Crosstalk between Macrophages and Endothelial Cells in the Tumor Microenvironment

Therapeutic advances targeting tumor angiogenesis in pancreatic cancer: Current dilemmas and future directions

Pancreatic cancer (PC) is one of the most lethal malignancies, which is generally resistant to various treatments. Tumor angiogenesis is deemed to be a pivotal rate-determining step for tumor growth and metastasis. Therefore, anti-angiogenetic therapy is a rational strategy to treat various cancers. However, numerous clinical trials on anti-angiogenetic therapies for PC are overwhelmingly disappointing. The unique characteristics of tumor blood vessels in PC, which are desperately lacking and highly compressed by the dense desmoplastic stroma, are reconsidered to explore some optimized strategies. In this review, we mainly focus on its specific characteristics of tumor blood vessels, discuss the current dilemmas of anti-angiogenic therapy in PC and their underlying mechanisms. Furthermore, we point out the future directions, including remodeling the abnormal vasculature or even reshaping the whole tumor microenvironment in which they are embedded to improve tumor microcirculation, and then create therapeutic vulnerabilities to the current available therapeutic strategies.

The stress-responsive protein REDD1 and its pathophysiological functions

Regulated in development and DNA damage-response 1 (REDD1) is a stress-induced protein that controls various cellular functions, including metabolism, oxidative stress, autophagy, and cell fate, and contributes to the pathogenesis of metabolic and inflammatory disorders, neurodegeneration, and cancer. REDD1 usually exerts deleterious effects, including tumorigenesis, metabolic inflammation, neurodegeneration, and muscle dystrophy; however, it also exhibits protective functions by regulating multiple intrinsic cell activities through either an mTORC1-dependent or -independent mechanism. REDD1 typically regulates mTORC1 signaling, NF-κB activation, and cellular pro-oxidant or antioxidant activity by interacting with 14-3-3 proteins, IκBα, and thioredoxin-interacting protein or 75 kDa glucose-regulated protein, respectively. The diverse functions of REDD1 depend on cell type, cellular context, interaction partners, and cellular localization (e.g., mitochondria, endomembrane, or cytosol). Therefore, comprehensively understanding the molecular mechanisms and biological roles of REDD1 under pathophysiological conditions is of utmost importance. In this review, based on the published literature, we highlight and discuss the molecular mechanisms underlying the REDD1 expression and its actions, biological functions, and pathophysiological roles.

Tissue nanotransfection causes tumor regression by its effect on nanovesicle cargo that alters microenvironmental macrophage state

Extracellular vesicles (EVs) are nanovesicles released by all eukaryotic cells. This work reports the first nanoscale fluorescent visualization of tumor-originating vesicles bearing an angiogenic microRNA (miR)-126 cargo. In a validated experimental model of lethal murine vascular neoplasm, tumor-originating EV delivered its miR-126 cargo to tumor-associated macrophages (TAMs). Such delivery resulted in an angiogenic (LYVE+) change of state in TAM that supported tumor formation. Study of the trafficking of tumor-originating fluorescently tagged EV revealed colocalization with TAM demonstrating uptake by these cells. Ex vivo treatment of macrophages with tumor-derived EVs led to gain of tumorigenicity in these isolated cells. Single-cell RNA sequencing of macrophages revealed that EV-borne miR-126 characterized the angiogenic change of state. Unique gene expression signatures of specific macrophage clusters responsive to miR-126-enriched tumor-derived EVs were revealed. Topical tissue nanotransfection (TNT) delivery of an oligonucleotide comprising an anti-miR against miR-126 resulted in significant knockdown of miR-126 in the tumor tissue. miR-126 knockdown resulted in complete involution of the tumor and improved survival rate of tumor-affected mice. This work identifies a novel tumorigenic mechanism that relies on tumorigenic state change of TAM caused by tumor-originating EV-borne angiomiR. This disease process can be effectively targeted by topical TNT of superficial tumors.

M2 macrophages-derived exosomal miR-3917 promotes the progression of lung cancer via targeting GRK6

Macrophages in the tumor microenvironment (TME) can serve as potential targets for therapeutic intervention. The aim of this study was to investigate the molecular mechanism by which M2 macrophage-derived exosomes (M2-Ex) affect lung cancer progression through miRNA transport. The THP-1 cells were differentiated into M0 and M2 macrophages. M2-Ex were isolated and identified by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Cancer tissues and adjacent tissues of non-small-cell lung cancer (NSCLC) patients were collected. H1299 and A549 cells were co-cultured with M2-Ex. Subcutaneous xenograft mouse model was established. miR-3917 is highly expressed in lung cancer tissues and M2-Ex. Interference of miR-3917 in M2-Ex inhibits H1299 cell proliferation, migration and invasion, while overexpression of miR-3917 had the opposite effect in A549 cells. M2-Ex promote tumor growth by delivering miR-3917 in vivo. miR-3917 could target G protein-coupled receptor kinase 6 (GRK6), and interference of miR-3917 in M2-Ex inhibits H1299 cells proliferation, migration and invasion by up-regulating GRK6 level, while overexpression of miR-3917 had the opposite effect in A549 cells. M2-Ex can transfer miR-3917 into lung cancer cells and promote lung cancer progression, providing theoretical basis for the diagnosis and effective treatment of lung cancer.

Role of Biological Mediators of Tumor-Associated Macrophages in Breast Cancer Progression

BACKGROUND

Breast cancer (BRCA) has become the most common cancer worldwide. The tumor microenvironment (TME) in the breast exerts a crucial role in promoting BRCA initiation, progression, and metastasis. Tumor-associated macrophages (TAMs) are the primary component of tumor-infiltrating immune cells through biological mediators which convert TME into malignant tumors. Combinations of these biological mediators can promote tumor growth, metastasis, angiogenesis, immune suppression, and limit the anti-tumor activity of conventional chemotherapy and radiotherapy.

OBJECTIVES

The present study aimed to highlight the functions of several biological mediators in the breast which generate TME into malignant tumors. Furthermore, this review offers a rationale for TAM-targeted therapy as a novel treatment strategy for BRCA Results: this review emphasizes TAM-associated biological mediators of TME viz., cancer-associated fibroblasts, endothelial cells, adipocytes, tumor-derived exosomes, extracellular matrix, and other immune cells, which facilitates TME into malignant tumors. Evidence suggests that the increased infiltration of TAMs and elevated expression of TAM-related genes are associated with a poor prognosis of BRCA. Based on these findings, TAM-targeted therapeutic strategies, including inhibitors of CSF-1/CSF-1R, CCL2/CCR2, CCL5-CCR5, bisphosphonate, nanoparticle, and exosomal-targeted delivery have been developed, and are currently being employed in intervention trials.

CONCLUSION

This review concludes the roles of biological mediators of TME interact with TAMs in BRCA that provide a rationale for TAM-targeted therapy as a novel treatment approach for BRCA.

Dual Relationship Between Stromal Cells and Immune Cells in the Tumor Microenvironment

The tumor microenvironment (TME) plays a critical role in tumorigenesis and is comprised of different components, including tumor cells, stromal cells, and immune cells. Among them, the relationship between each mediator involved in the construction of the TME can be understood by focusing on the secreting or expressing factors from each cells. Therefore, understanding the various interactions between each cellular component of the TME is necessary for precise therapeutic approaches. In carcinoma, stromal cells are well known to influence extracellular matrix (ECM) formation and tumor progression through multiple mediators. Immune cells respond to tumor cells by causing cytotoxicity or inflammatory responses. However, they are involved in tumor escape through immunoregulatory mechanisms. In general, anti-cancer therapy has mainly been focused on cancer cells themselves or the interactions between cancer cells and specific cell components. However, cancer cells directly or indirectly influence other TME partners, and members such as stromal cells and immune cells also participate in TME organization through their mutual communication. In this review, we summarized the relationship between stromal cells and immune cells in the TME and discussed the positive and negative relationships from the point of view of tumor development for use in research applications and therapeutic strategies.

Dysregulated tumor-associated macrophages in carcinogenesis, progression and targeted therapy of gynecological and breast cancers

Gynecological and breast cancers are a group of heterogeneous malignant tumors. Although existing treatment strategies have ameliorated the clinical outcomes of patients, the overall survival rate of advanced diseases remains unsatisfactory. Increasing evidence has indicated that the development and prognosis of tumors are closely related to the tumor microenvironment (TME), which restricts the immune response and provokes malignant progression. Tumor-associated macrophages (TAMs) are the main component of TME and act as a key regulator in tumor metastasis, immunosuppression and therapeutic resistance. Several preclinical trials have studied potential drugs that target TAMs to achieve potent anticancer therapy. This review focuses on the various functions of TAMs and how they influence the carcinogenesis of gynecological and breast cancers through regulating cancer cell proliferation, tumor angiogenesis and tumor-related immunosuppression. Besides, we also discuss the potential application of disabling TAMs signaling as a part of cancer therapeutic strategies, as well as CAR macrophages, TAMs-based vaccines and TAMs nanobiotechnology. These research advances support that targeting TAMs combined with conventional therapy might be used as effective therapeutics for gynecological and breast cancers in the future.