pivotal role in tumor immune escape; thus, maintaining an appropriate level of PD-1 expression is of great significance. We identified KLHL22, an adaptor of the Cul3-based E3 ligase, as a major PD-1-associated protein that mediates the degradation of PD-1 before its transport to the cell surface. KLHL22 deficiency leads to overaccumulation of PD-1, which represses the antitumor response of T cells and promotes tumor progression. Importantly, KLHL22 was markedly decreased in tumor-infiltrating T cells from colorectal cancer patients. Meanwhile, treatment with 5-fluorouracil (5-FU) could increase PD-1 expression by inhibiting the transcription of KLHL22. These findings reveal that KLHL22 plays a crucial role in preventing excessive T cell suppression by maintaining PD-1 expression homeostasis and suggest the therapeutic potential of 5-FU in combination with anti-PD-1 in colorectal cancer patients.

Notch Signaling and the Breast Cancer Microenvironment

Notch promotes breast cancer progression through tumor initiating cell maintenance, tumor cell fate specification, proliferation, survival, and motility. In addition, Notch is recognized as a decisive mechanism in regulating various juxtacrine and paracrine communications in the tumor microenvironment (TME). In this chapter, we review recent studies on stress-mediated Notch activation within the TME and sequelae such as angiogenesis, extracellular matrix remodeling, changes in the innate and adaptive immunophenotype, and therapeutic perspectives.

Reinvigorating exhausted CD8+ cytotoxic T lymphocytes in the tumor microenvironment and current strategies in cancer immunotherapy

Immunotherapy has revolutionized the treatment of cancer in recent years and achieved overall success and long-term clinical benefit in patients with a wide variety of cancer types. However, there is still a large proportion of patients exhibiting limited or no responses to immunotherapeutic strategy, some of which were even observed with hyperprogressive disease. One major obstacle restricting the efficacy is that tumor-reactive CD8⁺ T cells, which are central for tumor control, undergo exhaustion, and lose their ability to eliminate cancer cells after infiltrating into the strongly immunosuppressive tumor microenvironment. Thus, as a potential therapeutic rationale in the development of cancer immunotherapy, targeting or reinvigorating exhausted CD8⁺ T cells has been attracting much interest. Hitherto, both intrinsic and extrinsic mechanisms that govern CD8⁺ T-cell exhaustion have been explored. Specifically, the transcriptional and epigenetic landscapes have been depicted utilizing single-cell RNA sequencing or mass cytometry (CyTOF). In addition, cellular metabolism dictating the tumor-infiltrating CD8⁺ T-cell fate is currently under investigation. A series of clinical trials are being carried out to further establish the current strategies targeting CD8⁺ T-cell exhaustion. Taken together, despite the proven benefit of immunotherapy in cancer patients, additional efforts are still needed to fully circumvent limitations of exhausted T cells in the treatment. In this review, we will focus on the current cellular and molecular understanding of metabolic changes, epigenetic remodeling, and transcriptional regulation in CD8⁺ T-cell exhaustion and describe hypothetical treatment approaches based on immunotherapy aiming at reinvigorating exhausted CD8⁺ T cells.

Specific Targeting of Notch Ligand-Receptor Interactions to Modulate Immune Responses: A Review of Clinical and Preclinical Findings

Understanding and targeting Notch signaling effectively has long been valued in the field of cancer and other immune disorders. Here, we discuss key discoveries at the intersection of Notch signaling, cancer and immunology. While there is a plethora of Notch targeting agents tested in vitro, in vivo and in clinic, undesirable off-target effects and therapy-related toxicities have been significant obstacles. We make a case for the clinical application of ligand-derived and affinity modifying compounds as novel therapeutic agents and discuss major research findings with an emphasis on Notch ligand-specific modulation of immune responses.

Cancer and HIV-1 Infection: Patterns of Chronic Antigen Exposure

The main role of the human immune system is to eliminate cells presenting foreign antigens and abnormal patterns, while maintaining self-tolerance. However, when facing highly variable pathogens or antigens very similar to self-antigens, this system can fail in completely eliminating the anomalies, leading to the establishment of chronic pathologies. Prototypical examples of immune system defeat are cancer and Human Immunodeficiency Virus-1 (HIV-1) infection. In both conditions, the immune system is persistently exposed to antigens leading to systemic inflammation, lack of generation of long-term memory and exhaustion of effector cells. This triggers a negative feedback loop where effector cells are unable to resolve the pathology and cannot be replaced due to the lack of a pool of undifferentiated, self-renewing memory T cells. In addition, in an attempt to reduce tissue damage due to chronic inflammation, antigen presenting cells and myeloid components of the immune system activate systemic regulatory and tolerogenic programs. Beside these homologies shared between cancer and HIV-1 infection, the immune system can be shaped differently depending on the type and distribution of the eliciting antigens with ultimate consequences at the phenotypic and functional level of immune exhaustion. T cell differentiation, functionality, cytotoxic potential and proliferation reserve, immune-cell polarization, upregulation of negative regulators (immune checkpoint molecules) are indeed directly linked to the quantitative and qualitative differences in priming and recalling conditions. Better understanding of distinct mechanisms and functional consequences underlying disease-specific immune cell dysfunction will contribute to further improve and personalize immunotherapy. In the present review, we describe relevant players of immune cell exhaustion in cancer and HIV-1 infection, and enumerate the best-defined hallmarks of T cell dysfunction. Moreover, we highlight shared and divergent aspects of T cell exhaustion and T cell activation to the best of current knowledge.

Glycogen synthase 3 (GSK-3) regulation of PD-1 expression and and its therapeutic implications

The past few years have witnessed exciting progress in the application of immune check-point blockade (ICB) for the treatment of various human cancers. ICB was first used against cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) to demonstrate durable anti-tumor responses followed by ICB against programmed cell death-1 (PD-1) or its ligand, PD-L1. Present approaches involve the use of combinations of blocking antibodies against CTLA-4, PD-1 and other inhibitory receptors (IRs) such as TIM3, TIGIT and LAG3. Despite this success, most patients are not cured by ICB therapy and there are limitations to the use of antibodies including cost, tumor penetration, the accessibility of receptors, and clearance from the cell surface as well as inflammatory and autoimmune complications. Recently, we demonstrated that the down-regulation or inhibition of glycogen synthase kinase 3 (GSK-3) down-regulates PD-1 expression in infectious diseases and cancer (Taylor et al., 2016 Immunity 44, 274-86; 2018 Cancer Research 78, 706-717; Krueger and Rudd 2018 Immunity 46, 529-531). In this Review, we outline the use of small molecule inhibitors (SMIs) that target intracellular pathways for co-receptor blockade in cancer immunotherapy.