Reactive Oxygen Species as Regulators of MDSC-Mediated Immune Suppression

Self-regulating immunosuppressive tumor microenvironment by NIR-II photothermal agent with anti-inflammatory activity for self-reinforcing immunotherapy synergy with cancer photothermal ablation

Cancer thermal immunotherapeutic strategy has garnered tremendous attention in nanomedicine frontier. Photothermal therapy (PTT) within the second near-infrared (NIR-II) window is popular hyperthermia technique, but the effect of NIR-II PTT on antitumor immunity remains extensive exploration. Here, we first reveal the inflammatory immunosuppressive tumor microenvironment (TME) characterized by high-influx of myeloid-derived suppressor cells (MDSCs) following NIR-II PTT. For this issue, we develop biomineralized copper sulfide nanoparticles (BCS NPs) as NIR-II photothermal agents (PTAs), and found for the first time that they are superior electron-donor antioxidants with pronounced anti-inflammatory activities. Impressively, the excessive inflammation triggered by BCS NPs-mediated NIR-II PTT can be self-alleviated to minimize the high-influx of MDSCs, and the immunosuppression-related reactive oxygen species produced by MDSCs can also be self-scavenged. Such reprogramming of TME facilitates the activation of systemic adaptive antitumor immunity and the strengthened tumour-infiltrating of cytotoxic T lymphocytes, thereby realizing self-reinforcing immunotherapy synergy with cancer NIR-II PTT. More importantly, a robust abscopal effect against distant tumors is also observed in bilateral tumor models. This work provides the first example to underscore the potential of PTAs with antioxidant and anti-inflammatory functions as innovative thermal immuno-nanomedicines.

Advances in research on flavonoids in tumor immunotherapy (Review)

Cancer immunotherapy is an approach used in anti‑tumor treatment; however, its efficacy is limited to specific tumor types that are inherently sensitive to immune system modulation. Expanding the scope of indications and enhancing the efficacy of cancer immunotherapy are key goals for continued advancement. Flavonoids modulate the tumor‑immunosuppressive microenvironment. Integrating flavonoids with immunotherapeutic modalities, including cancer vaccines, immune checkpoint inhibitors and adoptive immune‑cell therapy, has potential in terms of augmenting the therapeutic efficacy of immunotherapy. The present review aimed to summarize flavonoids that enhance cancer immunotherapy, focusing on their underlying mechanisms and the application of nanotechnology to overcome inherent limitations such as poor solubility, low bioavailability, rapid metabolism, and instability under physiological conditions, thereby highlighting the potential of flavonoids in advancing cancer immunotherapy.

Comprehensive analysis of breast cancer oxidative stress related gene signature: a combination of bulk and single-cell RNA sequencing analysis

Oxidative stress influences the tumor microenvironment, driving breast cancer progression and drug resistance. This study aimed to develop a prognostic gene signature based on oxidative stress-related genes (OSRGs) to assess patient outcomes and immune status. UCSC Xena ( http://xena.ucsc.edu/ ) and GEO ( https://www.ncbi.nlm.nih.gov/geo/ ) databases were used to obtain RNA-seq data and corresponding clinical information. The classification of OSRG subtypes was performed using consensus cluster. The oxidative stress related scoring (OSRS) model was established combining Lasso regression and multivariable Cox regression. The analysis of tumor mutation burden (TMB) and somatic mutation were carried out using the R package 'maftools'. Python package 'pySCENIC' was used to construct and analyze the transcription factor network. Additionally, immune infiltration was analyzed using R packages 'CIBERSORT' and 'ESTIMATE'. Three OSRG subgroups were identified and the Differentially Expressed Genes (DEGs) among them were enriched in humoral immunity, cytokine communication and drug metabolism pathways. OSRS model was established based on the DEGs and revealed association with patients' overall survival, somatic mutations, immune statuses, and drug resistance. Finally, transcription factor TFAP2B was identified as a key regulatory factor in high OSRS cells, and associated with a negative prognostic outcome in Basal-like breast cancer patients.

Glucocorticoid Receptor-Targeted Nanoliposome for STAT3 Inhibition-Led Myeloid-Derived Suppressor Cell Modulation and Efficient Colon Cancer Treatment

STAT3 is an important protein responsible for cellular proliferation, motility, and immune tolerance and is hyperactive in colorectal cancer, instigating metastasis, cellular proliferation, migration, as well as inhibition. It helps in proliferation of myeloid-derived suppressor cells (MDSCs), which within the tumor microenvironment (TME) suppress T cells to encourage tumor growth, metastasis, and resistance to immunotherapy, besides playing dynamic role in regulating macrophages within the tumor. Thus, MDSC is a potential target to augment immune surveillance within the TME. Herein, we report targeting both colorectal cancer and MDSCs using a glucocorticoid receptor (GR)-targeted nanoliposomal formulation carrying GR-ligand, dexamethasone (Dex), and a STAT3 inhibitor, niclosamide (N). Our main objective was to selectively inhibit STAT3, the key immunomodulatory factor in most TME-associated cells including MDSCs, and also repurpose the use of this antihelminthic, low-cost drug N for cancer treatment. The resultant formulation D1XN exhibited better tumor regression and survivability compared to GR nontargeted formulation. Further, bone marrow cell-derived MDSCs were engineered by D1XN treatment ex vivo and were inoculated back to tumor-bearing mice. Significant tumor growth inhibition with enhanced antiproliferative immune cell signatures, such as T cell infiltration, decrease in Treg cells, and increased M1/M2 macrophage ratio within the TME were observed. This reveals the effectiveness of engineered MDSCs to modulate tumor surveillance besides reversing the aggressiveness of the tumor. Therefore, D1XN and D1XN-mediated engineered MDSCs alone or in combination can be considered as potent selective chemo-immunotherapeutic nanoliposomal agent(s) against colorectal cancer.

MiR- 150 deletion promotes lung tumor growth by upregulating P-STAT3 and ROS in MDSCs

Lung cancer is the second most common cancer in the world. Myeloid-derived suppressor cells (MDSCs) are important cell populations in the microenvironment of lung cancer, which affects the development and treatment of lung cancer. A large number of studies have shown that miRNA can regulate MDSCs, promoting tumor development. Here we aim to explore the role of miR- 150 on MDSCs in lung tumors. We established lung tumor models by injecting miR- 150 knock-out (miR- 150 KO) mice with LLC subcutaneously. MiR- 150 deletion promoted tumor growth and increased the ratio of MDSCs in tumors. In addition, knockdown of miR- 150 resulted in high serum levels of IL- 6 and G-CSF and promoted the expression of suppressive-associated molecules in MDSCs. In vitro, inhibition of miR- 150 led to increased expression of ROS, IRE1α and P-STAT3 in MDSCs. In vivo administration of STAT3 inhibitor significantly inhibited tumor growth in miR- 150 KO mice and reduced ROS level in tumor MDSCs. Our results indicated that miR- 150 deletion promotes lung tumor growth by upregulating P-STAT3 and ROS in MDSCs, suggesting that STAT3 inhibitors are effective in blocking the production of ROS in MDSCs lacking miR- 150.

Single-cell transcriptomic analysis identified resistant MDSCs and a stress-tolerant gene co-expression network as common MDSC features across multiple disease settings

Background

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immunosuppressive myeloid cells. The identification of a molecular signature common to MDSC regardless of tissue source would aid in the classification of cells as MDSCs.

Methods

Single-cell RNA sequencing (scRNA-seq) was performed on GM-CSF+ IL-6-induced human MDSCs to characterize the extent of heterogeneity within monocytic MDSCs (M-MDSCs). Cytokine-treated PBMCs were also cultured in the absence of serum to include an additional element of cell stress. Independent published bulk and single-cell transcriptomic datasets were used for validation.

Findings

A cluster of cells with preserved MDSC features was induced by the combination of inflammatory signals and cell stress in the form of serum starvation (resistant MDSCs, rMDSCs). A gene co-expression module (the yellow module) was identified specific to rMDSCs. The genes upregulated in MDSCs can be further classified into stress-tolerant vs. -sensitive features. This yellow module mostly contained stress-tolerant genes and showed excellent separation for distinguishing M-MDSCs from control cells across a range of in vitro and in vivo conditions (ROC AUC = 0.954), a feature not found in the stress-sensitive genes. Importantly, rMDSCs were identified in scRNA-seq datasets of immune cells from multiple human cancer types. Tumor C1Q macrophages, which have been associated with immunosuppression, highly expressed the yellow module gene signature.

Interpretation

These results demonstrate the importance of the combined roles of inflammation and cellular stress in shaping the features of M-MDSCs and highlight cellular resilience represented by rMDSCs and the role of stress-tolerant features in defining common MDSC features.

Unraveling the Complexities of Myeloid-Derived Suppressor Cells in Inflammatory Bowel Disease

Myeloid-derived suppressor cells (MDSCs) regulate immune responses in many pathological conditions, one of which is inflammatory bowel disease (IBD), an incurable chronic disorder of the digestive tract and beyond. The pathophysiology of IBD remains unclear, likely involving aberrant innate and adaptive immunity. Studies have reported altered population of MDSCs in patients with IBD. However, their distribution varies among patients and different preclinical models of IBD. The expansion and activation of MDSCs are likely driven by various stimuli during intestinal inflammation, but the in-depth mechanisms remain poorly understood. The role of MDSCs in the pathogenesis of IBD appears to be paradoxical. In addition to intestinal inflammation, suppressive MDSCs may promote colitis-to-colon cancer transition. In this Review, we summarize recent progresses on the features, activation, and roles of MDSCs in the development of IBD and IBD-associated colon cancer.

MDSC checkpoint blockade therapy: a new breakthrough point overcoming immunosuppression in cancer immunotherapy

Despite the success of cancer immunotherapy in treating hematologic malignancies, their efficacy in solid tumors remains limited due to the immunosuppressive tumor microenvironment (TME), which is mainly formed by myeloid-derived suppressor cells (MDSCs). MDSCs not only exert potent immunosuppressive effects that hinder the success of immune checkpoint inhibitors (ICIs) and adaptive cellular therapies, but they also promote tumor advancement through non-immunological pathways, including promoting angiogenesis, driving epithelial-mesenchymal transition (EMT), and contributing to the establishment of pre-metastatic environments. While targeting MDSCs alone or in combination with conventional therapies has shown limited success, emerging evidence suggests that MDSC checkpoint blockade in combination with other immunotherapies holds great promise in overcoming both immunological and non-immunological barriers. In this review, we discussed the dual roles of MDSCs, with a particular emphasis on their underexplored checkpoints blockade strategies. We discussed the rationale behind combination strategies, their potential advantages in overcoming MDSC-mediated immunosuppression, and the challenges associated with their development. Additionally, we highlight future research directions aimed at optimizing combination immunotherapies to enhance cancer therapeutic effectiveness, particularly in solid tumor therapies where MDSCs are highly prevalent.

Amplifying glioblastoma immunotherapy: T cell shielding through Nitric oxide/reactive oxygen species scavenging nanoparticles Potentiates anti-PD-1

Despite the success of immune checkpoint blockade (ICB) therapy in various cancers, its efficacy faces challenges in glioblastoma (GBM) due to the immunosuppressive cold-tumor microenvironment. The scarcity of tumor-infiltrating T cells and the suppression of T cell activity significantly limit therapeutic outcomes in GBM. Nitric oxide (NO) and reactive oxygen species (ROS) from tumor-associated myeloid cells (TAMCs) are key contributors to T cell suppression, reducing ICB therapy effectiveness. In this study, we developed NO-ROS scavenging micelles that effectively scavenge both NO and ROS, protecting T cells from their exhausting effects. This leads to a significant increase in T cell infiltration and activation. Moreover, when combined with αPD-1, the survival rate increases to 40 % up to 120 days, enhancing therapeutic efficacy compared to αPD-1 alone. This approach not only protects T cells from the inhibitory effects of NO and ROS but also has the potential to reshape the tumor microenvironment, overcoming T cell suppression in cold tumors.

A 5-Year Update on the Clinical Development of Cancer Cell-Based Vaccines for Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is considered one of the most aggressive forms of brain cancer with a 15-month median survival, despite advancements in surgery, radiotherapy, and chemotherapy. The immune-suppressed tumor microenvironment and the blood-brain barrier are major contributors to its poor prognosis and treatment resistance. In the last decade, significant progress has been made in developing cell-based vaccines to boost immune responses against GBM. This review provides an extensive update on recent clinical trials involving various cancer cell vaccines, including ICT-107, the α-type-1 DC vaccine, and others. Although these trials have demonstrated potential improvements in progression-free survival (PFS) and overall survival (OS), the diverse and immune-suppressed nature of GBM poses challenges for consistent therapeutic success. We discuss the details of these trials along with the potential mechanism of vaccine efficacy and immune activations. The findings of these trials highlight the significance of a personalized immunotherapy approach and suggest that patient stratification could significantly advance the clinical management of GBM.

Interactions and communications in the prostate tumour microenvironment: evolving towards effective cancer therapy

Prostate cancer is one of the most common malignancies in men. The tumour microenvironment (TME) has a critical role in the initiation, progression, and metastasis of prostate cancer. TME contains various cell types, including cancer-associated fibroblasts (CAFs), endothelial cells, immune cells such as macrophages, lymphocytes B and T, natural killer (NK) cells, and other proteins such as extracellular matrix (ECM) components. The interactions and communications between these cells within the TME are crucial for the growth and response of various solid tumours, such as prostate cancer to different anticancer modalities. In this review article, we exemplify the various mechanisms by which the TME influences prostate cancer progression. The roles of different cells, cytokines, chemokines, and growth factors in modulating the immune response and prostate tumour growth will be discussed. The impact of these cells and factors and other ECM components on tumour cell invasion and metastasis will also be discussed. We explain how these interactions in TME can affect the response of prostate cancer to therapy. We also highlight the importance of understanding these interactions to develop novel therapeutic approaches for prostate cancer.

The Recruitment and Immune Suppression Mechanisms of Myeloid-Derived Suppressor Cells and Their Impact on Bone Metastatic Cancer

BACKGROUND

MDSCs are immature neutrophils and monocytes with immunosuppressive potentials, involving mononuclear MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs).

RECENT FINDINGS

They are significant components of the tumor microenvironment (TME). Besides, recent studies also verified that MDSCs also facilitated the progression of bone metastasis by regulating the network of cytokines and the function of immune cells.

CONCLUSION

It is necessary to summarize the mechanisms of MDSC recruitment and immunosuppression, and their impact on bone metastasis.

From innovation to clinic: Emerging strategies harnessing electrically conductive polymers to enhance electrically stimulated peripheral nerve repair

Peripheral nerve repair (PNR) is a major healthcare challenge due to the limited regenerative capacity of the nervous system, often leading to severe functional impairments. While nerve autografts are the gold standard, their implications are constrained by issues such as donor site morbidity and limited availability, necessitating innovative alternatives like nerve guidance conduits (NGCs). However, the inherently slow nerve growth rate (∼1 mm/day) and prolonged neuroinflammation, delay recovery even with the use of passive (no-conductive) NGCs, resulting in muscle atrophy and loss of locomotor function. Electrical stimulation (ES) has the ability to enhance nerve regeneration rate by modulating the innate bioelectrical microenvironment of nerve tissue while simultaneously fostering a reparative environment through immunoregulation. In this context, electrically conductive polymer (ECP)-based biomaterials offer unique advantages for nerve repair combining their flexibility, akin to traditional plastics, and mixed ionic-electronic conductivity, similar to ionically conductive nerve tissue, as well as their biocompatibility and ease of fabrication. This review focuses on the progress, challenges, and emerging techniques for integrating ECP based NGCs with ES for functional nerve regeneration. It critically evaluates the various approaches using ECP based scaffolds, identifying gaps that have hindered clinical translation. Key challenges discussed include designing effective 3D NGCs with high electroactivity, optimizing ES modules, and better understanding of immunoregulation during nerve repair. The review also explores innovative strategies in material development and wireless, self-powered ES methods. Furthermore, it emphasizes the need for non-invasive ES delivery methods combined with hybrid ECP based neural scaffolds, highlighting future directions for advancing preclinical and clinical translation. Together, ECP based NGCs combined with ES represent a promising avenue for advancing PNR and improving patient outcomes.

Targeting the kynurenine pathway: another therapeutic opportunity in the metabolic crosstalk between cancer and immune cells

The pivotal role of metabolic reprogramming in cancer-related drug resistance, through the tryptophan-catabolized kynurenine pathway (KP), has been particularly underscored in recent research. This pathway, driven by indoleamine 2,3-dioxygenase 1 (IDO1), facilitates immune evasion and promotes tumor progression by fostering an immunosuppressive environment. In Phase III investigation of the combination of IDO1 inhibition with immune checkpoint inhibitors (ICIs), the combination therapy was not efficacious. In this review, we revisit current advances, explore future directions, and emphasize the importance of dual inhibition of the KP rate-limiting enzymes IDO1 and tryptophan 2,3-dioxygenase-2 (TDO2) in appropriate patient populations. We propose that dual inhibition may maximize the therapeutic potential of KP inhibition. Additionally, we delve into the complex cellular interactions in cancer and metabolic dependencies within the tumor microenvironment (TME). Insights from preclinical studies, recent clinical trials, and promising therapeutic combinations will be discussed to elucidate and promote a clear path forward for the direction of KP research into cancer-related outcomes.

Targeting Inflammation After Hemorrhagic Shock as a Molecular and Experimental Journey to Improve Outcomes: A Review

Hemorrhagic shock continues to be a major contributor to trauma-related fatalities globally, posing a significant and intricate pathophysiological challenge. The condition is marked by injury and blood loss, which activate molecular cascades that can quickly become harmful. The inflammatory response exhibits a biphasic pattern, beginning with a hyper-inflammatory phase that transitions into immunosuppression, posing significant obstacles to effective therapeutic interventions. This review article explores the intricate molecular mechanisms driving inflammation in hemorrhagic shock, emphasizing cellular signaling pathways, endothelial dysfunction, and immune activation. We discuss the role of molecular biomarkers in tracking disease progression and stratifying risk, with a focus on markers of endothelial dysfunction and inflammatory mediators as potential prognostic tools. Additionally, we assess therapeutic strategies, spanning traditional approaches like hemostatic resuscitation to advanced immunomodulatory treatments. Despite promising advancements in molecular monitoring and targeted therapies, challenges persist in bridging experimental findings with clinical applications. Future efforts must prioritize understanding the dynamic progression of inflammatory pathways and refining the timing of interventions to improve outcomes in hemorrhagic shock management.

Targeting the lung tumour stroma: harnessing nanoparticles for effective therapeutic interventions

Lung cancer remains an influential global health concern, necessitating the development of innovative therapeutic strategies. The tumour stroma, which is known as tumour microenvironment (TME) has a central impact on tumour expansion and treatment resistance. The stroma of lung tumours consists of numerous cells and molecules that shape an environment for tumour expansion. This environment not only protects tumoral cells against immune system attacks but also enables tumour stroma to attenuate the action of antitumor drugs. This stroma consists of stromal cells like cancer-associated fibroblasts (CAFs), suppressive immune cells, and cytotoxic immune cells. Additionally, the presence of stem cells, endothelial cells and pericytes can facilitate tumour volume expansion. Nanoparticles are hopeful tools for targeted drug delivery because of their extraordinary properties and their capacity to devastate biological obstacles. This review article provides a comprehensive overview of contemporary advancements in targeting the lung tumour stroma using nanoparticles. Various nanoparticle-based approaches, including passive and active targeting, and stimuli-responsive systems, highlighting their potential to improve drug delivery efficiency. Additionally, the role of nanotechnology in modulating the tumour stroma by targeting key components such as immune cells, extracellular matrix (ECM), hypoxia, and suppressive elements in the lung tumour stroma.

Reassessing the roles of oxidative DNA base lesion 8-oxoGua and repair enzyme OGG1 in tumorigenesis

ROS cause multiple forms of DNA damage, and among them, 8-oxoguanine (8-oxoGua), an oxidized product of guanine, is one of the most abundant. If left unrepaired, 8-oxoGua may pair with A instead of C, leading to a mutation of G: C to T: A during DNA replication. 8-Oxoguanine DNA glycosylase 1 (OGG1) is a tailored repair enzyme that recognizes 8-oxoGua in DNA duplex and initiates the base excision repair (BER) pathway to remove the lesion and ensure the fidelity of the genome. The accumulation of genomic 8-oxoGua and the dysfunction of OGG1 is readily linked to mutagenesis, and subsequently aging-related diseases and tumorigenesis; however, the direct experimental evidence has long been lacking. Recently, a series of studies have shown that guanine oxidation in the genome has a conservative bias, with the tendency to occur in the regulatory regions, thus, 8-oxoGua is not only a lesion to be repaired, but also an epigenetic modification. In this regard, OGG1 is a specific reader of this base modification. Substrate recognition and/or excision by OGG1 can cause DNA conformation changes, affect chromatin modifications, thereby modulating the transcription of genes involved in a variety of cellular processes, including inflammation, cell proliferation, differentiation, and apoptosis. Thus, in addition to the potential mutagenicity, 8-oxoGua may contribute to tumor development and progression through the altered gene expression stemming from its epigenetic effects.

Can interventions targeting MDSCs improve the outcome of vaccination in vulnerable populations?

Preventive vaccination is a crucial strategy for controlling and preventing infectious diseases, offering both effectiveness and cost-efficiency. However, despite the widespread success of vaccination programs, there are still certain population groups who struggle to mount adequate responses to immunization. These at-risk groups include but are not restricted to the elderly, overweight individuals, individuals with chronic infections and cancer patients. All of these groups are characterized by persistent chronic inflammation. Recent studies have demonstrated that one of the key players in immune regulation and the promotion of chronic inflammation are myeloid-derived suppressor cells (MDSCs). These cells possess a wide range of immunosuppressive mechanisms and are able to dampen immune responses in both antigen-specific and antigen-nonspecific manner, thus contributing to the establishment and maintenance of an inflammatory environment. Given their pivotal role in immune modulation, there is growing interest in understanding how MDSCs may influence the efficacy of vaccines, particularly in vulnerable populations. In this narrative review, we discuss whether MDSCs are able to regulate vaccine-induced immunity and whether their suppression can potentially enhance vaccine efficacy in vulnerable populations.

Patterns of immune evasion in triple-negative breast cancer and new potential therapeutic targets: a review

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the absence of progesterone and estrogen receptors and low (or absent) HER2 expression. TNBC accounts for 15-20% of all breast cancers. It is associated with younger age, a higher mutational burden, and an increased risk of recurrence and mortality. Standard treatment for TNBC primarily relies on cytotoxic agents, such as taxanes, anthracyclines, and platinum compounds for both early and advanced stages of the disease. Several targeted therapies, including bevacizumab and sunitinib, have failed to demonstrate significant clinical benefit in TNBC. The emergence of immune checkpoint inhibitors (ICI) has revolutionized cancer treatment. By stimulating the immune system, ICIs induce a durable anti-tumor response across various solid tumors. TNBC is a particularly promising target for treatment with ICIs due to the higher levels of tumor-infiltrating lymphocytes (TIL), increased PD-L1 expression, and higher mutational burden, which generates tumor-specific neoantigens that activate immune cells. ICIs administered as monotherapy in advanced TNBC yields only a modest response; however, response rates significantly improve when ICIs are combined with cytotoxic agents, particularly in tumors expressing PD-L1. Pembrolizumab is approved for use in both early and advanced TNBC in combination with standard chemotherapy. However, more research is needed to identify more potent biomarkers, and to better elucidate the synergism of ICIs with other targeted agents. In this review, we explore the challenges of immunotherapy in TNBC, examining the mechanisms of tumor progression mediated by immune cells within the tumor microenvironment, and the signaling pathways involved in both primary and acquired resistance. Finally, we provide a comprehensive overview of ongoing clinical trials underway to investigate novel immune-targeted therapies for TNBC.

Reactive oxygen species: Janus-faced molecules in the era of modern cancer therapy

Oxidative stress, that is, an unbalanced increase in reactive oxygen species (ROS), contributes to tumor-induced immune suppression and limits the efficacy of immunotherapy. Cancer cells have inherently increased ROS production, intracellularly through metabolic perturbations and extracellularly through activation of NADPH oxidases, which promotes cancer progression. Further increased ROS production or impaired antioxidant systems, induced, for example, by chemotherapy or radiotherapy, can preferentially kill cancer cells over healthy cells. Inflammatory cell-derived ROS mediate immunosuppressive effects of myeloid-derived suppressor cells and activated granulocytes, hampering antitumor effector cells such as T cells and natural killer (NK) cells. Cancer therapies modulating ROS levels in tumors may thus have entirely different consequences when targeting cancer cells versus immune cells. Here we discuss the possibility of developing more efficient cancer therapies based on reduction-oxidation modulation, as either monotherapies or in combination with immunotherapy. Short-term, systemic administration of antioxidants or drugs blocking ROS production can boost the immune system and act in synergy with immunotherapy. However, prolonged use of antioxidants can instead enhance tumor progression. Alternatives to systemic antioxidant administration are under development where gene-modified or activated T cells and NK cells are shielded ex vivo against the harmful effects of ROS before the infusion to patients with cancer.

Myeloid-derived suppressor cells in cancer: Current knowledge and future perspectives

MDSCs (myeloid-derived suppressor cells) are crucial for immune system evasion in cancer. They accumulate in peripheral blood and tumor microenvironment, suppressing immune cells like T-cells, natural killer cells and dendritic cells. They promote tumor angiogenesis and metastasis by secreting cytokines and growth factors and contribute to a tumor-promoting environment. The accumulation of MDSCs in cancer patients has been linked to poor prognosis and resistance to various cancer therapies. Targeting MDSCs and their immunosuppressive mechanisms may improve treatment outcomes and enhance immune surveillance by developing drugs that inhibit MDSC function, by preventing their accumulation and by disrupting the tumor-promoting environment. This review presents a detailed overview of the MDSC research in cancer with regulation of their development and function. The relevance of MDSC as a prognostic and predictive biomarker in different types of cancers, along with recent advancements on the therapeutic approaches to target MDSCs are discussed in detail.

High Humidity Alters Myeloid-Derived Suppressor Cells in Spleen Tissue: Insights into Rheumatoid Arthritis Progression

Background

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation and bone destruction, leading to severe complications. Previous research has suggested that high humidity conditions may exacerbate RA, however, the underlying mechanisms remain unclear. Furthermore, there is a lack of evidence linking humidity to the worsening of RA symptoms in animal models.

Methods

The Collagen-induced arthritis (CIA) mouse model was established using C57BL/6 mice. The arthritis status of the mice was evaluated under two distinct humidity conditions (50% and 80%). The aim of the present study was to investigate the impact of elevated humidity levels on the types of splenic cells present using mass spectrometry flow. Additionally, the study utilized MDSCs, which are significantly upregulated by high humidity, to assess the levels of oxidative stress and conducted mRNA sequencing of sorted MDSCs to investigate their impact on arthritis in CIA mice.

Results

Compared to normal humidity, high humidity exacerbated arthritis incidence in mice, resulting in increased arthritis scores, swelling, serum autoantibodies (anti-COII and anti-CCP), and upregulation of pro-inflammatory cytokines. Significant variations were observed in the spleen index under high humidity condition, accompanied by noticeable inflammatory alterations. Moreover, elevated humidity levels induced a substantial modulation in MDSCs population in the spleen of CIA mice, along with alterations in oxidative stress markers such as heightened serum ROS levels, and increased expression of COX, SOD, and Nrf2 mRNA. Following successful sorting of MDSCs, mRNA sequencing revealed a decrease in the expression of Rap1 signaling pathway under high humidity environment, which may contribute to the increase of MDSCs cells and aggravate the progression of RA disease.

Conclusion

A comprehensive analysis of the available data reveals a detrimental impact of high humidity on MDSCs numbers within spleen tissue, with potential implications for the development of RA.

Targeting ROS-sensing Nrf2 potentiates anti-tumor immunity of intratumoral CD8+ T and CAR-T cells

Cytotoxic T lymphocytes (CTLs) play a crucial role in cancer rejection. However, CTLs encounter dysfunction and exhaustion in the immunosuppressive tumor microenvironment (TME). Although the reactive oxygen species (ROS)-rich TME attenuates CTL function, the underlying molecular mechanism remains poorly understood. The nuclear factor erythroid 2-related 2 (Nrf2) is the ROS-responsible factor implicated in increasing susceptibility to cancer progression. Therefore, we examined how Nrf2 is involved in anti-tumor responses of CD8+ T and chimeric antigen receptor (CAR) T cells in the ROS-rich TME. Here, we demonstrated that tumor growth in Nrf2-/- mice was significantly controlled and was reversed by T cell depletion and further confirmed that Nrf2 deficiency in T cells promotes anti-tumor responses using an adoptive transfer model of antigen-specific CD8+ T cells. Nrf2-deficient CTLs are resistant to ROS, and their effector functions are sustained in the TME. Furthermore, Nrf2 knockdown in human CAR-T cells enhanced the survival and function of intratumoral CAR-T cells in a solid tumor xenograft model and effectively controlled tumor growth. ROS-sensing Nrf2 inhibits the anti-tumor T cell responses, indicating that Nrf2 may be a potential target for T cell immunotherapy strategies against solid tumors.

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.

MAPK signaling pathway induced LOX-1+ polymorphonuclear myeloid-derived suppressor cells in biliary atresia

Biliary atresia (BA) is a severe pediatric liver disease characterized by progressive bile duct destruction and fibrosis, leading to significant liver damage and frequently necessitating liver transplantation. This study elucidates the role of LOX-1+ polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in BA pathogenesis and assesses their potential as non-invasive early diagnostic biomarkers. Using flow cytometry, immunofluorescence, and molecular profiling, we analyzed the expression and activity of these cells in peripheral blood and liver tissues from BA patients and controls. Our findings reveal a significant increase in the frequencies and function of LOX-1+PMN-MDSCs in BA patients, along with MAPK signaling pathway upregulation, indicating their involvement in disease mechanisms. Additionally, the frequencies of LOX-1+PMN-MDSC in peripheral blood significantly positively correlate with liver function parameters in BA patients, demonstrating diagnostic performance comparable to traditional serum markers. These findings suggest that LOX-1+PMN-MDSCs contribute to the immunosuppressive environment in BA and could serve as potential diagnostic targets.

Targeting Lipid Metabolism in Cancer Stem Cells for Anticancer Treatment

Cancer stem cells (CSCs), or tumor-initiating cells (TICs), are small subpopulations (0.0001-0.1%) of cancer cells that are crucial for cancer relapse and therapy resistance. The elimination of each CSC is essential for achieving long-term remission. Metabolic reprogramming, particularly lipids, has a significant impact on drug efficacy by influencing drug diffusion, altering membrane permeability, modifying mitochondrial function, and adjusting the lipid composition within CSCs. These changes contribute to the development of chemoresistance in various cancers. The intricate relationship between lipid metabolism and drug resistance in CSCs is an emerging area of research, as different lipid species play essential roles in multiple stages of autophagy. However, the link between autophagy and lipid metabolism in the context of CSC regulation remains unclear. Understanding the interplay between autophagy and lipid reprogramming in CSCs could lead to the development of new approaches for enhancing therapies and reducing tumorigenicity in these cells. In this review, we explore the latest findings on lipid metabolism in CSCs, including the role of key regulatory enzymes, inhibitors, and the contribution of autophagy in maintaining lipid homeostasis. These recent findings may provide critical insights for identifying novel pharmacological targets for effective anticancer treatment.

Microcapsules based on biological macromolecules for intestinal health: A review

Intestinal dysfunction is becoming increasingly associated with neurological and endocrine issues, raising concerns about its impact on world health. With the introduction of several breakthrough technologies for detecting and treating intestinal illnesses, significant progress has been made in the previous few years. On the other hand, traditional intrusive diagnostic techniques are expensive and time-consuming. Furthermore, the efficacy of conventional drugs (not capsules) is reduced since they are more likely to degrade before reaching their target. In this context, microcapsules based on different types of biological macromolecules have been used to encapsulate active drugs and sensors to track intestinal ailments and address these issues. Several biomacromolecules/biomaterials (natural protein, alginate, chitosan, cellulose and RNA etc.) are widely used for make microcapsules for intestinal diseases, and can significantly improve the therapeutic effect and reduce adverse reactions. This article systematically summarizes microencapsulated based on biomacromolecules material for intestinal health control and efficacy enhancement. It also discusses the application and mechanism research of microencapsulated biomacromolecules drugs in reducing intestinal inflammation, in addition to covering the preparation techniques of microencapsulated drug delivery systems used for intestinal health. Microcapsule delivery systems' limits and potential applications for intestinal disease diagnosis, treatment, and surveillance were highlighted.

17β-estradiol promotes myeloid-derived suppressor cells functions and alleviates inflammatory bowel disease by activation of Stat3 and NF-κB signalings

Inflammatory bowel disease (IBD) describes a group of clinically common autoimmune diseases characterized by chronic intestinal inflammation, with gender differences in prevalence. Estrogen has been previously shown to exert anti-inflammatory action in IBD development, however, the mechanisms remain obscure. Recent research has revealed that myeloid-derived suppressor cells (MDSCs) play a protective role in IBD pathogenesis. To investigate the molecular mechanisms of estrogen steroid 17β-estradiol (E2) in IBD progression, we established IBD mouse models (DNB-induced) with or without prior ovariectomy (OVX) and E2 implantation. We found that OVX led to worse IBD symptoms and reduced MDSCs frequency, whereas E2 significantly alleviated these effects in vivo. Moreover, in vitro experiments showed that E2 promoted the proliferation and immunosuppressive function of MDSCs through phosphorylation of Stat3 and p65. Mechanistically, E2-mediated Stat3/p65 phosphorylation depends on the interaction between HOTAIR, a long non-coding RNA that are well-known in MDSCs proliferation, and Stat3/p65 respectively. In conclusion, our study revealed that E2 promotes the expansion and immunosuppressive function of MDSCs, and thus diminished the occurrence and development of IBD.

Immunosuppressive tumor microenvironment in the progression, metastasis, and therapy of hepatocellular carcinoma: from bench to bedside

Hepatocellular carcinoma (HCC) is a highly heterogeneous malignancy with high incidence, recurrence, and metastasis rates. The emergence of immunotherapy has improved the treatment of advanced HCC, but problems such as drug resistance and immune-related adverse events still exist in clinical practice. The immunosuppressive tumor microenvironment (TME) of HCC restricts the efficacy of immunotherapy and is essential for HCC progression and metastasis. Therefore, it is necessary to elucidate the mechanisms behind immunosuppressive TME to develop and apply immunotherapy. This review systematically summarizes the pathogenesis of HCC, the formation of the highly heterogeneous TME, and the mechanisms by which the immunosuppressive TME accelerates HCC progression and metastasis. We also review the status of HCC immunotherapy and further discuss the existing challenges and potential therapeutic strategies targeting immunosuppressive TME. We hope to inspire optimizing and innovating immunotherapeutic strategies by comprehensively understanding the structure and function of immunosuppressive TME in HCC.

Myeloid-derived suppressor cells-induced exhaustion of CD8 + T-cell participates in rejection after liver transplantation

Liver transplantation (LT) rejection remains the most pervasive problem associated with this procedure, while the mechanism involved is still complicated and undefined. One promising solution may involve the use of myeloid-derived suppressor cells (MDSC). However, the immunological mechanisms underlying the effects of MDSC after LT remain unclear. This study is meant to clarify the role MDSCs play after liver transplantation. In this study, we collected liver tissue and peripheral blood mononuclear cells (PBMC) from LT patients showing varying degrees of rejection, as well as liver and spleen tissue samples from mice LT models. These samples were then analyzed using flow cytometry, immunohistochemistry and multiple immunofluorescence. M-MDSCs and CD8 + T-cells extracted from C57/BL6 mice were enriched and cocultured for in vitro experiments. Results, as obtained in both LT patients and LT mice model, revealed that the proportion and frequency of M-MDSC and PD-1 + T-cells increased significantly under conditions associated with a high degree of LT rejection. Within the LT rejection group, our immunofluorescence results showed that a close spatial contiguity was present between PD-1 + T-cells and M-MDSCs in these liver tissue samples and the proportion of CD84/PD-L1 double-positive M-MDSC was greater than that of G-MDSC. There was a positive correlation between the activity of CD84 and immunosuppressive function of M-MDSCs including PD-L1 expression and reactive oxygen species (ROS) production, as demonstrated in our in vitro model. M-MDSCs treated with CD84 protein were able to induce co-cultured CD8 + T-cells to express high levels of exhaustion markers. We found that CD84 regulated M-MDSC function via expression of PD-L1 through activation of the Akt/Stat3 pathway. These results suggest that the capacity for CD84 to regulate M-MDSC induction of CD8 + T-cell exhaustion may play a key role in LT rejection. Such findings provide important, new insights into the mechanisms of tolerance induction in LT.

Plasmodium yoelii Infection Enhances the Expansion of Myeloid-Derived Suppressor Cells via JAK/STAT3 Pathway

Myeloid-derived suppressor cells (MDSCs), the negative immune regulators, have been demonstrated to be involved in immune responses to a variety of pathological conditions, such as tumors, chronic inflammation, and infectious diseases. However, the roles and mechanisms underlying the expansion of MDSCs in malaria remain unclear. In this study, the phenotypic and functional characteristics of splenic MDSCs during Plasmodium yoelii NSM infection are described. Furthermore, we provide compelling evidence that the sera from P. yoelii-infected C57BL/6 mice containing excess IL-6 and granulocyte-macrophage colony-stimulating factor promote the accumulation of MDSCs by inducing Bcl2 expression. Serum-induced MDSCs exert more potent suppressive effects on T cell responses than control MDSCs within both in vivo P. yoelii infection and in vitro serum-treated bone marrow cells experiments. Serum treatment increases the MDSC inhibitory effect, which is dependent on Arg1 expression. Moreover, mechanistic studies reveal that the serum effects are mediated by JAK/STAT3 signaling. By inhibiting STAT3 phosphorylation with the JAK inhibitor JSI-124, effects of serum on MDSCs are almost eliminated. In vivo depletion of MDSCs with anti-Gr-1 or 5-fluorouracil significantly reduces the parasitemia and promotes Th1 immune response in P. yoelii-infected C57BL/6 mice by upregulating IFN-γ expression. In summary, this study indicates that P. yoelii infection facilitates the accumulation and function of MDSCs by upregulating the expression of Bcl2 and Arg1 via JAK/STAT3 signaling pathway in vivo and in vitro. Manipulating the JAK/STAT3 signaling pathway or depleting MDSCs could be promising therapeutic interventions to treat malaria.

Effect of luteolin on oxidative stress and inflammation in the human osteoblast cell line hFOB1.19 in an inflammatory microenvironment

BACKGROUND

Periapical lesions are characterized by periapical inflammation and damage to periapical tissues and eventually lead to bone resorption and even tooth loss. H2O2 is widely used in root canal therapy for patients with periapical inflammation. Luteolin possesses high anti-inflammatory, antioxidant, and anticancer potential. However, the underlying mechanism of the efficacy of H2O2 and luteolin on oxidative stress and inflammatory tissue has not been previously addressed. We aimed to investigate the anti-inflammatory and antioxidative effects of luteolin on H2O2-induced cellular oxidative inflammation.

METHODS

After human osteoblasts (hFOB1.19) were treated with lipopolysaccharide (LPS), luteolin, or H2O2, cell proliferation was analysed by using a cell counting kit-8 (CCK-8), cell apoptosis was measured by using flow cytometry, the production of reactive oxygen species (ROS) was evaluated by using an oxidation-sensitive probe DCFH-DA ROS assay kit, and the expression of genes and proteins was detected by using reverse transcription quantitative polymerase chain reaction (RT‒qPCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

We demonstrated that inflammation is closely related to oxidative stress and that the oxidative stress level in the inflammatory environment is increased. Luteolin inhibited the H2O2-induced increase in the expression of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor α (TNF-α) and significantly repressed the H2O2-induced increase in ROS, as well as markedly strengthened superoxide dismutase (SOD) activity in hFOB1.19 cells. Moreover, we detected that luteolin may inhibit H2O2-induced hFOB1.19 cell injury by suppressing the NF-κB pathway.

CONCLUSION

We elucidated that luteolin protected human osteoblasts (hFOB1.19) from H2O2-induced cell injury and inhibited the production of proinflammatory cytokines by suppressing the NF-κB signalling pathway. Our findings provide a potential drug for treating H2O2-induced periodontitis and cell injury.

MDSCs use a complex molecular network to suppress T-cell immunity in a pulmonary model of fungal infection

Background

Paracoccidioidomycosis (PCM) is a systemic endemic fungal disease prevalent in Latin America. Previous studies revealed that host immunity against PCM is tightly regulated by several suppressive mechanisms mediated by tolerogenic plasmacytoid dendritic cells, the enzyme 2,3 indoleamine dioxygenase (IDO-1), regulatory T-cells (Tregs), and through the recruitment and activation of myeloid-derived suppressor cells (MDSCs). We have recently shown that Dectin-1, TLR2, and TLR4 signaling influence the IDO-1-mediated suppression caused by MDSCs. However, the contribution of these receptors in the production of important immunosuppressive molecules used by MDSCs has not yet been explored in pulmonary PCM.

Methods

We evaluated the expression of PD-L1, IL-10, as well as nitrotyrosine by MDSCs after anti-Dectin-1, anti-TLR2, and anti-TLR4 antibody treatment followed by P. brasiliensis yeasts challenge in vitro. We also investigated the influence of PD-L1, IL-10, and nitrotyrosine in the suppressive activity of lung-infiltrating MDSCs of C57BL/6-WT, Dectin-1KO, TLR2KO, and TLR4KO mice after in vivo fungal infection. The suppressive activity of MDSCs was evaluated in cocultures of isolated MDSCs with activated T-cells.

Results

A reduced expression of IL-10 and nitrotyrosine was observed after in vitro anti-Dectin-1 treatment of MDSCs challenged with fungal cells. This finding was further confirmed in vitro and in vivo by using Dectin-1KO mice. Furthermore, MDSCs derived from Dectin-1KO mice showed a significantly reduced immunosuppressive activity on the proliferation of CD4+ and CD8+ T lymphocytes. Blocking of TLR2 and TLR4 by mAbs and using MDSCs from TLR2KO and TLR4KO mice also reduced the production of suppressive molecules induced by fungal challenge. In vitro, MDSCs from TLR4KO mice presented a reduced suppressive capacity over the proliferation of CD4+ T-cells.

Conclusion

We showed that the pathogen recognition receptors (PRRs) Dectin-1, TLR2, and TLR4 contribute to the suppressive activity of MDSCs by inducing the expression of several immunosuppressive molecules such as PD-L1, IL-10, and nitrotyrosine. This is the first demonstration of a complex network of PRRs signaling in the induction of several suppressive molecules by MDSCs and its contribution to the immunosuppressive mechanisms that control immunity and severity of pulmonary PCM.

Advances in electroactive biomaterials: Through the lens of electrical stimulation promoting bone regeneration strategy

The regenerative capacity of bone is indispensable for growth, given that accidental injury is almost inevitable. Bone regenerative capacity is relevant for the aging population globally and for the repair of large bone defects after osteotomy (e.g., following removal of malignant bone tumours). Among the many therapeutic modalities proposed to bone regeneration, electrical stimulation has attracted significant attention owing to its economic convenience and exceptional curative effects, and various electroactive biomaterials have emerged. This review summarizes the current knowledge and progress regarding electrical stimulation strategies for improving bone repair. Such strategies range from traditional methods of delivering electrical stimulation via electroconductive materials using external power sources to self-powered biomaterials, such as piezoelectric materials and nanogenerators. Electrical stimulation and osteogenesis are related via bone piezoelectricity. This review examines cell behaviour and the potential mechanisms of electrostimulation via electroactive biomaterials in bone healing, aiming to provide new insights regarding the mechanisms of bone regeneration using electroactive biomaterials.

The translational potential of this article

This review examines the roles of electroactive biomaterials in rehabilitating the electrical microenvironment to facilitate bone regeneration, addressing current progress in electrical biomaterials and the mechanisms whereby electrical cues mediate bone regeneration. Interactions between osteogenesis-related cells and electroactive biomaterials are summarized, leading to proposals regarding the use of electrical stimulation-based therapies to accelerate bone healing.

Impact and potential value of immunosenescence on solid gastrointestinal tumors

Solid gastrointestinal tumors often respond poorly to immunotherapy for the complex tumor microenvironment (TME), which is exacerbated by immune system alterations. Immunosenescence is the process of increased diversification of immune genes due to aging and other factors, leading to a decrease in the recognition function of the immune system. This process involves immune organs, immune cells, and the senescence-associated secretory phenotype (SASP). The most fundamental change is DNA damage, resulting in TME remodeling. The main manifestations are worsening inflammation, increased immunosuppressive SASP production, decreased immune cell antitumor activity, and the accumulation of tumor-associated fibroblasts and myeloid-derived suppressor cells, making antitumor therapy less effective. Senotherapy strategies to remove senescent cells and block key senescence processes can have synergistic effects with other treatments. This review focuses on immunoenescence and its impact on the solid TME. We characterize the immunosenescent TME and discuss future directions for antitumor therapies targeting senescence.

Mechanisms of myeloid-derived suppressor cell-mediated immunosuppression in colorectal cancer and related therapies

Severe immunosuppression is a hallmark of colorectal cancer (CRC). Myeloid-derived suppressor cells (MDSCs), one of the most abundant components of the tumor stroma, play an important role in the invasion, metastasis, and immune escape of CRC. MDSCs create an immunosuppressive microenvironment by inhibiting the proliferation and activation of immunoreactive cells, including T and natural killer cells, as well as by inducing the proliferation of immunosuppressive cells, such as regulatory T cells and tumor-associated macrophages, which, in turn, promote the growth of cancer cells. Thus, MDSCs are key contributors to the emergence of an immunosuppressive microenvironment in CRC and play an important role in the breakdown of antitumor immunity. In this narrative review, we explore the mechanisms through which MDSCs contribute to the immunosuppressive microenvironment, the current therapeutic approaches and technologies targeting MDSCs, and the therapeutic potential of modulating MDSCs in CRC treatment. This study provides ideas and methods to enhance survival rates in patients with CRC.

β-Glucan Subverts the Function of Myeloid Cells in Neonates

β-Glucan is the main component of the cell wall of pathogen-associated molecular patterns (PAMPs) including various yeast, fungi, or certain bacteria. Previous reports demonstrated that β-glucan was widely investigated as a potent immunomodulators to stimulate innate and adaptive immune responses, which indicated that it could be recommended as an effective adjuvant in immunotherapy. However, the detailed effects of β-glucan on neonatal immunity are still largely unknown. Here, we found that β-glucan did not affect the frequencies and numbers of myeloid cells in the spleen and bone marrow from neonates. Functional assay revealed that β-glucan from neonates compromised the immunosuppressive function of immature myeloid cells, which were myeloid-derived suppressor cells (MDSCs). Flow cytometry or gene expression analysis revealed that β-glucan-derived polymorphonuclear (PMN)-MDSCs produced lower level of reactive oxygen species (ROS) and arginase-1 (Arg1) in neonatal mice. Furthermore, β-glucan administration significantly decreased the frequency and ROS level of PMN-MDSCs in vitro. These observations suggest that β-glucan facilitates the maturation of myeloid cells in early life, which may contribute to its beneficial effects against immune disorders later in life.

Radiation Therapy and Myeloid-Derived Suppressor Cells: Breaking Down Their Cancerous Partnership

Radiation therapy (RT) has been a primary treatment modality in cancer for decades. Increasing evidence suggests that RT can induce an immunosuppressive shift via upregulation of cells such as tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs). MDSCs inhibit antitumor immunity through potent immunosuppressive mechanisms and have the potential to be crucial tools for cancer prognosis and treatment. MDSCs interact with many different pathways, desensitizing tumor tissue and interacting with tumor cells to promote therapeutic resistance. Vascular damage induced by RT triggers an inflammatory signaling cascade and potentiates hypoxia in the tumor microenvironment (TME). RT can also drastically modify cytokine and chemokine signaling in the TME to promote the accumulation of MDSCs. RT activation of the cGAS-STING cytosolic DNA sensing pathway recruits MDSCs through a CCR2-mediated mechanism, inhibiting the production of type 1 interferons and hampering antitumor activity and immune surveillance in the TME. The upregulation of hypoxia-inducible factor-1 and vascular endothelial growth factor mobilizes MDSCs to the TME. After recruitment, MDSCs promote immunosuppression by releasing reactive oxygen species and upregulating nitric oxide production through inducible nitric oxide synthase expression to inhibit cytotoxic activity. Overexpression of arginase-1 on subsets of MDSCs degrades L-arginine and downregulates CD3ζ, inhibiting T-cell receptor reactivity. This review explains how radiation promotes tumor resistance through activation of immunosuppressive MDSCs in the TME and discusses current research targeting MDSCs, which could serve as a promising clinical treatment strategy in the future.

A Roadmap of CAR-T-Cell Therapy in Glioblastoma: Challenges and Future Perspectives

Glioblastoma (GBM) is the most common primary malignant brain tumor, with a median overall survival of less than 2 years and a nearly 100% mortality rate under standard therapy that consists of surgery followed by combined radiochemotherapy. Therefore, new therapeutic strategies are urgently needed. The success of chimeric antigen receptor (CAR) T cells in hematological cancers has prompted preclinical and clinical investigations into CAR-T-cell treatment for GBM. However, recent trials have not demonstrated any major success. Here, we delineate existing challenges impeding the effectiveness of CAR-T-cell therapy for GBM, encompassing the cold (immunosuppressive) microenvironment, tumor heterogeneity, T-cell exhaustion, local and systemic immunosuppression, and the immune privilege inherent to the central nervous system (CNS) parenchyma. Additionally, we deliberate on the progress made in developing next-generation CAR-T cells and novel innovative approaches, such as low-intensity pulsed focused ultrasound, aimed at surmounting current roadblocks in GBM CAR-T-cell therapy.

Granzymes in health and diseases: the good, the bad and the ugly

Granzymes are a family of serine proteases, composed of five human members: GA, B, H, M and K. They were first discovered in the 1980s within cytotoxic granules released during NK cell- and T cell-mediated killing. Through their various proteolytic activities, granzymes can trigger different pathways within cells, all of which ultimately lead to the same result, cell death. Over the years, the initial consideration of granzymes as mere cytotoxic mediators has changed due to surprising findings demonstrating their expression in cells other than immune effectors as well as new intracellular and extracellular activities. Additional roles have been identified in the extracellular milieu, following granzyme escape from the immunological synapse or their release by specific cell types. Outside the cell, granzyme activities mediate extracellular matrix alteration via the degradation of matrix proteins or surface receptors. In certain contexts, these processes are essential for tissue homeostasis; in others, excessive matrix degradation and extensive cell death contribute to the onset of chronic diseases, inflammation, and autoimmunity. Here, we provide an overview of both the physiological and pathological roles of granzymes, highlighting their utility while also recognizing how their unregulated presence can trigger the development and/or worsening of diseases.

Targeting the tumor microenvironment, a new therapeutic approach for prostate cancer

BACKGROUND

A growing number of studies have shown that in addition to adaptive immune cells such as CD8 + T cells and CD4 + T cells, various other cellular components within prostate cancer (PCa) tumor microenvironment (TME), mainly tumor-associated macrophages (TAMs), cancer-associated fibroblasts (CAFs) and myeloid-derived suppressor cells (MDSCs), have been increasingly recognized as important modulators of tumor progression and promising therapeutic targets.

OBJECTIVE

In this review, we aim to delineate the mechanisms by which TAMs, CAFs and MDSCs interact with PCa cells in the TME, summarize the therapeutic advancements targeting these cells and discuss potential new therapeutic avenues.

METHODS

We searched PubMed for relevant studies published through December 10 2023 on TAMs, CAFs and MDSCs in PCa.

RESULTS

TAMs, CAFs and MDSCs play a critical role in the tumorigenesis, progression, and metastasis of PCa. Moreover, they substantially mediate therapeutic resistance against conventional treatments including anti-androgen therapy, chemotherapy, and immunotherapy. Therapeutic interventions targeting these cellular components have demonstrated promising effects in preclinical models and several clinical trials for PCa, when administrated alone, or combined with other anti-cancer therapies. However, the lack of reliable biomarkers for patient selection and incomplete understanding of the mechanisms underlying the interactions between these cellular components and PCa cells hinder their clinical translation and utility.

CONCLUSION

New therapeutic strategies targeting TAMs, CAFs, and MDSCs in PCa hold promising prospects. Future research endeavors should focus on a more comprehensive exploration of the specific mechanisms by which these cells contribute to PCa, aiming to identify additional drug targets and conduct more clinical trials to validate the safety and efficacy of these treatment strategies.

CD14-CD10-CD45+HLA-DR-SSC+ neutrophils may be granulocytic myeloid-derived suppressor cell-like cells and relate to disease progression in non-Hodgkin's lymphoma patients

We explored the frequency of CD14-CD10-CD45+HLA-DR-SSC++ neutrophils (CD10- neutrophils) in patients with non-Hodgkin's lymphoma (NHL), and their immunologic characteristics and clinical significance. Patients with NHL who were newly diagnosed (NDP; n = 33), in remission (RMP; n = 28) and relapsed (RLP; n = 29) were included, and 47 volunteers were recruited as healthy controls (HCs). The frequency of CD10- neutrophils in the peripheral blood from HC and patients with NHL was detected. CD10- and CD10+ neutrophils were sorted, and their cytology was analyzed. CD3+ T cells were also isolated and cultured with the autologous CD10- or CD10+ neutrophils, after which the proliferation and death rates of T cells were determined. The levels of arginase-1 (Arg-1) and reactive oxygen species (ROS) in CD10+ or CD10- neutrophils were examined. Few CD10- neutrophils were detected in HCs but were significantly elevated in patients with NHL, especially in NDP and RLP. In addition, CD10- neutrophils in NDP with advanced stage and high risk were markedly higher than those in NDP with limited stage and low risk. In RMP and RLP, the relapse-free survival and overall survival in patients with high CD10- neutrophils were shorter than those with low CD10- neutrophils. CD10- neutrophils from patients with NHL, which mainly consist of immature neutrophils, inhibit T-cell proliferation and facilitate T-cell death. Furthermore, a significant increase was observed in Arg-1 expression, along with an increase to a certain extent in ROS. CD10- neutrophils in patients with NHL have characteristics of myeloid-derived suppressor cells and may be related to disease progression and poor prognosis.

Nanomedicines for reversing immunosuppressive microenvironment of hepatocellular carcinoma

Although immunotherapeutic strategies such as immune checkpoint inhibitors (ICIs) have gained promising advances, their limited efficacy and significant toxicity remain great challenges for hepatocellular carcinoma (HCC) immunotherapy. The tumor immunosuppressive microenvironment (TIME) with insufficient T-cell infiltration and low immunogenicity accounts for most HCC patients' poor response to ICIs. Worse still, the current immunotherapeutics without precise delivery may elicit enormous autoimmune side effects and systemic toxicity in the clinic. With a better understanding of the TIME in HCC, nanomedicines have emerged as an efficient strategy to achieve remodeling of the TIME and superadditive antitumor effects via targeted delivery of immunotherapeutics or multimodal synergistic therapy. Based on the typical characteristics of the TIME in HCC, this review summarizes the recent advancements in nanomedicine-based strategies for TIME-reversing HCC treatment. Additionally, perspectives on the awaiting challenges and opportunities of nanomedicines in modulating the TIME of HCC are presented. Acquisition of knowledge of nanomedicine-mediated TIME reversal will provide researchers with a better opportunity for clinical translation of HCC immunotherapy.

Myeloid-derived suppressor cell mitochondrial fitness governs chemotherapeutic efficacy in hematologic malignancies

Myeloid derived suppressor cells (MDSCs) are key regulators of immune responses and correlate with poor outcomes in hematologic malignancies. Here, we identify that MDSC mitochondrial fitness controls the efficacy of doxorubicin chemotherapy in a preclinical lymphoma model. Mechanistically, we show that triggering STAT3 signaling via β2-adrenergic receptor (β2-AR) activation leads to improved MDSC function through metabolic reprograming, marked by sustained mitochondrial respiration and higher ATP generation which reduces AMPK signaling, altering energy metabolism. Furthermore, induced STAT3 signaling in MDSCs enhances glutamine consumption via the TCA cycle. Metabolized glutamine generates itaconate which downregulates mitochondrial reactive oxygen species via regulation of Nrf2 and the oxidative stress response, enhancing MDSC survival. Using β2-AR blockade, we target the STAT3 pathway and ATP and itaconate metabolism, disrupting ATP generation by the electron transport chain and decreasing itaconate generation causing diminished MDSC mitochondrial fitness. This disruption increases the response to doxorubicin and could be tested clinically.

Bladder-cancer-derived exosomal circRNA_0013936 promotes suppressive immunity by up-regulating fatty acid transporter protein 2 and down-regulating receptor-interacting protein kinase 3 in PMN-MDSCs

BACKGROUND

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is one of the causes of tumor immune tolerance and failure of cancer immunotherapy. Here, we found that bladder cancer (BCa)-derived exosomal circRNA_0013936 could enhance the immunosuppressive activity of PMN-MDSCs by regulating the expression of fatty acid transporter protein 2 (FATP2) and receptor-interacting protein kinase 3 (RIPK3). However, the underlying mechanism remains largely unknown.

METHODS

BCa-derived exosomes was isolated and used for a series of experiments. RNA sequencing was used to identify the differentially expressed circRNAs. Western blotting, immunohistochemistry, immunofluorescence, qRT-PCR, ELISA and Flow cytometry were performed to reveal the potential mechanism of circRNA_0013936 promoting the immunosuppressive activity of PMN-MDSC.

RESULTS

CircRNA_0013936 enriched in BCa-derived exosomes could promote the expression of FATP2 and inhibit the expression of RIPK3 in PMN-MDSCs. Mechanistically, circRNA_0013936 promoted the expression of FATP2 and inhibited the expression of RIPK3 expression via sponging miR-320a and miR-301b, which directly targeted JAK2 and CREB1 respectively. Ultimately, circRNA_0013936 significantly inhibited the functions of CD8+ T cells by up-regulating FATP2 through the circRNA_0013936/miR-320a/JAK2 pathway, and down-regulating RIPK3 through the circRNA_0013936/miR-301b/CREB1 pathway in PMN-MDSCs.

CONCLUSIONS

BCa-derived exosomal circRNA_0013936 promotes suppressive immunity by up-regulating FATP2 through the circRNA_0013936/miR-320a/JAK2 pathway and down-regulating RIPK3 through the circRNA_0013936/miR-301b-3p/CREB1 pathway in PMN-MDSCs. These findings help to find new targets for clinical treatment of human bladder cancer.

Metabolic collaboration between cells in the tumor microenvironment has a negligible effect on tumor growth

The tumor microenvironment is composed of a complex mixture of different cell types interacting under conditions of nutrient deprivation, but the metabolism therein is not fully understood due to difficulties in measuring metabolic fluxes and exchange of metabolites between different cell types in vivo. Genome-scale metabolic modeling enables estimation of such exchange fluxes as well as an opportunity to gain insight into the metabolic behavior of individual cell types. Here, we estimated the availability of nutrients and oxygen within the tumor microenvironment using concentration measurements from blood together with a metabolite diffusion model. In addition, we developed an approach to efficiently apply enzyme usage constraints in a comprehensive metabolic model of human cells. The combined modeling reproduced severe hypoxic conditions and the Warburg effect, and we found that limitations in enzymatic capacity contribute to cancer cells' preferential use of glutamine as a substrate to the citric acid cycle. Furthermore, we investigated the common hypothesis that some stromal cells are exploited by cancer cells to produce metabolites useful for the cancer cells. We identified over 200 potential metabolites that could support collaboration between cancer cells and cancer-associated fibroblasts, but when limiting to metabolites previously identified to participate in such collaboration, no growth advantage was observed. Our work highlights the importance of enzymatic capacity limitations for cell behaviors and exemplifies the utility of enzyme-constrained models for accurate prediction of metabolism in cells and tumor microenvironments.

Advances in tumor immune microenvironment of head and neck squamous cell carcinoma: A review of literature

Squamous cell carcinoma is seen as principal malignancy of head and neck. Tumor immune microenvironment plays a vital role in the occurrence, development and treatment of head and neck squamous cell carcinoma (HNSCC). The effect of immunotherapy, in particular, is closely related to tumor immune microenvironment. This review searched for high-quality literature included within PubMed, Web of Science, and Scopus using the keywords "head and neck cancers," "tumor microenvironment" and "immunotherapy," with the view to summarizing the characteristics of HNSCC immune microenvironment and how various subsets of immune cells promote tumorigenesis. At the same time, based on the favorable prospects of immunotherapy having been shown currently, the study is committed to pinpointing the latest progress of HNSCC immunotherapy, which is of great significance in not only further guiding the diagnosis and treatment of HNSCC, but also conducting its prognostic judgement.

Granulocytic myeloid-derived suppressor cell activity during biofilm infection is regulated by a glycolysis/HIF1a axis

Staphylococcus aureus is a leading cause of biofilm-associated prosthetic joint infection (PJI). A primary contributor to infection chronicity is an expansion of granulocytic myeloid-derived suppressor cells (G-MDSCs), which are critical for orchestrating the antiinflammatory biofilm milieu. Single-cell sequencing and bioinformatic metabolic algorithms were used to explore the link between G-MDSC metabolism and S. aureus PJI outcome. Glycolysis and the hypoxia response through HIF1a were significantly enriched in G-MDSCs. Interfering with both pathways in vivo, using a 2-deoxyglucose nanopreparation and granulocyte-targeted Hif1a conditional KO mice, respectively, attenuated G-MDSC-mediated immunosuppression and reduced bacterial burden in a mouse model of S. aureus PJI. In addition, single-cell RNA-Seq (scRNA-Seq) analysis of granulocytes from PJI patients also showed an enrichment in glycolysis and hypoxia-response genes. These findings support the importance of a glycolysis/HIF1a axis in promoting G-MDSC antiinflammatory activity and biofilm persistence during PJI.

Novel therapeutic strategies targeting myeloid-derived suppressor cell immunosuppressive mechanisms for cancer treatment

Cancer is the leading cause of death globally superseded only by cardiovascular diseases, and novel strategies to overcome therapeutic resistance against existing cancer treatments are urgently required. Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells with potent immunosuppressive capacity against well-established anti-tumour effectors such as natural killer cells (NK cells) and T cells thereby promoting cancer initiation and progression. Critically, MDSCs are readily identified in almost all tumour types and human cancer patients, and numerous studies in the past decade have recognised their role in contributing to therapeutic resistance against all four pillars of modern cancer treatment, namely surgery, chemotherapy, radiotherapy and immunotherapy. MDSCs suppress anti-tumour immunity through a plethora of mechanisms including the well-characterised arginase 1 (Arg1), inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS)-mediated pathways, along with several other more recently discovered. MDSCs are largely absent in healthy homeostatic states and predominantly exist in pathological conditions, making them attractive therapeutic targets. However, the lack of specific markers identified for MDSCs to date greatly hindered therapeutic development, and currently there are no clinically approved drugs that specifically target MDSCs. Methods to deplete MDSCs clinically and inhibit their immunosuppressive function will be crucial in advancing cancer treatment and to overcome treatment resistance. This review provides a detailed overview of the current understandings behind the mechanisms of MDSC-mediated suppression of anti-tumour immunity, and discusses potential strategies to target MDSC immunosuppressive mechanisms to overcome therapeutic resistance.

Targeting myeloperoxidase limits myeloid cell immunosuppression enhancing immune checkpoint therapy for pancreatic cancer

Pancreatic ductal adenocarcinoma is a devastating disease characterized by an extreme resistance to current therapies, including immune checkpoint therapy. The limited success of immunotherapies can be attributed to a highly immunosuppressive pancreatic cancer microenvironment characterized by an extensive infiltration of immune suppressing myeloid cells. While there are several pathways through which myeloid cells contribute to immunosuppression, one important mechanism is the increased production of reactive oxygen species. Here, we evaluated the contribution of myeloperoxidase, a myeloid-lineage restricted enzyme and primary source of reactive oxygen species, to regulate immune checkpoint therapy response in preclinical pancreatic cancer models. We compared treatment outcome, immune composition and characterized myeloid cells using wild-type, myeloperoxidase-deficient, and myeloperoxidase inhibitor treated wild-type mice using established subcutaneous pancreatic cancer models. Loss of host myeloperoxidase and pharmacological inhibition of myeloperoxidase in combination with immune checkpoint therapy significantly delayed tumor growth. The tumor microenvironment and systemic immune landscape demonstrated significant decreases in myeloid cells, exhausted T cells and T regulatory cell subsets when myeloperoxidase was deficient. Loss of myeloperoxidase in isolated myeloid cell subsets from tumor-bearing mice resulted in decreased reactive oxygen species production and T cell suppression. These data suggest that myeloperoxidase contributes to an immunosuppressive microenvironment and immune checkpoint therapy resistance where myeloperoxidase inhibitors have the potential to enhance immunotherapy response. Repurposing myeloperoxidase specific inhibitors may provide a promising therapeutic strategy to expand therapeutic options for pancreatic cancer patients to include immunotherapies.