Different tumor microenvironments contain functionally distinct subsets of macrophages derived from Ly6C(high) monocytes

The Diagnostic Significance of CXCL13 in M2 Tumor Immune Microenvironment of Human Astrocytoma

Background: CXCL13 may act as a mediator of tumor-associated macrophage immunity during malignant progression. Objective: The present study clarifies the clinicopathological significances of CXCL13 and its corresponding trend with M2 macrophage in human astrocytoma. Methods: The predictive potential of CXCL13 was performed using 695 glioma samples derived from TCGA lower-grade glioma and glioblastoma (GBMLGG) dataset. CXCL13 and M2 biomarker CD163 were observed by immunohistochemistry in 112 astrocytoma tissues. Results: An in-depth analysis showed that CXCL13 expression was related to the poor prognosis of glioma patients (p = 0.0002) derive from TCGA analysis. High level of CXCL13 was detected in 43 (38.39%) astrocytoma and CXCL13/CD163 coexpression was expressed in 33 (29.46%) cases. The immunoreactivities of CXCL13 and CXCL13/CD163 were found in the malignant lesions, which were both significantly associated with grade, patient survival, and IDH1 mutation. Single CXCL13 and CXCL13/CD163 coexpression predicted poor overall survival in astrocytoma (p = 0.0039 and p = 0.0002, respectively). Multivariate Cox regression analyses manifested CXCL13/CD163 phenotype was a significant independent prognostic indicator of patient outcome in astrocytoma (CXCL13, p = 0.0642; CXCL13/CD163, p = 0.0368). Conclusion: CXCL13 overexpression is strongly linked to CD163+ M2 infiltration in malignant astrocytoma. CXCL13/CD163 coexpression would imply M2c-related aggressive characteristics existing in astrocytoma progression could also provide predictive trends of patient outcomes.

Targeting the Tumor Microenvironment: A Close Up of Tumor-Associated Macrophages and Neutrophils

The importance of the tumor microenvironment (TME) in dynamically regulating cancer progression and influencing the therapeutic outcome is widely accepted and appreciated. Several therapeutic strategies to modify or modulate the TME, like angiogenesis or immune checkpoint inhibitors, showed clinical efficacy and received approval from regulatory authorities. Within recent decades, new promising strategies targeting myeloid cells have been implemented in preclinical cancer models. The predominance of specific cell phenotypes in the TME has been attributed to pro- or anti-tumoral. Hence, their modulation can, in turn, alter the responses to standard-of-care treatments, making them more or less effective. Here, we summarize and discuss the current knowledge and the correlated challenges about the tumor-associated macrophages and neutrophils targeting strategies, current treatments, and future developments.

Rapid acceleration of KRAS-mutant pancreatic carcinogenesis via remodeling of tumor immune microenvironment by PPARδ

Pancreatic intraepithelial neoplasia (PanIN) is a precursor of pancreatic ductal adenocarcinoma (PDAC), which commonly occurs in the general populations with aging. Although most PanIN lesions (PanINs) harbor oncogenic KRAS mutations that initiate pancreatic tumorigenesis; PanINs rarely progress to PDAC. Critical factors that promote this progression, especially targetable ones, remain poorly defined. We show that peroxisome proliferator-activated receptor-delta (PPARδ), a lipid nuclear receptor, is upregulated in PanINs in humans and mice. Furthermore, PPARδ ligand activation by a high-fat diet or GW501516 (a highly selective, synthetic PPARδ ligand) in mutant KRASG12D (KRASmu) pancreatic epithelial cells strongly accelerates PanIN progression to PDAC. This PPARδ activation induces KRASmu pancreatic epithelial cells to secrete CCL2, which recruits immunosuppressive macrophages and myeloid-derived suppressor cells into pancreas via the CCL2/CCR2 axis to orchestrate an immunosuppressive tumor microenvironment and subsequently drive PanIN progression to PDAC. Our data identify PPARδ signaling as a potential molecular target to prevent PDAC development in subjects harboring PanINs.

Two distinct receptor-binding domains of human glycyl-tRNA synthetase 1 displayed on extracellular vesicles activate M1 polarization and phagocytic bridging of macrophages to cancer cells

Macrophages play important roles in cancer microenvironment. Human cytosolic glycyl-tRNA synthetase (GARS1) was previously shown to be secreted via extracellular vesicles (EVs) from macrophages to trigger cancer cell death. However, the effects of GARS1-containing EVs (GARS1-EVs) on macrophages as well as on cancer cells and the working mechanisms of GARS1 in cancer microenvironment are not yet understood. Here we show that GARS1-EVs induce M1 polarization and facilitate phagocytosis of macrophages. GARS1-EVs triggers M1 polarization of macrophage via the specific interaction of the extracellular cadherin subdomains 1-4 of the cadherin EGF LAG seven-pass G-type receptor 2 (CELSR2) with the N-terminal WHEP domain containing peptide region of GARS1, and activates the RAF-MEK-ERK pathway for M1 type cytokine production and phagocytosis. Besides, GARS1 interacted with cadherin 6 (CDH6) of cancer cells via its C-terminal tRNA-binding domain to induce cancer cell death. In vivo model, GARS1-EVs showed potent suppressive activity against tumor initiation via M1 type macrophages. GARS1 displayed on macrophage-secreted extracellular vesicles suppressed tumor growth in dual mode, namely through pro-apoptotic effect on cancer cells and M1 polarization effect on macrophages. Collectively, these results elucidate the unique tumor suppressive activity and mechanism of GARS1-EVs by activating M1 macrophage via CELSR2 as well as by direct killing of cancer cells via CDH6.

Imaging and therapeutic targeting of the tumor immune microenvironment with biologics

The important role of tumor microenvironmental elements in determining tumor progression and metastasis has been firmly established. In particular, the presence and activity profile of tumor-infiltrating immune cells may be associated with the outcome of the disease and may predict responsiveness to (immuno)therapy. Indeed, while some immune cell types, such as macrophages, support cancer cell outgrowth and mediate therapy resistance, the presence of activated CD8⁺ T cells is usually indicative of a better prognosis. It is therefore of the utmost interest to obtain a full picture of the immune infiltrate in tumors, either as a prognostic test, as a way to stratify patients to maximize therapeutic success, or as therapy follow-up. Hence, the non-invasive imaging of these cells is highly warranted, with biologics being prime candidates to achieve this goal.

Cell surface-tethered IL-12 repolarizes the tumor immune microenvironment to enhance the efficacy of adoptive T cell therapy

Immune-activating cytokines such as interleukin-12 (IL-12) hold strong potential for cancer immunotherapy but have been limited by high systemic toxicities. We describe here an approach to safely harness cytokine biology for adoptive cell therapy through uniform and dose-controlled tethering onto the surface of the adoptively transferred cells. Tumor-specific T cells tethered with IL-12 showed superior antitumor efficacy across multiple cell therapy models compared to conventional systemic IL-12 coadministration. Mechanistically, the IL-12-tethered T cells supported a strong safety profile by driving interferon-γ production and adoptively transferred T cell activity preferentially in the tumor. Immune profiling revealed that the tethered IL-12 reshaped the suppressive tumor immune microenvironment, including triggering a pronounced repolarization of monocytic myeloid-derived suppressor cells into activated, inflammatory effector cells that further supported antitumor activity. This tethering approach thus holds strong promise for harnessing and directing potent immunomodulatory cytokines for cell therapies while limiting systemic toxicities.

Aging Leads to Increased Monocytes and Macrophages With Altered CSF-1 Receptor Expression and Earlier Tumor-Associated Macrophage Expansion in Murine Mesothelioma

Increased cancer incidence occurs with the emergence of immunosenescence, highlighting the indispensability of the immune system in preventing cancer and its dysregulation with aging. Tumor-associated macrophages (TAMs) are often present in high numbers and are associated with poor clinical outcomes in solid cancers, including mesothelioma. Monocytes and macrophages from the bone marrow and spleen can respond to tumor-derived factors, such as CSF-1, and initiation of the CSF-1R signaling cascade results in their proliferation, differentiation, and migration to the tumor. Age-related changes occur in monocytes and macrophages in terms of numbers and function, which in turn can impact tumor initiation and progression. Whether this is due to changes in CSF-1R expression with aging is currently unknown and was investigated in this study. We examined monocytes and macrophages in the bone marrow and spleen during healthy aging in young (3–4 months) and elderly (20–24 months) female C57BL/6J mice. Additionally, changes to these tissues and in TAMs were examined during AE17 mesothelioma tumor growth. Healthy aging resulted in an expansion of Ly6C^high monocytes and macrophages in the bone marrow and spleen. CSF-1R expression levels were reduced in elderly splenic macrophages only, suggesting differences in CSF-1R signaling between both cell type and tissue site. In tumor-bearing mice, Ly6C^high monocytes increased with tumor growth in the spleen in the elderly and increased intracellular CSF-1R expression occurred in bone marrow Ly6C^high monocytes in elderly mice bearing large tumors. Age-related changes to bone marrow and splenic Ly6C^high monocytes were reflected in the tumor, where we observed increased Ly6C^high TAMs earlier and expansion of Ly6C^low TAMs later during AE17 tumor growth in the elderly compared to young mice. F4/80^high TAMs increased with tumor growth in both young and elderly mice and were the largest subset of TAMs in the tumor. Together, this suggests there may be a faster transition of Ly6C^high towards F4/80^high TAMs with aging. Amongst TAM subsets, expression of CSF-1R was lowest in F4/80^high TAMs, however Ly6C^low TAMs had higher intracellular CSF-1R expression. This suggests downstream CSF-1R signaling may vary between macrophage subsets, which can have implications towards CSF-1R blockade therapies targeting macrophages in cancer.

TNF-α-Secreting Lung Tumor-Infiltrated Monocytes Play a Pivotal Role During Anti-PD-L1 Immunotherapy

Immune checkpoint blockade (ICB) of the PD-1 pathway revolutionized the survival forecast for advanced non-small cell lung cancer (NSCLC). Yet, the majority of PD-L1⁺ NSCLC patients are refractory to anti-PD-L1 therapy. Recent observations indicate a pivotal role for the PD-L1⁺ tumor-infiltrating myeloid cells in therapy failure. As the latter comprise a heterogenous population in the lung tumor microenvironment, we applied an orthotopic Lewis Lung Carcinoma (LLC) model to evaluate 11 different tumor-residing myeloid subsets in response to anti-PD-L1 therapy. While we observed significantly reduced fractions of tumor-infiltrating MHC-II^low macrophages and monocytes, serological levels of TNF-α restored in lung tumor-bearing mice. Notably, we demonstrated in vivo and in vitro that anti-PD-L1 therapy mediated a monocyte-specific production of, and response to TNF-α, further accompanied by their significant upregulation of CD80, VISTA, LAG-3, SIRP-α and TIM-3. Nevertheless, co-blockade of PD-L1 and TNF-α did not reduce LLC tumor growth. A phenomenon that was partly explained by the observation that monocytes and TNF-α play a Janus-faced role in anti-PD-L1 therapy-mediated CTL stimulation. This was endorsed by the observation that monocytes appeared crucial to effectively boost T cell-mediated LLC killing in vitro upon combined PD-L1 with LAG-3 or SIRP-α blockade. Hence, this study enlightens the biomarker potential of lung tumor-infiltrated monocytes to define more effective ICB combination strategies.

Prognostic values of inflammatory indexes in bevacizumab-treated patients with advanced non-small-cell lung cancer

Purpose:

Inflammatory indexes, including neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII) and lymphocyte-to-monocyte ratio (LMR), have been confirmed as prognostic factors in multiple manigances. However, the prognostic value of these parameters in bevacizumab-treated non-small-cell lung cancer (NSCLC) is still not clear.

Methods:

We retrospectively studied 119 patients with advanced NSCLC who received bevacizumab treatment. The associations of pretreatment NLR, PLR, SII and LMR with progression-free survival (PFS) and overall survival (OS) were analyzed.

Results & Conclusion:

The median PFS and OS of patients with high baseline NLR, PLR and SII and low LMR were significantly decreased than those of patients with low baseline NLR, PLR and SII and high LMR. Multivariable analysis indicated that high baseline SII was independently related with inferior prognosis, and baseline LMR was an independent predictor for OS.

In this study we retrospectively studied 119 patients with advanced non-small-cell lung cancer receiving bevacizumab treatment. We found that the prognosis of the patients with high baseline neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and systemic immune-inflammation index (SII) and low lymphocyte-to-monocyte ratio (LMR) were significantly poorer than those in patients with low baseline NLR, PLR and SII and high LMR. Multivariable analysis indicated that high baseline SII was independently related with inferior progression-free survival and overall survival, and that baseline LMR was an independent predictor for overall survival. This study suggests that we can predict the efficacy of bevacizumab by analyzing several blood cell count indexes.

Nanoparticle based medicines: approaches for evading and manipulating the mononuclear phagocyte system and potential for clinical translation

For decades, nanomedicines have been reported as a potential means to overcome the limitations of conventional drug delivery systems by reducing side effects, toxicity and the non-ideal pharmacokinetic behaviour typically exhibited by small molecule drugs. However, upon administration many nanoparticles prompt induction of host inflammatory responses due to recognition and uptake by macrophages, eliminating up to 95% of the administered dose. While significant advances in nanoparticle engineering and consequent therapeutic efficacy have been made, it is becoming clear that nanoparticle recognition by the mononuclear phagocyte system (MPS) poses an impassable junction in the current framework of nanoparticle development. Hence, this has negative consequences on the clinical translation of nanotechnology with respect to therapeutic efficacy, systemic toxicity and economic benefit. In order to improve the translation of nanomedicines from bench-to-bedside, there is a requirement to either modify nanomedicines in terms of how they interact with intrinsic processes in the body, or modulate the body to be more accommodating for nanomedicine treatments. Here we provide an overview of the current standard for design elements of nanoparticles, as well as factors to consider when producing nanomedicines that have minimal MPS-nanoparticle interactions; we explore this landscape across the cellular to tissue and organ levels. Further, rather than designing materials to suit the body, a growing research niche involves modulating biological responses to administered nanomaterials. We here discuss how developing strategic methods of MPS 'pre-conditioning' with small molecule or biological drugs, as well as implementing strategic dosing regimens, such as 'decoy' nanoparticles, is essential to increasing nanoparticle therapeutic efficacy. By adopting such a perspective, we hope to highlight the increasing trends in research dedicated to improving nanomedicine translation, and subsequently making a positive clinical impact.

Cucurbitacin B controls M2 macrophage polarization to suppresses metastasis via targeting JAK-2/STAT3 signalling pathway in colorectal cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Cucurbitacin B (CuB), extracted from muskmelon pedicel, is a widely available triterpenoid molecule that exerts influence on various biological activities. Modern pharmacological studies have found that cucurbitacin B has many kinds of pharmacological anti-tumor and anti-metastasis functions.

AIM OF THE STUDY

To explore the mechanism of anti-tumor and anti-metastasis effect of cucurbitacin B.

MATERIALS AND METHODS

The effect of cucurbitacin B on the growth of HCT116 and CT-26 was detected by CCK8; apoptosis was determined by flow cytometry and colony formation; the expression of apoptosis-related protein Bax, Bcl-2 and Cleaved-caspase-3 were examined by western Blot. To explore the underlying mechanism of cucurbitacin B against tumor, the Western blot, Immunofluorescence staining, Microscale Thermophoresis assays were used. Multiple molecular biology experiments were applied to validate the effect of polarization of cucurbitacin B-induced macrophages. The supernatant of Cucurbitacin B-induced macrophages and colon cells were co-cultured in vitro, and then transwell and wound healing assay were employed to the related phenotypes. C57BL/6 and BALB/c murine colon cancer model were also used to study the drug effects in vivo.

RESULTS

Cucurbitacin B distinctly induced the apoptosis of CRC cells. It was observed that cucurbitacin B not only inhibited the phosphorylation of JAK2 and STAT3, but also the translocation from the cytosol to the nucleus. Meanwhile, we observed that cucurbitacin B is bound to STAT3. Further experimentation demonstrated that cucurbitacin B reduced the polarization of M2 macrophage by down-regulating JAK2/STAT3 signaling pathway. Cucurbitacin B-induced M2-like macrophages were found to diminish the migration of CRC cells. In vitro study suggested that cucurbitacin inhibited the CRC cells proliferation via JAK2/STAT3 and suppressed the cell migration by suppressing M2-like macrophages polarization. Consistent with in vitro results, the cucurbitacin B therapy significantly inhibited tumor growth and metastasis in mice. Moreover, in vivo the treatment with cucurbitacin B enhanced anti-tumor immunity by regulating M2-like macrophages and promoted the expression of CD4 and CD8 in tumor microenvironment.

CONCLUSION

Our results proved that cucurbitacin B might be a potential candidate agent for adjuvant therapy in the process of CRC growth and metastasis.

Identification and Validation of Immune Cells and Hub Genes in Gastric Cancer Microenvironment

Gastric cancer (GC) is the most common malignant tumor in the digestive system, traditional radiotherapy and chemotherapy are not effective for some patients. The research progress of immunotherapy seems to provide a new way for treatment. However, it is still urgent to predict immunotherapy biomarkers and determine novel therapeutic targets. In this study, the gene expression profiles and clinical data of 407 stomach adenocarcinoma (STAD) patients were downloaded from The Cancer Genome Atlas (TCGA) portal, and the abundance ratio of immune cells in each sample was obtained via the “Cell Type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT)” algorithm. Five immune cells were obtained as a result of abundance comparison, and 295 immune-related genes were obtained through differential gene analysis. Enrichment, protein interaction, and module analysis were performed on these genes. We identified five immune cells associated with infiltration and 20 hub genes, of which five genes were correlated with overall survival. Finally, we used Real-time PCR (RT-PCR) to detect the expression differences of the five hub genes in 18 pairs of GC and adjacent tissues. This research not only provides cellular and gene targets for immunotherapy of GC but also provides new ideas for researchers to explore immunotherapy for various tumors.

Small extracellular vesicles induce resistance to anti-GD2 immunotherapy unveiling tipifarnib as an adjunct to neuroblastoma immunotherapy

Background

Anti-GD2 monoclonal antibody immunotherapy has significantly improved the overall survival rate for high-risk neuroblastoma patients. However, 40% of patients fail to respond or develop resistance to treatment, and the molecular mechanisms by which this occurs remain poorly understood. Tumor-derived small extracellular vesicles (sEVs) have emerged as critical regulators in modulating the response to immunotherapy. In this study, we investigated the role of neuroblastoma-derived sEVs in promoting resistance to the anti-GD2 monoclonal antibody dinutuximab. Moreover, to determine whether pharmacologic inhibition of sEV secretion sensitizes tumors to dinutuximab treatment, we combined dinutuximab with tipifarnib, a farnesyltransferase inhibitor that inhibits sEV secretion.

Methods

We investigated the role of neuroblastoma-derived sEVs in modulating the response to dinutuximab by utilizing the syngeneic 9464D-GD2 mouse model. The effect of neuroblastoma-derived sEVs in modulating the tumor microenvironment (TME) and host immune system were evaluated by RNA-sequencing and flow cytometry. Importantly, we used this mouse model to investigate the efficacy of tipifarnib in sensitizing neuroblastoma tumors to dinutuximab. The effect of tipifarnib on both the TME and host immune system were assessed by flow cytometry.

Results

We demonstrated that neuroblastoma-derived sEVs significantly attenuated the efficacy of dinutuximab in vivo and modulated tumor immune cell infiltration upon dinutuximab treatment to create an immunosuppressive TME that contains more tumor-associated macrophages and fewer tumor-infiltrating NK cells. In addition, we demonstrated that neuroblastoma-derived sEVs suppress splenic NK cell maturation in vivo and dinutuximab-induced NK cell-mediated antibody-dependent cellular cytotoxicity in vitro. Importantly, tipifarnib drastically enhanced the efficacy of dinutuximab-mediated inhibition of tumor growth and prevented the immunosuppressive effects of neuroblastoma-derived sEVs in vivo.

Conclusions

These preclinical findings uncover a novel mechanism by which neuroblastoma-derived sEVs modulate the immune system to promote resistance to dinutuximab and suggest that tipifarnib-mediated inhibition of sEV secretion may serve as a viable treatment strategy to enhance the antitumor efficacy of anti-GD2 immunotherapy in high-risk neuroblastoma patients.

Upregulation of MTA1 in Colon Cancer Drives A CD8+ T Cell-Rich But Classical Macrophage-Lacking Immunosuppressive Tumor Microenvironment

Background

The MTA1 protein encoded by metastasis-associated protein 1 (MTA1) is a key component of the ATP-dependent nucleosome remodeling and deacetylase (NuRD) complex, which is widely upregulated in cancers. MTA1 extensively affects downstream gene expression by participating in chromatin remodeling. Although it was defined as a metastasis-associated gene in first reports and metastasis is a process prominently affected by the tumor microenvironment, whether it affects the microenvironment has not been investigated. In our study, we elucidated the regulatory effect of MTA1 on tumor-associated macrophages (TAMs) and how this regulation affects the antitumor effect of cytotoxic T lymphocytes (CTLs) in the tumor microenvironment of colorectal cancer.

Methods

We detected the cytokines affected by MTA1 expression via a cytokine antibody array in control HCT116 cells and HCT116 cells overexpressing MTA1. Multiplex IHC staining was conducted on a colorectal cancer tissue array from our cancer cohort. Flow cytometry (FCM) was performed to explore the polarization of macrophages in the coculture system and the antitumor killing effect of CTLs in the coculture system. Bioinformatics analysis was conducted to analyze the Cancer Genome Atlas (TCGA) colorectal cancer cohort and single-cell RNA-seq data to assess the immune infiltration status of the TCGA colorectal cancer cohort and the functions of myeloid cells.

Results

MTA1 upregulation in colorectal cancer was found to drive an immunosuppressive tumor microenvironment. In the tumor microenvironment of MTA1-upregulated colorectal cancer, although CD8⁺ T cells were significantly enriched, macrophages were significantly decreased, which impaired the CTL effect of the CD8⁺ T cells on tumor cells. Moreover, upregulated MTA1 in tumor cells significantly induced infiltrated macrophages into tumor-associated macrophage phenotypes and further weakened the cytotoxic effect of CD8⁺ T cells.

Conclusion

Upregulation of MTA1 in colorectal cancer drives an immunosuppressive tumor microenvironment by decreasing the microphages from the tumor and inducing the residual macrophages into tumor-associated microphage phenotypes to block the activation of the killing CTL, which contributes to cancer progression.

Clinical relevance of tumour-associated macrophages

In the past decade, substantial advances have been made in understanding the biology of tumour-associated macrophages (TAMs), and their clinical relevance is emerging. A particular aspect that is becoming increasingly clear is that the interaction of TAMs with cancer cells and stromal cells in the tumour microenvironment enables and sustains most of the hallmarks of cancer. Therefore, manipulation of TAMs could enable improved disease control in a substantial fraction of patients across a large number of cancer types. In this Review, we examine the diversity of TAMs in various cancer indications and how this heterogeneity is being revisited with the advent of single-cell technologies, and then explore the current knowledge on the functional roles of different TAM states and the prognostic and predictive value of TAM-related signatures. We also review agents targeting TAMs that are currently being or will soon be tested in clinical trials, and how manipulations of TAMs can improve existing anticancer treatments. Finally, we discuss how TAM-targeting approaches could be further integrated into routine clinical practice, considering a precision oncology approach and viewing TAMs as a dynamic population that can evolve under treatment pressure.

pH-degradable, bisphosphonate-loaded nanogels attenuate liver fibrosis by repolarization of M2-type macrophages

Fibrosis is a consequence of most chronic liver diseases, but currently no approved antifibrotic treatment is available. M2-type macrophages drive fibrosis progression and prevent regression, even when effective causal therapies have been employed. M2-type macrophages activate a cascade of fibrogenic effector cells and can prevent removal of excess scar tissue. To switch these profibrogenic M2 to fibrolytic (regenerative) macrophages, we developed a pH-degradable, nanogel-based delivery system which can be covalently functionalized with the macrophage-repolarizing bisphosphonate alendronate. The nanogels efficiently deliver the clinically approved drug into hepatic nonparenchymal cells after intravenous administration. They do not eliminate macrophages but repolarize their phenotype and subsequently block fibrosis progression. This approach establishes a nanotherapeutic delivery platform to treat further M2-type macrophage-driven diseases, including cancer.

Immune-suppressive (M2-type) macrophages can contribute to the progression of cancer and fibrosis. In chronic liver diseases, M2-type macrophages promote the replacement of functional parenchyma by collagen-rich scar tissue. Here, we aim to prevent liver fibrosis progression by repolarizing liver M2-type macrophages toward a nonfibrotic phenotype by applying a pH-degradable, squaric ester–based nanogel carrier system. This nanotechnology platform enables a selective conjugation of the highly water-soluble bisphosphonate alendronate, a macrophage-repolarizing agent that intrinsically targets bone tissue. The covalent delivery system, however, promotes the drug’s safe and efficient delivery to nonparenchymal cells of fibrotic livers after intravenous administration. The bisphosphonate payload does not eliminate but instead reprograms profibrotic M2- toward antifibrotic M1-type macrophages in vitro and potently prevents liver fibrosis progression in vivo, mainly via induction of a fibrolytic phenotype, as demonstrated by transcriptomic and proteomic analyses. Therefore, the alendronate-loaded squaric ester–based nanogels represent an attractive approach for nanotherapeutic interventions in fibrosis and other diseases driven by M2-type macrophages, including cancer.

Targeted Accumulation of Macrophages Induced by Microbeam Irradiation in a Tissue-Dependent Manner

Radiation therapy (RT) is a vital component of multimodal cancer treatment, and its immunomodulatory effects are a major focus of current therapeutic strategies. Macrophages are some of the first cells recruited to sites of radiation-induced injury where they can aid in tissue repair, propagate radiation-induced fibrogenesis and influence tumour dynamics. Microbeam radiation therapy (MRT) is a unique, spatially fractionated radiation modality that has demonstrated exceptional tumour control and reduction in normal tissue toxicity, including fibrosis. We conducted a morphological analysis of MRT-irradiated normal liver, lung and skin tissues as well as lung and melanoma tumours. MRT induced distinct patterns of DNA damage, reflecting the geometry of the microbeam array. Macrophages infiltrated these regions of peak dose deposition at variable timepoints post-irradiation depending on the tissue type. In normal liver and lung tissue, macrophages clearly demarcated the beam path by 48 h and 7 days post-irradiation, respectively. This was not reflected, however, in normal skin tissue, despite clear DNA damage marking the beam path. Persistent DNA damage was observed in MRT-irradiated lung carcinoma, with an accompanying geometry-specific influx of mixed M1/M2-like macrophage populations. These data indicate the unique potential of MRT as a tool to induce a remarkable accumulation of macrophages in an organ/tissue-specific manner. Further characterization of these macrophage populations is warranted to identify their organ-specific roles in normal tissue sparing and anti-tumour responses.

Engineering nanobodies for next-generation molecular imaging

In recent years, nanobodies have emerged as ideal imaging agents for molecular imaging. Molecular nanobody imaging combines the specificity of nanobodies with the sensitivity of state-of-the-art molecular imaging modalities, such as positron emission tomography (PET). Given that modifications of nanobodies alter their pharmacokinetics (PK), the engineering strategies that combine nanobodies with radionuclides determine the effectiveness, reliability, and safety of the molecular imaging probes. In this review, we introduce conjugation strategies that have been applied to nanobodies, including random conjugation, ^99mTc tricarbonyl chemistry, sortase A-mediated site-specific conjugation, maleimide-cysteine chemistry, and click chemistries. We also summarize the latest advances in nanobody tracers, emphasizing their preclinical and clinical use. In addition, we elaborate on nanobody-based near-infrared fluorescence (NIRF) imaging and image-guided surgery.

Macrophages: shapes and functions

Macrophages are cells of the innate immune system and represent an important component of the first-line defense against pathogens and tumor cells. Here, their diverse functions in inflammation and tumor defense are described, and the mechanisms, tools, and activation pathways and states applied are presented. The main focus is on the role and origin of reactive oxygen species (ROS), the important signal pathways TLR/NF-κB, and the M1/​​M2 polarization of macrophages.

Short-Term Fasting Synergizes with Solid Cancer Therapy by Boosting Antitumor Immunity

Simple Summary

Stimulating our body’s own immune response to fight cancer is important for the success of cancer treatment in general. To further improve current cancer therapy, preclinical research shows that short-term fasting diets enhance cancer therapy efficacy, such as chemotherapy. Short-term fasting diets are low-caloric and low in protein for 3–5 days; they are usually done every couple of weeks. This review summarizes preclinical and clinical evidence of fasting diets synergizing with cancer therapy by boosting antitumor immunity.

Abstract

Short-term fasting (STF), using a low caloric, low protein fasting mimicking diet (FMD), appears to be a promising strategy to enhance chemotherapy-based cancer efficacy, while potentially alleviating toxicity. Preclinical results suggest that enhanced tumor immunity and decreased growth signaling, via lowering of circulating insulin and insulin growth factor 1 (IGF-1) levels form the potential underlying mechanisms. STF may boost anti-tumor responses by promoting tumor immunogenicity and decreasing local immunosuppression. These findings warrant further studies focused on the combination of STF, not only with chemotherapy, but also with immunotherapy to evaluate the full range of benefits of STF in cancer treatment. Here, we delineate the underlying anticancer mechanisms of fasting. We summarize preclinical evidence of STF boosting antitumor immunity and alleviating immunosuppression, as well as the clinical findings reporting the immunomodulatory effects of STF during various cancer treatments, including immunotherapy.

Research progress in immunotherapy of NSCLC with EGFR sensitive mutations

Lung cancer is a malignant tumor with high incidence and mortality across the world. The use of immune checkpoint inhibitors for lung cancer has improved the prognosis of some lung cancer patients to a greater extent and provided a new direction for the clinical treatment of lung cancer. Immunotherapy still has limitations in terms of its appropriate population and adverse reactions. Particularly for non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation, there has been no major breakthrough in current immunotherapy. Whether immunotherapy can bring new benefits after drug resistance is induced by tyrosine kinase inhibitor-targeted therapy and whether the combination of immunotherapy with other treatments can improve the prognosis remain to be studied in depth. In this article, we provide a detailed review of the relevant characteristics of the tumor microenvironment of NSCLC with EGFR mutation and the current research on immunotherapy for NSCLC with EGFR mutation.

Metabolism of tissue macrophages in homeostasis and pathology

Cellular metabolism orchestrates the intricate use of tissue fuels for catabolism and anabolism to generate cellular energy and structural components. The emerging field of immunometabolism highlights the importance of cellular metabolism for the maintenance and activities of immune cells. Macrophages are embryo- or adult bone marrow-derived leukocytes that are key for healthy tissue homeostasis but can also contribute to pathologies such as metabolic syndrome, atherosclerosis, fibrosis or cancer. Macrophage metabolism has largely been studied in vitro. However, different organs contain diverse macrophage populations that specialize in distinct and often tissue-specific functions. This context specificity creates diverging metabolic challenges for tissue macrophage populations to fulfill their homeostatic roles in their particular microenvironment and conditions their response in pathological conditions. Here, we outline current knowledge on the metabolic requirements and adaptations of macrophages located in tissues during homeostasis and selected diseases.

Histidine-rich glycoprotein (HRGP): Pleiotropic and paradoxical effects on macrophage, tumor microenvironment, angiogenesis, and other physiological and pathological processes

Histidine-rich glycoprotein (HRGP) is a relatively less known glycoprotein, but it is abundant in plasma with a multidomain structure, which allows it to interact with many ligands and regulate various biological processes. HRGP ligands includes heme, Zn²⁺, thrombospondin, plasmin/plasminogen, heparin/heparan sulfate, fibrinogen, tropomyosin, IgG, FcγR, C1q. In many conditions, the histidine-rich region of HRGP strengthens ligand binding following interaction with Zn²⁺ or exposure to low pH, such as sites of tissue injury or tumor growth. The multidomain structure and diverse ligand binding attributes of HRGP indicates that it can act as an extracellular adaptor protein, connecting with different ligands, especially on cell surfaces. Also, HRGP can selectively target IgG, which blocks the production of soluble immune complexes. The most common cell surface ligand of HRGP is heparan sulfate proteoglycan, and the interaction is also potentiated by elevated Zn²⁺ concentration and low pH. Recent reports have shown that HRGP can modulate macrophage polarization and possibly regulate other physiological processes such as angiogenesis, anti-tumor immune response, fibrinolysis and coagulation, soluble immune complex clearance and phagocytosis of apoptotic/necrosis cells. In addition, it has also been reported that HRGP has antibacterial and anti-HIV infection effects and may be used as a novel clinical biomarker accordingly. This review outlines the molecular, structural and biological properties of HRGP as well as presenting an update on the function of HRGP in various physiological processes.

Nanobodies as molecular imaging probes

Camelidae derived single-domain antibodies (sdAbs), commonly known as nanobodies (Nbs), are the smallest antibody fragments with full antigen-binding capacity. Owing to their desirable properties such as small size, high specificity, strong affinity, excellent stability, and modularity, nanobodies are on their way to overtake conventional antibodies in terms of popularity. To date, a broad range of nanobodies have been generated against different molecular targets with applications spanning basic research, diagnostics, and therapeutics. In the field of molecular imaging, nanobody-based probes have emerged as a powerful tool. Radioactive or fluorescently labeled nanobodies are now used to detect and track many targets in different biological systems using imaging techniques. In this review, we provide an overview of the use of nanobodies as molecular probes. Additionally, we discuss current techniques for the generation, conjugation, and intracellular delivery of nanobodies.

Heterogeneity and function of macrophages in the breast during homeostasis and cancer

Macrophages are diverse immune cells populating all tissues and adopting a unique tissue-specific identity. Breast macrophages play an essential role in the development and function of the mammary gland over one's lifetime. In the recent years, with the development of fate-mapping, imaging and scRNA-seq technologies we grew a better understanding of the origin, heterogeneity and function of mammary macrophages in homeostasis but also during breast cancer development. Here, we aim to provide a comprehensive review of the latest improvements in studying the macrophage heterogeneity in healthy mammary tissues and breast cancer.

Molecular imaging of tumor-associated macrophages in cancer immunotherapy

Tumor-associated macrophages (TAMs), the most abundant inflammatory cell group in the tumor microenvironment, play an essential role in tumor immune regulation. The infiltration degree of TAMs in the tumor microenvironment is closely related to tumor growth and metastasis, and TAMs have become a promising target in tumor immunotherapy. Molecular imaging is a new interdisciplinary subject that combines medical imaging technology with molecular biology, nuclear medicine, radiation medicine, and computer science. The latest progress in molecular imaging allows the biological processes of cells to be visualized in vivo, which makes it possible to better understand the density and distribution of macrophages in the tumor microenvironment. This review mainly discusses the application of targeting TAM in tumor immunotherapy and the imaging characteristics and progress of targeting TAM molecular probes using various imaging techniques.

Immune Infiltration Associated MAN2B1 Is a Novel Prognostic Biomarker for Glioma

Mannosidase Alpha Class 2B Member 1 (MAN2B1) gene encodes lysosomal alpha-d-mannosidase involved in the ordered degradation of N-linked glycoproteins. Alteration in MAN2B1 has been proved to be accountable for several diseases. However, the relationship between MAN2B1 and glioma malignancy remains unclear. In this study, RNA-seq data from The Cancer Genome Atlas and the Chinese Glioma Genome Atlas datasets were analyzed to explore the correlation between MAN2B1 and clinicopathological features, prognosis, and somatic mutations in gliomas. We found that MAN2B1 was elevated in glioma and was correlated with malignant clinical and molecular features. Upregulated expression of MAN2B1 is prognostic for poor outcomes in glioma patients. Different frequencies of somatic mutations were found in gliomas between high and low MAN2B1 expression. Real-time quantitative polymerase chain reaction, western blot, and immunohistochemistry staining from glioma patient samples and cell lines were used to validate bioinformatic findings. Functional enrichment analysis showed that MAN2B1 was involved in immune and inflammation processes. Moreover, MAN2B1 expression was strongly correlated with M2 macrophages and weakly correlated with M1 macrophages. Further analysis confirmed that MAN2B1 was closely associated with the markers of M2 macrophages and tumor-associated macrophages. Taken together, MAN2B1 is a potential prognostic biomarker in glioma and associates with immune infiltration.

MicroRNA-200c Attenuates the Tumor-Infiltrating Capacity of Macrophages

Simple Summary

The tumor microenvironment determines the prognosis and outcome for cancer patients. Herein, tumor-associated macrophages are not only highly abundant, but also play a crucial role in shaping a tumor-supporting microenvironment. Both their recruitment to the tumor as well as their functional polarization toward a pro-tumorigenic phenotype are mediated by tumor-derived factors including microRNAs. However, the impact of most microRNAs on the tumor cell-macrophage crosstalk remains to be elucidated. Thus, we reached out to investigate the role of hsa-miR-200c-3p (miR-200c) in tumor cell–macrophage interactions, as it was shown to be differentially expressed during cancer progression and metastasis. miR-200c was highly expressed in MCF7 breast tumor cells compared to macrophages. Furthermore, we identified a CD36-dependent uptake of miR-200c, derived from apoptotic tumor cells, into macrophages. In macrophages, elevated miR-200c levels reduced the expression of numerous migration-associated mRNAs, consequently reducing the capacity of macrophages to infiltrate into tumor spheroids. Finally, a distinct signature of miR-200c-repressed, predicted targets was identified, which strongly correlated with tumor infiltration. Targeting the miR-200c transfer from dying tumor cells to macrophages might therefore provide the opportunity to specifically modulate tumor-associated macrophage recruitment.

Abstract

Macrophages constitute a major part of the tumor-infiltrating immune cells. Within the tumor microenvironment, they acquire an alternatively activated, tumor-supporting phenotype. Factors released by tumor cells are crucial for the recruitment of tumor-associated macrophages. In the present project, we aimed to understand the role of hsa-miR-200c-3p (miR-200c) in the interplay between tumor cells and macrophages. To this end, we employed a coculture system of MCF7 breast tumor cells and primary human macrophages and observed the transfer of miR-200c from apoptotic tumor cells to macrophages, which required intact CD36 receptor in macrophages. We further comprehensively determined miR-200c targets in macrophages by mRNA-sequencing and identified numerous migration-associated mRNAs to be downregulated by miR-200c. Consequently, miR-200c attenuated macrophage infiltration into 3-dimensional tumor spheroids. miR-200c-mediated reduction in infiltration further correlated with a miR-200c migration signature comprised of the four miR-200c-repressed, predicted targets PPM1F, RAB11FIB2, RDX, and MSN.

ALDH3A1 overexpression in OSCC inhibits inflammation via phospho‐Ser727 at STAT3 in tumor‐associated macrophages

OBJECTIVES

Cancer-related inflammation (CRI) significantly increases the difficulty of treating oral squamous cell carcinoma (OSCC) and remains a major treatment challenge. Our objective was to determine whether tumor ALDH3A1 could attenuate OSCC tumorigenesis by inhibiting tumor-associated macrophages (TAMs) that promoted CRI.

MATERIALS AND METHODS

ALDH3A1 in Cal27 cells was overexpressed, and the tumor-conditioned medium (TCM) was collected. We induced THP-1 cells with TCM and recombinant human IL-6. The phosphorylation of STAT3 and the TLR4/TRAF6/TBK1 cascade reaction in TAMs was analyzed using Western blotting, and mitochondrial ROS (mtROS) production was measured using a MitoSox kit. A tumorigenicity assay was performed to examine the tumor volume and weight, and the expression of CD68, CD11b, IL-6, Ki67, and CD31 was analyzed via immunohistochemistry.

RESULTS

ALDH3A1 attenuated STAT3 phosphorylation at Ser727 rapidly and mtROS production earlier in TAMs via inhibiting TLR4/TRAF6/TBK1 cascade reaction. MtROS reduction inhibited IL-1β and IL-8 secretions by NLRP3/caspase-1/IL-1β/IL-8 pathway. Meanwhile, the inhibition of pro-tumor phenotypes of TAMs, tumor proliferation, and tumor angiogenesis during the process was proved in vivo.

CONCLUSION

ALDH3A1 was associated closely with CRI and inhibited CRI regulated by TAMs. This finding may achieve clinical transformation and open new therapeutic options for targeting CRI regulated by TAMs.

The Impact of Obesity, Adipose Tissue, and Tumor Microenvironment on Macrophage Polarization and Metastasis

Simple Summary

The inflammatory adipose microenvironment in obesity plays a crucial role in cancer development and metastases. By focusing on adipocytes and macrophages, as well as the extracellular matrix, the cellular and molecular mechanisms that link inflammation, obesity, and cancer will be addressed by this review. After describing the tumor microenvironment and extracellular matrix, the influence of M1, M2, and tumor-associated macrophages will be explored through their origin, classification, polarization, and regulatory networks, including their potential role in angiogenesis, invasion, metastasis, and immunosuppression, with a specific focus on the roles of adipocytes in this process.

Abstract

Tumor metastasis is a major cause of death in cancer patients. It involves not only the intrinsic alterations within tumor cells, but also crosstalk between these cells and components of the tumor microenvironment (TME). Tumorigenesis is a complex and dynamic process, involving the following three main stages: initiation, progression, and metastasis. The transition between these stages depends on the changes within the extracellular matrix (ECM), in which tumor and stromal cells reside. This matrix, under the effect of growth factors, cytokines, and adipokines, can be morphologically altered, degraded, or reorganized. Many cancers evolve to form an immunosuppressive TME locally and create a pre-metastatic niche in other tissue sites. TME and pre-metastatic niches include myofibroblasts, immuno-inflammatory cells (macrophages), adipocytes, blood, and lymphatic vascular networks. Several studies have highlighted the adipocyte-macrophage interaction as a key driver of cancer progression and dissemination. The following two main classes of macrophages are distinguished: M1 (pro-inflammatory/anti-tumor) and M2 (anti-inflammatory/pro-tumor). These cells exhibit distinct microenvironment-dependent phenotypes that can promote or inhibit metastasis. On the other hand, obesity in cancer patients has been linked to a poor prognosis. In this regard, tumor-associated adipocytes modulate TME through the secretion of inflammatory mediators, which modulate and recruit tumor-associated macrophages (TAM). Hereby, this review describes the cellular and molecular mechanisms that link inflammation, obesity, and cancer. It provides a comprehensive overview of adipocytes and macrophages in the ECM as they control cancer initiation, progression, and invasion. In addition, it addresses the mechanisms of tumor anchoring and recruitment for M1, M2, and TAM macrophages, specifically highlighting their origin, classification, polarization, and regulatory networks, as well as their roles in the regulation of angiogenesis, invasion, metastasis, and immunosuppression, specifically highlighting the role of adipocytes in this process.

Systemic Influences of Mammary Cancer on Monocytes in Mice

There is a growing body of evidence that cancer causes systemic changes. These influences are most evident in the bone marrow and the blood, particularly in the myeloid compartment. Here, we show that there is an increase in the number of bone marrow, circulating and splenic monocytes by using mouse models of breast cancer caused by the mammary epithelial expression of the polyoma middle T antigen. Cancer does not affect ratios of classical to non-classical populations of monocytes in the circulation nor does it affect their half-lives. Single cell RNA sequencing also indicates that cancer does not induce any new monocyte populations. Cancer does not change the monocytic progenitor number in the bone marrow, but the proliferation rate of monocytes is higher, thus providing an explanation for the expansion of the circulating numbers. Deep RNA sequencing of these monocytic populations reveals that cancer causes changes in the classical monocyte compartment, with changes evident in bone marrow monocytes and even more so in the blood, suggesting influences in both compartments, with the down-regulation of interferon type 1 signaling and antigen presentation being the most prominent of these. Consistent with this analysis, down-regulated genes are enriched with STAT1/STAT2 binding sites in their promoter, which are transcription factors required for type 1 interferon signaling. However, these transcriptome changes in mice did not replicate those found in patients with breast cancer. Consequently, this mouse model of breast cancer may be insufficient to study the systemic influences of human cancer.

Spatial immune heterogeneity of hypoxia-induced exhausted features in high-grade glioma

The tumor immune microenvironment (TIME) in high-grade glioma (HGG) exhibits high spatial heterogeneity. Though the tumor core and peripheral regions have different biological features, the cause of this spatial heterogeneity has not been clearly elucidated. Here, we examined the spatial heterogeneity of HGG using core and peripheral regions obtained separately from the patients with HGG. We analyzed infiltrating immune cells by flow cytometry from 34 patients with HGG and the transcriptomes by RNA-seq analysis from 18 patients with HGG. Peripheral region-infiltrating immune cells were in vitro cultured in hypoxic conditions and their immunophenotypes analyzed. We analyzed whether the frequencies of exhausted CD8⁺ T cells and immunosuppressive cells in the core or peripheral regions are associated with the survival of patients with HGG. We found that terminally exhausted CD8⁺ T cells and immunosuppressive cells, including regulatory T (T_REG) cells and M2 tumor-associated macrophages (TAMs), are more enriched in the core regions than the peripheral regions. Terminally exhausted and immunosuppressive profiles in the core region significantly correlated with the hypoxia signature, which was enriched in the core region. Importantly, in vitro culture of peripheral region-infiltrating immune cells in hypoxic conditions resulted in an increase in terminally exhausted CD8⁺ T cells, CTLA-4⁺ T_REG cells, and M2 TAMs. Finally, we found that a high frequency of PD-1⁺CTLA-4⁺CD8⁺ T cells in the core regions was significantly associated with decreased progression-free survival of patients with HGG. The hypoxic condition in the core region of HGG directly induces an immunosuppressive TIME, which is associated with patient survival.

Tumors resurrect an embryonic vascular program to escape immunity

[Figure: see text].

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Metabolism in tumor-associated macrophages

Macrophages functionally adapt to a diverse set of signals, a process that is critical for their role in maintaining or restoring tissue homeostasis. This process extends to cancer, where macrophages respond to a series of inflammatory and metabolic cues that direct a maladaptive healing response. Tumor-associated macrophages (TAMs) have altered glucose, amino acid, and lipid metabolic profiles, and interfering with this metabolic shift can blunt the ability of macrophages to promote tumor growth, metastasis, and the creation of an immunosuppressive microenvironment. Here we will review changes in metabolites and metabolic pathways in TAMs and link these with the phenotypic and functional properties of the cells. We will also discuss current strategies targeting TAM metabolism as a therapeutic intervention in cancer.

Role of macrophages in cancer progression and targeted immunotherapies

The vast complexity of the tumor microenvironment (TME) aggrandizes the underlying principles responsible for immune escape, therapy resistance, and treatment failure. The stromal and immune cell population circumjacent to the tumor cells affects the cancer cell cycle leading to tumor progression. Tumor-associated macrophages (TAMs) exhibiting a unique M2 polarization state constitute a significant portion of the TME. They serve as tumor suppressors at early stages and tumor promoters at advanced stages by governing various microenvironmental cues. TAMs secreted various pro-tumoral cytokines, chemokines, and matrix metalloproteases are known to regulate the different cell cycle molecules including checkpoint inhibitors in cancer cells leading to cell cycle progression with faulty cellular components. Moreover, TAMs are well-known immunosuppressors and thereby facilitating the tumor cells' evasion from immune recognition. This chapter will describe the interaction between TAMs and tumor cells, the involvement of TAMs in the regulation of cancer cell progression by controlling cell cycle checkpoints or molecular pathways, and current TAM-based therapies, including restriction of TAM recruitment, anti-survival strategies, or switching polarity. Moreover, this chapter will also emphasize recently developed drug targets and CAR-macrophage cell therapy that restricts tumor progression.

Enabling CAR-T cells for solid tumors: Rage against the suppressive tumor microenvironment

Adoptive T cell therapies based on chimeric antigen receptors (CAR-T) are emerging as genuine therapeutic options for the treatment of hematological malignancies. The observed clinical success has not yet been extended into solid tumor indications as a result of multiple factors including immunosuppressive features of the tumor microenvironment (TME). In this context, an emerging strategy is to design CAR-T cells for the elimination of defined cellular components of the TME, with the objective of re-shaping the tumor immune contexture to control tumor growth. Relevant cell components that are currently under investigation as targets of CAR-T therapies include the tumor vasculature, cancer-associated fibroblasts (CAFs), and immunosuppressive tumor associated macrophages (TAMs) and myeloid derived suppressor cells (MDSCs). In this review, we recapitulate the rapidly expanding field of CAR-T cell therapies that directly target cellular components within the TME with the ultimate objective of promoting immune function, either alone or in combination with other cancer therapies.

Roles of tumor-associated macrophages in tumor progression: implications on therapeutic strategies

Macrophages are heterogeneous cells that present as different functional phenotypes due to their plasticity. They can be classified into two categories, namely M1- and M2-like macrophages, which are involved in processes as diverse as anti-tumor activity and immunosuppressive tumor promotion. Tumor-associated macrophages (TAMs) are defined as being of an M2-type and are considered as the active component in tumor microenvironment. TAMs are involved in multiple processes of tumor progression through the expression of cytokines, chemokines, growth factors, protein hydrolases and more, which lead to enhance tumor cell proliferation, angiogenesis, and immunosuppression, which in turn supports invasion and metastasis. It is assumed that the abundance of TAMs in major solid tumors is correlated to a negative patient prognosis. Because of the currently available data of the TAMs’ role in tumor development, these cells have emerged as a promising target for novel cancer treatment strategies. In this paper, we will briefly describe the origins and types of TAMs and will try to comprehensively show how TAMs contribute to tumorigenesis and disease progression. Finally, we will present the main TAM-based therapeutic strategies currently available.

Macrophages play a role in inflammatory transformation of colorectal cancer

Colorectal cancer (CRC) is one of the most common and fatal cancers worldwide, and it is also a typical inflammatory cancer. The function of macrophages is very important in the tissue immune microenvironment during inflammatory and carcinogenic transformation. Here, we evaluated the function and mechanism of macrophages in intestinal physiology and in different pathological stages. Furthermore, the role of macrophages in the immune microenvironment of CRC and the influence of the intestinal population and hypoxic environment on macrophage function are summarized. In addition, in the era of tumor immunotherapy, CRC currently has a limited response rate to immune checkpoint inhibitors, and we summarize potential therapeutic strategies for targeting tumor-associated macrophages.

Suppressing MDSC Recruitment to the Tumor Microenvironment by Antagonizing CXCR2 to Enhance the Efficacy of Immunotherapy

Simple Summary

While the development of immunotherapy has greatly advanced cancer treatment, many patients do not benefit from immunotherapy. Numerous strategies have been developed to improve response to immunotherapy across cancer types, including blocking the activity of immunosuppressive immune cells, cytokines, and signaling pathways that are linked to poor responses. Myeloid-derived suppressor cells (MDSCs) are associated with poor responses to immunotherapy, and the chemokine receptor, CXCR2, is involved in recruiting MDSCs to the tumor. In this review, we present studies that explore the potential of inhibiting MDSCs through blocking CXCR2 as a strategy to enhance response to existing and novel immunotherapies.

Abstract

Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of cells derived from immature myeloid cells. These cells are often associated with poor responses to cancer therapy, including immunotherapy, in a variety of tumor types. The C-X-C chemokine receptor 2 (CXCR2) signaling axis plays a key role in the migration of immunosuppressive MDSCs into the tumor microenvironment (TME) and the pre-metastatic niche. MDSCs impede the efficacy of immunotherapy through a variety of mechanisms. Efforts to target MDSCs by blocking CXCR2 is an active area of research as a method for improving existing and novel immunotherapy strategies. As immunotherapies gain approval for a wider array of clinical indications, it will become even more important to understand the efficacy of CXCR2 inhibition in combating immunotherapy resistance at different stages of tumor progression.

Polypharmacological reprogramming of tumor-associated macrophages towards an inflammatory phenotype

Tumor-associated macrophages (TAM) are an important component of the tumor microenvironment (TME) that can promote tumor progression, metastasis, and resistance to therapies. Although TAMs represent a promising target for therapeutic intervention, the complexity of the TME has made the study of TAMs challenging. Here, we established a physiologically relevant in vitro TAM polarization system that recapitulates TAM pro-tumoral activities. This system was used to characterize dynamic changes in gene expression and protein phosphorylation during TAM polarization and to screen phenotypic kinase inhibitors that impact TAM programming. BMS-794833, a multi-targeted compound, was identified as a potent inhibitor of TAM polarization. BMS-794833 decreased pro-tumoral properties of TAMs in vitro and suppressed tumor growth in mouse triple-negative breast cancer models. The effect of BMS-794833 was independent of its primary targets (MET and VEGFR2) but was dependent on its effect on multiple signaling pathways, including focal adhesion kinases, SRC family kinases, STAT3, and p38 MAP kinases. Collectively, these findings underline the efficacy of polypharmacological strategies in reprogramming complex signaling cascades activated during TAM polarization.

Inflammatory Components of the Thyroid Cancer Microenvironment: An Avenue for Identification of Novel Biomarkers

The incidence of thyroid cancer in the United States is on the rise with an appreciably high disease recurrence rate of 20-30%. Anaplastic thyroid cancer (ATC), although rare in occurrence, is an aggressive form of cancer with limited treatment options and bleak cure rates. This chapter uses discussions of in vitro models that are representative of papillary, anaplastic, and follicular thyroid cancer to evaluate the crosstalk between specific cells of the tumor microenvironment (TME), which serves as a highly heterogeneous realm of signaling cascades and metabolism that are associated with tumorigenesis. The cellular constituents of the TME carry out varying characteristic immunomodulatory functions that are discussed throughout this chapter. The aforementioned cell types include cancer-associated fibroblasts (CAFs), endothelial cells (ECs), and cancer stem cells (CSCs), as well as specific immune cells, including natural killer (NK) cells, dendritic cells (DCs), mast cells, T regulatory (Treg) cells, CD8+ T cells, and tumor-associated macrophages (TAMs). TAM-mediated inflammation is associated with a poor prognosis of thyroid cancer, and the molecular basis of the cellular crosstalk between macrophages and thyroid cancer cells with respect to inducing a metastatic phenotype is not yet known. The dynamic nature of the physiological transition to pathological metastatic phenotypes when establishing the TME encompasses a wide range of characteristics that are further explored within this chapter, including the roles of somatic mutations and epigenetic alterations that drive the genetic heterogeneity of cancer cells, allowing for selective advantages that aid in their proliferation. Induction of these proliferating cells is typically accomplished through inflammatory induction, whereby chronic inflammation sets up a constant physiological state of inflammatory cell recruitment. The secretions of these inflammatory cells can alter the genetic makeup of proliferating cells, which can in turn, promote tumor growth.This chapter also presents an in-depth analysis of molecular interactions within the TME, including secretory cytokines and exosomes. Since the exosomal cargo of a cell is a reflection and fingerprint of the originating parental cells, the profiling of exosomal miRNA derived from thyroid cancer cells and macrophages in the TME may serve as an important step in biomarker discovery. Identification of a distinct set of tumor suppressive miRNAs downregulated in ATC-secreted exosomes indicates their role in the regulation of tumor suppressive genes that may increase the metastatic propensity of ATC. Additionally, the high expression of pro-inflammatory cytokines in studies looking at thyroid cancer and activated macrophage conditioned media suggests the existence of an inflammatory TME in thyroid cancer. New findings are suggestive of the presence of a metastatic niche in ATC tissues that is influenced by thyroid tumor microenvironment secretome-induced epithelial to mesenchymal transition (EMT), mediated by a reciprocal interaction between the pro-inflammatory M1 macrophages and the thyroid cancer cells. Thus, targeting the metastatic thyroid carcinoma microenvironment could offer potential therapeutic benefits and should be explored further in preclinical and translational models of human metastatic thyroid cancer.

Tumor Properties Mediate the Relationship Between Peripheral Blood Monocytes and Tumor-Associated Macrophages in Breast Cancer

In cancer patients, circulating monocytes show functional alterations. Since monocytes are precursors of tumor-associated macrophages (TAMs), TAMs ensuring tumor viability are potentially replenished through the recruitment of monocytes with specific properties. We demonstrated that locoregional metastasis and circulating factors, such as CD45-EpCAM + CD44 + CD24-/low circulating tumor cells, and serum MCP-1 and HMGB1 were statistically associated with modulation of the monocyte features in breast cancer patients. The count of circulating CD45-EpCAM + cells correlated with CD68+, CD163 + monocyte in blood, and with density of CD68 + TAM in breast cancer tumors. Overall, the relationship between monocytes and TAMs is mediated by the tumor in breast cancer patients.

Nutrient supplements from selected botanicals mediated immune modulation of the tumor microenvironment and antitumor mechanism

Specific extracts of selected vegetables (SV) have been shown to benefit the survival of stage IIIb/IV non-small cell lung cancer patients in phase I/II studies and is currently in a phase III trial. However, the underlying mechanism of SV-mediated antitumor immune responses has not been elucidated. Our results indicate that SV modulated the NK and adoptive T cell immune responses in antitumor efficacy. Furthermore, antitumor effects of SV were also mediated by innate myeloid cell function, which requires both TLR and β-glucan signaling in a MyD88/TRIF and Dectin-1-dependent manner, respectively. Additionally, SV treatment reduced granulocytic myeloid-derived suppressor cell (MDSC) infiltration into the tumor and limited monocytic MDSC toward the M2-like functional phenotype. Importantly, SV treatment enhanced antigen-specific immune responses by augmenting the activation of antigen-specific TH1/TH17 cells in secondary lymphoid organs and proliferative response, as well as by reducing the Treg population in the tumor microenvironment, which was driven by SV-primed activated M-MDSC. Our results support the idea that SV can subvert immune-tolerance state in the tumor microenvironment and inhibit tumor growth. The present study suggests that features, such as easy accessibility, favorable clinical efficacy, no detectable side effects and satisfactory safety make SV a feasible, appealing and convincing adjuvant therapy for the treatment of cancer patients and prevent tumor recurrence and/or metastases.

circRNAs: Insight Into Their Role in Tumor-Associated Macrophages

Currently, it is well known that the tumor microenvironment not only provides energy support for tumor growth but also regulates tumor signaling pathways and promotes the proliferation, invasion, metastasis, and drug resistance of tumor cells. The tumor microenvironment, especially the function and mechanism of tumor-associated macrophages (TAMs), has attracted great attention. TAMs are the most common immune cells in the tumor microenvironment and play a vital role in the occurrence and development of tumors. circular RNA (circRNA) is a unique, widespread, and stable form of non-coding RNA (ncRNA), but little is known about the role of circRNAs in TAMs or how TAMs affect circRNAs. In this review, we summarize the specific manifestations of circRNAs that affect the tumor-associated macrophages and play a significant role in tumor progression. This review helps improve our understanding of the association between circRNAs and TAMs, thereby promoting the development and progress of potential clinical targeted therapies.

Diagnostic and prognostic value of ABC transporter family member ABCG1 gene in clear cell renal cell carcinoma

As the most common histologic subtype of renal cancer, clear cell renal cell carcinoma (ccRCC) poses a serious threat to public health. However, there are no specific molecular-targeted drugs for ccRCC at present. Human ATP-binding cassette (ABC) transporter family plays an important role in homeostasis maintenance. This study aimed to evaluate the potential diagnostic value of ABC genes in ccRCC. A total of 952 samples of ccRCC patients (707) and controls (245) from three different datasets were included for analysis. Receiver operating characteristic analysis and t-test were used to analyze the differential expression of ABC genes in ccRCC patients and control samples at mRNA level during screening and validations. The Cancer Genome Atlas (TCGA-ccRCC) dataset was utilized to investigate the correlation between ABC genes expression and prognostic value in ccRCC. We then investigated the interactions between ABCG1 and proteins in the Comparative Toxicogenomics Database (CTD). Finally, we found that ATP-binding cassette transporter G member 1 (ABCG1) was over-expressed in ccRCC patients compared with healthy samples at mRNA level. Cox regression analysis and Kaplan-Meier analysis showed that ccRCC patients with high ABCG1 expression had better overall survival (OS) than those patients with low expression (hazard ratio (HR) = 0.662, p = 0.007). This study demonstrated that ABCG1 is a potential diagnostic and prognostic biomarker in ccRCC and discussed the molecular mechanisms underlying the relationship between ccRCC and ABCG1, which might provide guidance for better management and treatment of ccRCC in the future.