SHP-1 and SHP-2 associate with immunoreceptor tyrosine-based switch motif of programmed death 1 upon primary human T cell stimulation, but only receptor ligation prevents T cell activation

Targeting PD-1 post-translational modifications for improving cancer immunotherapy

Programmed cell death protein 1 (PD-1) is a critical immune checkpoint receptor that suppresses immune responses largely through its interaction with PD-L1. Tumors exploit this mechanism to evade immune surveillance, positioning immune checkpoint inhibitors targeting the PD-1/PD-L1 axis as groundbreaking advancements in cancer therapy. However, the overall effectiveness of these therapies is often constrained by an incomplete understanding of the underlying mechanisms. Recent research has uncovered the pivotal role of various post-translational modifications (PTMs) of PD-1, including ubiquitination, UFMylation, phosphorylation, palmitoylation, and glycosylation, in regulating its protein stability, localization, and protein-protein interactions. As much, dysregulation of these PTMs can drive PD-1-mediated immune evasion and contribute to therapeutic resistance. Notably, targeting PD-1 PTMs with small-molecule inhibitors or monoclonal antibodies (MAbs) has shown potential to bolster anti-tumor immunity in both pre-clinical mouse models and clinical trials. This review highlights recent findings on PD-1's PTMs and explores emerging therapeutic strategies aimed at modulating these modifications. By integrating these mechanistic insights, the development of combination cancer immunotherapies can be further rationally advanced, offering new avenues for more effective and durable treatments.

Intravesical chemotherapy enhances anti-tumor immunity in bladder cancer by modulating CD8+ T cell activation and Treg populations

Bladder cancer is one of the most common malignancies of the urinary system, with standard treatments including surgery, radiotherapy, and chemotherapy. However, these conventional approaches often yield suboptimal outcomes, necessitating exploring alternative therapeutic strategies. This study evaluated the efficacy of intravesical chemotherapy, both alone and in combination with immunotherapy, using an orthotopic mouse model of bladder cancer. To establish the model, luciferase-expressing bladder cancer cells were orthotopically implanted into immunocompetent mice. Treatment efficacy was assessed by monitoring changes in bioluminescence imaging (BLI) signal intensity, indicative of tumor burden, and by measuring tumor weights post-mortem. Mice were divided into four groups: G1: untreated control; G2: intravesical chemotherapy with 40 mph Doxorubicin (0.05 ml per mouse, bladder instillation); G3intraperitoneal (i.p.) chemotherapy with 10 mph Doxorubicin; G4: immune combination therapy with 10 mph Doxorubicin (i.p.) plus 10 mph PD-L1 inhibitor (i.p.). Results demonstrated that intravesical chemotherapy significantly reduced tumor burden compared to both conventional systemic chemotherapy and immune combination therapy (p-value <0.05). Flow cytometry analysis revealed a notable decrease in CD8+ T cell expression in both the intravesical and conventional chemotherapy groups (p value < 0.01). Additionally, Treg cell expression was moderately reduced in the conventional and immune combination therapy groups (p value < 0.05). Notably, intravesical chemotherapy led to a significant increase in CD69 activation on CD8+ T cells (p value < 0.05), suggesting enhanced T cell activation, while also moderately reducing PD-1 expression, a marker of T cell exhaustion (p value < 0.05).Histological analysis, including hematoxylin and eosin (HE) staining and Ki-67 immunohistochemistry, further confirmed significant differences in tumor morphology and proliferation among the treatment groups (p value < 0.05). These findings suggest that intravesical chemotherapy not only exerts a direct anti-tumor effect but also modulates the immune response by activating CD8+ T cells and mitigating T cell exhaustion. To conclusion, this study highlights the potential of intravesical chemotherapy as a promising and clinically feasible approach for bladder cancer treatment, warranting further investigation in translational and clinical practice.

T cell aging and exhaustion: Mechanisms and clinical implications

T cell senescence and exhaustion represent critical aspects of adaptive immune system dysfunction, with profound implications for health and the development of disease prevention and therapeutic strategies. These processes, though distinct, are interconnected at the molecular level, leading to impaired effector functions and reduced proliferative capacity of T cells. Such impairments increase susceptibility to diseases and diminish the efficacy of vaccines and treatments. Importantly, T cell senescence and exhaustion can dynamically influence each other, particularly in the context of chronic diseases. A deeper understanding of the molecular mechanisms underlying T cell senescence and exhaustion, as well as their interplay, is essential for elucidating the pathogenesis of related diseases and restoring dysfunctional immune responses. This knowledge will pave the way for the development of targeted therapeutic interventions and strategies to enhance immune competence. This review aims to summarize the characteristics, mechanisms, and disease associations of T cell senescence and exhaustion, while also delineating the distinctions and intersections between these two states to enhance our comprehension.

Development of a Peptide Inhibitor Targeting the C-SH2 Domain of the SHP2 Phosphatase

Src homology 2 (SH2) domain-containing phosphatase 2 (SHP2) mediates important signal transduction upon cell surface receptor stimulation, regulating multiple cellular functions. In addition to the catalytically active phosphotyrosine (pTyr) phosphatase domain, SHP2 contains two regulatory pTyr-binding domains: the N-SH2 and C-SH2 domains. While the role of the N-SH2 domain is well understood, the role of the C-SH2 domain is less clear. To support studies on the involvement of the domains in SHP2 function, herein, the development of a peptide inhibitor containing a nonhydrolysable pTyr mimetic, which selectively binds to the C-SH2 domain of SHP2 and blocks its protein-protein interactions, is described. Incorporation of the pTyr mimetic l-O-malonyltyrosine (l-OMT) results in robust binding affinity to the C-SH2 domain, while the widely used pTyr mimetic phosphonodifluoromethyl phenylalanine (F2Pmp) abolishes binding, showing that this mimetic is not a general binder of SH2 domains, which challenges existing notions. The C-SH2 inhibitor peptide (CSIP) is stable, selective, cell permeable, and noncytotoxic. CSIP enriches the toolbox of inhibitors with different modes of action targeting SHP2, and will support studies to better understand SHP2 regulation and interactions, which can ultimately inform new drug discovery efforts.

Mechanisms of CD8+ T cell exhaustion and its clinical significance in prognosis of anti-tumor therapies: A review

In recent years, immunotherapy has gradually become one of the main strategies for cancer treatment, with immune checkpoint inhibitors (ICIs) offering new possibilities for tumor therapy. However, some cancer patients exhibit low responses and resistance to ICIs treatment. T cell exhaustion, a process associated with tumor progression, refers to a subset of T cells that progressively lose effector functions and exhibit increased expression of inhibitory receptors. These exhausted T cells are considered key players in the therapeutic efficacy of immune checkpoint inhibitors. Therefore, understanding the impact of T cell exhaustion on tumor immunotherapy and the underlying mechanisms is critical for improving clinical treatment outcomes. Several elegant studies have provided insights into the prognostic value of exhausted T cells in cancers. In this review, we highlight the process of exhausted T cells and its predictive value in various cancers, as well as the relevant mechanisms behind it, providing new insights into the immunotherapy of cancer.

Programmed Death-1 Ligand 1 Domain Organization, Signaling Motifs, and Interactors in Cancer Immunotherapy

Immunotherapies targeting the programmed cell death-1 ligand 1 (PD-L1) and programmed cell death 1 (PD-1) pathway sparked a revolution in cancer treatment. These breakthrough therapies work by disrupting the interaction between PD-1-expressed on T cells-and its ligand PD-L1, commonly found on the surface of cancer cells. By using monoclonal antibodies to block this binding, the immune system is unleashed to fight cancer more effectively. However, PD-L1's role extends far beyond immune evasion. When situated on cancer cells, PD-L1 transmits inhibitory signals through PD-1, silencing the effector functions of T cells. However, PD-L1 also engages in reverse signaling, also called intrinsic signaling, delivering intracellular instructions that contribute to cancer cell survival, even in the absence of PD-1 binding. This signaling cascade shields cancer cells from apoptosis, drives proliferation, regulates DNA damage responses, and even functions as a co-transcriptional transactivator, amplifying cancer's ability to thrive. The intricate mechanisms behind PD-L1's intrinsic signaling are under intense investigation. In this review, we provide a historical perspective on the discoveries leading to PD-L1's structure, signaling motifs, and interacting partners, shedding light on its multifaceted roles and the promising therapeutic possibilities ahead.

TIM-3 teams up with PD-1 in cancer immunotherapy: mechanisms and perspectives

Immunotherapy using immune checkpoint inhibitors (ICIs) has become a prominent strategy for cancer treatment over the past ten years. However, the efficacy of ICIs remains limited, with certain cancers exhibiting resistance to these therapeutic approaches. Consequently, several immune checkpoint proteins are presently being thoroughly screened and assessed in both preclinical and clinical studies. Among these candidates, T cell immunoglobulin and mucin-domain containing-3 (TIM-3) is considered a promising target. TIM-3 exhibits multiple immunosuppressive effects on various types of immune cells. Given its differential expression levels at distinct stages of T cell dysfunction in the tumor microenvironment (TME), TIM-3, along with programmed cell death protein 1 (PD-1), serves as indicators of T cell exhaustion. Moreover, it is crucial to carefully evaluate the impact of TIM-3 and PD-1 expression in cancer cells on the efficacy of immunotherapy. To increase the effectiveness of anti-TIM-3 and anti-PD-1 therapies, it is proposed to combine the inhibition of TIM-3, PD-1, and programmed death-ligand 1 (PD-L1). The efficacy of TIM-3 inhibition in conjunction with PD-1/PD-L1 inhibitors is being evaluated in a number of ongoing clinical trials for patients with various cancers. This study systematically investigates the fundamental biology of TIM-3 and PD-1, as well as the detailed mechanisms through which TIM-3 and PD-1/PD-L1 axis contribute to cancer immune evasion. Additionally, this article provides a thorough analysis of ongoing clinical trials evaluating the synergistic effects of combining PD-1/PD-L1 and TIM-3 inhibitors in anti-cancer treatment, along with an overview of the current status of TIM-3 and PD-1 antibodies.

Shp-1 regulates the activity of low-affinity T cells specific to endogenous self-antigen during melanoma tumor growth and drives resistance to immune checkpoint inhibition

BACKGROUND

The presence of activated CD8 T cells in the tumor microenvironment is correlated with an effective immune response to immune checkpoint inhibitor (ICI) therapy. However, ICI predominantly targets high-affinity T cells, which may be less abundant in tumors with few neoantigens. Targeting the intracellular phosphatase Src homology region 2 domain-containing phosphatase-1 (Shp-1) in combination with ICI lowers the T cell activation threshold and enhances the ability of low-affinity T cells to mount a productive antitumor response.

METHODS

In this study, we sought to determine whether temporal inhibition of Shp-1 during active tumor growth could rescue the activity of low-affinity T cells specific for endogenous self-antigens. To address this question, we implanted Yale University Mouse Melanoma (YUMM) tumor cell lines into WT mice and, on tumor establishment, administered an inhibitor of Shp-1 (TPI-1) with or without ICI treatment. We analyzed treatment-dependent changes in the immune infiltrate in the tumor via flow cytometry, major histocompatibility complex (MHC) tetramer-mediated detection of tyrosinase-related protein 2 (TRP-2)180-188-specific T cells and a micropipette-based two-dimensional affinity assay to measure the T cell receptor (TCR) affinity.

RESULTS

Administration of ICI and a Shp-1 inhibitor to mice with established YUMM tumors, but neither agent alone, resulted in a significant delay in tumor growth and an increased frequency of CD8 tumor-infiltrating T cells with enhanced effector and reduced exhaustion characteristics. In particular, combined treatment increased the frequency of CD8 T cells specific for the MHC Class I-restricted tumor self-antigen TRP-2180-188. We found that the increase in effector T cells was almost entirely due to an increase in T cells with very low TCR affinity.

CONCLUSIONS

We conclude that approaches for altering TCR signaling threshold are effective in enhancing the antitumor response of low-affinity T cells specific for endogenous self-antigens in settings of ICI resistance and/or where neoantigens are not available to drive antitumor responses.

From Bench to Bladder: The Rise in Immune Checkpoint Inhibition in the Treatment of Non-Muscle Invasive Bladder Cancer

Non-muscle invasive bladder cancer (NMIBC) represents a significant clinical challenge due to its high recurrence rate and need for frequent monitoring. The current treatment modality is bacillus Calmette-Guérin (BCG) therapy combined with chemotherapy after transurethral resection of the bladder tumor (TURBT), which is highly effective in most patients. Yet, the cancer becomes resistant to these treatments in 30-40% of patients, necessitating the need for new treatment modalities. In the cancer world, the development of immune checkpoint inhibitors that target molecules, such as programmed cell death protein-1 (PD-1), its ligand, PD-L1, and Cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), have revolutionized the treatment of many cancer types. PD-1/PD-L1 and CTLA-4 are shown to be upregulated in NMIBC in certain circumstances. PD-1/PD-L1 interactions play a role in immune evasion by suppressing T cell activity within the tumor microenvironment (TME), while the binding of CTLA-4 on T cells leads to downregulation of the immune response, making these pathways potential immunotherapeutic targets in NMIBC. This review seeks to understand the role of these therapies in treating NMIBC. We explore the cellular and non-cellular immune landscape in the TME of NMIBC, including Tregs, T effector cells, macrophages, B cells, and relevant cytokines. We also discuss the biological role of PD-1/PD-L1 and CTLA-4 while covering the rationale for these immunotherapies in NMIBC. Finally, we cover key clinical trials that have studied these treatments in NMIBC clinically. Such a study will be helpful for urologists and oncologists to manage patients with NMIBC more effectively.

Post-translational modifications of immune checkpoints: unlocking new potentials in cancer immunotherapy

Immunotherapy targeting immune checkpoints has gained traction across various cancer types in clinical settings due to its notable advantages. Despite this, the overall response rates among patients remain modest, alongside issues of drug resistance and adverse effects. Hence, there is a pressing need to enhance immune checkpoint blockade (ICB) therapies. Post-translational modifications (PTMs) are crucial for protein functionality. Recent research emphasizes their pivotal role in immune checkpoint regulation, directly impacting the expression and function of these key proteins. This review delves into the influence of significant PTMs-ubiquitination, phosphorylation, and glycosylation-on immune checkpoint signaling. By targeting these modifications, novel immunotherapeutic strategies have emerged, paving the way for advancements in optimizing immune checkpoint blockade therapies in the future.

Revolutionary Cancer Therapy for Personalization and Improved Efficacy: Strategies to Overcome Resistance to Immune Checkpoint Inhibitor Therapy

Cancer remains a significant public health issue worldwide, standing as a primary contributor to global mortality, accounting for approximately 10 million fatalities in 2020 [...].

Autologous Human Dendritic Cells from XDR-TB Patients Polarize a Th1 Response Which Is Bactericidal to Mycobacterium tuberculosis

Extensively drug-resistant tuberculosis (XDR-TB) is a public health concern as drug resistance is outpacing the drug development pipeline. Alternative immunotherapeutic approaches are needed. Peripheral blood mononuclear cells (PBMCs) were isolated from pre-XDR/XDR-TB (n = 25) patients and LTBI (n = 18) participants. Thereafter, monocytic-derived dendritic cells (mo-DCs) were co-cultured with M. tb antigens, with/without a maturation cocktail (interferon-γ, interferon-α, CD40L, IL-1β, and TLR3 and TLR7/8 agonists). Two peptide pools were evaluated: (i) an ECAT peptide pool (ESAT6, CFP10, Ag85B, and TB10.4 peptides) and (ii) a PE/PPE peptide pool. Sonicated lysate of the M. tb HN878 strain served as a control. Mo-DCs were assessed for DC maturation markers, Th1 cytokines, and the ability of the DC-primed PBMCs to restrict the growth of M. tb-infected monocyte-derived macrophages. In pre-XDR/XDR-TB, mo-DCs matured with M. tb antigens (ECAT or PE/PPE peptide pool, or HN878 lysate) + cocktail, compared to mo-DCs matured with M. tb antigens only, showed higher upregulation of co-stimulatory molecules and IL-12p70 (p < 0.001 for both comparisons). The matured mo-DCs had enhanced antigen-specific CD8+ T-cell responses to ESAT-6 (p = 0.05) and Ag85B (p = 0.03). Containment was higher with mo-DCs matured with the PE/PPE peptide pool cocktail versus mo-DCs matured with the PE/PPE peptide pool (p = 0.0002). Mo-DCs matured with the PE/PPE peptide pool + cocktail achieved better containment than the ECAT peptide pool + cocktail [50%, (IQR:39-75) versus 46%, (IQR:15-62); p = 0.02]. In patients with pre-XDR/XDR-TB, an effector response primed by mo-DCs matured with an ECAT or PE/PPE peptide pool + cocktail was capable of restricting the growth of M. tb in vitro.

PD-1 blockade treatment in melanoma: Mechanism of response and tumor-intrinsic resistance

Malignant melanoma is characterized by high immunogenicity, genetic heterogeneity, and diverse pathological manifestations, affecting both skin and mucosa over the body. Pembrolizumab and nivolumab, both anti-PD-1 monoclonal antibodies, were approved by the US FDA for unresectable or metastatic melanoma in 2011 and 2014, respectively, with enduring and transformative outcomes. Despite marked clinical achievements, only a subset of patients manifested a complete response. Approximately 55% of melanoma patients exhibited primary resistance to PD-1 antibodies, with nearly 25% developing secondary resistance within 2 years of treatment. Thus, there is a critical need to comprehensively elucidate the mechanisms underlying the efficacy and resistance to PD-1 blockade. This review discusses the fundamental mechanisms of PD-1 blockade, encompassing insights from T cells and B cells, and presents resistance to anti-PD-1 with a particular focus on tumoral-intrinsic mechanisms in melanoma.

Beyond peptides: Unveiling the design strategies, structure activity correlations and protein-ligand interactions of small molecule inhibitors against PD-1/PD-L1

The landscape of cancer treatment has been transformed by the emergence of immunotherapy, especially through the use of antibodies that target the PD-1/PD-L1 pathway. Recently, there has been a notable increase in interest surrounding immune checkpoint inhibitors for cancer therapy. While antibody-based approaches have drawbacks like high costs and prolonged activity, the approval of monoclonal antibodies such as pembrolizumab and nivolumab has paved the way for a range of alternative therapies, including peptides, peptidomimetics, and small-molecule inhibitors. These smaller molecules, which target the PD-1/PD-L1 interaction, are seen as potential substitutes or supplements to monoclonal antibodies. Our focus in this article is primarily on exploring small molecules designed for PD-1/PD-L1 checkpoint pathway modulation in cancer immunotherapy, along with highlighting current advances in their structural and preclinical/clinical development. The pursuit of therapeutics based on small-molecule inhibitors of the PD-1/PD-L1 axis offers a promising yet intricate avenue for advancing cancer treatment.

A comprehensive review of immune checkpoint inhibitors for cancer treatment

Immunology-based therapies are emerging as an effective cancer treatment, using the body's immune system to target tumors. Immune checkpoints, which regulate immune responses to prevent tissue damage and autoimmunity, are often exploited by cancer cells to avoid destruction. The discovery of checkpoint proteins like PD-1/PD-L1 and CTLA-4 was pivotal in developing cancer immunotherapy. Immune checkpoint inhibitors (ICIs) have shown great success, with FDA-approved drugs like PD-1 inhibitors (Nivolumab, Pembrolizumab, Cemiplimab), PD-L1 inhibitors (Atezolizumab, Durvalumab, Avelumab), and CTLA-4 inhibitors (Ipilimumab, Tremelimumab), alongside LAG-3 inhibitor Relatlimab. Research continues on new checkpoints like TIM-3, VISTA, B7-H3, BTLA, and TIGIT. Biomarkers like PDL-1 expression, tumor mutation burden, interferon-γ presence, microbiome composition, and extracellular matrix characteristics play a crucial role in predicting responses to immunotherapy with checkpoint inhibitors. Despite their effectiveness, not all patients experience the same level of benefit, and organ-specific immune-related adverse events (irAEs) such as rash or itching, colitis, diarrhea, hyperthyroidism, and hypothyroidism may occur. Given the rapid advancements in this field and the variability in patient outcomes, there is an urgent need for a comprehensive review that consolidates the latest findings on immune checkpoint inhibitors, covering their clinical status, biomarkers, resistance mechanisms, strategies to overcome resistance, and associated adverse effects. This review aims to fill this gap by providing an analysis of the current clinical status of ICIs, emerging biomarkers, mechanisms of resistance, strategies to enhance therapeutic efficacy, and assessment of adverse effects. This review is crucial to furthering our understanding of ICIs and optimizing their application in cancer therapy.

Association between programmed death protein 1-related single-nucleotide polymorphisms and immune-related adverse events induced by programmed death protein 1 inhibitors-a pilot study

Programmed death protein 1 (PD-1) inhibitors have potent anti-tumor activities. However, they often result in immune-related adverse events (irAEs) of varying severity. Therefore, the factors affecting the incidence of irAEs warrant urgent investigation. This study aimed to identify specific and sensitive predictors of irAEs in a Chinese population. We conducted a genome-wide association study (GWAS) comprising 80 patients with malignant tumors to evaluate single-nucleotide polymorphism (SNP) loci associated with the incidence of irAEs. The SNP rs2157775 on the LOC339166 gene had the lowest P value but did not reach the significance threshold after Bonferroni correction. Therefore, potentially associated SNPs were further investigated through the mechanism-related PD-1 pathway using the ImmPort and PathCards Human Gene Databases. A binary logistic regression model revealed that CD3E (rs3782040) A/A was associated with a lower incidence of irAEs in patients with malignant tumors who received PD-1 inhibitors. In contrast, PTPN11 (rs143894582) C/CA was associated with a higher incidence of irAEs. These findings provide a basis for the verification and identification of new loci to provide insight into the etiology of irAEs.

Efficacy of neoadjuvant PD-1/PD-L1 inhibitor in resectable NSCLC: a meta-analysis based on randomized controlled trials

BACKGROUND

The efficacy of neoadjuvant immunotherapy in resectable non-small-cell lung cancer (NSCLC) is controversial. The aim of this study is to explore the efficacy of additional PD-1/PD-L1 inhibitors in the neoadjuvant treatment of resctable NSCLC.

METHODS

Data sources included Cochrane Library, Embase, Web of Science, and PubMed from beginning of the database creation to May 2024. The primary outcomes of the study included event-free survival (EFS), overall survival (OS), pathological complete response (pCR), major pathological response (MPR).

RESULTS

Seven RCTs, including 2929 patients, were included in the analysis. The results showed that the experimental group had significantly higher rates of pCR (RR = 5.9, p < 0.001) and MPR (RR = 2.88, p < 0.001) compared to the control group. OS (HR = 0.57) and EFS (HR = 0.58) was also significantly improved in the experimental group. Subgroup analysis of EFS revealed that the benefit was higher in the East (HR = 0.56) than in the West (HR = 0.70). Additionally, the benefit seemed to rise with PD-L1 tumor cell proportion score (TPS) (TPS < 1%, HR = 0.76; 1% < TPS < 49%, HR = 0.56; TPS ≥ 50%, HR = 0.38). The benefit degree seemed to be higher in the III period patients (HR = 0.75) than I-II period patients (HR = 0.52). It is important to emphasize that smokers (HR = 0.54, p < 0.001) benefited from neoadjuvant immunotherapy but nonsmokers (HR = 0.68, p = 0.055) did not.

CONCLUSION

Neoadjuvant PD-1/PD-L1 inhibitor combined with chemotherapy can significantly improve the short-term and long-term prognosis of patients with resectable NSCLC. Moreover, the efficacy of this treatment regimen may be affected by different clinicopathological characteristics of patients.

Deep phosphotyrosine characterisation of primary murine T cells using broad spectrum optimisation of selective triggering

Sequencing the tyrosine phosphoproteome using MS-based proteomics is challenging due to the low abundance of tyrosine phosphorylation in cells, a challenge compounded in scarce samples like primary cells or clinical samples. The broad-spectrum optimisation of selective triggering (BOOST) method was recently developed to increase phosphotyrosine sequencing in low protein input samples by leveraging tandem mass tags (TMT), phosphotyrosine enrichment, and a phosphotyrosine-loaded carrier channel. Here, we demonstrate the viability of BOOST in T cell receptor (TCR)-stimulated primary murine T cells by benchmarking the accuracy and precision of the BOOST method and discerning significant alterations in the phosphoproteome associated with receptor stimulation. Using 1 mg of protein input (about 20 million cells) and BOOST, we identify and precisely quantify more than 2000 unique pY sites compared to about 300 unique pY sites in non-BOOST control samples. We show that although replicate variation increases when using the BOOST method, BOOST does not jeopardise quantitative precision or the ability to determine statistical significance for peptides measured in triplicate. Many pY previously uncharacterised sites on important T cell signalling proteins are quantified using BOOST, and we identify new TCR responsive pY sites observable only with BOOST. Finally, we determine that the phase-spectrum deconvolution method on Orbitrap instruments can impair pY quantitation in BOOST experiments.

Neoantigen-specific mRNA/DC vaccines for effective anticancer immunotherapy

The development of personalized anticancer vaccines based on neoantigens represents a new direction in cancer immunotherapy. The latest advancement in dendritic cell (DC) tumor vaccine construction involves loading DC with mRNA-encoding neoantigens, which allows for rapid production and is suitable for personalized preparation. Cell-penetrating peptides (CPPs) are emerging as biological delivery systems in which negatively charged nucleic acids can be wound onto the cationic CPP backbone to form nanoscale complexes. This preparation method facilitates standardization. If DC can express and present neoantigen mRNA at high levels, it holds promising application potential. In this study, we developed a neoantigen-mRNA/DC vaccine using candidate neoantigens from mouse colon cancer (MC38) and examined its immune and antitumor effects. The results demonstrated that neoantigen-mRNA/DC vaccines induced strong T cell immune responses and exhibited significant antitumor effects, effectively preventing tumor growth. Our study provides an experimental basis for further optimizing the preparation of DC vaccines and reducing their costs.

PD-1 endocytosis unleashes the cytolytic potential of checkpoint blockade in tumor immunity

PD-1 immune checkpoint blockade (ICB) is a key cancer treatment. While blocking PD-1 binding to ligand is known, the role of internalization in enhancing ICB efficacy is less explored. Our study reveals that PD-1 internalization helps unlock ICB's full potential in cancer immunotherapy. Anti-PD-1 induces 50%-60% surface PD-1 internalization from human and mouse cells, leaving low to intermediate levels of resistant receptors. Complexes then appear in early and late endosomes. Both CD4 and CD8 T cells, especially CD8+ effectors, are affected. Nivolumab outperforms pembrolizumab in human T cells, while PD-1 internalization requires crosslinking by bivalent antibody. While mono- and bivalent anti-PD-1 inhibit tumor growth with CD8 tumor-infiltrating cells expressing increased granzyme B, bivalent antibody is more effective where the combination of steric blockade and endocytosis induces greater CD8+ T cell tumor infiltration and the expression of the cytolytic pore protein, perforin. Our findings highlight an ICB mechanism that combines steric blockade and PD-1 endocytosis for optimal checkpoint immunotherapy.

Hemophagocytic lymphohistiocytosis: current treatment advances, emerging targeted therapy and underlying mechanisms

Hemophagocytic lymphohistiocytosis (HLH) is a rapidly progressing, life-threatening syndrome characterized by excessive immune activation, often presenting as a complex cytokine storm. This hyperactive immune response can lead to multi-organ failure and systemic damage, resulting in an extremely short survival period if left untreated. Over the past decades, although HLH has garnered increasing attention from researchers, there have been few advancements in its treatment. The cytokine storm plays a crucial role in the treatment of HLH. Investigating the detailed mechanisms behind cytokine storms offers insights into targeted therapeutic approaches, potentially aiding in early intervention and improving the clinical outcome of HLH patients. To date, there is only one targeted therapy, emapalumab targeting interferon-γ, that has gained approval for primary HLH. This review aims to summarize the current treatment advances, emerging targeted therapeutics and underlying mechanisms of HLH, highlighting its newly discovered targets potentially involved in cytokine storms, which are expected to drive the development of novel treatments and offer fresh perspectives for future studies. Besides, multi-targeted combination therapy may be essential for disease control, but further trials are required to determine the optimal treatment mode for HLH.

The roles of migrasomes in immunity, barriers, and diseases

Migrasomes are recently identified extracellular vesicles and organelles formed in conjunction with cell migration. They are situated at the rear of migrating cells, exhibit a circular or elliptical membrane-enclosed structure, and function as a new organelle. Migrasomes selectively sort intercellular components, mediating a cell migration-dependent release mechanism known as migracytosis and modulating cell-cell communication. Accumulated evidence clarifies migrasome formation processes and indicates their diverse functional roles. Migrasomes may also be potentially correlated with the occurrence, progression, and prognosis of certain diseases. Migrasomes' involvement in physiological and pathological processes highlights their potential for expanding our understanding of biological procedures and as a target in clinical therapy. However, the precise mechanisms and full extent of their involvement in immunity, barriers, and diseases remain unclear. This review aimed to provide a comprehensive overview of the roles of migrasomes in human immunity and barriers, in addition to providing insights into their impact on human diseases. STATEMENT OF SIGNIFICANCE: Migrasomes, newly identified extracellular vesicles and organelles, form during cell migration and are located at the rear of migrating cells. These circular or elliptical structures mediate migracytosis, selectively sorting intercellular components and modulating cell-cell communication. Evidence suggests diverse functional roles for migrasomes, including potential links to disease occurrence, progression, and prognosis. Their involvement in physiological and pathological processes highlights their significance in understanding biological procedures and potential clinical therapies. However, their exact mechanisms in immunity, barriers, and diseases remain unclear. This review provides an overview of migrasomes' roles in human immunity and barriers, and their impact on diseases.

Cell Identity and Spatial Distribution of PD-1/PD-L1 Blockade Responders

The programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) axis inhibits T cell activity, impairing anti-tumor immunity. Blocking this axis with therapeutic antibodies is one of the most promising anti-tumor immunotherapies. It has long been recognized that PD-1/PD-L1 blockade reinvigorates exhausted T (TEX) cells already present in the tumor microenvironment (TME). However, recent advancements in high-throughput gene sequencing and bioinformatic tools have provided researchers with a more granular and dynamic insight into PD-1/PD-L1 blockade-responding cells, extending beyond the TME and TEX populations. This review provides an update on the cell identity, spatial distribution, and treatment-induced spatiotemporal dynamics of PD-1/PD-L1 blockade responders. It also provides a synopsis of preliminary reports of potential PD-1/PD-L1 blockade responders other than T cells to depict a panoramic picture. Important questions to answer in further studies and the translational and clinical potential of the evolving understandings are also discussed.

A novel bioinformatics pipeline for the identification of immune inhibitory receptors as potential therapeutic targets

Despite major successes with inhibitory receptor blockade in cancer, the identification of novel inhibitory receptors as putative drug targets is needed due to lack of durable responses, therapy resistance, and side effects. Most inhibitory receptors signal via immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and previous studies estimated that our genome contains over 1600 ITIM-bearing transmembrane proteins. However, testing and development of these candidates requires increased understanding of their expression patterns and likelihood to function as inhibitory receptor. Therefore, we designed a novel bioinformatics pipeline integrating machine learning-guided structural predictions and sequence-based likelihood models to identify putative inhibitory receptors. Using transcriptomics data of immune cells, we determined the expression of these novel inhibitory receptors, and classified them into previously proposed functional categories. Known and putative inhibitory receptors were expressed across different immune cell subsets with cell type-specific expression patterns. Furthermore, putative immune inhibitory receptors were differentially expressed in subsets of tumour infiltrating T cells. In conclusion, we present an inhibitory receptor pipeline that identifies 51 known and 390 novel human inhibitory receptors. This pipeline will support future drug target selection across diseases where therapeutic targeting of immune inhibitory receptors is warranted.

Changing the location of proteins on the cell surface is a promising strategy for modulating T cell functions

Targeting immune receptors on T cells is a common strategy to treat cancer and autoimmunity. Frequently, this is accomplished through monoclonal antibodies targeting the ligand binding sites of stimulatory or inhibitory co-receptors. Blocking ligand binding prevents downstream signalling and modulates specific T cell functions. Since 1985, the FDA has approved over 100 monoclonal antibodies against immune receptors. This therapeutic approach significantly improved the care of patients with numerous immune-related conditions; however, many patients are unresponsive, and some develop immune-related adverse events. One reason for that is the lack of consideration for the localization of these receptors on the cell surface of the immune cells in the context of the immune synapse. In addition to blocking ligand binding, changing the location of these receptors on the cell surface within the different compartments of the immunological synapse could serve as an alternative, efficient, and safer approach to treating these patients. This review discusses the potential therapeutic advantages of altering proteins' localization within the immune synapse and summarizes published work in this field. It also discusses the novel use of bispecific antibodies to induce the clustering of receptors on the cell surface. It presents the rationale for developing novel antibodies, targeting the organization of signalling receptor complexes on the cell surface. This approach offers an innovative and emerging technology to treat cancer patients resistant to current immunotherapies.

The role of programmed death receptor (PD-)1/PD-ligand (L)1 in periodontitis and cancer

The programmed-death-ligand-1 (PD-L1) is an immune-modulating molecule that is constitutively expressed on various immune cells, different epithelial cells and a multitude of cancer cells. It is a costimulatory molecule that may impair T-cell mediated immune response. Ligation to the programmed-death-receptor (PD)-1, on activated T-cells and further triggering of the related signaling pathways can induce T-cells apoptosis or anergy. The upregulation of PD-L1 in various cancer types, including oral squamous cell carcinomas, was demonstrated and has been linked to immune escape of tumors and poor prognosis. A bidirectional relationship exists between the increased PD-L1 expression and periodontitis as well as the epithelial-mesenchymal transition (EMT), a process of interconversion of epithelial cells to mesenchymal cells that may induce immune escape of tumors. Interaction between exosomal PD-L1 and PD-1 on T-cells may cause immunosuppression by blocking the activation and proliferation of T-cells. The efficacy and importance of treatment with PD-1/PD-L1 checkpoint inhibitors and their prognostic influence on human cancers was demonstrated. Regarding PD-1/PD-L1 checkpoint inhibitors, resistances exist or may develop, basing on various factors. Further investigations of the underlying mechanisms will help to overcome the therapeutic limitations that result from resistances and to develop new strategies for the treatment of cancer.

Immune checkpoint pathways in glioblastoma: a diverse and evolving landscape

Immune checkpoint (IC) inhibition in glioblastoma (GBM) has not shown promising results in the last decade compared to other solid tumors. Several factors contributing to the lack of immunotherapy response include the profound immunosuppressive nature of GBM, highly redundant signaling pathways underlying immune checkpoints, and the negative immunogenic impact of current standard of care on the tumor microenvironment. In this review, we will discuss various ICs in the context of GBM, their interplay with the tumor immune microenvironment, relevant pre-clinical and clinical studies, and the impact of current treatment modalities on GBM IC blockade therapy. Understanding the molecular mechanisms that drive ICs, and how they contribute to an immunosuppressive tumor microenvironment is critical in advancing IC inhibition therapy in GBM. Furthermore, revisiting current treatment modalities and their impact on the immune landscape is instrumental in designing future combinatorial therapies that may overcome treatment resistance.

Predictive Biomarkers and Resistance Mechanisms of Checkpoint Inhibitors in Malignant Solid Tumors

Predictive biomarkers for immune checkpoint inhibitors (ICIs) in solid tumors such as melanoma, hepatocellular carcinoma (HCC), colorectal cancer (CRC), non-small cell lung cancer (NSCLC), endometrial carcinoma, renal cell carcinoma (RCC), or urothelial carcinoma (UC) include programmed cell death ligand 1 (PD-L1) expression, tumor mutational burden (TMB), defective deoxyribonucleic acid (DNA) mismatch repair (dMMR), microsatellite instability (MSI), and the tumor microenvironment (TME). Over the past decade, several types of ICIs, including cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, anti-programmed cell death 1 (PD-1) antibodies, anti-programmed cell death ligand 1 (PD-L1) antibodies, and anti-lymphocyte activation gene-3 (LAG-3) antibodies have been studied and approved by the Food and Drug Administration (FDA), with ongoing research on others. Recent studies highlight the critical role of the gut microbiome in influencing a positive therapeutic response to ICIs, emphasizing the importance of modeling factors that can maintain a healthy microbiome. However, resistance mechanisms can emerge, such as increased expression of alternative immune checkpoints, T-cell immunoglobulin (Ig), mucin domain-containing protein 3 (TIM-3), LAG-3, impaired antigen presentation, and alterations in the TME. This review aims to synthesize the data regarding the interactions between microbiota and immunotherapy (IT). Understanding these mechanisms is essential for optimizing ICI therapy and developing effective combination strategies.

T cell exhaustion and senescence for ovarian cancer immunotherapy

Ovarian cancer is a common gynecological malignancy, and its treatment remains challenging. Although ovarian cancer may respond to immunotherapy because of endogenous immunity at the molecular or T cell level, immunotherapy has so far not had the desired effect. The functional status of preexisting T cells is an indispensable determinant of powerful antitumor immunity and immunotherapy. T cell exhaustion and senescence are two crucial states of T cell dysfunction, which share some overlapping phenotypic and functional features, but each status possesses unique molecular and developmental signatures. It has been widely accepted that exhaustion and senescence of T cells are important strategies for cancer cells to evade immunosurveillance and maintain the immunosuppressive microenvironment. Herein, this review summarizes the phenotypic and functional features of exhaust and senescent T cells, and describes the key drivers of the two T cell dysfunctional states in the tumor microenvironment and their functional roles in ovarian cancer. Furthermore, we present a summary of the molecular machinery and signaling pathways governing T cell exhaustion and senescence. Possible strategies that can prevent and/or reverse T cell dysfunction are also explored. An in-depth understanding of exhausted and senescent T cells will provide novel strategies to enhance immunotherapy of ovarian cancer through redirecting tumor-specific T cells away from a dysfunctional developmental trajectory.

Generation of Devil Facial Tumour Cells Co-Expressing MHC With CD80, CD86 or 41BBL to Enhance Tumour Immunogenicity

The major histocompatibility complex (MHC) molecules play an integral role in the adaptive immune response to transmissible cancers through tumour antigen presentation and recognition of allogeneic MHC molecules. The transmissible devil facial tumours 1 and 2 (DFT1 and DFT2) modulate MHC-I antigen presentation to evade host immune responses and facilitate transmission of tumours cells to new Tasmanian devil (Sarcophilus harrisii) hosts. To enhance T-cell-driven tumour immunogenicity for vaccination and immunotherapy, DFT1 and DFT2 cells were co-transfected with (i) NLRC5 for MHC-I expression or CIITA for MHC-I and MHC-II expression, and (ii) a co-stimulatory molecule, either CD80, CD86 or 41BBL. The co-transfected DFT cells presented enhanced expression of MHC-I and/or MHC-II. As few devil-specific monoclonal antibodies exist, we used recombinant CTLA4 and 41BB fused to a fluorescent protein to confirm expression of cell surface CD80, CD86 and 41BBL. The capacity for these cells to induce T-cell responses including PD1 and IFNG expression was evaluated in in vitro co-culture assays with captive devil peripheral blood mononuclear cells (PBMCs). Although PBMC viability had increased, there was no evidence of enhanced T-cell activation. This system can be used to identify additional factors required to promote activation of naïve devil T-cells in vitro.

PD-1/PD-L1 Provides Protective Role in Hypoxia-Induced Pulmonary Vascular Remodeling

BACKGROUND

Hypoxia-induced pulmonary hypertension (HPH) is a T helper 17 cell response-driven disease, and PD-1 (programmed cell death 1)/PD-L1 (programmed cell death-ligand 1) inhibitor-associated pulmonary hypertension has been reported recently. This study is designed to explore whether the PD-1/PD-L1 pathway participates in HPH via regulating endothelial dysfunction and T helper 17 cell response.

METHODS

Lung tissue samples were obtained from eligible patients. Western blotting, immunohistochemistry, and immunofluorescence techniques were used to assess protein expression, while immunoprecipitation was utilized to detect ubiquitination. HPH models were established in C57BL/6 WT (wild-type) and PD-1-/- mice, followed by treatment with PD-L1 recombinant protein. Adeno-associated virus vector delivery was used to upregulate PD-L1 in the endothelial cells. Endothelial cell function was assessed through assays for cell angiogenesis and adhesion.

RESULTS

Expression of the PD-1/PD-L1 pathway was downregulated in patients with HPH and mouse models, with a notable decrease in PD-L1 expression in endothelial cells compared with the normoxia group. In comparison to WT mice, PD-1-/- mice exhibited a more severe HPH phenotype following exposure to hypoxia, However, administration of PD-L1 recombinant protein and overexpression of PD-L1 in lung endothelial cells mitigated HPH. In vitro, blockade of PD-L1 with a neutralizing antibody promoted endothelial cell angiogenesis, adhesion, and pyroptosis. Mechanistically, hypoxia downregulated PD-L1 protein expression through ubiquitination. Additionally, both in vivo and in vitro, PD-L1 inhibited T helper 17 cell response through the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target of rapamycin) pathway in HPH.

CONCLUSIONS

PD-1/PD-L1 plays a role in ameliorating HPH development by inhibiting T helper 17 cell response through the PI3K/AKT/mTOR pathway and improving endothelial dysfunction, suggesting a novel therapeutic indication for PD-1/PD-L1-based immunomodulatory therapies in the treatment of HPH.

PD-1/LAG-3 co-signaling profiling uncovers CBL ubiquitin ligases as key immunotherapy targets

Many cancer patients do not benefit from PD-L1/PD-1 blockade immunotherapies. PD-1 and LAG-3 co-upregulation in T-cells is one of the major mechanisms of resistance by establishing a highly dysfunctional state in T-cells. To identify shared features associated to PD-1/LAG-3 dysfunctionality in human cancers and T-cells, multiomic expression profiles were obtained for all TCGA cancers immune infiltrates. A PD-1/LAG-3 dysfunctional signature was found which regulated immune, metabolic, genetic, and epigenetic pathways, but especially a reinforced negative regulation of the TCR signalosome. These results were validated in T-cell lines with constitutively active PD-1, LAG-3 pathways and their combination. A differential analysis of the proteome of PD-1/LAG-3 T-cells showed a specific enrichment in ubiquitin ligases participating in E3 ubiquitination pathways. PD-1/LAG-3 co-blockade inhibited CBL-B expression, while the use of a bispecific drug in clinical development also repressed C-CBL expression, which reverted T-cell dysfunctionality in lung cancer patients resistant to PD-L1/PD-1 blockade. The combination of CBL-B-specific small molecule inhibitors with anti-PD-1/anti-LAG-3 immunotherapies demonstrated notable therapeutic efficacy in models of lung cancer refractory to immunotherapies, overcoming PD-1/LAG-3 mediated resistance.

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.

Potential mechanisms and targeting strategies of the gut microbiota in antitumor immunity and immunotherapy

BACKGROUND

Immunotherapies, notably immune checkpoints inhibitors that target programmed death 1/programmed death ligand 1(PD-1/PD-L1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), had profoundly changed the way advanced and metastatic cancers are treated and dramatically improved overall and progression-free survival.

AIMS

This review article aimed to explore the underlying molecular mechanisms by which the gut microbiota affects antitumor immunity and the efficacy of cancer immunotherapy.

METHODS

We summarized the latest knowledge supporting the associations among the gut microbiota, antitumor immunity, and immunotherapy. Moreover, we disscussed the therapeutic strategy for improving immunotherapy efficacy by modulating gut microbiota in cancer treatment.

RESULTS

The potential molecular mechanisms underlying these associations are explained in terms of four aspects: immunomodulation, molecular mimicry, mamps, and microbial metabolites.

CONCLUSION

The gut microbiota significantly impacts antitumor immunity and alters the effectiveness of cancer immunotherapy.

PD1 inhibits PKCθ-dependent phosphorylation of cytoskeleton-related proteins and immune synapse formation

ABSTRACT

The inhibitory surface receptor programmed cell death protein 1 (PD1) is a major target for antibody-based cancer immunotherapies. Nevertheless, a substantial number of patients fail to respond to the treatment or experience adverse effects. An improved understanding of intracellular pathways targeted by PD1 is thus needed to develop better predictive and prognostic biomarkers. Here, via unbiased phosphoproteome analysis of primary human T cells, we demonstrate that PD1 triggering inhibited the phosphorylation and physical association with protein kinase Cθ (PKCθ) of a variety of cytoskeleton-related proteins. PD1 blocked activation and recruitment of PKCθ to the forming immune synapse (IS) in a Src homology-2 domain-containing phosphatase-1/2 (SHP1/SHP2)-dependent manner. Consequently, PD1 engagement led to impaired synaptic phosphorylation of cytoskeleton-related proteins and formation of smaller IS. T-cell receptor induced phosphorylation of the PKCθ substrate and binding partner vimentin was long-lasting and it could be durably inhibited by PD1 triggering. Vimentin phosphorylation in intratumoral T cells also inversely correlated with the levels of the PD1 ligand, PDL1, in human lung carcinoma. Thus, PKCθ and its substrate vimentin represent important targets of PD1-mediated T-cell inhibition, and low levels of vimentin phosphorylation may serve as a biomarker for the activation of the PD1 pathway.

Antimelanoma Effects of Alchemilla vulgaris: A Comprehensive In Vitro and In Vivo Study

Due to the rich ethnobotanical and growing evidence-based medicine records, the Alchemillae herba, i.e., the upper parts of the Lady's mantle (Alchemilla vulgaris L.), was used for the assessment of antimelanoma activity. The ethanolic extract of A. vulgaris strongly suppressed the viability of B16F1, B16F10, 518A2, and Fem-X cell lines. In contrast to the in vitro study, where the B16F1 cells were more sensitive to the treatment than the more aggressive counterpart B16F10, the results obtained in vivo using the corresponding syngeneic murine model were quite the opposite. The higher sensitivity of B16F10 tumors in vivo may be attributed to a more complex response to the extract compared to one triggered in vitro. In addition, the strong immunosuppressive microenvironment in the B16F1 model is impaired by the treatment, as evidenced by enhanced antigen-presenting potential of dendritic cells, influx and activity of CD4+ T and CD8+ T lymphocytes, decreased presence of T regulatory lymphocytes, and attenuation of anti-inflammatory cytokine production. All these effects are supported by the absence of systemic toxicity. A. vulgaris extract treatment results in a sustained and enhanced ability to reduce melanoma growth, followed by the restoration of innate and adopted antitumor immunity without affecting the overall physiology of the host.

Soluble immune checkpoints: implications for cancer prognosis and response to immune checkpoint therapy and conventional therapies

Longitudinal sampling of tumor tissue from patients with solid cancers, aside from melanoma and a few other cases, is often unfeasible, and thus may not capture the plasticity of interactions between the tumor and immune system under selective pressure of a given therapy. Peripheral blood analyses provide salient information about the human peripheral immunome while offering technical and practical advantages over traditional tumor biopsies, and should be utilized where possible alongside interrogation of the tumor. Some common blood-based biomarkers used to study the immune response include immune cell subsets, circulating tumor DNA, and protein analytes such as cytokines. With the recent explosion of immune checkpoint inhibitors (ICI) as a modality of treatment in multiple cancer types, soluble immune checkpoints have become a relevant area of investigation for peripheral immune-based biomarkers. However, the exact functions of soluble immune checkpoints and their roles in cancer for the most part remain unclear. This review discusses current literature on the production, function, and expression of nine soluble immune checkpoints - sPD-L1, sPD-1, sCTLA4, sCD80, sTIM3, sLAG3, sB7-H3, sBTLA, and sHVEM - in patients with solid tumors, and explores their role as biomarkers of response to ICI as well as to conventional therapies (chemotherapy, radiotherapy, targeted therapy, and surgery) in cancer patients.

In the Eyes of the Beholder-New Mertk Knockout Mouse and Re-Evaluation of Phagocytosis versus Anti-Inflammatory Functions of MERTK

Greg Lemke's laboratory was one of the pioneers of research into the TAM family of receptor tyrosine kinases (RTKs). Not only was Tyro3 cloned in his laboratory, but his group also extensively studied mice knocked out for individual or various combinations of the TAM RTKs Tyro3, Axl, and Mertk. Here we primarily focus on one of the paralogs-MERTK. We provide a historical perspective on rodent models of loss of Mertk function and their association with retinal degeneration and blindness. We describe later studies employing mouse genetics and the generation of newer knockout models that point out incongruencies with the inference that loss of MERTK-dependent phagocytosis is sufficient for severe, early-onset photoreceptor degeneration in mice. This discussion is meant to raise awareness with regards to the limitations of the original Mertk knockout mouse model generated using 129 derived embryonic stem cells and carrying 129 derived alleles and the role of these alleles in modifying Mertk knockout phenotypes or even displaying Mertk-independent phenotypes. We also suggest molecular approaches that can further Greg Lemke's scintillating legacy of dissecting the molecular functions of MERTK-a protein that has been described to function in phagocytosis as well as in the negative regulation of inflammation.

Advances in Hodgkin Lymphoma Treatment: From Molecular Biology to Clinical Practice

Classical Hodgkin Lymphoma (cHL) is a highly curable disease, but around 20% of patients experience progression or relapse after standard frontline chemotherapy regimens. Salvage regimens followed by autologous stem cell transplants represent the historical treatment approach for these cases. In the last decade, with the increasing understanding of cHL biology and tumor microenvironment role in disease course, novel molecules have been introduced in clinical practice, improving outcomes in the relapsed/refractory setting. The anti-CD30 antibody-drug conjugated brentuximab vedotin and PD-1/PD-L1 checkpoint inhibitors represent nowadays curative options for chemorefractory patients, and randomized trials recently demonstrated their efficacy in frontline immune-chemo-combined modalities. Several drugs able to modulate the patients' T-lymphocytes and NK cell activity are under development, as well as many anti-CD30 chimeric antigen receptor T-cell products. Multiple tumor aberrant epigenetic mechanisms are being investigated as targets for antineoplastic compounds such as histone deacetylase inhibitors and hypomethylating agents. Moreover, JAK2 inhibition combined with anti-PD1 blockade revealed a potential complementary therapeutic pathway in cHL. In this review, we will summarize recent findings on cHL biology and novel treatment options clinically available, as well as promising future perspectives in the field.

Regulatory T cells as crucial trigger and potential target for hyperprogressive disease subsequent to PD-1/PD-L1 blockade for cancer treatment

PD-1/PD-L1 blockade therapy has brought great success to cancer treatment. Nevertheless, limited beneficiary populations and even hyperprogressive disease (HPD) greatly constrain the application of PD-1/PD-L1 inhibitors in clinical treatment. HPD is a special pattern of disease progression with rapid tumor growth and even serious consequences of patient death, which requires urgent attention. Among the many predisposing causes of HPD, regulatory T cells (Tregs) are suspected because they are amplified in cases of HPD. Tregs express PD-1 thus PD-1/PD-L1 blockade therapy may have an impact on Tregs which leads to HPD. Tregs are a subset of CD4+ T cells expressing FoxP3 and play critical roles in suppressing immunity. Tregs migrate toward tumors in the presence of chemokines to suppress antitumor immune responses, causing cancer cells to grow and proliferate. Studies have shown that deleting Tregs could enhance the efficacy of PD-1/PD-L1 blockade therapy and reduce the occurrence of HPD. This suggests that immunotherapy combined with Treg depletion may be an effective means of avoiding HPD. In this review, we summarized the immunosuppressive-related functions of Tregs in antitumor therapy and focused on advances in therapy combining Tregs depletion with PD-1/PD-L1 blockade in clinical studies. Moreover, we provided an outlook on Treg-targeted HPD early warning for PD-1/PD-L1 blockade therapy.

Engineering PD-1-targeted small protein variants for in vitro diagnostics and in vivo PET imaging

BACKGROUND

Programmed cell death 1 (PD-1) belongs to immune checkpoint proteins ensuring negative regulation of the immune response. In non-small cell lung cancer (NSCLC), the sensitivity to treatment with anti-PD-1 therapeutics, and its efficacy, mostly correlated with the increase of tumor infiltrating PD-1+ lymphocytes. Due to solid tumor heterogeneity of PD-1+ populations, novel low molecular weight anti-PD-1 high-affinity diagnostic probes can increase the reliability of expression profiling of PD-1+ tumor infiltrating lymphocytes (TILs) in tumor tissue biopsies and in vivo mapping efficiency using immune-PET imaging.

METHODS

We designed a 13 kDa β-sheet Myomedin scaffold combinatorial library by randomization of 12 mutable residues, and in combination with ribosome display, we identified anti-PD-1 Myomedin variants (MBA ligands) that specifically bound to human and murine PD-1-transfected HEK293T cells and human SUP-T1 cells spontaneously overexpressing cell surface PD-1.

RESULTS

Binding affinity to cell-surface expressed human and murine PD-1 on transfected HEK293T cells was measured by fluorescence with LigandTracer and resulted in the selection of most promising variants MBA066 (hPD-1 KD = 6.9 nM; mPD-1 KD = 40.5 nM), MBA197 (hPD-1 KD = 29.7 nM; mPD-1 KD = 21.4 nM) and MBA414 (hPD-1 KD = 8.6 nM; mPD-1 KD = 2.4 nM). The potential of MBA proteins for imaging of PD-1+ populations in vivo was demonstrated using deferoxamine-conjugated MBA labeled with 68Galium isotope. Radiochemical purity of 68Ga-MBA proteins reached values 94.7-99.3% and in vitro stability in human serum after 120 min was in the range 94.6-98.2%. The distribution of 68Ga-MBA proteins in mice was monitored using whole-body positron emission tomography combined with computerized tomography (PET/CT) imaging up to 90 min post-injection and post mortem examined in 12 mouse organs. The specificity of MBA proteins was proven by co-staining frozen sections of human tonsils and NSCLC tissue biopsies with anti-PD-1 antibody, and demonstrated their potential for mapping PD-1+ populations in solid tumors.

CONCLUSIONS

Using directed evolution, we developed a unique set of small binding proteins that can improve PD-1 diagnostics in vitro as well as in vivo using PET/CT imaging.

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.

Immunotherapeutic implications of negative regulation by protein tyrosine phosphatases in T cells: the emerging cases of PTP1B and TCPTP

In the context of inflammation, T cell activation occurs by the concerted signals of the T cell receptor (TCR), co-stimulatory receptors ligation, and a pro-inflammatory cytokine microenvironment. Fine-tuning these signals is crucial to maintain T cell homeostasis and prevent self-reactivity while offering protection against infectious diseases and cancer. Recent developments in understanding the complex crosstalk between the molecular events controlling T cell activation and the balancing regulatory cues offer novel approaches for the development of T cell-based immunotherapies. Among the complex regulatory processes, the balance between protein tyrosine kinases (PTK) and the protein tyrosine phosphatases (PTPs) controls the transcriptional and metabolic programs that determine T cell function, fate decision, and activation. In those, PTPs are de facto regulators of signaling in T cells acting for the most part as negative regulators of the canonical TCR pathway, costimulatory molecules such as CD28, and cytokine signaling. In this review, we examine the function of two close PTP homologs, PTP1B (PTPN1) and T-cell PTP (TCPTP; PTPN2), which have been recently identified as promising candidates for novel T-cell immunotherapeutic approaches. Herein, we focus on recent studies that examine the known contributions of these PTPs to T-cell development, homeostasis, and T-cell-mediated immunity. Additionally, we describe the signaling networks that underscored the ability of TCPTP and PTP1B, either individually and notably in combination, to attenuate TCR and JAK/STAT signals affecting T cell responses. Thus, we anticipate that uncovering the role of these two PTPs in T-cell biology may lead to new treatment strategies in the field of cancer immunotherapy. This review concludes by exploring the impacts and risks that pharmacological inhibition of these PTP enzymes offers as a therapeutic approach in T-cell-based immunotherapies.

Discovery of a novel SHP2 allosteric inhibitor using virtual screening, FMO calculation, and molecular dynamic simulation

CONTEXT

SHP2 is a non-receptor protein tyrosine phosphatase to remove tyrosine phosphorylation. Functionally, SHP2 is an essential bridge to connect numerous oncogenic cell-signaling cascades including RAS-ERK, PI3K-AKT, JAK-STAT, and PD-1/PD-L1 pathways. This study aims to discover novel and potent SHP2 inhibitors using a hierarchical structure-based virtual screening strategy that combines molecular docking and the fragment molecular orbital method (FMO) for calculating binding affinity (referred to as the Dock-FMO protocol). For the SHP2 target, the FMO method prediction has a high correlation between the binding affinity of the protein-ligand interaction and experimental values (R2 = 0.55), demonstrating a significant advantage over the MM/PBSA (R2 = 0.02) and MM/GBSA (R2 = 0.15) methods. Therefore, we employed Dock-FMO virtual screening of ChemDiv database of ∼2,990,000 compounds to identify a novel SHP2 allosteric inhibitor bearing hydroxyimino acetamide scaffold. Experimental validation demonstrated that the new compound (E)-2-(hydroxyimino)-2-phenyl-N-(piperidin-4-ylmethyl)acetamide (7188-0011) effectively inhibited SHP2 in a dose-dependent manner. Molecular dynamics (MD) simulation analysis revealed the binding stability of compound 7188-0011 and the SHP2 protein, along with the key interacting residues in the allosteric binding site. Overall, our work has identified a novel and promising allosteric inhibitor that targets SHP2, providing a new starting point for further optimization to develop more potent inhibitors.

METHODS

All the molecular docking studies were employed to identify potential leads with Maestro v10.1. The protein-ligand binding affinities of potential leads were further predicted by FMO calculations at MP2/6-31G* level using GAMESS v2020 system. MD simulations were carried out with AmberTools18 by applying the FF14SB force field. MD trajectories were analyzed using VMD v1.9.3. MM/GB(PB)SA binding free energy analysis was carried out with the mmpbsa.py tool of AmberTools18. The docking and MD simulation results were visualized through PyMOL v2.5.0.

Inhibitory CARs fail to protect from immediate T cell cytotoxicity

Chimeric antigen receptors (CARs) equipped with an inhibitory signaling domain (iCARs) have been proposed as strategy to increase on-tumor specificity of CAR-T cell therapies. iCARs inhibit T cell activation upon antigen recognition and thereby program a Boolean NOT gate within the CAR-T cell. If cancer cells do not express the iCAR target antigen while it is highly expressed on healthy tissue, CAR/iCAR coexpressing T cells are supposed to kill cancer cells but not healthy cells expressing the CAR antigen. In this study, we employed a well-established reporter cell system to demonstrate high potency of iCAR constructs harboring BTLA-derived signaling domains. We then created CAR/iCAR combinations for the clinically relevant antigen pairs B7-H3/CD45 and CD123/CD19 and show potent reporter cell suppression by iCARs targeting CD45 or CD19. In primary human T cells αCD19-iCARs were capable of suppressing T cell proliferation and cytokine production. Surprisingly, the iCAR failed to veto immediate CAR-mediated cytotoxicity. Likewise, T cells overexpressing PD-1 or BTLA did not show impaired cytotoxicity toward ligand-expressing target cells, indicating that inhibitory signaling by these receptors does not mediate protection against cytotoxicity by CAR-T cells. Future approaches employing iCAR-equipped CAR-T cells for cancer therapy should therefore monitor off-tumor reactivity and potential CAR/iCAR-T cell dysfunction.

Anti-PD-1 treatment protects against seizure by suppressing sodium channel function

AIMS

Although programmed cell death protein 1 (PD-1) typically serves as a target for immunotherapies, a few recent studies have found that PD-1 is expressed in the nervous system and that neuronal PD-1 might play a crucial role in regulating neuronal excitability. However, whether brain-localized PD-1 is involved in seizures and epileptogenesis is still unknown and worthy of in-depth exploration.

METHODS

The existence of PD-1 in human neurons was confirmed by immunohistochemistry, and PD-1 expression levels were measured by real-time quantitative PCR (RT-qPCR) and western blotting. Chemoconvulsants, pentylenetetrazol (PTZ) and cyclothiazide (CTZ), were applied for the establishment of in vivo (rodents) and in vitro (primary hippocampal neurons) models of seizure, respectively. SHR-1210 (a PD-1 monoclonal antibody) and sodium stibogluconate (SSG, a validated inhibitor of SH2-containing protein tyrosine phosphatase-1 [SHP-1]) were administrated to investigate the impact of PD-1 pathway blockade on epileptic behaviors of rodents and epileptiform discharges of neurons. A miRNA strategy was applied to determine the impact of PD-1 knockdown on neuronal excitability. The electrical activities and sodium channel function of neurons were determined by whole-cell patch-clamp recordings. The interaction between PD-1 and α-6 subunit of human voltage-gated sodium channel (Nav1.6) was validated by performing co-immunostaining and co-immunoprecipitation (co-IP) experiments.

RESULTS

Our results reveal that PD-1 protein and mRNA levels were upregulated in lesion cores compared with perifocal tissues of surgically resected specimens from patients with intractable epilepsy. Furthermore, we show that anti-PD-1 treatment has anti-seizure effects both in vivo and in vitro. Then, we reveal that PD-1 blockade can alter the electrophysiological properties of sodium channels. Moreover, we reveal that PD-1 acts together with downstream SHP-1 to regulate sodium channel function and hence neuronal excitability. Further investigation suggests that there is a direct interaction between neuronal PD-1 and Nav1.6.

CONCLUSION

Our study reveals that neuronal PD-1 plays an important role in epilepsy and that anti-PD-1 treatment protects against seizures by suppressing sodium channel function, identifying anti-PD-1 treatment as a novel therapeutic strategy for epilepsy.

PD-1-mediated inhibition of T cell activation: Mechanisms and strategies for cancer combination immunotherapy

The programmed cell death 1 (PD-1) immune checkpoint of co-inhibitory signaling plays crucial roles in controlling the magnitude and duration of T cell activation to limit tissue damage and maintain self-tolerance. Cancer cells hijack the co-inhibitory pathway and escape immune surveillance by overexpressing the PD-1 ligand PD-L1. Immune checkpoint inhibitors, such as PD-1 blocking antibody have been approved for tumor immunotherapy. However, not all patients can benefit from PD-1 monotherapy. Combination immunotherapy based on PD-1 axis blockade substantially improves clinical anti-tumor efficacy. In this review, we briefly summarize the current progress on the mechanisms of PD-1-mediated inhibition of T cell activation and strategies for cancer combination immunotherapy.

Targeting inflammation as cancer therapy

Inflammation has accompanied human beings since the emergence of wounds and infections. In the past decades, numerous efforts have been undertaken to explore the potential role of inflammation in cancer, from tumor development, invasion, and metastasis to the resistance of tumors to treatment. Inflammation-targeted agents not only demonstrate the potential to suppress cancer development, but also to improve the efficacy of other therapeutic modalities. In this review, we describe the highly dynamic and complex inflammatory tumor microenvironment, with discussion on key inflammation mediators in cancer including inflammatory cells, inflammatory cytokines, and their downstream intracellular pathways. In addition, we especially address the role of inflammation in cancer development and highlight the action mechanisms of inflammation-targeted therapies in antitumor response. Finally, we summarize the results from both preclinical and clinical studies up to date to illustrate the translation potential of inflammation-targeted therapies.

PD-1 Limits IL-2 Production and Thymic Regulatory T Cell Development

Inhibitory proteins, such as programmed cell death protein 1 (PD-1), have been studied extensively in peripheral T cell responses to foreign Ags, self-Ags, and neoantigens. Notably, these proteins are first expressed during T cell development in the thymus. Reports suggest that PD-1 limits regulatory T cell (Treg) development, but the mechanism by which PD-1 exerts this function remains unknown. The present study expands the evaluation of murine PD-1 and its ligands in the thymus, demonstrating that some of the highest expressers of PD-1 and programmed death-ligand 1 are agonist selected cells. Surprisingly, we reveal a selective role for PD-1 in regulating the developmental niche only for Tregs because other agonist selected cell populations, such as NK T cells, remain unchanged. We also ruled out PD-1 as a regulator of proliferation or cell death of agonist selected Tregs and further demonstrated that PD-1-deficient Tregs have reduced TCR signaling. Unexpectedly, the data suggest that PD-1-deficient thymocytes produce elevated levels of IL-2, a Treg niche-limiting cytokine. Collectively, these data suggest a novel role for PD-1 in regulating IL-2 production and the concurrent agonist selection of murine thymic Tregs. This observation has implications for the use of checkpoint blockade in the context of cancer and infection.

B Cell Subsets and Immune Checkpoint Expression in Patients with Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is characterized by dysfunctional B cells. Immune checkpoint molecules such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death-1 (PD-1) are upregulated in patients with CLL and may correlate with prognostic markers such as beta-2 microglobulin (B2M). The aim of this study was to evaluate the levels of immune checkpoints on B cell subsets and to further correlate them with B2M levels in patients with CLL. We recruited 21 patients with CLL and 12 controls. B cell subsets and the levels of immune checkpoint expression were determined using conventional multi-color flow cytometry. Basal levels of B2M in patients with CLL were measured using an enzyme-linked immunosorbent assay. Patients with CLL had increased levels of activated B cells when compared to the control group, p < 0.001. The expression of PD-1 and CTLA-4 were increased on activated B cells and memory B cells, p < 0.05. There were no associations between B2M levels and the measured immune checkpoints on B cell subsets, after adjusting for sex and age. In our cohort, the patients with CLL expressed elevated levels of PD-1 and CTLA-4 immune checkpoints on activated and memory B cell subsets. However, there was no correlation between these immune checkpoint expressions and B2M levels.