Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

The important role of myeloid-derived suppressor cells: From hepatitis to liver cancer

Liver homeostasis is coordinated by crosstalk between resident and infiltrating inflammatory cells. Liver disease creates a dynamic inflammatory microenvironment characterized by aberrant metabolism and continuous hepatic regeneration, making it an important risk factor for hepatocellular carcinoma (HCC) as well as liver failure. Recent studies have revealed a critical heterogeneous population of myeloid-derived suppressor cells (MDSCs), which influence liver disease progression and malignancy by dynamically regulating the immune microenvironment. MDSCs play an important role in preventing excessive immune responses in the liver. However, MDSCs are also associated with the promotion of liver injury and liver cancer progression. The plasticity of MDSCs in liver disease is a unique challenge for therapeutic intervention strategies and requires a deeper understanding of the underlying mechanisms. Here, we review the role of MDSCs in the establishment and progression of liver disease and highlight the evidence for MDSCs as a priority target for current and future therapeutic strategies. We explore the fate of MDSCs from hepatitis to liver cancer, providing recent insights into potential targets for clinical intervention.

Recent developments in peptide vaccines against Glioblastoma, a review and update

Glioblastoma multiforme (GBM) is the most prevalent invasive CNS tumor, with a high incidence rate and a high likelihood of recurrence in most patients. Despite available treatments, recurrent glioblastoma (rGBM) exhibits growing resistance to chemotherapy and radiotherapy, which necessitates the development of newer methods of treatment. Peptide vaccines, a type of cancer immunotherapy, have recently attracted attention as a potentially practical therapeutic approach because they target tumor-associated or tumor-specific antigens to generate an effective immune response against cancer cells. These vaccines have been included in several clinical trials, demonstrating their safety and effectiveness by eliciting protective immune responses. However, peptide vaccines for glioblastoma face challenges due to the complex nature of intracranial brain tumors that require innovative approaches and in-depth research to increase their efficacy. The main topics covered in this article include immunological inhibitors and immune characteristics of the CNS and GBM, the basis of immunity, and the significant results of clinical trials of peptide vaccine therapy for GBM. Additionally, it examines the potential causes of the low effectiveness of these vaccines and recommends future research to address the specific challenges associated with immunotherapy in GBM. The evaluation of preliminary phase studies and phase III clinical trials will provide insights into potential immunological responses, biosecurity precautions, and clinical outcomes, guiding future vaccination initiatives to promote higher effectiveness.

The role of notch signaling in regulating myeloid-derived suppressor cells: Implications in Cancer and autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) encompass monocytes and granulocytes, which are innate immune cells capable of suppressing T cells and NK cells. MDSCs exert numerous detrimental effects, as they facilitate tumor initiation, promote tumor growth and metastasis, suppress host immune responses, and evade immune surveillance, thereby hindering anticancer responses. Conversely, in autoimmune diseases, MDSCs exhibit dysfunctional immunosuppressive functions and often display pro-inflammatory effects, which can exacerbate immune disorders. We postulate that this discrepancy is attributable to the involvement of the Notch signaling pathway. The Notch signaling pathway is an evolutionarily conserved mechanism that plays a crucial role in maintaining normal mammalian physiological functions. The Notch receptor undergoes three cleavage events before being transported into the nucleus, where it regulates the transcription of target genes. The role of Notch or MDSCs in different diseases has been fully reported, but the regulatory role of Notch signaling pathway on MDSCs in different diseases has been rarely reported.In this review, we characterize the activation, expansion, and immune suppression mechanisms of MDSCs. We then introduce the Notch signaling pathway and finally discuss its role in colorectal cancer, breast cancer, lung cancer, as well as T-cell acute lymphoblastic leukemia, systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. The Notch signaling pathway regulates MDSCs through distinct mechanisms in these contexts. We hope this review will aid both beginners and experts in systematically understanding the regulation of MDSCs by the Notch signaling pathway in cancer and autoimmune diseases.

Tumor-infiltrating myeloid cells; mechanisms, functional significance, and targeting in cancer therapy

Tumor-infiltrating myeloid cells (TIMs), which encompass tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), and tumor-associated dendritic cells (TADCs), are of great importance in tumor microenvironment (TME) and are integral to both pro- and anti-tumor immunity. Nevertheless, the phenotypic heterogeneity and functional plasticity of TIMs have posed challenges in fully understanding their complexity roles within the TME. Emerging evidence suggested that the presence of TIMs is frequently linked to prevention of cancer treatment and improvement of patient outcomes and survival. Given their pivotal function in the TME, TIMs have recently been recognized as critical targets for therapeutic approaches aimed at augmenting immunostimulatory myeloid cell populations while depleting or modifying those that are immunosuppressive. This review will explore the important properties of TIMs related to immunity, angiogenesis, and metastasis. We will also document the latest therapeutic strategies targeting TIMs in preclinical and clinical settings. Our objective is to illustrate the potential of TIMs as immunological targets that may improve the outcomes of existing cancer treatments.

Circular RNAs: key players in tumor immune evasion

Immune responses against tumor antigens play a role in confining tumor growth. In response, cancer cells developed several mechanisms to bypass or defeat these anti-tumor immune responses-collectively referred to as "tumor immune evasion". Recent studies have shown that a group of non-coding RNAs, namely circRNAs affect several aspects of tumor immune evasion through regulation of activity of CD8 + T cells, regulatory T cells, natural killer cells, cytokine-induced killer cells or other immune cells. Understanding the role of circRNAs in this process facilitate design of novel therapies for enhancing the anti-tumor capacity of immune system. This review provides an outline of different roles of circRNAs in the tumor immune evasion.

Comprehensive immunogenomic landscape analysis unveils CD33 + myeloid cell-driven immunomodulatory signatures in melanoma development

BACKGROUND

Understanding the causal relationships between immune cell populations and cancer development remains a critical challenge in tumor immunology.

METHODS

We employed Mendelian Randomization analysis leveraging genome-wide association studies of 612 immune cell traits and 91 cancer types to systematically evaluate causal associations. Single-cell RNA sequencing and computational deconvolution analyses were performed to characterize myeloid cell subpopulations in melanoma samples.

FINDINGS

Our analysis revealed significant relationships between specific immune cell subsets and cancer risk, particularly highlighting the role of CD33 + myeloid cells in melanoma pathogenesis. Single-cell RNA sequencing identified distinct CD33high myeloid subpopulations characterized by elevated expression of complement cascade components and chemokine signaling pathways. Through computational deconvolution of The Cancer Genome Atlas melanoma cohort, we demonstrated that elevated CD33high monocyte abundance correlates with increased immune dysfunction scores, reduced CD8 + T cell infiltration, and poor survival outcomes.

INTERPRETATION

Here we delineate the multifaceted mechanisms through which CD33 + myeloid cell populations orchestrate perturbations in the tumor-immune microenvironmental landscape, manifesting in compromised immunosurveillance and enhanced tumor progression. Our findings illuminate novel therapeutic opportunities through targeted modulation of myeloid cell function, while providing a systematic framework for understanding the complex interplay between immune cell populations and oncogenic processes.

Metabolomic reprogramming of the tumor microenvironment by dual arginase inhibitor OATD-02 boosts anticancer immunity

Metabolic reprogramming within the tumor microenvironment (TME) plays a central role in cancer progression and immune evasion, with L-arginine metabolism emerging as a key regulatory axis. Arginase overexpression depletes intratumoral L-arginine, thus suppressing T-cell proliferation while fuelling tumor growth through polyamine biosynthesis. OATD-02, a novel dual arginase (ARG1/ARG2) inhibitor, reprograms tumor metabolism by restoring L-arginine availability and reducing the levels of polyamines, thereby shifting the TME toward a more immunostimulatory state. Unlike ARG1-selective inhibitors with limited intracellular uptake, OATD-02 effectively inhibits both extracellular and intracellular arginases, thereby addressing a major limitation of first-generation arginase inhibitors. To visualize the pharmacodynamic effects of OATD-02 dosing in mice with spatial resolution, we employed MALDI mass spectrometry imaging (MALDI-MSI), thus enabling direct mapping of metabolic changes within tumor tissues. In preclinical models, OATD-02 treatment led to widespread accumulation of intratumoral L-arginine with concomitant depletion of polyamines and resulted in metabolic shifts that correlated with increased immune cell infiltration and an improved response to immune checkpoint blockade. These findings underscore the role of dual arginase inhibition in reshaping tumor metabolism and overcoming immune suppression by restoring the metabolic fitness of immune cells to fight cancer. The metabolic changes caused by OATD-02 treatment resulted in significantly enhanced antitumor immune responses, increased T-cell infiltration in tumors, expansion of CD8⁺ T cells in draining lymph nodes, and systemic upregulation of T-cell activation markers. These effects translated into a substantial survival benefit in the CT26 tumor model, particularly when combined with anti-PD-1 therapy, where OATD-02 improved checkpoint blockade efficacy by relieving metabolic constraints affecting tumor-infiltrating lymphocytes. By leveraging the unique capabilities of MALDI-MSI, this study provides high-resolution metabolic insights into the mechanism of action of OATD-02, reinforcing its potential as a next-generation metabolic-immunotherapeutic agent. The observed metabolic reprogramming, coupled with enhanced immune activation and prolonged survival, supports the clinical development of OATD-02 as a promising strategy for enhancing cancer immunotherapy efficacy. OATD-02 is currently undergoing clinical evaluation in a phase I/II trial (NCT05759923), which will further elucidate its safety and therapeutic impact. These findings highlight the potential of arginase-targeted therapies in cancer treatment and underscore the value of MALDI-MSI as a powerful tool for tracking metabolic responses to therapy.

The role of the tumour microenvironment in lung cancer and its therapeutic implications

Lung cancer is the leading cause of cancer-related deaths globally, with tumour growth, invasion, and treatment response heavily influenced by the tumour microenvironment (TME). The TME promotes tumour progression by creating an immunosuppressive environment that hampers the body's antitumour immune response, primarily through the Nuclear Factor Kappa B (NF-κB) and Signal Transducer and Activator of Transcription 3 (STAT3) pathways. These pathways contribute to chronic inflammation, immune evasion, and angiogenesis. Targeting the TME and its signalling pathways has shown potential to enhance treatment efficacy. STAT3, a key transcription factor in lung cancer, drives tumour growth and immune suppression via the mTOR and JAK pathways. Inhibiting these pathways can block STAT3 and slow cancer progression. Promising results have been observed with mTOR inhibitors like CC-115 and Vistusertib, especially when combined with immune checkpoint inhibitors, and with JAK inhibitors such as Ruxolitinib, AZD4205, and Filgotinib. These strategies represent a promising direction for lung cancer therapy. This review explores the intricate relationship between the TME and lung cancer, focussing on novel therapeutic approaches that target immune cells, signalling molecules, and fibroblasts within the TME to improve patient outcomes.

Harnessing Exosomes: From Tumor Immune Escape to Therapeutic Innovation in Gastric Cancer Immunotherapy

Gastric cancer ranks fifth among the most prevalent cancers globally, with a dismal prognosis. In recent years, immunotherapy, particularly immune checkpoint inhibitors, has emerged as a glimmer of hope for advanced gastric cancer patients. However, not all patients can benefit from this treatment modality, as the tumor microenvironment significantly influences treatment efficacy. Exosomes, pivotal mediators of intercellular communication, exert intricate and diverse effects in shaping and regulating the tumor microenvironment. This review provides a comprehensive overview of the functional mechanisms of exosomes within the gastric cancer tumor microenvironment. It delves into their biogenesis, functions, and impact on innate and adaptive immune cells (such as dendritic cells, myeloid-derived suppressor cells, and T cells) and cancer-associated fibroblasts. Additionally, the potential applications of exosomes in gastric cancer immunotherapy are explored, including their use as biomarkers to predict responses to immune checkpoint inhibitors, and drug delivery vectors, and in the development of exosome-based vaccines and gene therapy. Notably, this review emphasizes the dual nature of exosomes: they can facilitate tumor immune escape, yet they also serve as promising targets for innovative therapeutic strategies. It also compares potential exosome-based strategies with existing immunotherapies like ICIs and emerging CAR-T cell therapies. Finally, insights into the future of exosomes in precision immunotherapy for gastric cancer are offered, presenting a forward-looking perspective on this emerging field.

Mediation Mendelian randomization analysis of immune cell phenotypes and glioma risk: unveiling the regulation of cerebrospinal fluid metabolites

BACKGROUND AND OBJECTIVE

Gliomas, particularly glioblastoma multiforme (GBM), are the most common primary central nervous system tumors in adults and are notoriously difficult to treat due to their high heterogeneity and invasiveness. Despite advances in molecular diagnostics and personalized therapies, prognosis remains poor. The immune system plays a critical role in glioma progression. This study employed mediation Mendelian randomization analysis to explore the relationships between immune cell phenotypes, cerebrospinal fluid metabolites, and glioma, aiming to uncover potential mechanisms of tumor progression and immune evasion.

METHOD

In this study, we employed several analytical methods including IVW, MR Egger, Simple mode, Weighted median, and Weighted mode, with IVW results being considered the primary basis. We assessed heterogeneity and pleiotropy, and used leave-one-out analysis to determine sensitivity, ensuring the stability and reliability of the results. The potential mediating effects of cerebrospinal fluid metabolites were investigated to explore the underlying mechanisms linking immune cell function and glioma. The GWAS data for immune cells, cerebrospinal fluid metabolites, and glioma used in this study were sourced from public databases.

RESULT

We identified nine risk immune cell phenotypes for glioma (such as CD19 on IgD( +) CD24(-)), and ten protective immune cell phenotypes (such as CD11c on monocytes). Mediation analysis revealed that levels of 7-alpha-hydroxy-3-oxo-4-cholestenoate (7-hoca) (MP = - 14.6%) and Palmitoyl dihydrosphingomyelin (d18:0/16:0) (MP = 7.9%) partially mediated the relationship between CD3 on CD39( +) resting Treg cells and glioma. Additionally, 7-hoca levels (MP = - 12.3%) and Phenyllactate (pla) levels (MP = 4.12%) partially mediated the association between FSC-A on NKT cells and glioma. Furthermore, Glycerophosphoinositol levels (MP = - 12.1%) and Orotate levels (MP = - 11.4%) partially mediated the relationship between Granulocyte adenylyl cyclase (Granulocyte AC) and glioma.

CONCLUSION

This study identified that specific immune cell phenotypes directly influence glioma risk and indirectly modulate this risk through cerebrospinal fluid metabolites. CD19 on IgD( +) CD24(-) B cells were identified as risk factors, while CD11c on monocytes were protective. Metabolites like 7-hoca and glycerophosphoinositol play key mediating roles. These findings enhance our understanding of glioma pathophysiology and suggest that immune modulation and metabolic intervention may be promising therapeutic strategies.

Single-Cell Atlas of the Peripheral Immune Response in Patients With Chronic Hepatitis B

Cellular immune responses are crucial in determining outcomes of the hepatitis B virus (HBV) infection. Ineffective immune responses enable persistent HBV infection and contribute to progressive liver disease. Understanding the mechanisms underlying immunological HBV tolerance and restoring functional adaptive immune responses is essential for successful chronic hepatitis B (CHB) treatment. This study examined the dysregulated immune responses and immunopathological cell states associated with CHB using single-cell RNA sequencing of peripheral blood mononuclear cells to investigate immune cell composition and transcriptional differences between patients with CHB and healthy donors. Phenotypic alterations in the lymphoid and myeloid compartments were observed following HBV infection. T cell immune profiling in patients with CHB showed enrichment of exhausted CD8+ T cells, impaired cytotoxicity of effector CD8+ T cells, and increased regulatory T cell (Treg) suppressive activity. Immature neutrophils and a unique CD14+ monocyte subset (myeloid-derived suppressor cells) exhibited potent immunosuppressive abilities. A novel population of CD14+CD163+VSIG4+ M2-like macrophages with immunosuppressive and anti-inflammatory phenotypes was enriched in a patient with severe CHB and liver failure, indicating a potential contribution to dysfunctional immune responses. Our study demonstrated immune exhaustion and evasion in chronic HBV infection, elucidating its immunopathological features and suggesting new therapeutic strategies for immune-mediated disorders and unresolved chronic HBV infection.

Therapeutic targeting of the p300/CBP bromodomain enhances the efficacy of immune checkpoint blockade therapy

Blockade of immune checkpoints, such as programmed death-ligand 1 (PD-L1), has shown promise in cancer treatment; however, clinical response remains limited in many cancer types. Our previous research demonstrated that p300/CBP mediates the acetylation of the PD-L1 promoter, regulating PD-L1 expression. In this study, we further investigated the role of the p300/CBP bromodomain in regulating PD-L1 expression using CCS1477, a selective bromodomain inhibitor developed by our team. We found that the p300/CBP bromodomain is essential for H3K27 acetylation at PD-L1 enhancers. Inhibiting this modification significantly reduced enhancer activity and PD-L1 transcription, including exosomal PD-L1, which has been implicated as key contributors to resistance against PD-L1 blockade therapy in various cancers. Furthermore, CCS1477 treatment resulted in a marked reduction of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment (TME) by inhibiting key cytokines such as IL6, CSF1, and CSF2, which are crucial for MDSC differentiation and recruitment. By reducing PD-L1 expression and modulating the immunosuppressive TME, CCS1477 creates a more favorable environment for tumor-infiltrating lymphocytes, significantly enhancing the efficacy of immune checkpoint blockade (ICB) therapy. Notably, these effects were observed in both prostate cancer and melanoma models, underscoring the broad therapeutic potential of p300/CBP bromodomain inhibition in improving ICB outcomes.

Research status and frontiers in liver cancer immunotherapy: a bibliometric perspective on highly cited literature

Background

Liver cancer is one of the major causes of cancer-related death in the world. As a breakthrough therapy, immunotherapy had significantly improved the prognosis of patients. However, the current research status and research hotspots in the field of liver cancer immunotherapy still lack systematic review. Based on the bibliometric analysis of highly cited papers, this study intended to reveal the current research status, research hotspots and future research trends in this field.

Objective

The purpose of this study was to analyze the national/regional contributions, authors and institutions cooperation network, keywords clustering and keywords burst analysis of highly cited papers on liver cancer immunotherapy through bibliometrics, so as to clarify the research frontier and development direction, and provide objective data support for future research direction and clinical practice.

Methods

The highly cited papers on liver cancer immunotherapy from the Web of Science core collection up to February 23, 2025 were retrieved, and 232 studies were included. CiteSpace was used to build a knowledge map, analyze the distribution of years, countries, authors, institutions and cooperation networks, and identify research hotspots and emerging trends through keyword clustering and burst detection.

Results

The number of highly cited papers continued to increase from 2014 and reached a peak in 2022. China and the United States had the highest number of publications and the centrality of cooperation networks. The author with the highest number of papers was Llovet, Josep M, whose research direction mainly focused on immune checkpoint inhibitor combination therapy and molecular typing. The author with the highest cooperation network centrality was Duda, Dan G, whose research team focused on tumor microenvironment regulation. Harvard University and the University of Barcelona played an important central role in the institutional collaboration. Keywords analysis showed that immune checkpoint inhibitors, tumor microenvironment and combination therapy were the core of liver cancer immunotherapy. Burst keywords such as cell lung cancer, pembrolizumab, advanced melanoma, blockade, lymphocytes, etc. had revealed the research frontier of liver cancer immunotherapy research.

Conclusion

The research on liver cancer immunotherapy had made multi-dimensional progress, with China and the United States leading the global cooperation. The main research directions were the combination strategy of immunization, the regulation of tumor microenvironment and the exploration of novel targets. In the future, it is necessary to optimize treatment resistance solutions, integrate interdisciplinary resources, and promote the development of precision and personalized treatment.

RNF2 induces myeloid-derived suppressor cells chemotaxis and promotes hepatocellular carcinoma progression through the TRAF2-NF-κB signaling axis

RING finger protein 2 (RNF2) has been shown to promote tumor growth in various cancer types. However, the immune regulatory function of RNF2 in the tumor microenvironment is unclear. Here, we report that upregulation of RNF2 is positively correlated with the tumor burden and poor prognosis in hepatocellular carcinoma patients and fosters an immunosuppressive microenvironment with increased MDSCs recruitment, and reduced T cell activation. Mechanistically, RNF2 binds with TRAF2 and directly mediates K63-linked TRAF2 ubiquitination. This modification of TRAF2 enables NF-κB hyperactivation in tumor cells, which subsequently induces CXCL1 transcription to enhance MDSCs migration. Furthermore, RNF2 knockout improves responsiveness to anti-PD-1 therapy in immunocompetent mice, as evidenced by enhancing infiltration of CD8+T cells into the tumor and a reduction in MDSC levels. Collectively, our experiments support that perturbing RNF2 and targeting MDSCs may afford therapeutic opportunities for hepatocellular carcinoma interception and prevention.

Myeloid-Derived Suppressor Cells: Implications in Cancer Immunology and Immunotherapy

Myeloid-derived suppressor cells (MDSCs) are believed to be key promoters of tumor development and are recognized as a hallmark of cancer cells' ability to evade the immune system evasion. MDSC levels often increase in peripheral blood and the tumor microenvironment (TME). These cells exert immunosuppressive functions, weakening the anticancer immune surveillance system, in part by repressing T-cell immunity. Moreover, MDSCs may promote tumor progression and interact with cancer cells, increasing MDSC expansion and favoring an immunotolerant TME. This review analyzes the primary roles of MDSCs in cancer and T-cell immunity, discusses the urgent need to develop effective MDSC-targeted therapies, and highlights the potential synergistic combination of MDSC targeting with chimeric antigen receptors and immune checkpoint inhibitors.

Understanding pre-metastatic niche formation: implications for colorectal cancer liver metastasis

The liver is the most commonly metastasized organ in colorectal cancer (CRC), and distant metastasis is the primary cause of mortality from CRC. In recent years, researchers have discovered that tumor cells create a "pre-metastatic niche (PMN)" favorable to metastasis before reaching the metastatic location. This review discusses the many processes and mechanisms that lead to PMN formation in CRC, including gut microbiota, stem cell stimulation, immunocyte interactions, and the induction of extracellular vesicles that carry important information. It examines research methods and diagnostic and therapeutic approaches for treating metastatic CRC with PMN. The crucial significance of PMN formation in metastatic CRC is also highlighted.

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.

The colorectal cancer microenvironment: Preclinical progress in identifying targets for cancer therapy

Colorectal cancer (CRC) is a common cancer with high mortality rates. Despite progress in treatment, it remains an incurable disease for many patients. In CRC, the tumor microenvironment (TME) plays critical roles in tumor growth, progression, patients' prognosis, and response to treatments. Understanding TME complexities is important for developing effective therapies. In vitro and in vivo preclinical models are critical in understanding the disease, discovering potential targets, and developing effective therapeutics. In this review, we focus on preclinical research studies associated with modulation of the TME in CRC. These models give insights into understanding the role of stroma and immune cell components of the TME in CRC and improve clinical responses, providing insights in novel treatment options. Various studies have focused on targeting the TME in CRC to improve responses to different therapeutic approaches. These include identifying targets for cancer therapies, targeting molecular signaling, and enhancing the efficacy of immunotherapeutic modalities. Furthermore, targeting stromal and angiogenic factors in the TME may provide new therapeutic options. Overall, understanding and targeting the TME in CRC is a promising approach for improving therapeutic outcomes.

Myeloid-derived suppressor cells in metabolic and cardiovascular disorders

Dysregulation of immune homeostasis can precipitate chronic inflammation, thus significantly contributing to the onset and progression of metabolic and cardiovascular diseases. Myeloid-derived suppressor cells (MDSCs) constitute a heterogeneous population of immature myeloid cells that are mobilized in response to biological stressors such as tissue damage and inflammation. Although MDSCs have been extensively characterized in the contexts of cancer and infectious diseases, emerging evidence highlights their pivotal roles in the pathophysiology of metabolic and cardiovascular disorders. We discuss growing evidence for the involvement of MDSCs in the progression of metabolic and cardiovascular diseases, with the aim of deepening our understanding of MDSCs in cardiometabolic physiology and identifying the necessary steps for the development of innovative MDSC-targeted therapeutic strategies.

Breast Cancer and Tumor Microenvironment: The Crucial Role of Immune Cells

Breast cancer is the most common type of cancer in women and the second leading cause of death by cancer. Despite recent advances, the mortality rate remains high, underlining the need to develop new therapeutic approaches. The complex interaction between cancer cells and the tumor microenvironment (TME) is crucial in determining tumor progression, therapy response, and patient prognosis. Understanding the role of immune cells in carcinogenesis and tumor progression can help improve targeted therapeutic options, increasing the likelihood of a favorable prognosis. Therefore, this review aims to critically analyze the complex interaction between tumor cells and immune cells, emphasizing the clinical and therapeutic implications. Additionally, we explore advances in immunotherapies, with a focus on immune checkpoint inhibitors.

Unravelling the role of ubiquitin-specific proteases in breast carcinoma: insights into tumour progression and immune microenvironment modulation

Breast cancer is a prevalent malignancy worldwide, and its treatment has increasingly shifted towards precision medicine, with immunotherapy emerging as a key therapeutic strategy. Deubiquitination, an essential epigenetic modification, is regulated by deubiquitinating enzymes (DUBs) and plays a critical role in immune function and tumor progression. Ubiquitin-specific proteases (USPs), a prominent subgroup of DUBs, are involved in regulating immune cell functions, antigen processing, and T cell development in the context of breast cancer. Certain USPs also modulate the differentiation of immune cells, such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), within the breast cancer immune microenvironment. Furthermore, several USPs influence the expression of PD-L1, thus affecting the efficacy of immune checkpoint inhibitors. The overexpression of USPs may promote immune evasion, contributing to the development of treatment resistance. This review elucidates the role of USPs in modulating the immune microenvironment and immune responses in breast cancer. Additionally, it discusses effective strategies for combining USP inhibitors with other therapeutic agents to enhance treatment outcomes. Therefore, targeting USPs presents the potential to enhance the efficacy of immunotherapy and overcome drug resistance, offering a more effective treatment strategy for breast cancer patients.

Frontiers in pancreatic cancer on biomarkers, microenvironment, and immunotherapy

Pancreatic cancer remains one of the most challenging malignancies to treat due to its late-stage diagnosis, aggressive progression, and high resistance to existing therapies. This review examines the latest advancements in early detection, and therapeutic strategies, with a focus on emerging biomarkers, tumor microenvironment (TME) modulation, and the integration of artificial intelligence (AI) in data analysis. We highlight promising biomarkers, including microRNAs (miRNAs) and circulating tumor DNA (ctDNA), that offer enhanced sensitivity and specificity for early-stage diagnosis when combined with multi-omics panels. A detailed analysis of the TME reveals how components such as cancer-associated fibroblasts (CAFs), immune cells, and the extracellular matrix (ECM) contribute to therapy resistance by creating immunosuppressive barriers. We also discuss therapeutic interventions that target these TME components, aiming to improve drug delivery and overcome immune evasion. Furthermore, AI-driven analyses are explored for their potential to interpret complex multi-omics data, enabling personalized treatment strategies and real-time monitoring of treatment response. We conclude by identifying key areas for future research, including the clinical validation of biomarkers, regulatory frameworks for AI applications, and equitable access to innovative therapies. This comprehensive approach underscores the need for integrated, personalized strategies to improve outcomes in pancreatic cancer.

Chimeric Antigen Receptor Cell Therapy: Empowering Treatment Strategies for Solid Tumors

Chimeric antigen receptor-T (CAR-T) cell therapy has demonstrated impressive efficacy in the treatment of blood cancers; however, its effectiveness against solid tumors has been significantly limited. The differences arise from a range of difficulties linked to solid tumors, including an unfriendly tumor microenvironment, variability within the tumors, and barriers to CAR-T cell infiltration and longevity at the tumor location. Research shows that the reasons for the decreased effectiveness of CAR-T cells in treating solid tumors are not well understood, highlighting the ongoing need for strategies to address these challenges. Current strategies frequently incorporate combinatorial therapies designed to boost CAR-T cell functionality and enhance their capacity to effectively target solid tumors. However, these strategies remain in the testing phase and necessitate additional validation to assess their potential benefits. CAR-NK (natural killer), CAR-iNKT (invariant natural killer T), and CAR-M (macrophage) cell therapies are emerging as promising strategies for the treatment of solid tumors. Recent studies highlight the construction and optimization of CAR-NK cells, emphasizing their potential to overcome the unique challenges posed by the solid tumor microenvironment, such as hypoxia and metabolic barriers. This review focuses on CAR cell therapy in the treatment of solid tumors.

Harnessing the tumor microenvironment: targeted cancer therapies through modulation of epithelial-mesenchymal transition

The tumor microenvironment (TME) is integral to cancer progression, impacting metastasis and treatment response. It consists of diverse cell types, extracellular matrix components, and signaling molecules that interact to promote tumor growth and therapeutic resistance. Elucidating the intricate interactions between cancer cells and the TME is crucial in understanding cancer progression and therapeutic challenges. A critical process induced by TME signaling is the epithelial-mesenchymal transition (EMT), wherein epithelial cells acquire mesenchymal traits, which enhance their motility and invasiveness and promote metastasis and cancer progression. By targeting various components of the TME, novel investigational strategies aim to disrupt the TME's contribution to the EMT, thereby improving treatment efficacy, addressing therapeutic resistance, and offering a nuanced approach to cancer therapy. This review scrutinizes the key players in the TME and the TME's contribution to the EMT, emphasizing avenues to therapeutically disrupt the interactions between the various TME components. Moreover, the article discusses the TME's implications for resistance mechanisms and highlights the current therapeutic strategies toward TME modulation along with potential caveats.

Leveraging Single-Cell Multi-Omics to Decode Tumor Microenvironment Diversity and Therapeutic Resistance

Recent developments in single-cell multi-omics technologies have provided the ability to identify diverse cell types and decipher key components of the tumor microenvironment (TME), leading to important advancements toward a much deeper understanding of how tumor microenvironment heterogeneity contributes to cancer progression and therapeutic resistance. These technologies are able to integrate data from molecular genomic, transcriptomic, proteomics, and metabolomics studies of cells at a single-cell resolution scale that give rise to the full cellular and molecular complexity in the TME. Understanding the complex and sometimes reciprocal relationships among cancer cells, CAFs, immune cells, and ECs has led to novel insights into their immense heterogeneity in functions, which can have important consequences on tumor behavior. In-depth studies have uncovered immune evasion mechanisms, including the exhaustion of T cells and metabolic reprogramming in response to hypoxia from cancer cells. Single-cell multi-omics also revealed resistance mechanisms, such as stromal cell-secreted factors and physical barriers in the extracellular matrix. Future studies examining specific metabolic pathways and targeting approaches to reduce the heterogeneity in the TME will likely lead to better outcomes with immunotherapies, drug delivery, etc., for cancer treatments. Future studies will incorporate multi-omics data, spatial relationships in tumor micro-environments, and their translation into personalized cancer therapies. This review emphasizes how single-cell multi-omics can provide insights into the cellular and molecular heterogeneity of the TME, revealing immune evasion mechanisms, metabolic reprogramming, and stromal cell influences. These insights aim to guide the development of personalized and targeted cancer therapies, highlighting the role of TME diversity in shaping tumor behavior and treatment outcomes.

Optimising CAR T therapy for the treatment of solid tumors

INTRODUCTION

Adoptive immunotherapy using chimeric antigen receptor (CAR)-engineered T cells has proven transformative in the management of B cell and plasma cel derived malignancies. However, solid tumors have largely proven to be resistant to this therapeutic modality. Challenges include the paucity of safe target antigens, heterogeneity of target expression within the tumor, difficulty in delivery of CAR T cells to the site of disease, poor penetration within solid tumor deposits and inability to circumvent the array of immunosuppressive and biophysical barriers imposed by the solid tumor microenvironment.

AREAS COVERED

Literature was reviewed on the PubMed database, excluding occasional papers which were not available as open access publications or through other means.

EXPERT OPINION

Here, we have surveyed the large body of technological advances that have been made in the quest to bridge the gap toward successful deployment of CAR T cells for the treatment of solid tumors. These encompass the development of more sophisticated targeting strategies to engage solid tumor cells safely and comprehensively, improved drug delivery solutions, design of novel CAR architectures that achieve improved functional persistence and which resist physical, chemical and biological hurdles present in tumor deposits. Prospects for combination therapies that incorporate CAR T cells are also considered.

Nanobodies as innovative immune checkpoint modulators: advancing cancer immunotherapy

The immune system relies on a delicate balance between attacking harmful pathogens and preserving the body's own tissues, a balance maintained by immune checkpoints. These checkpoints play a critical role in preventing autoimmune diseases by restraining excessive immune responses while allowing the immune system to recognize and destroy abnormal cells, such as tumors. In recent years, immune checkpoint inhibitors (ICIs) have become central to cancer therapy, enabling the immune system to target and eliminate cancer cells that evade detection. Traditional antibodies, such as IgGs, have been widely used in immune therapies but are limited by their size and complexity. Nanobodies (Nbs), derived from camelid heavy-chain-only antibodies, offer a promising alternative. These small, stable antibody fragments retain the antigen-binding specificity of traditional antibodies but have enhanced solubility and the ability to target otherwise inaccessible epitopes. This review explores the use of Nbs as ICIs, emphasizing their potential in cancer immunotherapy and other immune-related treatments. Their unique structural properties and small size make Nbs highly effective tools for modulating immune responses, representing a novel approach in the evolving landscape of checkpoint inhibitor therapies.

The Emerging Role of Schwann Cells in the Tumor Immune Microenvironment and Its Potential Clinical Application

As the primary glial cells in the peripheral nervous system (PNS), Schwann cells (SCs) have been proven to influence the behavior of cancer cells profoundly and are involved in cancer progression through extensive interactions with cancer cells and other stromal cells. Indeed, the tumor microenvironment (TME) is a critical factor that can significantly limit the efficacy of immunotherapeutic approaches. The TME promotes tumor progression in part by reshaping an immunosuppressive state. The immunosuppressive TME is the result of the crosstalk between the tumor cells and the different immune cell subsets, including macrophages, natural killer (NK) cells, dendritic cells (DCs), lymphocytes, myeloid-derived suppressor cells (MDSCs), etc. They are closely related to the anti-tumor immune status and the clinical prognosis of cancer patients. Increasing research demonstrates that SCs influence these immune cells and reshape the formation of the immunosuppressive TME via the secretion of various cytokines, chemokines, and other effector molecules, eventually facilitating immune evasion and tumor progression. In this review, we summarize the SC reprogramming in TME, the emerging role of SCs in tumor immune microenvironment, and the underlying mechanisms involved. We also discuss the possible therapeutic strategies to selectively target SCs, providing insights and perspectives for future research and clinical studies involving SC-targeted treatment.

Targeting Cancer: Microenvironment and Immunotherapy Innovations

In 2024, the United States was projected to experience 2 million new cancer diagnoses and approximately 611,720 cancer-related deaths, reflecting a broader global trend in which cancer cases are anticipated to exceed 35 million by 2050. This increasing burden highlights ongoing challenges in cancer treatment despite significant advances that have reduced cancer mortality by 31% since 1991. Key obstacles include the disease's inherent heterogeneity and complexity, such as treatment resistance, cancer stem cells, and the multifaceted tumor microenvironment (TME). The TME-comprising various tumor and immune cells, blood vessels, and biochemical factors-plays a crucial role in tumor growth and resistance to therapies. Recent innovations in cancer treatment, particularly in the field of immuno-oncology, have leveraged insights into TME interactions. An emerging example is the FDA-approved therapy using tumor-infiltrating lymphocytes (TILs), demonstrating the potential of cell-based approaches in solid tumors. However, TIL therapy is just one of many strategies being explored. This review provides a comprehensive overview of the emerging field of immuno-oncology, focusing on how novel therapies targeting or harnessing components of the TME could enhance treatment efficacy and address persistent challenges in cancer care.

NK/DC crosstalk-modulating antitumor activity via Sema3E/PlexinD1 axis for enhanced cancer immunotherapy

The complex relationship between natural killer (NK) cells and dendritic cells (DCs) within the tumor microenvironment significantly impacts the success of cancer immunotherapy. Recent advancements in cancer treatment have sought to bolster innate and adaptive immune responses through diverse modalities, aiming to tilt the immune equilibrium toward tumor elimination. Optimal antitumor immunity entails a multifaceted interplay involving NK cells, T cells and DCs, orchestrating immune effector functions. Although DC-based vaccines and NK cells' cytotoxic capabilities hold substantial therapeutic potential, their interaction is frequently hindered by immunosuppressive elements such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells. Chemokines and cytokines, such as CXCL12, CCL2, interferons, and interleukins, play crucial roles in modulating NK/DC interactions and enhancing immune responses. This review elucidates the mechanisms underlying NK/DC interaction, emphasizing their pivotal roles in augmenting antitumor immune responses and the impediments posed by tumor-induced immunosuppression. Furthermore, it explores the therapeutic prospects of restoring NK/DC crosstalk, highlighting the significance of molecules like Sema3E/PlexinD1 in this context, offering potential avenues for enhancing the effectiveness of current immunotherapeutic strategies and advancing cancer treatment paradigms. Harnessing the dynamic interplay between NK and DC cells, including the modulation of Sema3E/PlexinD1 signaling, holds promise for developing more potent therapies that harness the immune system's full potential in combating cancer.

Overcoming immunosuppression in cancer: how ketogenic diets boost immune checkpoint blockade

Immune checkpoint blockade (ICB) is now part of the standard of care in the treatment of many forms of cancer, yet it lacks efficacy in some patients, necessitating adjunct therapies to support the anti-tumor immune response. Ketogenic diets (KDs), i.e., high-fat low-carbohydrate diets, have been shown to have antiproliferative and immunomodulatory effects in various preclinical cancer studies. Here, we review current knowledge of the complex interplay of KDs and the anti-tumor immune response in the context of ICB therapy, to update our understanding of diet-induced immunometabolic reprogramming in cancer. Preclinical cancer studies have revealed increased activation of and infiltration by tumor-fighting immune cells, especially CD8+ T cells, but also M1 macrophages and natural killer cells, in response to a KD regimen. In contrast, immune-suppressive cells such as regulatory CD4+ T lymphocytes, M2 macrophages, and myeloid-derived suppressor cells were reported to be decreased or largely unaffected in tumors of KD-fed mice. KDs also showed synergism with ICB therapy in several preclinical tumor studies. The observed effects are ascribed to the ability of KDs to improve immune cell infiltration and induce downregulation of immune-inhibitory processes, thus creating a more immunogenic tumor microenvironment. The studies reviewed herein show that altering the metabolic composition of the tumor microenvironment by a KD can boost the anti-tumor immune response and diminish even immunotherapy-resistant as well as immunologically "cold" tumors. However, the exact underlying mechanisms remain to be elucidated, requiring further studies before KDs can be successfully implemented as an adjunct tumor therapy to improve survival rates for cancer patients.

Targeted modulation of myeloid-derived suppressor cells in the tumor microenvironment: Implications for cancer therapy

Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells originating from the bone marrow, known for their potent immunosuppressive functions that contribute to tumor immune evasion and progression. This paper provides a comprehensive analysis of the multifaceted interactions between MDSCs and tumors, exploring their distinct phenotypes and immunosuppressive mechanisms. Key roles of MDSCs in tumor biology are discussed, including their involvement in the formation of the pre-metastatic niche, facilitation of angiogenesis, enhancement of vascular permeability, suppression of tumor cell apoptosis, and promotion of resistance to cancer therapies. Additionally, the review highlights recent advances in the development of MDSC-targeting therapies, with a focus on their potential to enhance anti-tumor immunity. The therapeutic potential of Traditional Chinese Medicine (TCM) in modulating MDSC quantity and function is also explored, suggesting a novel approach to cancer treatment by integrating traditional and modern therapeutic strategies.

The NF-κB1/p50 Subunit Influences the Notch/IL-6-Driven Expansion of Myeloid-Derived Suppressor Cells in Murine T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia is an aggressive neoplasia due to hyper-proliferation of lymphoid progenitors and lacking a definitive cure to date. Notch-activating mutations are the most common in driving disease onset and progression, often in combination with sustained activity of NF-κB. Myeloid-derived suppressor cells represent a mixed population of immature progenitors exerting suppression of anti-cancer immune responses in the tumor microenvironment of many malignancies. We recently reported that in a transgenic murine model of Notch3-dependent T-cell acute lymphoblastic leukemia there is an accumulation of myeloid-derived suppressor cells, dependent on both Notch signaling deregulation and IL-6 production inside tumor T-cells. However, possible interaction between NF-κB and Notch in this context remains unexplored. Interestingly, we also reported that Notch3 transgenic and NF-κB1/p50 deleted double mutant mice display massive myeloproliferation. Here, we demonstrated that the absence of the p50 subunit in these mice dramatically enhances the induction and suppressive function of myeloid-derived suppressor cells. This runs in parallel with an impressive increase in IL-6 concentration in the peripheral blood serum, depending on IL-6 hyper-production by tumor T-cells from double mutant mice. Mechanistically, IL-6 increase relies on loss of the negative control exerted by the p50 subunit on the IL-6 promoter. Our results reveal the Notch/NF-κB cross-talk in regulating myeloid-derived suppressor cell biology in T-cell leukemia, highlighting the need to consider carefully the pleiotropic effects of NF-κB-based therapy on the tumor microenvironment.

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.

Recent Treatment Strategies and Molecular Pathways in Resistance Mechanisms of Antiangiogenic Therapies in Glioblastoma

Malignant gliomas present great difficulties in treatment, with little change over the past 30 years in the median survival time of 15 months. Current treatment options include surgery, radiotherapy (RT), and chemotherapy. New therapies aimed at suppressing the formation of new vasculature (antiangiogenic treatments) or destroying formed tumor vasculature (vascular disrupting agents) show promise. This study summarizes the existing knowledge regarding the processes by which glioblastoma (GBM) tumors acquire resistance to antiangiogenic treatments. The discussion encompasses the activation of redundant proangiogenic pathways, heightened tumor cell invasion and metastasis, resistance induced by hypoxia, creation of vascular mimicry channels, and regulation of the tumor immune microenvironment. Subsequently, we explore potential strategies to overcome this resistance, such as combining antiangiogenic therapies with other treatment methods, personalizing treatments for each patient, focusing on new therapeutic targets, incorporating immunotherapy, and utilizing drug delivery systems based on nanoparticles. Additionally, we would like to discuss the limitations of existing methods and potential future directions to enhance the beneficial effects of antiangiogenic treatments for patients with GBM. Therefore, this review aims to enhance the research outcome for GBM and provide a more promising opportunity by thoroughly exploring the mechanisms of resistance and investigating novel therapeutic strategies.

Unveiling the Dynamic Interplay between Cancer Stem Cells and the Tumor Microenvironment in Melanoma: Implications for Novel Therapeutic Strategies

Cutaneous melanoma still represents a significant health burden worldwide, being responsible for the majority of skin cancer deaths. Key advances in therapeutic strategies have significantly improved patient outcomes; however, most patients experience drug resistance and tumor relapse. Cancer stem cells (CSCs) are a small subpopulation of cells in different tumors, including melanoma, endowed with distinctive capacities of self-renewal and differentiation into bulk tumor cells. Melanoma CSCs are characterized by the expression of specific biomarkers and intracellular pathways; moreover, they play a pivotal role in tumor onset, progression and drug resistance. In recent years, great efforts have been made to dissect the molecular mechanisms underlying the protumor activities of melanoma CSCs to provide the basis for novel CSC-targeted therapies. Herein, we highlight the intricate crosstalk between melanoma CSCs and bystander cells in the tumor microenvironment (TME), including immune cells, endothelial cells and cancer-associated fibroblasts (CAFs), and its role in melanoma progression. Specifically, we discuss the peculiar capacities of melanoma CSCs to escape the host immune surveillance, to recruit immunosuppressive cells and to educate immune cells toward an immunosuppressive and protumor phenotype. We also address currently investigated CSC-targeted strategies that could pave the way for new promising therapeutic approaches for melanoma care.

Dual roles of myeloid-derived suppressor cells in various diseases: a review

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that originate from bone marrow stem cells. In pathological conditions, such as autoimmune disorders, allergies, infections, and cancer, normal myelopoiesis is altered to facilitate the formation of MDSCs. MDSCs were first shown to promote cancer initiation and progression by immunosuppression with the assistance of various chemokines and cytokines. Recently, various studies have demonstrated that MDSCs play two distinct roles depending on the physiological and pathological conditions. MDSCs have protective roles in autoimmune disorders (such as uveoretinitis, multiple sclerosis, rheumatoid arthritis, ankylosing spondylitis, type 1 diabetes, autoimmune hepatitis, inflammatory bowel disease, alopecia areata, and systemic lupus erythematosus), allergies, and organ transplantation. However, they play negative roles in infections and various cancers. Several immunosuppressive functions and mechanisms of MDSCs have been determined in different disease conditions. This review comprehensively discusses the associations between MDSCs and various pathological conditions and briefly describes therapeutic approaches.