Macrophages as a "weapon" in anticancer cellular immunotherapy

A detailed insight into macrophages' role in shaping lung carcinogenesis

Despite significant advancements in cancer treatment in recent decades, the high mortality rate associated with lung cancer remains a significant concern. The development and proper execution of new targeted therapies needs more deep knowledge regarding the lung cancer associated tumour microenvironment. One of the key component of that tumour microenvironment is the lung resident macrophages. Although in normal physiological condition the lung resident macrophages are believed to maintain lung homeostasis, but they may also initiate a vicious inflammatory response in abnormal conditions which is linked to lung cancer development. Depending on the activation pathway, the lung resident macrophages are either of M1 or M2 sub-type. The M1 and M2 sub-types differ significantly in various prospectuses, from phenotypic markers to metabolic pathways. In addition to this generalized classification, the recent advancement of the multiomics technology is able to identify some other sub-types of lung resident macrophages. Researchers have also observed that these different sub-types can manipulate the pathogenesis of lung carcinogenesis in a context dependent manner and can either promote or inhibit the development of lung carcinogenesis upon receiving proper activation. As proper knowledge about the role played by the lung resident macrophages' in shaping the lung carcinogenesis is limited, so the main purpose of this review is to bring all the available information under the same roof. We also elaborated the different mechanisms involved in maintenance of the plasticity of M1/M2 sub-type, as this plasticity can be a good target for lung cancer treatment.

Potential applications of macrophages in cancer immunotherapy

Immunotherapy has improved cancer treatment based on investigations of tumor immune escape. Manipulation of the immune system stimulates antitumor immune responses and blocks tumor immune escape routes. Genetically adoptive cell therapy, such as T cells, has yielded promising results for hematologic malignancies, but their application to solid tumors has been challenging. Macrophages have a wide broad of capabilities in regulating immune responses, homeostasis, and tissue development, as well as the ability to phagocyte, present antigens, and infiltrate the tumor microenvironment (TME). Given the importance of macrophages in cancer development, they could serve as novel tool for tumor treatment. Therefore, macrophages are used in different formats for direct and indirect targeting of tumor cells. This review summarized the available data on the various applications of macrophages in cancer immunotherapy.

Polyunsaturated fatty acids promote M2-like TAM deposition via dampening RhoA-YAP1 signaling in the ovarian cancer microenvironment

BACKGROUND

Peritoneal metastases frequently occur in epithelial ovarian cancer (EOC), resulting in poor prognosis and survival rates. Tumor-associated-macrophages (TAMs) massively infiltrate into ascites spheroids and are multi-polarized as protumoral M2-like phenotype, orchestrating the immunosuppression and promoting tumor progression. However, the impact of omental conditioned medium/ascites (OCM/AS) on TAM polarization and its function in tumor progression remains elusive.

METHODS

The distribution and polarization of TAMs in primary and omental metastatic EOC patients' tumors and ascites were examined by m-IHC, FACS analysis, and immunofluorescence. QPCR, immunofluorescence, FACS analysis, lipid staining assay, ROS assay, and Seahorse real-time cell metabolic assay characterized TAMs as being polarized in the ascites microenvironment. The oncogenic role of TAMs in tumor cells was demonstrated by co-cultured migration/invasion, proliferation, and spheroid formation assays. Mechanistic studies of the regulations of TAM polarization were performed by using RNA-Seq, GTPase pull-down, G-LISA activation assays, and other biochemical assays. A Yap1 macrophages (MФs) conditional knockout (cKO) mouse model demonstrated the roles of YAP1 in TAM polarization status and its pro-metastatic function. Finally, the anti-metastatic potential of targeting TAMs through restoring YAP1 by pharmacological agonist XMU MP1 was demonstrated in vitro and in vivo.

RESULTS

Abundant polyunsaturated fatty acids (PUFAs) in OCM/AS suppressed RhoA-GTPase activities, which, in turn, downregulated nuclear YAP1 in MФs, leading to increased protumoral TAM polarization accompanied by elevated OXPHOS metabolism. Abolishment of YAP1 in MФs further confirmed that a higher M2/M1 ratio of TAM polarization could alleviate CD8+ T cell infiltration and cytotoxicity in vivo. Consistently, the loss of YAP1 has been observed in EOC metastatic tissues, suggesting its clinical relevance. On the contrary, restoration of YAP1 expression by pharmaceutical inhibition of MST1/2 induced conversion of M2-to-M1-like polarized MФs, elevating the infiltration of CD8+ T cells and attenuating tumor growth.

CONCLUSION

This study revealed that PUFAs-enriched OCM/AS of EOC promotes M2-like TAM polarization through RhoA-YAP1 inhibition, where YAP1 downregulation is required for accelerating protumoral M2-like TAM polarization, thereby causing immunosuppression and enhancing tumor progression. Conversion of M2-to-M1-like polarized MФs through Yap1 activation inhibits tumor progression and contributes to developing potential TAMs-targeted immunotherapies in combating EOC peritoneal metastases.

The next frontier in immunotherapy: potential and challenges of CAR-macrophages

Chimeric antigen receptor macrophage (CAR-MΦ) represents a significant advancement in immunotherapy, especially for treating solid tumors where traditional CAR-T therapies face limitations. CAR-MΦ offers a promising approach to target and eradicate tumor cells by utilizing macrophages' phagocytic and antigen-presenting abilities. However, challenges such as the complex tumor microenvironment (TME), variability in antigen expression, and immune suppression limit their efficacy. This review addresses these issues, exploring mechanisms of CAR-MΦ action, optimal construct designs, and interactions within the TME. It also delves into the ex vivo manufacturing challenges of CAR-MΦ, discussing autologous and allogeneic sources and the importance of stringent quality control. The potential synergies of integrating CAR-MΦ with existing cancer therapies like checkpoint inhibitors and conventional chemotherapeutics are examined to highlight possible enhanced treatment outcomes. Furthermore, regulatory pathways for CAR-MΦ therapies are scrutinized alongside established protocols for CAR-T cells, identifying unique considerations essential for clinical trials and market approval. Proposed safety monitoring frameworks aim to manage potential adverse events, such as cytokine release syndrome, crucial for patient safety. Consolidating current research and clinical insights, this review seeks to refine CAR-MΦ therapeutic applications, overcome barriers, and suggest future research directions to transition CAR-MΦ therapies from experimental platforms to standard cancer care options.

Engineered Bio-Based Hydrogels for Cancer Immunotherapy

Immunotherapy represents a revolutionary paradigm in cancer management, showcasing its potential to impede tumor metastasis and recurrence. Nonetheless, challenges including limited therapeutic efficacy and severe immune-related side effects are frequently encountered, especially in solid tumors. Hydrogels, a class of versatile materials featuring well-hydrated structures widely used in biomedicine, offer a promising platform for encapsulating and releasing small molecule drugs, biomacromolecules, and cells in a controlled manner. Immunomodulatory hydrogels present a unique capability for augmenting immune activation and mitigating systemic toxicity through encapsulation of multiple components and localized administration. Notably, hydrogels based on biopolymers have gained significant interest owing to their biocompatibility, environmental friendliness, and ease of production. This review delves into the recent advances in bio-based hydrogels in cancer immunotherapy and synergistic combinatorial approaches, highlighting their diverse applications. It is anticipated that this review will guide the rational design of hydrogels in the field of cancer immunotherapy, fostering clinical translation and ultimately benefiting patients.

Bacteria-Based Backpacks to Enhance Adoptive Macrophage Transfer against Solid Tumors

Adoptive cell therapy has emerged as a promising approach for cancer treatment. However, the transfer of macrophages exhibits limited efficacy against solid tumors due to the dynamic cellular phenotypic shift from antitumor to protumor states within the immunosuppressive tumor microenvironment. In this study, a strategy of attaching bacteria to macrophages (Mø@bac) is reported that endows adoptively infused macrophages with durable stimulation by leveraging the intrinsic immunogenicity of bacteria. These attached bacteria, referred to as backpacks, are encapsulated with adhesive nanocoatings and can sustainably control the cellular phenotypes in vivo. Moreover, Mø@bac can repolarize endogenous tumor-associated macrophages, leading to a more robust immune response and thus reducing the tumor progression in a murine 4T1 cancer model without any side effects. This study utilizing bacteria as cellular backpacks opens a new avenue for the development of cell therapies.

Prognostic role of macrophages and mast cells in the microenvironment of hepatocellular carcinoma after resection

BACKGROUND

The prognostic significance of mast cells and different phenotypes of macrophages in the microenvironment of hepatocellular carcinoma (HCC) following resection is unclear. We aimed in this study to assess the local distribution of infiltrating macrophages and mast cells of specific phenotypes in tissues of HCC and to evaluate their prognostic values for survival of post-surgical patients.

METHODS

The clinicopathological and follow-up data of 70 patients with HCC, who underwent curative resection of tumor from 1997 to 2019, were collected. The infiltration of CD68+ and CD163+ macrophages and CD117+ mast cells was assessed immunohistochemically in representative resected specimens of HCC and adjacent tissues. The area fraction (AF) of positively stained cells was estimated automatically using QuPath image analysis software in several regions, such as tumor center (TC), inner margin (IM), outer margin (OM), and peritumor (PT) area. The prognostic significance of immune cells, individually and in associations, for time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS) was evaluated using Kaplan-Meier and Cox regression analyses.

RESULTS

High AF of CD68+ macrophages in TC and IM and high AF of mast cells in IM and PT area were associated with a longer DFS. High AF of CD163+ macrophages in PT area correlated with a shorter DFS. Patients from CD163TChigh & CD68TClow group had a shorter DFS compared to all the rest of the groups, and cases with CD163IMlow & CD68IMhigh demonstrated significantly longer DFS compared to low AF of both markers. Patients from CD68IMhigh & CD163PTlow group, CD117IMhigh & CD163PTlow group, and CD117PThigh & CD163PTlow group had a significantly longer DFS compared to all other combinations of respective cells.

CONCLUSIONS

The individual prognostic impact of CD68+ and CD163+ macrophages and mast cells in the microenvironment of HCC after resection depends on their abundance and location, whereas the cumulative impact is built upon combination of different cell phenotypes within and between regions.

Deciphering the immune landscape of head and neck squamous cell carcinoma: A single-cell transcriptomic analysis of regulatory T cell responses to PD-1 blockade therapy

Immunotherapy is changing the Head and Neck Squamous Cell Carcinoma (HNSCC) landscape and improving outcomes for patients with recurrent or metastatic HNSCC. A deeper understanding of the tumor microenvironment (TME) is required in light of the limitations of patients' responses to immunotherapy. Here, we aimed to examine how Nivolumab affects infiltrating Tregs in the HNSCC TME. We used single-cell RNA sequencing data from eight tissues isolated from four HNSCC donors before and after Nivolumab treatment. Interestingly, the study found that Treg counts and suppressive activity increased following Nivolumab therapy. We also discovered that changes in the CD44-SSP1 axis, NKG2C/D-HLA-E axis, and KRAS signaling may have contributed to the increase in Treg numbers. Furthermore, our study suggests that decreasing the activity of the KRAS and Notch signaling pathways, and increasing FOXP3, CTLA-4, LAG-3, and GZMA expression, may be mechanisms that enhance the killing and suppressive capacity of Tregs. Additionally, the result of pseudo-temporal analysis of the HNSCC TME indicated that after Nivolumab therapy, the expression of certain inhibitory immune checkpoints including TIGIT, ENTPD1, and CD276 and LY9, were decreased in Tregs, while LAG-3 showed an increased expression level. The study also found that Tregs had a dense communication network with cluster two, and that certain ligand-receptor pairs, including SPP1/CD44, HLA-E/KLRC2, HLA-E/KLRK1, ANXA1/FPR3, and CXCL9/FCGR2A, had notable changes after the therapy. These changes in gene expression and cell interactions may have implications for the role of Tregs in the TME and in response to Nivolumab therapy.

Macrophage infiltration in 3D cancer spheroids to recapitulate the TME and unveil interactions within cancer cells and macrophages to modulate chemotherapeutic drug efficacy

BACKGROUND

Recapitulating the tumor microenvironment (TME) in vitro remains a major hurdle in cancer research. In recent years, there have been significant strides in this area, particularly with the emergence of 3D spheroids as a model system for drug screening and therapeutics development for solid tumors. However, incorporating macrophages into these spheroid cultures poses specific challenges due to the intricate interactions between macrophages and cancer cells.

METHODS

To address this issue, in this study, we established a reproducible healthy multicellular 3D spheroid culture with macrophage infiltrates in order to mimic the TME and modulate the drug's efficacy on cancer cells in the presence of macrophages. A 3D spheroid was established using the human cancer cell line CAL33 and THP1 cell derived M0 macrophages were used as a source of macrophages. Cellular parameters including tumour metabolism, health, and mitochondrial mass were analysed in order to establish ideal conditions. To modulate the interaction of cancer cells with macrophage the ROS, NO, and H2O2 levels, in addition to M1 and M2 macrophage phenotypic markers, were analyzed. To understand the crosstalk between cancer cells and macrophages for ECM degradation, HSP70, HIF1α and cysteine proteases were examined in spheroids using western blotting and qPCR.

RESULTS

The spheroids with macrophage infiltrates exhibited key features of solid tumors, including cellular heterogeneity, metabolic changes, nutrient gradients, ROS emission, and the interplay between HIF1α and HSP70 for upregulation of ECM degradading enzymes. Our results demonstrate that tumor cells exhibit a metabolic shift in the presence of macrophages. Additionally, we have observed a shift in the polarity of M0 macrophages towards tumor-associated macrophages (TAMs) in response to cancer cells in spheroids. Results also demonstrate the involvement of macrophages in regulating HIF-1α, HSP70, and ECM degradation cysteine proteases enzymes.

CONCLUSIONS

This study has significant implications for cancer therapy as it sheds light on the intricate interaction between tumor cells and their surrounding macrophages. Additionally, our 3D spheroid model can aid in drug screening and enhance the predictive accuracy of preclinical studies. The strength of our study lies in the comprehensive characterization of the multicellular 3D spheroid model, which closely mimics the TME.

Nocardia rubra cell wall skeleton regulates tumour-associated macrophage polarization by reprogramming M2 macrophages into M1 macrophages via STAT1/STAT6 pathways

Targeted therapy with tumour-associated macrophages (TAMs) has emerged as a new paradigm for immunotherapy of cervical cancer. Nocardia rubra cell wall skeleton (Nr-CWS) for external use is an immunotherapeutic agent. In this study, we aimed to explore the effects of Nr-CWS on TAMs and the potential mechanisms. Cervical tissue samples were collected before and after Nr-CWS treatment from patients with high-risk HPV infection and cervical intraepithelial neoplasia (CIN). The effect of Nr-CWS on macrophages in vivo was examined by immunohistochemistry and double-labeling immunofluorescence histochemistry. In vitro experiments were performed using a TAM model established by THP-1 cells under Nr-CWS treatment. We found that Nr-CWS treatment significantly reduced the numbers of total macrophages and M2 macrophages, increased the proportion of M1 macrophages and decreased the proportion of M2 macrophages in cervical tissues. After Nr-CWS treatment in vitro, the expression levels of the M1 macrophage markers were increased, while the expression levels of the M2 macrophage markers were decreased. Nr-CWS treatment also activated STAT1 pathways but inhibited STAT6 pathways. These results indicated that Nr-CWS may improve local immune response and reverse immunosuppression by regulating the M2 to M1 polarization of TAMs via STAT1/STAT6 pathways.

Holothurian triterpene glycoside cucumarioside A2-2 induces macrophages activation and polarization in cancer immunotherapy

BACKGROUND

Despite intensive developments of adoptive T cell and NK cell therapies, the efficacy against solid tumors remains elusive. Our study demonstrates that macrophage-based cell therapy could be a potent therapeutic option against solid tumors.

METHODS

To this end, we determine the effect of a natural triterpene glycoside, cucumarioside A2-2 (CA2-2), on the polarization of mouse macrophages into the M1 phenotype, and explore the antitumor activity of the polarized macrophage. The polarization of CA2-2-pretreated macrophages was analyzed by flow cytometry and confocal imaging. The anti-cancer activity of CA2-2 macrophages was evaluated against 4T1 breast cancer cells and EAC cells in vitro and syngeneic mouse model in vivo.

RESULTS

Incubation of murine macrophages with CA2-2 led to polarization into the M1 phenotype, and the CA2-2-pretreated macrophages could selectively target and kill various types of cancer in vitro. Notably, loading near-infrared (NIR) fluorochrome-labeled nanoparticles, MnMEIO-mPEG-CyTE777, into macrophages substantiated that M1 macrophages can target and penetrate tumor tissues in vivo efficiently.

CONCLUSION

In this study, CA2-2-polarized M1 macrophages significantly attenuated tumor growth and prolonged mice survival in the syngeneic mouse models. Therefore, ex vivo CA2-2 activation of mouse macrophages can serve as a useful model for subsequent antitumor cellular immunotherapy developments.

Immunotherapies inducing immunogenic cell death in cancer: insight of the innate immune system

Cancer immunotherapies include monoclonal antibodies, cytokines, oncolytic viruses, cellular therapies, and other biological and synthetic immunomodulators. These are traditionally studied for their effect on the immune system's role in eliminating cancer cells. However, some of these therapies have the unique ability to directly induce cytotoxicity in cancer cells by inducing immunogenic cell death (ICD). Unlike general immune stimulation, ICD triggers specific therapy-induced cell death pathways, based on the release of damage-associated molecular patterns (DAMPs) from dying tumour cells. These activate innate pattern recognition receptors (PRRs) and subsequent adaptive immune responses, offering the promise of sustained anticancer drug efficacy and durable antitumour immune memory. Exploring how onco-immunotherapies can trigger ICD, enhances our understanding of their mechanisms and potential for combination strategies. This review explores the complexities of these immunotherapeutic approaches that induce ICD, highlighting their implications for the innate immune system, addressing challenges in cancer treatment, and emphasising the pivotal role of ICD in contemporary cancer research.

Macrophage-Based Microrobots for Anticancer Therapy: Recent Progress and Future Perspectives

Macrophages, which are part of the mononuclear phagocytic system, possess sensory receptors that enable them to target cancer cells. In addition, they are able to engulf large amounts of particles through phagocytosis, suggesting a potential "Trojan horse" drug delivery approach to tumors by facilitating the engulfment of drug-hidden particles by macrophages. Recent research has focused on the development of macrophage-based microrobots for anticancer therapy, showing promising results and potential for clinical applications. In this review, we summarize the recent development of macrophage-based microrobot research for anticancer therapy. First, we discuss the types of macrophage cells used in the development of these microrobots, the common payloads they carry, and various targeting strategies utilized to guide the microrobots to cancer sites, such as biological, chemical, acoustic, and magnetic actuations. Subsequently, we analyze the applications of these microrobots in different cancer treatment modalities, including photothermal therapy, chemotherapy, immunotherapy, and various synergistic combination therapies. Finally, we present future outlooks for the development of macrophage-based microrobots.

Impact of Macrophages on the Interaction of Cetuximab-Functionalized Polyelectrolyte Capsules with EGFR-Expressing Cancer Cells

Polyelectrolyte capsules (PCs) are a promising tool for anticancer drug delivery and tumor targeting. Surface functionalization of PCs with antibodies is widely used for providing their specific interactions with cancer cells. The efficiency of PC-based targeted delivery systems can be affected by the cellular heterogeneity of the tumor, particularly by the presence of tumor-associated macrophages. We used human epidermoid carcinoma cells and macrophages derived from human leukemia monocytic cells in either monoculture or coculture to analyze the targeting capacity and internalization efficiency of PCs with a mean size of 1.03 ± 0.11 μm. The PCs were functionalized with the monoclonal antibody cetuximab targeting the human epidermal growth factor receptor (EGFR). We have shown that surface functionalization of the PCs with cetuximab ensures a specific interaction with EGFR-expressing cancer cells and promotes capsule internalization. In monoculture, the macrophages derived from human leukemia monocytic cells have been found to internalize both nonfunctionalized PCs and cetuximab-functionalized PCs (Cet-PCs) more intensely compared to epidermoid carcinoma cells. The internalization of Cet-PCs by cancer cells is mediated by lipid rafts of the cell membrane, whereas the PC internalization by macrophages is only slightly influenced by lipid rafts. Experiments with a coculture of human epidermoid carcinoma cells and macrophages derived from human leukemia monocytic cells have shown that Cet-PCs preferentially interact with cancer cells, which are subsequently attacked by macrophages. These data can be used to further improve the strategy of PC functionalization for targeted delivery, with the cellular heterogeneity of the tumor microenvironment taken into consideration.

Different mechanisms of CD200-CD200R induce diverse outcomes in cancer treatment

The CD200 is a cell membrane protein expressed by tumor cells, and its receptor CD200 receptor (CD200R) is expressed by immune cells including macrophages and dendritic cells. The formation of CD200-CD200R inhibits the cellular functions of the targeted immune cells, so CD200 is one type of the immune checkpoint and blockade CD200-CD200R formation is a potential cancer treatment. However, the CD200 blockade has opposite treatment outcomes in different types of cancers. For instance, the CD200R deficient mice have a higher tumor load than the wild type (WT) mice in melanoma suggesting that CD200-CD200R inhibits melanoma. On the other hand, the antibody anti-CD200 treatment in pancreatic ductal adenocarcinoma (PDAC) and head and neck squamous cell carcinoma (HNSCC) significantly reduces the tumor load indicating that CD200-CD200R promotes PDAC and HNSCC. In this work, we hypothesize that different mechanisms of CD200-CD200R in tumor microenvironment could be one of the reasons for the diverse treatment outcomes of CD200 blockade in different types of cancers. We create one Ordinary Differential Equations (ODEs) model for melanoma including the inhibition of CCL8 and regulatory T cells and the switching from M2 to M1 macrophages by CD200-CD200R to capture the tumor inhibition by CD200-CD200R. We also create another ODEs model for PDAC and HNSCC including the promotion of the polarization and suppressive activities of M2 macrophages by CD200-CD200R to generate the tumor promotion by CD200-CD200R. Furthermore, we use these two models to investigate the treatment efficacy of the combination treatment between the CD200-CD200R blockade and the other immune checkpoint inhibitor, anti-PD-1. Our result shows that different mechanisms of CD200-CD200R can induce different treatment outcomes in combination treatments, namely, only the CD200-CD200R blockade reduces tumor load in melanoma and only the anti-PD-1 and CD200 knockout decrease tumor load in PDAC and HNSCC. Moreover, in melanoma, the CD200-CD200R mainly utilizes the inhibitions on M1 macrophages and dendritic cells to inhibit tumor growth, instead of M2 macrophages.

Innate Immune System in the Context of Radiation Therapy for Cancer

Radiation therapy (RT) remains an integral component of modern oncology care, with most cancer patients receiving radiation as a part of their treatment plan. The main goal of ionizing RT is to control the local tumor burden by inducing DNA damage and apoptosis within the tumor cells. The advancement in RT, including intensity-modulated RT (IMRT), stereotactic body RT (SBRT), image-guided RT, and proton therapy, have increased the efficacy of RT, equipping clinicians with techniques to ensure precise and safe administration of radiation doses to tumor cells. In this review, we present the technological advancement in various types of RT methods and highlight their clinical utility and associated limitations. This review provides insights into how RT modulates innate immune signaling and the key players involved in modulating innate immune responses, which have not been well documented earlier. Apoptosis of cancer cells following RT triggers immune systems that contribute to the eradication of tumors through innate and adoptive immunity. The innate immune system consists of various cell types, including macrophages, dendritic cells, and natural killer cells, which serve as key mediators of innate immunity in response to RT. This review will concentrate on the significance of the innate myeloid and lymphoid lineages in anti-tumorigenic processes triggered by RT. Furthermore, we will explore essential strategies to enhance RT efficacy. This review can serve as a platform for researchers to comprehend the clinical application and limitations of various RT methods and provides insights into how RT modulates innate immune signaling.

Tetracyclic 1,4-Naphthoquinone Thioglucoside Conjugate U-556 Blocks the Purinergic P2X7 Receptor in Macrophages and Exhibits Anti-Inflammatory Activity In Vivo

P2X7 receptors (P2X7Rs) are ligand-gated ion channels that play a significant role in inflammation and are considered a potential therapeutic target for some inflammatory diseases. We have previously shown that a number of synthetic 1,4-naphthoquinones are capable of blocking P2X7Rs in neuronal and macrophage cells. In the present investigation, we have demonstrated the ability of the tetracyclic quinone-thioglucoside conjugate U-556, derived from 1,4-naphthoquinone thioglucoside, to inhibit ATP-induced Ca2+ influx and YO-PRO-1 dye uptake, which indicates blocking P2X7R in RAW 264.7 macrophages. This process was accompanied by the inhibition of ATP-induced reactive oxygen species production in macrophages, as well as the macrophage survival strengthening under ATP toxic effects. Nevertheless, U-556 had no noticeable antioxidant capacity. Naphthoquinone-thioglucoside conjugate U-556 binding to the extracellular part of the P2X7R was confirmed by SPR analysis, and the kinetic characteristics of this complex formation were established. Computer modeling predicted that U-556 binds the P2X7R allosteric binding site, topographically similar to that of the specific A438079 blocker. The study of biological activity in in vivo experiments shows that tetracylic conjugate significantly reduces inflammation provoked by carrageenan. The data obtained points out that the observed physiological effects of U-556 may be due to its ability to block the functioning of the P2X7R.

Nanoengineered drug delivery in cancer immunotherapy for overcoming immunosuppressive tumor microenvironment

Almost like a living being in and of itself, tumors actively interact with and modify their environment to escape immune responses. Owing to the pre-formation of cancer-favorable microenvironment prior to anti-cancer treatment, the numerous attempts that followed propose limited efficacy in oncology. Immunogenicity by activation of immune cells within the tumor microenvironment or recruitment of immune cells from nearby lymph nodes is quickly offset as the immunosuppressive environment, rapidly converting immunogenic cells into immune suppressive cells, overriding the immune system. Tumor cells, as well as regulatory cells, namely M2 macrophages, Treg cells, and MDSCs, derived by the immunosuppressive environment, also cloak from potential anti-tumoral factors by directly or indirectly secreting cytokines, such as IL-10 and TGF-β, related to immune regulation. Enzymes and other metabolic or angiogenetic constituents - VEGF, IDO1, and iNOS - are also employed directed for anti-cancer immune cell malfunctioning. Therefore, the conversion of "cold" immunosuppressive environment into "hot" immune responsive environment is of paramount importance, bestowing the advances in the field of cancer immunotherapy the opportunity to wholly fulfill its intended purpose. This paper reviews the mechanisms by which tumors wield to exercise immune suppression and the nanoengineered delivery strategies being developed to overcome this suppression.

Fermented Lettuce Extract Induces Immune Responses through Polarization of Macrophages into the Pro-Inflammatory M1-Subtype

It has been reported that lettuce and its bioactive compounds enhance the host immune system by acting as immune modulators. This study aimed to identify the immunological effect of fermented lettuce extract (FLE) on macrophages. To evaluate the efficacy of FLE in enhancing macrophage function, we measured and compared the levels of macrophage activation-related markers in FLE- and lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Treatment with FLE activated RAW 264.7 macrophages, increased their phagocytic ability, and increased the production of nitric oxide (NO) and pro-inflammatory cytokine levels-similar to LPS. The effects of FLE on M1/M2 macrophage polarization were investigated by determining M1 and M2 macrophage transcript markers in mouse peritoneal macrophages. The FLE-related treatment of peritoneal macrophages enhanced the expression of M1 markers but reduced IL-4 treatment-induced M2 markers. After the generation of tumor-associated macrophages (TAMs), alterations in the levels of M1 and M2 macrophage markers were measured after treatment with FLE. The FLE-related treatment of TAMs increased the expression and production of pro-inflammatory cytokines and also led to the enhanced apoptosis of pancreatic cancer cells. These findings suggest that FLE may be useful for macrophage-targeted cancer therapy because of its ability to regulate the activation and polarization of macrophages in the tumor microenvironment.

Immunosuppressive cells in oncolytic virotherapy for glioma: challenges and solutions

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

Saponins of North Atlantic Sea Cucumber: Chemistry, Health Benefits, and Future Prospectives

Frondosides are the major saponins (triterpene glycosides) of the North Atlantic sea cucumber (Cucumaria frondosa). Frondosides possess amphiphilic characteristics due to the presence of various hydrophilic sugar moieties and hydrophobic genin (sapogenin). Saponins are abundant in holothurians, including in sea cucumbers that are widely distributed across the northern part of the Atlantic Ocean. Over 300 triterpene glycosides have been isolated, identified, and categorized from many species of sea cucumbers. Furthermore, specific saponins from sea cucumbers are broadly classified on the basis of the fron-dosides that have been widely studied. Recent studies have shown that frondoside-containing extracts from C. frondosa exhibit anticancer, anti-obesity, anti-hyperuricemic, anticoagulant, antioxidant, antimicrobial, antiangiogenic, antithrombotic, anti-inflammatory, antitumor, and immunomodulatory activities. However, the exact mechanism(s) of action of biological activities of frondosides is not clearly understood. The function of some frondosides as chemical defense molecules need to be understood. Therefore, this review discusses the different frondosides of C. frondosa and their potential therapeutic activities in relation to the postulated mechanism(s) of action. In addition, recent advances in emerging extraction techniques of frondosides and other saponins and future perspectives are discussed.

Antioxidant, Immunostimulatory, and Anticancer Properties of Hydrolyzed Wheat Bran Mediated through Macrophages Stimulation

Previous studies demonstrated that enzymatic hydrolysis enhances wheat bran (WB) biological properties. This study evaluated the immunostimulatory effect of a WB hydrolysate (HYD) and a mousse enriched with HYD (MH) before and after in vitro digestion on murine and human macrophages. The antiproliferative activity of the harvested macrophage supernatant on colorectal cancer (CRC) cells was also analyzed. MH showed significantly higher content than control mousse (M) in soluble poly- and oligosaccharides (OLSC), as well as total soluble phenolic compounds (TSPC). Although in vitro gastrointestinal digestion slightly reduced the TSPC bioaccessibility of MH, ferulic acid (FA) levels remained stable. HYD showed the highest antioxidant activity followed by MH, which demonstrated a greater antioxidant activity before and after digestion as compared with M. RAW264.7 and THP-1 cells released the highest amounts of pro-inflammatory cytokines after being treated with 0.5 mg/mL of digested WB samples. Treatment with digested HYD-stimulated RAW264.7 supernatant for 96 h showed the most anticancer effect, and spent medium reduced cancer cell colonies more than direct WB sample treatments. Although a lack of inner mitochondrial membrane potential alteration was found, increased Bax:Bcl-2 ratio and caspase-3 expression suggested activation of the mitochondrial apoptotic pathway when CRC cells were treated with macrophage supernatants. Intracellular reactive oxygen species (ROS) were positively correlated with the cell viability in CRC cells exposed to RAW264.7 supernatants (r = 0.78, p < 0.05) but was not correlated in CRC cells treated with THP-1 conditioned media. Supernatant from WB-stimulated THP-1 cells may be able to stimulate ROS production in HT-29 cells, leading to a decrease of viable cells in a time-dependent manner. Therefore, our present study revealed a novel anti-tumour mechanism of HYD through the stimulation of cytokine production in macrophages and the indirect inhibition of cell proliferation, colony formation, and activation of pro-apoptotic proteins expression in CRC cells.

Exploring Monocytes-Macrophages in Immune Microenvironment of Glioblastoma for the Design of Novel Therapeutic Strategies

Gliomas are primary malignant brain tumors. These tumors seem to be more and more frequent, not only because of a true increase in their incidence, but also due to the increase in life expectancy of the general population. Among gliomas, malignant gliomas and more specifically glioblastomas (GBM) are a challenge in their diagnosis and treatment. There are few effective therapies for these tumors, and patients with GBM fare poorly, even after aggressive surgery, chemotherapy, and radiation. Over the last decade, it is now appreciated that these tumors are composed of numerous distinct tumoral and non-tumoral cell populations, which could each influence the overall tumor biology and response to therapies. Monocytes have been proved to actively participate in tumor growth, giving rise to the support of tumor-associated macrophages (TAMs). In GBM, TAMs represent up to one half of the tumor mass cells, including both infiltrating macrophages and resident brain microglia. Infiltrating macrophages/monocytes constituted ~ 85% of the total TAM population, they have immune functions, and they can release a wide array of growth factors and cytokines in response to those factors produced by tumor and non-tumor cells from the tumor microenvironment (TME). A brief review of the literature shows that this cell population has been increasingly studied in GBM TME to understand its role in tumor progression and therapeutic resistance. Through the knowledge of its biology and protumoral function, the development of therapeutic strategies that employ their recruitment as well as the modulation of their immunological phenotype, and even the eradication of the cell population, can be harnessed for therapeutic benefit. This revision aims to summarize GBM TME and localization in tumor niches with special focus on TAM population, its origin and functions in tumor progression and resistance to conventional and experimental GBM treatments. Moreover, recent advances on the development of TAM cell targeting and new cellular therapeutic strategies based on monocyte/macrophages recruitment to eradicate GBM are discussed as complementary therapeutics.

Roles of macrophages on ulcerative colitis and colitis-associated colorectal cancer

Colitis-associated colorectal cancer is the most serious complication of ulcerative colitis. Long-term chronic inflammation increases the incidence of CAC in UC patients. Compared with sporadic colorectal cancer, CAC means multiple lesions, worse pathological type and worse prognosis. Macrophage is a kind of innate immune cell, which play an important role both in inflammatory response and tumor immunity. Macrophages are polarized into two phenotypes under different conditions: M1 and M2. In UC, enhanced macrophage infiltration produces a large number of inflammatory cytokines, which promote tumorigenesis of UC. M1 polarization has an anti-tumor effect after CAC formation, whereas M2 polarization promotes tumor growth. M2 polarization plays a tumor-promoting role. Some drugs have been shown to that prevent and treat CAC effectively by targeting macrophages.

Co-enrichment of CD8-positive T cells and macrophages is associated with clinical benefit of tislelizumab in solid tumors

BACKGROUND

Activated immune cells (IC) in the tumor microenvironment (TME) are critical for anti-tumor efficacy. Greater understanding of the dynamic diversity and crosstalk between IC is needed to clarify their association with immune checkpoint inhibitor efficacy.

METHODS

Patients from three tislelizumab monotherapy trials in solid tumors (NCT02407990, NCT04068519, NCT04004221) were retrospectively divided into subgroups by CD8⁺ T-cell and macrophage (Mφ) levels, assessed via multiplex immunohistochemistry (mIHC; n = 67) or gene expression profiling (GEP; n = 629).

RESULTS

A trend of longer survival was observed in patients with both high CD8⁺ T-cell and Mφ levels versus other subgroups in the mIHC analysis (P = 0.11), which was confirmed with greater statistical significance in the GEP analysis (P = 0.0001). Co-existence of CD8⁺ T cells and Mφ was coupled with elevated CD8⁺ T-cell cytotoxicity, T-cell trafficking, MHC class I antigen presentation signatures/genes, and enrichment of the pro-inflammatory Mφ polarization pathway. Additionally, a high level of pro-inflammatory CD64⁺ Mφ density was associated with an immune-activated TME and survival benefit with tislelizumab (15.2 vs. 5.9 months for low density; P = 0.042). Spatial proximity analysis revealed that closer proximity between CD8⁺ T cells and CD64⁺ Mφ was associated with a survival benefit with tislelizumab (15.2 vs. 5.3 months for low proximity; P = 0.024).

CONCLUSIONS

These findings support the potential role of crosstalk between pro-inflammatory Mφ and cytotoxic T cells in the clinical benefit of tislelizumab.

TRIAL REGISTRATION

NCT02407990, NCT04068519, NCT04004221.

Viability variation of T-cells under ultrasound exposure according to adhesion condition with bubbles

PURPOSE

Although cellular immunotherapy is expected as a new cancer treatment, its therapeutic efficiency is limited in solid tumors, because most cells return to the bloodstream rather than adhere to the target site. Therefore, we are motivated to develop a technique to concentrate the cells in the blood flow using active control of bubble-surrounded cells under ultrasound exposure considering both aspects of cell controllability and viability.

METHODS

We prepared a lipid bubble conjugating ligand to adhere to the surface of the T-cells. First, we evaluated the cell controllability by retaining the cells on a wall of an artificial blood vessel through continuous ultrasound exposure. Next, we investigated the cell viability under ultrasound exposure in a suspension with various bubble concentrations.

RESULTS

We estimated the concentration of bubbles when the adhesion to the cell surface was saturated. Then, we evaluated the cell viability with various conditions of ultrasound exposure and bubble concentrations. However, it was confirmed that cell damage occurred under conditions that achieved proper control of the cells. Therefore, we exposed the cells to burst waves to reduce the applied ultrasound intensity. Consequently, the significant increase in cell viability was confirmed to be inversely proportional to the duty ratio.

CONCLUSION

To retain cells on a vessel wall, determining the appropriate ultrasound condition including sound pressure and waveform is important to maintain cell viability.

Strategies to overcome myeloid cell induced immune suppression in the tumor microenvironment

Cancer progression and metastasis due to tumor immune evasion and drug resistance is strongly associated with immune suppressive cellular responses, particularly in the case of metastatic tumors. The myeloid cell component plays a key role within the tumor microenvironment (TME) and disrupts both adaptive and innate immune cell responses leading to loss of tumor control. Therefore, strategies to eliminate or modulate the myeloid cell compartment of the TME are increasingly attractive to non-specifically increase anti-tumoral immunity and enhance existing immunotherapies. This review covers current strategies targeting myeloid suppressor cells in the TME to enhance anti-tumoral immunity, including strategies that target chemokine receptors to deplete selected immune suppressive myeloid cells and relieve the inhibition imposed on the effector arms of adaptive immunity. Remodeling the TME can in turn improve the activity of other immunotherapies such as checkpoint blockade and adoptive T cell therapies in immunologically "cold" tumors. When possible, in this review, we have provided evidence and outcomes from recent or current clinical trials evaluating the effectiveness of the specific strategies used to target myeloid cells in the TME. The review seeks to provide a broad overview of how myeloid cell targeting can become a key foundational approach to an overall strategy for improving tumor responses to immunotherapy.

An arabinogalactan isolated from Pollen Typhae induces the apoptosis of RKO cells by promoting macrophage polarization

An arabinogalactan (PTPS-1-2) was isolated and characterized from Pollen Typhae, and its potential antitumor effects on activating macrophages to produce immunomodulatory factors and promoting apoptosis in colorectal cancer cells were investigated. Structural characterization showed that PTPS-1-2 had a molecular weight of 59 kDa and was composed of rhamnose, arabinose, glucuronic acid, galactose, and galacturonic acid with a molar ratio of 7.6: 17.1: 6.5: 61.4: 7.4. Its backbone was predominantly composed of T-β-D-Galp, 1,3-β-D-Galp, 1,6-β-D-Galp, 1,3,6-β-D-Galp, 1,4-α-D-GalpA, 1,2-α-L-Rhap, additionally, branches contained 1,5-α-L-Araf, T-α-L-Araf, T-β-D-4-OMe-GlcpA, T-β-D-GlcpA and T-α-L-Rhap. PTPS-1-2 activated RAW264.7 cell by triggering the NF-kB signaling pathway and M1 macrophage polarization. Furthermore, the conditioned medium (CM) of Mφ pretreated with PTPS-1-2 exerted marked antitumor effects by inhibiting RKO cell proliferation and suppressing cell colony formation. Collectively, our findings suggested that PTPS-1-2 might be a therapeutic option for the prevention and treatment of tumors.

New insights into immunomodulatory properties of lactic acid bacteria fermented herbal medicines

The COVID-19 pandemic has brought more attention to the immune system, the body’s defense against infectious diseases. The immunomodulatory ability of traditional herbal medicine has been confirmed through clinical trial research, and has obvious advantages over prescription drugs due to its high number of potential targets and low toxicity. The active compounds of herbal drugs primarily include polysaccharides, saponins, flavonoids, and phenolics and can be modified to produce new active compounds after lactic acid bacteria (LAB) fermentation. LAB, primary source of probiotics, can produce additional immunomodulatory metabolites such as exopolysaccharides, short-chain fatty acids, and bacteriocins. Moreover, several compounds from herbal medicines can promote the growth and production of LAB-based immune active metabolites. Thus, LAB-mediated fermentation of herbal medicines has become a novel strategy for regulating human immune responses. The current review discusses the immunomodulatory properties and active compounds of LAB fermented herbal drugs, the interaction between LAB and herbal medicines, and changes in immunoregulatory components that occur during fermentation. This study also discusses the mechanisms by which LAB-fermented herbal medicines regulate the immune response, including activation of the innate or adaptive immune system and the maintenance of intestinal immune homeostasis.

Remotely Guided Immunobots Engaged in Anti-Tumorigenic Phenotypes for Targeted Cancer Immunotherapy

Building medical microrobots from the body's own cells may circumvent the biocompatibility concern and hence presents more potential in clinical applications to improve the possibility of escaping from the host defense mechanism. More importantly, live cells can enable therapeutically relevant functions with significantly higher efficiency than synthetic systems. Here, live immune cell-derived microrobots from macrophages, i.e., immunobots, which can be remotely steered with externally applied magnetic fields and directed toward anti-tumorigenic (M1) phenotypes, are presented. Macrophages engulf the engineered magnetic decoy bacteria, composed of 0.5 µm diameter silica Janus particles with one side coated with anisotropic FePt magnetic nanofilm and the other side coated with bacterial lipopolysaccharide (LPS). This study demonstrates the torque-based surface rolling locomotion of the immunobots along assigned trajectories inside blood plasma, over a layer of endothelial cells, and under physiologically relevant flow rates. The immunobots secrete signature M1 cytokines, IL-12 p40, TNF-α, and IL-6, and M1 cell markers, CD80 and iNOS, via toll-like receptor 4 (TLR4)-mediated stimulation with bacterial LPS. The immunobots exhibit anticancer activity against urinary bladder cancer cells. This study further demonstrates such immunobots from freshly isolated primary bone marrow-derived macrophages since patient-derivable macrophages may have a strong clinical potential for future cell therapies in cancer.

The Impact of Infused Autograft Absolute Numbers of Immune Effector Cells on Survival Post-Autologous Stem Cell Transplantation

Autologous stem cell transplantation treatment has been viewed as a therapeutic modality to enable the infusion of higher doses of chemotherapy to eradicate tumor cells. Nevertheless, recent reports have shown that, in addition to stem cells, infusion of autograft immune effector cells produces an autologous graft-versus-tumor effect, similar to the graft-versus-tumor effect observed in allogeneic-stem cell transplantation, but without the clinical complications of graft-versus-host disease. In this review, I assess the impact on clinical outcomes following infusions of autograft-antigen presenting cells, autograft innate and adaptive immune effector cells, and autograft immunosuppressive cells during autologous stem cell transplantation. This article is intended to provide a platform to change the current paradigmatic view of autologous stem cell transplantation, from a high-dose chemotherapy-based treatment to an adoptive immunotherapeutic intervention.

Mathematical Modeling and Analysis of CD200-CD200R in Cancer Treatment

CD200 is a cell membrane protein that binds to its receptor, CD200 receptor (CD200R). The CD200 positive tumor cells inhibit the cellular functions of M1 and M2 macrophages and dendritic cells (DCs) through the CD200-CD200R complex, resulting in downregulation of Interleukin-10 and Interleukin-12 productions and affecting the activation of cytotoxic T lymphocytes. In this work, we provide two ordinary differential equation models, one complete model and one simplified model, to investigate how the binding affinities of CD200R and the populations of M1 and M2 macrophages affect the functions of the CD200-CD200R complex in tumor growth. Our simulations demonstrate that (i) the impact of the CD200-CD200R complex on tumor promotion or inhibition highly depends on the binding affinity of the CD200R on M2 macrophages and DCs to the CD200 on tumor cells, and (ii) a stronger binding affinity of the CD200R on M1 macrophages or DCs to the CD200 on tumor cells induces a higher tumor cell density in the CD200 positive tumor. Thus, the CD200 blockade would be an efficient treatment method in this case. Moreover, the simplified model shows that the binding affinity of CD200R on macrophages is the major factor to determine the treatment efficacy of CD200 blockade when the binding affinities of CD200R on M1 and M2 macrophages are significantly different to each other. On the other hand, both the binding affinity of CD200R and the population of macrophages are the major factors to determine the treatment efficacy of CD200 blockade when the binding affinities of CD200R on M1 and M2 macrophages are close to each other. We also analyze the simplified model to investigate the dynamics of the positive and trivial equilibria of the CD200 positive tumor case and the CD200 deficient tumor case. The bifurcation diagrams show that when M1 macrophages dominate the population, the tumor cell density of the CD200 positive tumor is higher than the one of CD200 deficient tumor. Moreover, the dynamics of tumor cell density change from tumor elimination to tumor persistence to oscillation, as the maximal proliferation rate of tumor cells increases.

Biomimetic Nanotherapeutics: Employing Nanoghosts to fight Melanoma

Melanoma is a cancer of melanocytes present at the basal layer of the skin. Nanomedicine has armed us with competent platform to manage such fatal neoplastic diseases. Nevertheless, it suffers from numerous pitfalls such as rapid clearance and opsonization of surface-functionalized carriers, biocompatibility and idiopathic reactions which could be difficult to predict in the patient. Biomimetic approach, a novel step towards personalized medicine bridges these drawbacks by employing endogenous cell membranes to traverse physiological barriers. Camouflaged carriers coated with natural cell membranes possess unique characteristics such as high circulatory periods, and the absence of allogenic and xenogenic responses. Proteins residing on the cell membranes render a diverse range of utilities to the coated nanoparticles including natural efficiency to identify cellular targets, homologous targeting, reticuloendothelial system evasion, biocompatibility and reduced adverse and idiopathic effects. In the present article, we have focused on cell membrane camouflaged nanocarriers for melanoma management. We have discussed various types of biomimetic systems, their processing and coating approaches, and their characterization. We have also enumerated novel avenues in melanoma treatment and the combination of biomimetic systems with smart nanoparticulate systems with the potential to bring breakthroughs in the near future. Additionally, immunotherapy-based biomimetic systems to combat melanoma have been highlighted. Hurdles towards clinical translation and ways to overcome them have been explained in detail.

Designing Lactate Dehydrogenase-Mimicking SnSe Nanosheets To Reprogram Tumor-Associated Macrophages for Potentiation of Photothermal Immunotherapy

Rapid glycolysis of tumor cells produces excessive lactate to trigger acidification of the tumor microenvironment (TME), leading to the formation of immunosuppressive TME and tumor-associated macrophage (TAM) dysfunction. Therefore, reprogramming TAMs by depleting lactate with nanodrugs is expected to serve as an effective means of tumor-targeted immunotherapy. Herein, we report the use of lactic acid dehydrogenase (LDH)-mimicking SnSe nanosheets (SnSe NSs) loaded with a carbonic anhydrase IX (CAIX) inhibitor to reconstruct an acidic and immunosuppressive TME. As expected, this nanosystem could reprogram the TAM to achieve M1 macrophage activation and could also restore the potent tumor-killing activity of macrophages while switching their metabolic mode from mitochondrial oxidative phosphorylation to glycolysis. In addition, the repolarizing effect of SnSe NSs on macrophages was validated in a coculture model of bone marrow-derived macrophages, in three patient-derived malignant pleural effusion and in vivo mouse model. This study proposes a feasible therapeutic strategy for depleting lactate and thus ameliorating acidic TME employing Se-containing nanosheets, which could further amply the effects of TAM-based antitumor immunotherapy.

The importance of N6-methyladenosine modification in tumor immunity and immunotherapy

As the most common and abundant RNA modification in eukaryotic cells, N6-methyladenosine (m6A) modification plays an important role in different stages of tumor. m6A can participate in the regulation of tumor immune escape, so as to enhance the monitoring of tumor by the immune system and reduce tumorgenesis. m6A can also affect the tumor progression by regulating the immune cell responses to tumor in tumor microenvironment. In addition, immunotherapy has become the most popular method for the treatment of cancer, in which targets such as immune checkpoints are also closely associated with m6A. This review discusses the roles of N6-methyladenosine modification in tumor immune regulation, their regulatory mechanism, and the prospect of immunotherapy.

Tumor-Derived Extracellular Vesicles: A Means of Co-opting Macrophage Polarization in the Tumor Microenvironment

Extracellular vesicles (EVs) are a heterogeneous population of membrane-bound parcels of bioactive proteins, nucleic acids, and lipids released from almost all cell types. The diversity of cargo packaged into EVs proffer the induction of an array of effects on recipient cells. EVs released from tumor cells have emerged as a vital means of communication and immune modulation within the tumor microenvironment (TME). Macrophages are an important contributor to the TME with seemingly paradoxical roles promoting either pro- or anti-tumoral immune function depending on their activated phenotypes. Here, we discuss the influence of tumor-derived extracellular vesicles on the functional plasticity of macrophages in tumor progression.