Recommendations for myeloid-derived suppressor cell nomenclature and characterization standards

Immunotherapy resistance in solid tumors: mechanisms and potential solutions

While the emergence of immunotherapies has fundamentally altered the management of solid tumors, cancers exploit many complex biological mechanisms that result in resistance to these agents. These encompass a broad range of cellular activities - from modification of traditional paradigms of immunity via antigen presentation and immunoregulation to metabolic modifications and manipulation of the tumor microenvironment. Intervening on these intricate processes may provide clinical benefit in patients with solid tumors by overcoming resistance to immunotherapies, which is why it has become an area of tremendous research interest with practice-changing implications. This review details the major ways cancers avoid both natural immunity and immunotherapies through primary (innate) and secondary (acquired) mechanisms of resistance, and it considers available and emerging therapeutic approaches to overcoming immunotherapy resistance.

Myeloid‑derived suppressor cells as targets of emerging therapies and nanotherapies (Review)

Breast cancer (BC) is the leading cause of cancer-related mortality among women worldwide. Immunotherapies are a promising approach in cancer treatment, particularly for aggressive forms of BC with high mortality rates. However, the current eligibility for immunotherapy remains limited to a limited fraction of patients with BC. Myeloid-derived suppressor cells (MDSCs), originating from myeloid cells, are known for their dual role in immunosuppression and tumor promotion, significantly affecting patient outcomes by fostering the formation of premetastatic niches. Consequently, targeting MDSCs has emerged as a promising avenue for further exploration in therapeutic interventions. Leveraging nanotechnology-based drug delivery systems, which excel in accumulating drugs within tumors via passive or active targeting mechanisms, are a promising strategy for the use of MDSCs in the treatment of BC. The present review discusses the immunosuppressive functions of MDSCs, their role in BC, and the diverse strategies for targeting them in cancer therapy. Additionally, the present review discusses future advancements in BC treatments focusing on MDSCs. Furthermore, it elucidates the mechanisms underlying MDSC activation, recruitment and differentiation in BC progression, highlighting the clinical characteristics that render MDSCs suitable candidates for the therapy and targeted nanotherapy of BC.

Tumor-derived GLI1 promotes remodeling of the immune tumor microenvironment in melanoma

BACKGROUND

Melanoma progression is based on a close interaction between cancer cells and immune cells in the tumor microenvironment (TME). Thus, a better understanding of the mechanisms controlling TME dynamics and composition will help improve the management of this dismal disease. Work from our and other groups has reported the requirement of an active Hedgehog-GLI (HH-GLI) signaling for melanoma growth and stemness. However, the role of the downstream GLI1 transcription factor in melanoma TME remains largely unexplored.

METHODS

The immune-modulatory activity of GLI1 was evaluated in a syngeneic B16F10 melanoma mouse model assessing immune populations by flow cytometry. Murine polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) were differentiated from bone marrow cells and their immunosuppressive ability was assessed by inhibition of T cells. Conditioned media (CM) from GLI1-overexpressing mouse melanoma cells was used to culture PMN-MDSCs, and the effects of CM were evaluated by Transwell invasion assay and T cell inhibition. Cytokine array analysis, qPCR and chromatin immunoprecipitation were performed to explore the regulation of CX3CL1 expression by GLI1. Human monocyte-derived dendritic cells (moDCs) were cultured in CM from GLI1-silenced patient-derived melanoma cells to assess their activation and recruitment. Blocking antibodies anti-CX3CL1, anti-CCL7 and anti-CXCL8 were used for in vitro functional assays.

RESULTS

Melanoma cell-intrinsic activation of GLI1 promotes changes in the infiltration of immune cells, leading to accumulation of immunosuppressive PMN-MDSCs and regulatory T cells, and to decreased infiltration of dendric cells (DCs), CD8 + and CD4 + T cells in the TME. In addition, we show that ectopic expression of GLI1 in melanoma cells enables PMN-MDSC expansion and recruitment, and increases their ability to inhibit T cells. The chemokine CX3CL1, a direct transcriptional target of GLI1, contributes to PMN-MDSC expansion and recruitment. Finally, silencing of GLI1 in patient-derived melanoma cells promotes the activation of human monocyte-derived dendritic cells (moDCs), increasing cytoskeleton remodeling and invasion ability. This phenotype is partially prevented by blocking the chemokine CCL7, but not CXCL8.

CONCLUSION

Our findings highlight the relevance of tumor-derived GLI1 in promoting an immune-suppressive TME, which allows melanoma cells to evade the immune system, and pave the way for the design of new combination treatments targeting GLI1.

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.

Impact of obesity‑associated myeloid‑derived suppressor cells on cancer risk and progression (Review)

Obesity is a chronic disease caused by the accumulation of excessive adipose tissue. This disorder is characterized by chronic low‑grade inflammation, which promotes the release of proinflammatory mediators, including cytokines, chemokines and leptin. Simultaneously, chronic inflammation can predispose to cancer development, progression and metastasis. Proinflammatory molecules are involved in the recruitment of specific cell populations in the tumor microenvironment. These cell populations include myeloid‑derived suppressor cells (MDSCs), a heterogeneous, immature myeloid population with immunosuppressive abilities. Obesity‑associated MDSCs have been linked with tumor dissemination, progression and poor clinical outcomes. A comprehensive literature review was conducted to assess the impact of obesity‑associated MDSCs on cancer in both preclinical models and oncological patients with obesity. A secondary objective was to examine the key role that leptin, the most important proinflammatory mediator released by adipocytes, plays in MDSC‑driven immunosuppression Finally, an overview is provided of the different therapeutic approaches available to target MDSCs in the context of obesity‑related cancer.

Exportin 1 governs the immunosuppressive functions of myeloid-derived suppressor cells in tumors through ERK1/2 nuclear export

Myeloid-derived suppressor cells (MDSCs) are a main driver of immunosuppression in tumors. Understanding the mechanisms that determine the development and immunosuppressive function of these cells could provide new therapeutic targets to improve antitumor immunity. Here, using preclinical murine models, we discovered that exportin 1 (XPO1) expression is upregulated in tumor MDSCs and that this upregulation is induced by IL-6-induced STAT3 activation during MDSC differentiation. XPO1 blockade transforms MDSCs into T-cell-activating neutrophil-like cells, enhancing the antitumor immune response and restraining tumor growth. Mechanistically, XPO1 inhibition leads to the nuclear entrapment of ERK1/2, resulting in the prevention of ERK1/2 phosphorylation following the IL-6-mediated activation of the MAPK signaling pathway. Similarly, XPO1 blockade in human MDSCs induces the formation of neutrophil-like cells with immunostimulatory functions. Therefore, our findings revealed a critical role for XPO1 in MDSC differentiation and suppressive functions; exploiting these new discoveries revealed new targets for reprogramming immunosuppressive MDSCs to improve cancer therapeutic responses.

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.

Umbilical cord blood derived cell expansion: a potential neuroprotective therapy

Umbilical cord blood (UCB) is a rich source of beneficial stem and progenitor cells with known angiogenic, neuroregenerative and immune-modulatory properties. Preclinical studies have highlighted the benefit of UCB for a broad range of conditions including haematological conditions, metabolic disorders and neurological conditions, however clinical translation of UCB therapies is lacking. One barrier for clinical translation is inadequate cell numbers in some samples meaning that often a therapeutic dose cannot be achieved. This is particularly important when treating adults or when administering repeat doses of cells. To overcome this, UCB cell expansion is being explored to increase cell numbers. The current focus of UCB cell expansion is CD34+ haematopoietic stem cells (HSCs) for which the main application is treatment of haematological conditions. Currently there are 36 registered clinical trials that are examining the efficacy of expanded UCB cells with 31 of these being for haematological malignancies. Early data from these trials suggest that expanded UCB cells are a safe and feasible treatment option and show greater engraftment potential than unexpanded UCB. Outside of the haematology research space, expanded UCB has been trialled as a therapy in only two preclinical studies, one for spinal cord injury and one for hind limb ischemia. Proteomic analysis of expanded UCB cells in these studies showed that the cells were neuroprotective, anti-inflammatory and angiogenic. These findings are also supported by in vitro studies where expanded UCB CD34+ cells showed increased gene expression of neurotrophic and angiogenic factors compared to unexpanded CD34+ cells. Preclinical evidence demonstrates that unexpanded CD34+ cells are a promising therapy for neurological conditions where they have been shown to improve multiple indices of injury in rodent models of stroke, Parkinson's disease and neonatal hypoxic ischemic brain injury. This review will highlight the current application of expanded UCB derived HSCs in transplant medicine, and also explore the potential use of expanded HSCs as a therapy for neurological conditions. It is proposed that expanded UCB derived CD34+ cells are an appropriate cellular therapy for a range of neurological conditions in children and adults.

Tumor-associated macrophages: A sentinel of innate immune system in tumor microenvironment gone haywire

The tumor microenvironment (TME) is a critical determinant in the initiation, progression, and treatment outcomes of various cancers. Comprising of cancer-associated fibroblasts (CAF), immune cells, blood vessels, and signaling molecules, the TME is often likened to the soil supporting the seed (tumor). Among its constituents, tumor-associated macrophages (TAMs) play a pivotal role, exhibiting a dual nature as both promoters and inhibitors of tumor growth. This review explores the intricate relationship between TAMs and the TME, emphasizing their diverse functions, from phagocytosis and tissue repair to modulating immune responses. The plasticity of TAMs is highlighted, showcasing their ability to adopt either protumorigenic or anti-tumorigenic phenotypes based on environmental cues. In the context of cancer, TAMs' pro-tumorigenic activities include promoting angiogenesis, inhibiting immune responses, and fostering metastasis. The manuscript delves into therapeutic strategies targeting TAMs, emphasizing the challenges faced in depleting or inhibiting TAMs due to their multifaceted roles. The focus shifts towards reprogramming TAMs to an anti-tumorigenic M1-like phenotype, exploring interventions such as interferons, immune checkpoint inhibitors, and small molecule modulators. Noteworthy advancements include the use of CSF1R inhibitors, CD40 agonists, and CD47 blockade, demonstrating promising results in preclinical and clinical settings. A significant section is dedicated to Chimeric Antigen Receptor (CAR) technology in macrophages (CAR-M cells). While CAR-T cells have shown success in hematological malignancies, their efficacy in solid tumors has been limited. CAR-M cells, engineered to infiltrate solid tumors, are presented as a potential breakthrough, with a focus on their development, challenges, and promising outcomes. The manuscript concludes with the exploration of third-generation CAR-M technology, offering insight into in-vivo reprogramming and nonviral vector approaches. In conclusion, understanding the complex and dynamic role of TAMs in cancer is crucial for developing effective therapeutic strategies. While early-stage TAM-targeted therapies show promise, further extensive research and larger clinical trials are warranted to optimize their targeting and improve overall cancer treatment outcomes.

Insights into Immune Exhaustion in Chronic Hepatitis B: A Review of Checkpoint Receptor Expression

Hepatitis B, caused by the hepatitis B virus (HBV), often progresses to chronic infection, leading to severe complications, such as cirrhosis, liver failure, and hepatocellular carcinoma. Chronic HBV infection is characterized by a complex interplay between the virus and the host immune system, resulting in immune cell exhaustion, a phenomenon commonly observed in chronic viral infections and cancer. This state of exhaustion involves elevated levels of inhibitory molecules, cells, and cell surface receptors, as opposed to stimulatory counterparts. This review aims to elucidate the expression patterns of various co-inhibitory and co-stimulatory receptors on immune cells isolated from chronic hepatitis B (CHB) patients. By analyzing existing data, the review conducts comparisons between CHB patients and healthy adults, explores the differences between HBV-specific and total T cells in CHB patients, and examines variations between intrahepatic and peripheral immune cells in CHB patients. Understanding the mechanisms underlying immune exhaustion in CHB is crucial for developing novel immunotherapeutic approaches. This detailed analysis sheds light on the immune exhaustion observed in CHB and lays the groundwork for future combined immunotherapy strategies aimed at leveraging checkpoint receptors to restore immune function and improve clinical outcomes.

Myeloid-derived suppressor cells: Implication in myeloid malignancies and immunotherapy

Myeloid malignancies stem from a modified hematopoietic stem cell and predominantly include acute myeloid leukemia, myelodysplastic neoplasms, myeloproliferative malignancies, and chronic myelomonocytic leukemia. Myeloid-derived suppressor cells (MDSCs) exhibit immunoregulatory properties by governing the innate and adaptive immune systems, creating a permissive and supportive environment for neoplasm growth. This review examines the key characteristics of MDSCs in myeloid malignancies, highlighting that an increased MDSC count corresponds to heightened immunosuppressive capabilities, fostering an immune-tolerant neoplasm microenvironment. Also, this review analyzes and describes the potential of combined cancer therapies, focusing on targeting MDSC generation, expansion, and their inherent immunosuppressive activities to enhance the efficacy of current cancer immunotherapies. A comprehensive understanding of the implications of myeloid malignancies may enhance the exploration of immunotherapeutic strategies for their potential application.

The cross-talk between the macro and micro-environment in precursor lesions of pancreatic cancer leads to new and promising circulating biomarkers

Pancreatic cancer (PC) is a clinically challenging tumor to combat due to its advanced stage at diagnosis as well as its resistance to currently available therapies. The absence of early symptoms and known detectable biomarkers renders this disease incredibly difficult to detect/manage. Recent advances in the understanding of PC biology have highlighted the importance of cancer-immune cell interactions, not only in the tumor micro-environment but also in distant systemic sites, like the bone marrow, spleen and circulating immune cells, the so-called macro-environment. The response of the macro-environment is emerging as a determining factor in tumor development by contributing to the formation of an increasingly immunogenic micro-environment promoting tumor homeostasis and progression. We will summarize the key events associated with the feedback loop between the tumor immune micro-environment (TIME) and the tumor immune macroenvironment (TIMaE) in pancreatic precancerous lesions along with how it regulates disease development and progression. In addition, liquid biopsy biomarkers capable of diagnosing PC at an early stage of onset will also be discussed. A clearer understanding of the early crosstalk between micro-environment and macro-environment could contribute to identifying new molecular therapeutic targets and biomarkers, consequently improving early PC diagnosis and treatment.

Circulating Polymorphonuclear Myeloid-Derived Suppressor Cells (PMN-MDSCs) Have a Biological Role in Patients with Primary Myelofibrosis

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by a chronic inflammatory state that plays a relevant role in the disease pathogenesis (as proven by high levels of inflammatory cytokines with prognostic significance and by a persistent oxidative stress) and by extensive neoangiogenesis in bone marrow (BM) and spleen. Myeloid-derived suppressor cells (MDSCs) are immature cells that expand in patients with cancer, sepsis or chronic inflammation, favoring tumor onset and progression mainly through the decrease in immune surveillance and the promotion of neoangiogenesis. In this paper, we evaluated the presence of circulating MDSCs in PMF patients, the plasmatic factors involved in their mobilization/expansion and the correlations with laboratory, genetic and clinical parameters. The data indicated that MDSCs could have a relevant role in PMF as a new pathogenic mechanism contributing to explaining the phenotypic diversity observed during the clinical course of the disease, or a potential new target for personalized treatment.

The causal role between circulating immune cells and diabetic nephropathy: a bidirectional Mendelian randomization with mediating insights

Diabetic nephropathy (DN) is a critical inflammatory condition linked to diabetes, affecting millions worldwide. This study employs Mendelian randomization (MR) to explore the causal relationship between immune cell signatures and DN, analyzing over 731 immune signatures and incorporating data from 1400 metabolites to investigate potential mediators. Despite no statistically significant influence of DN on immunophenotypes after FDR correction, some phenotypes with unadjusted low P-values warranted mention, including CD34 on Hematopoietic Stem Cell (Myeloid cell Panel), CD45 on CD33- HLA DR- (Myeloid cell Panel). Furthermore, three immunophenotypes were identified to have a significant impact on DN risk: CD16-CD56 on HLA DR+ NK (TBNK Panel), CD45 on HLA DR+ T cell (TBNK Panel), and CD33dim HLA DR+ CD11b+ AC (Myeloid cell Panel). Our findings underscore the critical role of immune cells in DN, highlighting potential mediators and offering new insights into its underlying mechanisms.

A dual-targeting approach with anti-IL10R CAR-T cells engineered to release anti-CD33 bispecific antibody in enhancing killing effect on acute myeloid leukemia cells

BACKGROUND

Immunotherapies, including chimeric antigen receptor (CAR) T cells and bispecific antibodies (BsAbs), encounter several challenges in the management of acute myeloid leukemia (AML), including limited persistence of these treatments, antigen loss and resistance of leukemia stem cells (LSCs) to therapy.

METHODS

Here, we proposed a novel dual-targeting approach utilizing engineered anti-IL10R CAR-T cells to secrete bispecific antibodies targeting CD33. This innovative strategy, rooted in our previous research which established a connection between IL-10 and the stemness of AML cells, designed to improve targeting efficiency and eradicate both LSCs and AML blasts.

RESULTS

We first demonstrated the superior efficacy of this synergistic approach in eliminating AML cell lines and primary cells expressing different levels of the target antigens, even in cases of low CD33 or IL10R expression. Furthermore, the IL10R CAR-T cells that secret anti-CD33 bsAbs (CAR.BsAb-T), exhibited an enhanced activation and induction of cytotoxicity not only in IL10R CAR-T cells but also in bystander T cells, thereby more effectively targeting CD33-positive tumor cells. Our in vivo experiments provided additional evidence that CAR.BsAb-T cells could efficiently redirect T cells, reduce tumor burden, and demonstrate no significant toxicity. Additionally, delivering bsAbs locally to the tumor sites through this strategy helps mitigate the pharmacokinetic challenges typically associated with the rapid clearance of prototypical bsAbs.

CONCLUSIONS

Overall, the engineering of a single-vector targeting IL10R CAR, which subsequently secretes CD33-targeted bsAb, addresses the issue of immune escape due to the heterogeneous expression of IL10R and CD33, and represents a promising progress in AML therapy aimed at improving treatment outcomes.

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

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

MERTK Inhibition as a Targeted Novel Cancer Therapy

In this issue honoring the contributions of Greg Lemke, the Earp and Graham lab teams discuss several threads in the discovery, action, signaling, and translational/clinical potential of MERTK, originally called c-mer, a member of the TYRO3, AXL, and MERTK (TAM) family of receptor tyrosine kinases. The 30-year history of the TAM RTK family began slowly as all three members were orphan RTKs without known ligands and/or functions when discovered by three distinct alternate molecular cloning strategies in the pre-genome sequencing era. The pace of understanding their physiologic and pathophysiologic roles has accelerated over the last decade. The activation of ligands bridging externalized phosphatidylserine (PtdSer) has placed these RTKs in a myriad of processes including neurodevelopment, cancer, and autoimmunity. The field is ripe for further advancement and this article hopefully sets the stage for further understanding and therapeutic intervention. Our review will focus on progress made through the collaborations of the Earp and Graham labs over the past 30 years.

Differential tumor immune microenvironment coupled with tumor progression or tumor eradication in HPV-antigen expressing squamous cell carcinoma (SCC) models

Human papilloma virus (HPV) is an etiological factor of head and neck squamous cell carcinoma (HNSCC). To investigate the role of HPV antigen in anti-tumor immunity, we established mouse models by expressing HPV16 E6 and E7 in a SCC tumor cell line. We obtained two HPV antigen-expressing clones (C-225 and C-100) transplantable into C57BL/6 recipients. We found that C-225 elicited complete eradication in C57BL/6 mice (eradicated), whereas C-100 grew progressively (growing). We examined immune tumor microenvironment (TME) using flow cytometry and found that eradicated or growing tumors exhibited differential immune profiles that may influence the outcome of anti-tumor immunity. Surprisingly, the percentage of CD8 and CD4 tumor-infiltrating lymphocytes (TILs) was much higher in growing (C-100) than eradicated (C-225) tumor. However, the TILs upregulated PD-1 and LAG-3 more potently and exhibited impaired effector functions in growing tumor compared to their counterparts in eradicated tumor. C-225 TME is highly enriched with myeloid cells, especially polymorphonuclear (PMN) myeloid-derived suppressor cells (MDSC), whereas the percentage of M-MDSC and tumor-associated macrophages (TAMs) was much higher in C-100 TME, especially M2-TAMs (CD206+). The complete eradication of C-225 depended on CD8 T cells and elicited anti-tumor memory responses upon secondary tumor challenge. We employed DNA sequencing to identify differences in the T cell receptor of peripheral blood lymphocytes pre- and post-secondary tumor challenge. Lastly, C-225 and C-100 tumor lines harbored different somatic mutations. Overall, we uncovered differential immune TME that may underlie the divergent outcomes of anti-tumor immunity by establishing two SCC tumor lines, both of which express HPV16 E6 and E7 antigens. Our experimental models may provide a platform for pinpointing tumor-intrinsic versus host-intrinsic differences in orchestrating an immunosuppressive TME in HNSCCs and for identifying new targets that render tumor cells vulnerable to immune attack.

Neuroimmune cell interactions and chronic infections in oral cancers

Inflammation is a process that is associated with the activation of distal immunosuppressive pathways that have evolved to restore homeostasis and prevent excessive tissue destruction. However, long-term immunosuppression resulting from systemic and local inflammation that may stem from dysbiosis, infections, or aging poses a higher risk for cancers. Cancer incidence and progression dramatically increase with chronic infections including HIV infection. Thus, studies on pro-tumorigenic effects of microbial stimulants from resident microbiota and infections in the context of inflammation are needed and underway. Here, we discuss chronic infections and potential neuro-immune interactions that could establish immunomodulatory programs permissive for tumor growth and progression.

Bexarotene Induce Differentiation of Myeloid-Derived Suppressor Cells through Arg-1 Signalling Pathway

BACKGROUND

Cellular therapy has emerged as a promising strategy to minimize the use of conventional immunosuppressive drugs and ultimately induce long-term graft survival. Myeloid-derived suppressor cells (MDSCs) can be used for immunosuppressive treatment of solid organ transplants.

METHODS

Granular macrophage colony-stimulating factor (GM-CSF) and bexarotene, an X receptor-selective retinoid, were used for in vitro MDSC induction. Cell phenotypes were detected using flow cytometry, while mRNA was detected via real-time PCR. A mouse skin transplantation model was used to verify the inhibitory effects of this treatment.

RESULTS

The combination of GM-CSF and bexarotene-induced MDSC differentiation. MDSCs induce immune tolerance by inhibiting T-cell proliferation, influencing cytokine secretion, and inducing T-cell transformation into Treg cells. Combination treatment significantly up-regulated Arg-1 expression in MDSCs. The Arg-1 inhibitor nor-NOHA neutralized the immunosuppressive activity of MDSCs, suggesting the involvement of Arg-1 in MDSC-mediated immunosuppression. GM-CSF and bexarotene-induced MDSCs prolong graft survival in mouse skin transplants, exhibiting in vivo immunosuppressive effects.

CONCLUSIONS

A new method for inducing MDSCs is presented. The combination of GM-CSF and bexarotene induces MDSCs with remarkable regulatory functions. Adoptive transfer of the induced MDSCs extended allograft survival. These results suggest that MDSCs can potentially be used in future clinical transplants to inhibit rejection, reduce adverse events, and induce operative tolerance.

Dual roles of CD11b+CD33+HLA-DR-/lowCD14- myeloid-derived suppressor cells with a granulocytic morphology following allogeneic hematopoietic stem cell transplantation: from inflammation promoters to immune suppressors within 90 days

Introduction

Granulocytic myeloid-derived suppressor cells (G-MDSCs) show fast recovery following allogeneic hematopoietic stem cell transplantation (allo-HSCT) constituting the major part of peripheral blood in the early phase. Although G-MDSCs mediate immune suppression through multiple mechanisms, they may also promote inflammation under specific conditions.

Methods

G-MDSCs were isolated from 82 patients following allo-HSCT within 90 days after allo-HSCT, and their interactions with autologous CD3+ T-cells were examined. T-cell proliferation was assessed by flow cytometry following CFSE staining, while differentiation and interferon-γ secretion were characterized using chemokine receptor profiling and ELISpot assays, respectively. NK cell cytotoxicity was evaluated through co-culture with K562 cells. An aGVHD xenogeneic model in humanized mice was employed to study the in vivo effects of human leukocytes. Furthermore, transcriptional alterations in G-MDSCs were analyzed via RNA sequencing to investigate functional transitions.

Results

G-MDSCs promoted inflammation in the early-stage, by facilitating cytokine secretion and proliferation of T cells, as well as their differentiation into pro-inflammatory T helper subsets. At day 28, patients with a higher number of G-MDSCs exhibited an increased risk of developing grades II-IV aGvHD. Besides, adoptive transfer of G-MDSCs from patients at day 28 into humanized mice exacerbated aGvHD. However, at day 90, G-MDSCs led to immunosuppression, characterized by upregulated expression of indoleamine 2,3-dioxygenase gene and interleukin-10 secretion, coupled with the inhibition of T cell proliferation. Furthermore, transcriptional analysis of G-MDSCs at day 28 and day 90 revealed that 1445 genes were differentially expressed. These genes were associated with various pathways, revealing the molecular signatures of early post-transplant differentiation in G-MDSCs. In addition, genes linked to the endoplasmic reticulum stress were upregulated in patients without aGvHD. The acquisition of immunosuppressive function by G-MDSCs may depend on the activation of CXCL2 and DERL1 genes.

Conclusion

Our findings revealed the alteration in the immune characteristics of G-MDSCs within the first 90 days post-allo-HSCT. Moreover, the quantity of G-MDSCs at day 28 may serve as a predictive indicator for the development of aGvHD.

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.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Platelet-derived TGF-β1 induces functional reprogramming of myeloid-derived suppressor cells in immune thrombocytopenia

ABSTRACT

Platelet α-granules are rich in transforming growth factor β1 (TGF-β1), which is associated with myeloid-derived suppressor cell (MDSC) biology. Responders to thrombopoietin receptor agonists (TPO-RAs) revealed a parallel increase in the number of both platelets and MDSCs. Here, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient mice to establish an active murine model of immune thrombocytopenia (ITP). Subsequently, we demonstrated that TPO-RAs augmented the inhibitory activities of MDSCs by arresting plasma cells differentiation, reducing Fas ligand expression on cytotoxic T cells, and rebalancing T-cell subsets. Mechanistically, transcriptome analysis confirmed the participation of TGF-β/Smad pathways in TPO-RA-corrected MDSCs, which was offset by Smad2/3 knockdown. In platelet TGF-β1-deficient mice, TPO-RA-induced amplification and enhanced suppressive capacity of MDSCs was waived. Furthermore, our retrospective data revealed that patients with ITP achieving complete platelet response showed superior long-term outcomes compared with those who only reach partial response. In conclusion, we demonstrate that platelet TGF-β1 induces the expansion and functional reprogramming of MDSCs via the TGF-β/Smad pathway. These data indicate that platelet recovery not only serves as an end point of treatment response but also paves the way for immune homeostasis in immune-mediated thrombocytopenia.

Immune System of Dental Pulp in Inflamed and Normal Tissue

Teeth are vulnerable to structural compromise, primarily attributed to carious lesions, in which microorganisms originating from the oral cavity deteriorate the mineralized structures of enamel and dentin, subsequently infiltrating the underlying soft connective tissue, known as the dental pulp. Nonetheless, dental pulp possesses the necessary capabilities to detect and defend against bacteria and their by-products, using a variety of intricate defense mechanisms. The pulp houses specialized cells known as odontoblasts, which encounter harmful substances produced by oral bacteria. These cells identify pathogens at an early stage and commence the immune system response. As bacteria approach the pulp, various cell types within the pulp, such as different immune cells, stem cells, fibroblasts, as well as neuronal and vascular networks, contribute a range of defense mechanisms. Therefore, the immune system is present in the healthy pulp to restrain the initial spread of pathogens, and then in the inflamed pulp, it prepares the conditions for necrosis or regeneration, so inflammatory response mechanisms play a critical role in maintaining tissue homeostasis. This review aims to consolidate the existing literature on the immune system in dental pulp, encompassing current knowledge on this topic that explains the diverse mechanisms of recognition and defense against pathogens exhibited by dental pulp cells, elucidates the mechanisms of innate and adaptive immunity in inflamed pulp, and highlights the difference between inflamed and normal pulp tissue.

Non-Coding RNA in Tumor Cells and Tumor-Associated Myeloid Cells-Function and Therapeutic Potential

The RNA world is wide, and besides mRNA, there is a variety of other RNA types, such as non-coding (nc)RNAs, which harbor various intracellular regulatory functions. This review focuses on small interfering (si)RNA and micro (mi)RNA, which form a complex network regulating mRNA translation and, consequently, gene expression. In fact, these RNAs are critically involved in the function and phenotype of all cells in the human body, including malignant cells. In cancer, the two main targets for therapy are dysregulated cancer cells and dysfunctional immune cells. To exploit the potential of mi- or siRNA therapeutics in cancer therapy, a profound understanding of the regulatory mechanisms of RNAs and following targeted intervention is needed to re-program cancer cells and immune cell functions in vivo. The first part focuses on the function of less well-known RNAs, including siRNA and miRNA, and presents RNA-based technologies. In the second part, the therapeutic potential of these technologies in treating cancer is discussed, with particular attention on manipulating tumor-associated immune cells, especially tumor-associated myeloid cells.

TLR9 promotes monocytic myeloid-derived suppressor cell induction during JEV infection

Myeloid-derived suppressor cells (MDSCs) are a group of heterologous populations of immature bone marrow cells consisting of progenitor cells of macrophages, dendritic cells and granulocytes. Recent studies have revealed that the accumulation of MDSCs in the mouse spleen plays a pivotal role in suppressing the immune response following JEV infection. However, the mechanisms by which JEV induces MDSCs are poorly understood. Here, it was found that JEV infection induces mitochondrial damage and the release of mitochondrial DNA (mtDNA), which further leads to the activation of TLR9. TLR9 deficiency decreases the M-MDSCs population and their suppressive function both in vitro and in vivo. Moreover, the increase of MHCⅡ expression on antigen-presenting cells and CD28 expression on T cells in TLR9-/- mice was positively correlated with M-MDSCs reduction. Accordingly, the survival rate of TLR9-/- mice dramatically increased after JEV infection. These findings reveal the connections of mitochondrial damage and TLR9 activation to the induction of M-MDSCs during JEV infection.

The impact of IL-10 and IL-17 on myeloid-derived suppressor cells in vitro and in vivo in a murine model of asthma

Myeloid-derived suppressor cells (MDSCs) hold promise for clinical applications due to their immunosuppressive properties, particularly in the context of inflammation. In the present study, the number and immunosuppressive activity of MDSCs isolated from naïve Il10-/-, Il17-/-, and WT mice as control, as well as from house dust mite extract (HDM)-induced asthmatic Il10-/- and Il17-/- mice, were investigated. IL-10 deficiency increased the number of polymorphonuclear (PMN)-MDSCs in the lung, spleen, and bone marrow, without concurrent impairment of their suppressive activity in vitro. In the asthma model, the IL-17 knockout was concomitant with a lower number and activity of monocytic (M)-MDSCs and an altered inflammatory reaction with impaired lung function. Additionally, we found a higher baseline inflammation of the Il17-/- mice in the lung, manifested in increased airway resistance. We conclude that the impact of IL-10 and IL-17 deficiency on MDSCs differs in the context of inflammation. Accordingly, the in vitro experiments demonstrated an increased number of PMN-MDSCs across tissues in Il10-/- mice, which indicates that IL-10 might serve a pivotal role in preserving immune homeostasis under physiological circumstances. In the context of HDM-induced airway inflammation, IL-17 was found to be an important player in the suppression of pulmonary inflammation and regulation of M-MDSCs.

A review concerning the breast cancer-related tumour microenvironment

Breast cancer (BC) is currently the most common malignant tumour in women and one of the leading causes of their death around the world. New and increasingly personalised diagnostic and therapeutic tools have been introduced over the last few decades, along with significant advances regarding the study and knowledge related to BC. The tumour microenvironment (TME) refers to the tumour cell-associated cellular and molecular environment which can influence conditions affecting tumour development and progression. The TME is composed of immune cells, stromal cells, extracellular matrix (ECM) and signalling molecules secreted by these different cell types. Ever deeper understanding of TME composition changes during tumour development and progression will enable new and more innovative therapeutic strategies to become developed for targeting tumours during specific stages of its evolution. This review summarises the role of BC-related TME components and their influence on tumour progression and the development of resistance to therapy. In addition, an account on the modifications in BC-related TME components associated with therapy is given, and the completed or ongoing clinical trials related to this topic are presented.

Deep pan-cancer analysis and multi-omics evidence reveal that ALG3 inhibits CD8+ T cell infiltration by suppressing chemokine secretion and is associated with 5-fluorouracil sensitivity

BACKGROUND

α-1,3-mannosyltransferase (ALG3) holds significance as a key member within the mannosyltransferase family. Nevertheless, the exact function of ALG3 in cancer remains ambiguous. Consequently, the current research aimed to examine the function and potential mechanisms of ALG3 in various types of cancer.

METHODS

Deep pan-cancer analyses were conducted to investigate the expression patterns, prognostic value, genetic variations, single-cell omics, immunology, and drug responses associated with ALG3. Subsequently, in vitro experiments were executed to ascertain the biological role of ALG3 in breast cancer. Moreover, the link between ALG3 and CD8+ T cells was verified using immunofluorescence. Lastly, the association between ALG3 and chemokines was assessed using qRT-PCR and ELISA.

RESULTS

Deep pan-cancer analysis demonstrated a heightened expression of ALG3 in the majority of tumors based on multi-omics evidence. ALG3 emerges as a diagnostic and prognostic biomarker across diverse cancer types. In addition, ALG3 participates in regulating the tumor immune microenvironment. Elevated levels of ALG3 were closely linked to the infiltration of bone marrow-derived suppressor cells (MDSC) and CD8+ T cells. According to in vitro experiments, ALG3 promotes proliferation and migration of breast cancer cells. Moreover, ALG3 inhibited CD8+ T cell infiltration by suppressing chemokine secretion. Finally, the inhibition of ALG3 enhanced the responsiveness of breast cancer cells to 5-fluorouracil treatment.

CONCLUSION

ALG3 shows potential as both a prognostic indicator and immune infiltration biomarker across various types of cancer. Inhibition of ALG3 may represent a promising therapeutic strategy for tumor treatment.

Immunosuppressive regulatory cells in cancer immunotherapy: restrain or modulate?

Immunosuppressive regulatory cells (IRCs) play important roles in negatively regulating immune response, and are mainly divided into myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). Large numbers of preclinical and clinical studies have shown that inhibition or reduction of IRCs could effectively elevate antitumor immune responses. However, several studies also reported that excessive inhibition of IRCs function is one of the main reasons causing the side effects of cancer immunotherapy. Therefore, the reasonable regulation of IRCs is crucial for improving the safety and efficiency of cancer immunotherapy. In this review, we summarised the recent research advances in the cancer immunotherapy by regulating the proportion of IRCs, and discussed the roles of IRCs in regulating tumour immune evasion and drug resistance to immunotherapies. Furthermore, we also discussed how to balance the potential opportunities and challenges of using IRCs to improve the safety of cancer immunotherapies.

Smad4 deficiency inhibits lung metastases through enhancing phagocytosis of lung interstitial macrophages

Smad4, a critical mediator of TGF-β signaling, plays a pivotal role in regulating various cellular functions, including immune responses. In this study, we investigated the impact of Smad4 knockout specifically in macrophages on anti-tumor immunity, focusing on lung metastasis of B16 melanoma cells. Using a mouse model with Smad4 knockout in macrophages established via Lyz2-cre mice and Smad4 flox/flox mice, we demonstrated a significant inhibition of B16 metastasis in the lungs. Interestingly, the inhibition of tumor growth was found to be independent of adaptive immunity, as no significant changes were observed in the numbers or activities of T cells, B cells, or NK cells. Instead, Smad4 knockout led to the emergence of an MCHIIlow CD206high subset of lung interstitial macrophages, characterized by enhanced phagocytosis function. Our findings highlight the crucial role of Smad4 in modulating the innate immune response against tumors and provide insights into potential therapeutic strategies targeting lung interstitial macrophages to enhance anti-tumor immunity.

A reactive monocyte subset characterized by low expression of CD91 is expanded during sterile and septic inflammation

OBJECTIVES

This study was undertaken to assess CD91 expression on monocytes and changes in monocyte subset distribution during acute tissue damage and bloodstream infection (BSI).

METHODS

We investigated blood specimens from healthy individuals, trauma and cardiac surgery patients as a model of tissue damage, and patients with BSI, by flow cytometry using a panel of antibodies comprising CD45, HLA-DR, CD14, CD16 and CD91 for the identification of monocyte subsets.

RESULTS

While infrequent in healthy subjects, CD91low/neg monocyte levels were markedly high in BSI, trauma and after cardiac surgery. This monocyte subset expanded up to 15-fold in both patient cohorts, whereas CD14+CD16+ inflammatory monocytes were multiplied by a factor of 5 only. CD14+CD91low monocytes displayed a significantly lower density of HLA-DR and markedly reduced expression of CD300e, compared to the other subsets. They also expressed high levels of myeloperoxidase and showed robust phagocytic and oxidative burst activity.

CONCLUSIONS

Expansion of CD91low monocytes is a sensitive marker of acute inflammatory states of infectious and non-infectious etiology.

Extracellular vesicles as modulators of monocyte and macrophage function in tumors

The tumor microenvironment (TME) harbors several cell types, such as tumor cells, immune cells, and non-immune cells. These cells communicate through several mechanisms, such as cell-cell contact, cytokines, chemokines, and extracellular vesicles (EVs). Tumor-derived vesicles are known to have the ability to modulate the immune response. Monocytes are a subset of circulating innate immune cells and play a crucial role in immune surveillance, being recruited to tissues where they differentiate into macrophages. In the context of tumors, it has been observed that tumor cells can attract monocytes to the TME and induce their differentiation into tumor-associated macrophages with a pro-tumor phenotype. Tumor-derived EVs have emerged as essential structures mediating this process. Through the transfer of specific molecules and signaling factors, tumor-derived EVs can shape the phenotype and function of monocytes, inducing the expression of cytokines and molecules by these cells, thus modulating the TME towards an immunosuppressive environment.

JAK inhibition enhances checkpoint blockade immunotherapy in patients with Hodgkin lymphoma

Unleashing antitumor T cell activity by checkpoint inhibitor immunotherapy is effective in cancer patients, but clinical responses are limited. Cytokine signaling through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway correlates with checkpoint immunotherapy resistance. We report a phase I clinical trial of the JAK inhibitor ruxolitinib with anti-PD-1 antibody nivolumab in Hodgkin lymphoma patients relapsed or refractory following checkpoint inhibitor immunotherapy. The combination yielded a best overall response rate of 53% (10/19). Ruxolitinib significantly reduced neutrophil-to-lymphocyte ratios and percentages of myeloid suppressor cells but increased numbers of cytokine-producing T cells. Ruxolitinib rescued the function of exhausted T cells and enhanced the efficacy of immune checkpoint blockade in preclinical solid tumor and lymphoma models. This synergy was characterized by a switch from suppressive to immunostimulatory myeloid cells, which enhanced T cell division.

Intra-tumoral administration of CHST15 siRNA remodels tumor microenvironment and augments tumor-infiltrating T cells in pancreatic cancer

The dense stroma is one cause of poor efficacy of T cell-mediated immunotherapy in pancreatic ductal adenocarcinoma (PDAC). Carbohydrate sulfotransferase 15 (CHST15) is a proteoglycan-synthetic enzyme responsible for remodeling tumor stroma. Intra-tumoral injection of CHST15 small interfering RNA (siRNA) has been shown to increase the tumor-infiltrating T cells (TILs) in patients with unresectable PDAC. However, the mechanism underlying the enhanced accumulation of TILs is not fully explored. Here, we demonstrate that intra-tumoral injection of CHST15 siRNA locally and remotely diminishes myeloid-derived suppressor cells (MDSCs) and enhances TILs in mice. CHST15 was expressed by tumor cells and MDSCs in both tumor and tumor-draining lymph nodes (TDLNs), and CHST15 siRNA repressed stromal density, neutrophil extracellular traps, and Ly6C/G+ MDSCs in vivo. Remarkably, tumor growth inhibition was only observed in the immunocompetent KPC model, which is associated with enhanced TILs. In vitro, CHST15 siRNA significantly downregulated the levels of CHST15 and indoleamine 2,3-dioxygenase mRNA in CD33+ MDSCs derived from human peripheral blood mononuclear cells. These results suggest a dual role for intra-tumorally injected CHST15 siRNA on modulating the tumor immune microenvironment for T cell entry and remotely diminishing CHST15+ MDSCs, decreasing T cell suppression and expanding T cells in the TDLN, ultimately leading to an enhanced accumulation of TILs.

A Non-Coding Oligonucleotide Recruits Cutaneous CD11b+ Cells that Inhibit Thelper Responses and Promote Tregs

Skin-resident antigen-presenting cells (APC) play an important role in maintaining peripheral tolerance via immune checkpoint proteins and induction of T regulatory cells (Tregs). However, there is a lack of knowledge on how to expand or recruit immunoregulatory cutaneous cells without causing inflammation. Here, it is shown that administration of a non-coding single-stranded oligonucleotide (ssON) leads to CCR2-dependent accumulation of CD45+CD11b+Ly6C+ cells in the skin that express substantial levels of PD-L1 and ILT3. Transcriptomic analyses of skin biopsies reveal the upregulation of key immunosuppressive genes after ssON administration. Functionally, the cutaneous CD11b+ cells inhibit Th1/2/9 responses and promote the induction of CD4+FoxP3+ T-cells. In addition, ssON treatment of imiquimod-induced inflammation results in significantly reduced Th17 responses. It is also shown that induction of IL-10 production in the presence of cutaneous CD11b+ cells isolated after ssON administrations is partly PD-L1 dependent. Altogether, an immunomodulatory ssON is identified that can be used therapeutically to recruit cutaneous CD11b+ cells with the capacity to dampen Th cells.

Generation of Myeloid-Derived Suppressor Cells Mediated by MicroRNA-125a-5p in Melanoma

The ability of tumor-derived extracellular vesicles (EVs) to modulate the function of myeloid cells is widely recognized. Hence, a comprehensive understanding of the distinct components associated with EVs and the signals that they deliver to myeloid cells could provide potential approaches to impede the immunosuppression by myeloid-derived suppressor cells (MDSCs). We investigated melanoma EV-associated microRNAs (miRs) using the RET transgenic melanoma mouse model and simulated their transfer to normal myeloid cells by transfecting immature mouse myeloid cells and human monocytes. We observed elevated levels of miR-125a-5p, -125b-5p, and let-7e-5p in mouse melanoma-infiltrating MDSCs. In addition, miR-125a-5p levels in the tumor microenvironment correlated with mouse melanoma progression. The delivery of miR-125a-5p, alone or in combination with let-7e-5p and miR-99b-5p from the same genomic cluster, to normal myeloid cells resulted in their conversion to MDSC-like cells. Our findings indicate that miR-125a-5p could modulate myeloid cell activation in the melanoma microenvironment via a NF-κB-dependent mechanism.

Comparative study of immune response to local tumor destruction modalities in a murine breast cancer model

Introduction

Immunotherapy is revolutionizing the management of multiple cancer types. However, only a subset of patients responds to immunotherapy. One mechanism of resistance is the absence of immune infiltrates within the tumor. In situ vaccine with local means of tumor destruction that can induce immunogenic cell death have been shown to enhance tumor T cell infiltration and increase efficacy of immune checkpoint blockade.

Methods

Here, we compare three different forms of localize tumor destruction therapies: radiation therapy (RT), vascular targeted photodynamic therapy (VTP) and cryoablation (Cryo), which are known to induce immunogenic cell death, with their ability to induce local and systemic immune responses in a mouse 4T1 breast cancer model. The effects of combining RT, VTP, Cryo with anti-PD1 was also assessed.

Results

We observed that RT, VTP and Cryo significantly delayed tumor growth and extended overall survival. In addition, they also induced regression of non-treated distant tumors in a bilateral model suggesting a systemic immune response. Flow cytometry showed that VTP and Cryo are associated with a reduction in CD11b+ myeloid cells (granulocytes, monocytes, and macrophages) in tumor and periphery. An increase in CD8+ T cell infiltration into tumors was observed only in the RT group. VTP and Cryo were associated with an increase in CD4+ and CD8+ cells in the periphery.

Conclusion

These data suggest that cell death induced by VTP and Cryo elicit similar immune responses that differ from local RT.

Tumour Microenvironment: The General Principles of Pathogenesis and Implications in Diffuse Large B Cell Lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma worldwide, constituting around 30-40% of all cases. Almost 60% of patients develop relapse of refractory DLBCL. Among the reasons for the therapy failure, tumour microenvironment (TME) components could be involved, including tumour-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), tumour-associated neutrophils (TANs), cancer-associated fibroblasts (CAFs), and different subtypes of cytotoxic CD8+ cells and T regulatory cells, which show complex interactions with tumour cells. Understanding of the TME can provide new therapeutic options for patients with DLBCL and improve their prognosis and overall survival. This review provides essentials of the latest understanding of tumour microenvironment elements and discusses their role in tumour progression and immune suppression mechanisms which result in poor prognosis for patients with DLBCL. In addition, we point out important markers for the diagnostic purposes and highlight novel therapeutic targets.

Engineered CD147-Deficient THP-1 Impairs Monocytic Myeloid-Derived Suppressor Cell Differentiation but Maintains Antibody-Dependent Cellular Phagocytosis Function for Jurkat T-ALL Cells with Humanized Anti-CD147 Antibody

CD147 is upregulated in cancers, including aggressive T-ALL. Traditional treatments for T-ALL often entail severe side effects and the risk of relapse, highlighting the need for more efficacious therapies. ADCP contributes to the antitumor response by enhancing the ability of phagocytic cells to engulf cancer cells upon antibody binding. We aimed to engineer CD147KO THP-1 cells and evaluated their differentiation properties compared to the wild type. A humanized anti-CD147 antibody, HuM6-1B9, was also constructed for investing the phagocytic function of CD147KO THP-1 cells mediated by HuM6-1B9 in the phagocytosis of Jurkat T cells. The CD147KO THP-1 was generated by CRISPR/Cas9 and maintained polarization profiles. HuM6-1B9 was produced in CHO-K1 cells and effectively bound to CD147 with high binding affinity (KD: 2.05 ± 0.30 × 10-9 M). Additionally, HuM6-1B9 enhanced the phagocytosis of Jurkat T cells by CD147KO THP-1-derived LPS-activated macrophages (M-LPS), without self-ADCP. The formation of THP-1-derived mMDSC was limited in CD147KO THP-1 cells, highlighting the significant impact of CD147 deletion. Maintaining expression markers and phagocytic function in CD147KO THP-1 macrophages supports future engineering and the application of induced pluripotent stem cell-derived macrophages. The combination of HuM6-1B9 and CD147KO monocyte-derived macrophages holds promise as an alternative strategy for T-ALL.

Guardians and Mediators of Metastasis: Exploring T Lymphocytes, Myeloid-Derived Suppressor Cells, and Tumor-Associated Macrophages in the Breast Cancer Microenvironment

Breast cancers (BCs) are solid tumors composed of heterogeneous tissues consisting of cancer cells and an ever-changing tumor microenvironment (TME). The TME includes, among other non-cancer cell types, immune cells influencing the immune context of cancer tissues. In particular, the cross talk of immune cells and their interactions with cancer cells dramatically influence BC dissemination, immunoediting, and the outcomes of cancer therapies. Tumor-infiltrating lymphocytes (TILs), tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs) represent prominent immune cell populations of breast TMEs, and they have important roles in cancer immunoescape and dissemination. Therefore, in this article we review the features of TILs, TAMs, and MDSCs in BCs. Moreover, we highlight the mechanisms by which these immune cells remodel the immune TME and lead to breast cancer metastasis.

Defining mesenchymal stem/stromal cell-induced myeloid-derived suppressor cells using single-cell transcriptomics

Mesenchymal stem/stromal cells (MSCs) modulate the immune response through interactions with innate immune cells. We previously demonstrated that MSCs alleviate ocular autoimmune inflammation by directing bone marrow cell differentiation from pro-inflammatory CD11bhiLy6ChiLy6Glo cells into immunosuppressive CD11bmidLy6CmidLy6Glo cells. Herein, we analyzed MSC-induced CD11bmidLy6Cmid cells using single-cell RNA sequencing and compared them with CD11bhiLy6Chi cells. Our investigation revealed seven distinct immune cell types including myeloid-derived suppressor cells (MDSCs) in the CD11bmidLy6Cmid cells, while CD11bhiLy6Chi cells included mostly monocytes/macrophages with a small cluster of neutrophils. These MSC-induced MDSCs highly expressed Retnlg, Cxcl3, Cxcl2, Mmp8, Cd14, and Csf1r as well as Arg1. Comparative analyses of CSF-1RhiCD11bmidLy6Cmid and CSF-1RloCD11bmidLy6Cmid cells demonstrated that the former had a homogeneous monocyte morphology and produced elevated levels of interleukin-10. Functionally, these CSF-1RhiCD11bmidLy6Cmid cells, compared with the CSF-1RloCD11bmidLy6Cmid cells, inhibited CD4+ T cell proliferation and promoted CD4+CD25+Foxp3+ Treg expansion in culture and in a mouse model of experimental autoimmune uveoretinitis. Resistin-like molecule (RELM)-γ encoded by Retnlg, one of the highly upregulated genes in MSC-induced MDSCs, had no direct effects on T cell proliferation, Treg expansion, or splenocyte activation. Together, our study revealed a distinct transcriptional profile of MSC-induced MDSCs and identified CSF-1R as a key cell-surface marker for detection and therapeutic enrichment of MDSCs.

Exploring the Potential of Glycolytic Modulation in Myeloid-Derived Suppressor Cells for Immunotherapy and Disease Management

Recent advancements in various technologies have shed light on the critical role of metabolism in immune cells, paving the way for innovative disease treatment strategies through immunometabolism modulation. This review emphasizes the glucose metabolism of myeloid-derived suppressor cells (MDSCs), an emerging pivotal immunosuppressive factor especially within the tumor microenvironment. MDSCs, an immature and heterogeneous myeloid cell population, act as a double-edged sword by exacerbating tumors or mitigating inflammatory diseases through their immune-suppressive functions. Numerous recent studies have centered on glycolysis of MDSC, investigating the regulation of altered glycolytic pathways to manage diseases. However, the specific changes in MDSC glycolysis and their exact functions continue to be areas of ongoing discussion yet. In this paper, we review a range of current findings, including the latest research on the alteration of glycolysis in MDSCs, the consequential functional alterations in these cells, and the outcomes of attempts to modulate MDSC functions by regulating glycolysis. Ultimately, we will provide insights into whether these research efforts could be translated into clinical applications.

Syngeneic murine models with distinct immune microenvironments represent subsets of human intrahepatic cholangiocarcinoma

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) is a poorly immunogenic malignancy associated with limited survival. Syngeneic immunocompetent mouse models of CCA are an essential tool to elucidate the tumor immune microenvironment (TIME), understand mechanisms of tumor immune evasion, and test novel immunotherapeutic strategies. The scope of this study was to develop and characterize immunocompetent CCA models with distinct genetic drivers, and correlate tumor genomics, immunobiology, and therapeutic response.

METHODS

A multifaceted approach including scRNA-seq, CITE-seq, whole exome and bulk RNA sequencing was employed. FDA-approved PD-1/PD-L1 antibodies were tested in humanized PD-1/PD-L1 mice (HuPD-H1).

RESULTS

A genetic mouse model of intrahepatic CCA (iCCA) driven by intrabiliary transduction of Fbxw7ΔF/Akt that mimics human iCCA was generated. From the Fbxw7ΔF/Akt tumors, a murine cell line (FAC) and syngeneic model with genetic and phenotypic characteristics of human iCCA were developed. Established SB1 (YAPS127A/Akt) and KPPC (KrasG12Dp53L/L) models were compared to the FAC model. Although the models had transcriptomic similarities, they had substantial differences as well. Mutation patterns of FAC, SB1, and KPPC cells matched different mutational signatures in Western and Japanese CCA patient cohorts. KPPC tumors had a high tumor mutation burden. FAC tumors had a T cell-infiltrated TIME, while SB1 tumors had a preponderance of suppressive myeloid cells. FAC, SB1, and KPPC tumors matched different immune signatures in human iCCA cohorts. Moreover, FAC, SB1, and KPPC tumor-bearing HuPD-H1 mice displayed differential responses to nivolumab or durvalumab.

CONCLUSIONS

Syngeneic iCCA models display a correlation between tumor genotype and TIME phenotype, with differential responses to FDA-approved immunotherapies. This study underscores the importance of leveraging multiple preclinical models to understand responses to immunotherapy in different genetic subsets of human CCA.

IMPACT AND IMPLICATIONS

Understanding the relationship between tumor genotype and the phenotype of the immune microenvironment is an unmet need in cholangiocarcinoma (CCA). Herein, we use syngeneic murine models of intrahepatic CCA with different genetic drivers to demonstrate a correlation between tumor genotype and immune microenvironment phenotype in murine models, which is associated with differential responses to FDA-approved immunotherapies. This information will help guide other preclinical studies. Additionally, it emphasizes that immune checkpoint inhibition in patients with CCA is not a "one-size-fits-all" approach. Our observations suggest that, as for targeted therapies, patients should be stratified and selected for treatment according to their tumor genetics.

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone

BACKGROUND

Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression.

METHODS

Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis.

FINDINGS

ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone.

INTERPRETATION

Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer.

FUNDING

Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Converting "cold" to "hot": epigenetics strategies to improve immune therapy effect by regulating tumor-associated immune suppressive cells

Significant developments in cancer treatment have been made since the advent of immune therapies. However, there are still some patients with malignant tumors who do not benefit from immunotherapy. Tumors without immunogenicity are called "cold" tumors which are unresponsive to immunotherapy, and the opposite are "hot" tumors. Immune suppressive cells (ISCs) refer to cells which can inhibit the immune response such as tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) cells and so on. The more ISCs infiltrated, the weaker the immunogenicity of the tumor, showing the characteristics of "cold" tumor. The dysfunction of ISCs in the tumor microenvironment (TME) may play essential roles in insensitive therapeutic reaction. Previous studies have found that epigenetic mechanisms play an important role in the regulation of ISCs. Regulating ISCs may be a new approach to transforming "cold" tumors into "hot" tumors. Here, we focused on the function of ISCs in the TME and discussed how epigenetics is involved in regulating ISCs. In addition, we summarized the mechanisms by which the epigenetic drugs convert immunotherapy-insensitive tumors into immunotherapy-sensitive tumors which would be an innovative tendency for future immunotherapy in "cold" tumor.