Cyclophosphamide Enhances Cancer Antibody Immunotherapy in the Resistant Bone Marrow Niche by Modulating Macrophage FcγR Expression

Maplirpacept: a CD47 decoy receptor with minimal red blood cell binding and robust anti-tumor efficacy

Introduction

CD47 is highly expressed on cancer cells and triggers an anti-phagocytic "don't eat me" signal when bound by the inhibitory signal regulatory protein α (SIRPα) expressed on macrophages. While CD47 blockade can mitigate tumor growth, many CD47 blockers also bind to red blood cells (RBCs), leading to anemia. Maplirpacept (TTI-622, PF-07901801) is a CD47 blocking fusion protein consisting of a human SIRPα fused to an IgG4 Fc region and designed to limit binding to RBCs.

Methods

To determine maplirpacept binding to RBCs and interference with blood tests, human blood samples were used. The ability of maplirpacept to promote macrophage-mediated phagocytosis of human tumor cells was assessed using both confocal microscopy and flow cytometry. In vivo antitumor efficacy as a monotherapy and in combination with other therapeutic agents was evaluated in xenograft models.

Results

In the current study, we demonstrate that maplirpacept has limited binding to RBCs while driving enhanced macrophage-mediated phagocytosis of hematological tumor cells in vitro and reducing tumor burden in human xenograft models. Moreover, phagocytosis of neoplastic cells can be enhanced when maplirpacept is combined with other therapeutic agents, including antibodies or chemotherapeutic agents.

Conclusion

These preclinical results establish maplirpacept as an effective CD47 blocker that mitigates the potential for anemia in patients.

FcγRIIB (CD32B) antibodies enhance immune responses through activating FcγRs

Fc receptors (FcR) play a key role in coordinating responses from both the innate and adaptive immune system. The inhibitory Fc gamma receptor (FcγRIIB/CD32B; referred to as FcγRII/CD32 in mice) restrains the immune response, specifically through regulating immunoglobulin G (IgG) effector functions. FcγRII-deficient mice demonstrate elevated incidence and severity of autoimmunity and increased responses to immunization and infections. To explore the potential of FcγRIIB as a target for augmenting vaccines, we tested the ability of monoclonal antibodies (mAb) against mouse FcγRII and human FcγRIIB to enhance humoral responses in preclinical models. We used wild-type (WT), FcγR-deficient, and human FcγRIIB transgenic (Tg) mice with either a functional intracellular domain (hFcγRIIB Tg) or lacking immunoreceptor tyrosine-based inhibitory motif (ITIM) signalling capacity (NoTIM). Targeting mouse FcγRII and human FcγRIIB with antibodies significantly augmented humoral immune responses against experimental antigens and enhanced tumour clearance in vivo. Surprisingly, mAbs without a functional Fc (N297Q; referred to as Fc-null) lacked efficacy. Similarly, blocking FcγRII in mice lacking activating FcγRs failed to enhance immune responses. Conversely, blocking both signalling-competent and signalling-defective (NoTIM) FcγRIIB in Tg mice with a WT, but not Fc-null, FcγRIIB mAb equally enhanced immunity. These data indicate the redundancy of inhibitory signalling in potentiating immune responses in vivo. Collectively, our data suggest that mAb-targeting of FcγRIIB stabilizes mAb Fc and enhances immune responses via Fc-mediated crosslinking of activating FcγRs, irrespective of the inhibitory function of FcγRIIB. These findings support a strategy to boost immune responses in immunization protocols.

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

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

Macrophages in tumor cell migration and metastasis

Tumor-associated macrophages (TAMs) are a phenotypically diverse, highly plastic population of cells in the tumor microenvironment (TME) that have long been known to promote cancer progression. In this review, we summarize TAM ontogeny and polarization, and then explore how TAMs enhance tumor cell migration through the TME, thus facilitating metastasis. We also discuss how chemotherapy and host factors including diet, obesity, and race, impact TAM phenotype and cancer progression. In brief, TAMs induce epithelial-mesenchymal transition (EMT) in tumor cells, giving them a migratory phenotype. They promote extracellular matrix (ECM) remodeling, allowing tumor cells to migrate more easily. TAMs also provide chemotactic signals that promote tumor cell directional migration towards blood vessels, and then participate in the signaling cascade at the blood vessel that allows tumor cells to intravasate and disseminate throughout the body. Furthermore, while chemotherapy can repolarize TAMs to induce an anti-tumor response, these cytotoxic drugs can also lead to macrophage-mediated tumor relapse and metastasis. Patient response to chemotherapy may be dependent on patient-specific factors such as diet, obesity, and race, as these factors have been shown to alter macrophage phenotype and affect cancer-related outcomes. More research on how chemotherapy and patient-specific factors impact TAMs and cancer progression is needed to refine treatment strategies for cancer patients.

Fc gamma receptors: Their evolution, genomic architecture, genetic variation, and impact on human disease

Fc gamma receptors (FcγRs) are a family of receptors that bind IgG antibodies and interface at the junction of humoral and innate immunity. Precise regulation of receptor expression provides the necessary balance to achieve healthy immune homeostasis by establishing an appropriate immune threshold to limit autoimmunity but respond effectively to infection. The underlying genetics of the FCGR gene family are central to achieving this immune threshold by regulating affinity for IgG, signaling efficacy, and receptor expression. The FCGR gene locus was duplicated during evolution, retaining very high homology and resulting in a genomic region that is technically difficult to study. Here, we review the recent evolution of the gene family in mammals, its complexity and variation through copy number variation and single-nucleotide polymorphism, and impact of these on disease incidence, resolution, and therapeutic antibody efficacy. We also discuss the progress and limitations of current approaches to study the region and emphasize how new genomics technologies will likely resolve much of the current confusion in the field. This will lead to definitive conclusions on the impact of genetic variation within the FCGR gene locus on immune function and disease.

The relevance of tumor target expression levels on IgA-mediated cytotoxicity in cancer immunotherapy

Recent advances in cancer immunotherapy, particularly the success of immune checkpoint inhibitors, have reignited interest in targeted monoclonal antibodies for immunotherapy. Antibody therapies aim to minimize on-target, off-tumor toxicity by targeting antigens overexpressed on tumor cells but not on healthy cells. Despite considerable efforts, some therapeutic antibodies have been linked to dose-limiting side effects. Our hypothesis suggests that the efficacy of IgG leads to a lower target expression threshold for tumor cell killing, contributing to these side effects. Earlier, therapeutic IgG antibodies were reformatted into the IgA isotype. Unlike IgG, which primarily engages Fc gamma receptors (FcγR) to induce antibody-dependent cellular cytotoxicity (ADCC) by NK cells and antibody-dependent cellular phagocytosis (ADCP) by monocytes/macrophages, IgA antibodies activate neutrophils through the Fc alpha receptor I (CD89, FcαRI). In previous studies, it appeared that IgA may require a higher target expression threshold for effective killing, and we aimed to investigate this in our current study. Moreover, we investigated how blocking the myeloid checkpoint CD47/SIRPα axis affect the target expression threshold. Using a tetracycline-inducible expression system, we regulated target expression in different cell lines. Our findings from ADCC assays indicate that IgA-mediated PMN ADCC requires a higher antigen expression level than IgG-mediated PBMC ADCC. Furthermore, blocking CD47 enhanced IgA-mediated ADCC, lowering the antigen threshold. Validated in two in vivo models, our results show that IgA significantly reduces tumor growth in high-antigen-expressing tumors without affecting low-antigen-expressing healthy tissues. This suggests IgA-based immunotherapy could potentially minimize on-target, off-tumor side effects, improving treatment efficacy and patient safety.

Investigating the protective effects of Astragalus polysaccharides on cyclophosphamide-induced bone marrow suppression in mice and bone mesenchymal stem cells

BACKGROUND

This study determines the role and mechanism of APS in cyclophosphamide-induced myelosuppression in mice and bone mesenchymal stem cells (BMSCs) cell model.

METHODS

Cy-induced myelosuppression mice and BMSCs cell model were established. Fifty C57BL/6 mice (weighing 20 ± 2 g) were randomly divided into five groups. Femur and tibia samples, bone marrow samples, and blood samples were collected 3 days after the last injection of Cy. Histopathology changes and cell apoptosis were detected. Cell viability, apoptosis, cycle distribution, reactive oxygen species activity, osteogenesis ability, and protein levels were detected. γ-H2AX and senescence-associated β-galactosidase activity expression was detected by immunofluorescence. Cy-induced senescence and Wnt/β-catenin related protein levels were detected using western blotting.

RESULTS

The results showed that APS effectively induced Cy-induced histological injury and cell apoptosis rate. After treated with APS, ROS and ALP levels were significantly increased. In BMSCs, cell viability, apoptosis, and cell cycle distribution were also influenced by APS treatment. Compared with the control group, cell viability was significantly increased, the cell apoptosis rate was decreased while the number of cells remained in the G0-G1 phase was increased. Meanwhile, ROS levels were significantly increased in APS group. Cell senescence and Wnt/β-catenin related protein (γ-H2AX, SA-β-gal, p21, p16, p-β-catenin/ β-catenin, c-Myc, and AXIN2) levels were also altered both in vivo and in vitro. Interestingly, the effects of APS were reversed by BML-284.

CONCLUSION

Our results indicate that APS protected Cy-induced myelosuppression through the Wnt/β-catenin pathway and APS is a potential therapeutic drug for Cy-induced myelosuppression.

Magnetic-driven Interleukin-4 internalization promotes magnetic nanoparticle morphology and size-dependent macrophage polarization

Macrophages are known to depict two major phenotypes: classically activated macrophages (M1), associated with high production of pro-inflammatory cytokines, and alternatively activated macrophages (M2), which present an anti-inflammatory function. A precise control over M1-M2 polarization is a promising strategy in therapeutics to modulate both tissue regeneration and tumor progression processes. However, this is not a simple task as macrophages behave differently depending on the microenvironment. In agreement with this, non-consistent data have been reported regarding macrophages response to magnetic iron oxide nanoparticles (MNPs). To investigate the impact of both tissue microenvironment and MNPs properties on the obtained macrophage responses, single-core (SC) and multi-core (MC) citrate coated MNPs, are synthesized and, afterwards, loaded with a macrophage polarization trigger, IL-4. The developed MNPs are then tested in macrophages subjected to different stimuli. We demonstrate that macrophages treated with low concentrations of MNPs behave differently depending on the polarization stage independently of the concentration of iron. Moreover, we find out that MNPs size and morphology determines the effect of the IL-4 loaded MNPs on M1 macrophages, since IL-4 loaded SC MNPs favor the polarization of M1 macrophages towards M2 phenotype, while IL-4 loaded MC MNPs further stimulate the secretion of pro-inflammatory cytokines.

Human leukocyte immunoglobulin-like receptors in health and disease

Human leukocyte immunoglobulin (Ig)-like receptors (LILR) are a family of 11 innate immunomodulatory receptors, primarily expressed on lymphoid and myeloid cells. LILRs are either activating (LILRA) or inhibitory (LILRB) depending on their associated signalling domains (D). With the exception of the soluble LILRA3, LILRAs mediate immune activation, while LILRB1-5 primarily inhibit immune responses and mediate tolerance. Abnormal expression and function of LILRs is associated with a range of pathologies, including immune insufficiency (infection and malignancy) and overt immune responses (autoimmunity and alloresponses), suggesting LILRs may be excellent candidates for targeted immunotherapies. This review will discuss the biology and clinical relevance of this extensive family of immune receptors and will summarise the recent developments in targeting LILRs in disease settings, such as cancer, with an update on the clinical trials investigating the therapeutic targeting of these receptors.

Anti-Tumor Strategies by Harnessing the Phagocytosis of Macrophages

Macrophages are essential for the human body in both physiological and pathological conditions, engulfing undesirable substances and participating in several processes, such as organism growth, immune regulation, and maintenance of homeostasis. Macrophages play an important role in anti-bacterial and anti-tumoral responses. Aberrance in the phagocytosis of macrophages may lead to the development of several diseases, including tumors. Tumor cells can evade the phagocytosis of macrophages, and "educate" macrophages to become pro-tumoral, resulting in the reduced phagocytosis of macrophages. Hence, harnessing the phagocytosis of macrophages is an important approach to bolster the efficacy of anti-tumor treatment. In this review, we elucidated the underlying phagocytosis mechanisms, such as the equilibrium among phagocytic signals, receptors and their respective signaling pathways, macrophage activation, as well as mitochondrial fission. We also reviewed the recent progress in the area of application strategies on the basis of the phagocytosis mechanism, including strategies targeting the phagocytic signals, antibody-dependent cellular phagocytosis (ADCP), and macrophage activators. We also covered recent studies of Chimeric Antigen Receptor Macrophage (CAR-M)-based anti-tumor therapy. Furthermore, we summarized the shortcomings and future applications of each strategy and look into their prospects with the hope of providing future research directions for developing the application of macrophage phagocytosis-promoting therapy.

Towards a better understanding of human iNKT cell subpopulations for improved clinical outcomes

Invariant natural killer T (iNKT) cells are a unique T lymphocyte population expressing semi-invariant T cell receptors (TCRs) that recognise lipid antigens presented by CD1d. iNKT cells exhibit potent anti-tumour activity through direct killing mechanisms and indirectly through triggering the activation of other anti-tumour immune cells. Because of their ability to induce potent anti-tumour responses, particularly when activated by the strong iNKT agonist αGalCer, they have been the subject of intense research to harness iNKT cell-targeted immunotherapies for cancer treatment. However, despite potent anti-tumour efficacy in pre-clinical models, the translation of iNKT cell immunotherapy into human cancer patients has been less successful. This review provides an overview of iNKT cell biology and why they are of interest within the context of cancer immunology. We focus on the iNKT anti-tumour response, the seminal studies that first reported iNKT cytotoxicity, their anti-tumour mechanisms, and the various described subsets within the iNKT cell repertoire. Finally, we discuss several barriers to the successful utilisation of iNKT cells in human cancer immunotherapy, what is required for a better understanding of human iNKT cells, and the future perspectives facilitating their exploitation for improved clinical outcomes.

Nanoparticle STING Agonist Reprograms the Bone Marrow to an Antitumor Phenotype and Protects Against Bone Destruction

When breast cancer metastasizes to bone, treatment options are limited. Failure to treat bone metastases is thought to be due to therapy-resistant features of the bone marrow microenvironment. Using a murine model of bone metastatic mammary carcinoma, we demonstrate that systemic delivery of polymer nanoparticles loaded with cyclic dinucleotide (CDN) agonists of stimulator of interferon genes (STING) inhibited tumor growth and bone destruction after 7 days of treatment. Each dose of STING-activating nanoparticles trafficked to the bone marrow compartment and was retained within the tumor microenvironment for over 24 hours, enhancing antitumor immunity through proinflammatory cytokine production and early T-cell activation. While acquired resistance mechanisms, including increased levels of immunosuppressive cytokines and the infiltration of regulatory T cells, ultimately limited antitumor efficacy after 2 weeks of treatment, bone protective effects remained. Overall, these studies demonstrate that STING pathway activation, here enabled using a nanomedicine approach to enhance CDN delivery to bone metastatic sites, can reprogram the immune contexture of the bone marrow to an antitumor phenotype that inhibits bone colonization of metastatic breast cancer cells and protects from tumor-mediated bone destruction.

Significance

Bone metastases are difficult to treat due to the inaccessibility of the bone marrow compartment and the immunosuppressive microenvironment that protects resident stem cells. Packaging a STING agonist into a nanoparticle that enables systemic administration and drug accumulation at tumor sites overcomes both barriers to stymie metastatic breast cancer growth.

Ginsenosides: Allies of gastrointestinal tumor immunotherapy

In the past decade, immunotherapy has been the most promising treatment for gastrointestinal tumors. But the low response rate and drug resistance remain major concerns. It is therefore imperative to develop adjuvant therapies to increase the effectiveness of immunotherapy and prevent drug resistance. Ginseng has been used in Traditional Chinese medicine as a natural immune booster for thousands of years. The active components of ginseng, ginsenosides, have played an essential role in tumor treatment for decades and are candidates for anti-tumor adjuvant therapy. They are hypothesized to cooperate with immunotherapy drugs to improve the curative effect and reduce tumor resistance and adverse reactions. This review summarizes the research into the use of ginsenosides in immunotherapy of gastrointestinal tumors and discusses potential future applications.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients' survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial-mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

FcγRIIB controls antibody-mediated target cell depletion by ITIM-independent mechanisms

Many therapeutic antibodies deplete target cells and elicit immunotherapy by engaging activating Fc gamma receptors (FcγRs) on host effector cells. These antibodies are negatively regulated by the inhibitory FcγRIIB (CD32B). Dogma suggests inhibition is mediated through the FcγRIIB immunoreceptor tyrosine-based inhibition motif (ITIM), negatively regulating immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling from activating FcγR. To assess this, we generated experimental models expressing human (h)FcγRIIB on targets or effectors, lacking or retaining ITIM signaling capacity. We demonstrate that signaling through the hFcγRIIB ITIM is dispensable for impairing monoclonal antibody (mAb)-mediated depletion of normal and malignant murine target cells through three therapeutically relevant surface receptors (CD20, CD25, and OX40) affecting immunotherapy. We demonstrate that hFcγRIIB competition with activating FcγRs for antibody Fc, rather than ITIM signaling, is sufficient to impair activating FcγR engagement, inhibiting effector function and immunotherapy.

The burden of SARS-CoV-2 in patients receiving chimeric antigen receptor T cell immunotherapy: everything to lose

INTRODUCTION

Chimeric antigen receptor T (CAR-T) cell immunotherapy has revolutionized the prognosis of refractory or relapsed B-cell malignancies. CAR-T cell recipients have immunosuppression generated by B-cell aplasia leading to a higher susceptibility to respiratory virus infections and poor response to vaccination.

AREAS COVERED

This review focuses on the challenge posed by B-cell targeted immunotherapies: managing long-lasting B-cell impairment during the successive surges of a deadly viral pandemic. We restricted this report to data regarding vaccine efficacy in CAR-T cell recipients, outcomes after developing COVID-19 and specificities of treatment management. We searched in MEDLINE database to identify relevant studies until March 31^st 2022.

EXPERT OPINION

Among available observational studies, the pooled mortality rate reached 40% in CAR-T cell recipients infected by SARS-CoV-2. Additionally, vaccines responses seem to be widely impaired in recipients (seroconversion 20%, T-cell response 50%). In this setting of B-cell depletion, passive immunotherapy is the backbone of treatment. Convalescent plasma therapy has proven to be a highly effective curative treatment with rare adverse events. Neutralizing monoclonal antibodies could be used as pre-exposure prophylaxis or early treatment but their neutralizing activity is constantly challenged by new variants. In order to reduce viral replication, direct-acting antiviral drugs should be considered.

Extracellular vesicles and PDL1 suppress macrophages inducing therapy resistance in TP53-deficient B-cell malignancies

Genetic alterations in the DNA Damage Response (DDR) pathway are a frequent mechanism of resistance to CIT in B-cell malignancies. We have previously shown that the synergy of CIT relies on secretory crosstalk elicited by chemotherapy between the tumour cells and macrophages. Here, we show that loss of multiple different members of the DDR pathway inhibits macrophage phagocytic capacity in vitro and in vivo. Particularly loss of TP53 led to decreased phagocytic capacity ex vivo across multiple B-cell malignancies. We demonstrate via in vivo cyclophosphamide treatment using the Eµ-TCL1 mouse model that loss of macrophage phagocytic capacity in Tp53-deleted leukemia is driven by a significant downregulation of a phagocytic transcriptomic signature using scRNA-Seq. By analysing the tumour B-cell proteome, we identified a TP53 specific upregulation of proteins associated with extracellular vesicles (EV). We abrogated EV biogenesis in tumour B-cells via CRISPR-knockout (KO) of RAB27A and confirmed that the EVs from TP53-deleted lymphoma cells were responsible for the reduced phagocytic capacity and the in vivo CIT resistance. Furthermore, we observed that TP53 loss led to an upregulation of both PD-L1 cell surface expression and secretion of EVs by lymphoma cells. Disruption of EV bound PD-L1 by anti-PD-L1 antibodies or PD-L1 CRISPR-KO improved macrophage phagocytic capacity and in vivo therapy response. Thus, we demonstrate enhanced EV-release and increased PD-L1 expression in TP53-deficient B-cell lymphomas as novel mechanisms of macrophage function alteration in CIT resistance. This study indicates the use of checkpoint inhibition in the combination treatment of B-cell malignancies with TP53 loss.

Tumor-Associated Macrophages: Critical Players in Drug Resistance of Breast Cancer

Drug resistance is one of the most critical challenges in breast cancer (BC) treatment. The occurrence and development of drug resistance are closely related to the tumor immune microenvironment (TIME). Tumor-associated macrophages (TAMs), the most important immune cells in TIME, are essential for drug resistance in BC treatment. In this article, we summarize the effects of TAMs on the resistance of various drugs in endocrine therapy, chemotherapy, targeted therapy, and immunotherapy, and their underlying mechanisms. Based on the current overview of the key role of TAMs in drug resistance, we discuss the potential possibility for targeting TAMs to reduce drug resistance in BC treatment, By inhibiting the recruitment of TAMs, depleting the number of TAMs, regulating the polarization of TAMs and enhancing the phagocytosis of TAMs. Evidences in our review support it is important to develop novel therapeutic strategies to target TAMs in BC to overcome the treatment of resistance.

Co-Delivery of Letrozole and Cyclophosphamide via Folic Acid-Decorated Nanoniosomes for Breast Cancer Therapy: Synergic Effect, Augmentation of Cytotoxicity, and Apoptosis Gene Expression

Breast cancer is one of the most prevalent causes of cancer mortality in women. In order to increase patient prognosis and survival rates, new technologies are urgently required to deliver therapeutics in a more effective and efficient manner. Niosome nanoparticles have been recently employed as therapeutic platforms capable of loading and carrying drugs within their core for both mono and combination therapy. Here, niosome-based nanoscale carriers were investigated as a targeted delivery system for breast cancer therapy. The platform developed consists of niosomes loaded with letrozole and cyclophosphamide (NLC) and surface-functionalized with a folic-acid-targeting moiety (NLCPFA). Drug release from the formulated particles exhibited pH-sensitive properties in which the niosome showed low and high release in physiological and cancerous conditions, respectively. The results revealed a synergic effect in cytotoxicity by co-loading letrozole and cyclophosphamide with an efficacy increment in NLCPFA use in comparison with NLC. The NLCPFA resulted in the greatest drug internalization compared to the non-targeted formulation and the free drug. Additionally, downregulation of cyclin-D, cyclin-E, MMP-2, and MMP-9 and upregulating the expression of caspase-3 and caspase-9 genes were observed more prominently in the nanoformulation (particularly for NLCPFA) compared to the free drug. This exciting data indicated that niosome-based nanocarriers containing letrozole and cyclophosphamide with controlled release could be a promising platform for drug delivery with potential in breast cancer therapy.

There Is Strength in Numbers: Quantitation of Fc Gamma Receptors on Murine Tissue-Resident Macrophages

Many of the effector functions of antibodies rely on the binding of antibodies/immune complexes to cellular Fcγ receptors (FcγRs). Since the majority of innate immune effector cells express both activating and inhibitory Fc receptors, the outcome of the binding of immune complexes to cells of a given population is influenced by the relative affinities of the respective IgG subclasses to these receptors, as well as by the numbers of activating and inhibitory FcγRs on the cell surface. A group of immune cells that has come into focus more recently is the various subsets of tissue-resident macrophages. The central functions of FcγRs on tissue macrophages include the clearance of opsonized pathogens, the removal of small immune complexes from the circulation and the depletion of antibody-opsonized cells in the therapy of autoimmunity and cancer. Despite these essential functions of FcγRs on tissue-resident macrophages, an in-depth quantification of FcγRs is lacking. Thus, the aim of our current study was to quantify the various Fcγ receptors on macrophages in murine liver, lung, kidney, brain, skin and spleen. Our study identified a pronounced heterogeneity between FcγR expression patterns of the different tissue macrophages, which may reflect their specialized functions within their unique niches in different organ environments.

Monoclonal antibody requires immunomodulation for efficacy against Acinetobacter baumannii infection

Monoclonal antibodies (MAbs) are gaining significant momentum as novel therapeutics for infections caused by antibiotic-resistant bacteria. We evaluated the mechanism by which anti-bacterial MAb therapy protects against Acinetobacter baumannii infections. Anti-capsular MAb enhanced macrophage opsonophagocytosis and rescued mice from lethal infections by harnessing complement, macrophages, and neutrophils, yet the degree of bacterial burden did not correlate with survival. Furthermore, MAb therapy reduced pro-inflammatory (IL-1β, IL-6, TNFα) and anti-inflammatory (IL-10) cytokines, which correlated inversely with survival. Although disrupting IL-10 abrogated the survival advantage conferred by the MAb, IL-10-knockout mice treated with MAb could still survive if TNFα production was suppressed directly (via anti-TNFα neutralizing antibody) or indirectly (via macrophage depletion). Thus, even for a MAb that enhances microbial clearance via opsonophagocytosis, clinical efficacy required modulation of pro- and anti-inflammatory cytokines. These findings may inform future MAb development targeting bacteria that trigger the sepsis cascade.

Targeting macrophages in cancer immunotherapy

Immunotherapy is regarded as the most promising treatment for cancers. Various cancer immunotherapies, including adoptive cellular immunotherapy, tumor vaccines, antibodies, immune checkpoint inhibitors, and small-molecule inhibitors, have achieved certain successes. In this review, we summarize the role of macrophages in current immunotherapies and the advantages of targeting macrophages. To better understand and make better use of this type of cell, their development and differentiation characteristics, categories, typical markers, and functions were collated at the beginning of the review. Therapeutic strategies based on or combined with macrophages have the potential to improve the treatment efficacy of cancer therapies.

Disseminated cancer cells in breast cancer: Mechanism of dissemination and dormancy and emerging insights on therapeutic opportunities

Metastatic spread in breast cancer patients is the major driver of cancer-related deaths. A unique subset of cells disseminated from pre-invasive or primary tumor lesions are recognized as the main seeds for metastatic outgrowth. Disseminated cancer cells (DCCs) can migrate to distant organs and settle in a dormant state for a prolonged period until they emerge to overt metastases. Understanding the biology of breast cancer cells dissemination, dormancy and reactivation to form overt metastases has become an important focus. In this review, we discuss the recent advancements of molecular pathways involving breast cancer cell dissemination, role of chemokine-chemokine receptor networks in DCCs migration, DCCs phenotypic heterogeneity and unique genes signatures in tumor dormancy, microenvironmental regulation and specific niches that favors DCCs homing and dormancy. In addition, we also discuss recent findings relating to the role of immune response on DCC dissemination and dormancy. With recent advances in the field of immunotherapy/targeted therapy and its beneficial effects in cancer treatment, this review will focus on their impact on DCCs, reversal of stemness, tumor dormancy and metastatic relapse.

High-throughput phenotypic screen and transcriptional analysis identify new compounds and targets for macrophage reprogramming

Macrophages are plastic and, in response to different local stimuli, can polarize toward multi-dimensional spectrum of phenotypes, including the pro-inflammatory M1-like and the anti-inflammatory M2-like states. Using a high-throughput phenotypic screen in a library of ~4000 FDA-approved drugs, bioactive compounds and natural products, we find ~300 compounds that potently activate primary human macrophages toward either M1-like or M2-like state, of which ~30 are capable of reprogramming M1-like macrophages toward M2-like state and another ~20 for the reverse repolarization. Transcriptional analyses of macrophages treated with 34 non-redundant compounds identify both shared and unique targets and pathways through which the tested compounds modulate macrophage activation. One M1-activating compound, thiostrepton, is able to reprogram tumor-associated macrophages toward M1-like state in mice, and exhibit potent anti-tumor activity. Our compound-screening results thus help to provide a valuable resource not only for studying the macrophage biology but also for developing therapeutics through modulating macrophage activation.

Mechanism of Intestinal Flora and Proteomics on Regulating Immune Function of Durio zibethinus Rind Polysaccharide

In this study, cyclophosphamide was injected intraperitoneally to establish an immunosuppressive mouse model to study the immune regulating effects of Durio zibethinus Murr rind polysaccharide (DZMP) through proteomics and intestinal flora. The results showed that the thymus and spleen indexes of the high-dose DZMP (200 mg/kg) group were significantly increased, and the tissue structure of the spleen was improved compared with the model group ( $P<0.01$ ). The contents of IL-2, IL-4, IL-6, and TNF-α in the high-dose group of DZMP were significantly increased ( $P<0.001$ ). Activities of acid phosphatase (ACP), lactate dehydrogenase (LDH), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) were increased in serum ( $P<0.01$ ). In the liver, catalase (CAT) activity was increased ( $P<0.001$ ) while the malondialdehyde (MDA) content was decreased and immune activity was increased ( $P<0.001$ ). Proteomics studies showed that the drug group could significantly increase the low-affinity immunoglobulin gamma Fc receptor III (FcγRIII) protein and protein kinase C-α (PKC-α) compared with the model group ( $P<0.001$ ). In addition, the result showed that those proteins were likely involved in the regulation of the metabolic pathways of autoimmune thyroid disease, Staphylococcus aureus infection, and NF-κB signaling pathway. Intestinal microbial studies showed that short-chain fatty acid (SCFA) content was increased as well as the relative abundance of beneficial bacteria Akkermansia, Bacteroides, and Paraprevotella, while the relative abundance of Ruminococcus and Oscillospira was decreased compared with the model group ( $P<0.001$ ). The results showed that DZMP might play a beneficial role in immune regulation by improving intestinal flora.

LILRB3 (ILT5) is a myeloid cell checkpoint that elicits profound immunomodulation

Despite advances in identifying the key immunoregulatory roles of many of the human leukocyte immunoglobulin-like receptor (LILR) family members, the function of the inhibitory molecule LILRB3 (ILT5, CD85a, LIR3) remains unclear. Studies indicate a predominant myeloid expression; however, high homology within the LILR family and a relative paucity of reagents have hindered progress toward identifying the function of this receptor. To investigate its function and potential immunomodulatory capacity, a panel of LILRB3-specific monoclonal antibodies (mAbs) was generated. LILRB3-specific mAbs bound to discrete epitopes in Ig-like domain 2 or 4. LILRB3 ligation on primary human monocytes by an agonistic mAb resulted in phenotypic and functional changes, leading to potent inhibition of immune responses in vitro, including significant reduction in T cell proliferation. Importantly, agonizing LILRB3 in humanized mice induced tolerance and permitted efficient engraftment of allogeneic cells. Our findings reveal powerful immunosuppressive functions of LILRB3 and identify it as an important myeloid checkpoint receptor.