Evolving polarisation of infiltrating and alveolar macrophages in the lung during metastatic progression of melanoma suggests CCR1 as a therapeutic target

Inflammatory chemokine receptors CCR1, CCR2, CCR3 and CCR5 are essential for an optimal T cell response to influenza

Inflammatory chemokine receptors CCR1/2/3/5 (iCCRs) play an important role in the recruitment of immune cells involved in innate immune functions and orchestrating the adaptive immune response. Here we utilise an influenza A virus (IAV) challenge to investigate the combinatorial roles of the iCCRs in the anti-IAV immune response. We did not observe any gross differences in infection-driven pathology in the absence of iCCRs. iCCR deletion resulted in decreased numbers of some antigen-presenting cell types in the lung (B cells, DC1s, monocytes and inflammatory macrophages), though cell numbers in the draining lymph node were not affected. Whilst the total number of T cells was similar in lungs of iCCR-deficient mice, the number of IAV-specific CD4 but not CD8 T cells in the lung was strongly reduced in the absence of iCCRs. Furthermore, fewer CD4, but not CD8, T cells produced IFN-γ. This CD4 T cell phenotype persisted into the memory stage of infection, with fewer IAV-specific and IFN-γ+ CD4 but not CD8 T cells at 29 days post infection. In conclusion, despite having limited impact on antigen-presenting cell migration between the lung and the draining lymph node, iCCR deletion is associated with an altered CD4 T cell response to IAV infection.

The Use of Biologics for Targeting GPCRs in Metastatic Cancers

A comprehensive review of studies describing the role of G-protein coupled receptor (GPCR) behaviour contributing to metastasis in cancer, and the developments of biotherapeutic drugs towards targeting them, provides a valuable resource toward improving our understanding of the opportunities to effectively target this malignant tumour cell adaptation. Focusing on the five most common metastatic cancers of lung, breast, colorectal, melanoma, and prostate cancer, we highlight well-studied and characterised GPCRs and some less studied receptors that are also implicated in the development of metastatic cancers. Of the approximately 390 GPCRs relevant to therapeutic targeting, as many as 125 of these have been identified to play a role in promoting metastatic disease in these cancer types. GPCR signalling through the well-characterised pathways of chemokine receptors, to emerging data on signalling by orphan receptors, is integral to many aspects of the metastatic phenotype. Despite having detailed information on many receptors and their ligands, there are only thirteen approved therapeutics specifically for metastatic cancer, of which three are small molecules with the remainder including synthetic and non-synthetic peptides or monoclonal antibodies. This review will cover the existing and potential use of monoclonal antibodies, proteins and peptides, and nanobodies in targeting GPCRs for metastatic cancer therapy.

Non-redundant roles of the CCR1 and CCR2 chemokine axes in monocyte recruitment during lung metastasis

Monocytes and monocyte-derived macrophages facilitate cancer progression and metastasis. Inflammatory monocytes expressing CCR2 are actively recruited to metastatic lungs, where they promote tumor cell extravasation, metastatic outgrowth, and an immunosuppressive environment. The role of CCR1 in this process has remained unclear. We used Ccr1- and Ccr2-deficient mice and two different tumor cells lines, MC38 and LLC1 with and without Ccl2-deficiency in vitro and in vivo. The recruitment of both Ccr1- and Ccr2-deficient monocytes towards the Ccl2 chemokine was significantly impaired, while no substantial recruitment was observed towards Ccl5 in vitro. MC38 and LLC1 Ccl2-deficient tumor cells showed reduced lung metastasis in both Ccr1- and Ccr2-deficient mice when compared to wild-type mice. We detected reduced numbers of macrophages and myeloid cells in both chemokine receptor-deficient mice. Lung metastasis in both Ccr1- and Ccr2-deficient mice could be rescued to the same levels as in wild-type mice by an adoptive transfer of Ccr2-deficient but not Ccr1-deficient monocytic cells. Accumulation of Ccr1-deficient monocytes in the lungs was severely impaired upon intravenous monocyte injection, indicating the importance of this axis in cell recruitment. Moreover, the efficient recruitment of adoptive transferred Ccr2-deficient monocytes to the lungs and the restoration of lung metastasis suggests an involvement of an additional, Ccr2-independent chemokine pathway. This data defines the non-redundant functions of the Ccr1- and Ccr2-chemokine axes in monocyte recruitment and macrophage presence during lung metastasis. While Ccr2 is essential for the release of monocytes from the bone marrow, Ccr1 is primarily responsible for monocyte presence at metastatic sites.

Neutrophil and Colorectal Cancer

Colorectal cancer (CRC) is often associated with metastasis and recurrence and is the leading cause of cancer-related mortality. In the progression of CRC, recent studies have highlighted the critical role of neutrophils, particularly tumor-associated neutrophils (TANs). TANs have both tumor-promoting and tumor-suppressing activities, contributing to metastasis, immunosuppression, angiogenesis, and epithelial-to-mesenchymal transition. Tumor-promoting TANs promote tumor growth by releasing proteases, reactive oxygen species, and cytokines, whereas tumor-suppressing TANs enhance immune responses by activating T cells and natural killer cells. Understanding the mechanisms underlying TAN mobilization, plasticity, and their role in the tumor microenvironment has revealed potential therapeutic targets. This review provides a comprehensive overview of TAN biology in CRC and discusses both the tumor-promoting and tumor-suppressing functions of neutrophils. Novel therapeutic approaches targeting TANs, such as chemokine receptor antagonists, aim to modulate neutrophil reprogramming and offer promising avenues for improving treatment outcomes of CRC.

Enhanced CCR2 expression by ACKR2-deficient NK cells increases tumoricidal cell therapy efficacy

Chemokines regulate leukocyte navigation to inflamed sites and specific tissue locales and may therefore be useful for ensuring accurate homing of cell therapeutic products. We, and others, have shown that atypical chemokine receptor 2 (ACKR2)-deficient mice (ACKR2-/-) are protected from metastasis development in cell line and spontaneous mouse models. We have shown that this relates to enhanced CCR2 expression on ACKR2-/- natural killer cells, allowing them to home more effectively to CCR2 ligand-expressing metastatic deposits. Here we demonstrate that the metastatic-suppression phenotype in ACKR2-/- mice is not a direct effect of the absence of ACKR2. Instead, enhanced natural killer cell CCR2 expression is caused by passenger mutations that originate from the creation of the ACKR2-/- mouse strain in 129 embryonic stem cells. We further demonstrate that simple selection of CCR2+ natural killer cells enriches for a population of cells with enhanced antimetastatic capabilities. Given the widespread expression of CCR2 ligands by tumors, our study highlights CCR2 as a potentially important contributor to natural killer cell tumoricidal cell therapy.

Tissue-Resident Macrophages in Cancer: Friend or Foe?

INTRODUCTION

Macrophages are essential in maintaining homeostasis, combating infections, and influencing the process of various diseases, including cancer. Macrophages originate from diverse lineages: Notably, tissue-resident macrophages (TRMs) differ from hematopoietic stem cells and circulating monocyte-derived macrophages based on genetics, development, and function. Therefore, understanding the recruited and TRM populations is crucial for investigating disease processes.

METHODS

By searching literature databses, we summarized recent relevant studies. Research has shown that tumor-associated macrophages (TAMs) of distinct origins accumulate in tumor microenvironment (TME), with TRM-derived TAMs closely resembling gene signatures of normal TRMs.

RESULTS

Recent studies have revealed that TRMs play a crucial role in cancer progression. However, organ-specific effects complicate TRM investigations. Nonetheless, the precise involvement of TRMs in tumors is unclear. This review explores the multifaceted roles of TRMs in cancer, presenting insights into their origins, proliferation, the latest research methodologies, their impact across various tumor sites, their potential and strategies as therapeutic targets, interactions with other cells within the TME, and the internal heterogeneity of TRMs.

CONCLUSIONS

We believe that a comprehensive understanding of the multifaceted roles of TRMs will pave the way for targeted TRM therapies in the treatment of cancer.

Synergistic antitumor activity by dual blockade of CCR1 and CXCR2 expressed on myeloid cells within the tumor microenvironment

BACKGROUND

Chemokine signaling within the tumor microenvironment can promote tumor progression. Although CCR1 and CXCR2 on myeloid cells could be involved in tumor progression, it remains elusive what effect would be observed if both of those are blocked.

METHODS

We employed two syngeneic colorectal cancer mouse models: a transplanted tumor model and a liver metastasis model. We generated double-knockout mice for CCR1 and CXCR2, and performed bone marrow (BM) transfer experiments in which sub-lethally irradiated wild-type mice were reconstituted with BM from either wild-type, Ccr1-/-, Cxcr2-/- or Ccr1-/-Cxcr2-/- mice.

RESULTS

Myeloid cells that express MMP2, MMP9 and VEGF were accumulated around both types of tumors through CCR1- and CXCR2-mediated pathways. Mice reconstituted with Ccr1-/-Cxcr2-/- BM exhibited the strongest suppression of tumor growth and liver metastasis compared with other three groups. Depletion of CCR1+CXCR2+ myeloid cells led to a higher frequency of CD8+ T cells, whereas the numbers of Ly6G+ neutrophils, FOXP3+ Treg cells and CD31+ endothelial cells were significantly decreased. Furthermore, treatment with a neutralizing anti-CCR1 mAb to mice reconstituted with Cxcr2-/- BM significantly suppressed tumor growth and liver metastasis.

CONCLUSION

Dual blockade of CCR1 and CXCR2 pathways in myeloid cells could be an effective therapy against colorectal cancer.

CD276-dependent efferocytosis by tumor-associated macrophages promotes immune evasion in bladder cancer

Interplay between innate and adaptive immune cells is important for the antitumor immune response. However, the tumor microenvironment may turn immune suppressive, and tumor associated macrophages are playing a role in this transition. Here, we show that CD276, expressed on tumor-associated macrophages (TAM), play a role in diminishing the immune response against tumors. Using a model of tumors induced by N-butyl-N-(4-hydroxybutyl) nitrosamine in BLCA male mice we show that genetic ablation of CD276 in TAMs blocks efferocytosis and enhances the expression of the major histocompatibility complex class II (MHCII) of TAMs. This in turn increases CD4 + and cytotoxic CD8 + T cell infiltration of the tumor. Combined single cell RNA sequencing and functional experiments reveal that CD276 activates the lysosomal signaling pathway and the transcription factor JUN to regulate the expression of AXL and MerTK, resulting in enhanced efferocytosis in TAMs. Proving the principle, we show that simultaneous blockade of CD276 and PD-1 restrain tumor growth better than any of the components as a single intervention. Taken together, our study supports a role for CD276 in efferocytosis by TAMs, which is potentially targetable for combination immune therapy.

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.

Advanced insights on tumor-associated macrophages revealed by single-cell RNA sequencing: The intratumor heterogeneity, functional phenotypes, and cellular interactions

Single-cell RNA sequencing (scRNA-seq) is an emerging technology used for cellular transcriptome analysis. The application of scRNA-seq has led to profoundly advanced oncology research, continuously optimizing novel therapeutic strategies. Intratumor heterogeneity extensively consists of all tumor components, contributing to different tumor behaviors and treatment responses. Tumor-associated macrophages (TAMs), the core immune cells linking innate and adaptive immunity, play significant roles in tumor progression and resistance to therapies. Moreover, dynamic changes occur in TAM phenotypes and functions subject to the regulation of the tumor microenvironment. The heterogeneity of TAMs corresponding to the state of the tumor microenvironment has been comprehensively recognized using scRNA-seq. Herein, we reviewed recent research and summarized variations in TAM phenotypes and functions from a developmental perspective to better understand the significance of TAMs in the tumor microenvironment.

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

Microenvironmental Changes in Mediastinal Fat-associated Lymphoid Clusters and Lungs in Early and Late Stages of Metastatic Lung Cancer Induction

The prognosis of metastatic lung melanoma (MLM) has been reported to be poor. An increasing number of studies have reported the function of several immune cells in cancer regression. Although the function of mediastinal fat-associated lymphoid clusters (MFALCs) in the progression of inflammatory lung lesions has been previously reported, the association between MLM progression and MFALCs development has remained unexplored. Herein, we compared the microenvironmental changes in the lungs and MFALCs among phosphate-buffered saline (PBS) and cancer groups at early (1 week) and late (2 weeks) stages following the intravenous injection of B16-F10 melanoma cells into C57BL/6 mice. Except for lung CD4+ helper T-cells and Iba1+ macrophage populations of early stage, we observed a significant increase in the proliferating and immune cell (CD20+ B-lymphocytes, CD3+ T-lymphocytes, CD8+ cytotoxic T-cells, CD16+ natural killer (NK) cells populations, area of high endothelial venules, and lung lymphatic vessels in cancer groups at both the stages as compared with the PBS groups. Furthermore, a significant positive correlation was observed between immune cell populations in MFALCs and the lungs (B- and T-lymphocytes, and NK cells in both stages). Collectively, our findings suggest a promising cancer therapeutic strategy via targeting immune cells in MFALCs.