Colorectal Cancer-Derived Small Extracellular Vesicles Promote Tumor Immune Evasion by Upregulating PD-L1 Expression in Tumor-Associated Macrophages

Ultrasensitive quantification of PD-L1+ extracellular vesicles in melanoma patient plasma using a parallelized high throughput droplet digital assay

The expression of programmed death-ligand 1 (PD-L1) on extracellular vesicles (EVs) is an emerging biomarker for cancer, and has gained particular interest for its role mediating immunotherapy. However, precise quantification of PD-L1+ EVs in clinical samples remains challenging due to their sparse concentration and the enormity of the number of background EVs in human plasma, limiting applicability of conventional approaches. In this study, we develop a high-throughput droplet-based extracellular vesicle analysis (DEVA) assay for ultrasensitive quantification of EVs in plasma that are dual positive for both PD-L1 and tetraspanin (CD81) known to be expressed on EVs. We achieve a performance that significantly surpasses conventional approaches, demonstrating 360× enhancement in the limit of detection (LOD) and a 750× improvement in the limit of quantitation (LOQ) compared to conventional plate enzyme-linked immunoassay (ELISA). Underlying this performance is DEVA's high throughput analysis of individual EVs one at a time and the high specificity to targeted EVs versus background. We achieve a 0.006% false positive rate per droplet by leveraging avidity effects that arise from EVs having multiple copies of their target ligands on their surface. We use parallelized optofluidics to rapidly process 10 million droplets per minute, ∼100× greater than conventional approaches. A validation study on a cohort of 14 patients with melanoma confirms DEVA's ability to match conventional ELISA measurements with reduced plasma sample volume and without the need for prior EV purification. This proof-of-concept study demonstrates DEVA's potential for clinical utility to enhance prognosis as well as guide treatment for cancer.

MicroRNAs in extracellular vesicles: A potential role in cancer progression

Intercellular communication, an essential biological process in multicellular organisms, is mediated by direct cell-to-cell contact and cell secretary molecules. Emerging evidence identifies a third mechanism of intercellular communication- the release of extracellular vesicles (EVs). EVs are membrane-enclosed nanosized bodies, released from cells into the extracellular environment, often found in all biofluids. The growing body of research indicates that EVs carry bioactive molecules in the form of proteins, DNA, RNAs, microRNAs (miRNAs), lipids, metabolites, etc., and upon transferring them, alter the phenotypes of the target recipient cells. Interestingly, the abundance of EVs is found to be significantly higher in different diseased conditions, most importantly cancer. In the past few decades, numerous studies have identified EV miRNAs as an important contributor in the pathogenesis of different types of cancer. However, the underlying mechanism behind EV miRNA-associated cancer progression and how it could be used as a targeted therapy remain ill-defined. The present review highlights how EV miRNAs influence essential processes in cancer, such as growth, proliferation, metastasis, angiogenesis, apoptosis, stemness, immune evasion, resistance to therapy, etc. A special emphasis has been given to the potential role of EV miRNAs as cancer biomarkers. The final section of the review delineates the ongoing clinical trials on the role of miRNAs in the progression of different types of cancer. Targeting EV miRNAs could be a potential therapeutic means in the treatment of different forms of cancer alongside conventional therapeutic approaches.

Syringeable Near-Infrared Light-Activated In Situ Immunogenic Hydrogel Boosts the Cancer-Immunity Cycle to Enhance Anticancer Immunity

Effective anticancer immunity depends on properly activating multiple stepwise events in the cancer-immunity cycle. An immunologically "cold" tumor microenvironment (TME) engenders immune evasion and refractoriness to conventional checkpoint blockade immunotherapy. Here, we combine nanoparticle formulations and an in situ formed hydrogel scaffold to treat accessible tumors locally and to stimulate systemic immunity against metastatic tumor lesions. The nanoparticles encapsulate poly(ε-caprolactone)-derived cytotoxic chemotherapy and adjuvant of Toll-like receptor 7/8 through a reactive oxygen species (ROS)-cleavable linker that can be self-activated by the coassembled neighboring photosensitizer following near-infrared (NIR) laser irradiation. Further development results in syringeable, NIR light-responsive, and immunogenic hydrogel (iGEL) that can be implanted peritumorally and deposited into the tumor surgical bed. Upon NIR laser irradiation, the generated ROS induces iGEL degradation and bond cleavage in the polymer-drug conjugates, triggering the immunogenic cell death cascade in cancer cells and spontaneously releasing encapsulated agents to rewire the cancer-immunity cycle. Notably, upon application in multiple preclinical models of melanoma and triple-negative breast cancer, which are aggressive and refractory to conventional immunotherapy, iGEL induces durable remission of established tumors, extends postsurgical tumor-free survival, and inhibits metastatic burden. The result of this study is a locally administrable immunogenic hydrogel for triggering host systemic immunity to improve immunotherapeutic efficacy with minimal off-target side effects.

M2 Tumor-Associated Macrophages-Derived Exosomal MALAT1 Promotes Glycolysis and Gastric Cancer Progression

M2-polarized tumor-associated macrophages (M2 TAMs) promote cancer progression. Exosomes mediate cellular communication in the tumor microenvironment (TME). However, the roles of exosomes from M2 TAMs in gastric cancer progression are unclear. Herein, it is reported that M2 TAMs-derived exosomes induced aerobic glycolysis in gastric cancer cells and enhanced their proliferation, metastasis, and chemoresistance in a glycolysis-dependent manner. It is identified that MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) is enriched in M2 TAM exosomes and confirmed that MALAT1 transfer from M2 TAMs to gastric cancer cells via exosomes mediates this effect. Mechanistically, MALAT1 interacted with the δ-catenin protein and suppressed its ubiquitination and degradation by β-TRCP. In addition, MALAT1 upregulated HIF-1α expression by acting as a sponge for miR-217-5p. The activation of β-catenin and HIF-1α signaling pathways by M2 TAM exosomes collectively led to enhanced aerobic glycolysis in gastric cancer cells. Finally, a dual-targeted inhibition of MALAT1 in both gastric cancer cells and macrophages by exosome-mediated delivery of siRNA remarkably suppressed gastric cancer growth and improved chemosensitivity in mouse tumor models. Taken together, these results suggest that M2 TAMs-derived exosomes promote gastric cancer progression via MALAT1-mediated regulation of glycolysis. The findings offer a potential target for gastric cancer therapy.

Extracellular vesicles containing MFGE8 from colorectal cancer facilitate macrophage efferocytosis

BACKGROUND

Colorectal cancer (CRC) commonly exhibits tolerance to cisplatin treatment, but the underlying mechanisms remain unclear. Within the tumor microenvironment, macrophages play a role in resisting the cytotoxic effects of chemotherapy by engaging in efferocytosis to clear apoptotic cells induced by chemotherapeutic agents. The involvement of extracellular vesicles (EVs), an intercellular communicator within the tumor microenvironment, in regulating the efferocytosis for the promotion of drug resistance has not been thoroughly investigated.

METHODS

We constructed GFP fluorescent-expressing CRC cell lines (including GFP-CT26 and GFP-MC38) to detect macrophage efferocytosis through flow cytometric analysis. We isolated and purified CRC-secreted EVs using a multi-step ultracentrifugation method and identified them through electron microscopy and nanoflow cytometry. Proteomic analysis was conducted to identify the protein molecules carried by CRC-EVs. MFGE8 knockout CRC cell lines were constructed using CRISPR-Cas9, and their effects were validated through in vitro and in vivo experiments using Western blotting, immunofluorescence, and flow cytometric analysis, confirming that these EVs activate the macrophage αvβ3-Src-FAK-STAT3 signaling pathway, thereby promoting efferocytosis.

RESULTS

In this study, we found that CRC-derived EVs (CRC-EVs) enhanced macrophage efferocytosis of cisplatin-induced apoptotic CRC cells. Analysis of The Cancer Genome Atlas (TCGA) database revealed a high expression of the efferocytosis-associated gene MFGE8 in CRC patients, suggesting a poorer prognosis. Additionally, mass spectrometry-based proteomic analysis identified a high abundance of MFGE8 protein in CRC-EVs. Utilizing CRISPR-Cas9 gene edition system, we generated MFGE8-knockout CRC cells, demonstrating that their EVs fail to upregulate macrophage efferocytosis in vitro and in vivo. Furthermore, we demonstrated that MFGE8 in CRC-EVs stimulated macrophage efferocytosis by increasing the expression of αvβ3 on the cell surface, thereby activating the intracellular Src-FAK-STAT3 signaling pathway.

CONCLUSIONS

Therefore, this study highlighted a mechanism in CRC-EVs carrying MFGE8 activated the macrophage efferocytosis. This activation promoted the clearance of cisplatin-induced apoptotic CRC cells, contributing to CRC resistance against cisplatin. These findings provide novel insights into the potential synergistic application of chemotherapy drugs, EVs inhibitors, and efferocytosis antagonists for CRC treatment.

The multifaceted role of extracellular vesicles (EVs) in colorectal cancer: metastasis, immune suppression, therapy resistance, and autophagy crosstalk

Extracellular vesicles (EVs) are lipid bilayer structures released by all cells and widely distributed in all biological fluids. EVs are implicated in diverse physiopathological processes by orchestrating cell-cell communication. Colorectal cancer (CRC) is one of the most common cancers worldwide, with metastasis being the leading cause of mortality in CRC patients. EVs contribute significantly to the advancement and spread of CRC by transferring their cargo, which includes lipids, proteins, RNAs, and DNAs, to neighboring or distant cells. Besides, they can serve as non-invasive diagnostic and prognostic biomarkers for early detection of CRC or be harnessed as effective carriers for delivering therapeutic agents. Autophagy is an essential cellular process that serves to remove damaged proteins and organelles by lysosomal degradation to maintain cellular homeostasis. Autophagy and EV release are coordinately activated in tumor cells and share common factors and regulatory mechanisms. Although the significance of autophagy and EVs in cancer is well established, the exact mechanism of their interplay in tumor development is obscure. This review focuses on examining the specific functions of EVs in various aspects of CRC, including progression, metastasis, immune regulation, and therapy resistance. Further, we overview emerging discoveries relevant to autophagy and EVs crosstalk in CRC.

Selective but not pan-CDK inhibition abrogates 5-FU-driven tissue factor upregulation in colon cancer

Thromboembolic events are complications in cancer patients and hypercoagulability has been linked to the tissue factor (TF) pathway, making this an attractive target. Here, we investigated the effects of chemotherapeutics and CDK inhibitors (CDKI) abemaciclib/palbociclib (CDK4/6), THZ-1 (CDK7/12/13), and dinaciclib (CDK1/2/5/9) alone and in combination regimens on TF abundance and coagulation. The human colorectal cancer (CRC) cell line HROC173 was treated with 5-FU or gemcitabine to stimulate TF expression. TF+ cells were sorted, recultured, and re-analyzed. The effect of treatment alone or in combination was assessed by functional assays. Low-dose chemotherapy induced a hypercoagulable state and significantly upregulated TF, even after reculture without treatment. Cells exhibited characteristics of epithelial-mesenchymal transition, including high expression of vimentin and mucin. Dinaciclib and THZ-1 also upregulated TF, while abemaciclib and palbociclib downregulated it. Similar results were observed in coagulation assays. The same anticoagulant activity of abemaciclib was seen after incubation with peripheral immune cells from healthy donors and CRC patients. Abemaciclib reversed 5-FU-induced TF upregulation and prolonged clotting times in second-line treatment. Effects were independent of cytotoxicity, senescence, and p27kip1 induction. TF-antibody blocking experiments confirmed the importance of TF in plasma coagulation, with Factor XII playing a minor role. Short-term abemaciclib counteracts 5-FU-induced hypercoagulation and eventually even prevents thromboembolic events.

Extracellular vesicles in neuroblastoma: role in progression, resistance to therapy and diagnostics

Neuroblastoma (NB) is the most common extracranial solid pediatric cancer, and is one of the leading causes of cancer-related deaths in children. Despite the current multi-modal treatment regimens, majority of patients with advanced-stage NBs develop therapeutic resistance and relapse, leading to poor disease outcomes. There is a large body of knowledge on pathophysiological role of small extracellular vesicles (EVs) in progression and metastasis of multiple cancer types, however, the importance of EVs in NB was until recently not well understood. Studies emerging in the last few years have demonstrated the involvement of EVs in various aspects of NB pathogenesis. In this review we summarize these recent findings and advances on the role EVs play in NB progression, such as tumor growth, metastasis and therapeutic resistance, that could be helpful for future investigations in NB EV research. We also discuss different strategies for therapeutic targeting of NB-EVs as well as utilization of NB-EVs as potential biomarkers.

Isolation and Enrichment of Extracellular Vesicles with Double-Positive Membrane Protein for Subsequent Biological Studies

The isolation and enrichment of specific extracellular vesicle (EV) subpopulations are essential in the context of precision medicine. However, the current methods predominantly rely on a single-positive marker and are susceptible to interference from soluble proteins or impurities. This limitation represents a significant obstacle to the widespread application of EVs in biological research. Herein, a novel approach that utilizes proximity ligation assay (PLA) and DNA-RNA hybridization are proposed to facilitate the binding of two proteins on the EV membrane in advance enabling the isolation and enrichment of intact EVs with double-positive membrane proteins followed by using functionalized magnetic beads for capture and enzymatic cleavage for isolated EVs release. The isolated subpopulations of EVs can be further utilized for cellular uptake studies, high-throughput small RNA sequencing, and breast cancer diagnosis. Hence, developing and implementing a specialized system for isolating and enriching a specific subpopulation of EVs can enhance basic and clinical research in this field.

Extracellular vesicle-mediated communication between CD8+ cytotoxic T cells and tumor cells

Tumors pose a significant global public health challenge, resulting in numerous fatalities annually. CD8+ T cells play a crucial role in combating tumors; however, their effectiveness is compromised by the tumor itself and the tumor microenvironment (TME), resulting in reduced efficacy of immunotherapy. In this dynamic interplay, extracellular vesicles (EVs) have emerged as pivotal mediators, facilitating direct and indirect communication between tumors and CD8+ T cells. In this article, we provide an overview of how tumor-derived EVs directly regulate CD8+ T cell function by carrying bioactive molecules they carry internally and on their surface. Simultaneously, these EVs modulate the TME, indirectly influencing the efficiency of CD8+ T cell responses. Furthermore, EVs derived from CD8+ T cells exhibit a dual role: they promote tumor immune evasion while also enhancing antitumor activity. Finally, we briefly discuss current prevailing approaches that utilize functionalized EVs based on tumor-targeted therapy and tumor immunotherapy. These approaches aim to present novel perspectives for EV-based tumor treatment strategies, demonstrating potential for advancements in the field.

MicroRNAs as regulators of immune checkpoints in cancer immunotherapy: targeting PD-1/PD-L1 and CTLA-4 pathways

Immunotherapy has revolutionized cancer treatment by harnessing the power of the immune system to eliminate tumors. Immune checkpoint inhibitors (ICIs) block negative regulatory signals that prevent T cells from attacking cancer cells. Two key ICIs target the PD-1/PD-L1 pathway, which includes programmed death-ligand 1 (PD-L1) and its receptor programmed death 1 (PD-1). Another ICI targets cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). While ICIs have demonstrated remarkable efficacy in various malignancies, only a subset of patients respond favorably. MicroRNAs (miRNAs), small non-coding RNAs that regulate gene expression, play a crucial role in modulating immune checkpoints, including PD-1/PD-L1 and CTLA-4. This review summarizes the latest advancements in immunotherapy, highlighting the therapeutic potential of targeting PD-1/PD-L1 and CTLA-4 immune checkpoints and the regulatory role of miRNAs in modulating these pathways. Consequently, understanding the complex interplay between miRNAs and immune checkpoints is essential for developing more effective and personalized immunotherapy strategies for cancer treatment.

S100A9+CD14+ monocytes contribute to anti-PD-1 immunotherapy resistance in advanced hepatocellular carcinoma by attenuating T cell-mediated antitumor function

BACKGROUND

The paucity of reliable biomarkers for predicting immunotherapy efficacy in patients with advanced hepatocellular carcinoma (HCC) has emerged as a burgeoning concern with the expanding use of immunotherapy. This study endeavors to delve into the potential peripheral biomarkers capable of prognosticating efficacy in HCC patients who are poised to receive anti-PD-1 monotherapy within the phase III clinical trial, KEYNOTE394. Additionally, we sought to elucidate the underlying molecular mechanisms for resistance to immune checkpoint blockade (ICB) and propose innovative combination immunotherapy strategies for future clinical application.

METHODS

Patient blood samples were collected for single-cell RNA sequencing to evaluate the immune cell signature before receiving ICB therapy. Subsequently, in vitro assays and in vivo murine model experiments were conducted to validate the mechanism that S100A9+CD14+ monocytes play a role in ICB resistance.

RESULTS

Our study demonstrates a notable enrichment of S100A9+CD14+ monocytes in the peripheral blood of patients exhibiting suboptimal responses to anti-PD-1 therapy. Moreover, we identified the Mono_S100A9 signature as a predictive biomarker, indicative of reduced efficacy in immunotherapy and decreased survival benefits across various tumor types. Mechanistically, S100A9 activates PD-L1 transcription by directly binding to the CD274 (PD-L1) gene promoter, thereby suppressing T-cell proliferation and cytotoxicity via the PD-1/PD-L1 axis, consequently diminishing the therapeutic effectiveness of subsequent anti-PD-1 treatments. Furthermore, our in vivo studies revealed that inhibiting S100A9 can synergistically enhance the efficacy of anti-PD-1 drugs in the eradication of hepatocellular carcinoma.

CONCLUSIONS

Our study underscores the significance of S100A9+CD14+ monocytes in predicting inadequate response to ICB treatment and provides insights into the monocyte cell-intrinsic mechanisms of resistance to ICB therapy. We also propose a combined therapeutic approach to enhance ICB efficacy by targeting S100A9.

Exosomal miR-3174 induced by hypoxia promotes angiogenesis and metastasis of hepatocellular carcinoma by inhibiting HIPK3

Hepatocellular carcinoma (HCC) is a highly malignant tumor with rich blood supply. HCC-derived exosomes containing hereditary substances including microRNAs (miRNAs) were involved in regulating tumor angiogenesis and metastasis. Subsequently, series experiments were performed to evaluate the effect of exosomal miR-3174 on HCC angiogenesis and metastasis. HCC-derived exosomal miR-3174 was ingested by human umbilical vein endothelial cells (HUVECs) in which HIPK3 was targeted and silenced, causing subsequent inhibition of Fas and p53 signaling pathways. Furthermore, exosomal miR-3174 induced permeability and angiogenesis of HUVECs to enhance HCC progression and metastasis. Under hypoxia, upregulated HIF-1α further promoted the transcription of miR-3174. Moreover, HNRNPA1 augmented the package of miR-3174 into exosomes. Clinical data analysis confirmed that HCC patients with high-level miR-3174 were correlated with worse prognosis. Thus, exosomal miR-3174 induced by hypoxia promotes angiogenesis and metastasis of HCC by inhibiting HIPK3/p53 and HIPK3/Fas signaling pathways. Our findings might provide potential targets for anti-tumor therapy.

Unveiling the immune symphony: decoding colorectal cancer metastasis through immune interactions

Colorectal cancer (CRC), known for its high metastatic potential, remains a leading cause of cancer-related death. This review emphasizes the critical role of immune responses in CRC metastasis, focusing on the interaction between immune cells and tumor microenvironment. We explore how immune cells, through cytokines, chemokines, and growth factors, contribute to the CRC metastasis cascade, underlining the tumor microenvironment's role in shaping immune responses. The review addresses CRC's immune evasion tactics, especially the upregulation of checkpoint inhibitors like PD-1 and CTLA-4, highlighting their potential as therapeutic targets. We also examine advanced immunotherapies, including checkpoint inhibitors and immune cell transplantation, to modify immune responses and enhance treatment outcomes in CRC metastasis. Overall, our analysis offers insights into the interplay between immune molecules and the tumor environment, crucial for developing new treatments to control CRC metastasis and improve patient prognosis, with a specific focus on overcoming immune evasion, a key aspect of this special issue.

Macrophage heterogeneity and its interactions with stromal cells in tumour microenvironment

Macrophages and tumour stroma cells account for the main cellular components in the tumour microenvironment (TME). Current advancements in single-cell analysis have revolutionized our understanding of macrophage diversity and macrophage-stroma interactions. Accordingly, this review describes new insight into tumour-associated macrophage (TAM) heterogeneity in terms of tumour type, phenotype, metabolism, and spatial distribution and presents the association between these factors and TAM functional states. Meanwhile, we focus on the immunomodulatory feature of TAMs and highlight the tumour-promoting effect of macrophage-tumour stroma interactions in the immunosuppressive TME. Finally, we summarize recent studies investigating macrophage-targeted therapy and discuss their therapeutic potential in improving immunotherapy by alleviating immunosuppression.

Tumour-associated macrophage-derived DOCK7-enriched extracellular vesicles drive tumour metastasis in colorectal cancer via the RAC1/ABCA1 axis

BACKGROUND

Metastasis accounts for the majority of deaths among patients with colorectal cancer (CRC). Here, the regulatory role of tumour-associated macrophages (TAMs) in CRC metastasis was explored.

METHODS

Immunohistochemical (IHC) analysis of the TAM biomarker CD163 was conducted to evaluate TAM infiltration in CRC. Transwell assays and an ectopic liver metastasis model were established to evaluate the metastatic ability of tumour cells. RNA sequencing (RNA-seq) and liquid chromatography-mass spectrometry (LC-MS) were applied to identify the differentially expressed genes and proteins in CRC cells and in TAM-derived extracellular vesicles (EVs). Cholesterol content measurement, a membrane fluidity assay and filipin staining were performed to evaluate cholesterol efflux in CRC cells.

RESULTS

Our results showed that TAM infiltration is positively correlated with CRC metastasis. TAMs can facilitate the migration and invasion of MC-38 and CT-26 cells via EVs. According to the RNA-seq data, TAM-EVs increase cholesterol efflux and enhance membrane fluidity in CRC cells by regulating ABCA1 expression, thus affecting the motility of CRC cells. Mechanistically, DOCK7 packaged in TAM-EVs can activate RAC1 in CRC cells and subsequently upregulate ABCA1 expression by phosphorylating AKT and FOXO1. Moreover, IHC analysis of ABCA1 in patients with liver-metastatic CRC indicated that ABCA1 expression is significantly greater in metastatic liver nodules than in primary CRC tumours.

CONCLUSIONS

Overall, our findings suggest that DOCK7 delivered via TAM-EVs could regulate cholesterol metabolism in CRC cells and CRC cell metastasis through the RAC1/AKT/FOXO1/ABCA1 axis. DOCK7 could thus be a new therapeutic target for controlling CRC metastasis.

Emerging Roles of Small Extracellular Vesicles in Gastrointestinal Cancer Research and Therapy

Discovered in the late eighties, sEVs are small extracellular nanovesicles (30-150 nm diameter) that gained increasing attention due to their profound roles in cancer, immunology, and therapeutic approaches. They were initially described as cellular waste bins; however, in recent years, sEVs have become known as important mediators of intercellular communication. They are secreted from cells in substantial amounts and exert their influence on recipient cells by signaling through cell surface receptors or transferring cargos, such as proteins, RNAs, miRNAs, or lipids. A key role of sEVs in cancer is immune modulation, as well as pro-invasive signaling and formation of pre-metastatic niches. sEVs are ideal biomarker platforms, and can be engineered as drug carriers or anti-cancer vaccines. Thus, sEVs further provide novel avenues for cancer diagnosis and treatment. This review will focus on the role of sEVs in GI-oncology and delineate their functions in cancer progression, diagnosis, and therapeutic use.

Mutual regulation of PD-L1 immunosuppression between tumor-associated macrophages and tumor cells: a critical role for exosomes

Tumor cells primarily employ the PD-1/PD-L1 pathway to thwart the anti-tumor capabilities of T lymphocytes, inducing immunosuppression. This occurs through the direct interaction of PD-L1 with PD-1 on T lymphocyte surfaces. Recent research focusing on the tumor microenvironment has illuminated the pivotal role of immune cells, particularly tumor-associated macrophages (TAMs), in facilitating PD-L1-mediated immunosuppression. Exosomes, characterized by their ability to convey information and be engulfed by cells, significantly contribute to promoting TAM involvement in establishing PD-L1-mediated immunosuppression within the tumor microenvironment. Exosomes, characterized by their ability to convey information and be engulfed by cells, significantly contribute to promoting TAM involvement in establishing PD-L1-mediated immunosuppression within the tumor microenvironment. In addition to receiving signals from tumor-derived exosomes that promote PD-L1 expression, TAMs also exert control over PD-L1 expression in tumor cells through the release of exosomes. This paper aims to summarize the mechanisms by which exosomes participate in this process, identify crucial factors that influence these mechanisms, and explore innovative strategies for inhibiting or reversing the tumor-promoting effects of TAMs by targeting exosomes.

Molecular and immunological characteristics of patients with CMTM6 low expression colorectal cancer

CKLF-like MARVEL transmembrane domain-containing 6 (CMTM6), a regulator of programmed cell death ligand 1 (PD-L1), has attracted extensive attention due to its role in tumors. However, research on the expression of CMTM6 in colorectal cancer (CRC) and its relationship with PD-L1 expression and immune cell infiltration is limited. We used The Cancer Genome Atlas database to mine and analyze data from patients with CRC using bioinformatics methods. We investigated the expression of CMTM6 in CRC and its relationship with PD-L1 expression and immune cell infiltration. Immunohistochemistry and PCR were performed to detect CMTM6 and PD-L1 expression in CRC tissues. Differential gene expression analysis was performed using the edgeR package in R and immune cell infiltration analysis was performed using the ssGSEA algorithm. Additionally, GO and KEGG enrichment analyses were conducted to identify the biological processes and pathways associated with low CMTM6 expression. Our study found that CMTM6 expression was significantly upregulated in CRC tissues compared to that in adjacent normal tissues. Patients with high CMTM6 expression exhibited significantly increased levels of PD-L1 expression and higher levels of tumor-infiltrating immune cells compared to patients with low CMTM6 expression. GO and KEGG analyses suggested that CMTM6 may be involved in multiple immune regulatory pathways in CRC.

Lactate-Induced CCL8 in Tumor-Associated Macrophages Accelerates the Progression of Colorectal Cancer through the CCL8/CCR5/mTORC1 Axis

Tumor-associated macrophages (TAMs) play a pivotal role in shaping the tumor microenvironment. Lactic acid (LA) has been identified as an influential factor in promoting immune escape and tumor progression. However, the mechanisms through which LA modulates TAMs in colorectal cancer (CRC) remain poorly understood. We used qRT-PCR to quantify the expression of LA-related genes (LDHA and LAMP2) in CRC tumor tissues and adjacent nontumor tissues (n = 64). The biological effects and mechanisms of LA on macrophages and tumors were evaluated via qRT-PCR, Western blot, RNA-seq, wound healing assay, colony formation assay in vitro, and allograft mouse tumor models in vivo. We found the expression of LDHA and LAMP2 was highly elevated in the tumor regions and positively associated with a poor clinical stage of CRC. A high concentration of LA was generated under hypoxia; it could promote tumor progression and metastasis with the involvement of macrophages. The inhibition of LA release impaired this protumor phenomenon. Mechanically, LA induced M2 macrophages through the AKT/ERK signaling pathway; subsequently, M2 macrophages secreted CCL8 and facilitated the proliferation and metastasis of CRC cells by activating the CCL8/CCR5/mTORC1 axis. This effect was inhibited by the antagonist or knockdown of CCR5. In conclusion, lactate-induced CCL8 in TAMs accelerated CRC proliferation and metastasis through the CCL8/CCR5/mTORC1 axis.

Exosomal EIF5A derived from Lewis lung carcinoma induced adipocyte wasting in cancer cachexia

Cancer cachexia is a systemic inflammation-driven syndrome, characterized by muscle atrophy and adipose tissue wasting, with progressive weight loss leading to serious impairment of physiological function. Extracellular vesicles (EVs) derived from cancer cells play a significant role in adipocyte lipolysis, yet the mechanism remain uneclucidated. In this study, EVs derived from Lewis lung carcinoma (LLC) cells were extracted and characterized. 3T3-L1 and HIB1B adipocytes were cultured with conditioned medium or EVs from LLC, and LLC cells were used to establish a cancer cachexia mouse model. EVs derived from LLC cells were taken up by 3T3-L1 and HIB1B adipocytes, and derived exosomal EIF5A protein-induced lipolysis of adipocytes. High level of EIF5A was expressed in EVs from LLC cells, exosomal EIF5A is linked to lipid metabolism. Elevated expression of EIF5A is associated with shorter overall survival in lung cancer patients. Western blots, glycerol release and Oil red O staining assays were used to evaluate lipolysis of adipocytes. The reduction of lipolysis in 3T3-L1 and HIB1B adipocytes is achieved through silencing EIF5A or treating with pharmacologic inhibitor GC7 in vitro, and suppressing the expression of EIF5A in LLC cells by infected with shRNA or GC7 treatment partly alleviated white and brown adipose tissue lipolysis in vivo. Mechanistically, EIF5A directly binds with G protein-coupled bile acid receptor 1 (GPBAR1) mRNA to promote its translation and then activates cAMP response element binding protein (CREB) signaling pathway to induce lipolysis. This study demonstrates that exosomal EIF5A from LLC cells, with hypusinated EIF5A, has a lipolytic effect on adipocyte and adipose tissues in cancer cachexia model. Exosomal EIF5A could be involved in lipolysis and these findings indicate that a novel regulator and potential target for cachexia treatment.

An off-the-shelf small extracellular vesicle nanomedicine for tumor targeting therapy

Small extracellular vesicles (sEVs) have shown excellent prospects as drug delivery systems for cancer therapy. However, the inherent non-targeting and short blood circulation characteristics severely restrict their practical applications as a delivery system. In addition, post-encapsulating drugs into sEVs also remains challenging. Here, we constructed an engineered cell line that secreted multifunctional sEVs (termed NBsEV204) with 7D12 (an anti-EGFR nanobody) and hCD47 decorations on their surface, as well as high levels of miR-204-5p encapsulation. NBsEV204 exhibited extended blood circulation and improved macrophage-mediated phagocytosis of tumor cells by blocking CD47 signaling. Importantly, NBsEV204 specifically targeted EGFR+ tumor cells and showed robust tumor-suppressive effects both in vitro and in vivo. Overall, this study provides a convenient and feasible method to produce off-the-shelf anticancer sEV nanomedicine, which exhibits tremendous potential for clinical translation.

Application of exosomal miRNA mediated macrophage polarization in colorectal cancer: Current progress and challenges

Colorectal cancer (CRC) is a major global health problem with high morbidity and mortality rates. Surgical resection is the main treatment for early-stage CRC, but detecting it early is challenging. Therefore, effective therapeutic targets for advanced patients are still lacking. Exosomes, tiny vesicles in body fluids, play a crucial role in tumor metastasis, immune regulation, and drug resistance. Interestingly, they can even serve as a biomarker for cancer diagnosis and prognosis. Studies have shown that exosomes can carry miRNA, mediate the polarization of M1/M2 macrophages, promote the proliferation and metastasis of cancer cells, and affect the prognosis of CRC. Since the gastrointestinal tract has many macrophages, understanding the mechanism behind exosomal miRNA-mediated macrophage polarization in CRC treatment is crucial. This article summarizes recent advancements in the study of exosomal miRNAs in CRC and their potential as diagnostic and prognostic markers.

The complementary roles of STAT3 and STAT1 in cancer biology: insights into tumor pathogenesis and therapeutic strategies

STATs are a family of transcription factors that regulate many critical cellular processes such as proliferation, apoptosis, and differentiation. Dysregulation of STATs is frequently observed in tumors and can directly drive cancer pathogenesis. STAT1 and STAT3 are generally viewed as mediating opposite roles in cancer development, with STAT1 suppressing tumorigenesis and STAT3 promoting oncogenesis. In this review, we investigate the specific roles of STAT1 and STAT3 in normal physiology and cancer biology, explore their interactions with each other, and offer insights into therapeutic strategies through modulating their transcriptional activity.

Curcumin inhibits malignant behavior of colorectal cancer cells by regulating M2 polarization of tumor-associated macrophages and metastasis associated in colon cancer 1 (MACC1) expression

The present study was to investigate the underlying mechanism of the antitumor effect of curcumin in colorectal cancer cells, focusing on the M2 polarization of tumor-associated macrophages (TAMs). The effect of curcumin on the malignant behavior of colorectal cancer cells was investigated by WST assay for cell growth, and Transwell assay for cell migration/invasion. THP-1 cells were differentiated into macrophages and coculture with colorectal cancer cells to study the influence of curcumin on M2 polarization, presenting as the levels of ARG1 mRNA, IL-10, and CD163-positive cells. GEO database was searched for the shared altered gene of curcumin in colorectal cells and human monocytes. Molecular docking was used to visualize the binding between curcumin and MACC1. Curcumin restricted the proliferation, apoptosis, and migration/invasion of HCT 116 and SW620 cells. Curcumin attenuated levels of the M2 macrophage markers, CD163 + cells, IL-10 secretion, and ARG1 mRNA. MACC1 was a target of curcumin in colorectal cancer cells, relating to macrophage. Rescue experiments showed that MACC1 overexpression can reverse the antitumor effect of curcumin in colorectal cancer cells and M2 polarization of TAMs. Curcumin's antiproliferative and anti-migratory effects in colorectal cancer cells may be mediated by MACC1 and inhibition of M2 polarization of TAMs.

Unraveling dynamic interactions between tumor-associated macrophages and consensus molecular subtypes in colorectal cancer: An integrative analysis of single-cell and bulk RNA transcriptome

Background

Accumulating research substantiated that tumor-associated macrophages (TAMs) have a significant impact on the tumorigenesis, progression, and distant metastasis, representing a novel target for various cancers. However, the underlying dynamic changes and interactions between TAMs and tumor cells remain largely elusive in colorectal cancer (CRC).

Methods

We depicted the dynamic changes of macrophages using sing-cell RNA-seq data and extracted TAM differentiation-related genes. Next, we utilized the weighted gene co-expression network analysis (WGCNA) to acquire CMS-related modular genes using bulk RNA-seq data. Finally, we utilized univariate Cox and Lasso Cox regression analyses to identify TAM differentiation-related biomarkers and established a novel risk signature model. We employed quantitative real-time polymerase chain reaction (qRT-PCR) on CRC tissue samples and used immunohistochemistry (IHC) data frome the HPA database to validate the mRNA and protein expression of prognostic genes. The interaction of TAMs and each consensus molecular subtype (CMS) subpopulation was analyzed at the cellular level.

Results

A total of 47,285 cells from single-cell dataset and 1197 CRC patients from bulk dataset were obtained. Among those, 6400 myeloid cells were re-clustered and annotated. RNASE1, F13A1, DAPK1, CLEC10A, RPN2, REG4 and RGS19 were identified as prognostic genes and the risk signature model was established based on the above genes. The qRT-PCR analysis indicated that the expression of RNASE1 and DAPK1 were significantly up-regulated in CRC tumor tissues. The cell-cell communication analysis demonstrated complex interactions between TAMs and CMS malignant cell subpopulations.

Conclusion

This study presents an in-depth dissection of the dynamic features of TAMs in the tumor microenvironment and provides promising therapeutic targets for CRC.

Extracellular vesicles and particles as mediators of long-range communication in cancer: connecting biological function to clinical applications

Over the past decade, extracellular vesicles and particles (EVPs) have emerged as critical mediators of intercellular communication, participating in numerous physiological and pathological processes. In the context of cancer, EVPs exert local effects, such as increased invasiveness, motility, and reprogramming of tumor stroma, as well as systemic effects, including pre-metastatic niche formation, determining organotropism, promoting metastasis and altering the homeostasis of various organs and systems, such as the liver, muscle, and circulatory system. This review provides an overview of the critical advances in EVP research during the past decade, highlighting the heterogeneity of EVPs, their roles in intercellular communication, cancer progression, and metastasis. Moreover, the clinical potential of systemic EVPs as useful cancer biomarkers and therapeutic agents is explored. Last but not least, the progress in EVP analysis technologies that have facilitated these discoveries is discussed, which may further propel EVP research in the future.

Regulatory role of exosomes in colorectal cancer progression and potential as biomarkers

Colorectal cancer (CRC) remains an enormous challenge to human health worldwide. Unfortunately, the mechanism underlying CRC progression is not well understood. Mounting evidence has confirmed that exosomes play a vital role in CRC progression, which has attracted extensive attention among researchers. In addition to acting as messengers between CRC cells, exosomes also participate in the CRC immunomodulatory process and reshape immune function. As stable message carriers and liquid biopsy option under development, exosomes are promising biomarkers in the diagnosis or treatment of CRC. In this review we have described and analyzed the biogenesis and release of exosomes and current research on the role of exosomes in immune regulation and metastasis of CRC. Moreover, we have discussed candidate exosomal molecules as potential biomarkers to diagnose CRC, predict CRC progression, or determine CRC chemoresistance, and described the significance of exosomes in the immunotherapy of CRC. This review provides insight to further understand the role of exosomes in CRC progression and identify valuable biomarkers that facilitate the clinical management of CRC patients.

Tumor-derived small extracellular vesicles promote breast cancer progression by upregulating PD-L1 expression in macrophages

BACKGROUND

The metastasis of breast cancer (BC) is a complex multi-step pathological process, strictly dependent on the intrinsic characteristics of BC cells and promoted by a predisposing microenvironment. Although immunotherapy has made important progress in metastasis BC, the heterogeneity of PD-L1 in tumor associated macrophages (TAMs) in BC and the underlying mechanisms in the metastasis development of BC are still not completely elucidated. Small extracellular vesicles (sEVs) represent essential interaction mediators between BC cells and TAMs. It is worth noting to explore the underlying mechanisms typical of sEVs and their role in the metastasis development of BC.

METHODS

The structure of sEVs was identified by TEM, while the particle size and amounts of sEVs were detected by BCA and NTA analysis. The specific PD-L1 + CD163 + TAM subpopulation in metastasis BC was identified by scRNA-seq data of GEO datasets and verified by IHC and IF. The function of TAMs and sEVs in metastasis BC was explored by RT-qPCR, WB, IF, flow cytometry and in vivo experiment. The expression profiles of plasma sEVs-miRNA in relation to BC metastasis was analyzed using next-generation sequencing. Further detailed mechanisms of sEVs in the metastasis development of BC were explored by bioinformatics analysis, RT-qPCR, WB and luciferase reporter assay.

RESULTS

In this study, we identified that the immunosuppressive molecule PD-L1 was more abundant in TAMs than in BC cells, and a specific PD-L1 + CD163 + TAM subpopulation was found to be associated with metastasis BC. Additionally, we found that BC cells-derived sEVs can upregulate the PD-L1 expression and induce the M2 polarization, enhancing the metastasis development both in vitro and in vivo. Also, Clinical data showed that sEV-miR-106b-5p and sEV-miR-18a-5p was in relation to BC metastasis development and poor prognosis of BC patients. Further mechanistic experiments revealed that BC-derived sEV-miR-106b-5p and sEV-miR-18a-5p could synergistically promoted the PD-L1 expression in M2 TAMs by modulating the PTEN/AKT and PIAS3/STAT3 pathways, resulting in the enhancement of the BC cells invasion and metastasis.

CONCLUSIONS

Our study demonstrated that BC-derived sEVs can induce metastasis in BC through miR-106b-5p/PTEN/AKT/PD-L1 and miR-18a-5p/PIAS3/STAT3/PD-L1 pathways in TAMs. Therefore, the inhibition of these specific interactions of signaling pathways would represent a promising target for future therapeutic strategies for treatment of BC.

Progress of regulatory RNA in small extracellular vesicles in colorectal cancer

Colorectal cancer (CRC) is the second most common malignant tumor of the gastrointestinal tract with the second highest mortality rate and the third highest incidence rate. Early diagnosis and treatment are important measures to reduce CRC mortality. Small extracellular vesicles (sEVs) have emerged as key mediators that facilitate communication between tumor cells and various other cells, playing a significant role in the growth, invasion, and metastasis of cancer cells. Regulatory RNAs have been identified as potential biomarkers for early diagnosis and prognosis of CRC, serving as crucial factors in promoting CRC cell proliferation, invasion and metastasis, angiogenesis, drug resistance, and immune cell differentiation. This review provides a comprehensive summary of the vital role of sEVs as biomarkers in CRC diagnosis and their potential application in CRC treatment, highlighting their importance as a promising avenue for further research and clinical translation.

Innate Immune Cells in the Tumor Microenvironment of Liver Metastasis from Colorectal Cancer: Contribution to a Comprehensive Therapy

Colorectal cancer (CRC) is the third most prevalent type of cancer, and liver metastasis is the most common site of metastatic development. In the tumor microenvironment (TME), various innate immune cells are known to influence cancer progression and metastasis occurrence. CD274 (PD-L1) and CD206 (MRC1) are proteins that have been associated with poor prognosis and disease progression. We conducted a study on tumoral and non-tumoral biopsies from 47 patients with CRC liver metastasis, using flow cytometry to phenotypically characterize innate immune cells. Our findings showed an increase in the expression of CD274 on classical, intermediate, and non-classical monocytes when comparing tumor with non-tumor samples. Furthermore, tumor samples with a desmoplastic growth pattern exhibited a significantly decreased percentage of CD274- and CD206-positive cells in all monocyte populations compared to non-desmoplastic samples. We found a correlation between a lower expression of CD206 or CD274 on classical, intermediate, and non-classical monocytes and increased disease-free survival, which points to a better prognosis for these patients. In conclusion, our study has identified potential new targets and biomarkers that could be incorporated into a personalized medicine approach to enhance the outcome for colorectal cancer patients.

Macrophages in immunoregulation and therapeutics

Macrophages exist in various tissues, several body cavities, and around mucosal surfaces and are a vital part of the innate immune system for host defense against many pathogens and cancers. Macrophages possess binary M1/M2 macrophage polarization settings, which perform a central role in an array of immune tasks via intrinsic signal cascades and, therefore, must be precisely regulated. Many crucial questions about macrophage signaling and immune modulation are yet to be uncovered. In addition, the clinical importance of tumor-associated macrophages is becoming more widely recognized as significant progress has been made in understanding their biology. Moreover, they are an integral part of the tumor microenvironment, playing a part in the regulation of a wide variety of processes including angiogenesis, extracellular matrix transformation, cancer cell proliferation, metastasis, immunosuppression, and resistance to chemotherapeutic and checkpoint blockade immunotherapies. Herein, we discuss immune regulation in macrophage polarization and signaling, mechanical stresses and modulation, metabolic signaling pathways, mitochondrial and transcriptional, and epigenetic regulation. Furthermore, we have broadly extended the understanding of macrophages in extracellular traps and the essential roles of autophagy and aging in regulating macrophage functions. Moreover, we discussed recent advances in macrophages-mediated immune regulation of autoimmune diseases and tumorigenesis. Lastly, we discussed targeted macrophage therapy to portray prospective targets for therapeutic strategies in health and diseases.

Tumor Cell-derived Extracellular Vesicles in Modulating Phenotypes and Immune Functions of Macrophages: Mechanisms and Therapeutic Applications

Tumor tissues consist of tumor cells and tumor stroma, which is structured by non-tumor cells and the extracellular matrix. Macrophages are the predominant immune cells in the tumor microenvironment (TME). Based on the intimate interaction between macrophages and tumor cells, macrophages are closely involved in tumor initiation and progression, playing a key role in tumor formation, angiogenesis, metastasis, and immune escape. Extracellular vesicles (EVs) are a group of membrane-enclosed structures secreted by almost all cell types. As crucial mediators of cell-to-cell communication, EVs play a role in various physiological processes and the development of diseases including cancer. According to numerous studies, tumor cell-derived extracellular vesicles (T-EVs) could highly modulate the phenotypes and functions of macrophages, thus promoting tumor development. Herein, we comprehensively introduce the role of T-EVs in regulating the M1/M2 phenotypes and immune functions of macrophages, including cytokine secretion, expression of immune regulatory molecules on the membrane, phagocytosis, and antigen presentation. More importantly, based on the regulatory effects of T-EVs on macrophages, we propose several potential therapeutic approaches that may guide future attempts to increase the effectiveness of cancer therapy.

The application of extracellular vesicles in colorectal cancer metastasis and drug resistance: recent advances and trends

Colorectal cancer (CRC) has high incidence and mortality rates and is one of the most common cancers of the digestive tract worldwide. Metastasis and drug resistance are the main causes of cancer treatment failure. Studies have recently suggested extracellular vesicles (EVs) as a novel mechanism for intercellular communication. They are vesicular particles, which are secreted and released into biological fluids, such as blood, urine, milk, etc., by a variety of cells and carry numerous biologically active molecules, including proteins, nucleic acids, lipids, metabolites, etc. EVs play a crucial part in the metastasis and drug resistance of CRC by delivering cargo to recipient cells and modulating their behavior. An in-depth exploration of EVs might facilitate a comprehensive understanding of the biological behavior of CRC metastasis and drug resistance, which might provide a basis for developing therapeutic strategies. Therefore, considering the specific biological properties of EVs, researchers have attempted to explore their potential as next-generation delivery systems. On the other hand, EVs have also been demonstrated as biomarkers for the prediction, diagnosis, and presumed prognosis of CRC. This review focuses on the role of EVs in regulating the metastasis and chemoresistance of CRC. Moreover, the clinical applications of EVs are also discussed.

Interplay between Signaling Pathways and Tumor Microenvironment Components: A Paradoxical Role in Colorectal Cancer

The study of the tumor microenvironment (TME) has become an important part of colorectal cancer (CRC) research. Indeed, it is now accepted that the invasive character of a primary CRC is determined not only by the genotype of the tumor cells, but also by their interactions with the extracellular environment, which thereby orchestrates the development of the tumor. In fact, the TME cells are a double-edged sword as they play both pro- and anti-tumor roles. The interaction of the tumor-infiltrating cells (TIC) with the cancer cells induces the polarization of the TIC, exhibiting an antagonist phenotype. This polarization is controlled by a plethora of interconnected pro- and anti-oncogenic signaling pathways. The complexity of this interaction and the dual function of these different actors contribute to the failure of CRC control. Thus, a better understanding of such mechanisms is of great interest and provides new opportunities for the development of personalized and efficient therapies for CRC. In this review, we summarize the signaling pathways linked to CRC and their implication in the development or inhibition of the tumor initiation and progression. In the second part, we enlist the major components of the TME and discuss the complexity of their cells functions.

Exosome-derived miRNAs regulate macrophage-colorectal cancer cell cross-talk during aggressive tumor development

Colorectal cancer is one of the leading causes of death worldwide. Its incidence and mortality have significantly increased during the past few years. Colorectal cancer cells cross-talk with other cells through exosomes in their tumor microenvironment. The miRNAs containing exosomes are responsible for tumor growth, invasion, and metastasis. Multiple studies have shown that exosomal miRNAs are key players in the crosstalk between cancerous, immune, and stromal cells during colorectal cancer development. They help in the establishment of the tumorigenic microenvironment by reprogramming macrophages towards a pro-tumorigenic phenotype. In this review, we discussed various exosomal miRNAs derived both from colorectal cancer cells and macrophages that promote or inhibit cancer aggression. We also discussed various miRNA-based therapeutic approaches to inhibit cancer progression.

LINC00543 promotes colorectal cancer metastasis by driving EMT and inducing the M2 polarization of tumor associated macrophages

BACKGROUND

The interaction between the tumor-microenvironment (TME) and the cancer cells has emerged as a key player in colorectal cancer (CRC) metastasis. A small proportion of CRC cells which undergo epithelial-mesenchymal transition (EMT) facilitate the reshaping of the TME by regulating various cellular ingredients.

METHODS

Immunohistochemical analysis, RNA immunoprecipitation (RIP), RNA Antisense Purification (RAP), dual luciferase assays were conducted to investigate the biological function and regulation of LINC00543 in CRC. A series in vitro and in vivo experiments were used to clarify the role of LINC00543 in CRC metastasis.

RESULTS

Here we found that the long non-coding RNA LINC00543, was overexpressed in colorectal cancer tissues, which correlated with advanced TNM stage and poorer prognosis of CRC patients. The overexpression of LINC00543 promoted tumorigenesis and metastasis of CRC cells by enhancing EMT and remodeling the TME. Mechanistically, LINC00543 blocked the transport of pre-miR-506-3p across the nuclear-cytoplasmic transporter XPO5, thereby reducing the production of mature miR-506-3p, resulting in the increase in the expression of FOXQ1 and induction of EMT. In addition, upregulation of FOXQ1 induced the expression of CCL2 that accelerated the recruitment of macrophages and their M2 polarization.

CONCLUSIONS

Our study showed that LINC00543 enhanced EMT of CRC cells through the pre-miR-506-3p/FOXQ1 axis. This resulted in the upregulation of CCL2, leading to macrophages recruitment and M2 polarization, and ultimately stimulating the progression of CRC.

Extracellular Vesicles in Colorectal Cancer: From Tumor Growth and Metastasis to Biomarkers and Nanomedications

Colorectal cancer (CRC) is a leading public health concern due to its incidence and high mortality rates, highlighting the requirement of an early diagnosis. Evaluation of circulating extracellular vesicles (EVs) might constitute a noninvasive and reliable approach for CRC detection and for patient follow-up because EVs display the molecular features of the cells they originate. EVs are released by almost all cell types and are mainly categorized as exosomes originating from exocytosis of intraluminal vesicles from multivesicular bodies, ectosomes resulting from outward budding of the plasma membrane and apoptotic bodies' ensuing cell shrinkage. These vesicles play a critical role in intercellular communications during physiological and pathological processes. They facilitate CRC progression and premetastatic niche formation, and they enable transfer of chemotherapy resistance to sensitive cells through the local or remote delivery of their lipid, nucleic acid and protein content. On another note, their stability in the bloodstream, their permeation in tissues and their sheltering of packaged material make engineered EVs suitable vectors for efficient delivery of tracers and therapeutic agents for tumor imaging or treatment. Here, we focus on the physiopathological role of EVs in CRCs, their value in the diagnosis and prognosis and ongoing investigations into therapeutic approaches.

Tumor-derived miRNAs as tumor microenvironment regulators for synergistic therapeutic options

MicroRNAs (miRNAs) are a class of non-coding RNAs that perform post-transcriptional gene regulation. This review focuses on the role of tumor cell-derived miRNAs in the regulation of the tumor microenvironment (TME) via receptor cell recoding, including angiogenesis, expression of immunosuppressive molecules, formation of radiation resistance, and chemoresistance. Furthermore, we discuss the potential of these molecules as adjuvant therapies in combination with chemotherapy, radiotherapy, or immunotherapy, as well as their advantages as efficacy predictors for personalized therapy. MiRNA-based therapeutic agents for tumors are currently in clinical trials, and while challenges remain, additional research on tumor-derived miRNAs is warranted, which may provide significant clinical benefits to cancer patients.

The pleiotropic mode and molecular mechanism of macrophages in promoting tumor progression and metastasis

Macrophages are the most abundant immune cells in primary and metastatic tumor tissues. Studies have shown that macrophages mainly exhibit a tumor-promoting phenotype and play a key role in tumor progression and metastasis. Therefore, many macrophage-targeted drugs have entered clinical trials. However, compared to preclinical studies, some clinical trial results showed that macrophage-targeted therapy did not achieve the desired effect. This may be because most of what we know about macrophages comes from in vitro experiments and animal models, while macrophages in the more complex human microenvironment are still poorly understood. With the development of technologies such as single-cell RNA sequencing, we have gained a new understanding of the origin, classification and functional mechanism of tumor-associated macrophages. Therefore, this study reviewed the recent progress of macrophages in promoting tumor progression and metastasis, aiming to provide some help for the formulation of optimal strategies for macrophage-targeted therapy.

MicroRNA: role in macrophage polarization and the pathogenesis of the liver fibrosis

Macrophages, as central components of innate immunity, feature significant heterogeneity. Numerus studies have revealed the pivotal roles of macrophages in the pathogenesis of liver fibrosis induced by various factors. Hepatic macrophages function to trigger inflammation in response to injury. They induce liver fibrosis by activating hepatic stellate cells (HSCs), and then inflammation and fibrosis are alleviated by the degradation of the extracellular matrix and release of anti-inflammatory cytokines. MicroRNAs (miRNAs), a class of small non-coding endogenous RNA molecules that regulate gene expression through translation repression or mRNA degradation, have distinct roles in modulating macrophage activation, polarization, tissue infiltration, and inflammation regression. Considering the complex etiology and pathogenesis of liver diseases, the role and mechanism of miRNAs and macrophages in liver fibrosis need to be further clarified. We first summarized the origin, phenotypes and functions of hepatic macrophages, then clarified the role of miRNAs in the polarization of macrophages. Finally, we comprehensively discussed the role of miRNAs and macrophages in the pathogenesis of liver fibrotic disease. Understanding the mechanism of hepatic macrophage heterogeneity in various types of liver fibrosis and the role of miRNAs on macrophage polarization provides a useful reference for further research on miRNA-mediated macrophage polarization in liver fibrosis, and also contributes to the development of new therapies targeting miRNA and macrophage subsets for liver fibrosis.

Alarmin IL-33 orchestrates antitumoral T cell responses to enhance sensitivity to 5-fluorouracil in colorectal cancer

Rationale: Resistance to 5-fluorouracil (5-FU) chemotherapy remains the main barrier to effective clinical outcomes for patients with colorectal cancer (CRC). A better understanding of the detailed mechanisms underlying 5-FU resistance is needed to increase survival. Interleukin (IL)-33 is a newly discovered alarmin-like molecule that exerts pro- and anti-tumorigenic effects in various cancers. However, the precise role of IL-33 in CRC progression, as well as in the development of 5-FU resistance, remains unclear. Methods: High-quality RNA-sequencing analyses were performed on matched samples from patients with 5-FU-sensitive and 5-FU-resistant CRC. The clinical and biological significance of IL-33, including its effects on both T cells and tumor cells, as well as its relationship with 5-FU chemotherapeutic activity were examined in ex vivo, in vitro and in vivo models of CRC. The molecular mechanisms underlying these processes were explored. Results: IL-33 expressed by tumor cells was a dominant mediator of antitumoral immunity in 5-FU-sensitive patients with CRC. By binding to its ST2 receptor, IL-33 triggered CD4+ (Th1 and Th2) and CD8+ T cell responses by activating annexin A1 downstream signaling cascades. Mechanistically, IL-33 enhanced the sensitivity of CRC cells to 5-FU only in the presence of T cells, which led to the activation of both tumor cell-intrinsic apoptotic and immune killing-related signals, thereby synergizing with 5-FU to induce apoptosis of CRC cells. Moreover, injured CRC cells released more IL-33 and the T cell chemokines CXCL10 and CXCL13, forming a positive feedback loop to further augment T cell responses. Conclusions: Our results identified a previously unrecognized connection between IL-33 and enhanced sensitivity to 5-FU. IL-33 created an immune-active tumor microenvironment by orchestrating antitumoral T cell responses. Thus, IL-33 is a potential predictive biomarker for 5-FU chemosensitivity and favorable prognosis and has potential as a promising adjuvant immunotherapy to improve the clinical benefits of 5-FU-based therapies in the treatment of CRC.

Extremely high infiltration of CD8+PD-L1+ cells detected in a stage III non-small cell lung cancer patient exhibiting hyperprogression during anti-PD-L1 immunotherapy after chemoradiation: A case report

In recent years, immune checkpoint inhibitors (ICIs), represented by PD-1/PD-L1 monoclonal antibodies, have become a research hotspot in the field of oncology treatment. Immunotherapy has shown significant survival advantages in a variety of solid tumors. However, the phenomenon of hyperprogressive disease (HPD) in some patients treated with immunotherapy is gradually getting more attention and focus. An early understanding of the characteristics of HPD is crucial to optimize the treatment strategy. We report a patient with unresectable stage III lung adenocarcinoma who developed HPD with metastasis during consolidation therapy with durvalumab after chemoradiation. To further investigate the potential mechanism of HPD after anti-PD-L1 treatment, primary lung baseline tissue, baseline plasma, post-immunotherapy plasma, and liver metastasis samples of the patient were detected via next-generation sequencing (NGS). Then, multiplex immunohistochemistry (mIHC) was performed on primary lung baseline tissue and liver metastasis samples. KRAS and p.G12C were identified as the major driver mutation genes. With a low tumor mutation burden (TMB) value, the patient presented a very high percentage of CD8+PD-L1+ T cells that infiltrated in the baseline tissue, with 95.5% of all CD8+ cells expressing PD-L1 and a low percentage of CD8+ T cells expressing PD-1. After the emergence of HPD from immunotherapy, liver metastases were similarly infiltrated with an extremely high proportion of CD8+PD-L1+ T cells, with 85.6% of all CD8+ cells expressing PD-L1 and almost no CD8+ T cells expressing PD-1. The extreme infiltration of PD-L1+CD8+ T cells in the tumor microenvironment of baseline tissue might be associated with the aggressive tumor growth observed in anti-PD-L1 treatment for related HPD and could be a potential biomarker for HPD development.

Phospholipid-Membrane-Based Nanovesicles Acting as Vaccines for Tumor Immunotherapy: Classification, Mechanisms and Applications

Membrane vesicles, a group of nano- or microsized vesicles, can be internalized or interact with the recipient cells, depending on their parental cells, size, structure and content. Membrane vesicles fuse with the target cell membrane, or they bind to the receptors on the cell surface, to transfer special effects. Based on versatile features, they can modulate the functions of immune cells and therefore influence immune responses. In the field of tumor therapeutic applications, phospholipid-membrane-based nanovesicles attract increased interest. Academic institutions and industrial companies are putting in effort to design, modify and apply membrane vesicles as potential tumor vaccines contributing to tumor immunotherapy. This review focuses on the currently most-used types of membrane vesicles (including liposomes, bacterial membrane vesicles, tumor- and dendritic-cell-derived extracellular vesicles) acting as tumor vaccines, and describes the classification, mechanism and application of these nanovesicles.

Long Non-Coding RNA and microRNA Interplay in Colorectal Cancer and Their Effect on the Tumor Microenvironment

As the current staging and grading systems are not sufficient to stratify patients for therapy and predict the outcome of the disease, there is an urgent need to understand cancer in its complexity. The mutual relationship between tumour and immune or stromal cells leads to rapid evolution and subsequent genetic and epigenetic changes. Immunoscore has been introduced as a diagnostic tool for colorectal cancer (CRC) only recently, emphasising the role of the specific tumor microenvironment in patient's prognosis and overall outcome. Despite the fact that non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), cannot be translated into proteins, they significantly affect cell's transcriptome and translatome. miRNA binding to mRNA efficiently blocks its translation and leads to mRNA destruction. On the other hand, miRNAs can be bound by lncRNAs or circular RNAs (circRNAs), which prevents them from interfering with translation. In this way, ncRNAs create a multi-step network that regulates the cell's translatome. ncRNAs are also shed by the cell as exogenous RNAs and they are also found in exosomes, suggesting their role in intercellular communication. Hence, these mechanisms affect the tumor microenvironment as much as protein signal molecules. In this review, we provide an insight into the current knowledge of the microenvironment, lncRNAs', and miRNAs' interplay. Understanding mechanisms that underlie the evolution of a tissue as complex as a tumour is crucial for the future success in therapy.

Tumor extracellular vesicles mediate anti-PD-L1 therapy resistance by decoying anti-PD-L1

PD-L1⁺ tumor-derived extracellular vesicles (TEVs) cause systemic immunosuppression and possibly resistance to anti-PD-L1 antibody (αPD-L1) blockade. However, whether and how PD-L1⁺ TEVs mediate αPD-L1 therapy resistance is unknown. Here, we show that PD-L1⁺ TEVs substantially decoy αPD-L1 and that TEV-bound αPD-L1 is more rapidly cleared by macrophages, causing insufficient blockade of tumor PD-L1 and subsequent αPD-L1 therapy resistance. Inhibition of endogenous production of TEVs by Rab27a or Coro1a knockout reverses αPD-L1 therapy resistance. Either an increased αPD-L1 dose or macrophage depletion mediated by the clinical drug pexidartinib abolishes αPD-L1 therapy resistance. Moreover, in the treatment cycle with the same total treatment dose of αPD-L1, high-dose and low-frequency treatment had better antitumor effects than low-dose and high-frequency treatment, induced stronger antitumor immune memory, and eliminated αPD-L1 therapy resistance. Notably, in humanized immune system mice with human xenograft tumors, both increased αPD-L1 dose and high-dose and low-frequency treatment enhanced the antitumor effects of αPD-L1. Furthermore, increased doses of αPD-L1 and αPD-1 had comparable antitumor effects, but αPD-L1 amplified fewer PD-1⁺ Treg cells, which are responsible for tumor hyperprogression. Altogether, our results reveal a TEV-mediated mechanism of αPD-L1-specific therapy resistance, thus providing promising strategies to improve αPD-L1 efficacy.

Microbiota and Extracellular Vesicles in Anti-PD-1/PD-L1 Therapy

Simple Summary

Immune checkpoint inhibitors (ICI) targeting PD-1/PD-L1 have emerged as contemporary treatments for a variety of cancers. However, the efficacy of antibody-based ICIs could be further enhanced. Microbiota have been demonstrated to be among the vital factors governing cancer progression and response to therapy in patients. Bacteria secrete extracellular vesicles carrying bioactive metabolites within their cargo that can cross physiological barriers, selectively accumulate near tumor cells, and alter the tumor microenvironment. Extracellular vesicles, particularly those derived from bacteria, could thus be of promising assistance in refining the treatment outcomes for anti-PD-1/PD-L1 therapy. The potentiality of microbiota-derived extracellular vesicles in improving the currently used treatments and presenting new therapeutic avenues for cancer has been featured in this review.

Abstract

Cancer is a deadly disease worldwide. In light of the requisite of convincing therapeutic methods for cancer, immune checkpoint inhibition methods such as anti-PD-1/PD-L1 therapy appear promising. Human microbiota have been exhibited to regulate susceptibility to cancer as well as the response to anti-PD-1/PD-L1 therapy. However, the probable contribution of bacterial extracellular vesicles (bEVs) in cancer pathophysiology and treatment has not been investigated much. bEVs illustrate the ability to cross physiological barriers, assemble around the tumor cells, and likely modify the tumor microenvironment (EVs). This systematic review emphasizes the correlation between cancer-associated extracellular vesicles, particularly bEVs and the efficacy of anti-PD-1/PD-L1 therapy. The clinical and pharmacological prospective of bEVs in revamping the contemporary treatments for cancer has been further discussed.

Bladder Cancer-Derived Small Extracellular Vesicles Promote Tumor Angiogenesis by Inducing HBP-Related Metabolic Reprogramming and SerRS O-GlcNAcylation in Endothelial Cells

A malformed tumour vascular network provokes the nutrient-deprived tumour microenvironment (TME), which conversely activates endothelial cell (EC) functions and stimulates neovascularization. Emerging evidence suggests that the flexible metabolic adaptability of tumour cells helps to establish a metabolic symbiosis among various cell subpopulations in the fluctuating TME. In this study, the authors propose a novel metabolic link between bladder cancer (BCa) cells and ECs in the nutrient-scarce TME, in which BCa-secreted glutamine-fructose-6-phosphate aminotransferase 1 (GFAT1) via small extracellular vesicles (sEVs) reprograms glucose metabolism by increasing hexosamine biosynthesis pathway flux in ECs and thus enhances O-GlcNAcylation. Moreover, seryl-tRNA synthetase (SerRS) O-GlcNAcylation at serine 101 in ECs promotes its degradation by ubiquitination and impeded importin α5-mediated nuclear translocation. Intranuclear SerRS attenuates vascular endothelial growth factor transcription by competitively binding to the GC-rich region of the proximal promotor. Additionally, GFAT1 knockout in tumour cells blocks SerRS O-GlcNAcylation in ECs and attenuates angiogenesis both in vitro and in vivo. However, administration of GFAT1-overexpressing BCa cells-derived sEVs increase the angiogenetic activity in the ECs of GFAT1-knockout mice. In summary, this study suggests that inhibiting sEV-mediated GFAT1 secretion from BCa cells and targeting SerRS O-GlcNAcylation in ECs may serve as novel strategies for BCa antiangiogenetic therapy.