Distinct Populations of Immune-Suppressive Macrophages Differentiate from Monocytic Myeloid-Derived Suppressor Cells in Cancer

Comprehensive approach to cancer immunotherapy - Simultaneous targeting of myeloid-derived suppressor cells and cancer cells with AFP conjugates

The immune system plays a pivotal role in combating diseases, including cancer, with monocytes emerging as key regulators of immune response dynamics. This article describes a novel strategy for cancer treatment centered on depleting myeloid-derived suppressor cells (MDSCs), to enhance the overall immune response while simultaneously targeting cancer cells directly. Alpha-fetoprotein (AFP) is an oncofetal protein that plays an important role in delivering nutrients to immature monocytes, embryonic, and cancer cells in a targeted manner. AFP can be repurposed, making it a vehicle for delivering toxins, rather than nutrients to kill cancer cells and deplete MDSCs in the tumor microenvironment (TME). Depleting monocytes not only stimulates the immune system but also improves the lymphocyte-to-monocyte ratio (LMR), often low in cancer patients. AFP combined with cytotoxic drugs, offers dual benefit-immune stimulation and targeted chemotherapy. Studies in xenograft models demonstrated high efficacy and safety of AFP-toxin conjugates, surpassing conventional targeted chemotherapy. Such conjugates have also been reported to provide superior efficacy and safety in cancer patients compared to chemotherapy. This approach, using AFP conjugated with toxins, either covalently or non-covalently, presents a safe and highly effective option for cancer immuno/chemotherapy.

Targeting tumor‑associated macrophages: Critical players in tumor progression and therapeutic strategies (Review)

Tumor‑associated macrophages (TAMs) are essential components of the tumor microenvironment (TME) and display phenotypic heterogeneity and plasticity associated with the stimulation of bioactive molecules within the TME. TAMs predominantly exhibit tumor‑promoting phenotypes involved in tumor progression, such as tumor angiogenesis, metastasis, immunosuppression and resistance to therapies. In addition, TAMs have the potential to regulate the cytotoxic elimination and phagocytosis of cancer cells and interact with other immune cells to engage in the innate and adaptive immune systems. In this context, targeting TAMs has been a popular area of research in cancer therapy, and a comprehensive understanding of the complex role of TAMs in tumor progression and exploration of macrophage‑based therapeutic approaches are essential for future therapeutics against cancers. The present review provided a comprehensive and updated overview of the function of TAMs in tumor progression, summarized recent advances in TAM‑targeting therapeutic strategies and discussed the obstacles and perspectives of TAM‑targeting therapies for cancers.

Decitabine suppresses MDSC-induced immunosuppression through dual functional mechanism and inhibits melanoma metastasis

Myeloid-derived suppressor cells (MDSCs) play a crucial role in promoting melanoma metastasis. Reprogramming MDSCs into mature M1 macrophages has emerged as a strategy to inhibit metastasis. Decitabine (Dec) is known to eradicate MDSCs and suppress tumor growth. In this study, we provide evidence that Dec not only reduces the MDSC population by inducing apoptosis, arresting cell cycle, and impairing recruitment, but also suppresses their immunosuppressive function by downregulating related genes and facilitating differentiation into M1 macrophages. Transcriptomic analysis of Dec-treated MDSCs revealed a marked downregulation of immunosuppressive genes including S100a9, S100a8, Vegf, Cxcr2, and Nos2. Meanwhile, M1 macrophage-associated genes involved in immune activation were upregulated, such as Ddx58, Isg15, Tap1, Ccl5, Cxcl9, and Cxcl10. Further bioinformatic analysis indicated that Dec promotes MDSC-to-M1 macrophage differentiation and activates innate immune pathways including NOD-like signaling to enhance anti-tumor immunity. Time-course studies implied that Dec upregulates myeloid transcription factor Irf7 to initiate MDSC differentiation and orchestrate the anti-tumor immune response. Collectively, our study unveils a novel dual-functional mechanism of Dec as both a cytotoxic agent reducing MDSCs and an inducer of their differentiation into M1 macrophages, thereby alleviating immunosuppression. This highlights Dec's potential for clinical melanoma metastasis suppression.

Role of Exosomes in Cancer and Aptamer-Modified Exosomes as a Promising Platform for Cancer Targeted Therapy

Exosomes are increasingly recognized as important mediators of intercellular communication in cancer biology. Exosomes can be derived from cancer cells as well as cellular components in tumor microenvironment. After secretion, the exosomes carrying a wide range of bioactive cargos can be ingested by local or distant recipient cells. The released cargos act through a variety of mechanisms to elicit multiple biological effects and impact most if not all hallmarks of cancer. Moreover, owing to their excellent biocompatibility and capability of being easily engineered or modified, exosomes are currently exploited as a promising platform for cancer targeted therapy. In this review, we first summarize the current knowledge of roles of exosomes in risk and etiology, initiation and progression of cancer, as well as their underlying molecular mechanisms. The aptamer-modified exosome as a promising platform for cancer targeted therapy is then briefly introduced. We also discuss the future directions for emerging roles of exosome in tumor biology and perspective of aptamer-modified exosomes in cancer therapy.

Netrin G1 Ligand is a new stromal immunomodulator that promotes pancreatic cancer

Understanding pancreatic cancer biology is fundamental for identifying new targets and for developing more effective therapies. In particular, the contribution of the stromal microenvironment to pancreatic cancer tumorigenesis requires further exploration. Here, we report the stromal roles of the synaptic protein Netrin G1 Ligand (NGL-1) in pancreatic cancer, uncovering its pro-tumor functions in cancer-associated fibroblasts and in immune cells. We observed that the stromal expression of NGL-1 inversely correlated with patients' overall survival. Moreover, germline knockout (KO) mice for NGL-1 presented decreased tumor burden, with a microenvironment that is less supportive of tumor growth. Of note, tumors from NGL-1 KO mice produced less immunosuppressive cytokines and displayed an increased percentage of CD8 + T cells than those from control mice, while preserving the physical structure of the tumor microenvironment. These effects were shown to be mediated by NGL-1 in both immune cells and in the local stroma, in a TGF-β-dependent manner. While myeloid cells lacking NGL-1 decreased the production of immunosuppressive cytokines, NGL-1 KO T cells showed increased proliferation rates and overall polyfunctionality compared to control T cells. CAFs lacking NGL-1 were less immunosuppressive than controls, with overall decreased production of pro-tumor cytokines and compromised ability to inhibit CD8 + T cells activation. Mechanistically, these CAFs downregulated components of the TGF-β pathway, AP-1 and NFAT transcription factor families, resulting in a less tumor-supportive phenotype. Finally, targeting NGL-1 genetically or using a functionally antagonistic small peptide phenocopied the effects of chemotherapy, while modulating the immunosuppressive tumor microenvironment (TME), rather than eliminating it. We propose NGL-1 as a new local stroma and immunomodulatory molecule, with pro-tumor roles in pancreatic cancer.

Statement of Significance

Here we uncovered the pro-tumor roles of the synaptic protein NGL-1 in the tumor microenvironment of pancreatic cancer, defining a new target that simultaneously modulates tumor cell, fibroblast, and immune cell functions. This study reports a new pathway where NGL-1 controls TGF-β, AP-1 transcription factor members and NFAT1, modulating the immunosuppressive microenvironment in pancreatic cancer. Our findings highlight NGL-1 as a new stromal immunomodulator in pancreatic cancer.

Cellular collusion: cracking the code of immunosuppression and chemo resistance in PDAC

Despite the efforts, pancreatic ductal adenocarcinoma (PDAC) is still highly lethal. Therapeutic challenges reside in late diagnosis and establishment of peculiar tumor microenvironment (TME) supporting tumor outgrowth. This stromal landscape is highly heterogeneous between patients and even in the same patient. The organization of functional sub-TME with different cellular compositions provides evolutive advantages and sustains therapeutic resistance. Tumor progressively establishes a TME that can suit its own needs, including proliferation, stemness and invasion. Cancer-associated fibroblasts and immune cells, the main non-neoplastic cellular TME components, follow soluble factors-mediated neoplastic instructions and synergize to promote chemoresistance and immune surveillance destruction. Unveiling heterotypic stromal-neoplastic interactions is thus pivotal to breaking this synergism and promoting the reprogramming of the TME toward an anti-tumor milieu, improving thus the efficacy of conventional and immune-based therapies. We underscore recent advances in the characterization of immune and fibroblast stromal components supporting or dampening pancreatic cancer progression, as well as novel multi-omic technologies improving the current knowledge of PDAC biology. Finally, we put into context how the clinic will translate the acquired knowledge to design new-generation clinical trials with the final aim of improving the outcome of PDAC patients.

Alarmin S100A8 imparts chemoresistance of esophageal cancer by reprogramming cancer-associated fibroblasts

Chemotherapy remains the first-line treatment for advanced esophageal cancer. However, durable benefits are achieved by only a limited subset of individuals due to the elusive chemoresistance. Here, we utilize patient-derived xenografts (PDXs) from esophageal squamous-cell carcinoma to investigate chemoresistance mechanisms in preclinical settings. We observe that activated cancer-associated fibroblasts (CAFs) are enriched in the tumor microenvironment of PDXs resistant to chemotherapy. Mechanistically, we reveal that cancer-cell-derived S100A8 triggers the intracellular RhoA-ROCK-MLC2-MRTF-A pathway by binding to the CD147 receptor of CAFs, inducing CAF polarization and leading to chemoresistance. Therapeutically, we demonstrate that blocking the S100A8-CD147 pathway can improve chemotherapy efficiency. Prognostically, we found the S100A8 levels in peripheral blood can serve as an indicator of chemotherapy responsiveness. Collectively, our study offers a comprehensive understanding of the molecular mechanisms underlying chemoresistance in esophageal cancer and highlights the potential value of S100A8 in the clinical management of esophageal cancer.

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Overexpressing S100A9 ameliorates NK cell dysfunction in estrogen receptor-positive breast cancer

BACKGROUND

Estrogen receptor (ER) positive human epidermal growth factor receptor 2 (HER2) negative breast cancer (ER+/HER2-BC) and triple-negative breast cancer (TNBC) are two distinct breast cancer molecular subtypes, especially in tumor immune microenvironment (TIME). The TIME of TNBC is considered to be more inflammatory than that of ER+/HER2-BC. Natural killer (NK) cells are innate lymphocytes that play an important role of tumor eradication in TME. However, studies focusing on the different cell states of NK cells in breast cancer subtypes are still inadequate.

METHODS

In this study, single-cell mRNA sequencing (scRNA-seq) and bulk mRNA sequencing data from ER+/HER2-BC and TNBC were analyzed. Key regulator of NK cell suppression in ER+/HER2-BC, S100A9, was quantified by qPCR and ELISA in MCF-7, T47D, MDA-MB-468 and MDA-MB-231 cell lines. The prognosis predictability of S100A9 and NK activation markers was evaluated by Kaplan-Meier analyses using TCGA-BRAC data. The phenotype changes of NK cells in ER+/HER2-BC after overexpressing S100A9 in cancer cells were evaluated by the production levels of IFN-gamma, perforin and granzyme B and cytotoxicity assay.

RESULTS

By analyzing scRNA-seq data, we found that multiple genes involved in cellular stress response were upregulated in ER+/HER2-BC compared with TNBC. Moreover, TLR regulation pathway was significantly enriched using differentially expressed genes (DEGs) from comparing the transcriptome data of ER+/HER2-BC and TNBC cancer cells, and NK cell infiltration high/low groups. Among the DEGs, S100A9 was identified as a key regulator. Patients with higher expression levels of S100A9 and NK cell activation markers had better overall survival. Furthermore, we proved that overexpression of S100A9 in ER+/HER2-cells could improve cocultured NK cell function.

CONCLUSION

In conclusion, the study we presented demonstrated that NK cells in ER+/HER2-BC were hypofunctional, and S100A9 was an important regulator of NK cell function in ER+BC. Our work contributes to elucidate the regulatory networks between cancer cells and NK cells and may provide theoretical basis for novel drug development.

Characterization of Immunosuppressive Myeloid Cells in Merkel Cell Carcinoma: Correlation with Resistance to PD-1 Pathway Blockade

PURPOSE

Merkel cell carcinoma (MCC) is a highly immunogenic skin cancer. Although essentially all MCCs are antigenic through viral antigens or high tumor mutation burden, MCC has a response rate of only approximately 50% to PD-(L)1 blockade suggesting barriers to T-cell responses. Prior studies of MCC immunobiology have focused on CD8 T-cell infiltration and their exhaustion status, while the role of innate immunity, particularly myeloid cells, in MCC remains underexplored.

EXPERIMENTAL DESIGN

We utilized single-cell transcriptomics from 9 patients with MCC and multiplex IHC staining of 54 patients' preimmunotherapy tumors, to identify myeloid cells and evaluate association with immunotherapy response.

RESULTS

Single-cell transcriptomics identified tumor-associated macrophages (TAM) as the dominant myeloid component within MCC tumors. These TAMs express an immunosuppressive gene signature characteristic of monocytic myeloid-derived suppressor cells and importantly express several targetable immune checkpoint molecules, including PD-L1 and LILRB receptors, that are not present on tumor cells. Analysis of 54 preimmunotherapy tumor samples showed that a subset of TAMs (CD163+, CD14+, S100A8+) selectively infiltrated tumors that had significant CD8 T cells. Indeed, higher TAM prevalence was associated with resistance to PD-1 blockade. While spatial interactions between TAMs and CD8 T cells were not associated with response, myeloid transcriptomic data showed evidence for cytokine signaling and expression of LILRB receptors, suggesting potential immunosuppressive mechanisms.

CONCLUSIONS

This study further characterizes TAMs in MCC tumors and provides insights into their possible immunosuppressive mechanism. TAMs may reduce the likelihood of treatment response in MCC by counteracting the benefit of CD8 T-cell infiltration. See related commentary by Silk and Davar, p. 1076.

Colon-targeted S100A8/A9-specific peptide systems ameliorate colitis and colitis-associated colorectal cancer in mouse models

The link between chronic inflammation and cancer development is well acknowledged. Inflammatory bowel disease including ulcerative colitis and Crohn's disease frequently promotes colon cancer development. Thus, control of intestinal inflammation is a therapeutic strategy to prevent and manage colitis-associated colorectal cancer (CRC). Recently, gut mucosal damage-associated molecular patterns S100A8 and S100A9, acting via interactions with their pattern recognition receptors (PRRs), especially TLR4 and RAGE, have emerged as key players in the pathogenesis of colonic inflammation. We found elevated serum levels of S100A8 and S100A9 in both colitis and colitis-associated CRC mouse models along with significant increases in their binding with PRR, TLR4, and RAGE. In this study we developed a dual PRR-inhibiting peptide system (rCT-S100A8/A9) that consisted of TLR4- and RAGE-inhibiting motifs derived from S100A8 and S100A9, and conjugated with a CT peptide (TWYKIAFQRNRK) for colon-specific delivery. In human monocyte THP-1 and mouse BMDMs, S100A8/A9-derived peptide comprising TLR4- and RAGE-interacting motif (0.01, 0.1, 1 μM) dose-dependently inhibited the binding of S100 to TLR4 or RAGE, and effectively inhibited NLRP3 inflammasome activation. We demonstrated that rCT-S100A8/A9 had appropriate drug-like properties including in vitro stabilities and PK properties as well as pharmacological activities. In mouse models of DSS-induced acute and chronic colitis, injection of rCT-S100A8/A9 (50 μg·kg-1·d-1, i.p. for certain consecutive days) significantly increased the survival rates and alleviated the pathological injuries of the colon. In AOM/DSS-induced colitis-associated colorectal cancer (CAC) mouse model, injection of rCT-S100A8/A9 (50 μg·kg-1·d-1, i.p.) increased the body weight, decreased tumor burden in the distal colon, and significantly alleviated histological colonic damage. In mice bearing oxaliplatin-resistant CRC xenografts, injection of rCT-S100A8/A9 (20 μg/kg, i.p., every 3 days for 24-30 days) significantly inhibited the tumor growth with reduced EMT-associated markers in tumor tissues. Our results demonstrate that targeting the S100-PRR axis improves colonic inflammation and thus highlight this axis as a potential therapeutic target for colitis and CRC.

Sexual-biased necroinflammation is revealed as a predictor of bevacizumab benefit in Glioblastoma

BACKGROUND

Glioblastoma (GBM) is a highly malignant brain tumor that affects men more often than women. In addition, the former shows a poorer survival prognosis. To date the reason for this sex-specific aggressiveness remains unclear. Therefore, the aim of this study is to investigate tumor processes that explain these sex differences.

METHODS

This was a retrospective study of GBM patients which was stratified according to sex. Cohort with 73 tumors were analyzed with immunohistochemistry, RNA-seq and RT-qPCR to characterize differences in vascular and immunological profiles. Transcriptomic profiling, GSEA and pathway enrichment analysis were used for discovery molecular pathways predominant in each group. We further investigated the therapeutic effect of Bevacizumab (VEGFA blocking antibody) in retrospective GBM cohort (36 tumors) based on sex differences.

RESULTS

We found that under hypoxic tumor conditions, two distinct tumor immuno-angiogenic ecosystems develop linked to sex differences and ESR1 expression are generated. One of these subgroups, which includes male patients with low ESR1 expression, is characterized by vascular fragility associated with the appearance of regions of necrosis and high inflammation (called necroinflamed tumors). This male-specific tumor subtype shows high inflammation related to MDSC infiltration. Using this stratification, we identified a possible group of patients who could respond to bevacizumab (BVZ) and revealed a genetic signature that may find clinical applications as a predictor of those who may benefit most from this treatment.

CONCLUSIONS

This study provides a stratification based on the sexual differences in GBM, which associates the poor prognosis with the presence of immunosuppressive myeloid cells in the necrotic areas. This new stratification could change the current prognosis of GBM and identifies those who respond to BVZ treatment.

S100A8/A9 predicts response to PIM kinase and PD-1/PD-L1 inhibition in triple-negative breast cancer mouse models

BACKGROUND

Understanding why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well remains a challenge. This study aims to understand the potential underlying mechanisms distinguishing early-stage TNBC tumors that respond to clinical intervention from non-responders, as well as to identify clinically viable therapeutic strategies, specifically for TNBC patients who may not benefit from existing therapies.

METHODS

We conducted retrospective bioinformatics analysis of historical gene expression datasets to identify a group of genes whose expression levels in early-stage tumors predict poor clinical outcomes in TNBC. In vitro small-molecule screening, genetic manipulation, and drug treatment in syngeneic mouse models of TNBC were utilized to investigate potential therapeutic strategies and elucidate mechanisms of drug action.

RESULTS

Our bioinformatics analysis reveals a robust association between increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors and subsequent disease progression in TNBC. A targeted small-molecule screen identifies PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Notably, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC.

CONCLUSIONS

Our data propose S100A8/A9 as a potential predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC. This work encourages the development of S100A8/A9-based liquid biopsy tests for treatment guidance.

Myeloid-derived suppressor cells in cancer and cancer therapy

Anticancer agents continue to dominate the list of newly approved drugs, approximately half of which are immunotherapies. This trend illustrates the considerable promise of cancer treatments that modulate the immune system. However, the immune system is complex and dynamic, and can have both tumour-suppressive and tumour-promoting effects. Understanding the full range of immune modulation in cancer is crucial to identifying more effective treatment strategies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that develop in association with chronic inflammation, which is a hallmark of cancer. Indeed, MDSCs accumulate in the tumour microenvironment, where they strongly inhibit anticancer functions of T cells and natural killer cells and exert a variety of other tumour-promoting effects. Emerging evidence indicates that MDSCs also contribute to resistance to cancer treatments, particularly immunotherapies. Conversely, treatment approaches designed to eliminate cancer cells can have important additional effects on MDSC function, which can be either positive or negative. In this Review, we discuss the interplay between MDSCs and various other cell types found in tumours as well as the mechanisms by which MDSCs promote tumour progression. We also discuss the relevance and implications of MDSCs for cancer therapy.

Single-cell analysis of immune and stroma cell remodeling in clear cell renal cell carcinoma primary tumors and bone metastatic lesions

BACKGROUND

Despite therapeutic advances, once a cancer has metastasized to the bone, it represents a highly morbid and lethal disease. One third of patients with advanced clear cell renal cell carcinoma (ccRCC) present with bone metastasis at the time of diagnosis. However, the bone metastatic niche in humans, including the immune and stromal microenvironments, has not been well-defined, hindering progress towards identification of therapeutic targets.

METHODS

We collected fresh patient samples and performed single-cell transcriptomic profiling of solid metastatic tissue (Bone Met), liquid bone marrow at the vertebral level of spinal cord compression (Involved), and liquid bone marrow from a different vertebral body distant from the tumor site but within the surgical field (Distal), as well as bone marrow from patients undergoing hip replacement surgery (Benign). In addition, we incorporated single-cell data from primary ccRCC tumors (ccRCC Primary) for comparative analysis.

RESULTS

The bone marrow of metastatic patients is immune-suppressive, featuring increased, exhausted CD8 + cytotoxic T cells, T regulatory cells, and tumor-associated macrophages (TAM) with distinct transcriptional states in metastatic lesions. Bone marrow stroma from tumor samples demonstrated a tumor-associated mesenchymal stromal cell population (TA-MSC) that appears to be supportive of epithelial-to mesenchymal transition (EMT), bone remodeling, and a cancer-associated fibroblast (CAFs) phenotype. This stromal subset is associated with poor progression-free and overall survival and also markedly upregulates bone remodeling through the dysregulation of RANK/RANKL/OPG signaling activity in bone cells, ultimately leading to bone resorption.

CONCLUSIONS

These results provide a comprehensive analysis of the bone marrow niche in the setting of human metastatic cancer and highlight potential therapeutic targets for both cell populations and communication channels.

Progress in understanding of relationship between inflammation and tumors

Over the past decade, there has been clear evidence that inflammation plays a key role in tumorigenesis. Tumor extrinsic inflammation is caused by many factors, including bacterial and viral infections, autoimmune diseases, obesity, smoking, excessive alcohol consumption, etc., all of which can increase cancer risk and stimulate malignant progression. Conversely, inflammation inherent in cancer or caused by cancer can be triggered by cancer-initiating mutations and can promote malignant progression through recruitment and activation of inflammatory cells. Both exogenous and endogenous inflammation can lead to immunosuppression, thus providing a preferred opportunity for tumor development. Studies have confirmed that chronic inflammation is involved in various steps of tumorigenesis, including cell transformation, promotion, survival, prolifer-ation, invasion, angiogenesis, and metastasis. Recent research has shed new light on the molecular and cellular circuits between inflammation and cancer. Two pathways have been preliminarily identified: Intrinsic and extrinsic. In the intrinsic pathway, genetic events leading to tumors initiate the expression of inflammatory related programs and guide the construction of the inflammatory microenvironment. In the extrinsic pathway, inflammatory conditions promote the development of cancer. This article reviews the recent progress in the understanding of the relationship between inflammation and tumors.

VISTA promotes the metabolism and differentiation of myeloid-derived suppressor cells by STAT3 and polyamine-dependent mechanisms

Myeloid-derived suppressor cells (MDSCs) impair antitumor immune responses. Identifying regulatory circuits during MDSC development may bring new opportunities for therapeutic interventions. We report that the V-domain suppressor of T cell activation (VISTA) functions as a key enabler of MDSC differentiation. VISTA deficiency reduced STAT3 activation and STAT3-dependent production of polyamines, which causally impaired mitochondrial respiration and MDSC expansion. In both mixed bone marrow (BM) chimera mice and myeloid-specific VISTA conditional knockout mice, VISTA deficiency significantly reduced tumor-associated MDSCs but expanded monocyte-derived dendritic cells (DCs) and enhanced T cell-mediated tumor control. Correlated expression of VISTA and arginase-1 (ARG1), a key enzyme supporting polyamine biosynthesis, was observed in multiple human cancer types. In human endometrial cancer, co-expression of VISTA and ARG1 on tumor-associated myeloid cells is associated with poor survival. Taken together, these findings unveil the VISTA/polyamine axis as a central regulator of MDSC differentiation and warrant therapeutically targeting this axis for cancer immunotherapy.

Targeting tumor-associated macrophages: Novel insights into immunotherapy of skin cancer

BACKGROUND

The incidence of skin cancer is currently increasing, and conventional treatment options inadequately address the demands of disease management. Fortunately, the recent rapid advancement of immunotherapy, particularly immune checkpoint inhibitors (ICIs), has ushered in a new era for numerous cancer patients. However, the efficacy of immunotherapy remains suboptimal due to the impact of the tumor microenvironment (TME). Tumor-associated macrophages (TAMs), a major component of the TME, play crucial roles in tumor invasion, metastasis, angiogenesis, and immune evasion, significantly impacting tumor development. Consequently, TAMs have gained considerable attention in recent years, and their roles have been extensively studied in various tumors. However, the specific roles of TAMs and their regulatory mechanisms in skin cancer remain unclear.

AIM OF REVIEW

This paper aims to elucidate the origin and classification of TAMs, investigate the interactions between TAMs and various immune cells, comprehensively understand the precise mechanisms by which TAMs contribute to the pathogenesis of different types of skin cancer, and finally discuss current strategies for targeting TAMs in the treatment of skin cancer.

KEY SCIENTIFIC CONCEPTS OF OVERVIEW

With a specific emphasis on the interrelationship between TAMs and skin cancer, this paper posits that therapeutic modalities centered on TAMs hold promise in augmenting and harmonizing with prevailing clinical interventions for skin cancer, thereby charting a novel trajectory for advancing the landscape of immunotherapeutic approaches for skin cancer.

S100A9 Induces Macrophage M2 Polarization and Immunomodulatory Role in the Lesion Site After Spinal Cord Injury in Rats

Immune response is pivotal in the secondary injury of spinal cord injury (SCI). Polarization of macrophages (MΦ) influences the immune response in the secondary injury, which is regulated by several immune-related proteins. M2Φ plays the immunomodulatory role in the central nervous system. This study used bioinformatic analysis and machine algorithms to screen hub immune-related proteins after SCI and experimentally investigate the role of the target protein in the M2Φ polarization and immunomodulation in rats and in vitro after SCI. We downloaded GSE151371 and GSE45006, hub immune-related genes were screened using machine learning algorithms, and the expression of S100A9 was verified by datasets. Allen's weight-drop injury SCI model in Sprague-Dawley rat and bone marrow-derived rat MΦ with myelin debris model were used to study the effects of S100A9 on M2Φ polarization and immunomodulation at the lesion site and in vitro. Bioinformatic analysis showed that S100A9 acts as a hub immune-related gene in the SCI patients and rats. S100A9 increased at the lesion site in SCI rats, and its inhibition reduced CD206 and ARG-1 expression. Exogenous S100A9 promoted CD206 and ARG-1 expression in MΦ. S100A9 also increased the expression of PD-L1 and decreased MHC II at the lesion site in SCI rats and MΦ with myelin debris, and enhanced mitochondrial activity in rat MΦ with myelin debris. In conclusion, S100A9 is an indispensable factor in the immune process in secondary injury following SCI.

Immunomodulatory actions of myeloid-derived suppressor cells in the context of innate immunity

Myeloid-derived suppressor cells (MDSCs) are notable innate immune cells, which are further divided into two subpopulations, i.e., monocytic and granulocytic. These cells are traditionally considered to mainly suppress the T-cell responses. However, more updated data indicate that their properties are rather immunomodulatory than solely immunosuppressive. Indeed, MDSCs display extensive crosstalk with other either innate or adaptive immune cells, and, according to the situation under which they are triggered, they may enhance or attenuate the immune response. However, their positive role in host's defense mechanisms under specific conditions is rarely discussed in the literature. In this mini-review, the authors briefly summarise the mechanisms of action of MDSCs under distinct conditions, such as infections and malignancies, with a particular emphasis on their role as components of the innate immunity system.

Protein kinase C delta regulates mononuclear phagocytes and hinders response to immunotherapy in cancer

Mononuclear phagocytes (MPs) play a crucial role in tissue homeostasis; however, MPs also contribute to tumor progression and resistance to immune checkpoint blockade (ICB). Targeting MPs could be an effective strategy to enhance ICB efficacy. We report that protein kinase C delta (PKCδ), a serine/threonine kinase, is abundantly expressed by MPs in human and mouse tumors. PKCδ-/- mice displayed reduced tumor progression compared to wild types, with increased response to anti-PD-1. Tumors from PKCδ-/- mice demonstrated TH1-skewed immune response including increased antigen presentation and T cell activation. Depletion of MPs in vivo altered tumor growth in control but not PKCδ-/- mice. Coinjection of PKCδ-/- M2-like macrophages with cancer cells into wild-type mice markedly delayed tumor growth and significantly increased intratumoral T cell activation compared to PKCδ+/+ controls. PKCδ deficiency reprogrammed MPs by activating type I and type II interferon signaling. Thus, PKCδ might be targeted to reprogram MPs to augment ICB efficacy.

In vitro generation of murine myeloid-derived suppressor cells from hematopoietic progenitor cells

One of the hallmarks of cancer is the expansion and accumulation of highly immunosuppressive myeloid cells known as myeloid-derived suppressor cells (MDSCs). To study MDSCs biology, differentiation from hematopoietic progenitor cells (HPC) is an useful tool to elucidate the biological and biochemical mechanisms associated with acquisition of immune suppressive activity and expansion in cancer. Although this is one of the protocols performed to study immune suppressive myeloid cells, differentiation of MDSCs from HPC is a method that allows to modify conditions of the supernatants used. In this protocol, we outline the process of differentiating HPCs into MDSCs in vitro using tumor explant supernatants to recapitulate the tumor microenvironment.

Myeloid-derived suppressor cells and tolerogenic dendritic cells are distinctively induced by PI3K and Wnt signaling pathways

Imbalanced immune responses are a prominent hallmark of cancer and autoimmunity. Myeloid cells can be overly suppressive, inhibiting protective immune responses or inactive not controlling autoreactive immune cells. Understanding the mechanisms that induce suppressive myeloid cells, such as myeloid-derived suppressor cells (MDSCs) and tolerogenic dendritic cells (TolDCs), can facilitate the development of immune-restoring therapeutic approaches. MDSCs are a major barrier for effective cancer immunotherapy by suppressing antitumor immune responses in cancer patients. TolDCs are administered to patients to promote immune tolerance with the intent to control autoimmune disease. Here, we investigated the development and suppressive/tolerogenic activity of human MDSCs and TolDCs to gain insight into signaling pathways that drive immunosuppression in these different myeloid subsets. Moreover, monocyte-derived MDSCs (M-MDSCs) generated in vitro were compared to M-MDSCs isolated from head-and-neck squamous cell carcinoma patients. PI3K-AKT signaling was identified as being crucial for the induction of human M-MDSCs. PI3K inhibition prevented the downregulation of HLA-DR and the upregulation of reactive oxygen species and MerTK. In addition, we show that the suppressive activity of dexamethasone-induced TolDCs is induced by β-catenin-dependent Wnt signaling. The identification of PI3K-AKT and Wnt signal transduction pathways as respective inducers of the immunomodulatory capacity of M-MDSCs and TolDCs provides opportunities to overcome suppressive myeloid cells in cancer patients and optimize therapeutic application of TolDCs. Lastly, the observed similarities between generated- and patient-derived M-MDSCs support the use of in vitro-generated M-MDSCs as powerful model to investigate the functionality of human MDSCs.

Construction of a novel prognostic model in skin cutaneous melanoma based on chemokines-related gene signature

Skin cutaneous melanoma, SKCM, is one of the most aggressive treatment-resistant tumours. Despite the fact that the BRAF oncogene and immunological checkpoints such as PD-1/PD-L1 and CTLA-4 have enhanced the therapeutic efficacy of SKCM, the subsequent resistance mechanisms and remedies have raised concerns. Chemokines have a significant role in the immunological milieu of tumor, which may increase the efficacy of checkpoint blockade and serve as a possible therapeutic intervention route. However, there is still no chemokine-based typing and risk model to provide a prognosis and therapeutic efficacy assessment for SKCM patients. In this study, we verified the distinct differences of prognostic stratification as well as immune characteristics between two chemokine-related clusters in SKCM patients. Two clusters of DEGs were discovered to be primarily enriched in B and T cell receptor signaling pathways as well as TNF signaling via NF-kappa-B. Based on 14 prognosis-related DEGs from aforementioned two clusters (CCL8, GBP2, GBP4, SRNG, HLA-DMB, RARRES3, HLA-DQA1, PARP12, APOL3, IRF1, HLA-DRA, UBE2L6, IL2RA and CD38), a chemokine-related 14-gene prognostic model was established. At the same time, researchers explored differences between the low-risk and high-risk groups in clinical traits, the proportion of infiltration of 22 different types of immune cells, and how well medications worked. The risk score model's immunotherapy and prognostic predictions were also confirmed in testing groups. Based on the finding, we can claim that there is a clear link between chemokines and TME in SKCM. The risk score may perform as a trustworthy prediction model, giving therapeutic benefits for both chemotherapy and immunotherapy, as well as being beneficial for clinical decision making in SKCM patients.

S100A8/A9 predicts triple-negative breast cancer response to PIM kinase and PD-1/PD-L1 inhibition

It remains elusive why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well. Our retrospective analysis of historical gene expression datasets reveals that increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors is robustly associated with subsequent disease progression in TNBC. Although it has recently gained recognition as a potential anticancer target, S100A8/A9 has not been integrated into clinical study designs evaluating molecularly targeted therapies. Our small molecule screen has identified PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Furthermore, combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Importantly, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC. Thus, our data suggest that S100A8/A9 could be a predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC and encourage the development of S100A8/A9-based liquid biopsy tests.

Successful treatment with carboplatin and paclitaxel in melanoma progression after immune-related adverse events

The overall survival of melanoma patients has improved using antibodies targeting immune checkpoints (anti-PD-1, anti-CTLA-4 and anti-LAG-3). Systemic chemotherapy was administered in melanoma for many years with limited effectiveness. Here we report a case of a patient who experienced immune-mediated adverse effects from checkpoint blockade therapy and subsequently responded to chemotherapy. The patient presented with melanoma and paraneoplastic digital ischemia. She received a combination of ipilimumab/nivolumab and experienced G3 myocarditis, followed by melanoma progression after a steroid taper. This patient achieved a partial and durable response with platinum and taxane-based chemotherapy. This report suggests the possibility of a subset of patients who experience progression after immune-based side effects where chemotherapy may be effective in the modern age of melanoma treatment.

M1/M2 macrophages and their overlaps - myth or reality?

Macrophages represent heterogeneous cell population with important roles in defence mechanisms and in homoeostasis. Tissue macrophages from diverse anatomical locations adopt distinct activation states. M1 and M2 macrophages are two polarized forms of mononuclear phagocyte in vitro differentiation with distinct phenotypic patterns and functional properties, but in vivo, there is a wide range of different macrophage phenotypes in between depending on the microenvironment and natural signals they receive. In human infections, pathogens use different strategies to combat macrophages and these strategies include shaping the macrophage polarization towards one or another phenotype. Macrophages infiltrating the tumours can affect the patient's prognosis. M2 macrophages have been shown to promote tumour growth, while M1 macrophages provide both tumour-promoting and anti-tumour properties. In autoimmune diseases, both prolonged M1 activation, as well as altered M2 function can contribute to their onset and activity. In human atherosclerotic lesions, macrophages expressing both M1 and M2 profiles have been detected as one of the potential factors affecting occurrence of cardiovascular diseases. In allergic inflammation, T2 cytokines drive macrophage polarization towards M2 profiles, which promote airway inflammation and remodelling. M1 macrophages in transplantations seem to contribute to acute rejection, while M2 macrophages promote the fibrosis of the graft. The view of pro-inflammatory M1 macrophages and M2 macrophages suppressing inflammation seems to be an oversimplification because these cells exploit very high level of plasticity and represent a large scale of different immunophenotypes with overlapping properties. In this respect, it would be more precise to describe macrophages as M1-like and M2-like.

The recent progress of myeloid-derived suppressor cell and its targeted therapies in cancers

Myeloid-derived suppressor cells (MDSCs) are an immature group of myeloid-derived cells generated from myeloid cell precursors in the bone marrow. MDSCs appear almost exclusively in pathological conditions, such as tumor progression and various inflammatory diseases. The leading function of MDSCs is their immunosuppressive ability, which plays a crucial role in tumor progression and metastasis through their immunosuppressive effects. Since MDSCs have specific molecular features, and only a tiny amount exists in physiological conditions, MDSC-targeted therapy has become a promising research direction for tumor treatment with minimal side effects. In this review, we briefly introduce the classification, generation and maturation process, and features of MDSCs, and detail their functions under various circumstances. The present review specifically demonstrates the environmental specificity of MDSCs, highlighting the differences between MDSCs from cancer and healthy individuals, as well as tumor-infiltrating MDSCs and circulating MDSCs. Then, we further describe recent advances in MDSC-targeted therapies. The existing and potential targeted drugs are divided into three categories, monoclonal antibodies, small-molecular inhibitors, and peptides. Their targeting mechanisms and characteristics have been summarized respectively. We believe that a comprehensive in-depth understanding of MDSC-targeted therapy could provide more possibilities for the treatment of cancer.

Ferroptosis of immune cells in the tumor microenvironment

Ferroptosis is a distinct form of cell death driven by the accumulation of peroxidized lipids. Characterized by alterations in redox lipid metabolism, ferroptosis has been implicated in a variety of cellular processes, including cancer. Induction of ferroptosis is considered a novel way to kill tumor cells, especially cells resistant to radiation and chemotherapy. However, in recent years, a new paradigm has emerged. In addition to promoting tumor cell death, ferroptosis causes potent immune suppression in the tumor microenvironment (TME) by affecting both innate and adaptive immune responses. In this review, we discuss the dual role of ferroptosis in the antitumor and protumorigenic functions of immune cells in cancer. We suggest strategies for targeting ferroptosis, taking into account its ambiguous role in cancer.

Immunologically active ferumoxytol-poly(I : C) nanomaterials inhibit metastatic melanoma by regulating myeloid-derived suppressor cell differentiation

Nanomaterials have been identified as a potential therapeutic option for targeting myeloid-derived suppressor cells (MDSCs), which are known to play a crucial role in tumor metastasis and treatment resistance. Here, we report a unique immunologically active nanomaterial composed of ferumoxytol and poly(I : C) (FP-NPs) and investigate its immunoregulatory activities on MDSCs in metastatic melanoma. In vivo assays demonstrated that FP-NPs had the ability to significantly impede the progression of metastatic melanoma and decrease the MDSC population in the lungs, spleen, and bone marrow of mice. Both in vivo and in vitro experiments revealed that FP-NPs reduced the number of granulocytic MDSCs and promoted the differentiation of monocytic MDSCs into anti-tumor M1 macrophages. Transcriptome sequencing indicated that FP-NPs significantly altered the expression of several genes involved in immunity. Analysis of Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and quantitative real-time PCR revealed that FP-NPs significantly increased the expression of the myeloid cell differentiation-related gene interferon regulatory factor 7 and activated interferon beta-related signaling pathways, which stimulated the differentiation of MDSCs into M1 macrophages. These findings suggest that FP-NPs, a unique nanomaterial with immunological properties, can induce MDSCs to differentiate into M1 macrophages, potentially offering new treatment prospects for metastatic melanoma in the future.

Tumor-associated fibrosis impairs immune surveillance and response to immune checkpoint blockade in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths. Immune checkpoint blockade has improved survival for many patients with NSCLC, but most fail to obtain long-term benefit. Understanding the factors leading to reduced immune surveillance in NSCLC is critical in improving patient outcomes. Here, we show that human NSCLC harbors large amounts of fibrosis that correlates with reduced T cell infiltration. In murine NSCLC models, the induction of fibrosis led to increased lung cancer progression, impaired T cell immune surveillance, and failure of immune checkpoint blockade efficacy. Associated with these changes, we observed that fibrosis leads to numerically and functionally impaired dendritic cells and altered macrophage phenotypes that likely contribute to immunosuppression. Within cancer-associated fibroblasts, distinct changes within the Col13a1-expressing population suggest that these cells produce chemokines to recruit macrophages and regulatory T cells while limiting recruitment of dendritic cells and T cells. Targeting fibrosis through transforming growth factor-β receptor signaling overcame the effects of fibrosis to enhance T cell responses and improved the efficacy of immune checkpoint blockade but only in the context of chemotherapy. Together, these data suggest that fibrosis in NSCLC leads to reduced immune surveillance and poor responsiveness to checkpoint blockade and highlight antifibrotic therapies as a candidate strategy to overcome immunotherapeutic resistance.

Chronic adrenergic stress and generation of myeloid-derived suppressor cells: Implications for cancer immunotherapy in dogs

Recent studies have highlighted a key role played by the sympathetic nervous system (SNS) and adrenergic stress in mediating immune suppression associated with chronic inflammation in cancer and other diseases. The connection between chronic SNS activation, adrenergic stress and immune suppression is linked in part to the ability of catecholamines to stimulate the bone marrow release and differentiation of myeloid-derived suppressor cells (MDSC). Rodent model studies have revealed an important role for β-adrenergic receptor signalling in suppression of cancer immunity in mice subjected to chronic stresses, including thermal stress. Importantly, therapeutic blockade of beta-adrenergic responses by drugs such as propranolol can partially reverse the generation and differentiation of MDSC, and partly restore tumour immunity. Clinical trials in both humans and dogs with cancer have demonstrated that propranolol blockade can improve responses to radiation therapy, cancer vaccines and immune checkpoint inhibitors. Thus, the SNS stress response has become an important new target to relieve immune suppression in cancer and other chronic inflammatory conditions.

Serum immune mediators as novel predictors of response to anti-PD-1/PD-L1 therapy in non-small cell lung cancer patients with high tissue-PD-L1 expression

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related morbidity and mortality worldwide. Immune checkpoint inhibitors (ICIs) including anti-PD-1 and anti-PD-L1 antibodies, have significantly changed the treatment outcomes with better overall survival, but only 15-40% of the patients respond to ICIs therapy. The search for predictive biomarkers of responses is warranted for better clinical outcomes. We aim here to identify pre-treatment soluble immune molecules as surrogate biomarkers for tissue PD-L1 (TPD-L1) status and as predictors of response to anti-PD-1/PD-L1 therapy in NSCLC patients. Sera from 31 metastatic NSCLC patients, eligible for anti-PD-1/PD-L1 or combined chemoimmunotherapy, were collected prior to treatment. Analysis of soluble biomarkers with TPD-L1 status showed significant up/down regulation of the immune inhibitory checkpoint markers (sSiglec7, sSiglec9, sULBP4 and sPD-L2) in patients with higher TPD-L1 (TPD-L1 >50%) expression. Moreover, correlation analysis showed significant positive linear correlation of soluble PD-L1 (sPD-L1) with higher TPD-L1 expression. Interestingly, only responders in the TPD-L1 >50% group showed significant down regulation of the immune inhibitory markers (sPD-L2, sTIMD4, sNectin2 and CEA). When responders vs. non-responders were compared, significant down regulation of other immune inhibitory biomarkers (sCD80, sTIMD4 and CEA) was recorded only in responding patients. In this, the optimal cut-off values of CD80 <91.7 pg/ml and CEA <1614 pg/ml were found to be significantly associated with better progression free survival (PFS). Indeed, multivariate analysis identified the cutoff-value of CEA <1614 pg/ml as an independent predictor of response in our patients. We identified here novel immune inhibitory/stimulatory soluble mediators as potential surrogate/predictive biomarkers for TPD-L1 status, treatment response and PFS in NSCLC patients treated with anti-PD-1/PD-L1 therapy.

Immunosuppressive cells in oncolytic virotherapy for glioma: challenges and solutions

Glioblastoma is a highly aggressive form of brain cancer characterized by the abundance of myeloid lineage cells in the tumor microenvironment. Tumor-associated macrophages and microglia (TAM) and myeloid-derived suppressor cells (MDSCs), play a pivotal role in promoting immune suppression and tumor progression. Oncolytic viruses (OVs) are self-amplifying cytotoxic agents that can stimulate local anti-tumor immune responses and have the potential to suppress immunosuppressive myeloid cells and recruit tumor-infiltrating T lymphocytes (TILs) to the tumor site, leading to an adaptive immune response against tumors. However, the impact of OV therapy on the tumor-resident myeloid population and the subsequent immune responses are not yet fully understood. This review provides an overview of how TAM and MDSC respond to different types of OVs, and combination therapeutics that target the myeloid population to promote anti-tumor immune responses in the glioma microenvironment.

Type I interferon response in astrocytes promotes brain metastasis by enhancing monocytic myeloid cell recruitment

Cancer metastasis to the brain is a significant clinical problem. Metastasis is the consequence of favorable interactions between invaded cancer cells and the microenvironment. Here, we demonstrate that cancer-activated astrocytes create a sustained low-level activated type I interferon (IFN) microenvironment in brain metastatic lesions. We further confirm that the IFN response in astrocytes facilitates brain metastasis. Mechanistically, IFN signaling in astrocytes activates C-C Motif Chemokine Ligand 2 (CCL2) production, which further increases the recruitment of monocytic myeloid cells. The correlation between CCL2 and monocytic myeloid cells is confirmed in clinical brain metastasis samples. Lastly, genetically or pharmacologically inhibiting C-C Motif Chemokine Receptor 2 (CCR2) reduces brain metastases. Our study clarifies a pro-metastatic effect of type I IFN in the brain even though IFN response has been considered to have anti-tumor effects. Moreover, this work expands our understandings on the interactions between cancer-activated astrocytes and immune cells in brain metastasis.

Here, There, and Everywhere: Myeloid-Derived Suppressor Cells in Immunology

Myeloid-derived suppressor cells (MDSCs) were initially identified in humans and mice with cancer where they profoundly suppress T cell- and NK cell-mediated antitumor immunity. Inflammation is a central feature of many pathologies and normal physiological conditions and is the dominant driving force for the accumulation and function of MDSCs. Therefore, MDSCs are present in conditions where inflammation is present. Although MDSCs are detrimental in cancer and conditions where cellular immunity is desirable, they are beneficial in settings where cellular immunity is hyperactive. Because MDSCs can be generated ex vivo, they are being exploited as therapeutic agents to reduce damaging cellular immunity. In this review, we discuss the detrimental and beneficial roles of MDSCs in disease settings such as bacterial, viral, and parasitic infections, sepsis, obesity, trauma, stress, autoimmunity, transplantation and graft-versus-host disease, and normal physiological settings, including pregnancy and neonates as well as aging. The impact of MDSCs on vaccination is also discussed.

Redox phospholipidomics discovers pro-ferroptotic death signals in A375 melanoma cells in vitro and in vivo

Growing cancer cells effectively evade most programs of regulated cell death, particularly apoptosis. This necessitates a search for alternative therapeutic modalities to cause cancer cell's demise, among them - ferroptosis. One of the obstacles to using pro-ferroptotic agents to treat cancer is the lack of adequate biomarkers of ferroptosis. Ferroptosis is accompanied by peroxidation of polyunsaturated species of phosphatidylethanolamine (PE) to hydroperoxy- (-OOH) derivatives, which act as death signals. We demonstrate that RSL3-induced death of A375 melanoma cells in vitro was fully preventable by ferrostatin-1, suggesting their high susceptibility to ferroptosis. Treatment of A375 cells with RSL3 caused a significant accumulation of PE-(18:0/20:4-OOH) and PE-(18:0/22:4-OOH), the biomarkers of ferroptosis, as well as oxidatively truncated products - PE-(18:0/hydroxy-8-oxo-oct-6-enoic acid (HOOA) and PC-(18:0/HOOA). A significant suppressive effect of RSL3 on melanoma growth was observed in vivo (utilizing a xenograft model of inoculation of GFP-labeled A375 cells into immune-deficient athymic nude mice). Redox phospholipidomics revealed elevated levels of 18:0/20:4-OOH in RSL3-treated group vs controls. In addition, PE-(18:0/20:4-OOH) species were identified as major contributors to the separation of control and RSL3-treated groups, with the highest variable importance in projection predictive score. Pearson correlation analysis revealed an association between tumor weight and contents of PE-(18:0/20:4-OOH) (r = -0.505), PE-18:0/HOOA (r = -0.547) and PE 16:0-HOOA (r = -0.503). Thus, LC-MS/MS based redox lipidomics is a sensitive and precise approach for the detection and characterization of phospholipid biomarkers of ferroptosis induced in cancer cells by radio- and chemotherapy.

Beta glucan as an immune stimulant in tumor microenvironment - Insight into lessons and promises from past decade

Cancer is characterized by a perturbed immune landscape. Inside tumor microenvironment, immune system is reprogrammed to facilitate tumor growth and survival rather than eliminating it. This immune evasive mechanism needs to be reversed to normal for effective anticancer therapeutic strategy. Immunotherapy has emerged as a novel strategy for redeployment of immune cells against cancer. However, they suffer in their efficacy, response rate and side effects. This necessitated us to turn toward natural repertoires which can act as a substitute to conventional immunotherapeutics. Beta glucan, a polysaccharide derived from mushroom, serves the role of immunomodulator inside tumor microenvironment. It acts as pathogen associated molecular pattern and bind to various pattern recognition receptors expressed on surface of immune cells thereby facilitating their activation and crosstalk. This result in resurgence of suppressed immune surveillance in the tumor milieu. In this review, we highlight in brief the advances and limitation of cancer immunotherapy. Alongside, we have discussed the detailed mechanistic principle and recent advances underlying restoration of immune functionality by beta glucan.

Therapeutic targeting of tumour myeloid cells

Myeloid cells are pivotal within the immunosuppressive tumour microenvironment. The accumulation of tumour-modified myeloid cells derived from monocytes or neutrophils - termed 'myeloid-derived suppressor cells' - and tumour-associated macrophages is associated with poor outcome and resistance to treatments such as chemotherapy and immune checkpoint inhibitors. Unfortunately, there has been little success in large-scale clinical trials of myeloid cell modulators, and only a few distinct strategies have been used to target suppressive myeloid cells clinically so far. Preclinical and translational studies have now elucidated specific functions for different myeloid cell subpopulations within the tumour microenvironment, revealing context-specific roles of different myeloid cell populations in disease progression and influencing response to therapy. To improve the success of myeloid cell-targeted therapies, it will be important to target tumour types and patient subsets in which myeloid cells represent the dominant driver of therapy resistance, as well as to determine the most efficacious treatment regimens and combination partners. This Review discusses what we can learn from work with the first generation of myeloid modulators and highlights recent developments in modelling context-specific roles for different myeloid cell subtypes, which can ultimately inform how to drive more successful clinical trials.

Myeloid cells in the era of cancer immunotherapy: Top 3 unanswered questions

Myeloid cells are increasingly being recognized as central players orchestrating or suppressing antitumor immune responses. With the advent of high-resolution analytical methods such as single-cell technologies, we now appreciate the heterogeneity and complexity of the myeloid compartment in the context of cancer. Because of their highly plastic nature, targeting myeloid cells has shown promising results either as a monotherapy or in combination with immunotherapy in preclinical models and cancer patients. However, the complexity of myeloid cell cellular crosstalk and molecular networks contributes to our poor understanding of the different myeloid cell subsets in tumorigenesis, which makes targeting myeloid cells challenging. Here, we summarize varied myeloid cell subsets and their contribution to tumor progression with a main focus on mononuclear phagocytes. The top three unanswered questions challenging the field of myeloid cells and cancer in the era of cancer immunotherapy are addressed. Through these questions, we discuss how myeloid cell origin and identity influence their function and disease outcomes. Different therapeutic strategies used to target myeloid cells in cancer are also addressed. Finally, the durability of myeloid cell targeting is interrogated by examining the complexity of resultant compensatory cellular and molecular mechanisms.

Reprogramming the tumor microenvironment leverages CD8+ T cell responses to a shared tumor/self antigen in ovarian cancer

Tumor antigen-driven responses to weakly immunogenic self-antigens and neoantigens directly affect treatment efficacy following immunotherapy. Using orthotopically grown SV40 T antigen+ ovarian carcinoma in antigen-naive wild-type or TgMISIIR-TAg-Low transgenic mice expressing SV40 T antigen as a self-antigen, we investigated the impact of CXCR4-antagonist-armed oncolytic virotherapy on tumor progression and antitumor immunity. Immunostaining and single-cell RNA sequencing analyses of the peritoneal tumor microenvironment of untreated tumors in syngeneic wild-type mice revealed the presence of SV40 T antigen-specific CD8+ T cells, a balanced M1/M2 transcriptomic signature of tumor-associated macrophages, and immunostimulatory cancer-associated fibroblasts. This contrasted with polarized M2 tumor-associated macrophages, immunosuppressive cancer-associated fibroblasts, and poor immune activation in TgMISIIR-TAg-Low mice. Intraperitoneal delivery of CXCR4-antagonist-armed oncolytic vaccinia virus led to nearly complete depletion of cancer-associated fibroblasts, M1 polarization of macrophages, and generation of SV40 T antigen-specific CD8+ T cells in transgenic mice. Cell depletion studies revealed that the therapeutic effect of armed oncolytic virotherapy was dependent primarily on CD8+ cells. These results demonstrate that targeting the interaction between immunosuppressive cancer-associated fibroblasts and macrophages in the tolerogenic tumor microenvironment by CXCR4-A-armed oncolytic virotherapy induces tumor/self-specific CD8+ T cell responses and consequently increases therapeutic efficacy in an immunocompetent ovarian cancer model.

Functional states of myeloid cells in cancer

Myeloid cells, comprised of macrophages, dendritic cells, monocytes, and granulocytes, represent a major component of the tumor microenvironment (TME) and are critically involved in regulation of tumor progression and metastasis. In recent years, single-cell omics technologies have identified multiple phenotypically distinct subpopulations. In this review, we discuss recent data and concepts suggesting that the biology of myeloid cells is largely defined by a very limited number of functional states that transcend the narrowly defined cell populations. These functional states are primarily centered around classical and pathological states of activation, with the latter state commonly defined as myeloid-derived suppressor cells. We discuss the concept that lipid peroxidation of myeloid cells represents a major mechanism that governs their pathological state of activation in the TME. Lipid peroxidation is associated with ferroptosis mediating suppressive activity of these cells and thus could be considered an attractive target for therapeutic intervention.

The role of myeloid-derived immunosuppressive cells in cardiovascular disease

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population found in the bone marrow, peripheral blood, and tumor tissue. Their role is mainly to inhibit the monitoring function of innate and adaptive immune cells, which leads to the escape of tumor cells and promotes tumor development and metastasis. Moreover, recent studies have found that MDSCs are therapeutic in several autoimmune disorders due to their strong immunosuppressive ability. Additionally, studies have found that MDSCs have an important role in the formation and progression of other cardiovascular diseases, such as atherosclerosis, acute coronary syndrome, and hypertension. In this review, we will discuss the role of MDSCs in the pathogenesis and treatment of cardiovascular disease.

S100A8 and S100A9 in Cancer

S100A8 and S100A9 are Ca²⁺ binding proteins that belong to the S100 family. Primarily expressed in neutrophils and monocytes, S100A8 and S100A9 play critical roles in modulating various inflammatory responses and inflammation-associated diseases. Forming a common heterodimer structure S100A8/A9, S100A8 and S100A9 are widely reported to participate in multiple signaling pathways in tumor cells. Meanwhile, S100A8/A9, S100A8, and S100A9, mainly as promoters, contribute to tumor development, growth and metastasis by interfering with tumor metabolism and the microenvironment. In recent years, the potential of S100A8/A9, S100A9, and S100A8 as tumor diagnostic or prognostic biomarkers has also been demonstrated. In addition, an increasing number of potential therapies targeting S100A8/A9 and related signaling pathways have emerged. In this review, we will first expound on the characteristics of S100A8/A9, S100A9, and S100A8 in-depth, focus on their interactions with tumor cells and microenvironments, and then discuss their clinical applications as biomarkers and therapeutic targets. We also highlight current limitations and look into the future of S100A8/A9 targeted anti-cancer therapy.

S100A8/S100A9 Promote Progression of Multiple Myeloma via Expansion of Megakaryocytes

Multiple myeloma is characterized by clonal proliferation of plasma cells that accumulate preferentially in the bone marrow (BM). The tumor microenvironment is one of the leading factors that promote tumor progression. Neutrophils and monocytes are a major part of the BM tumor microenvironment, but the mechanism of their contribution to multiple myeloma progression remains unclear. Here, we describe a novel mechanism by which S100A8/S100A9 proteins produced by BM neutrophils and monocytes promote the expansion of megakaryocytes supporting multiple myeloma progression. S100A8/S100A9 alone was not sufficient to drive megakaryopoiesis but markedly enhanced the effect of thrombopoietin, an effect that was mediated by Toll-like receptor 4 and activation of the STAT5 transcription factor. Targeting S100A9 with tasquinimod as a single agent and in combination with lenalidomide and with proteasome inhibitors has potent antimyeloma effect that is at least partly independent of the adaptive immune system. This newly identified axis of signaling involving myeloid cells and megakaryocytes may provide a new avenue for therapeutic targeting in multiple myeloma.

Significance

We identified a novel mechanism by which myeloid cells promote myeloma progression independently of the adaptive immune system. Specifically, we discovered a novel role of S100A8/S100A9, the most abundant proteins produced by neutrophils and monocytes, in regulation of myeloma progression via promotion of the megakaryocyte expansion and angiogenesis. Tasquinimod, an inhibitor of S100A9, has potent antimyeloma effects as a single agent and in combination with lenalidomide and with proteasome inhibitors.

Lysophosphatidylcholines modulate immunoregulatory checkpoints in peripheral monocytes and are associated with mortality in people with acute liver failure

BACKGROUND & AIMS

Acute liver failure (ALF) is a life-threatening disease characterised by high-grade inflammation and immunoparesis, which is associated with a high incidence of death from sepsis. Herein, we aimed to describe the metabolic dysregulation in ALF and determine whether systemic immune responses are modulated via the lysophosphatidylcholine (LPC)-autotaxin (ATX)-lysophosphatidylcholinic acid (LPA) pathway.

METHODS

Ninety-six individuals with ALF, 104 with cirrhosis, 31 with sepsis and 71 healthy controls (HCs) were recruited. Pathways of interest were identified by multivariate statistical analysis of proton nuclear magnetic resonance spectroscopy and untargeted ultraperformance liquid chromatography-mass spectrometry-based lipidomics. A targeted metabolomics panel was used for validation. Peripheral blood mononuclear cells were cultured with LPA 16:0, 18:0, 18:1, and their immune checkpoint surface expression was assessed by flow cytometry. Transcript-level expression of the LPA receptor (LPAR) in monocytes was investigated and the effect of LPAR antagonism was also examined in vitro.

RESULTS

LPC 16:0 was highly discriminant between ALF and HC. There was an increase in ATX and LPA in individuals with ALF compared to HCs and those with sepsis. LPCs 16:0, 18:0 and 18:1 were reduced in individuals with ALF and were associated with a poor prognosis. Treatment of monocytes with LPA 16:0 increased their PD-L1 expression and reduced CD155, CD163, MerTK levels, without affecting immune checkpoints on T and NK/CD56+T cells. LPAR1 and 3 antagonism in culture reversed the effect of LPA on monocyte expression of MerTK and CD163. MerTK and CD163, but not LPAR genes, were differentially expressed and upregulated in monocytes from individuals with ALF compared to controls.

CONCLUSION

Reduced LPC levels are biomarkers of poor prognosis in individuals with ALF. The LPC-ATX-LPA axis appears to modulate innate immune response in ALF via LPAR1 and LPAR3. Further investigations are required to identify novel therapeutic agents targeting these receptors.

IMPACT AND IMPLICATIONS

We identified a metabolic signature of acute liver failure (ALF) and investigated the immunometabolic role of the lysophosphatidylcholine-autotaxin-lysophosphatidylcholinic acid pathway, with the aim of finding a mechanistic explanation for monocyte behaviour and identifying possible therapeutic targets (to modulate the systemic immune response in ALF). At present, no selective immune-based therapies exist. We were able to modulate the phenotype of monocytes in vitro and aim to extend these findings to murine models of ALF as a next step. Future therapies may be based on metabolic modulation; thus, the role of specific lipids in this pathway require elucidation and the relative merits of autotaxin inhibition, lysophosphatidylcholinic acid receptor blockade or lipid-based therapies need to be determined. Our findings begin to bridge this knowledge gap and the methods used herein could be useful in identifying therapeutic targets as part of an experimental medicine approach.

Improving head and neck cancer therapies by immunomodulation of the tumour microenvironment

Targeted immunotherapy has improved patient survival in head and neck squamous cell carcinoma (HNSCC), but less than 20% of patients produce a durable response to these treatments. Thus, new immunotherapies that consider all key players of the complex HNSCC tumour microenvironment (TME) are necessary to further enhance tumour-specific T cell responses in patients. HNSCC is an ideal tumour type in which to evaluate immune and non-immune cell differences because of two distinct TME aetiologies (human papillomavirus (HPV)-positive and HPV-negative disease), multiple anatomic sites for tumour growth, and clear distinctions between patients with locally advanced disease and those with recurrent and/or metastatic disease. Recent technological and scientific advancements have provided a more complete picture of all cellular constituents within this complex TME and have evaluated the interplay of both immune and non-immune cells within HNSCC. Here, we include a comprehensive analysis of the complete ecosystem of the HNSCC TME, performed utilizing data-rich resources such as The Cancer Genome Atlas, and cutting-edge techniques, such as single-cell RNA sequencing, high-dimensional flow cytometry and spatial multispectral imaging, to generate improved treatment strategies for this diverse disease.

S100A9 promotes tumor-associated macrophage for M2 macrophage polarization to drive human liver cancer progression: An in vitro study

Tumor-associated macrophages (TAMs) and M2 macrophage polarization have been documented for their implication in various malignancies, but their implication in liver cancer remains to be determined. This study is intended to explore the effect of S100A9 regulated TAMs and macrophage polarization in liver cancer progression. THP-1 cells were induced to differentiate into M1 and M2 macrophages, which were then cultured in liver cancer cell conditioned culture medium before the M1 and M2 macrophages were identified by measuring biomarkers using real-time polymerase chain reaction. The differential expressed genes in macrophages in Gene Expression Omnibus (GEO) databases were screened. S100A9 overexpression and knockdown plasmid were transfected into macrophages to determine the effect of S100A9 on M2 macrophage polarization of TAMs and on proliferation ability of liver cancer cells. The proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) abilities of liver cancer co-cultured with TAMs. M1 and M2 macrophages were successfully induced and liver cancer cell conditioned culture medium can increase polarization of macrophages into M2 macrophages, in which elevated expression of S100A9 was detected. Data in GEO database showed that tumor microenvironment (TME) upregulated S1000A9 expression. Suppression on S1000A9 can significantly suppress M2 macrophage polarization. TAM can provide the necessary microenvironment for liver cancer cells, HepG2 and MHCC97H by increasing cell proliferation, migration, and invasion ability, while suppression on S1000A9 can reverse this expression pattern. Suppression on S100A9 expression can regulate M2 macrophage polarization of TAMs to suppress the progression of liver cancer.

Cabozantinib plus durvalumab in advanced gastroesophageal cancer and other gastrointestinal malignancies: Phase Ib CAMILLA trial results

This is the phase Ib part of the phase I/II CAMILLA trial evaluating cabozantinib plus durvalumab in advanced chemo-refractory proficient mismatch repair or microsatellite stable (pMMR/MSS) gastrointestinal malignancies including gastric/gastroesophageal junction/esophageal (G/GEJ/E) adenocarcinoma, colorectal cancer (CRC), and hepatocellular carcinoma (HCC). Thirty-five patients are enrolled. There are no observed dose-limiting toxicities during dose escalation. The overall grade 3/4 treatment-related adverse event rate is 34%. Among evaluable patients (n = 30), the objective response rate (ORR) is 30%, disease control rate (DCR) 83.3%, 6-month progression-free survival (PFS) 36.7%, median PFS 4.5 months, and median overall survival (OS) 8.7 months. Responses are seen in 4 of 17, 3 of 10, and 2 of 3 patients with CRC, G/GEJ/E adenocarcinoma, and HCC, respectively. Participants with a PD-L1 combined positive score (CPS) ≥5 have numerically higher ORR, PFS, and OS. Cabozantinib plus durvalumab demonstrates a tolerable safety profile and potential efficacy in previously treated advanced pMMR/MSS gastrointestinal malignancies.

Single-cell RNA sequencing reveals the effects of chemotherapy on human pancreatic adenocarcinoma and its tumor microenvironment

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) is a complex ecosystem that drives tumor progression; however, in-depth single cell characterization of the PDAC TME and its role in response to therapy is lacking. Here, we perform single-cell RNA sequencing on freshly collected human PDAC samples either before or after chemotherapy. Overall, we find a heterogeneous mixture of basal and classical cancer cell subtypes, along with distinct cancer-associated fibroblast and macrophage subpopulations. Strikingly, classical and basal-like cancer cells exhibit similar transcriptional responses to chemotherapy and do not demonstrate a shift towards a basal-like transcriptional program among treated samples. We observe decreased ligand-receptor interactions in treated samples, particularly between TIGIT on CD8 + T cells and its receptor on cancer cells, and identify TIGIT as the major inhibitory checkpoint molecule of CD8 + T cells. Our results suggest that chemotherapy profoundly impacts the PDAC TME and may promote resistance to immunotherapy.