STT3-dependent PD-L1 accumulation on cancer stem cells promotes immune evasion. Nat Commun. 2018;9:1908. [PMID: 29765039 PMCID: PMC5954021 DOI: 10.1038/s41467-018-04313-6]

A mitochondria-interfering nanocomplex cooperates with photodynamic therapy to boost antitumor immunity

Immunotherapeutics against triple-negative breast cancer (TNBC) hold great promise. In this work, we provide a combination therapy for simultaneous increasing tumor immunogenicity and down-regulating programmed cell death ligand 1 (PD-L1) to boost antitumor immunity in TNBC. We prepare bis (diethyldithiocarbamate)-copper/indocyanine green nanoparticles (CuET/ICG NPs) simply in aqueous with one-pot method. CuET/ICG NPs interfere mitochondria, reduce oxygen consumption, and alleviate tumor hypoxia to potentiate photodynamic therapy (PDT) for amplifying immunogenic cell death (ICD). Meanwhile, mitochondria dysfunction leads to energy stress and activates AMPK pathway. As a result, CuET/ICG NPs downregulates membrane PD-L1 (mPD-L1) on both 4T1 cancer cells and cancer stem cells (CSCs) through AMP-activated protein kinase (AMPK)-mediated pathway in hypoxia. Cooperatively, the combinational therapy activates antitumor immunity and triggers long lasting immune memory response to resist tumor re-challenge. Our study represents an attempt that conquers tumor immunosuppressive microenvironment with simple biomedical materials and multimodality treatments.

Sugar symphony: glycosylation in cancer metabolism and stemness

Glycosylation is a complex co-translational and post-translational modification (PTM) in eukaryotes that utilizes glycosyltransferases to generate a vast array of glycoconjugate structures. Recent studies have highlighted the role of glycans in regulating essential molecular, cellular, tissue, organ, and systemic biological processes with significant implications for human diseases, particularly cancer. The metabolic reliance of cancer, spanning tumor initiation, disease progression, and resistance to therapy, necessitates a range of uniquely altered cellular metabolic pathways. In addition, the intricate interplay between cell-intrinsic and -extrinsic mechanisms is exemplified by the communication between cancer cells, cancer stem cells (CSCs), cancer-associated fibroblasts (CAFs), and immune cells within the tumor microenvironment (TME). In this review article, we explore how differential glycosylation in cancer influences the metabolism and stemness features alongside new avenues in glycobiology.

TBB inhibits CK2/PD-L1/EGFR pathway-mediated tumor progression

The expression of PD-L1 on cancer cells facilitates tumor immune escape by binding to PD-1 on T cells, thereby inhibiting T cell activity. However, the role of intracellular PD-L1 signaling in tumor progression remains unclear. In this study, we demonstrate that CK2 induces PD-L1 phosphorylation at Thr-285, which enhances PD-L1 protein stability. This phosphorylation disrupts the interaction between LC3B and PD-L1, inhibiting PD-L1 degradation via autophagy. Furthermore, PD-L1-T285 phosphorylation promotes EGFR binding to PD-L1, leading to activation of EGFR downstream signaling. This activation drives non-small cell lung cancer (NSCLC) cell proliferation, migration, invasion, and tumor growth. Conversely, CK2 depletion or treatment with a CK2 inhibitor reversed these effects. Our findings reveal a novel mechanism by which the CK2/PD-L1/EGFR pathway promotes tumor progression.

Carvedilol sensitizes chemotherapy by targeting STING to boost anti-tumor immunity

The stimulator of interferon genes (STING)-mediated type I interferon (IFN) response is critical for mounting anti-tumor immunity and sensitizing chemotherapy by remodeling the tumor immune microenvironment. However, no clinically available drugs have been applied for STING activation. Based on high-throughput screening of small-molecule microarrays, we found that carvedilol, an adrenergic receptor blocker used to treat essential hypertension and symptomatic heart failure, is a STING activator. Mechanistically, carvedilol interacts with STING at threonine 263 and enhances its dimerization. Importantly, carvedilol enhances the therapeutic effect of etoposide in both the allografted tumor model and patient-derived tumor-like cell clusters (PTCs) by promoting etoposide-induced STING activation. Our findings identify carvedilol as a STING activator and provide a theoretical basis for combining carvedilol and etoposide in cancer therapy.

A nanobody-enzyme fusion protein targeting PD-L1 and sialic acid exerts anti-tumor effects by C-type lectin pathway-mediated tumor associated macrophages repolarizing

Aberrant sialylated glycosylation in the tumor microenvironment is a novel immune suppression pathway, which has garnered significant attention as a targetable glycoimmune checkpoint for cancer immunotherapy to address the dilemma of existing therapies. However, rational drug design and in-depth mechanistic studies are urgently required for tumor sialic acid to become valuable glycoimmune targets. In this study, we explored the positive correlation of PD-L1 and sialyltransferase expression in clinical colorectal cancer tissues and identified their mutual regulation effects in macrophages. Subsequently, we characterized a new sialidase with excellent properties from human oral symbiotic bacteria and then developed a novel nanobody-enzyme fusion protein, designated as Nb16-Sia, to concurrently target the PD-L1 and sialic acid. Results from syngeneic colon tumor models reveal superior efficacy of Nb16-Sia over monotherapy and combinations, which could remodel the tumor immune microenvironment. Mechanistically, Nb16-Sia, which could repolarize macrophages from the tumor-promoting M2 to anti-tumor M1 phenotype via the C-type lectin pathway, exerted its antitumor efficacy mainly by regulating tumor-associated macrophages. Our strategy of nanobody-enzyme fusion protein effectively enables the delivery of sialidase, allows the collaboration between anti-PD-L1 nanobody and sialidase in combating tumors, and holds considerable promise for further development.

Glycosylation editing: an innovative therapeutic opportunity in precision oncology

Cancer is still one of the most arduous challenges in the human society, even though humans have found many ways to try to conquer it. With our incremental understandings on the impact of sugar on human health, the clinical relevance of glycosylation has attracted our attention. The fact that altered glycosylation profiles reflect and define different health statuses provide novel opportunities for cancer diagnosis and therapeutics. By reviewing the mechanisms and critical enzymes involved in protein, lipid and glycosylation, as well as current use of glycosylation for cancer diagnosis and therapeutics, we identify the pivotal connection between glycosylation and cellular redox status and, correspondingly, propose the use of redox modulatory tools such as cold atmospheric plasma (CAP) in cancer control via glycosylation editing. This paper interrogates the clinical relevance of glycosylation on cancer and has the promise to provide new ideas for laboratory practice of cold atmospheric plasma (CAP) and precision oncology therapy.

Modulation of N-glycosylation in the PD-1: PD-L1 axis as a strategy to enhance cancer immunotherapies

The modulation of the N-glycosylation status in immune checkpoints, particularly the PD-1/PD-L1 axis, has emerged as a promising approach to enhance cancer immunotherapies. While immune checkpoint inhibitors (ICIs) targeting PD-1 and PD-L1 have achieved significant clinical success, recent studies highlight the critical role of N-glycosylation in regulating their expression, stability, and function. Alterations in N-glycosylation might affect the efficacy of ICIs by modulating the interactions between immune checkpoints and antibodies used in therapy. This review focuses on the glycosylation of PD-1 and its ligands PD-L1 and PD-L2, examining how N-glycans influence immune responses and contribute to immune evasion by tumors. It explores innovative strategies to modulate glycosylation in tumor and immune cells, including the use of N-glycosylation inhibitors and novel genetic manipulation techniques. Understanding the interplay between N-glycosylation and immune checkpoint functions is essential for optimizing immunotherapy outcomes and overcoming therapeutic resistance in cancer patients.

The multifaceted role of CS1 (SLAMF7) in immunoregulation: Implications for cancer therapy and autoimmune disorders

CS1 (SLAMF7), a pivotal immune receptor, plays a dual role in modulating immune responses in autoimmune diseases and cancer. In autoimmunity, aberrant CS1 signaling contributes to the activation of autoreactive lymphocytes, driving pathologies such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Conversely, in oncology, CS1 serves as a promising immunotherapeutic target, exemplified by the efficacy of the monoclonal antibody Elotuzumab in multiple myeloma. CS1 mediates immune cell functions through intricate signaling pathways, including interactions with EAT-2 and SAP adaptors, which influence cytotoxicity, cytokine production, and immune homeostasis. Beyond cancer and autoimmune diseases, soluble and membrane-bound forms of CS1 are emerging as biomarkers and potential therapeutic targets. Despite significant progress, gaps remain in understanding CS1\u2019s mechanisms, variability in expression, and role in other diseases. This study explores the multifaceted functions of CS1, proposing innovative strategies to leverage its therapeutic potential across diverse pathologies.

In-silico analysis unveiling the role of cancer stem cells in immunotherapy resistance of immune checkpoint-high pancreatic adenocarcinoma

Although immune checkpoint (IC) inhibition is a major treatment modality in cancer-immunotherapy, multiple cancers show low response. Our in-silico exploration by mining cancer datasets using R2, available clinical trial data, and Kaplan-Meier analysis from GEPIA depicted that unlike low-responder (LR) cancers, high-responder (HR) cancers furnish higher IC expression, that upon lowering may provide better prognosis. Contrastingly, pancreatic adenocarcinoma (PAAD) demonstrated high IC expression but low immunotherapy-response. Infiltration scores from TIMER2.0 revealed higher pro-tumor immune subsets and cancer-associated fibroblasts (CAFs) while depicting lower anti-tumor immune subsets in PAAD as compared to HR lung adenocarcinoma (LUAD). Additionally, bioinformatic tool cBioportal showed lesser tumor mutational burden, mismatch repair deficiency and greater percent of driver mutations in TP53, KRAS and CDKN2A in PAAD, supporting its higher immunotherapy-resistance than LUAD. Our search for the 'key' immunotherapy response-deciding factor(s) revealed cancer stem cells (CSCs), the known contributors of therapy-resistance and immuno-evasion, to be positively correlated with above-mentioned driver mutations, pro-tumor immune and CAF subsets; and that PAAD furnished higher expression of CSC genes than LUAD. UMAP/tSNE analyses revealed that high CSC signature is positively correlated with immunotherapy-resistance genes and pro-cancer immune cells, while negatively with cytotoxic-T cells in PAAD. Our in-silico study explains the low immunotherapy-response in high IC-expressing PAAD, wherein CSC plays a pivotal role. Further exploration portrayed correlation of CSCs with immunotherapy-resistance in other LR and HR cancers too, substantiating the need for personalized CSC evaluation and targeting for successful immunotherapy outcomes.

Unraveling the triad of hypoxia, cancer cell stemness, and drug resistance

In the domain of addressing cancer resistance, challenges such as limited effectiveness and treatment resistance remain persistent. Hypoxia is a key feature of solid tumors and is strongly associated with poor prognosis in cancer patients. Another significant portion of the development of acquired drug resistance is attributed to tumor stemness. Cancer stem cells (CSCs), a small tumor cell subset with self-renewal and proliferative abilities, are crucial for tumor initiation, metastasis, and intra-tumoral heterogeneity. Studies have shown a significant association between hypoxia and CSCs in the context of tumor resistance. Recent studies reveal a strong link between hypoxia and tumor stemness, which together promote tumor survival and progression during treatment. This review elucidates the interplay between hypoxia and CSCs, as well as their correlation with resistance to therapeutic drugs. Targeting pivotal genes associated with hypoxia and stemness holds promise for the development of novel therapeutics to combat tumor resistance.

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.

Capsanthin inhibits migration and reduces N-linked glycosylation of PD-L1 via the EZH2-PD-L1 axis in triple-negative breast cancer brain metastasis

Breast cancer metastasis to the brain, occurring in about 15-25% of cases, represents a major obstacle in the treatment of triple-negative breast cancer (TNBC). The molecular mechanisms driving this form of metastasis are still largely unknown. PD-L1, an immune checkpoint protein, is central to tumor immune evasion and has become a focus for immunotherapy development. While PD-L1 inhibitors have shown success in various cancer types, their effectiveness in TNBC brain metastases remains to be fully investigated. This highlights the urgent need to understand the complex interactions between metastatic brain tumors and the tumor microenvironment in TNBC patients. Gaining insights into these dynamics is crucial for developing new targeted therapies, including those that modulate the PD-L1 pathway, to better manage and treat TNBC brain metastases. We explore the impact of Capsanthin on the tumor microenvironment of brain metastases in triple-negative breast cancer (TNBC). Our results reveal that Capsanthin effectively inhibits the migration of brain metastasis TNBC cells. Furthermore, Capsanthin significantly reduces the expression of EZH2 and N-linked glycosylated PD-L1 proteins and mRNA in TNBC cells, encompassing both primary and metastatic sites, as well as in mesenchymal stem cells (3A6). Data from The Cancer Genome Atlas (TCGA) indicate that elevated expression levels of EZH2 correlate with poorer patient prognosis. Immunoprecipitation assays demonstrate a direct interaction between EZH2 and PD-L1 in brain metastases of TNBC, underscoring the pivotal role of the EZH2-PD-L1 axis. Additionally, Capsanthin was found to suppress the expression of epithelial-mesenchymal transition (EMT) markers in metastatic brain TNBC cells and mesenchymal stem cells. Our results suggest that Capsanthin can modulate the tumor microenvironment and inhibit key pathways involved in cancer progression, offering potential therapeutic benefits for patients with TNBC brain metastases.

Regulation of PD-L1 glycosylation and advances in cancer immunotherapy

Protein glycosylation plays a versatile role in regulating homeostasis, such as cell migration, protein sorting, and the immune response. Drugs aimed at targeting glycosylation have strong implications for immunity enhancement, diagnosis, and cancer regression. Programmed death-ligand 1 (PD-L1), expressed in cancer or antigen-presenting cells, binds to programmed cell death protein 1 (PD-1) and suppresses T cells. Glycosylation of PD-L1 at N35, N192, N200, and N219 stabilizes PD-L1 on the cancer cell surface, which contributes to immune evasion by inhibiting T cell activity. To date, at least six glycosyltransferases and four associate proteins are known to regulate PD-L1 glycosylation. Terminal modifications such as poly-N-acetyl-lactosamine (poly-LacNAC), sulfation, and sialylation are commonly found on PD-L1, acting as an immune recognition ligand and regulating certain immune responses. Studies have identified many mechanisms and potential therapeutic targets within the glycosylation pathways of PD-L1, revealing their involvement in cancer pathology, immune evasion, and resistance to immunotherapy. In this review, we covered the glycoforms, terminal moiety, binding lectin, glycosyltransferase, as well as sugar analogs focusing on glycosylated PD-L1. We present a mechanism that originates from the endoplasmic reticulum (ER)-Golgi apparatus (Golgi) and its subsequent translocation to the cell membrane. This pathway determines the immune suppression function of PD-L1 and therefore regulates the immune response such as T cells, monocytes, and macrophages. This collection of findings underscores the significance of glycosylation in the role of PD-L1 in cancer and highlights multiple potential targets and strategies for improving therapeutic intervention and diagnostic techniques.

Cancer stem cells and niches: challenges in immunotherapy resistance

Cancer stem cells (CSCs) are central to tumor progression, metastasis, immune evasion, and therapeutic resistance. Characterized by remarkable self-renewal and adaptability, CSCs can transition dynamically between stem-like and differentiated states in response to external stimuli, a process termed "CSC plasticity." This adaptability underpins their resilience to therapies, including immune checkpoint inhibitors and adoptive cell therapies (ACT). Beyond intrinsic properties, CSCs reside in a specialized microenvironment-the CSC niche-which provides immune-privileged protection, sustains their stemness, and fosters immune suppression. This review highlights the critical role of CSCs and their niche in driving immunotherapy resistance, emphasizing the need for integrative approaches to overcome these challenges.

Phytochemical synergies in BK002: advanced molecular docking insights for targeted prostate cancer therapy

Achyranthes japonica (Miq.) Nakai (AJN) and Melandrium firmum (Siebold and Zucc.) Rohrb. (MFR) are medicinal plants recognized for their bioactive phytochemicals, including ecdysteroids, anthraquinones, and flavonoids. This study investigates the anticancer properties of key constituents of these plants, focusing on the BK002 formulation, a novel combination of AJN and MFR. Specifically, the research employs advanced molecular docking and in silico analyses to assess the interactions of bioactive compounds ecdysterone, inokosterone, and 20-hydroxyecdysone (20-HE) with key prostate cancer-related network proteins, including 5α-reductase, CYP17, DNMT1, Dicer, PD-1, and PD-L1. Molecular docking techniques were applied to evaluate the binding affinities contributions of the bioactive compounds in BK002 against prostate cancer-hub network targets. The primary focus was on enzymes like 5α-reductase and CYP17, which are central to androgen biosynthesis, as well as on cancer-related proteins such as DNA methyltransferase 1 (DNMT1), Dicer, programmed death-1 (PD-1), and programmed death ligand-1 (PD-L1). Based on data from prostate cancer patients, key target networks were identified, followed by in silico analysis of the primary bioactive components of BK002.In silico assessments were conducted to evaluate the safety profiles of these compounds, providing insights into their therapeutic potential. The docking studies revealed that ecdysterone, inokosterone, and 20-hydroxyecdysonec demonstrated strong binding affinities to the critical prostate cancer-related enzymes 5α-reductase and CYP17, contributing to a potential reduction in androgenic activity. These compounds also exhibited significant inhibitory interactions with DNMT1, Dicer, PD-1, and PD-L1, suggesting a capacity to interfere with key oncogenic and immune evasion pathways. Ecdysterone, inokosterone, and 20-hydroxyecdysone have demonstrated the ability to target key oncogenic pathways, and their favorable binding affinity profiles further underscore their potential as novel therapeutic agents for prostate cancer. These findings provide a strong rationale for further preclinical and clinical investigations, supporting the integration of BK002 into therapeutic regimens aimed at modulating tumor progression and immune responses.

Breaking Immunosuppression to Enhance Cancer Stem Cell-Targeted Immunotherapy

Cancer stem cell (CSC)-targeted immunotherapy has emerged as a novel strategy in cancer treatment in the past decade. However, its efficacy is significantly limited due to the existence of host immune suppressive activity. Specifically, programmed cell death ligand-1 (PD-L1) is overexpressed in CSCs, and PD-L1 overexpressed CSCs create immunosuppressive milieu via interacting with various immune cells in tumor microenvironments (TME). Hence, novel immunotherapeutic strategies targeting CSCs with concurrent immunosuppression interruption will be promising in enhancing anti-CSC effects. These include dendritic cell (DC) and nanodisc (ND)-based vaccines to present CSC antigens in the forms of CSC lysate, CSC-marker proteins, and CSC-derived peptides to induce anti-CSC immunity. In addition, CSC-directed bispecific antibodies (BiAbs) and antibody drug conjugates (ADCs) have been developed to target CSCs effectively. Furthermore, chimeric antigen receptor (CAR)-T cell therapy and natural killer (NK) cell-based therapy targeting CSCs have achieved progress in both solid and hematologic tumors, and inhibition of CSC associated signaling pathways has proven successful. In this review, we aimed to outline the roles and regulatory mechanisms of PD-L1 in the properties of CSCs; the crosstalk between CSCs and immunosuppressive cells in TME, and recent progress and future promises of immunosuppression blockage to enhance CSC-targeted immunotherapy.

Cancer stem cells and tumor-associated macrophages as mates in tumor progression: mechanisms of crosstalk and advanced bioinformatic tools to dissect their phenotypes and interaction

Cancer stem cells (CSCs) are a small subset within the tumor mass significantly contributing to cancer progression through dysregulation of various oncogenic pathways, driving tumor growth, chemoresistance and metastasis formation. The aggressive behavior of CSCs is guided by several intracellular signaling pathways such as WNT, NF-kappa-B, NOTCH, Hedgehog, JAK-STAT, PI3K/AKT1/MTOR, TGF/SMAD, PPAR and MAPK kinases, as well as extracellular vesicles such as exosomes, and extracellular signaling molecules such as cytokines, chemokines, pro-angiogenetic and growth factors, which finely regulate CSC phenotype. In this scenario, tumor microenvironment (TME) is a key player in the establishment of a permissive tumor niche, where CSCs engage in intricate communications with diverse immune cells. The "oncogenic" immune cells are mainly represented by B and T lymphocytes, NK cells, and dendritic cells. Among immune cells, macrophages exhibit a more plastic and adaptable phenotype due to their different subpopulations, which are characterized by both immunosuppressive and inflammatory phenotypes. Specifically, tumor-associated macrophages (TAMs) create an immunosuppressive milieu through the production of a plethora of paracrine factors (IL-6, IL-12, TNF-alpha, TGF-beta, CCL1, CCL18) promoting the acquisition by CSCs of a stem-like, invasive and metastatic phenotype. TAMs have demonstrated the ability to communicate with CSCs via direct ligand/receptor (such as CD90/CD11b, LSECtin/BTN3A3, EPHA4/Ephrin) interaction. On the other hand, CSCs exhibited their capacity to influence immune cells, creating a favorable microenvironment for cancer progression. Interestingly, the bidirectional influence of CSCs and TME leads to an epigenetic reprogramming which sustains malignant transformation. Nowadays, the integration of biological and computational data obtained by cutting-edge technologies (single-cell RNA sequencing, spatial transcriptomics, trajectory analysis) has significantly improved the comprehension of the biunivocal multicellular dialogue, providing a comprehensive view of the heterogeneity and dynamics of CSCs, and uncovering alternative mechanisms of immune evasion and therapeutic resistance. Moreover, the combination of biology and computational data will lead to the development of innovative target therapies dampening CSC-TME interaction. Here, we aim to elucidate the most recent insights on CSCs biology and their complex interactions with TME immune cells, specifically TAMs, tracing an exhaustive scenario from the primary tumor to metastasis formation.

Secreted PD-L1 alleviates inflammatory arthritis in mice through local and systemic AAV gene therapy

Introduction

Rheumatoid arthritis (RA) primarily affects the joints but can also affect multiple organs and profoundly impacts patients' ability to carry out daily activities, mental health, and life expectancy. Current treatments for RA are limited in terms of duration, efficacy, and adverse effects. PD-L1 is a checkpoint protein that plays important roles in immune regulation and has been implicated in the initiation and progression of multiple autoimmune diseases.

Method

In a previous study, we demonstrated that intra-articular injection with adeno-associated virus (AAV) vectors encoding wild type PD-L1 improved local inflammation in the joint in the collagen-induced arthritis (CIA) mouse model of RA. To further improve efficacy, we explored AAV-mediated delivery of the soluble PD-L1 (sPD-L1) to CIA mice.

Result

After intra-articular injection of AAV6 vectors expressing the optimal isoform of sPD-L1 (shPD-L1), more potency was observed when compared to wild type PD-L1, with a lower dose of AAV6/shPD-L1 needed for arthritis improvement. To study the therapeutic effect of systemic expression of sPD-L1, we administered AAV8/shPD-L1 gene therapy in CIA mice via retro-orbital injection and found significant improvements in joint inflammation and paw swelling, exhibiting similar phenotypes to that in naïve mice. The levels of total immunoglobulin and anti-collagen specific antibodies were lower in AAV8/shPD-L1 treated CIA mice than those in controls. The levels of pro-inflammatory cytokines in blood were also significantly decreased in shPD-L1 treated mice. Additionally, T cell apoptosis rates in the spleen showed a 2-fold increase in treated mice. Finally, we investigated the therapeutic effect of AAV/shPD-L1 via intramuscular injection. After injection of AAV6/shPD-L1, decreased paw swelling, reduced joint inflammation, and lower levels of pro-inflammatory cytokines in blood were achieved. The therapeutic effect of shPD-L1 was dose dependent via intramuscular treatment with AAV vectors.

Conclusion

In conclusion, the findings in this study suggest that intra-articular injection of AAV vectors encoding sPD-L1 results in greater therapeutic benefit on arthritis, and systemic AAV/sPD-L1 is able to block the development of inflammatory arthritis with inhibition of the systemic immune response, underlining the potential of gene therapy with systemic delivery of shPD-L1 via AAV vectors in RA.

Stigmasterol Attenuates Triple-negative Breast Cancer Stem Cell Properties by Inhibiting JAK3

Background: Breast cancer stem-like cells (BCSCs) are considered a source of tumor origins, metastasis and drug resistance, thereby limiting current treatment regimens. Stigmasterol has been reported to inhibit various cancer processes, but its effects and mechanisms in BCSCs have not been investigated. Methods: To generate spheroids, we enriched parental and SUM159 cells with BCSCs in a serum-free medium. The effects on the stemness, metastasis and drug resistance of CSC-enriched SUM159 cells were detected for the first time by in vivo and in vitro experiments. Results: CSC-enriched SUM159 and 4T1 cells demonstrated higher potential for tumorigenesis and metastasis. Stigmasterol suppresses BCSCs' spheroid formation, cell viability, and migration ability and promotes cell apoptosis. Stigmasterol also inhibited BCSCs-originated cancer formation in rat models. Stigmasterol also attenuated the growth of TNBC organoids from human breast cancer tissues. These data revealed the inhibitory effects of stigmasterol on BCSC traits. In the meantime, we found that JAK3 was upregulated in BCSCs, and Stigmasterol could effectively inhibit its expression. In addition, JAK3 was evidenced to negatively regulate BCSC activity and stemness both in vitro and in vivo. More importantly, the results indicated that Stigmasterol suppresses BCSC activity by inhibiting JAK3 expression. Conclusion: This study is the first to demonstrate that Stigmasterol inhibited metastasis and stemness of BCSCs by downregulating JAK3, which might provide a new method for the clinical application of Stigmasterol in breast cancer.

A novel allosteric driver mutation of β-glucuronidase promotes head and neck squamous cell carcinoma progression through STT3B-mediated PD-L1 N-glycosylation

Head and neck squamous cell carcinoma (HNSCC) develops and advances because of the accumulation of somatic mutations located in orthosteric and allosteric areas. However, the biological effects of allosteric driver mutations during tumorigenesis are mostly unknown. Here, we mapped somatic mutations generated from 10 tumor-normal matched HNSCC samples into allosteric sites to prioritize the mutated allosteric proteins via whole-exome sequencing and AlloDriver, identifying the specific mutation H351Q in β-glucuronidase (GUSB), a lysosomal enzyme, as a novel allosteric driver mutation, which considerably encouraged HNSCC progression both in vitro and in vivo. Mechanistically, the allosteric mutation of H351Q remarkably attenuated protein trafficking from the endoplasmic reticulum (ER) to lysosomes, leading to ER retention, in which GUSB-H351Q facilitated the aberrant N-glycosylation of PD-L1 through increasing protein stability and mRNA transcripts of the STT3 oligosaccharyltransferase complex catalytic subunit B, an oligosaccharyltransferase complex. Moreover, GUSB-H351Q reshaped a more immunosuppressive microenvironment featuring increased infiltration of exhausted CD8+ T cells and remodeled tumor metabolism, characterized by increased activity of the purine metabolism pathways and pyruvic acid accumulation. This study provides a mechanism-driven approach to overcoming HNSCC progression and immune evasion and identifies novel druggable targets based on the presence of GUSB allosteric driver mutation.

Innovations in cancer immunotherapy: A comprehensive overview of recent breakthroughs and future directions

A major advance in cancer treatment has been the development and refinement of cancer immunotherapy. The discovery of immunotherapies for a wide range of cancers has revolutionized cancer treatment paradigms. Despite relapse or refractory disease, immunotherapy approaches can prolong the life expectancy of metastatic cancer patients. Multiple therapeutic approaches and agents are currently being developed to manipulate various aspects of the immune system. Oncolytic viruses, cancer vaccines, adoptive cell therapies, monoclonal antibodies, cytokine therapies, and inhibitors of immune checkpoints have all proven successful in clinical trials. There are several types of immunotherapeutic approaches available for treating cancer, and others are being tested in preclinical and clinical settings. Immunotherapy has proven successful, and many agents and strategies have been developed to improve its effectiveness. The purpose of this article is to present a comprehensive overview of current immunotherapy approaches used to treat cancer. Cancer immunotherapy advancements, emerging patterns, constraints, and potential future breakthroughs are also discussed.

Loss of RPN1 promotes antitumor immunity via PD-L1 checkpoint blockade in triple-negative breast cancer - experimental studies

BACKGROUND

RPN1, also known as ribophorin I (RPN1), is a type I transmembrane protein that plays an important role in glycosylation. However, the effects of RPN1 on cancer progression and immune evasion in breast cancer (BC) have not been identified.

MATERIALS AND METHODS

The expression of RPN1 was evaluated using RT-qPCR and immunohistochemistry (IHC). The effects of RPN1 on tumor cells were assessed using RT-qPCR, western blotting, flow cytometry, Cell Counting Kit 8 (CCK-8), colony formation assays, and in vivo experiments. The mechanism by which RPN1 modifies programmed death ligand-1 (PD-L1) and the tumor microenvironment was examined by RT-qPCR, western blotting, co-immunoprecipitation (Co-IP), and flow cytometry. The influence of the transcription factor YY1 on RPN1 expression was revealed using bioinformatics analysis, RT-qPCR, and dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays.

RESULTS

RPN1 is aberrantly expressed in triple-negative breast cancer (TNBC) cells, correlating with increased proliferation and poor prognosis. RPN1 mediates the post-translational modification of PD-L1, enhancing its glycosylation and stability, thus facilitating PD-L1-mediated immune escape and tumor growth. The deletion of RPN1 improves the TNBC microenvironment and enhances the efficacy of anti-PD-1 therapy. Additionally, we uncovered a novel regulatory axis involving YY1/RPN1/YBX1 in PD-L1 regulation, affecting TNBC growth and metastasis.

CONCLUSIONS

Our preliminary study reveals that targeting RPN1 promotes immune suppression, providing a new potential immunotherapy strategy for TNBC. However, further research is necessary to fully elucidate and understand the specific mechanisms of RPN1 in TNBC and its potential for clinical application.

Canonical and noncanonical NOTCH signaling in the nongenetic resistance of cancer: distinct and concerted control

Therapeutic resistance in cancer is responsible for numerous cancer deaths in clinical practice. While target mutations are well recognized as the basis of genetic resistance to targeted therapy, nontarget mutation resistance (or nongenetic resistance) remains poorly characterized. Despite its complex and unintegrated mechanisms in the literature, nongenetic resistance is considered from our perspective to be a collective response of innate or acquired resistant subpopulations in heterogeneous tumors to therapy. These subpopulations, e.g., cancer stem-like cells, cancer cells with epithelial-to-mesenchymal transition, and drug-tolerant persisters, are protected by their resistance traits at cellular and molecular levels. This review summarizes recent advances in the research on resistant populations and their resistance traits. NOTCH signaling, as a central regulator of nongenetic resistance, is discussed with a special focus on its canonical maintenance of resistant cancer cells and noncanonical regulation of their resistance traits. This novel view of canonical and noncanonical NOTCH signaling pathways is translated into our proposal of reshaping therapeutic strategies targeting NOTCH signaling in resistant cancer cells. We hope that this review will lead researchers to study the canonical and noncanonical arms of NOTCH signaling as an integrated resistant mechanism, thus promoting the development of innovative therapeutic strategies.

GSH/pH-responsive copper-based cascade nanocomplexes inducing immunogenic cell death through cuproptosis/ferroptosis/necroptosis in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) remains a formidable challenge due to high recurrence rates and limited efficacy of conventional treatments. Immunotherapy holds potential, but its effectiveness is often restricted by low patient responsiveness. This study presents a novel therapeutic strategy using GSH/pH-responsive copper-based cascade nanocomplexes to induce immunogenic cell death (ICD) in OSCC. The fabricated nanocomplex, PC@B-H, leverages the acidic and reducing tumor microenvironment to release copper ions and plumbagin, triggering a cascade of cell death mechanisms including cuproptosis, ferroptosis, and necroptosis. This multifunctional system not only enhances oxidative stress but also depletes glutathione, promotes lipid peroxidation, and disrupts mitochondrial function, leading to robust tumor inhibition. Additionally, the induction of ICD facilitates dendritic cell maturation and cytotoxic T lymphocyte infiltration, providing durable anti-tumor immunity. The study demonstrates that PC@B-H achieves a 92.3 % tumor growth inhibition rate with minimal systemic toxicity, offering a promising avenue for enhancing the efficacy of OSCC treatment through combined cell death pathways and immune activation.

Progress in understanding the regulatory mechanisms of immune checkpoint proteins PD-1 and PD-L1 expression

Programmed Death Protein-1 (PD-1) is a cell surface receptor that serves as a checkpoint for T cells, playing a pivotal role in regulating T-cell apoptosis. The binding of PD-1 to its ligand, Programmed Death Ligand 1 (PD-L1), inhibits anti-tumor immunity by suppressing T-cell activation signals. Indeed, the PD-1/PD-L1 pathway governs the induction and maintenance of immune tolerance within the tumor microenvironment. Consequently, the regulation of PD-1/PD-L1 immune checkpoint expression is of paramount importance. This review summarizes the mechanisms governing PD1/PD-L1 expression at various stages, including transcription, post-transcription (mRNA processing), and post-translation (protein modifications), as well as immunotherapy targeting PD1/PD-L1, aiming to further explore novel strategies for tumor immunotherapy.

Therapy-induced senescent cancer cells contribute to cancer progression by promoting ribophorin 1-dependent PD-L1 upregulation

Conventional chemotherapy- and radiotherapy-induced cancer senescence, which is characterized by poor proliferation, drug resistance, and senescence-associated secretory phenotype, has gained attention as contributing to cancer relapse and the development of an immunosuppressive tumor microenvironment. However, the association between cancer senescence and anti-tumor immunity is not fully understood. Here, we demonstrate that senescent cancer cells increase the level of PD-L1 by promoting its transcription and glycosylation. We identify ribophorin 1 as a key regulator of PD-L1 glycosylation during cancer senescence. Ribophorin 1 depletion reduces this elevated level of PD-L1 through the ER-lysosome-associated degradation pathway, thereby increasing the susceptibility of senescent cancer cells to T-cell-mediated killing. Consistently, ribophorin 1 depletion suppresses tumor growth by decreasing PD-L1 levels and boosting cytotoxic T lymphocyte activity in male mice. Moreover, ribophorin 1-targeted or anti-PD-1 therapy reduces the number of senescent cancer cells in irradiated tumors and suppresses cancer recurrence through the activation of cytotoxic T lymphocytes. These results provide crucial insights into how senescent cancer cells can escape T-cell immunity following cancer treatment and thereby contribute to cancer recurrence. Our findings also highlight the therapeutic promise of targeting senescent cancer cells for cancer treatment.

Comprehensive Potential of Artificial Intelligence for Predicting PD-L1 Expression and EGFR Mutations in Lung Cancer: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the methodological quality and the predictive performance of artificial intelligence (AI) for predicting programmed death ligand 1 (PD-L1) expression and epidermal growth factor receptors (EGFR) mutations in lung cancer (LC) based on systematic review and meta-analysis.

METHODS

AI studies based on PET/CT, CT, PET, and immunohistochemistry (IHC)-whole-slide image (WSI) were included to predict PD-L1 expression or EGFR mutations in LC. The modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to evaluate the methodological quality. A comprehensive meta-analysis was conducted to analyze the overall area under the curve (AUC). The Cochrane diagnostic test and I2 statistics were used to assess the heterogeneity of the meta-analysis.

RESULTS

A total of 45 AI studies were included, of which 10 were used to predict PD-L1 expression and 35 were used to predict EGFR mutations. Based on the analysis using the QUADAS-2 tool, 37 studies achieved a high-quality score of 7. In the meta-analysis of PD-L1 expression levels, the overall AUCs for PET/CT, CT, and IHC-WSI were 0.80 (95% confidence interval [CI], 0.77-0.84), 0.74 (95% CI, 0.69-0.77), and 0.95 (95% CI, 0.93-0.97), respectively. For EGFR mutation status, the overall AUCs for PET/CT, CT, and PET were 0.85 (95% CI, 0.81-0.88), 0.83 (95% CI, 0.80-0.86), and 0.75 (95% CI, 0.71-0.79), respectively. The Cochrane Diagnostic Test revealed an I2 value exceeding 50%, indicating substantial heterogeneity in the PD-L1 and EGFR meta-analyses. When AI was combined with clinicopathological features, the enhancement in predicting PD-L1 expression was not substantial, whereas the prediction of EGFR mutations showed improvement compared to the CT and PET models, albeit not significantly so compared to the PET/CT models.

CONCLUSIONS

The overall performance of AI in predicting PD-L1 expression and EGFR mutations in LC has promising clinical implications.

Intrinsic PD-L1 Degradation Induced by a Novel Self-Assembling Hexapeptide for Enhanced Cancer Immunotherapy

Programmed death-ligand 1 (PD-L1) is a critical immune checkpoint protein that facilitates tumor immune evasion. While antibody-based PD-1/PD-L1 inhibitors have shown promise, their limitations necessitate the development of alternative therapeutic strategies. This work addresses these challenges by developing a hexapeptide, KFM (Lys-Phe-Met-Phe-Met-Lys), capable of both directly downregulating PD-L1 and self-assembling into a ROS-responsive supramolecular hydrogel. This dual functionality allows Gel KFM to function as a localized drug delivery system and a PD-L1 inhibitor. Loading the hydrogel with mitoxantrone (MTX) and metformin (MET) further enhances the therapeutic effect by combining chemotherapy with PD-L1 downregulation. In vitro and in vivo studies demonstrate significant tumor growth inhibition, increased CD8+ T cell infiltration, and reduced intratumoral PD-L1 expression following peritumoral administration. Mechanistically, KFM promotes PD-L1 degradation via a ubiquitin-dependent pathway. This "carrier-free" delivery system expands the role of supramolecular hydrogels beyond passive carriers to active immunotherapeutic agents, offering a promising new strategy for cancer therapy.

Stemness in solid malignancies: coping with immune attack

Immunotherapy has become a key new pillar of cancer treatment, and this has sparked interest in understanding mechanisms of cancer immune evasion. It has long been appreciated that cancers are constituted by heterogeneous populations of tumour cells. This feature is often fuelled by specialized cells that have molecular programs resembling tissue stem cells. Although these cancer stem cells (CSCs) have capacity for unlimited self-renewal and differentiation, it is increasingly evident that some CSCs are capable of achieving remarkable immune resistance. Given that most immunotherapy regiments have overlooked CSC-specific immune-evasive mechanisms, many current treatment strategies often lead to cancer relapse. This Review focuses on advancements in understanding how CSCs in solid tumours achieve their unique immune-evasive properties, enabling them to drive tumour regrowth. Moreover, as cancers often arise from tissue stem cells that acquired oncogenic mutations, we discuss how tissue stem cells undergoing malignant transformation activate intrinsic immune-evasive mechanisms and establish close interactions with suppressive immune cells to escape immune surveillance. In addition, we summarize how in advanced disease stages, CSCs often hijack features of normal stem cells to resist antitumour immunity. Finally, we provide insights in how to design a new generation of cancer immunotherapies to ensure elimination of CSCs.

Fusobacterium nucleatum is enriched in invasive biofilms in colorectal cancer

Fusobacterium nucleatum is an oral bacterium known to colonize colorectal tumors, where it is thought to play an important role in cancer progression. Recent advances in sequencing and phenotyping of F. nucleatum have revealed important differences at the subspecies level, but whether these differences impact the overall tumor ecology, and tumorigenesis itself, remain poorly understood. In this study, we sought to characterize Fusobacteria in the tumor microbiome of a cohort of individuals with CRC through a combination of molecular, spatial, and microbiologic analyses. We assessed for relative abundance of F. nucleatum in tumors compared to paired normal tissue, and correlated abundance with clinical and pathological features. We demonstrate striking enrichment of F. nucleatum and the recently discovered subspecies animalis clade 2 (Fna C2) specifically in colon tumors that have biofilms, highlighting the importance of complex community partnerships in the pathogenesis of this important organism.

The role of liver cancer stem cells in hepatocellular carcinoma metastasis

Metastasis accounts for the vast majority of cancer deaths; however, this complex process has yet to be fully explained. To form metastases, cancer cells must undergo a series of steps, known as the "Metastatic cascade", each of which requires a specific functional transformation. Cancer stem cells (CSCs) play a vital role in tumor metastasis, but their dynamic behavior and regulatory mechanisms have not been fully elucidated. Based on the "Metastatic cascade" theory, this review summarizes the effect of liver CSCs on the metastatic biological programs that underlie the dissemination and metastatic growth of cancer cells. Liver CSCs have the capacity to initiate distant organ metastasis via EMT, and the microenvironment transformation that supports the ability of these cells to disseminate, evade immune surveillance, dormancy, and regenerate metastasis. Understanding the heterogeneity and traits of liver CSCs in these processes is critical for developing strategies to prevent and treat metastasis of advanced hepatocellular carcinoma (HCC).

A STT3A-dependent PD-L1 glycosylation modification mediated by GMPS drives tumor immune evasion in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a malignant tumor characterized by rapid progression. To explore the regulatory mechanism of rapid tumor growth and metastasis, we conducted proteomic and scRNA-Seq analyses on advanced HCC tissues and identified a significant molecule, guanine monophosphate synthase (GMPS), closely associated with the immune evasion in HCC. We analyzed the immune microenvironment characteristics remodeled by GMPS using scRNA-Seq and found GMPS induced tumor immune evasion in HCC by impairing the tumor-killing function of CD8 + T cells. Further investigation revealed that GMPS increased PD-L1 expression by regulating its ubiquitination and glycosylation modification. Mechanistically, GMPS enhanced the bond between PD-L1 and the catalytic subunit STT3A of oligosaccharyltransferase (OST) by acting as an additional module connecting the Sec61 channel complex and STT3A, which aided in the translocation and modification of nascent peptides. Increased PD-L1 impaired the tumor-killing function of CD8 + T cells, leading to the immune evasion. Importantly, targeting GMPS with angustmycin A, an inhibitor of GMPS activity, significantly suppressed PD-L1 expression and tumor growth in HCC, which also increased the sensitivity to anti-CTLA-4 immunotherapy. These findings suggested the potential of targeting GMPS as a promising therapeutic approach for HCC.

The hallmarks of cancer immune evasion

According to the widely accepted "three Es" model, the host immune system eliminates malignant cell precursors and contains microscopic neoplasms in a dynamic equilibrium, preventing cancer outgrowth until neoplastic cells acquire genetic or epigenetic alterations that enable immune escape. This immunoevasive phenotype originates from various mechanisms that can be classified under a novel "three Cs" conceptual framework: (1) camouflage, which hides cancer cells from immune recognition, (2) coercion, which directly or indirectly interferes with immune effector cells, and (3) cytoprotection, which shields malignant cells from immune cytotoxicity. Blocking the ability of neoplastic cells to evade the host immune system is crucial for increasing the efficacy of modern immunotherapy and conventional therapeutic strategies that ultimately activate anticancer immunosurveillance. Here, we review key hallmarks of cancer immune evasion under the "three Cs" framework and discuss promising strategies targeting such immunoevasive mechanisms.

N-Acetylated Monosaccharides and Derived Glycan Structures Occurring in N- and O-Glycans During Prostate Cancer Development

Post-translational modifications of proteins play an important role in their stability, solubility and in vivo function. Also, for several reasons, such as the Golgi fragmentation during cancerogenesis, glycosylation as the most common modification is especially promising in offering high cancer specificity which, in combination with tissue-specific biomarkers available in the case of prostate diseases (PSA, PSMA, PAP), may lead to the development of novel oncodiagnostic approaches. In this review, we present the importance of subterminal glycan structures based on the N-acetylated monosaccharides GlcNAc and GalNAc in N- and also O-glycans, structures of which they are a component (LacNAc, LacdiNAc, branched structures). We also discuss the importance and clinical performance of these structures in cases of prostate cancer diagnostics using lectin-based affinity methods, which could be implemented in clinical laboratory practice in the future.

Epigenetic control of immunoevasion in cancer stem cells

Cancer stem cells (CSCs) are a poorly differentiated population of malignant cells that (at least in some neoplasms) is responsible for tumor progression, resistance to therapy, and disease relapse. According to a widely accepted model, all stages of cancer progression involve the ability of neoplastic cells to evade recognition or elimination by the host immune system. In line with this notion, CSCs are not only able to cope with environmental and therapy-elicited stress better than their more differentiated counterparts but also appear to better evade tumor-targeting immune responses. We summarize epigenetic modifications of DNA and histones through which CSCs evade immune recognition or elimination, and propose that such alterations constitute promising therapeutic targets to increase the sensitivity of some malignancies to immunotherapy.

Influencing immunity: role of extracellular vesicles in tumor immune checkpoint dynamics

Immune checkpoint proteins (ICPs) serve as critical regulators of the immune system, ensuring protection against damage due to overly activated immune responses. However, within the tumor environment, excessive ICP activation weakens antitumor immunity. Despite the development of numerous immune checkpoint blockade (ICB) drugs in recent years, their broad application has been inhibited by uncertainties about their clinical efficacy. A thorough understanding of ICP regulation in the tumor microenvironment is essential for advancing the development of more effective and safer ICB therapies. Extracellular vesicles (EVs), which are pivotal mediators of cell-cell communication, have been extensively studied and found to play key roles in the functionality of ICPs. Nonetheless, a comprehensive review summarizing the current knowledge about the crosstalk between EVs and ICPs in the tumor environment is lacking. In this review, we summarize the interactions between EVs and several widely studied ICPs as well as their potential clinical implications, providing a theoretical basis for further investigation of EV-related ICB therapeutic approaches.

Delineating the Immunotherapeutic Potential of Vitamin E and Its Analogues in Cancer: A Comprehensive Narrative Review

Cancer is a disease resulting from uncontrolled cell division, which significantly contributes to human mortality rates. An alternative approach to cancer treatment, such as cancer immunotherapy, is needed as the existing chemotherapy and radiotherapy approaches target the cancer cells and healthy dividing cells. Vitamin E is a plant-derived lipid-soluble antioxidant with numerous health-promoting benefits, including anticancer and immunomodulatory properties. Vitamin E comprises eight natural isoforms: tocopherols (α, β, δ, and γ) and tocotrienols (α, β, δ, and γ). While initial research focused on the anticancer properties of α-tocopherol, there is growing interest in other natural forms and modified synthetic analogues of vitamin E due to their unique properties and enhanced anticancer effects. Hence, this review is aimed at outlining the effect of vitamin E and its analogues at various steps of the cancer-immunity cycle that can be used to stimulate anticancer immune responses.

FAT10 induces immune suppression by upregulating PD-L1 expression in hepatocellular carcinoma

The upregulation of programmed death ligand 1 (PD-L1) plays a crucial role in facilitating cancer cells to evade immune surveillance through immunosuppression. However, the precise regulatory mechanisms of PD-L1 in hepatocellular carcinoma (HCC) remain undefined. The correlation between PD-L1 and ubiquitin-like molecules (UBLs) was studied using sequencing data from 20 HCC patients in our center, combined with TCGA data. Specifically, the association between FAT10 and PD-L1 was further validated at both the protein and mRNA levels in HCC tissues from our center. Subsequently, the effect of FAT10 on tumor progression and immune suppression was examined through both in vivo and in vitro experiments. Utilizing sequencing data, qPCR, and Western blotting assays, we confirmed that FAT10 was highly expressed in HCC tissues and positively correlated with PD-L1 expression. Additionally, in vitro experiments demonstrated that the overexpression of FAT10 fostered the proliferation, migration, and invasion of HCC cells. Furthermore, the overexpression of FAT10 in HCC cells led to an increase in PD-L1 expression, resulting in the inhibition of T cell proliferation and the enhancement of HCC cell resistance to T cell-mediated cytotoxicity. Moreover, in vivo experiments utilizing the C57BL/6 mouse model revealed that overexpression of FAT10 effectively suppressed the infiltration of CD8 + GZMB + and CD8 + Ki67 + T cells, as well as reduced serum levels of TNF-α and IFN-γ. Mechanistically, we further identified that FAT10 upregulates PD-L1 expression via activating the PI3K/AKT/mTOR pathway, but not in a ubiquitin-like modification. In conclusion, our findings indicate that FAT10 promotes immune evasion of HCC via upregulating PD-L1 expression, suggesting its potential as a novel target to enhance the efficiency of immunotherapy in HCC.

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.

Chromosomal instability as an architect of the cancer stemness landscape

Despite a critical role for tumor-initiating cancer stem cells (CSCs) in breast cancer progression, major questions remain about the properties and signaling pathways essential for their function. Recent discoveries highlighting mechanisms of CSC-resistance to the stress caused by chromosomal instability (CIN) may provide valuable new insight into the underlying forces driving stemness properties. While stress tolerance is a well-known attribute of CSCs, CIN-induced stress is distinctive since levels appear to increase during tumor initiation and metastasis. These dynamic changes in CIN levels may serve as a barrier constraining the effects of non-CSCs and shaping the stemness landscape during the early stages of disease progression. In contrast to most other stresses, CIN can also paradoxically activate pro-tumorigenic antiviral signaling. Though seemingly contradictory, this may indicate that mechanisms of CIN tolerance and pro-tumorigenic inflammatory signaling closely collaborate to define the CSC state. Together, these unique features may form the basis for a critical relationship between CIN and stemness properties.

Circulating tumor cells: from new biological insights to clinical practice

The primary reason for high mortality rates among cancer patients is metastasis, where tumor cells migrate through the bloodstream from the original site to other parts of the body. Recent advancements in technology have significantly enhanced our comprehension of the mechanisms behind the bloodborne spread of circulating tumor cells (CTCs). One critical process, DNA methylation, regulates gene expression and chromosome stability, thus maintaining dynamic equilibrium in the body. Global hypomethylation and locus-specific hypermethylation are examples of changes in DNA methylation patterns that are pivotal to carcinogenesis. This comprehensive review first provides an overview of the various processes that contribute to the formation of CTCs, including epithelial-mesenchymal transition (EMT), immune surveillance, and colonization. We then conduct an in-depth analysis of how modifications in DNA methylation within CTCs impact each of these critical stages during CTC dissemination. Furthermore, we explored potential clinical implications of changes in DNA methylation in CTCs for patients with cancer. By understanding these epigenetic modifications, we can gain insights into the metastatic process and identify new biomarkers for early detection, prognosis, and targeted therapies. This review aims to bridge the gap between basic research and clinical application, highlighting the significance of DNA methylation in the context of cancer metastasis and offering new avenues for improving patient outcomes.

New horizons in the mechanisms and therapeutic strategies for PD-L1 protein degradation in cancer

Programmed death-ligand 1 (PD-L1) has become a crucial focus in cancer immunotherapy considering it is found in many different cells. Cancer cells enhance the suppressive impact of programmed death receptor 1 (PD-1) through elevating PD-L1 expression, which allows them to escape immune detection. Although there have been significant improvements, the effectiveness of anti-PD-1/PD-L1 treatment is still limited to a specific group of patients. An important advancement in cancer immunotherapy involves improving the PD-L1 protein degradation. This review thoroughly examined the processes by which PD-L1 breaks down, including the intracellular pathways of ubiquitination-proteasome and autophagy-lysosome. In addition, the analysis revealed changes that affect PD-L1 stability, such as phosphorylation and glycosylation. The significant consequences of these procedures on cancer immunotherapy and their potential role in innovative therapeutic approaches are emphasised. Our future efforts will focus on understanding new ways in which PD-L1 degradation is controlled and developing innovative treatments, such as proteolysis-targeting chimeras designed specifically to degrade PD-L1. It is crucial to have a thorough comprehension of these pathways in order to improve cancer immunotherapy strategies and hopefully improve therapeutic effectiveness.

GFPT1 accelerates immune escape in breast cancer by modifying PD-L1 via O-glycosylation

BACKGROUND

Immune escape is one of the causes of poor prognosis in breast cancer (BC). Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the first speed-limiting enzyme of the hexosamine biosynthesis pathway (HBP) and is essential for the progression of BC. Nevertheless, the mechanism of the influence of GFPT1 in BC immune escape is not clear.

METHODS

First, the level of GFPT1 in BC was analyzed by starbase, and GFPT1 expression in BC tissues was measured by qRT-PCR, western blot and IHC. Then, the O-GlcNAc levels were detected by western blot. Thereafter, Co-IP was applied to examine the relationship between GFPT1 and PD-L1. At last, a mouse model was constructed for validation in vivo.

RESULTS

Firstly, we discovered that GFPT1 was obviously strengthened in BC. Knockdown or introduction of GFPT1 correspondingly degraded and elevated O-GlcNAc levels in cells. Further researches revealed that there was a reciprocal relationship between GFPT1 and PD-L1. Mechanistically, we disclosed that GFPT1 enhanced PD-L1 protein stability through O-glycosylation. More interestingly, GFPT1 accelerated BC cell immune escape via upregulation of O-glycosylation-modified PD-L1. In vivo, silencing of GFPT1 attenuated immune escape of BC cells by reducing PD-L1 levels.

CONCLUSION

GFPT1 promoted BC progression and immune escape via O-glycosylation-modified PD-L1. GFPT1 may be a potential target for BC therapy.

The Peptidoglycan Recognition Protein 1 confers immune evasive properties on pancreatic cancer stem cells

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) has limited therapeutic options, particularly with immune checkpoint inhibitors. Highly chemoresistant 'stem-like' cells, known as cancer stem cells (CSCs), are implicated in PDAC aggressiveness. Thus, comprehending how this subset of cells evades the immune system is crucial for advancing novel therapies.

DESIGN

We used the KPC mouse model (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre) and primary tumour cell lines to investigate putative CSC populations. Transcriptomic analyses were conducted to pinpoint new genes involved in immune evasion. Overexpressing and knockout cell lines were established with lentiviral vectors. Subsequent in vitro coculture assays, in vivo mouse and zebrafish tumorigenesis studies, and in silico database approaches were performed.

RESULTS

Using the KPC mouse model, we functionally confirmed a population of cells marked by EpCAM, Sca-1 and CD133 as authentic CSCs and investigated their transcriptional profile. Immune evasion signatures/genes, notably the gene peptidoglycan recognition protein 1 (PGLYRP1), were significantly overexpressed in these CSCs. Modulating PGLYRP1 impacted CSC immune evasion, affecting their resistance to macrophage-mediated and T-cell-mediated killing and their tumourigenesis in immunocompetent mice. Mechanistically, tumour necrosis factor alpha (TNFα)-regulated PGLYRP1 expression interferes with the immune tumour microenvironment (TME) landscape, promoting myeloid cell-derived immunosuppression and activated T-cell death. Importantly, these findings were not only replicated in human models, but clinically, secreted PGLYRP1 levels were significantly elevated in patients with PDAC.

CONCLUSIONS

This study establishes PGLYRP1 as a novel CSC-associated marker crucial for immune evasion, particularly against macrophage phagocytosis and T-cell killing, presenting it as a promising target for PDAC immunotherapy.

Multidimensional analysis of tumor stem cells: from biological properties, metabolic adaptations to immune escape mechanisms

As a key factor in tumorigenesis, progression, recurrence and metastasis, the biological properties, metabolic adaptations and immune escape mechanisms of CSCs are the focus of current oncological research. CSCs possess self-renewal, multidirectional differentiation and tumorigenicity, and their mechanisms of action can be elucidated by the clonal evolution, hierarchical model and the dynamic CSCs model, of which the dynamic model is widely recognized due to its better explanation of the function and origin of CSCs. The origin hypothesis of CSCs involves cell-cell fusion, horizontal gene transfer, genomic instability and microenvironmental regulation, which together shape the diversity of CSCs. In terms of classification, CSCs include primary CSCs (pri-CSCs), precancerous stem cells (pre-CSCs), migratory CSCs (mig-CSCs), and chemo-radiotherapy-resistant CSCs (cr-CSCs and rr-CSCs), with each type playing a specific role in tumor progression. Surface markers of CSCs, such as CD24, CD34, CD44, CD90, CD133, CD166, EpCAM, and LGR5, offer the possibility of identifying, isolating, and targeting CSCs, but the instability and heterogeneity of their expression increase the difficulty of treatment. CSCs have adapted to their survival needs through metabolic reprogramming, showing the ability to flexibly switch between glycolysis and oxidative phosphorylation (OXPHOS), as well as adjustments to amino acid and lipid metabolism. The Warburg effect typifies their metabolic profiles, and altered glutamine and fatty acid metabolism further contributes to the rapid proliferation and survival of CSCs. CSCs are able to maintain their stemness by regulating the metabolic networks to maintain their stemness characteristics, enhance antioxidant defences, and adapt to therapeutic stress. Immune escape is another strategy for CSCs to maintain their survival, and CSCs can effectively evade immune surveillance through mechanisms such as up-regulating PD-L1 expression and promoting the formation of an immunosuppressive microenvironment. Together, these properties reveal the multidimensional complexity of CSCs, underscoring the importance of a deeper understanding of the biology of CSCs for the development of more effective tumor therapeutic strategies. In the future, therapies targeting CSCs will focus on precise identification of surface markers, intervention of metabolic pathways, and overcoming immune escape, with the aim of improving the relevance and efficacy of cancer treatments, and ultimately improving patient prognosis.

Regulation of post-translational modification of PD-L1 and associated opportunities for novel small-molecule therapeutics

PD-L1 is overexpressed on the surface of tumor cells and binds to PD-1, resulting in tumor immune escape. Therapeutic strategies to target the PD-1/PD-L1 pathway involve blocking the binding. Immune checkpoint inhibitors have limited efficacy against tumors because PD-L1 is also present in the cytoplasm. PD-L1 of post-translational modifications (PTMs) have uncovered numerous mechanisms contributing to carcinogenesis and have identified potential therapeutic targets. Therefore, small molecule inhibitors can block crucial carcinogenic signaling pathways, making them a potential therapeutic option. To better develop small molecule inhibitors, we have summarized the PTMs of PD-L1. This review discusses the regulatory mechanisms of small molecule inhibitors in carcinogenesis and explore their potential applications, proposing a novel approach for tumor immunotherapy based on PD-L1 PTM.

Genetically engineered nanomodulators elicit potent immunity against cancer stem cells by checkpoint blockade and hypoxia relief

Rapid development of checkpoint inhibitors has provided significant breakthroughs for cancer stem cell (CSC) therapy, while the therapeutic efficacy is restricted by hypoxia-mediated tumor immune evasion, especially hypoxia-induced CD47 overexpression in CSCs. Herein, we developed a genetically engineered CSC membrane-coated hollow manganese dioxide (hMnO2@gCMs) to elicit robust antitumor immunity by blocking CD47 and alleviating hypoxia to ultimately achieve the eradication of CSCs. The hMnO2 core effectively alleviated tumor hypoxia by inducing decomposition of tumor endogenous H2O2, thus suppressing the CSCs and reducing the expression of CD47. Cooperating with hypoxia relief-induced downregulation of CD47, the overexpressed SIRPα on gCM shell efficiently blocked the CD47-SIRPα "don't eat me" pathway, synergistically eliciting robust antitumor-mediated immune responses. In a B16F10-CSC bearing melanoma mouse model, the hMnO2@gCMs showed an enhanced therapeutic effect in eradicating CSCs and inhibiting tumor growth. Our work presents a simple, safe, and robust platform for CSC eradication and cancer immunotherapy.

N-linked glycosylation of PD-L1/PD-1: an emerging target for cancer diagnosis and treatment

During tumorigenesis and progression, the immune checkpoint programmed death-1 (PD-1) and its ligand programmed death ligand-1 (PD-L1) play critical roles in suppressing T cell-mediated anticancer immune responses, leading to T-cell exhaustion and subsequent tumor evasion. Therefore, anti-PD-L1/PD-1 therapy has been an attractive strategy for treating cancer over the past decade. However, the overall efficacy of this approach remains suboptimal, revealing an urgent need for novel insights. Interestingly, increasing evidence indicates that both PD-L1 on tumor cells and PD-1 on tumor-specific T cells undergo extensive N-linked glycosylation, which is essential for the stability and interaction of these proteins, and this modification promotes tumor evasion. In various preclinical models, targeting the N-linked glycosylation of PD-L1/PD-1 was shown to significantly increase the efficacy of PD-L1/PD-1 blockade therapy. Furthermore, deglycosylation of PD-L1 strengthens the signal intensity in PD-L1 immunohistochemistry (IHC) assays, improving the diagnostic and therapeutic relevance of this protein. In this review, we provide an overview of the regulatory mechanisms underlying the N-linked glycosylation of PD-L1/PD-1 as well as the crucial role of N-linked glycosylation in PD-L1/PD-1-mediated immune evasion. In addition, we highlight the promising implications of targeting the N-linked glycosylation of PD-L1/PD-1 in the clinical diagnosis and treatment of cancer. Our review identifies knowledge gaps and sheds new light on the cancer research field.

Post-translational modifications: The potential ways for killing cancer stem cells

While strides in cancer treatment continue to advance, the enduring challenges posed by cancer metastasis and recurrence persist as formidable contributors to the elevated mortality rates observed in cancer patients. Among the multifaceted factors implicated in tumor recurrence and metastasis, cancer stem cells (CSCs) emerge as noteworthy entities due to their inherent resistance to conventional therapies and heightened invasive capacities. Characterized by their notable abilities for self-renewal, differentiation, and initiation of tumorigenesis, the eradication of CSCs emerges as a paramount objective. Recent investigations increasingly emphasize the pivotal role of post-translational protein modifications (PTMs) in governing the self-renewal and replication capabilities of CSCs. This review accentuates the critical significance of several prevalent PTMs and the intricate interplay of PTM crosstalk in regulating CSC behavior. Furthermore, it posits that the manipulation of PTMs may offer a novel avenue for targeting and eliminating CSC populations, presenting a compelling perspective on cancer therapeutics with substantial potential for future applications.

Identification of tumor stemness and immunity related prognostic factors and sensitive drugs in head and neck squamous cell carcinoma

The presence of cancer stem cells (CSCs) contributes significantly to treatment resistance in various cancers, including head and neck squamous cell carcinoma (HNSCC). Despite this, the relationship between cancer stemness and immunity remains poorly understood. In this study, we aimed to identify potential immunotherapeutic targets and sensitive drugs for CSCs in HNSCC. Using data from public databases, we analyzed expression patterns and prognostic values in HNSCC. The stemness index was calculated using the single-sample gene set enrichment analysis (ssgsea) algorithm, and weighted gene co-expression network analysis (WGCNA) was employed to screen for key stemness-related modules. Consensus clustering was then used to group samples for further analysis, and prognosis-related key genes were identified through regression analysis. Our results showed that tumor samples from HNSCC exhibited higher stemness indices compared to normal samples. WGCNA identified a module highly correlated with stemness, comprising 187 genes, which were significantly enriched in protein digestion and absorption pathways. Furthermore, we identified sensitive drugs targeting prognostic genes associated with tumor stemness. Notably, two genes, HLF and CCL11, were found to be highly associated with both stemness and immunity. In conclusion, our study identifies a stemness-related gene signature and promising drug candidates for CSCs of HNSCC. Additionally, HLF and CCL11, which are associated with both stemness and immunity, represent potential targets for immunotherapy in HNSCC.