CCL2-induced chemokine cascade promotes breast cancer metastasis by enhancing retention of metastasis-associated macrophages

Discovery of a CCR2-targeting pepducin therapy for chronic pain

Targeting the CCL2/CCR2 chemokine axis has been shown to be effective at relieving pain in rodent models of inflammatory and neuropathic pain, therefore representing a promising avenue for the development of non-opioid analgesics. However, clinical trials targeting this receptor for inflammatory conditions and painful neuropathies have failed to meet expectations and have all been discontinued due to lack of efficacy. To overcome the poor selectivity of CCR2 chemokine receptor antagonists, we generated and characterized the function of intracellular cell-penetrating allosteric modulators targeting CCR2, namely pepducins. In vivo, chronic intrathecal administration of the CCR2-selective pepducin PP101 was effective in alleviating neuropathic and bone cancer pain. In the setting of bone metastases, we found that T cells infiltrate dorsal root ganglia (DRG) and induce long-lasting pain hypersensitivity. By acting on CCR2-expressing DRG neurons, PP101 attenuated the altered phenotype of sensory neurons as well as the neuroinflammatory milieu of DRGs, and reduced bone cancer pain by blocking CD4+ and CD8+ T cell infiltration. Notably, PP101 demonstrated its efficacy in targeting the neuropathic component of bone cancer pain, as evidenced by its anti-nociceptive effects in a model of chronic constriction injury of the sciatic nerve. Importantly, PP101-induced reduction of CCR2 signaling in DRGs did not result in deleterious tumor progression or adverse behavioral effects. Thus, targeting neuroimmune crosstalk through allosteric inhibition of CCR2 could represent an effective and safe avenue for the management of chronic pain.

Deciphering the performance of macrophages in tumour microenvironment: a call for precision immunotherapy

Macrophages infiltrating tumour tissues or residing in the microenvironment of solid tumours are known as tumour-associated macrophages (TAMs). These specialized immune cells play crucial roles in tumour growth, angiogenesis, immune regulation, metastasis, and chemoresistance. TAMs encompass various subpopulations, primarily classified into M1 and M2 subtypes based on their differentiation and activities. M1 macrophages, characterized by a pro-inflammatory phenotype, exert anti-tumoural effects, while M2 macrophages, with an anti-inflammatory phenotype, function as protumoural regulators. These highly versatile cells respond to stimuli from tumour cells and other constituents within the tumour microenvironment (TME), such as growth factors, cytokines, chemokines, and enzymes. These stimuli induce their polarization towards one phenotype or another, leading to complex interactions with TME components and influencing both pro-tumour and anti-tumour processes.This review comprehensively and deeply covers the literature on macrophages, their origin and function as well as the intricate interplay between macrophages and the TME, influencing the dual nature of TAMs in promoting both pro- and anti-tumour processes. Moreover, the review delves into the primary pathways implicated in macrophage polarization, examining the diverse stimuli that regulate this process. These stimuli play a crucial role in shaping the phenotype and functions of macrophages. In addition, the advantages and limitations of current macrophage based clinical interventions are reviewed, including enhancing TAM phagocytosis, inducing TAM exhaustion, inhibiting TAM recruitment, and polarizing TAMs towards an M1-like phenotype. In conclusion, while the treatment strategies targeting macrophages in precision medicine show promise, overcoming several obstacles is still necessary to achieve an accessible and efficient immunotherapy.

The temporal progression of lung immune remodeling during breast cancer metastasis

Tumor metastasis requires systemic remodeling of distant organ microenvironments that impacts immune cell phenotypes, population structure, and intercellular communication. However, our understanding of immune phenotypic dynamics in the metastatic niche remains incomplete. Here, we longitudinally assayed lung immune transcriptional profiles in the polyomavirus middle T antigen (PyMT) and 4T1 metastatic breast cancer models from primary tumorigenesis, through pre-metastatic niche formation, to the final stages of metastatic outgrowth at single-cell resolution. Computational analyses of these data revealed a TLR-NFκB inflammatory program enacted by both peripherally derived and tissue-resident myeloid cells that correlated with pre-metastatic niche formation and mirrored CD14+ "activated" myeloid cells in the primary tumor. Moreover, we observed that primary tumor and metastatic niche natural killer (NK) cells are differentially regulated in mice and human patient samples, with the metastatic niche featuring elevated cytotoxic NK cell proportions. Finally, we identified cell-type-specific dynamic regulation of IGF1 and CCL6 signaling during metastatic progression that represents anti-metastatic immunotherapy candidate pathways.

Targeting tumor‑associated macrophages: Critical players in tumor progression and therapeutic strategies (Review)

Tumor‑associated macrophages (TAMs) are essential components of the tumor microenvironment (TME) and display phenotypic heterogeneity and plasticity associated with the stimulation of bioactive molecules within the TME. TAMs predominantly exhibit tumor‑promoting phenotypes involved in tumor progression, such as tumor angiogenesis, metastasis, immunosuppression and resistance to therapies. In addition, TAMs have the potential to regulate the cytotoxic elimination and phagocytosis of cancer cells and interact with other immune cells to engage in the innate and adaptive immune systems. In this context, targeting TAMs has been a popular area of research in cancer therapy, and a comprehensive understanding of the complex role of TAMs in tumor progression and exploration of macrophage‑based therapeutic approaches are essential for future therapeutics against cancers. The present review provided a comprehensive and updated overview of the function of TAMs in tumor progression, summarized recent advances in TAM‑targeting therapeutic strategies and discussed the obstacles and perspectives of TAM‑targeting therapies for cancers.

STC1 competitively binding βPIX enhances melanoma progression via YAP nuclear translocation and M2 macrophage recruitment through the YAP/CCL2/VEGFA/AKT feedback loop

This study investigates the role of Stanniocalcin-1 (STC1) in melanoma progression, with a focus on its impact on metastasis, angiogenesis, and immune evasion. Systematic bioinformatics analysis revealed the potential influence of STC1 dysregulation on prognosis, immune cell infiltration, response to immune therapy, and cellular functions. In vitro assays were conducted to assess the proliferation, invasion, migration, and angiogenesis capabilities of A375 cells. In vivo experiments utilizing C57BL/6 J mice established a lung metastasis model using B16-F10 cells to evaluate macrophage infiltration and M2 polarization. A Transwell co-culture system was employed to explore the crosstalk between melanoma and macrophages. Molecular interactions among STC1, YAP, βPIX, and CCL2 are investigated using mass spectrometry, Co-Immunoprecipitation, Dual-Luciferase Reporter Assay, and Chromatin Immunoprecipitation experiments. STC1 was found to enhance lung metastasis by promoting the recruitment and polarization of M2 macrophages, thereby fostering an immunosuppressive microenvironment. Mechanistically, STC1 competes with YAP for binding to βPIX within the KER domain in melanoma cells, leading to YAP activation and subsequent CCL2 upregulation. CCL2-induced M2 macrophages secrete VEGFA, which enhances tumor vascularization and increases STC1 expression via the AKT signaling pathway in melanoma cells, establishing a pro-metastatic feedback loop. Notably, STC1-induced YAP activation increases PD-L1 expression, promoting immune evasion. Silencing STC1 enhances the efficacy of PD-1 immune checkpoint therapy in mice. This research elucidates STC1's role in melanoma metastasis and its complex interactions with tumor-associated macrophages, proposing STC1 as a potential therapeutic target for countering melanoma metastasis and augmenting the efficacy of PD-1 immunotherapy.

Targeting CCL2/CCR2 Signaling Overcomes MEK Inhibitor Resistance in Acute Myeloid Leukemia

PURPOSE

Emerging evidence underscores the critical role of extrinsic factors within the microenvironment in protecting leukemia cells from therapeutic interventions, driving disease progression, and promoting drug resistance in acute myeloid leukemia (AML). This finding emphasizes the need for the identification of targeted therapies that inhibit intrinsic and extrinsic signaling to overcome drug resistance in AML.

EXPERIMENTAL DESIGN

We performed a comprehensive analysis utilizing a cohort of ∼300 AML patient samples. This analysis encompassed the evaluation of secreted cytokines/growth factors, gene expression, and ex vivo drug sensitivity to small molecules. Our investigation pinpointed a notable association between elevated levels of CCL2 and diminished sensitivity to the MEK inhibitors (MEKi). We validated this association through loss-of-function and pharmacologic inhibition studies. Further, we deployed global phosphoproteomics and CRISPR/Cas9 screening to identify the mechanism of CCR2-mediated MEKi resistance in AML.

RESULTS

Our multifaceted analysis unveiled that CCL2 activates multiple prosurvival pathways, including MAPK and cell-cycle regulation in MEKi-resistant cells. Employing combination strategies to simultaneously target these pathways heightened growth inhibition in AML cells. Both genetic and pharmacologic inhibition of CCR2 sensitized AML cells to trametinib, suppressing proliferation while enhancing apoptosis. These findings underscore a new role for CCL2 in MEKi resistance, offering combination therapies as an avenue to circumvent this resistance.

CONCLUSIONS

Our study demonstrates a compelling rationale for translating CCL2/CCR2 axis inhibitors in combination with MEK pathway-targeting therapies, as a potent strategy for combating drug resistance in AML. This approach has the potential to enhance the efficacy of treatments to improve AML patient outcomes.

Expression of immune-related genes and breast cancer recurrence in women with ductal carcinoma in situ

BACKGROUND AND AIM

Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive breast cancer with highly variable clinical behavior, but risk stratification is still challenging. We sought to identify immune-related gene expression signatures of pure DCIS associated with different risks of breast cancer recurrence.

METHODS

A retrospective nested case-control study of 143 pure DCIS was performed including 70 women with subsequent ipsilateral breast event (IBE, in situ or invasive; cases) and 73 DCIS women with no IBE and matched for age, tumor size, treatment, hormone receptors/HER2 status, and follow-up time (controls). RNA was extracted from DCIS samples and subjected to next-generation sequencing gene expression analysis of 395 immune-related genes. Correlations between DCIS immune-related gene expression and IBE were analyzed using weighted Cox regression for nested case-control data.

RESULTS

Eight immune-related genes were differentially expressed between cases and controls. MAGEA10 expression (present vs. absent) and high expression levels of IFNA17 and CBLB (Q4 vs. Q1) were observed more frequently in DCIS of women with subsequent IBE, mainly invasive (p-valueFDR < 0.05). Conversely, expression of IL3RA1, TAGAP, TNFAIP8, and high expression levels of CCL2 and LRP1 were associated with a lower risk of IBE (p-valueFDR < 0.05).

CONCLUSION

This exploratory analysis of pure DCIS showed significant differences in immune-related gene expression profiles between women with and with no subsequent IBE, particularly as invasive IBE. These results, after additional validation, could improve risk stratification and management of DCIS patients.

An inflammation-related subtype classification for analyzing tumor microenvironment and clinical prognosis in colorectal cancer

Background

The inflammatory response plays an essential role in the tumor microenvironment (TME) of colorectal cancer (CRC) by modulating tumor growth, progression, and response to therapy through the recruitment of immune cells, production of cytokines, and activation of signaling pathways. However, the molecular subtypes and risk score prognostic model based on inflammatory response remain to be further explored.

Methods

Inflammation-related genes were collected from the molecular signature database and molecular subtypes were identified using nonnegative matrix factorization based on the TCGA cohort. We compared the clinicopathological features, immune infiltration, somatic mutation profile, survival prognosis, and drug sensitivity between the subtypes. The risk score model was developed using LASSO and multivariate Cox regression in the TCGA cohort. The above results were independently validated in the GEO cohort. Moreover, we explored the biological functions of the hub gene, receptor interacting protein kinase 2 (RIPK2), leveraging proteomics data, in vivo, and in vitro experiments.

Results

We identified two inflammation-related subtypes (inflammation-low and inflammation-high) and have excellent internal consistency and stability. Inflammation-high subtype showed higher immune cell infiltration and increased sensitivity to common chemotherapeutic drugs, while inflammation-low subtype may be more suitable for immunotherapy. Besides, the two subtypes differ significantly in pathway enrichment and biological functions. In addition, the 11-gene signature prognostic model constructed from inflammation-related genes showed strong prognostic assessment power and could serve as a novel prognostic marker to predict the survival of CRC patients. Finally, RIPK2 plays a crucial role in promoting malignant proliferation of CRC cell validated by experiment.

Conclusions

This study provides new insights into the heterogeneity of CRC and provides novel opportunities for treatment development and clinical decision making.

Downregulation of IRF8 in alveolar macrophages by G-CSF promotes metastatic tumor progression

Tissue-resident macrophages (TRMs) are abundant immune cells within pre-metastatic sites, yet their functional contributions to metastasis remain incompletely understood. Here, we show that alveolar macrophages (AMs), the main TRMs of the lung, are susceptible to downregulation of the immune stimulatory transcription factor IRF8, impairing anti-metastatic activity in models of metastatic breast cancer. G-CSF is a key tumor-associated factor (TAF) that acts upon AMs to reduce IRF8 levels and facilitate metastasis. Translational relevance of IRF8 downregulation was observed among macrophage precursors in breast cancer and a CD68hiIRF8loG-CSFhi gene signature suggests poorer prognosis in triple-negative breast cancer (TNBC), a G-CSF-expressing subtype. Our data highlight the underappreciated, pro-metastatic roles of AMs in response to G-CSF and identify the contribution of IRF8-deficient AMs to metastatic burden. AMs are an attractive target of local neoadjuvant G-CSF blockade to recover anti-metastatic activity.

Multiple influence of immune cells in the bone metastatic cancer microenvironment on tumors

Bone is a common organ for solid tumor metastasis. Malignant bone tumor becomes insensitive to systemic therapy after colonization, followed by poor prognosis and high relapse rate. Immune and bone cells in situ constitute a unique immune microenvironment, which plays a crucial role in the context of bone metastasis. This review firstly focuses on lymphatic cells in bone metastatic cancer, including their function in tumor dissemination, invasion, growth and possible cytotoxicity-induced eradication. Subsequently, we examine myeloid cells, namely macrophages, myeloid-derived suppressor cells, dendritic cells, and megakaryocytes, evaluating their interaction with cytotoxic T lymphocytes and contribution to bone metastasis. As important components of skeletal tissue, osteoclasts and osteoblasts derived from bone marrow stromal cells, engaging in 'vicious cycle' accelerate osteolytic bone metastasis. We also explain the concept tumor dormancy and investigate underlying role of immune microenvironment on it. Additionally, a thorough review of emerging treatments for bone metastatic malignancy in clinical research, especially immunotherapy, is presented, indicating current challenges and opportunities in research and development of bone metastasis therapies.

Update on current and new potential immunotherapies in breast cancer, from bench to bedside

Impressive advances have been seen in cancer immunotherapy during the last years. Although breast cancer (BC) has been long considered as non-immunogenic, immunotherapy for the treatment of BC is now emerging as a new promising therapeutic approach with considerable potential. This is supported by a plethora of completed and ongoing preclinical and clinical studies in various types of immunotherapies. However, a significant gap between clinical oncology and basic cancer research impairs the understanding of cancer immunology and immunotherapy, hampering cancer therapy research and development. To exploit the accumulating available data in an optimal way, both fundamental mechanisms at play in BC immunotherapy and its clinical pitfalls must be integrated. Then, clinical trials must be critically designed with appropriate combinations of conventional and immunotherapeutic strategies. While there is room for major improvement, this updated review details the immunotherapeutic tools available to date, from bench to bedside, in the hope that this will lead to rethinking and optimizing standards of care for BC patients.

Phenotypic Heterogeneity, Bidirectionality, Universal Cues, Plasticity, Mechanics, and the Tumor Microenvironment Drive Cancer Metastasis

Tumor diseases become a huge problem when they embark on a path that advances to malignancy, such as the process of metastasis. Cancer metastasis has been thoroughly investigated from a biological perspective in the past, whereas it has still been less explored from a physical perspective. Until now, the intraluminal pathway of cancer metastasis has received the most attention, while the interaction of cancer cells with macrophages has received little attention. Apart from the biochemical characteristics, tumor treatments also rely on the tumor microenvironment, which is recognized to be immunosuppressive and, as has recently been found, mechanically stimulates cancer cells and thus alters their functions. The review article highlights the interaction of cancer cells with other cells in the vascular metastatic route and discusses the impact of this intercellular interplay on the mechanical characteristics and subsequently on the functionality of cancer cells. For instance, macrophages can guide cancer cells on their intravascular route of cancer metastasis, whereby they can help to circumvent the adverse conditions within blood or lymphatic vessels. Macrophages induce microchannel tunneling that can possibly avoid mechanical forces during extra- and intravasation and reduce the forces within the vascular lumen due to vascular flow. The review article highlights the vascular route of cancer metastasis and discusses the key players in this traditional route. Moreover, the effects of flows during the process of metastasis are presented, and the effects of the microenvironment, such as mechanical influences, are characterized. Finally, the increased knowledge of cancer metastasis opens up new perspectives for cancer treatment.

Pivotal role of myeloid-derived suppressor cells in infection-related tumor growth

BACKGROUND

In this study, we investigated infection-related tumor growth, focusing on myeloid-derived suppressor cells (MDSCs) in clinical and experimental settings.

PATIENTS AND METHODS

In the clinical study, a total 109 patients who underwent gastrectomy or esophagectomy were included. Blood samples were collected from a preoperative time point through 3 months after surgery, and MDSCs were analyzed using flow cytometry. In animal experiments, peritonitis model mice were created by CLP method. We investigated the number of splenic MDSCs in these mice using flow cytometry. Malignant melanoma cells (B16F10) were inoculated on the back of the mice, and tumor growth was monitored. We compared the level of MDSC infiltration around the tumor and the migration ability between CLP and sham-operated mice-derived MDSCs. Finally, we focused on PD-L1+ MDSCs to examine the effectiveness of anti-PD-L1 antibodies on tumor growth in CLP mice.

RESULTS

In patients with postoperative infectious complication, MDSC number was found to remain elevated 3 months after surgery, when the inflammatory responses were normalized. CLP mice showed increased numbers of MDSCs, and following inoculation with B16F10 cells, this higher number of MDSCs was associated with significant tumor growth. CLP-mice-derived MDSCs had higher levels of accumulation around the tumor and had more enhanced migration ability. Finally, CLP mice had increased numbers of PD-L1+ MDSCs and showed more effective inhibition of tumor growth by anti-PD-L1 antibodies compared to sham-operated mice.

CONCLUSION

Long-lasting enhanced MDSCs associated with infection may contribute to infection-related tumor progression.

Loss of NAT10 disrupts enhancer organization via p300 mislocalization and suppresses transcription of genes necessary for metastasis progression

Acetylation of protein and RNA represent a critical event for development and cancer progression. NAT10 is the only known RNA acetylase that catalyzes the N4-actylcytidine (ac4C) modification of RNAs. Here, we show that the loss of NAT10 significantly decreases lung metastasis in allograft and genetically engineered mouse models of breast cancer. NAT10 interacts with a mechanosensitive, metastasis susceptibility protein complex at the nuclear pore. In addition to its canonical role in RNA acetylation, we find that NAT10 interacts with p300 at gene enhancers. NAT10 loss is associated with p300 mislocalization into heterochromatin regions. NAT10 depletion disrupts enhancer organization, leading to alteration of gene transcription necessary for metastatic progression, including reduced myeloid cell-recruiting chemokines that results in a less metastasis-prone tumor microenvironment. Our study uncovers a distinct role of NAT10 in enhancer organization of metastatic tumor cells and suggests its involvement in the tumor-immune crosstalk dictating metastatic outcomes.

Spatial and Temporal Mapping of Breast Cancer Lung Metastases Identify TREM2 Macrophages as Regulators of the Metastatic Boundary

Cancer mortality primarily stems from metastatic recurrence, emphasizing the urgent need for developing effective metastasis-targeted immunotherapies. To better understand the cellular and molecular events shaping metastatic niches, we used a spontaneous breast cancer lung metastasis model to create a single-cell atlas spanning different metastatic stages and regions. We found that premetastatic lungs are infiltrated by inflammatory neutrophils and monocytes, followed by the accumulation of suppressive macrophages with the emergence of metastases. Spatial profiling revealed that metastasis-associated immune cells were present in the metastasis core, with the exception of TREM2+ regulatory macrophages uniquely enriched at the metastatic invasive margin, consistent across both murine models and human patient samples. These regulatory macrophages (Mreg) contribute to the formation of an immune-suppressive niche, cloaking tumor cells from immune surveillance. Our study provides a compendium of immune cell dynamics across metastatic stages and niches, informing the development of metastasis-targeting immunotherapies.

SIGNIFICANCE

Temporal and spatial single-cell analysis of metastasis stages revealed new players in modulating immune surveillance and suppression. Our study highlights distinct populations of TREM2 macrophages as modulators of the microenvironment in metastasis, and as the key immune determinant defining metastatic niches, pointing to myeloid checkpoints to improve therapeutic strategies. This article is featured in Selected Articles from This Issue, p. 2489.

Recent advancements in nanomedicine based lipid metabolism for tumour immunotherapy

Therapy on lipid metabolism is emerging as a groundbreaking cancer treatment, offering the unprecedented opportunity to effectively treat and in several cases. Tumorigenesis is inextricably linked to lipid metabolism. In this regard, the features of lipid metabolism include lipid synthesis, decomposition, metabolism and lipid storage and mobilisation from intracellular lipid droplets. Most importantly, the regulation of lipid metabolism is central to the appropriate immune response of tumour cells, and ultimately to exert the immune efforts to realise the perspective of many anti-tumour effects. Different cancers and immune cells have different dependence on lipid metabolism, playing a pivotal role in differentiation and function of immune cells. However, what lies before the immunotherapy targeting lipid metabolism is side effects of systemic toxicity and defects of individual drugs, which strongly highlights that nanodelivery strategy is a magnet for it to enhance drug efficiency, reduce drug toxicity and improve application deficiencies. This review will first focus on emerging research progress of lipid metabolic reprogramming mechanism, and then explore the complex role of lipid metabolism in the tumour cells including the effect on immune cells and their nano-preparations of monotherapy and multiple therapies used in combination, in a shift away from conventional cancer research.HighlightsThe regulation of lipid metabolism is central to the appropriate immune response of tumour cells, and ultimately to exert the immune efforts to realise the perspective of many anti-tumour effects.Preparations of focusing lipid metabolism have side effects of systemic toxicity and defects of individual drugs. It strongly highlights that nanodelivery strategy is a magnet for it to enhance drug efficiency, reduce drug toxicity and improve application deficiencies.This review will first focus on emerging research progress of lipid metabolic reprogramming mechanism, and then explore the complex role of lipid metabolism in the tumour cells including the effect on immune cells as well as their nano-preparations of monotherapy and multiple therapies used in combination, in a shift away from conventional cancer research.

SCEL regulates switches between pro-survival and apoptosis of the TNF-α/TNFR1/NF-κB/c-FLIP axis to control lung colonization of triple negative breast cancer

BACKGROUND

Patients with metastatic triple-negative breast cancer (mTNBC) have a higher probability of developing visceral metastasis within 5 years after the initial diagnosis. Therefore, a deeper understanding of the progression and spread of mTNBC is urgently needed.

METHODS

The isobaric tag for relative and absolute quantitation (iTRAQ)-based LC-MS/MS proteomic approach was applied to identify novel membrane-associated proteins in the lung-tropic metastatic cells. Public domain datasets were used to assess the clinical relevance of the candidate proteins. Cell-based and mouse models were used for biochemical and functional characterization of the protein molecule Sciellin (SCEL) identified by iTRAQ to elucidate its role and underlying mechanism in promoting lung colonization of TNBC cells.

RESULTS

The iTRAQ-based LC-MS/MS proteomic approach identified a membrane-associated protein SCEL that was overexpressed in the lung-tropic metastatic cells, and its high expression was significantly correlated with the late-stage TNBC and the shorter survival of the patients. Downregulation of SCEL expression significantly impaired the 3D colony-forming ability but not the migration and invasion ability of the lung colonization (LC) cells. Knockdown of SCEL reduced TNF-α-induced activation of the NF-κB/c-FLIP pro-survival and Akt/Erk1/2 growth signaling pathways in the LC cells. Specifically, knockdown of SCEL expression switched TNF-α-mediated cell survival to the caspase 3-dependent apoptosis. Conversely, ectopic expression of SCEL promoted TNF-α-induced activation of NF-κB/c-FLIP pro-survival and Akt/Erk1/2 pro-growth signaling pathway. The result of co-immunoprecipitation (Co-IP) and GST pull-down assay showed that SCEL could interact with TNFR1 to promote its protein stability. The xenograft mouse model experiments revealed that knockdown of SCEL resulted in increase of caspase-3 activity, and decrease of ki67 and TNFR1 expression as well as increase of tumor-associated macrophages in the metastatic lung lesions. Clinically, SCEL expression was found to be positively correlated with TNFR1 in TNBC tissues. Lastly, we showed that blocking TNF-α-mediated cell survival signaling by adalimumab effectively suppressed the lung colonization of the SCEL-positive, but not the SCEL-downregulated LC cells in the tail-vein injection model.

CONCLUSIONS

Our findings indicate that SCEL plays an essential role in the metastatic lung colonization of TNBC by promoting the TNF-α/TNFR1/NF-κB/c-FLIP survival and Akt/Erk1/2 proliferation signaling. Thus, SCEL may serve as a biomarker for adalimumab treatment of TNBC patients.

Reverse Onco-Cardiology: What Is the Evidence for Breast Cancer? A Systematic Review of the Literature

Breast cancer and cardiovascular diseases (CVD) represent significant global health challenges, with CVD being the leading cause of mortality and breast cancer, showing a complex pattern of incidence and mortality. We explore the intricate interplay between these two seemingly distinct medical conditions, shedding light on their shared risk factors and potential pathophysiological connections. A specific connection between hypertension (HTN), atrial fibrillation (AF), myocardial infarction (MI), and breast cancer was evaluated. HTN is explored in detail, emphasizing the role of aging, menopause, insulin resistance, and obesity as common factors linking HTN and breast cancer. Moreover, an attempt is made to identify the potential impact of antihypertensive medications and highlight the increased risk of breast cancer among those women, with a focus on potential mechanisms. A summary of key findings underscores the need for a multisystem approach to understanding the relationship between CVD and breast cancer is also explored with a highlight for all the gaps in current research, such as the lack of clinical observational data on MI and breast cancer in humans and the need for studies specifically designed for breast cancer. This paper concludes that there should be a focus on potential clinical applications of further investigation in this field, including personalized prevention and screening strategies for women at risk. Overall, the authors attempt to provide a comprehensive overview of the intricate connections between breast cancer and cardiovascular diseases, emphasizing the importance of further research in this evolving field of cardio-oncology.

Honokiol prevents lung metastasis of triple-negative breast cancer by regulating polarization and recruitment of macrophages

Metastasis is the leading cause of breast cancer-associated death. Lung metastasis commonly occurs in triple-negative breast cancer (TNBC) metastasis, worsening the TNBC prognosis. Considering their role in tumor progression and metastasis, tumor-associated macrophages (TAMs) are essential therapeutic targets in cancer therapy. Previous studies have demonstrated that honokiol inhibits tumor growth and progression. Here we assessed how honokiol inhibits lung metastasis of TNBC by regulating the polarization of macrophages. We found that honokiol decreased the expression of IL-13-triggered M2 markers like CD206, Arg1, and CCL2, preventing the invasion and migration ability of TNBC cells. The activation of signal transducer and activator of transcription STAT6 and STAT3 was significantly suppressed by honokiol in M2 polarized macrophages. Meanwhile, honokiol increased the expression of LPS/IFNγ-induced M1 markers such as CD11c, iNOS, and IL12 by promoting STAT1 phosphorylation. Besides, honokiol decreased both the ratio of M2/M1 macrophages and the expression of the IL-10/IL-12 gene in lung tissues, thereby inhibiting the proliferation and metastasis of murine breast cancer. Moreover, honokiol reduced the infiltration of macrophages to the lung tissue through the CCL2/CCR2 pathways. These results highlight the potential of honokiol in suppressing TNBC tumor progression and lung metastasis by regulating the polarization and recruitment of macrophages.

The cross-talk between macrophages and tumor cells as a target for cancer treatment

Macrophages represent an important component of the innate immune system. Under physiological conditions, macrophages, which are essential phagocytes, maintain a proinflammatory response and repair damaged tissue. However, these processes are often impaired upon tumorigenesis, in which tumor-associated macrophages (TAMs) protect and support the growth, proliferation, and invasion of tumor cells and promote suppression of antitumor immunity. TAM abundance is closely associated with poor outcome of cancer, with impediment of chemotherapy effectiveness and ultimately a dismal therapy response and inferior overall survival. Thus, cross-talk between cancer cells and TAMs is an important target for immune checkpoint therapies and metabolic interventions, spurring interest in it as a therapeutic vulnerability for both hematological cancers and solid tumors. Furthermore, targeting of this cross-talk has emerged as a promising strategy for cancer treatment with the antibody against CD47 protein, a critical macrophage checkpoint recognized as the "don't eat me" signal, as well as other metabolism-focused strategies. Therapies targeting CD47 constitute an important milestone in the advancement of anticancer research and have had promising effects on not only phagocytosis activation but also innate and adaptive immune system activation, effectively counteracting tumor cells' evasion of therapy as shown in the context of myeloid cancers. Targeting of CD47 signaling is only one of several possibilities to reverse the immunosuppressive and tumor-protective tumor environment with the aim of enhancing the antitumor response. Several preclinical studies identified signaling pathways that regulate the recruitment, polarization, or metabolism of TAMs. In this review, we summarize the current understanding of the role of macrophages in cancer progression and the mechanisms by which they communicate with tumor cells. Additionally, we dissect various therapeutic strategies developed to target macrophage-tumor cell cross-talk, including modulation of macrophage polarization, blockade of signaling pathways, and disruption of physical interactions between leukemia cells and macrophages. Finally, we highlight the challenges associated with tumor hypoxia and acidosis as barriers to effective cancer therapy and discuss opportunities for future research in this field.

A randomized trial evaluating the association between related gene polymorphism and nausea and vomiting induced by cisplatin multi-day chemotherapy

PURPOSE

We aim to investigate the correlation between gene polymorphisms and cisplatin chemotherapy-induced nausea and vomiting (CINV), which was prevented by olanzapine or aprepitant triple antiemetic regimen.

METHODS

Before chemotherapy, the blood samples of 89 malignant tumor patients who received multi-day chemotherapy with cisplatin were collected for sequencing and typing. As there were duplicate patients enrolled in different chemotherapy cycles, there were a total of 190 cases. The patients were divided into two groups randomly, who received the triple antiemetic regimen of olanzapine or aprepitant combined with 5-HT3RA and dexamethasone. The main evaluation indicators were the total protection (TP) rate in the acute phase (0-24 h), the delayed phase (25-120 h) and the overall phase (0-120 h).

RESULTS

Univariate analysis was performed on genetic loci that reached H-W balance with TP. In the olanzapine group, increased TP in the acute phase was associated with HTR3A rs1176719 non-GG (P < 0.05) genotype etc. Increased TP in the delayed phase was associated with HTR3A rs1176719 non-GG (P < 0.05) genotype etc. In the aprepitant group, increased TP in the acute phase was associated with the MTHFR rs1801131 TT (P < 0.05) genotype etc. Increased TP in the delayed phase was associated with HTR3A rs1062613 CC (P < 0.05) genetype ect. Multivariate Logistic regression analysis showed that HTR3B rs7943062GG (P < 0.05) genotype etc. were correlated with increased TP in the delayed phase. MTHFR rs1801131TT genotype was associated with increased TP in the acute phase (P < 0.05) and delayed phase (P < 0.05).

CONCLUSION

This study found that gene polymorphisms, including HTR3B (rs1062613, rs1176719, rs2276303), HTR3B (rs45460698, rs7943062), HTR3C (rs6766410), ERCC1 (rs3212986), ERCC4 (rs744154) and MTHFR(rs1801131), may be independent prognostic factors for CINV.

Reconstructing disease dynamics for mechanistic insights and clinical benefit

Diseases change over time, both phenotypically and in their underlying molecular processes. Though understanding disease progression dynamics is critical for diagnostics and treatment, capturing these dynamics is difficult due to their complexity and the high heterogeneity in disease development between individuals. We present TimeAx, an algorithm which builds a comparative framework for capturing disease dynamics using high-dimensional, short time-series data. We demonstrate the utility of TimeAx by studying disease progression dynamics for multiple diseases and data types. Notably, for urothelial bladder cancer tumorigenesis, we identify a stromal pro-invasion point on the disease progression axis, characterized by massive immune cell infiltration to the tumor microenvironment and increased mortality. Moreover, the continuous TimeAx model differentiates between early and late tumors within the same tumor subtype, uncovering molecular transitions and potential targetable pathways. Overall, we present a powerful approach for studying disease progression dynamics-providing improved molecular interpretability and clinical benefits for patient stratification and outcome prediction.

Subverted macrophages in the triple-negative breast cancer ecosystem

Tumor-associated macrophages (TAMs) are the most critical effector cells of innate immunity and the most abundant tumor-infiltrating immune cells. They play a key role in the clearance of apoptotic bodies, regulation of inflammation, and tissue repair to maintain homeostasis in vivo. With the progression of triple-negative breast cancer（TNBC）, TAMs are "subverted" from tumor-promoting immune cells to tumor-promoting immune suppressor cells, which play a significant role in tumor development and are considered potential targets for cancer therapy. Here, we explored how macrophages, as the most important part of the TNBC ecosystem, are "subverted" to drive cancer evolution and the uniqueness of TAMs in TNBC progression and metastasis. Similarly, we discuss the rationale and available evidence for TAMs as potential targets for TNBC therapy.

Chronic pulmonary bacterial infection facilitates breast cancer lung metastasis by recruiting tumor-promoting MHCIIhi neutrophils

Breast cancer can metastasize to various organs, including the lungs. The immune microenvironment of the organs to be metastasized plays a crucial role in the metastasis of breast cancer. Infection with pathogens such as viruses and bacteria can alter the immune status of the lung. However, the effect of chronic inflammation caused by bacteria on the formation of a premetastatic niche within the lung is unclear, and the contribution of specific immune mediators to tumor metastasis also remains largely undetermined. Here, we used a mouse model revealing that chronic pulmonary bacterial infection augmented breast cancer lung metastasis by recruiting a distinct subtype of tumor-infiltrating MHCIIhi neutrophils into the lung, which exhibit cancer-promoting properties. Functionally, MHCIIhi neutrophils enhanced the lung metastasis of breast cancer in a cell-intrinsic manner. Furthermore, we identified CCL2 from lung tissues as an important environmental signal to recruit and maintain MHCIIhi neutrophils. Our findings clearly link bacterial-immune crosstalk to breast cancer lung metastasis and define MHCIIhi neutrophils as the principal mediator between chronic infection and tumor metastasis.

Effect of tumor-associated macrophages on the pyroptosis of breast cancer tumor cells

Macrophages are immune cells with high plasticity that are widely distributed in all tissues and organs of the body. Under the influence of the immune microenvironment of breast tumors, macrophages differentiate into various germline lineages. They exert pro-tumor or tumor-suppressive effects by secreting various cytokines. Pyroptosis is mediated by Gasdermin family proteins, which form holes in cell membranes and cause a violent inflammatory response and cell death. This is an important way for the body to fight off infections. Tumor cell pyroptosis can activate anti-tumor immunity and inhibit tumor growth. At the same time, it releases inflammatory mediators and recruits tumor-associated macrophages (TAMs) for accumulation. Macrophages act as "mediators" of cytokine interactions and indirectly influence the pyroptosis pathway. This paper describes the mechanism of action on the part of TAM in affecting the pyroptosis process of breast tumor cells, as well as its key role in the tumor microenvironment. Additionally, it provides the basis for in-depth research on how to use immune cells to affect breast tumors and guide anti-tumor trends, with important implications for the prevention and treatment of breast tumors. Video Abstract.

In Vitro 3D Spheroid Model Preserves Tumor Microenvironment of Hot and Cold Breast Cancer Subtypes

Dynamic interaction of cancer, immune, and stromal cells with extracellular matrix components modulates and resists the response of standard care therapies. To mimic this, an in vitro 3D spheroid model is designed using liquid overlay method to simulate hot (MDA-MB-231) and cold (MCF-7) breast tumor microenvironment (TME). This study shows increased mesenchymal phenotype, stemness, and suppressive microenvironment in MDA-MB-231-spheroids upon exposure to doxorubicin. Intriguingly, the presence of human dermal fibroblasts enhances cancer-associated fibroblast phenotype in MDA-MB-231-spheroids through increased expression of CXCL12 and FSP-1, leading to higher infiltration of immune cells (THP-1 monocytes). However, a suppressive TME is observed in both subtypes, as seen by upregulation of M2-macrophage-specific CD68 and CD206 markers. Specifically, increased PDL-1 expressing tumor-associated macrophages along with FoxP3 expressing T regulatory cells are found in MDA-MB-231-spheroids when cultured with peripheral blood mononuclear cells. Further, it is found that the addition of 1-methyl-tryptophan, a potent indoleamine-2,3-dioxygenase-1 inhibitor, subsides the suppressive phenotype by decreasing the M2 polarization via downregulation of tryptophan metabolism and IL10 expression, particularly in MCF-7 triculture spheroids. Thus, the in vitro 3D spheroid model of TME can be utilized in therapeutics to validate immunomodulatory drugs for various breast cancer subtypes.

MCP-1 expression in breast cancer and its association with distant relapse

BACKGROUND

Distant relapse of breast cancer complicates management of the disease and accounts for 90% of breast cancer-related deaths. Monocyte chemoattractant protein-1 (MCP-1) has critical roles in breast cancer progression and is widely accepted as a pro-metastatic chemokine.

METHODS

This study explored MCP-1 expression in the primary tumour of 251 breast cancer patients. A simplified 'histoscore' was used to determine if each tumour had high or low expression of MCP-1. Patient breast cancers were retrospectively staged based on available patient data. p < 0.05 was used to determine significance and changes in hazard ratios between models were considered.

RESULTS

Low MCP-1 expression in the primary tumour was associated with breast cancer-related death with distant relapse in ER- breast cancers (p < 0.01); however, this was likely a result of most low MCP-1-expressing ER- breast cancers being Stage III or Stage IV, with high MCP-1 expression in the primary tumour significantly correlated with Stage I breast cancers (p < 0.05). Expression of MCP-1 in the primary ER- tumours varied across Stage I, II, III and IV and we highlighted a switch in MCP-1 expression from high in Stage I ER- cancers to low in Stage IV ER- cancers.

CONCLUSION

This study has emphasised a critical need for further investigation into MCP-1's role in breast cancer progression and improved characterisation of MCP-1 in breast cancers, particularly in light of the development of anti-MCP-1, anti-metastatic therapies.

Liver metastasis from colorectal cancer: pathogenetic development, immune landscape of the tumour microenvironment and therapeutic approaches

Colorectal cancer liver metastasis (CRLM) is one of the leading causes of death among patients with colorectal cancer (CRC). Although immunotherapy has demonstrated encouraging outcomes in CRC, its benefits are minimal in CRLM. The complex immune landscape of the hepatic tumour microenvironment is essential for the development of a premetastatic niche and for the colonisation and metastasis of CRC cells; thus, an in-depth understanding of these mechanisms can provide effective immunotherapeutic targets for CRLM. This review summarises recent studies on the immune landscape of the tumour microenvironment of CRLM and highlights therapeutic prospects for targeting the suppressive immune microenvironment of CRLM.

Macrophage-Based Therapeutic Strategies in Hematologic Malignancies

Macrophages are types of immune cells, with ambivalent functions in tumor growth, which depend on the specific environment in which they reside. Tumor-associated macrophages (TAMs) are a diverse population of immunosuppressive myeloid cells that play significant roles in several malignancies. TAM infiltration in malignancies has been linked to a poor prognosis and limited response to treatments, including those using checkpoint inhibitors. Understanding the precise mechanisms through which macrophages contribute to tumor growth is an active area of research as targeting these cells may offer potential therapeutic approaches for cancer treatment. Numerous investigations have focused on anti-TAM-based methods that try to eliminate, rewire, or target the functional mediators released by these cells. Considering the importance of these strategies in the reversion of tumor resistance to conventional therapies and immune modulatory vaccination could be an appealing approach for the immunosuppressive targeting of myeloid cells in the tumor microenvironment (TME). The combination of reprogramming and TAM depletion is a special feature of this approach compared to other clinical strategies. Thus, the present review aims to comprehensively overview the pleiotropic activities of TAMs and their involvement in various stages of cancer development as a potent drug target, with a focus on hematologic tumors.

[Exploration of the Perturbation of PKIG in Lung Squamous Cell Carcinoma and the Role in Tumor Microenvironment Based on Bioinformatics Method]

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide, and patients have limited survival benefits from traditional treatments such as surgery, radiotherapy and chemotherapy. As a new treatment for lung cancer, immunotherapy has significantly prolonged the overall survival (OS) of patients. However, only some patients can benefit from it. We need to explore immunotherapy biomarkers more deeply to screen for advantages.

METHODS

The original data were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database, and the immunological and prognostic genes of lung squamous cell carcinoma (LUSC) were screened using R software and TIMER database. The expression of target genes was studied in TCGA and GEO databases, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and correlation analysis with tumor immune characteristics were performed by R software and TISIDB database.

RESULTS

We screened out a gene related to immunity and prognosis, cAMP dependent protein kinase inhibitor γ (PKIG), which is significantly differentially expressed in LUSC and normal tissues, and has important reference value for the diagnosis and prognosis assessment of LUSC. PKIG differential genes are mainly concentrated in the regulation of humoral immune response and other processes. The expression of PKIG was positively correlated with the infiltration level of regulatory T cells (Tregs) (r=0.340, P<0.001). In addition, the expression level of PKIG was positively correlated with the expression of chemokines/chemokine receptors such as chemokine C-C motif ligand 2 (CCL2) (r=0.503, P<0.001), CXC chemokine ligand 12 (CXCL12) (r=0.386, P<0.001) and CXC-chemokine receptor 4 (CXCR4) (r=0.492, P<0.001), and immunoinhibitors such as programmed cell death protein 1 (PDCD1) (r=0.359, P<0.001), cytotoxic T-lymphocyte associated antigen 4 (CTLA4) (r=0.375, P<0.001) and T cell immunoglobulin and ITIM domains (TIGIT) (r=0.305, P<0.001) in LUSC.

CONCLUSIONS

The immunological and prognostic gene PKIG in lung squamous cell carcinoma was screened through bioinformatics analysis. PKIG is highly correlated with LUSC prognosis and immune microenvironment, and is expected to be a potential biomolecular marker for LUSC immunotherapy.

Benzophenone-3 exposure alters composition of tumor infiltrating immune cells and increases lung seeding of 4T1 breast cancer cells

Environmental chemicals are a persistent and pervasive part of everyday life. A subset of environmental chemicals are xenoestrogens, compounds that bind to the estrogen receptor (ER) and drive estrogen-related processes. One such chemical, benzophenone-3 (BP3), is a common chemical in sunscreen. It is a potent UV protectant but also is quickly absorbed through the skin. While it has been approved by the FDA, there is a renewed interest in the safety of BP3, particularly in relation to breast cancer. The focus of this study was to examine the impact that BP3 has on triple negative breast cancer (TNBC) through alterations to cells in the immune microenvironment. In this study, we exposed female mice to one of two doses of BP3 before injecting them with a TNBC cell line. Several immune endpoints were examined both in the primary tissues and from in vitro studies of T cell behavior. Our studies revealed that in the lung tumor microenvironment, exposure to BP3 not only increased the number of metastases, but also the total area of tumor coverage. We also found that BP3 caused alterations in immune populations in a tissue-dependent manner, particularly in T cells. Taken together, our data suggest that while BP3 may not directly affect the proliferation of TNBC, growth and metastasis of TNBC-derived tumors can be altered by BP3 exposures via the alterations in the immune populations of the tumor microenvironment.

FGF19/FGFR4-mediated elevation of ETV4 facilitates hepatocellular carcinoma metastasis by upregulating PD-L1 and CCL2

BACKGROUND & AIMS

Metastasis remains the major reason for the high mortality of patients with hepatocellular carcinoma (HCC). This study was designed to investigate the role of E-twenty-six-specific sequence variant 4 (ETV4) in promoting HCC metastasis and to explore a new combination therapy strategy for ETV4-mediated HCC metastasis.

METHODS

PLC/PRF/5, MHCC97H, Hepa1-6, and H22 cells were used to establish orthotopic HCC models. Clodronate liposomes were used to clear macrophages in C57BL/6 mice. Gr-1 monoclonal antibody was used to clear myeloid-derived suppressor cells (MDSCs) in C57BL/6 mice. Flow cytometry and immunofluorescence were used to detect the changes of key immune cells in the tumour microenvironment.

RESULTS

ETV4 expression was positively related to higher tumour-node-metastasis (TNM) stage, poor tumour differentiation, microvascular invasion, and poor prognosis in human HCC. Overexpression of ETV4 in HCC cells transactivated PD-L1 and CCL2 expression, which increased tumour-associated macrophage (TAM) and MDSC infiltration and inhibited CD8+ T-cell accumulation. Knockdown of CCL2 by lentivirus or CCR2 inhibitor CCX872 treatment impaired ETV4-induced TAM and MDSC infiltration and HCC metastasis. Furthermore, FGF19/FGFR4 and HGF/c-MET jointly upregulated ETV4 expression through the ERK1/2 pathway. Additionally, ETV4 upregulated FGFR4 expression, and downregulation of FGFR4 decreased ETV4-enhanced HCC metastasis, which created a FGF19-ETV4-FGFR4 positive feedback loop. Finally, anti-PD-L1 combined with FGFR4 inhibitor BLU-554 or MAPK inhibitor trametinib prominently inhibited FGF19-ETV4 signalling-induced HCC metastasis.

CONCLUSIONS

ETV4 is a prognostic biomarker, and anti-PD-L1 combined with FGFR4 inhibitor BLU-554 or MAPK inhibitor trametinib may be effective strategies to inhibit HCC metastasis.

IMPACT AND IMPLICATIONS

Here, we reported that ETV4 increased PD-L1 and chemokine CCL2 expression in HCC cells, which resulted in TAM and MDSC accumulation and CD8+ T-cell inhibition to facilitate HCC metastasis. More importantly, we found that anti-PD-L1 combined with FGFR4 inhibitor BLU-554 or MAPK inhibitor trametinib markedly inhibited FGF19-ETV4 signalling-mediated HCC metastasis. This preclinical study will provide a theoretical basis for the development of new combination immunotherapy strategies for patients with HCC.

Tumor-Associated Macrophages in Multiple Myeloma: Key Role in Disease Biology and Potential Therapeutic Implications

Multiple myeloma (MM) is characterized by multiple relapse and, despite the introduction of novel therapies, the disease becomes ultimately drug-resistant. The tumor microenvironment (TME) within the bone marrow niche includes dendritic cells, T-cytotoxic, T-helper, reactive B-lymphoid cells and macrophages, with a complex cross-talk between these cells and the MM tumor cells. Tumor-associated macrophages (TAM) have an important role in the MM pathogenesis, since they could promote plasma cells proliferation and angiogenesis, further supporting MM immune evasion and progression. TAM are polarized towards M1 (classically activated, antitumor activity) and M2 (alternatively activated, pro-tumor activity) subtypes. Many studies demonstrated a correlation between TAM, disease progression, drug-resistance and reduced survival in lymphoproliferative neoplasms, including MM. MM plasma cells in vitro could favor an M2 TAM polarization. Moreover, a possible correlation between the pro-tumor effect of M2 TAM and a reduced sensitivity to proteasome inhibitors and immunomodulatory drugs was hypothesized. Several clinical studies confirmed CD68/CD163 double-positive M2 TAM were associated with increased microvessel density, chemoresistance and reduced survival, independently of the MM stage. This review provided an overview of the biology and clinical relevance of TAM in MM, as well as a comprehensive evaluation of a potential TAM-targeted immunotherapy.

Monocytes in Tumorigenesis and Tumor Immunotherapy

Monocytes are highly plastic innate immune cells that display significant heterogeneity during homeostasis, inflammation, and tumorigenesis. Tumor-induced systemic and local microenvironmental changes influence the phenotype, differentiation, and distribution of monocytes. Meanwhile, monocytes and their related cell subsets perform an important regulatory role in the development of many cancers by affecting tumor growth or metastasis. Thanks to recent advances in single-cell technologies, the nature of monocyte heterogeneity and subset-specific functions have become increasingly clear, making it possible to systematically analyze subset-specific roles of monocytes in tumorigenesis. In this review, we discuss recent discoveries related to monocytes and tumorigenesis, and new strategies for tumor biomarker identification and anti-tumor immunotherapy.

Targeting tumor-derived exosome-mediated premetastatic niche formation: The metastasis-preventive value of traditional Chinese medicine

Tumor-derived exosome (TDE)-mediated premetastatic niche (PMN) formation is a potential mechanism underlying the organotropic metastasis of primary tumors. Traditional Chinese medicine (TCM) has shown considerable success in preventing and treating tumor metastasis. However, the underlying mechanisms remain elusive. In this review, we discussed PMN formation from the perspectives of TDE biogenesis, cargo sorting, and TDE recipient cell alterations, which are critical for metastatic outgrowth. We also reviewed the metastasis-preventive effects of TCM, which act by targeting the physicochemical materials and functional mediators of TDE biogenesis, regulating the cargo sorting machinery and secretory molecules in TDEs, and targeting the TDE-recipient cells involved in PMN formation.

It takes two to tango: the role of tumor-associated macrophages in T cell-directed immune checkpoint blockade therapy

Immunotherapy has revolutionized cancer care in the past decade. Treatment with immune checkpoint inhibitors has demonstrated promising clinical activity against tumors. However, only a subset of patients responds to these treatments, limiting their potential benefit. Efforts to understand, predict, and overcome the lack of response in patients, have thus far focused mainly on the tumor immunogenicity and the quantity and characteristics of tumor-infiltrating T cells, since these cells are the main effectors of immunotherapies. However, recent comprehensive analyses of the tumor microenvironment (TME) in the context of immune checkpoint blockade (ICB) therapy have revealed critical functions of other immune cells in the effective anti-tumor response, highlighting the need to account for complex cell-cell interaction and communication underlying clinical outputs. In this perspective, I discuss the current understanding of the crucial roles of tumor-associated macrophages (TAMs) in the success of T cell-directed immune checkpoint blockade therapies, as well as the present, and the future of clinical trials on combinatorial therapies targeting both cell types.

The chemokine monocyte chemoattractant protein-1/CCL2 is a promoter of breast cancer metastasis

Breast cancer is the most prevalent cancer worldwide, and metastasis is the leading cause of death in cancer patients. Human monocyte chemoattractant protein-1 (MCP-1/CCL2) was isolated from the culture supernatants of not only mitogen-activated peripheral blood mononuclear leukocytes but also malignant glioma cells based on its in vitro chemotactic activity toward human monocytes. MCP-1 was subsequently found to be identical to a previously described tumor cell-derived chemotactic factor thought to be responsible for the accumulation of tumor-associated macrophages (TAMs), and it became a candidate target of clinical intervention; however, the role of TAMs in cancer development was still controversial at the time of the discovery of MCP-1. The in vivo role of MCP-1 in cancer progression was first evaluated by examining human cancer tissues, including breast cancers. Positive correlations between the level of MCP-1 production in tumors and the degree of TAM infiltration and cancer progression were established. The contribution of MCP-1 to the growth of primary tumors and metastasis to the lung, bone, and brain was examined in mouse breast cancer models. The results of these studies strongly suggested that MCP-1 is a promoter of breast cancer metastasis to the lung and brain but not bone. Potential mechanisms of MCP-1 production in the breast cancer microenvironment have also been reported. In the present manuscript, we review studies in which the role of MCP-1 in breast cancer development and progression and the mechanisms of its production were examined and attempt to draw a consensus and discuss the potential use of MCP-1 as a biomarker for diagnosis.

Reactive myelopoiesis and FX-expressing macrophages triggered by chemotherapy promote cancer lung metastasis

Several preclinical studies have demonstrated that certain cytotoxic drugs enhance metastasis, but the importance of host responses triggered by chemotherapy in regulating cancer metastasis has not been fully explored. Here, we showed that multidose gemcitabine (GEM) treatment promoted breast cancer lung metastasis in a transgenic spontaneous breast cancer model. GEM treatment significantly increased accumulation of CCR2+ macrophages and monocytes in the lungs of tumor-bearing as well as tumor-free mice. These changes were largely caused by chemotherapy-induced reactive myelopoiesis biased toward monocyte development. Mechanistically, enhanced production of mitochondrial ROS was observed in GEM-treated BM Lin-Sca1+c-Kit+ cells and monocytes. Treatment with the mitochondria targeted antioxidant abrogated GEM-induced hyperdifferentiation of BM progenitors. In addition, GEM treatment induced upregulation of host cell-derived CCL2, and knockout of CCR2 signaling abrogated the pro-metastatic host response induced by chemotherapy. Furthermore, chemotherapy treatment resulted in the upregulation of coagulation factor X (FX) in lung interstitial macrophages. Targeting activated FX (FXa) using FXa inhibitor or F10 gene knockdown reduced the pro-metastatic effect of chemotherapy. Together, these studies suggest a potentially novel mechanism for chemotherapy-induced metastasis via the host response-induced accumulation of monocytes/macrophages and interplay between coagulation and inflammation in the lungs.

The temporal progression of immune remodeling during metastasis

Tumor metastasis requires systemic remodeling of distant organ microenvironments which impacts immune cell phenotypes, population structure, and intercellular communication networks. However, our understanding of immune phenotypic dynamics in the metastatic niche remains incomplete. Here, we longitudinally assayed lung immune cell gene expression profiles in mice bearing PyMT-driven metastatic breast tumors from the onset of primary tumorigenesis, through formation of the pre-metastatic niche, to the final stages of metastatic outgrowth. Computational analysis of these data revealed an ordered series of immunological changes that correspond to metastatic progression. Specifically, we uncovered a TLR-NFκB myeloid inflammatory program which correlates with pre-metastatic niche formation and mirrors described signatures of CD14+ 'activated' MDSCs in the primary tumor. Moreover, we observed that cytotoxic NK cell proportions increased over time which illustrates how the PyMT lung metastatic niche is both inflammatory and immunosuppressive. Finally, we predicted metastasis-associated immune intercellular signaling interactions involving Igf1 and Ccl6 which may organize the metastatic niche. In summary, this work identifies novel immunological signatures of metastasis and discovers new details about established mechanisms that drive metastatic progression.

Graphical abstract

In brief

McGinnis et al. report a longitudinal scRNA-seq atlas of lung immune cells in mice bearing PyMT-driven metastatic breast tumors and identify immune cell transcriptional states, shifts in population structure, and rewiring of cell-cell signaling networks which correlate with metastatic progression.

Highlights

Longitudinal scRNA-seq reveals distinct stages of immune remodeling before, during, and after metastatic colonization in the lungs of PyMT mice.TLR-NFκB inflammation correlates with pre-metastatic niche formation and involves both tissue-resident and bone marrow-derived myeloid cell populations. Inflammatory lung myeloid cells mirror 'activated' primary tumor MDSCs, suggesting that primary tumor-derived cues induce Cd14 expression and TLR-NFκB inflammation in the lung. Lymphocytes contribute to the inflammatory and immunosuppressive lung metastatic microenvironment, highlighted by enrichment of cytotoxic NK cells in the lung over time. Cell-cell signaling network modeling predicts cell type-specific Ccl6 regulation and IGF1-IGF1R signaling between neutrophils and interstitial macrophages.

Investigating Chemokine-Matrix Networks in Breast Cancer: Tenascin-C Sets the Tone for CCL2

Bidirectional dialogue between cellular and non-cellular components of the tumor microenvironment (TME) drives cancer survival. In the extracellular space, combinations of matrix molecules and soluble mediators provide external cues that dictate the behavior of TME resident cells. Often studied in isolation, integrated cues from complex tissue microenvironments likely function more cohesively. Here, we study the interplay between the matrix molecule tenascin-C (TNC) and chemokine CCL2, both elevated in and associated with the progression of breast cancer and playing key roles in myeloid immune responses. We uncover a correlation between TNC/CCL2 tissue levels in HER2+ breast cancer and examine the physical and functional interactions of these molecules in a murine disease model with tunable TNC levels and in in vitro cellular and cell-free models. TNC supported sustained CCL2 synthesis, with chemokine binding to TNC via two distinct domains. TNC dominated the behavior of tumor-resident myeloid cells; CCL2 did not impact macrophage survival/activation whilst TNC facilitated an immune suppressive macrophage phenotype that was not dependent on or altered by CCL2 co-expression. Together, these data map new binding partners within the TME and demonstrate that whilst the matrix exerts transcriptional control over the chemokine, each plays a distinct role in subverting anti-tumoral immunity.

The role of metabolic reprogramming of tumor-associated macrophages in shaping the immunosuppressive tumor microenvironment

Macrophages are potent immune effector cells in innate immunity and exert dual-effects in the tumor microenvironment (TME). Tumor-associated macrophages (TAMs) make up a significant portion of TME immune cells. Similar to M1/M2 macrophages, TAMs are also highly plastic, and their functions are regulated by cytokines, chemokines and other factors in the TME. The metabolic changes in TAMs are significantly associated with polarization towards a protumour or antitumour phenotype. The metabolites generated via TAM metabolic reprogramming in turn promote tumor progression and immune tolerance. In this review, we explore the metabolic reprogramming of TAMs in terms of energy, amino acid and fatty acid metabolism and the potential roles of these changes in immune suppression.

Therapeutic targeting of tumour myeloid cells

Myeloid cells are pivotal within the immunosuppressive tumour microenvironment. The accumulation of tumour-modified myeloid cells derived from monocytes or neutrophils - termed 'myeloid-derived suppressor cells' - and tumour-associated macrophages is associated with poor outcome and resistance to treatments such as chemotherapy and immune checkpoint inhibitors. Unfortunately, there has been little success in large-scale clinical trials of myeloid cell modulators, and only a few distinct strategies have been used to target suppressive myeloid cells clinically so far. Preclinical and translational studies have now elucidated specific functions for different myeloid cell subpopulations within the tumour microenvironment, revealing context-specific roles of different myeloid cell populations in disease progression and influencing response to therapy. To improve the success of myeloid cell-targeted therapies, it will be important to target tumour types and patient subsets in which myeloid cells represent the dominant driver of therapy resistance, as well as to determine the most efficacious treatment regimens and combination partners. This Review discusses what we can learn from work with the first generation of myeloid modulators and highlights recent developments in modelling context-specific roles for different myeloid cell subtypes, which can ultimately inform how to drive more successful clinical trials.

Macrophages Promote Tumor Cell Extravasation across an Endothelial Barrier through Thin Membranous Connections

Macrophages are important players involved in the progression of breast cancer, including in seeding the metastatic niche. However, the mechanism by which macrophages in the lung parenchyma interact with tumor cells in the vasculature to promote tumor cell extravasation at metastatic sites is not clear. To mimic macrophage-driven tumor cell extravasation, we used an in vitro assay (eTEM) in which an endothelial monolayer and a matrigel-coated filter separated tumor cells and macrophages from each other. The presence of macrophages promoted tumor cell extravasation, while macrophage conditioned media was insufficient to stimulate tumor cell extravasation in vitro. This finding is consistent with a requirement for direct contact between macrophages and tumor cells. We observed the presence of Thin Membranous Connections (TMCs) resembling similar structures formed between macrophages and tumor cells called tunneling nanotubes, which we previously demonstrated to be important in tumor cell invasion in vitro and in vivo. To determine if TMCs are important for tumor cell extravasation, we used macrophages with reduced levels of endogenous M-Sec (TNFAIP2), which causes a defect in tunneling nanotube formation. As predicted, these macrophages showed reduced macrophage-tumor cell TMCs. In both, human and murine breast cancer cell lines, there was also a concomitant reduction in tumor cell extravasation in vitro when co-cultured with M-Sec deficient macrophages compared to control macrophages. We also detected TMCs formed between macrophages and tumor cells through the endothelial layer in the eTEM assay. Furthermore, tumor cells were more frequently found in pores under the endothelium that contain macrophage protrusions. To determine the role of macrophage-tumor cell TMCs in vivo, we generated an M-Sec deficient mouse. Using an in vivo model of experimental metastasis, we detected a significant reduction in the number of metastatic lesions in M-Sec deficient mice compared to wild type mice. There was no difference in the size of the metastases, consistent with a defect specific to tumor cell extravasation and not metastatic outgrowth. Additionally, with an examination of time-lapse intravital-imaging (IVI) data sets of breast cancer cell extravasation in the lungs, we could detect the presence of TMCs between extravascular macrophages and vascular tumor cells. Overall, our data indicate that macrophage TMCs play an important role in promoting the extravasation of circulating tumor cells in the lungs.

Role of Heterogeneous Nuclear Ribonucleoproteins in the Cancer-Immune Landscape

Cancer remains the second leading cause of death, accounting for approximately 20% of all fatalities. Evolving cancer cells and a dysregulated immune system create complex tumor environments that fuel tumor growth, metastasis, and resistance. Over the past decades, significant progress in deciphering cancer cell behavior and recognizing the immune system as a hallmark of tumorigenesis has been achieved. However, the underlying mechanisms controlling the evolving cancer-immune landscape remain mostly unexplored. Heterogeneous nuclear ribonuclear proteins (hnRNP), a highly conserved family of RNA-binding proteins, have vital roles in critical cellular processes, including transcription, post-transcriptional modifications, and translation. Dysregulation of hnRNP is a critical contributor to cancer development and resistance. HnRNP contribute to the diversity of tumor and immune-associated aberrant proteomes by controlling alternative splicing and translation. They can also promote cancer-associated gene expression by regulating transcription factors, binding to DNA directly, or promoting chromatin remodeling. HnRNP are emerging as newly recognized mRNA readers. Here, we review the roles of hnRNP as regulators of the cancer-immune landscape. Dissecting the molecular functions of hnRNP will provide a better understanding of cancer-immune biology and will impact the development of new approaches to control and treat cancer.

The Chemokine Receptor CCR1 Mediates Microglia Stimulated Glioma Invasion

Glioblastoma multiforme (GBM) is the most aggressive form of adult brain tumor which is highly resistant to conventional treatment and therapy. Glioma cells are highly motile resulting in infiltrative tumors with poorly defined borders. Another hallmark of GBM is a high degree of tumor macrophage/microglia infiltration. The level of these tumor-associated macrophages/microglia (TAMs) correlates with higher malignancy and poorer prognosis. We previously demonstrated that inhibition of TAM infiltration into glioma tumors with the CSF-1R antagonist pexidartinib (PLX3397) can inhibit glioma cell invasion in-vitro and in-vivo. In this study, we demonstrate an important role for the chemokine receptor CCR1 in mediating microglia/TAM stimulated glioma invasion. Using two structurally distinct CCR1 antagonists, including a novel inhibitor “MG-1-5”, we were able to block microglial activated GL261 glioma cell invasion in a dose dependent manner. Interestingly, treatment of a murine microglia cell line with glioma conditioned media resulted in a strong induction of CCR1 gene and protein expression. This induction was attenuated by inhibition of CSF-1R. In addition, glioma conditioned media treatment of microglia resulted in a rapid upregulation of gene expression of several CCR1 ligands including CCL3, CCL5, CCL6 and CCL9. These data support the existence of tumor stimulated autocrine loop within TAMs which ultimately mediates tumor cell invasion.

Why Don't the Mutant Cells That Evade DNA Repair Cause Cancer More Frequently? Importance of the Innate Immune System in the Tumor Microenvironment

The standard of care for most malignant solid tumors still involves tumor resection followed by chemo- and radiation therapy, hoping to eliminate the residual tumor cells. This strategy has been successful in extending the life of many cancer patients. Still, for primary glioblastoma (GBM), it has not controlled recurrence or increased the life expectancies of patients. Amid such disappointment, attempts to design therapies using the cells in the tumor microenvironment (TME) have gained ground. Such "immunotherapies" have so far overwhelmingly used genetic modifications of Tc cells (Car-T cell therapy) or blocking of proteins (PD-1 or PD-L1) that inhibit Tc-cell-mediated cancer cell elimination. Despite such advances, GBM has remained a "Kiss of Death" for most patients. Although the use of innate immune cells, such as the microglia, macrophages, and natural killer (NK) cells, has been considered in designing therapies for cancers, such attempts have not reached the clinic yet. We have reported a series of preclinical studies highlighting strategies to "re-educate" GBM-associated microglia and macrophages (TAMs) so that they assume a tumoricidal status. Such cells then secrete chemokines to recruit activated, GBM-eliminating NK cells and cause the rescue of 50-60% GBM mice in a syngeneic model of GBM. This review discusses a more fundamental question that most biochemists harbor: "since we are generating mutant cells in our body all the time, why don't we get cancer more often?" The review visits publications addressing this question and discusses some published strategies for re-educating the TAMs to take on the "sentry" role they initially maintained in the absence of cancer.

The portrayal of macrophages as tools and targets: A paradigm shift in cancer management

Macrophages play a major role in maintaining an organism's physiology, such as development, homeostasis, tissue repair, and immunity. These immune cells are known to be involved in tumor progression and modulation. Monocytes can be polarized to two types of macrophages (M1 macrophages and pro-tumor M2 macrophages). Through this article, we aim to emphasize the potential of targeting macrophages in order to improve current strategies for tumor management. Various strategies that target macrophages as a therapeutic target have been discussed along with ongoing clinical trials. We have discussed the role of macrophages in various stages of tumor progression epithelial-to-mesenchymal transition (EMT), invasion, maintaining the stability of circulating tumor cells (CTCs) in blood, and establishing a premetastatic niche along with the role of various cytokines and chemokines involved in these processes. Intriguingly macrophages can also serve as drug carriers due to their tumor tropism along the chemokine gradient. They surpass currently explored nanotherapeutics in tumor accumulation and circulation half-life. We have emphasized on macrophage-based biomimetic formulations and macrophage-hitchhiking as a strategy to effectively target tumors. We firmly believe that targeting macrophages or utilizing them as an indigenous carrier system could transform cancer management.

Macrophages Promote Tumor Cell Extravasation across an Endothelial Barrier through Thin Membranous Connections

Macrophages are important players involved in the progression of breast cancer, including in seeding the metastatic niche. However, the mechanism by which macrophages in the lung parenchyma interact with tumor cells in the vasculature to promote tumor cell extravasation at metastatic sites is not clear. To mimic macrophage-driven tumor cell extravasation, we used an in vitro assay (eTEM) in which an endothelial monolayer and a matrigel-coated filter separated tumor cells and macrophages from each other. The presence of macrophages promoted tumor cell extravasation while macrophage conditioned media was insufficient to stimulate tumor cell extravasation in vitro . This finding is consistent with a requirement for direct contact between macrophages and tumor cells. We observed the presence of Thin Membranous Connections (TMCs) resembling similar structures formed between macrophages and tumor cells called tunneling nanotubes which we previously demonstrated to be important in tumor cell invasion in vitro and in vivo (Hanna 2019). To determine if TMCs are important for tumor cell extravasation, we used macrophages with reduced levels of endogenous M-Sec (TNFAIP2), which causes a defect in tunneling nanotube formation. As predicted, these macrophages showed reduced macrophage-tumor cell TMCs. In both, human and murine breast cancer cell lines, there was also a concomitant reduction in tumor cell extravasation in vitro when co-cultured with M-Sec deficient macrophages compared to control macrophages. We also detected TMCs formed between macrophages and tumor cells through the endothelial layer in the eTEM assay. Furthermore, tumor cells were more frequently found in pores under the endothelium that contain macrophage protrusions. To determine the role of macrophage-tumor cell TMCs in vivo , we generated an M-Sec deficient mouse. Using an in vivo model of experimental metastasis, we detected a significant reduction in the number of metastatic lesions in M-Sec deficient mice compared to wild type mice. There was no difference in the size of the metastases, consistent with a defect specific to tumor cell extravasation and not metastatic outgrowth. Additionally, examination of time-lapse intravital-imaging (IVI) data sets of breast cancer cell extravasation in the lung, we could detect the presence of TMCs between extravascular macrophages and vascular tumor cells. Overall, our data indicate that macrophage TMCs play an important role in promoting the extravasation of circulating tumor cells in the lung.

A timeline of tumour-associated macrophage biology

Tumour progression is modulated by the local microenvironment. This environment is populated by many immune cells, of which macrophages are among the most abundant. Clinical correlative data and a plethora of preclinical studies in mouse models of cancers have shown that tumour-associated macrophages (TAMs) play a cancer-promoting role. Within the primary tumour, TAMs promote tumour cell invasion and intravasation and tumour stem cell viability and induce angiogenesis. At the metastatic site, metastasis-associated macrophages promote extravasation, tumour cell survival and persistent growth, as well as maintain tumour cell dormancy in some contexts. In both the primary and metastatic sites, TAMs are suppressive to the activities of cytotoxic T and natural killer cells that have the potential to eradicate tumours. Such activities suggest that TAMs will be a major target for therapeutic intervention. In this Perspective article, we chronologically explore the evolution of our understanding of TAM biology put into the context of major enabling advances in macrophage biology.