On the origin of myeloid-derived suppressor cells

The complexity of immune evasion mechanisms throughout the metastatic cascade

Metastasis, the spread of cancer from a primary site to distant organs, is an important challenge in oncology. This Review explores the complexities of immune escape mechanisms used throughout the metastatic cascade to promote tumor cell dissemination and affect organotropism. Specifically, we focus on adaptive plasticity of disseminated epithelial tumor cells to understand how they undergo phenotypic transitions to survive microenvironmental conditions encountered during metastasis. The interaction of tumor cells and their microenvironment is analyzed, highlighting the local and systemic effects that innate and adaptive immune systems have in shaping an immunosuppressive milieu to foster aggressive metastatic tumors. Effectively managing metastatic disease demands a multipronged approach to target the parallel and sequential mechanisms that suppress anti-tumor immunity. This management necessitates a deep understanding of the complex interplay between tumor cells, their microenvironment and immune responses that we provide with this Review.

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.

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

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.

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

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

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.

MDSC expansion during HIV infection: regulators, ART and immune reconstitution

Myeloid-derived suppressor cells (MDSCs) become expanded in different pathological conditions including human immunodeficiency virus (HIV) infection and this may worsen the disease status and accelerate disease progression. In HIV infection, MDSCs suppress anti-HIV immune responses and hamper immune reconstitution. Understanding the factors and mechanisms of MDSC expansion during HIV infection is central to understanding the pathophysiology of HIV infection. This may pave the way to developing new therapeutic targets or strategies. In this work we addressed (i) the mechanisms that regulate MDSC expansion, (ii) the impact of antiretroviral therapy (ART) on the frequency of MDSCs during HIV infection; (iii) the impact of MDSCs on immune reconstitution during successful ART; and (iv) the potential of MDSCs as a therapeutic target.

The post-septic peripheral myeloid compartment reveals unexpected diversity in myeloid-derived suppressor cells

Introduction

Sepsis engenders distinct host immunologic changes that include the expansion of myeloid-derived suppressor cells (MDSCs). These cells play a physiologic role in tempering acute inflammatory responses but can persist in patients who develop chronic critical illness.

Methods

Cellular Indexing of Transcriptomes and Epitopes by Sequencing and transcriptomic analysis are used to describe MDSC subpopulations based on differential gene expression, RNA velocities, and biologic process clustering.

Results

We identify a unique lineage and differentiation pathway for MDSCs after sepsis and describe a novel MDSC subpopulation. Additionally, we report that the heterogeneous response of the myeloid compartment of blood to sepsis is dependent on clinical outcome.

Discussion

The origins and lineage of these MDSC subpopulations were previously assumed to be discrete and unidirectional; however, these cells exhibit a dynamic phenotype with considerable plasticity.

Myeloid derived suppressor cells in peripheral blood can be a prognostic factor in canine transitional cell carcinoma

Myeloid-derived suppressor cells (MDSCs) are immature cells with immunosuppressive properties found in the tumor microenvironment. MDSCs are divided into two major subsets: polymorphonuclear MDSCs (PMN-MDSCs) and monocytic MDSCs (M-MDSCs). Both MDSC subsets contribute to the creation of an immunosuppressive environment for tumor progression. In humans, patients with high levels of MDSCs show worse outcomes for several types of cancers. However, the association between MDSCs and clinical features has rarely been investigated in canine studies. In the present study, we measured the proportion of PMN-MDSCs and M-MDSCs in the peripheral blood and tumor tissue of dogs with hepatocellular carcinoma (HCC), prostate cancer (PC), transitional cell carcinoma (TCC), lymphoma, and pulmonary adenocarcinoma. Additionally, we examined immunosuppressive ability of PMN-MDSCs and M-MDSCs in peripheral blood mononuclear cells of TCC case on CD4+, CD8+ and interferon-γ+ cells and investigated the relationships of MDSCs with clinical features and outcomes. PMN-MDSCs increased in HCC, PC, TCC, and lymphoma. In contrast, M-MDSCs increased in the TCC. Both PMN-MDSCs and M-MDSCs exhibited immunosuppressive effects on CD8+, CD4+ and interferon-γ+ cells. In dogs with TCC, lymph node metastasis was associated with high level of PMN-MDSCs but not with M-MDSCs. High levels of both PMN-MDSCs and M-MDSCs were related to advanced tumor stage. Kaplan-Meier analysis revealed that high levels of both PMN-MDSCs and M-MDSCs were significantly associated with shorter overall survival. In addition, the Cox proportional hazard regression model showed that M-MDSCs and the tumor stage were independent prognostic factors for TCC. These results suggest that PMN-MDSCs and M-MDSCs may be involved in tumor progression and could be prognostic factors and promising therapeutic targets in dogs with TCC.

Surface CD52, CD84, and PTGER2 mark mature PMN-MDSCs from cancer patients and G-CSF-treated donors

Precise molecular characterization of circulating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is hampered by their mixed composition of mature and immature cells and lack of specific markers. Here, we focus on mature CD66b+CD10+CD16+CD11b+ PMN-MDSCs (mPMN-MDSCs) from either cancer patients or healthy donors receiving G-CSF for stem cell mobilization (GDs). By RNA sequencing (RNA-seq) experiments, we report the identification of a distinct gene signature shared by the different mPMN-MDSC populations under investigation, also validated in mPMN-MDSCs from GDs and tumor-associated neutrophils (TANs) by single-cell RNA-seq (scRNA-seq) experiments. Analysis of such a gene signature uncovers a specific transcriptional program associated with mPMN-MDSC differentiation and allows us to identify that, in patients with either solid or hematologic tumors and in GDs, CD52, CD84, and prostaglandin E receptor 2 (PTGER2) represent potential mPMN-MDSC-associated markers. Altogether, our findings indicate that mature PMN-MDSCs distinctively undergo specific reprogramming during differentiation and lay the groundwork for selective immunomonitoring, and eventually targeting, of mature PMN-MDSCs.

Progress of immune checkpoint inhibitors therapy for non-small cell lung cancer with liver metastases

Nearly one-fifth of patients with non-small cell Lung Cancer (NSCLC) will develop liver metastases (LMs), and the overall treatment strategy of LMs will directly affect the survival of patients. However, some retrospective studies have found that patients receiving chemotherapy or targeted therapy have a poorer prognosis once LMs develop. In recent years, multiple randomised controlled trials (RCTS) have shown significant improvements in outcomes for patients with advanced lung cancer following the introduction of immune checkpoint inhibitors (ICIs) compared to conventional chemotherapy. ICIs is safe and effective in patients with LMs, although patients with LMs are mostly underrepresented in randomised clinical trials. However, NSCLC patients with LMs have a significantly worse prognosis than those without LMs when treated with ICIs, and the mechanism by which LMs induce systemic anti-tumour immunity reduction is unknown, so the management of LMs in patients with NSCLC is a clinical challenge that requires more optimised therapies to achieve effective disease control. In this review, we summarised the mechanism of ICIs in the treatment of LMs, the clinical research and treatment progress of ICIs and their combination with other therapies in patients with LMs from NSCLC.

Phenotypic Analysis of Circulating Myeloid Derived Suppressor Cells and Their Subpopulations in Egyptian Females with Breast Cancer: A Single-Centre Case-Control Study

BACKGROUND

Myeloid-derived suppressor cells (MDSC) are immature myeloid cells with suppressive function that has been thoroughly documented in the setting of cancer. Our purpose was to evaluate levels of MDSC and their subsets in a cohort of Egyptian patients with breast cancer.

METHODS

Evaluation of peripheral blood total MDSC and its subset was done using multicolor flowcytometry in 30 malignant, 10 benign breast tumor patients and 10 healthy control females.

RESULTS

BC patients had higher total MDSC levels compared to controls (p= 0.01) particularly the Monocytic MDSC (M-MDSC) and abnormal MDSC subsets (p = 0.001 and p <0.001, respectively). A tumor size > 2 cm exhibited significantly higher granulocytic MDSCs (G-MDSCs) compared to tumor size < 2 cm (p= 0.02) whereas abnormal MDSCs were significantly higher in patients with a tumor size < 2 cm (p = 0.037).

CONCLUSION

MDSC and its subsets can be used as a prognostic marker of tumor size as well as a potential targets for treatment in breast cancer patients.

The clinical trajectory of peripheral blood immune cell subsets, T-cell activation, and cytokines in septic patients

OBJECTIVE AND DESIGN

Changes in the immune status of patients with sepsis may have a major impact on their prognosis. Our research focused on changes in various immune cell subsets and T-cell activation during the progression of sepsis.

METHODS AND SUBJECTS

We collected data from 188 sepsis patients at the First Affiliated Hospital of Zhejiang University School of Medicine. The main focus was on the patient's immunocyte subset typing, T-cell activation/Treg cell analysis, and cytokine assay, which can indicate the immune status of the patient.

RESULTS

The study found that the number of CD4+ T cells, CD8+ T cells, NK cells, and B cells decreased early in the disease, and the decrease in CD4+ and CD8+ T cells was more pronounced in the death group. T lymphocyte activation was inhibited, and the number of Treg cells increased as the disease progressed. T lymphocyte inhibition was more significant in the death group, and the increase in IL-10 was more significant in the death group. Finally, we used patients' baseline conditions and immunological detection indicators for modeling and found that IL-10, CD4+ Treg cells, CD3+HLA-DR+ T cells, and CD3+CD69+ T cells could predict patients' prognosis well.

CONCLUSION

Our study found that immunosuppression occurs in patients early in sepsis. Early monitoring of the patient's immune status may provide a timely warning of the disease.

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Cancer-associated immune cells and their modulation by melatonin

OBJECTIVES

Rapidly growing evidence suggests that immune cells play a key role in determining tumor progression. Tumor cells are surrounded by a microenvironment composed of different cell populations including immune cells. The cross talk between tumor cells and the neighboring microenvironment is an important factor to take into account while designing tumor therapies. Despite significant advances in immunotherapy strategies, a relatively small proportion of patients have successfully responded to them. Therefore, the search for safe and efficient drugs, which could be used alongside conventional therapies to boost the immune system against tumors, is an ongoing need. In the present work, the modulatory effects of melatonin on different components of tumor immune microenvironment are reviewed.

METHODS

A thorough literature review was performed in PubMed, Scopus, and Web of Science databases. All published papers in English on tumor immune microenvironment and the relevant modulatory effects of melatonin were scrutinized.

RESULTS

Melatonin modulates macrophage polarization and prevents M2 induction. Moreover, it prevents the conversion of fibroblasts into cancer-associated fibroblasts (CAFs) and prevents cancer cell stemness. In addition, it can affect the payload composition of tumor-derived exosomes (TEXs) and their secretion levels to favor a more effective anti-tumor immune response. Melatonin is a safe molecule that affects almost all components of the tumor immune microenvironment and prevents them from being negatively affected by the tumor.

CONCLUSION

Based on the effects of melatonin on normal cells, tumor cells and microenvironment components, it could be an efficient compound to be used in combination with conventional immune-targeted therapies to increase their efficacy.

Assessment of myeloid-derived suppressor cell differentiation ex vivo

Myeloid-derived suppressor cells (MDSCs) are major promoters of progression and metastasis in cancer. MDSCs inhibit the anti-tumor immune response through multiple mechanisms. The main MDSC functions in cancer are related to the inactivation of T cells and the establishment of an immunosuppressive tumor microenvironment (TME) through the production of pro-inflammatory cytokines, among other mechanisms. MDSCs are phenotypically similar to conventional myeloid cells, so their identification is challenging. Moreover, they infiltrate the tumors in limited numbers, and their purification from within the tumors is technically difficult and makes their study a challenge. Therefore, several ex vivo differentiation methods have been established. Our differentiation method leads to MDSCs that closely model tumor-infiltrating counterparts. In this protocol, MDSCs are differentiated from bone marrow precursors by incubation in differentiation medium produced by murine tumor cell lines engineered to constitutively express granulocyte-monocyte colony stimulating factor (GM-CSF). These ex vivo-generated MDSC subsets show high fidelity compared to their natural tumor-infiltrated counterparts. Moreover, the high yields of purification from these ex vivo differentiated MDSC enable their use for validation of new treatments in high-throughput assays. In this chapter we describe the engineering of a stable cell line overexpressing GM-CSF, followed by production and collection of conditioned media supporting MDSC differentiation. Finally, we detail the isolation procedure of bone marrow cells and the specific MDSC differentiation protocol.

Modulation of Myeloid-Derived Suppressor Cells in the Tumor Microenvironment by Natural Products

During carcinogenesis, the microenvironment plays a fundamental role in tumor progression and resistance. This tumor microenvironment (TME) is characterized by being highly immunosuppressive in most cases, which makes it an important target for the development of new therapies. One of the most important groups of cells that orchestrate immunosuppression in TME is myeloid-derived suppressor cells (MDSCs), which have multiple mechanisms to suppress the immune response mediated by T lymphocytes and thus protect the tumor. In this review, we will discuss the importance of modulating MDSCs as a therapeutic target and how the use of natural products, due to their multiple mechanisms of action, can be a key alternative for modulating these cells and thus improve response to therapy in cancer patients.

MDSCs in breast cancer: an important enabler of tumor progression and an emerging therapeutic target

Women worldwide are more likely to develop breast cancer (BC) than any other type of cancer. The treatment of BC depends on the subtype and stage of the cancer, such as surgery, radiotherapy, chemotherapy, and immunotherapy. Although significant progress has been made in recent years, advanced or metastatic BC presents a poor prognosis, due to drug resistance and recurrences. During embryonic development, myeloid-derived suppressor cells (MDSCs) develop that suppress the immune system. By inhibiting anti-immune effects and promoting non-immune mechanisms such as tumor cell stemness, epithelial-mesenchymal transformation (EMT) and angiogenesis, MDSCs effectively promote tumor growth and metastasis. In various BC models, peripheral tissues, and tumor microenvironments (TME), MDSCs have been found to amplification. Clinical progression or poor prognosis are strongly associated with increased MDSCs. In this review, we describe the activation, recruitment, and differentiation of MDSCs production in BC, the involvement of MDSCs in BC progression, and the clinical characteristics of MDSCs as a potential BC therapy target.

Cancer immune exclusion: breaking the barricade for a successful immunotherapy

Immunotherapy has changed the course of cancer treatment. The initial steps were made through tumor-specific antibodies that guided the setup of an antitumor immune response. A new and successful generation of antibodies are designed to target immune checkpoint molecules aimed to reinvigorate the antitumor immune response. The cellular counterpart is the adoptive cell therapy, where specific immune cells are expanded or engineered to target cancer cells. In all cases, the key for achieving positive clinical resolutions rests upon the access of immune cells to the tumor. In this review, we focus on how the tumor microenvironment architecture, including stromal cells, immunosuppressive cells and extracellular matrix, protects tumor cells from an immune attack leading to immunotherapy resistance, and on the available strategies to tackle immune evasion.

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.

CD115- monocytic myeloid-derived suppressor cells are precursors of OLFM4high polymorphonuclear myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) consist of monocytic (M-) MDSCs and polymorphonuclear (PMN-) MDSCs that contribute to an immunosuppressive environment in tumor-bearing hosts. However, research on the phenotypic and functional heterogeneity of MDSCs in tumor-bearing hosts and across different disease stage is limited. Here we subdivide M-MDSCs based on CD115 expression and report that CD115^- M-MDSCs are functionally distinct from CD115⁺ M-MDSCs. CD115^- M-MDSCs increased in bone marrow and blood as tumors progressed. Transcriptome analysis revealed that CD115^- M-MDSCs expressed higher levels of neutrophil-related genes. Moreover, isolated CD115^- M-MDSCs had higher potential to be differentiated into PMN-MDSCs compared with CD115⁺ M-MDSCs. Of note, CD115^- M-MDSCs were able to differentiate into both olfactomedin 4 (OLFM4)^hi and OLFM4^lo PMN-MDSCs, whereas CD115⁺ M-MDSCs differentiated into a smaller proportion of OLFM4^lo PMN-MDSCs. In vivo, M-MDSC to PMN-MDSC differentiation occurred most frequently in bone marrow while M-MDSCs preferentially differentiated into tumor-associated macrophages in the tumor mass. Our study reveals the presence of previously unrecognized subtypes of CD115^- M-MDSCs in tumor-bearing hosts and demonstrates their cellular plasticity during tumorigenesis.

Defining the Emergence of New Immunotherapy Approaches in Breast Cancer: Role of Myeloid-Derived Suppressor Cells

Breast cancer (BC) continues to be the most diagnosed tumor in women and a very heterogeneous disease both inter- and intratumoral, mainly given by the variety of molecular profiles with different biological and clinical characteristics. Despite the advancements in early detection and therapeutic strategies, the survival rate is low in patients who develop metastatic disease. Therefore, it is mandatory to explore new approaches to achieve better responses. In this regard, immunotherapy arose as a promising alternative to conventional treatments due to its ability to modulate the immune system, which may play a dual role in this disease since the relationship between the immune system and BC cells depends on several factors: the tumor histology and size, as well as the involvement of lymph nodes, immune cells, and molecules that are part of the tumor microenvironment. Particularly, myeloid-derived suppressor cell (MDSC) expansion is one of the major immunosuppressive mechanisms used by breast tumors since it has been associated with worse clinical stage, metastatic burden, and poor efficacy of immunotherapies. This review focuses on the new immunotherapies in BC in the last five years. Additionally, the role of MDSC as a therapeutic target in breast cancer will be described.

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.

Phenotypic and functional heterogeneity of monocytes in health and cancer in the era of high dimensional technologies

Monocytes have been traditionally classified in three discrete subsets, which can participate in the immune responses as effector cells or as precursors of myeloid-derived cells in circulation and tissues. However, recent advances in single-cell omics have revealed unprecedented phenotypic and functional heterogeneity that goes well beyond the three conventional monocytic subsets and propose a more fluid differentiation model. This novel concept does not only apply to the monocytes in circulation but also at the tissue site. Consequently, the binary model proposed for differentiating monocyte into M1 and M2 macrophages has been recently challenged by a spectrum model that more realistically mirrors the heterogeneous cues in inflammatory conditions. This review describes the latest results on the high dimensional characterization of monocytes and monocyte-derived myeloid cells in steady state and cancer. We discuss how environmental cues and monocyte-intrinsic properties may affect their differentiation toward specific functional and phenotypic subsets, the causes of monocyte expansion and reduction in cancer, their metabolic requirements, and the potential effect on tumor immunity.

In vitro differentiation of myeloid suppressor cells (MDSC-like) from an immature myelomonocytic precursor THP-1

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population with a potent suppressor profile that regulates immune responses. These cells are one of the main components of the microenvironment of several diseases, including solid and hematologic tumors, autoimmunities, and chronic inflammation. However, their wide use in studies is limited due to they comprehend a rare population, which is difficult to isolate, expand, differentiate, and maintain in culture. Additionally, this population has a complex phenotypic and functional characterization.

OBJECTIVE

To develop a protocol for the in vitro production of MDSC-like population from the differentiation of the immature myeloid cell line THP-1.

METHODS

We stimulated THP-1 with G-CSF (100 ng/mL) and IL-4 (20 ng/mL) for seven days to differentiate into the MDSC-like profile. At the end of the protocol, we characterized these cells phenotypically and functionally by immunophenotyping, gene expression analysis, cytokine release dosage, lymphocyte proliferation, and NK-mediated killing essays.

RESULTS

We differentiate THP-1 cells in an MDSC-like population, named THP1-MDSC-like, which presented immunophenotyping and gene expression profiles compatible with that described in the literature. Furthermore, we verified that this phenotypic and functional differentiation did not deviate to a macrophage profile of M1 or M2. These THP1-MDSC-like cells secreted several immunoregulatory cytokines into the microenvironment, consistent with the suppressor profile related to MDSC. In addition, the supernatant of these cells decreased the proliferation of activated lymphocytes and impaired the apoptosis of leukemic cells induced by NK cells.

CONCLUSIONS

We developed an effective protocol for MDSC in vitro production from the differentiation of the immature myeloid cell line THP-1 induced by G-CSF and IL-4. Furthermore, we demonstrated that THP1-MDSC-like suppressor cells contribute to the immune escape of AML cells. Potentially, these THP1-MDSC-like cells can be applied on a large-scale platform, thus being able to impact the course of several studies and models such as cancer, immunodeficiencies, autoimmunity, and chronic inflammation.

The Anti-Tumorigenic Role of Cannabinoid Receptor 2 in Colon Cancer: A Study in Mice and Humans

The endocannabinoid system, particularly cannabinoid receptor 2 (CB2 in mice and CNR2 in humans), has controversial pathophysiological implications in colon cancer. Here, we investigate the role of CB2 in potentiating the immune response in colon cancer in mice and determine the influence of CNR2 variants in humans. Comparing wild-type (WT) mice to CB2 knockout (CB2^-/-) mice, we performed a spontaneous cancer study in aging mice and subsequently used the AOM/DSS model of colitis-associated colorectal cancer and a model for hereditary colon cancer (Apc^Min/+). Additionally, we analyzed genomic data in a large human population to determine the relationship between CNR2 variants and colon cancer incidence. Aging CB2^-/- mice exhibited a higher incidence of spontaneous precancerous lesions in the colon compared to WT controls. The AOM/DSS-treated CB2^-/- and Apc^Min/+CB2^-/- mice experienced aggravated tumorigenesis and enhanced splenic populations of immunosuppressive myeloid-derived suppressor cells along with abated anti-tumor CD8+ T cells. Importantly, corroborative genomic data reveal a significant association between non-synonymous variants of CNR2 and the incidence of colon cancer in humans. Taken together, the results suggest that endogenous CB2 activation suppresses colon tumorigenesis by shifting the balance towards anti-tumor immune cells in mice and thus portray the prognostic value of CNR2 variants for colon cancer patients.

Myeloid-Derived Suppressor Cells in Cancer and COVID-19 as Associated with Oxidative Stress

Myeloid-derived suppressor cells MDSCs are a heterogeneous population of cells that expand beyond their physiological regulation during pathologies such as cancer, inflammation, bacterial, and viral infections. Their key feature is their remarkable ability to suppress T cell and natural killer NK cell responses. Certain risk factors for severe COVID-19 disease, such as obesity and diabetes, are associated with oxidative stress. The resulting inflammation and oxidative stress can negatively impact the host. Similarly, cancer cells exhibit a sustained increase in intrinsic ROS generation that maintains the oncogenic phenotype and drives tumor progression. By disrupting endoplasmic reticulum calcium channels, intracellular ROS accumulation can disrupt protein folding and ultimately lead to proteostasis failure. In cancer and COVID-19, MDSCs consist of the same two subtypes (PMN-MSDC and M-MDSC). While the main role of polymorphonuclear MDSCs is to dampen the response of T cells and NK killer cells, they also produce reactive oxygen species ROS and reactive nitrogen species RNS. We here review the origin of MDSCs, their expansion mechanisms, and their suppressive functions in the context of cancer and COVID-19 associated with the presence of superoxide anion •O2- and reactive oxygen species ROS.

Role of myeloid-derived suppressor cells during Trypanosoma cruzi infection

Chagas disease (CD), caused by the protozoan parasite Trypanosoma cruzi, is the third largest parasitic disease burden globally. Currently, more than 6 million people are infected, mainly in Latin America, but international migration has turned CD into an emerging health problem in many nonendemic countries. Despite intense research, a vaccine is still not available. A complex parasite life cycle, together with numerous immune system manipulation strategies, may account for the lack of a prophylactic or therapeutic vaccine. There is substantial experimental evidence supporting that T. cruzi acute infection generates a strong immunosuppression state that involves numerous immune populations with regulatory/suppressive capacity. Myeloid-derived suppressor cells (MDSCs), Foxp3+ regulatory T cells (Tregs), regulatory dendritic cells and B regulatory cells are some of the regulatory populations that have been involved in the acute immune response elicited by the parasite. The fact that, during acute infection, MDSCs increase notably in several organs, such as spleen, liver and heart, together with the observation that depletion of those cells can decrease mouse survival to 0%, strongly suggests that MDSCs play a major role during acute T. cruzi infection. Accumulating evidence gained in different settings supports the capacity of MDSCs to interact with cells from both the effector and the regulatory arms of the immune system, shaping the outcome of the response in a very wide range of scenarios that include pathological and physiological processes. In this sense, the aim of the present review is to describe the main knowledge about MDSCs acquired so far, including several crosstalk with other immune populations, which could be useful to gain insight into their role during T. cruzi infection.

JAK/STAT pathway: Extracellular signals, diseases, immunity, and therapeutic regimens

Janus kinase/signal transduction and transcription activation (JAK/STAT) pathways were originally thought to be intracellular signaling pathways that mediate cytokine signals in mammals. Existing studies show that the JAK/STAT pathway regulates the downstream signaling of numerous membrane proteins such as such as G-protein-associated receptors, integrins and so on. Mounting evidence shows that the JAK/STAT pathways play an important role in human disease pathology and pharmacological mechanism. The JAK/STAT pathways are related to aspects of all aspects of the immune system function, such as fighting infection, maintaining immune tolerance, strengthening barrier function, and cancer prevention, which are all important factors involved in immune response. In addition, the JAK/STAT pathways play an important role in extracellular mechanistic signaling and might be an important mediator of mechanistic signals that influence disease progression, immune environment. Therefore, it is important to understand the mechanism of the JAK/STAT pathways, which provides ideas for us to design more drugs targeting diseases based on the JAK/STAT pathway. In this review, we discuss the role of the JAK/STAT pathway in mechanistic signaling, disease progression, immune environment, and therapeutic targets.

The emerging role of regulatory cell-based therapy in autoimmune disease

Autoimmune disease, caused by unwanted immune responses to self-antigens, affects millions of people each year and poses a great social and economic burden to individuals and communities. In the course of autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes mellitus, and multiple sclerosis, disturbances in the balance between the immune response against harmful agents and tolerance towards self-antigens lead to an immune response against self-tissues. In recent years, various regulatory immune cells have been identified. Disruptions in the quality, quantity, and function of these cells have been implicated in autoimmune disease development. Therefore, targeting or engineering these cells is a promising therapeutic for different autoimmune diseases. Regulatory T cells, regulatory B cells, regulatory dendritic cells, myeloid suppressor cells, and some subsets of innate lymphoid cells are arising as important players among this class of cells. Here, we review the roles of each suppressive cell type in the immune system during homeostasis and in the development of autoimmunity. Moreover, we discuss the current and future therapeutic potential of each one of these cell types for autoimmune diseases.

PDX Models: A Versatile Tool for Studying the Role of Myeloid-Derived Suppressor Cells in Breast Cancer

The pivotal role of myeloid-derived suppressive cells (MDSCs) in cancer has become increasingly apparent over the past few years. However, to fully understand how MDSCs can promote human tumor progression and to develop strategies to target this cell type, relevant models that closely resemble the clinical complexity of human tumors are needed. Here, we show that mouse MDSCs of both the monocytic (M-MDCS) and the granulocytic (PMN-MDSC) lineages are recruited to human breast cancer patient-derived xenograft (PDX) tumors in mice. Transcriptomic analysis of FACS-sorted MDSC-subpopulations from the PDX tumors demonstrated the expression of several MDSC genes associated with both their mobilization and immunosuppressive function, including S100A8/9, Ptgs2, Stat3, and Cxcr2, confirming the functional identity of these cells. By combining FACS analysis, RNA sequencing, and immune florescence, we show that the extent and type of MDSC infiltration depend on PDX model intrinsic factors such as the expression of chemokines involved in mobilizing and recruiting tumor-promoting MDSCs. Interestingly, MDSCs have been shown to play a prominent role in breast cancer metastasis, and in this context, we demonstrate increased recruitment of MDSCs in spontaneous PDX lung metastases compared to the corresponding primary PDX tumors. We also demonstrate that T cell-induced inflammation enhances the recruitment of MDSC in experimental breast cancer metastases. In conclusion, breast cancer PDX models represent a versatile tool for studying molecular mechanisms that drive myeloid cell recruitment to primary and metastatic tumors and facilitate the development of innovative therapeutic strategies targeting these cells.

Myeloid-derived suppressor cell: A crucial player in autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) are identified as a highly heterogeneous group of immature cells derived from bone marrow and play critical immunosuppressive functions in autoimmune diseases. Accumulating evidence indicates that the pathophysiology of autoimmune diseases was closely related to genetic mutations and epigenetic modifications, with the latter more common. Epigenetic modifications, which involve DNA methylation, covalent histone modification, and non-coding RNA-mediated regulation, refer to inheritable and potentially reversible changes in DNA and chromatin that regulate gene expression without altering the DNA sequence. Recently, numerous reports have shown that epigenetic modifications in MDSCs play important roles in the differentiation and development of MDSCs and their suppressive functions. The molecular mechanisms of differentiation and development of MDSCs and their regulatory roles in the initiation and progression of autoimmune diseases have been extensively studied, but the exact function of MDSCs remains controversial. Therefore, the biological and epigenetic regulation of MDSCs in autoimmune diseases still needs to be further characterized. This review provides a detailed summary of the current research on the regulatory roles of DNA methylation, histone modifications, and non-coding RNAs in the development and immunosuppressive activity of MDSCs, and further summarizes the distinct role of MDSCs in the pathogenesis of autoimmune diseases, in order to provide help for the diagnosis and treatment of diseases from the perspective of epigenetic regulation of MDSCs.

Peripheral myeloid-derived suppressor cells are good biomarkers of the efficacy of fingolimod in multiple sclerosis

Background

The increasing number of treatments that are now available to manage patients with multiple sclerosis (MS) highlights the need to develop biomarkers that can be used within the framework of individualized medicine. Fingolimod is a disease-modifying treatment that belongs to the sphingosine-1-phosphate receptor modulators. In addition to inhibiting T cell egress from lymph nodes, fingolimod promotes the immunosuppressive activity of myeloid-derived suppressor cells (MDSCs), whose monocytic subset (M-MDSCs) can be used as a biomarker of disease severity, as well as the degree of demyelination and extent of axonal damage in the experimental autoimmune encephalomyelitis (EAE) model of MS. In the present study, we have assessed whether the abundance of circulating M-MDSCs may represent a useful biomarker of fingolimod efficacy in EAE and in the clinical context of MS patients.

Methods

Treatment with vehicle or fingolimod was orally administered to EAE mice for 14 days in an individualized manner, starting the day when each mouse began to develop clinical signs. Peripheral blood from EAE mice was collected previous to treatment and human peripheral blood mononuclear cells (PBMCs) were collected from fingolimod to treat MS patients’ peripheral blood. In both cases, M-MDSCs abundance was analyzed by flow cytometry and its relationship with the future clinical affectation of each individual animal or patient was assessed.

Results

Fingolimod-treated animals presented a milder EAE course with less demyelination and axonal damage, although a few animals did not respond well to treatment and they invariably had fewer M-MDSCs prior to initiating the treatment. Remarkably, M-MDSC abundance was also found to be an important and specific parameter to distinguish EAE mice prone to better fingolimod efficacy. Finally, in a translational effort, M-MDSCs were quantified in MS patients at baseline and correlated with different clinical parameters after 12 months of fingolimod treatment. M-MDSCs at baseline were highly representative of a good therapeutic response to fingolimod, i.e., patients who met at least two of the criteria used to define non-evidence of disease activity-3 (NEDA-3) 12 months after treatment.

Conclusion

Our data indicate that M-MDSCs might be a useful predictive biomarker of the response of MS patients to fingolimod.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02635-3.

Myeloid-derived suppressor cells: Cancer, autoimmune diseases, and more

Although cancer immunotherapy using immune checkpoint inhibitors (ICIs) has been recognized as one of the major treatment modalities for malignant diseases, the clinical outcome is not uniform in all cancer patients. Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells that possess various strong immunosuppressive activities involving multiple immunocompetent cells that are significantly accumulated in patients who did not respond well to cancer immunotherapies. We reviewed the perspective of MDSCs with emerging evidence in this review. Many studies on MDSCs were performed in malignant diseases. Substantial studies on the participation of MDSCs on non-malignant diseases such as chronic infection and autoimmune diseases, and physiological roles in obesity, aging, pregnancy and neonates have yet to be reported. With the growing understanding of the roles of MDSCs, variable therapeutic strategies and agents targeting MDSCs are being investigated, some of which have been used in clinical trials. More studies are required in order to develop more effective strategies against MDSCs.

Suppression of T-Cell Proliferation by Normal Density Granulocytes Led to CD183 Downregulation and Cytokine Inhibition in T-Cells

Normal density granulocytes (NDGs) can suppress T-cell responses in a similar way as myeloid-derived suppressor cells (MDSCs). In this study, we tested the hypothesis that NDGs from healthy donors preferentially inhibit T helper 1 (Th1) cells and investigated the myeloid-derived suppressive effect in different T-cell populations. We found that NDG-induced suppression of T-cell proliferation was contact dependent, mediated by integrin CD11b, and dependent on NDG-production of reactive oxygen species (ROS). The suppression was rapid and occurred within the first few hours of coculture. The suppression did not influence the CD8+/CD4+ ratio indicating an equal sensitivity in these populations. We further analyzed the CD4+ T helper subsets and found that NDGs induced a loss of Th1 surface marker, CD183, that was unrelated to ligand-binding to CD183. In addition, we analyzed the Th1, Th2, and Th17 cytokine production and found that all cytokine groups were suppressed when T-cells were incubated with NDGs. We therefore concluded that NDGs do not preferentially suppress Th1-cells. Instead, NDGs generally suppress Th cells and cytotoxic T-cells but specifically downregulate the Th1 marker CD183.

Cytokine responses to LPS in reprogrammed monocytes are associated with the transcription factor PU.1

Myeloid-derived suppressor cells (MDSCs) are functionally immunosuppressive cells that arise and expand during extensive inflammatory conditions by increased hematopoietic output or reprogramming of immune cells. In sepsis, an increase of circulating MDSCs is associated with adverse outcomes, but unique traits that can be used to identify increased activity of MDSCs are lacking. By using endotoxin tolerance as a model of sepsis-induced monocytic MDSCs (M-MDSC-like cells), this study aims to identify the mediator and transcriptional regulator profile associated with M-MDSC activity. After analyzing 180 inflammation-associated proteins, a profile of differentially expressed cytokines was found in M-MDSC-like cells versus normal monocytes stimulated with LPS. These cytokines were associated with 5 candidate transcription factors, where particularly PU.1 showed differential expression on both transcriptional and protein levels in M-MDSC-like cells. Furthermore, inhibition of PU.1 led to increased production of CXCL5 and CCL8 in M-MDSC-like cells indicating its role in regulating the ability of M-MDSC-like cells to recruit other immune cells. Taken together, the study identifies a unique profile in the pattern of immune mediators defining M-MDSC activity upon LPS stimulation, which offers a functional link to their contribution to immunosuppression.

Myeloid-derived suppressor cells and vaccination against pathogens

It is widely accepted that the immune system includes molecular and cellular components that play a role in regulating and suppressing the effector immune response in almost any process in which the immune system is involved. Myeloid-derived suppressor cells (MDSCs) are described as a heterogeneous population of myeloid origin, immature state, with a strong capacity to suppress T cells and other immune populations. Although the initial characterization of these cells was strongly associated with pathological conditions such as cancer and then with chronic and acute infections, extensive evidence supports that MDSCs are also involved in physiological/non-pathological settings, including pregnancy, neonatal period, aging, and vaccination. Vaccination is one of the greatest public health achievements and has reduced mortality and morbidity caused by many pathogens. The primary goal of prophylactic vaccination is to induce protection against a potential pathogen by mimicking, at least in a part, the events that take place during its natural interaction with the host. This strategy allows the immune system to prepare humoral and cellular effector components to cope with the real infection. This approach has been successful in developing vaccines against many pathogens. However, when the infectious agents can evade and subvert the host immune system, inducing cells with regulatory/suppressive capacity, the development of vaccines may not be straightforward. Notably, there is a long list of complex pathogens that can expand MDSCs, for which a vaccine is still not available. Moreover, vaccination against numerous bacteria, viruses, parasites, and fungi has also been shown to cause MDSC expansion. Increases are not due to a particular adjuvant or immunization route; indeed, numerous adjuvants and immunization routes have been reported to cause an accumulation of this immunosuppressive population. Most of the reports describe that, according to their suppressive nature, MDSCs may limit vaccine efficacy. Taking into account the accumulated evidence supporting the involvement of MDSCs in vaccination, this review aims to compile the studies that highlight the role of MDSCs during the assessment of vaccines against pathogens.

Immune landscape after allo-HSCT: TIGIT- and CD161-expressing CD4 T cells are associated with subsequent leukemia relapse

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the most effective treatment for selected patients with acute myeloid leukemia (AML) and relies on a "graft-versus-leukemia" effect (GVL) where donor T lymphocytes mediate control of malignant cell growth. However, relapse remains the major cause of death after allo-HSCT. In various malignancies, several immunoregulatory mechanisms have been shown to restrain antitumor immunity, including ligand-mediated engagement of inhibitory receptors (IRs) on effector cells, and induction of immunosuppressive cell subsets, such as regulatory T cells (Tregs) or myeloid-derived suppressor cells (MDSCs). Relapse after HSCT remains a major therapeutic challenge, but immunoregulatory mechanisms involved in restraining the GVL effect must be better deciphered in humans. We used mass cytometry to comprehensively characterize circulating leukocytes in 2 cohorts of patients after allo-HSCT. We first longitudinally assessed various immunoregulatory parameters highlighting specific trends, such as opposite dynamics between MDSCs and Tregs. More generally, the immune landscape was stable from months 3 to 6, whereas many variations occurred from months 6 to 12 after HSCT. Comparison with healthy individuals revealed that profound alterations in the immune equilibrium persisted 1 year after HSCT. Importantly, we found that high levels of TIGIT and CD161 expression on CD4 T cells at month 3 after HSCT were distinct features significantly associated with subsequent AML relapse in a second cross-sectional cohort. Altogether, these data provide global insights into the reconstitution of the immunoregulatory landscape after HSCT and highlight non-canonical IRs associated with relapse, which could open the path to new prognostic tools or therapeutic targets to restore subverted anti-AML immunity.

New Perspectives on Myeloid-Derived Suppressor Cells and Their Emerging Role in Haematology

Myeloid-derived suppressor cells (MDSCs) are immature cells of myeloid origin that have gained researchers’ attention, as they constitute promising biomarkers and targets for novel therapeutic strategies (i.e., blockage of development, differentiation, depletion, and deactivation) in several conditions, including neoplastic, autoimmune, infective, and inflammatory diseases, as well as pregnancy, obesity, and graft rejection. They are characterised in humans by the typical immunophenotype of CD11b⁺CD33⁺HLA-DR^–/low and immune-modulating properties leading to decreased T-cell proliferation, induction of T-regulatory cells (T-regs), hindering of natural killer (NK) cell functionality, and macrophage M2-polarisation. The research in the field is challenging, as there are still difficulties in defining cell-surface markers and gating strategies that uniquely identify the different populations of MDSCs, and the currently available functional assays are highly demanding. There is evidence that MDSCs display altered frequency and/or functionality and could be targeted in immune-mediated and malignant haematologic diseases, although there is a large variability of techniques and results between different laboratories. This review presents the current literature concerning MDSCs in a clinical point of view in an attempt to trigger future investigation by serving as a guide to the clinical haematologist in order to apply them in the context of precision medicine as well as the researcher in the field of experimental haematology.

Circulating inflammatory cells in patients with metastatic breast cancer: Implications for treatment

Adaptive and innate immune cells play a crucial role as regulators of cancer development.

Inflammatory cells in blood flow seem to be involved in pro-tumor activities and contribute to breast cancer progression. Circulating lymphocyte ratios such as the platelet-lymphocytes ratio (PLR), the monocyte-lymphocyte ratio (MLR) and the neutrophil-lymphocyte ratio (NLR) are new reproducible, routinely feasible and cheap biomarkers of immune response. These indexes have been correlated to prognosis in many solid tumors and there is growing evidence on their clinical applicability as independent prognostic markers also for breast cancer.

In this review we give an overview of the possible value of lymphocytic indexes in advanced breast cancer prognosis and prediction of outcome. Furthermore, targeting the immune system appear to be a promising therapeutic strategy for breast cancer, especially macrophage-targeted therapies. Herein we present an overview of the ongoing clinical trials testing systemic inflammatory cells as therapeutic targets in breast cancer.

Immunosenescence: A Critical Factor Associated With Organ Injury After Sepsis

Progressive immune dysfunction associated with aging is known as immunosenescence. The age-related deterioration of immune function is accompanied by chronic inflammation and microenvironment changes. Immunosenescence can affect both innate and acquired immunity. Sepsis is a systemic inflammatory response that affects parenchymal organs, such as the respiratory system, cardiovascular system, liver, urinary system, and central nervous system, according to the sequential organ failure assessment (SOFA). The initial immune response is characterized by an excess release of inflammatory factors, followed by persistent immune paralysis. Moreover, immunosenescence was found to complement the severity of the immune disorder following sepsis. Furthermore, the immune characteristics associated with sepsis include lymphocytopenia, thymus degeneration, and immunosuppressive cell proliferation, which are very similar to the characteristics of immunosenescence. Therefore, an in-depth understanding of immunosenescence after sepsis and its subsequent effects on the organs may contribute to the development of promising therapeutic strategies. This paper focuses on the characteristics of immunosenescence after sepsis and rigorously analyzes the possible underlying mechanism of action. Based on several recent studies, we summarized the relationship between immunosenescence and sepsis-related organs. We believe that the association between immunosenescence and parenchymal organs might be able to explain the delayed consequences associated with sepsis.

Meaning and Significance of “Alkalization Therapy for Cancer”

Objectives of the Study

Our research aims to answer the following questions. Can cancer progression be stopped by changing the body condition of person with cancer? Can cancer be cured?If cancer progression can be stopped, what is the underlying mechanism?

Theoretical Rationale for Alkalization Therapy

Almost 70 years ago, Goldblatt H. & Cameron G. reported on the idea of alkalization therapy. Before that, Otto Warburg had been studying the metabolism of cancer and had discovered the essential nature of cancer. He published a review in Science in 1956 under the title “On the origin of cancer cells”. From his phenomena described above, we established the theoretical rationale for alkalization therapy, based on the question of “How does cancer form and what is its nature”?

Limitations of Deductive Methods and Inductive Approaches

In this paper, we describe a method to reconstruct the limitations and weaknesses of modern cancer medicine as Science-based Medicine using an inductive method, and to present a new vision of cancer therapy. How should we treat cancer? (Case presentation): Using a specific clinical case, we present patients in whom were successfully treated with no or few anticancer drugs.

Summary

The biggest weakness of current cancer treatments is that they only treat the cancer and not the actual patient. The “alkalization therapy” that we advocate does not compete with any of the current standard treatments, but improves the effectiveness of standard treatments, reduces side effects, and lowers medical costs.

Myeloid-Derived Suppressor Cells in COVID-19: The Paradox of Good

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the ongoing coronavirus disease 2019 (COVID-19) pandemic. Viral replication in the respiratory tract induces the death of infected cells and the release of pathogen- associated molecular patterns (PAMPs). PAMPs give rise to local inflammation, increasing the secretion of pro- inflammatory cytokines and chemokines, which attract immune cells from the blood into the infected lung. In most individuals, lung-recruited cells clear the infection, and the immune response retreats. However, in some cases, a dysfunctional immune response occurs, which triggers a cytokine storm in the lung, leading to acute respiratory distress syndrome (ARDS). Severe COVID-19 is characterized by an impaired innate and adaptive immune response and by a massive expansion of myeloid-derived suppressor cells (MDSCs). MDSCs function as protective regulators of the immune response, protecting the host from over-immunoreactivity and hyper-inflammation. However, under certain conditions, such as chronic inflammation and cancer, MDSCs could exert a detrimental role. Accordingly, the early expansion of MDSCs in COVID-19 is able to predict the fatal outcome of the infection. Here, we review recent data on MDSCs during COVID-19, discussing how they can influence the course of the disease and whether they could be considered as biomarker and possible targets for new therapeutic approaches.

Intercellular crosstalk of liver sinusoidal endothelial cells in liver fibrosis, cirrhosis and hepatocellular carcinoma

Intercellular crosstalk among various liver cells plays an important role in liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Capillarization of liver sinusoidal endothelial cells (LSECs) precedes fibrosis and accumulating evidence suggests that the crosstalk between LSECs and other liver cells is critical in the development and progression of liver fibrosis. LSECs dysfunction, a key event in the progression from fibrosis to cirrhosis, and subsequently obstruction of hepatic sinuses and increased intrahepatic vascular resistance (IHVR) contribute to development of portal hypertension (PHT) and cirrhosis. More importantly, immunosuppressive tumor microenvironment (TME), which is closely related to the crosstalk between LSECs and immune liver cells like CD8+ T cells, promotes advances tumorigenesis, especially HCC. However, the connections within the crosstalk between LSECs and other liver cells during the progression from liver fibrosis to cirrhosis to HCC have yet to be discussed. In this review, we first summarize the current knowledge of how different crosstalk between LSECs and other liver cells, including hepatocytes, hepatic stellate cells (HSCs), macrophoges, immune cells in liver and extra cellular matrix (ECM) contribute to the physiological function and the progrssion from liver fibrosis to cirrhosis, or even to HCC. Then we examine current treatment strategies for LSECs crosstalk in liver fibrosis, cirrhosis and HCC.

Clinical perspectives on the age-related increase of immunosuppressive activity

The aging process is associated with a remodeling of the immune system involving chronic low-grade inflammation and a gradual decline in the function of the immune system. These processes are also called inflammaging and immunosenescence. The age-related immune remodeling is associated with many clinical changes, e.g., risk for cancers and chronic infections increases, whereas the efficiency of vaccination and immunotherapy declines with aging. On the other hand, there is convincing evidence that chronic inflammatory states promote the premature aging process. The inflammation associated with aging or chronic inflammatory conditions stimulates a counteracting immunosuppression which protects tissues from excessive inflammatory injuries but promotes immunosenescence. Immunosuppression is a driving force in tumors and chronic infections and it also induces the tolerance to vaccination and immunotherapies. Immunosuppressive cells, e.g., myeloid-derived suppressor cells (MDSC), regulatory T cells (Treg), and type M2 macrophages, have a crucial role in tumorigenesis and chronic infections as well as in the tolerance to vaccination and immunotherapies. Interestingly, there is substantial evidence that inflammaging is also associated with an increased immunosuppressive activity, e.g., upregulation of immunosuppressive cells and anti-inflammatory cytokines. Given that both the aging and chronic inflammatory states involve the activation of immunosuppression and immunosenescence, this might explain why aging is a risk factor for tumorigenesis and chronic inflammatory states and conversely, chronic inflammatory insults promote the premature aging process in humans.

Combination of Photothermal Therapy with Anti-Inflammation Therapy Attenuates the Inflammation Tumor Microenvironment and Weakens Immunosuppression for Enhancement Antitumor Treatment

Photothermal therapy has gained widespread attention in cancer treatment, although its efficacy is suppressed due to the inflammatory response and immunosuppression, resulting in a discounted therapeutic effect. In this contribution, a high-performance NIR absorption organic small chromophore is developed, which is encapsulated into Pluronic F-127 to fabricate NIR absorption organic nanoparticles (TTM NPs) with excellent photothermal conversion efficiency (51.49%) for photothermal therapy. TTM NPs based photothermal therapy are combined with Aspisol, a kind of nonsteroidal anti-inflammatory drug, to weaken the inflammation and immunosuppression tumor microenvironment and enhance the antitumor effect. The results prove that the combination therapy realizes effective thermal elimination of primary tumors, inhibition of distant tumors, and suppression of tumor metastasis. The data show that combination therapy can suppress the expression of inflammatory factors, enhance dendritic cell activation and maturation, reverse the immunosuppression, facilitate T cell infiltration, and restore antitumor cytotoxic T lymphocyte activity. This study provides a paradigm to extend the development of photothermal therapy.

Epigenetic and transcriptional regulation of innate immunity in cancer

Innate immune cells participate in the detection of tumor cells via complex signaling pathways mediated by pattern-recognition receptors, such as Toll-like receptors (TLR) and NOD-like receptors (NLR). These pathways are finely tuned via multiple mechanisms, including epigenetic regulation. It is well established that hematopoietic progenitors generate innate immune cells that can regulate cancer cell behavior, and the disruption of normal hematopoiesis in pathologic states may lead to altered immunity and the development of cancer. In this review, we discuss the epigenetic and transcriptional mechanisms that underlie the initiation and amplification of innate immune signaling in cancer. We also discuss new targeting possibilities for cancer control that exploit innate immune cells and signaling molecules, potentially heralding the next generation of immunotherapy.

Immunosuppressive Signaling Pathways as Targeted Cancer Therapies

Immune response has been shown to play an important role in defining patient prognosis and response to cancer treatment. Tumor-induced immunosuppression encouraged the recent development of new chemotherapeutic agents that assists in the augmentation of immune responses. Molecular mechanisms that tumors use to evade immunosurveillance are attributed to their ability to alter antigen processing/presentation pathways and the tumor microenvironment. Cancer cells take advantage of normal molecular and immunoregulatory machinery to survive and thrive. Cancer cells constantly adjust their genetic makeup using several mechanisms such as nucleotide excision repair as well as microsatellite and chromosomal instability, thus giving rise to new variants with reduced immunogenicity and the ability to continue to grow without restrictions. This review will focus on the central molecular signaling pathways involved in immunosuppressive cells and briefly discuss how cancer cells evade immunosurveillance by manipulating antigen processing cells and related proteins. Secondly, the review will discuss how these pathways can be utilized for the implementation of precision medicine and deciphering drug resistance.

Immunosuppressive Signaling Pathways as Targeted Cancer Therapies

Immune response has been shown to play an important role in defining patient prognosis and response to cancer treatment. Tumor-induced immunosuppression encouraged the recent development of new chemotherapeutic agents that assists in the augmentation of immune responses. Molecular mechanisms that tumors use to evade immunosurveillance are attributed to their ability to alter antigen processing/presentation pathways and the tumor microenvironment. Cancer cells take advantage of normal molecular and immunoregulatory machinery to survive and thrive. Cancer cells constantly adjust their genetic makeup using several mechanisms such as nucleotide excision repair as well as microsatellite and chromosomal instability, thus giving rise to new variants with reduced immunogenicity and the ability to continue to grow without restrictions. This review will focus on the central molecular signaling pathways involved in immunosuppressive cells and briefly discuss how cancer cells evade immunosurveillance by manipulating antigen processing cells and related proteins. Secondly, the review will discuss how these pathways can be utilized for the implementation of precision medicine and deciphering drug resistance.

A core of differentially methylated CpG loci in gMDSCs isolated from neonatal and adult sources

BACKGROUND

Myeloid-derived suppressor cells (MDSCs), which include monocytic (mMDSCs) and granulocytic (gMDSCs) cells, are an immunosuppressive, heterogeneous population of cells upregulated in cancer and other pathologic conditions, in addition to normal conditions of stress. The origin of MDSCs is debated, and the regulatory pattern responsible for gMDSC differentiation remains unknown. Since DNA methylation (DNAm) contributes to lineage differentiation, we have investigated whether it contributes to the acquisition of the gMDSC phenotype.

RESULTS

Using the Illumina EPIC array to measure DNAm of gMDSCs and neutrophils from diverse neonatal and adult blood sources, we found 189 differentially methylated CpGs between gMDSCs and neutrophils with a core of ten differentially methylated CpGs that were consistent across both sources of cells. Genes associated with these loci that are involved in immune responses include VCL, FATS, YAP1, KREMEN2, UBTF, MCC-1, and EFCC1. In two cancer patient groups that reflected those used to develop the methylation markers (head and neck squamous cell carcinoma (HNSCC) and glioma), all of the CpG loci were differentially methylated, reaching statistical significance in glioma cases and controls, while one was significantly different in the smaller HNSCC group.

CONCLUSIONS

Our findings indicate that gMDSCs have a core of distinct DNAm alterations, informing future research on gMDSC differentiation and function.