Tumor-derived exosomal circFARSA mediates M2 macrophage polarization via the PTEN/PI3K/AKT pathway to promote non-small cell lung cancer metastasis

Tumor-derived vesicles in immune modulation: focus on signaling pathways

Tumor-derived extracellular vesicles (TDEVs) represent a heterogeneous population of extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, which are essential for tumor growth. EVs function as natural carriers of bioactive molecules, including lipids, proteins, and nucleic acids, enabling them to influence and regulate complex cellular interactions within the tumor microenvironment (TME). The TDEVs mainly have immunosuppressive functions as a result of the inhibitory signals disrupting the immune cell anti-tumor activity. They enhance tumor progression and immune evasion by inhibiting the effector function of immune cells and by altering critical processes of immune cell recruitment, polarization, and functional suppression by different signaling pathways. In this sense, TDEVs modulate the NF-κB pathway, promoting inflammation and inducing immune evasion. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling is required for TDEV-mediated immune suppression and the manifestation of tumor-supporting features. The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling, necessary for metabolic reprogramming, is orchestrated by TDEV to abrogate immune response and drive cancer cell proliferation. Finally, exosomal cargo can modulate the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, activating pro-inflammatory responses that influence tumor development and immunomodulation. In this review, we take a deep dive into how TDEVs affect the immune cells by altering key signaling pathways. We also examine emerging therapeutic approaches aimed at disrupting EV-mediated pathways, offering promising avenues for the development of novel EV-based cancer immunotherapy.

Emerging roles of exosomal circRNAs in non-small cell lung cancer

Despite the prevalence of non-small cell lung cancer (NSCLC) is high, the limited early detection and management of these tumors are restricted since there is an absence of reliable and precise diagnostic biomarkers and therapeutic targets. Exosomes transport functional molecules for facilitating intercellular communication, especially in the tumor microenvironment, indicating their potential as cancer biomarkers and therapeutic targets. Circular RNA (circRNA), a type of non-coding RNA possessing a covalently closed loop structure, substantial abundance, and tissue-specific expression patterns, is stably enriched in exosomes. In recent years, significant breakthroughs have been made in research on exosomal circRNA in NSCLC. This review briefly introduces the biogenesis, characterizations, and functions of circRNAs and exosomes, and systematically describes the biological functions and mechanisms of exosomal circRNAs in NSCLC. In addition, this study summarizes their role in the progression of NSCLC and discusses their clinical significance as biomarkers and therapeutic targets for NSCLC.

The role and clinical significance of tumor-associated macrophages in the epithelial-mesenchymal transition of lung cancer

Lung cancer remains the leading cause of cancer-related mortality worldwide. Tumor-associated macrophages (TAMs) and epithelial-mesenchymal transition (EMT) are key drivers of lung cancer metastasis and drug resistance. M2-polarized TAMs dominate the immunosuppressive tumor microenvironment (TME) and promote EMT through cytokines such as TGF-β, IL-6, and CCL2. Conversely, EMT-transformed tumor cells reinforce TAM recruitment and M2 polarization through immunomodulatory factors such as CCL2 and ZEB1, thereby establishing a bidirectional interplay that fuels tumor progression. Current evidence on this interaction remains fragmented, and a comprehensive review of the TAM-EMT regulatory network and its therapeutic implications is lacking. This review systematically integrates the bidirectional regulatory mechanisms between TAMs and EMT, highlighting their roles in lung cancer progression. It also summarizes emerging therapeutic strategies targeting TAM polarization and the EMT process, emphasizing their potential for clinical translation. This study fills the gap in systematic reviews on the interaction between TAMs and EMT, providing a comprehensive theoretical foundation for future research and the development of novel lung cancer therapies.

Circular RNAs perspective: exploring the direction of immunotherapy for colorectal cancer

Circular RNAs (circRNAs) are multifaceted molecules that play a pivotal role in regulating gene expression at both transcriptional and post-transcriptional levels. Their expression is highly tissue-specific and developmentally regulated, making them critical players in various physiological processes and diseases, particularly cancer. In colorectal cancer, circRNAs exhibit significantly dysregulated expression patterns and profoundly influence disease progression through diverse molecular mechanisms. Unraveling the complex roles of circRNAs in modulating colorectal cancer immunotherapy outcomes highlights their potential as both promising biomarkers and therapeutic targets. Moving forward, advancements in circRNA-based therapeutic strategies and delivery systems are poised to transform precision medicine, enabling early colorectal cancer diagnosis and improving patient prognosis.

Engineered exosomes in service of tumor immunotherapy: From optimizing tumor-derived exosomes to delivering CRISPR/Cas9 system

Exosomes can be modified and designed for various therapeutic goals because of their unique physical and chemical characteristics. Researchers have identified tumor-derived exosomes (TEXs) as significant players in cancer by influencing tumor growth, immune response evasion, angiogeneis, and drug resistance. TEXs promote the production of specific proteins important for cancer progression. Due to their easy accessibility, TEXs are being modified through genetic, drug delivery, membrane, immune system, and chemical alterations to be repurposed as vehicles for delivering drugs to improve cancer treatment outcomes. In the complex in vivo environment, the clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR/Cas9) system encounters challenges from degradation, neutralization, and immune responses, emphasizing the need for strategic distribution strategies for effective genome editing. Engineered exosomes present a promising avenue for delivering CRISPR/Cas9 in vivo. In this review, we will explore different techniques for enhancing TEXs using various engineering strategies. Additionally, we will discuss how these exosomes can be incorporated into advanced genetic engineering systems like CRISPR/Cas9 for possible therapeutic uses.

Immunoregulatory role of exosomal circRNAs in the tumor microenvironment

As cancer incidence and mortality rates rise, there is an urgent need to develop effective immunotherapy strategies. Circular RNA (circRNA), a newly identified type of non-coding RNA, is abundant within cells and can be released via exosomes, facilitating communication between cells. Studies have demonstrated that exosomal circRNAs can alter the tumor microenvironment and modulate immune responses by influencing the functions of T cells, natural killer (NK) cells, and macrophages, thereby enabling tumors to evade the immune system. Moreover, exosomal circRNAs show potential as diagnostic biomarkers and therapeutic targets for cancer. This review summarizes the regulatory roles of exosomal circRNAs in immune cells and their potential applications in cancer progression and treatment, highlighting their promise in improving cancer immunotherapy. Future research should concentrate on understanding the mechanisms of key exosomal circRNAs and developing targeted immunotherapy methods.

Tumour-derived exosomal miR-205 promotes ovarian cancer cell progression through M2 macrophage polarization via the PI3K/Akt/mTOR pathway

BACKGROUND

Tumour-associated macrophages (TAMs) are the most abundant immune cells in the tumour environment and are considered similar to M2 macrophages, which facilitate cancer progression. Exosomes, as important mediators of the cross-talk between tumour cells and tumour-associated macrophages, can facilitate the development and metastasis of ovarian cancer by mediating M2 macrophage polarization. However, the exact mechanisms underlying the communication between ovarian cancer (OC) cells and tumour-associated macrophages during OC progression remain unclear.

RESULTS

Here, we demonstrated that high expression of miR-205 was associated with M2 macrophage infiltration, which affected the prognosis of OC patients. Importantly, tumour-derived miR-205 could be transported from OC cells to macrophages via exosomes and promote cancer cell invasion and metastasis by inducing M2-like macrophage polarization. Animal experiments further confirmed that exosomal miR-205-induced M2 macrophages accelerated OC progression in vivo. Mechanistically, miR-205 downregulated PTEN, activating the PI3K/AKT/mTOR signalling pathway, which is critical for M2 polarization.

CONCLUSIONS

These results reveal that exosomal miR-205 plays a pivotal role in macrophage polarization within the OC microenvironment, highlighting its potential as a therapeutic target for OC treatment. This study not only enhances our understanding of the interactions between tumour and immune cells but also opens new avenues for targeted therapies against exosomal miR-205 in ovarian cancer.

Integrins and integrin-driven secretory pathways as multi-dimensional regulators of tumor-associated macrophage recruitment and reprogramming in tumor microenvironment

Integrins, a group of transmembrane receptors, play a crucial role in mediating the interactions between cells and extracellular matrix (ECM) proteins. The intracellular signaling initiated by these cell-matrix interactions in leukocytes mediates many essential cellular processes such as survival, migration, metabolism, and other immunological functions. Macrophages, as phagocytes, participate in both proinflammatory and anti-inflammatory processes, including progression. Numerous reports have shown that the integrin-regulated secretome, comprising cytokines, chemokines, growth factors, proteases, and other bioactive molecules, is a crucial modulator of macrophage functions in tumors, significantly influencing macrophage programming and reprogramming within the tumor microenvironment (TME) in addition to driving their step-by-step entry process into tumor tissue spaces. Importantly, studies have demonstrated a pivotal role for integrin receptor-mediated secretome and associated signaling pathways in functional reprogramming from anti-tumorigenic to pro-tumorigenic phenotype in tumor-associated macrophages (TAMs). In this comprehensive review, we have provided an in-depth analysis of the latest findings of various key pathways, mediators, and signaling cascades associated with integrin-driven polarization of macrophages in tumors. This manuscript will provide an updated understanding of the modulation of inflammatory monocytes/ macrophages and TAMs by integrin-driven secretory pathways in various functions such as migration, differentiation, and their role in tumor progression, angiogenesis, and metastasis.

Cellular plasticity and non-small cell lung cancer: role of T and NK cell immune evasion and acquisition of resistance to immunotherapies

Lung cancer is a leading global cause of mortality, with non-small cell lung cancer (NSCLC) accounting for a significant portion of cases. Immune checkpoint inhibitors (ICIs) have transformed NSCLC treatment; however, many patients remain unresponsive. ICI resistance in NSCLC and its association with cellular plasticity, epithelial-mesenchymal transition (EMT), enhanced adaptability, invasiveness, and resistance is largely influenced by epigenetic changes, signaling pathways, tumor microenvironment, and associated immune cells, fibroblasts, and cytokines. Immunosuppressive cells, including M2 tumor-associated macrophages, myeloid-derived suppressor cells, and regulatory T cells, contribute to resistance by suppressing the immune response. This cellular plasticity is influenced when B cells, natural killer cells, and T cells are exhausted or inhibited by components of the tumor microenvironment. Conversely, diverse T cell, NK cell, and B cell subsets hold potential as predictive response markers particularly cytotoxic CD8+ T cells, effector memory T cells, activated T cells, tumor infiltrated NK cells, tertiary lymphoid structures, etc. influence treatment response. Identifying specific gene expressions and immunophenotypes within T cells may offer insights into early clinical responses to immunotherapy. ICI resistance in NSCLC is a multifaceted process shaped by tumor plasticity, the complex tumor microenvironment, and dynamic immune cell changes. Comprehensive analysis of these factors may lead to the identification of novel biomarkers and combination therapies to enhance ICI efficacy in NSCLC treatment.

A game of hide-and-seek: how extracellular vesicles evade the immune system

Extracellular vesicles (EVs) are heterogeneously sized, cell-derived nanoparticles operating as proficient mediators of intercellular communication. They are produced by normal as well as diseased cells and carry a variety of cargo. While the molecular details of EV biology have been worked out over the past two decades, one question that continues to intrigue many is how are EVs able to evade the phagocytic immune cells while also being effectively internalized by the target cell or tissue. While some of the components that facilitate this process have started to be identified, many mechanisms are yet to be dissected. This review summarises some of the key mechanisms that cancer cell-derived and viral infected cell-derived EVs utilize to evade the immune system. It will discuss the diverse cloaking mechanisms, in the form of membrane proteins and cargo content that these EVs utilize to enhance pathogenesis. Further, it will highlight the different strategies that have been used to design EVs to escape the immune system, thereby increasing their circulation time with no major toxic effects in vivo. An understanding of the potential EV components that allow better immune evasion can be used to bioengineer EVs with better circulation times for therapeutic purposes.

Hsa_Circ_002144 Promotes Glycolysis and Immune Escape of Breast Cancer Through miR-326/PKM Axis

Background: Breast cancer is a leading cause of cancer-related deaths in women worldwide, posing a significant threat to female health. Therefore, it is crucial to search for new therapeutic targets and prognostic biomarkers for breast cancer patients. Method: Bioinformatics analysis, quantitative real-time PCR (qRT-PCR), and fluorescence in situ hybridization (FISH) were employed to investigate the expression of hsa_circ_002144 in breast cancer. Transwell assay, Western blotting, and cell viability assay were utilized to assess the impact of hsa_circ_002144 on the proliferation, migration, and invasion of breast cancer cells. Additionally, a mouse model was established to validate its functionality. Flow cytometry, WB analysis, enzyme-linked immunosorbent assay (ELISA), qRT-PCR, exosomes isolation, and co-culture system were employed to elucidate the molecular mechanism underlying macrophage polarization. Result: we have discovered for the first time that hsa_circ_002144 is highly expressed in breast cancer. It affected tumor growth and metastasis and could influence macrophage polarization through the glycolytic pathway. Conclusion: This finding provides a new direction for breast cancer treatment and prognosis assessment.

Exosome therapeutics for non-small cell lung cancer tumorigenesis

Non-small cell lung cancer (NSCLC) remains an ongoing health concern, with poor treatment options and prognosis for many patients. Typically, individuals with lung cancer are detected at the middle and terminal stages, resulting in poor medical results due to lack of initial diagnosis and treatment. So, finding the initial specific and effective therapy options for lung cancer is necessary. In addition, exosomes are generally small lipid vesicles with a diameter in the nanometer range that are created and released by different cell types. Exosomes have therapeutic potential through delivering bioactive compounds including microRNAs, siRNAs, and therapeutic proteins to tumor cells, modifying the tumor microenvironment, and promoting anti-tumor immune responses. In recent years, exosome-based therapy has become known as an appropriate approach for NSCLC treatment. This review offers an overview of the possibility of exosome-based therapy for NSCLC, with an emphasis on mechanisms of action, preclinical research, and current clinical trials. Preclinical studies have shown that exosome-based therapy can decrease tumor growth, metastasis, and drug resistance in NSCLC models. Furthermore, ongoing clinical trials are looking at the safety and efficacy of exosome-based therapies in NSCLC patients, offering important insights into their translational prospects. Despite promising preclinical evidences, significant obstacles remain, including optimizing exosome isolation and purification techniques, standardizing production strategies, and developing scalable manufacturing processes. Overall, exosome-based therapy shows significant promise as a novel and various methods for treating NSCLC, with the potential to enhance patient outcomes and evolution cancer treatment.

Colon Cancer-Derived Exosomal LncRNA-XIST Promotes M2-like Macrophage Polarization by Regulating PDGFRA

Colon cancer ranks second in overall cancer-related deaths and poses a serious risk to human life and health. In recent years, exosomes are believed to play an important and significant role in cancer, especially tumor-derived exosomes (TDEs). Previous studies have highlighted the pivotal role of exosomes in tumor development, owing to their ability to mediate communication between tumor cells and macrophages, induce macrophage M2 polarization, and facilitate the progression of tumorigenesis. In this study, we revealed that colon cancer-derived exosomes promoted M2-like macrophage polarization. Moreover, exosome-induced M2-like macrophages, in turn, promoted the proliferation, migration, and invasion abilities of colon cancer cells. Specifically, CT26- and HCT116-derived exosomes led to the activation of AKT, ERK, and STAT3/6 signaling pathways in THP-1(Mφ) cells. Furthermore, our findings showed that colon cancer-derived exosomes secreted lncXIST to sponge miR-17-5p, which, in turn, promoted the expression of PDGFRA, a common gene found in all three signaling pathways, to facilitate M2-like macrophage polarization. Dual-luciferase reporter assays confirmed the binding relationship between lncXIST and miR-17-5p, as well as miR-17-5p and PDGFRA. Collectively, our results highlight the novel role of lncXIST in facilitating macrophage polarization by sponging miR-17-5p and regulating PDGFRA expression.

RNAs in tumour-derived extracellular vesicles and their significance in the tumour microenvironment

Small extracellular vesicles (sEVs) secreted by various types of cells serve as crucial mediators of intercellular communication within the complex tumour microenvironment (TME). Tumour-derived small extracellular vesicles (TDEs) are massively produced and released by tumour cells, recapitulating the specificity of their cell of origin. TDEs encapsulate a variety of RNA species, especially messenger RNAs, microRNAs, long non-coding RNAs, and circular RNAs, which release to the TME plays multifaced roles in cancer progression through mediating cell proliferation, invasion, angiogenesis, and immune evasion. sEVs act as natural delivery vehicles of RNAs and can serve as useful targets for cancer therapy. This review article provides an overview of recent studies on TDEs and their RNA cargo, with emphasis on the role of these RNAs in carcinogenesis.

Tumor-derived Exosomes and Antitumor Immunity

Cancer immunotherapy, including immune checkpoint blockade, has been approved for treatment of patients with many cancer types. However, some patients fail to respond to immunotherapy, and emerging evidence indicates that tumor-derived exosomes (TEX) play a major role in reprogramming the host immune cells by inducing their dysfunction. Focusing on effector T cells, this review illustrates mechanisms of suppression that TEX use, thus promoting tumor escape from the host immune system. TEX carry multiple suppressive signals that drive T cell dysfunction and convert the tumor microenvironment into "an immune desert" in which activated T cells either die or are reprogrammed to mediate protumor functions. The reprogrammed T cells produce a new crop of CD3+ immunoinhibitory exosomes that further amplify suppression mediated by TEX. The result is a profound depletion of antitumor immune effector cells that reflects the defective immune competence of the cancer patient and partly explains why TEX are a significant barrier for cancer immunotherapy.

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

The role of extracellular vesicles in immune cell exhaustion and resistance to immunotherapy

INTRODUCTION

Extracellular vesicles (EVs) are membrane-bound nanoparticles for intercellular communication. Subtypes of EVs, namely exosomes and microvesicles transfer diverse, bioactive cargo to their target cells and eventually interfere with immune responses. Despite being a promising approach, cancer immunotherapy currently faces several challenges including immune resistance. EVs secreted from various sources in the tumor microenvironment provoke immune cell exhaustion and lower the efficacy of immunological treatments, such as CAR T cells and immune checkpoint inhibitors.

AREAS COVERED

This article goes through the mechanisms of action of various types of EVs in inhibiting immune response and immunotherapies, and provides a comprehensive review of EV-based treatments.

EXPERT OPINION

By making use of the distinctive features of EVs, natural or modified EVs are innovatively utilized as novel cancer therapeutics. They are occasionally coupled with currently established treatments to overcome their inadequacies. Investigating the properties and interactions of EVs and EV-based treatments is crucial for determining future steps in cancer therapeutics.

Converting "cold" to "hot": epigenetics strategies to improve immune therapy effect by regulating tumor-associated immune suppressive cells

Significant developments in cancer treatment have been made since the advent of immune therapies. However, there are still some patients with malignant tumors who do not benefit from immunotherapy. Tumors without immunogenicity are called "cold" tumors which are unresponsive to immunotherapy, and the opposite are "hot" tumors. Immune suppressive cells (ISCs) refer to cells which can inhibit the immune response such as tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) cells and so on. The more ISCs infiltrated, the weaker the immunogenicity of the tumor, showing the characteristics of "cold" tumor. The dysfunction of ISCs in the tumor microenvironment (TME) may play essential roles in insensitive therapeutic reaction. Previous studies have found that epigenetic mechanisms play an important role in the regulation of ISCs. Regulating ISCs may be a new approach to transforming "cold" tumors into "hot" tumors. Here, we focused on the function of ISCs in the TME and discussed how epigenetics is involved in regulating ISCs. In addition, we summarized the mechanisms by which the epigenetic drugs convert immunotherapy-insensitive tumors into immunotherapy-sensitive tumors which would be an innovative tendency for future immunotherapy in "cold" tumor.

Liquid biopsy techniques and lung cancer: diagnosis, monitoring and evaluation

Lung cancer stands as the most prevalent form of cancer globally, posing a significant threat to human well-being. Due to the lack of effective and accurate early diagnostic methods, many patients are diagnosed with advanced lung cancer. Although surgical resection is still a potential means of eradicating lung cancer, patients with advanced lung cancer usually miss the best chance for surgical treatment, and even after surgical resection patients may still experience tumor recurrence. Additionally, chemotherapy, the mainstay of treatment for patients with advanced lung cancer, has the potential to be chemo-resistant, resulting in poor clinical outcomes. The emergence of liquid biopsies has garnered considerable attention owing to their noninvasive nature and the ability for continuous sampling. Technological advancements have propelled circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), extracellular vesicles (EVs), tumor metabolites, tumor-educated platelets (TEPs), and tumor-associated antigens (TAA) to the forefront as key liquid biopsy biomarkers, demonstrating intriguing and encouraging results for early diagnosis and prognostic evaluation of lung cancer. This review provides an overview of molecular biomarkers and assays utilized in liquid biopsies for lung cancer, encompassing CTCs, ctDNA, non-coding RNA (ncRNA), EVs, tumor metabolites, TAAs and TEPs. Furthermore, we expound on the practical applications of liquid biopsies, including early diagnosis, treatment response monitoring, prognostic evaluation, and recurrence monitoring in the context of lung cancer.

Protocols for Co-Culture Phenotypic Assays with Breast Cancer Cells and THP-1-Derived Macrophages

Tumor mass comprises not only cancer cells but also heterogeneous populations of immune and stromal cells, along with the components of the extracellular matrix, collectively called the tumor microenvironment (TME). This diverse population of cells can communicate with each other, which can positively or negatively affect tumor growth and progression to malignancy. The most common type of immune cells in the TME are macrophages. Macrophages continuously differentiate into a broad landscape of tumor-associated macrophages (TAMs) in response to numerous signals from the TME, which makes studies on TAMs quite challenging. Therefore, implementing reliable protocols is a milestone for drawing consistent conclusions about the interactions between cancer cells and TAMs. Here, we provide the details for the polarization of a human leukemia monocytic cell line, THP-1, into M0, M1 and M2 macrophages. We also present a step-by-step protocol for a transwell co-culture using a human breast cancer cell line, HCC1806, and THP-1-derived macrophages. Finally, we describe the colony formation and migration assays performed on the breast cancer cells after the co-culture with macrophages to measure the influence of macrophages on the oncogenic features of cancer cells. In summary, our co-culture-based protocols can be a valuable resource for investigating the interactions between macrophages and cancer cells.

Mechanism of gambogic acid repressing invasion and metastasis of colorectal cancer by regulating macrophage polarization via tumor cell-derived extracellular vesicle-shuttled miR-21

Colorectal cancer (CRC) is a major cause of mortality and morbidity. Gambogic acid (GA) is a promising antitumor drug for treating CRC. We aimed to elucidate its mechanism in CRC invasion/metastasis via tumor cell-derived extracellular vesicle (EV)-carried miR-21. Nude mice peritoneal carcinomatosis (PC) model was subjected to GA treatment liver collection, followed by observation/counting of metastatic liver tissues/liver metastatic nodules by hematoxylin and eosin staining. miR-21 expression in metastatic liver tissues/CD68 + CD86, CD68 + CD206 cell percentages and M2 macrophage marker CD206 level in tumor tissues/interleukin (IL)-12 and IL-10 levels were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR)/flow cytometry/enzyme-linked immunosorbent assay. HT-29 cells were treated with GA/miR-21 mimics/negative control for 48 h. miR-21 expression/cell proliferation/migration/invasion/apoptosis were assessed by RT-qPCR/cell counting kit-8/scratch assay/transwell assay/flow cytometry. EVs were extracted from HT-29 cells and identified by transmission electron microscope/nanoparticle tracking analysis/Western blot. IL-4/IL-13-induced macrophages/PC nude mice were treated with GA and EVs, with the internalization of EVs by macrophages assessed through the uptake test. After intraperitoneal injection of GA, PC nude mice exhibited decreased tumor cell density/irregular cell number/liver metastatic nodule number/miR-21 expression, and CRC cells manifested reduced CD68 + CD206 cells/IL-10/miR-21/proliferation/migration/invasion and increased CD68 + CD86 cells/IL-12/apoptosis, while these trends were opposite after miR-21 overexpression, implying that GA curbed CRC/cell invasion/metastasis and macrophage polarization by diminishing miR-21 levels. miR-21 was encapsulated in HT-29 cell-derived EVs. M2 polarization elevated CD206 cells/IL-10, which were decreased by simultaneous GA treatment. EVs could be uptaken by macrophages. CRC cell-EV-miR-21 annulled the suppression effects of GA on macrophage M2 polarization. GA suppressed macrophage M2 polarization by lessening tumor cell derived-EV-shuttled miR-21, thereby weakening CRC invasion/metastasis.

Clinical impact of epithelial–mesenchymal transition for cancer therapy

The epithelial–mesenchymal transition (EMT) represents a pivotal frontier in oncology, playing a central role in the metastatic cascade of cancer—a leading global health challenge. This comprehensive review delves into the complexities of EMT, a process where cancer cells gain exceptional mobility, facilitating their invasion into distant organs and the establishment of secondary malignancies. We thoroughly examine the myriad of factors influencing EMT, encompassing transcription factors, signalling pathways, metabolic alterations, microRNAs, long non‐coding RNAs, epigenetic changes, exosomal interactions and the intricate dynamics of the tumour microenvironment. Particularly, the review emphasises the advanced stages of EMT, crucial for the development of highly aggressive cancer phenotypes. During this phase, cancer cells penetrate the vascular barrier and exploit the bloodstream to propagate life‐threatening metastases through the mesenchymal–epithelial transition. We also explore EMT's significant role in fostering tumour dormancy, senescence, the emergence of cancer stem cells and the formidable challenge of therapeutic resistance. Our review transcends a mere inventory of EMT‐inducing elements; it critically assesses the current state of EMT‐focused clinical trials, revealing both the hurdles and significant breakthroughs. Highlighting the potential of EMT research, we project its transformative impact on the future of cancer therapy. This exploration is aimed at paving the way towards an era of effectively managing this relentless disease, positioning EMT at the forefront of innovative cancer research strategies.

Tumor-related exosomal circ_0001715 promotes lung adenocarcinoma cell proliferation and metastasis via enhancing M2 macrophage polarization by regulating triggering receptor expressed on myeloid cells-2

BACKGROUND

Circular RNAs (circRNAs) have been shown to mediate tumor-associated macrophages (TAMs) to regulate the development of many cancers, including lung adenocarcinoma (LUAD). However, whether circ_0001715 regulates LUAD progression by mediating TAMs polarization remains uncertain.

METHODS

Monocytes (THP-1) were treated with PMA to induce M0 macrophages. M0 macrophages were incubated with LUAD cells-derived exosomes and then cocultured with LUAD cells. The levels of circ_0001715, M2 macrophage markers, microRNA (miR)-205-5p, and triggering receptor expressed on myeloid cells-2 (TREM2) were examined using quantitative real-time PCR. Flow cytometry was performed to assess M2 macrophage surface marker CD206. Cell proliferation, migration and invasion were determined using cell counting kit 8, EdU, colony formation and transwell assays. Dual-luciferase reporter assay was used to investigate the interactions between miR-205-5p and circ_0001715 or TREM2.

RESULTS

Circ_0001715 knockdown inhibited M2 macrophage polarization and its overexpression had an opposite effect. After M0 macrophages transfected with si-circ_0001715 were cocultured with LUAD cells, the proliferation and metastasis of LUAD cells were markedly reduced. Exosomes transferred circ_0001715 between M0 macrophages and LUAD cells. Exosomal circ_0001715 promoted M2 macrophage polarization to increase LUAD cell proliferation and metastasis. In terms of mechanism, circ_0001715 sponged miR-205-5p to positively regulate TREM2. TREM2 upregulation also could promote LUAD cell proliferation and metastasis via increasing M2 macrophage polarization. In addition, TREM2 knockdown reversed the effect of exosomal circ_0001715 on M2 macrophage polarization and LUAD cell progression.

CONCLUSION

Exosomal circ_0001715 led to LUAD cell proliferation and metastasis by promoting M2 macrophage polarization via the miR-205-5p/TREM2 axis.

Roles of circRNAs in regulating the tumor microenvironment

CircRNAs, a type of non-coding RNA widely present in eukaryotic cells, have emerged as a prominent focus in tumor research. However, the functions of most circRNAs remain largely unexplored. Known circRNAs exert their regulatory roles through various mechanisms, including acting as microRNA sponges, binding to RNA-binding proteins, and functioning as transcription factors to modulate protein translation and coding. Tumor growth is not solely driven by gene mutations but also influenced by diverse constituent cells and growth factors within the tumor microenvironment (TME). As crucial regulators within the TME, circRNAs are involved in governing tumor growth and metastasis. This review highlights the role of circRNAs in regulating angiogenesis, matrix remodeling, and immunosuppression within the TME. Additionally, we discuss current research on hypoxia-induced circRNAs production and commensal microorganisms' impact on the TME to elucidate how circRNAs influence tumor growth while emphasizing the significance of modulating the TME.

Non-coding RNAs in lung cancer: molecular mechanisms and clinical applications

Lung cancer (LC) is a heterogeneous disease with high malignant degree, rapid growth, and early metastasis. The clinical outcomes of LC patients are generally poor due to the insufficient elucidation of pathological mechanisms, low efficiency of detection and assessment methods, and lack of individualized therapeutic strategies. Non-coding RNAs (ncRNAs), including microRNA (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA), are endogenous regulators that are widely involved in the modulation of almost all aspects of life activities, from organogenesis and aging to immunity and cancer. They commonly play vital roles in various biological processes by regulating gene expression via their interactions with DNA, RNA, or protein. An increasing amount of studies have demonstrated that ncRNAs are closely correlated with the initiation and development of LC. Their dysregulation promotes the progression of LC via distinct mechanisms, such as influencing protein activity, activating oncogenic signaling pathways, or altering specific gene expression. Furthermore, some ncRNAs present certain clinical values as biomarker candidates and therapeutic targets for LC patients. A complete understanding of their mechanisms in LC progression may be highly beneficial to developing ncRNA-based therapeutics for LC patients. This review mainly focuses on the intricate mechanisms of miRNA, lncRNA, and circRNA involved in LC progression and discuss their underlying applications in LC treatment.

Tumor cell-derived exosomes regulate macrophage polarization: Emerging directions in the study of tumor genesis and development

As an extracellular vesicle, exosomes play an important role in intercellular information transmission, delivering cargos of the parent cell, such as RNA, DNA, proteins, and lipids, activating different signaling pathways in the target cell and regulating inflammation, angiogenesis, and tumor progression. In particular, exosomes secreted by tumor cells can change the function of surrounding cells, creating a microenvironment conducive to tumor growth and metastasis. For example, after macrophages phagocytose exosomes and accept their cargos, they activate macrophage polarization-related signaling pathways and polarize macrophages into M1 or M2 types to exert antitumor or protumor functions. Currently, the study of exosomes affecting the polarization of macrophages has attracted increasing attention. Therefore, this paper reviews relevant studies in this field to better understand the mechanism of exosome-induced macrophage polarization and provide evidence for exploring novel targets for tumor therapy and new diagnostic markers in the future.

Roles of exosome-derived non-coding RNA in tumor micro-environment and its clinical application

Tumor-derived exosomes play an important role in the tumor micro-environment. The exosome-derived non-coding RNAs are transmitted in the tumor microenvironment in three ways, communication between tumor cells, normal cells affecting tumor cells, and tumor cells affecting normal cells. Through these three ways, exosomal non-coding RNAs are involved in the regulation of tumor progression, affecting tumor angiogenesis, tumor invasiveness, drug resistance, stemness, tumor metabolic repro-gramming and immune escape, resulting in dual roles in promoting or inhibiting tumor development. Exosomes have a membranous structure and their contents are resistant to degradation by extracellular proteases and remain highly stable in body fluids, thus exosome-derived non-coding RNAs are expected to serve as diagnostic and prognostic indicators for a variety of cancers. In addition, exosomes can be used to deliver non-coding RNAs for targeted therapy, or to knock down or modify tumor-promoting non-coding RNAs for tumor therapy. This article reviews the function and communication mechanism of exosomal non-coding RNAs in the tumor microenvironment, including their pathways of action, effects, potential values for tumor biomarkers and treatment targets. This article also points out the issues that need to be further studied in order to promote the progress of extracellular non-coding RNAs in cancer research and their application in tumor diagnosis and treatment.

Recent advances of exosomal circRNAs in cancer and their potential clinical applications

Circular RNA (circRNA) is a type of non-coding RNA that forms a covalently closed, uninterrupted loop. The expression of circRNA differs among cell types and tissues, and various circRNAs are aberrantly expressed in a variety of diseases, including cancer. Aberrantly expressed circRNAs contribute to disease progression by acting as microRNA sponges, functional protein sponges, or novel templates for protein translation. Recent studies have shown that circRNAs are enriched in exosomes. Exosomes are spherical bilayer vesicles released by cells into extracellular spaces that mediate intercellular communication by delivering cargoes. These cargoes include metabolites, proteins, lipids, and RNA molecules. Exosome-mediated cell-cell or cell-microenvironment communications influence the progression of carcinogenesis by regulating cell proliferation, angiogenesis, metastasis as well as immune escape. In this review, we summarize the current knowledge about exosomal circRNAs in cancers and discuss their specific functions in tumorigenesis. Additionally, we discuss the potential value of exosomal circRNAs as diagnostic biomarkers and the potential applications of exosomal circRNA-based cancer therapy.

Epigenetic regulation in the tumor microenvironment: molecular mechanisms and therapeutic targets

Over decades, researchers have focused on the epigenetic control of DNA-templated processes. Histone modification, DNA methylation, chromatin remodeling, RNA modification, and noncoding RNAs modulate many biological processes that are crucial to the development of cancers. Dysregulation of the epigenome drives aberrant transcriptional programs. A growing body of evidence suggests that the mechanisms of epigenetic modification are dysregulated in human cancers and might be excellent targets for tumor treatment. Epigenetics has also been shown to influence tumor immunogenicity and immune cells involved in antitumor responses. Thus, the development and application of epigenetic therapy and cancer immunotherapy and their combinations may have important implications for cancer treatment. Here, we present an up-to-date and thorough description of how epigenetic modifications in tumor cells influence immune cell responses in the tumor microenvironment (TME) and how epigenetics influence immune cells internally to modify the TME. Additionally, we highlight the therapeutic potential of targeting epigenetic regulators for cancer immunotherapy. Harnessing the complex interplay between epigenetics and cancer immunology to develop therapeutics that combine thereof is challenging but could yield significant benefits. The purpose of this review is to assist researchers in understanding how epigenetics impact immune responses in the TME, so that better cancer immunotherapies can be developed.

The Potential Use of Exosomes in Anti-Cancer Effect Induced by Polarized Macrophages

The rapid development of aberrant cells outgrowing their normal bounds, which can subsequently infect other body parts and spread to other organs-a process known as metastasis-is one of the significant characteristics of cancer. The main reason why cancer patients die is because of widespread metastases. This abnormal cell proliferation varies in cancers of over a hundred types, and their response to treatment can vary substantially. Several anti-cancer drugs have been discovered to treat various tumors, yet they still have harmful side-effects. Finding novel, highly efficient targeted therapies based on modifications in the molecular biology of tumor cells is essential to reduce the indiscriminate destruction of healthy cells. Exosomes, an extracellular vesicle, are promising as a drug carrier for cancer therapy due to their good tolerance in the body. In addition, the tumor microenvironment is a potential target to regulate in cancer treatment. Therefore, macrophages are polarized toward M1 and M2 phenotypes, which are involved in cancer proliferation and are malignant. It is evident from recent studies that controlled macrophage polarization might contribute to cancer treatment, by the direct way of using miRNA. This review provides an insight into the potential use of exosomes to develop an 'indirect', more natural, and harmless cancer treatment through regulating macrophage polarization.

Exosomal Non-Coding RNAs: Novel Regulators of Macrophage-Linked Intercellular Communication in Lung Cancer and Inflammatory Lung Diseases

Macrophages are innate immune cells and often classified as M1 macrophages (pro-inflammatory states) and M2 macrophages (anti-inflammatory states). Exosomes are cell-derived nanovesicles that range in diameter from 30 to 150 nm. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), are abundant in exosomes and exosomal ncRNAs influence immune responses. Exosomal ncRNAs control macrophage-linked intercellular communication via their targets or signaling pathways, which can play positive or negative roles in lung cancer and inflammatory lung disorders, including acute lung injury (ALI), asthma, and pulmonary fibrosis. In lung cancer, exosomal ncRNAs mediated intercellular communication between lung tumor cells and tumor-associated macrophages (TAMs), coordinating cancer proliferation, migration, invasion, metastasis, immune evasion, and therapy resistance. In inflammatory lung illnesses, exosomal ncRNAs mediate macrophage activation and inflammation to promote or inhibit lung damage. Furthermore, we also discussed the possible applications of exosomal ncRNA-based therapies for lung disorders.

Regulation of the tumor immune microenvironment by cancer-derived circular RNAs

Circular RNA (circRNAs) is a covalently closed circular non-coding RNA formed by reverse back-splicing from precursor messenger RNA. It is found widely in eukaryotic cells and can be released to the surrounding environment and captured by other cell types. This, circRNAs serve as connections between different cell types for the mediation of multiple signaling pathways. CircRNAs reshape the tumor microenvironment (TME), a key factor involved in all stages of cancer development, by regulating epithelial-stromal transformation, tumor vascularization, immune cell function, and inflammatory responses. Immune cells are the most abundant cellular TME components, and they have profound toxicity to cancer cells. This review summarizes circRNA regulation of immune cells, including T cells, natural killer cells, and macrophages; highlights the impact of circRNAs on tumor progression, treatment, and prognosis; and indicates new targets for tumor immunotherapy.

Cancer-associated fibroblast-secreted IGFBP7 promotes gastric cancer by enhancing tumor associated macrophage infiltration via FGF2/FGFR1/PI3K/AKT axis

We previously reported that IGFBP7 plays a role in maintaining mRNA stability of oncogenic lncRNA UBE2CP3 by RNA-RNA interaction in gastric cancer (GC). Clinical cohort studies had implied an oncogenic role of IGFBP7 in GC. However, the molecular mechanism of IGFBP7 in GC progression remains unknown. In this study, clinical analysis based on two independent cohorts showed that IGFBP7 was positively associated with poor prognosis and macrophage infiltration in GC. Loss-of-function studies confirmed the oncogenic properties of IGFBP7 in regulating GC cell proliferation and invasion. Mechanismly, IGFBP7 was highly expressed in cancer-associated fibroblasts (CAF) and mesenchymal cells, and was induced by epithelial-to-mesenchymal transition (EMT) signaling, since its expression was increased by TGF-beta treatment and reduced by overexpression of OVOL2 in GC. RNA sequencing, qRT-PCR, ELISA assay showed that IGFBP7 positively regulated FGF2 expression and secretion in GC. Transcriptome analysis revealed that FGFR1 was downregulated in M1 polarization but upregulated in M2 polarization. Exogenous recombinant IGFBP7 treatment in macrophages and GC cells further identified that IGFBP7 promotes tumor associated macrophage (TAM) polarization via FGF2/FGFR1/PI3K/AKT axis. Our finding here represented the first evidence that IGFBP7 promotes GC by enhancing TAM/M2 macrophage polarization through FGF2/FGFR1/PI3K/AKT axis.

EIF4A3 serves as a prognostic and immunosuppressive microenvironment factor and inhibits cell apoptosis in bladder cancer

EIF4A3 (Eukaryotic translation initiation factor 4A3 (EIF4A3) was recently recognized as an oncogene; however, its role in BLCA (bladder cancer) remains unclear. We explored EIF4A3 expression and its prognostic value in BLCA in public datasets, including the TCGA (The Cancer Genome Atlas) and GEO (Gene Expression Omnibus). Thereafter, the association between EIF4A3 expression and the infiltration of immune cells and immune-checkpoint expression was determined using TIMER2 (Tumor Immune Estimation Resource 2) tool. Additionally, the impact of EIF4A3 on cellular proliferation and apoptosis events in BLCA cell lines was determined by siRNA technology. In this study, EIF4A3 was found to be significantly upregulated in BLCA, upregulated expression of EIF4A3 was related to poor prognosis, advanced histologic grade, subtype, pathological stage, white race, and poor primary therapy outcome. The immune infiltration analysis revealed that EIF4A3 expression was negatively associated with CD8⁺ and CD4⁺ T cells and positively with myeloid-derived suppressor cells, macrophage M2, cancer-associated fibroblasts, and Treg cells. Moreover, EIF4A3 was coexpressed with PD-L1 (programmed cell death 1-ligand 1) and its expression was higher in patients responding to anti-PD-L1 therapy. EIF4A3 knockdown significantly inhibited proliferation and promoted apoptosis in 5,637 and T24 cells. In summary, BLCA patients with elevated EIF4A3 expression had an unfavorable prognosis and immunosuppressive microenvironment, and EIF4A3 may facilitate BLCA progression by promoting cell proliferation and inhibiting apoptosis. Furthermore, our study suggests that EIF4A3 is a potential biomarker and therapeutic target for BLCA.

Exosomal circular RNA: a signature for lung cancer progression

Membrane vesicles having a diameter of 30-150 nm are known as exosomes. Several cancer types secrete exosomes, which may contain proteins, circular RNAs (circRNAs), microRNAs, or DNA. CircRNAs are endogenous RNAs that do not code for proteins and can create continuous and covalently closed loops. In cancer pathogenesis, especially metastasis, exosomal circRNAs (exo-circRNAs) have a crucial role mainly due to the frequently aberrant expression levels within tumors. However, neither the activities nor the regulatory mechanisms of exo-circRNAs in advancing lung cancer (LC) are obvious. A better understanding of the regulation and network connections of exo-circRNAs will lead to better treatment for LCs. The main objective of the current review is to highlight the functions and mechanisms of exo-circRNAs in LC and assess the relationships between exo-circRNA dysregulation and LC progression. In addition, underline the possible therapeutic targets based on exo-circRNA modulating.

Tumor-derived extracellular vesicles modulate innate immune responses to affect tumor progression

Immune cells are capable of influencing tumor progression in the tumor microenvironment (TME). Meanwhile, one mechanism by which tumor modulate immune cells function is through extracellular vesicles (EVs), which are cell-derived extracellular membrane vesicles. EVs can act as mediators of intercellular communication and can deliver nucleic acids, proteins, lipids, and other signaling molecules between cells. In recent years, studies have found that EVs play a crucial role in the communication between tumor cells and immune cells. Innate immunity is the first-line response of the immune system against tumor progression. Therefore, tumor cell-derived EVs (TDEVs) which modulate the functional change of innate immune cells serve important functions in the context of tumor progression. Emerging evidence has shown that TDEVs dually enhance or suppress innate immunity through various pathways. This review aims to summarize the influence of TDEVs on macrophages, dendritic cells, neutrophils, and natural killer cells. We also summarize their further effects on the progression of tumors, which may provide new ideas for developing novel tumor therapies targeting EVs.

Strategies to overcome the main challenges of the use of exosomes as drug carrier for cancer therapy

Exosomes are naturally occurring nanosized particles that aid intercellular communication by transmitting biological information between cells. Exosomes have therapeutic efficacy that can transfer their contents between cells as natural carriers. In addition, the exosomal contents delivered to the recipient pathological cells significantly inhibit cancer progression. However, exosome-based tumor treatments are inadequately precise or successful, and various challenges should be adequately overcome. Here, we discuss the significant challenges that exosomes face as drug carriers used for therapeutic targets and strategies for overcoming these challenges in order to promote this new incoming drug carrier further and improve future clinical outcomes. We also present techniques for overcoming these challenges.

Role of exosomal non-coding RNAs from tumor cells and tumor-associated macrophages in the tumor microenvironment

Exosomes have a crucial role in intercellular communication and mediate interactions between tumor cells and tumor-associated macrophages (TAMs). Exosome-encapsulated non-coding RNAs (ncRNAs) are involved in various physiological processes. Tumor-derived exosomal ncRNAs induce M2 macrophage polarization through signaling pathway activation, signal transduction, and transcriptional and post-transcriptional regulation. Conversely, TAM-derived exosomal ncRNAs promote tumor proliferation, metastasis, angiogenesis, chemoresistance, and immunosuppression. MicroRNAs induce gene silencing by directly targeting mRNAs, whereas lncRNAs and circRNAs act as miRNA sponges to indirectly regulate protein expressions. The role of ncRNAs in tumor-host interactions is ubiquitous. Current research is increasingly focused on the tumor microenvironment. On the basis of the "cancer-immunity cycle" hypothesis, we discuss the effects of exosomal ncRNAs on immune cells to induce T cell exhaustion, overexpression of programmed cell death ligands, and create a tumor immunosuppressive microenvironment. Furthermore, we discuss potential applications and prospects of exosomal ncRNAs as clinical biomarkers and drug delivery systems.

Multiplex Analysis of CircRNAs from Plasma Extracellular Vesicle-Enriched Samples for the Detection of Early-Stage Non-Small Cell Lung Cancer

BACKGROUND

The analysis of liquid biopsies brings new opportunities in the precision oncology field. Under this context, extracellular vesicle circular RNAs (EV-circRNAs) have gained interest as biomarkers for lung cancer (LC) detection. However, standardized and robust protocols need to be developed to boost their potential in the clinical setting. Although nCounter has been used for the analysis of other liquid biopsy substrates and biomarkers, it has never been employed for EV-circRNA analysis of LC patients.

METHODS

EVs were isolated from early-stage LC patients (n = 36) and controls (n = 30). Different volumes of plasma, together with different number of pre-amplification cycles, were tested to reach the best nCounter outcome. Differential expression analysis of circRNAs was performed, along with the testing of different machine learning (ML) methods for the development of a prognostic signature for LC.

RESULTS

A combination of 500 μL of plasma input with 10 cycles of pre-amplification was selected for the rest of the study. Eight circRNAs were found upregulated in LC. Further ML analysis selected a 10-circRNA signature able to discriminate LC from controls with AUC ROC of 0.86.

CONCLUSIONS

This study validates the use of the nCounter platform for multiplexed EV-circRNA expression studies in LC patient samples, allowing the development of prognostic signatures.

Circular RNAs Involved in the Regulation of the Age-Related Pathways

Circular RNAs (circRNAs) are a class of covalently circular noncoding RNAs that have been extensively studied in recent years. Aging is a process related to functional decline that is regulated by signal transduction. An increasing number of studies suggest that circRNAs can regulate aging and multiple age-related diseases through their involvement in age-related signaling pathways. CircRNAs perform several biological functions, such as acting as miRNA sponges, directly interacting with proteins, and regulating transcription and translation to proteins or peptides. Herein, we summarize research progress on the biological functions of circRNAs in seven main age-related signaling pathways, namely, the insulin-insulin-like, PI3K-AKT, mTOR, AMPK, FOXO, p53, and NF-κB signaling pathways. In these pathways, circRNAs mainly function as miRNA sponges. In this review, we suggest that circRNAs are widely involved in the regulation of the main age-related pathways and are potential biomarkers for aging and age-related diseases.

Roles of exosomal circRNAs in tumour immunity and cancer progression

Tumour immunity plays an important role in the development of cancer. Tumour immunotherapy is an important component of antitumour therapy. Exosomes, a type of extracellular vesicle, act as mediators of intercellular communication and molecular transfer and play an essential role in tumour immunity. Circular RNAs (circRNAs) are a new type of noncoding RNA that are enriched within exosomes. In this review, we describe the effects of exosomal circRNAs on various immune cells and the mechanisms of these effects, including macrophages, neutrophils, T cells, and Natural killer (NK) cells. Next, we elaborate on the latest progress of exosome extraction. In addition, the function of exosomal circRNAs as a potential prognostic and drug sensitivity marker is described. We present the great promise of exosomal circRNAs in regulating tumour immunity, predicting patient outcomes, and evaluating drug efficacy.

Past, Present and Future: The Relationship Between Circular RNA and Immunity

The immune system has evolved since the birth of humans. However, immune-related diseases have not yet been overcome due to the lack of expected indicators and targeting specificity of current medical technology, subjecting patients to very uncomfortable physical and mental experiences and high medical costs. Therefore, the requirements for treatments with higher specificity and indicative ability are raised. Fortunately, the discovery of and continuous research investigating circular RNAs (circRNAs) represent a promising method among numerous methods. Although circRNAs wear regarded as metabolic wastes when discovered, as a type of noncoding RNA (ncRNA) with a ring structure and wide distribution range in the human body, circRNAs shine brilliantly in medical research by virtue of their special nature and structure-determined functions, such as high stability, wide distribution, high detection sensitivity, acceptable reproducibility and individual differences. Based on research investigating the role of circRNAs in immunity, we systematically discuss the hotspots of the roles of circRNAs in immune-related diseases, including expression profile analyses, potential biomarker research, ncRNA axis/network construction, impacts on phenotypes, therapeutic target seeking, maintenance of nucleic acid stability and protein binding research. In addition, we summarize the current situation of and problems associated with circRNAs in immune research, highlight the applications and prospects of circRNAs in the treatment of immune-related diseases, and provide new insight into future directions and new strategies for laboratory research and clinical applications.

The emerging landscape of exosomal CircRNAs in solid cancers and hematological malignancies

Circular RNAs (circRNAs) are a type of recently discovered noncoding RNA. They exert their biological functions by competitively binding to microRNAs (miRNAs) as miRNA sponges, promoting gene transcription and participating in the regulation of selective splicing, interacting with proteins and being translated into proteins. Exosomes are derived from intracavitary vesicles (ILVs), which are formed by the inward budding of multivesicular bodies (MVBs), and exosome release plays a pivotal role in intercellular communication. Accumulating evidence indicates that circRNAs in exosomes are associated with solid tumor invasion and metastasis. Additionally, emerging studies in the last 1 ~ 2 years have revealed that exosomal circRNA also have effect on hematological malignancies. In this review, we outline the properties and biological functions of circRNAs and exosomes. In particular, we summarize in detail the mechanism and roles of exosomal circRNAs and highlight their application as novel biomarkers in malignant tumors.

Roles and clinical application of exosomal circRNAs in the diagnosis and treatment of malignant tumors

Exosomes are microvesicles secreted by cells. They contain a variety of bioactive substances with important roles in intercellular communication. Circular RNA (circRNA), a type of nucleic acid molecule found in exosomes, forms a covalently bonded closed loop without 5′ caps or 3′ poly(A) tails. It is structurally stable, widely distributed, and tissue specific. CircRNAs mainly act as microRNA sponges and have important regulatory roles in gene expression; they are superior to other non-coding RNAs as molecular diagnostic markers and drug treatment targets. Exosomal-derived circRNAs in the body fluids of tumor patients can modulate tumor proliferation, invasion, metastasis, and drug resistance. They can be used as effective biomarkers for early non-invasive diagnosis and prognostic evaluation of tumors, and also represent ideal targets for early precision therapeutic intervention. This review provides a theoretical basis for exploring the applications of exosomal circRNAs in malignant tumor diagnosis and treatment. We describe the biological functions of exosomal circRNAs in the occurrence and development of malignant tumors, their potential utility in diagnosis and treatment, and possible mechanisms.

Exosomes Regulate the Epithelial-Mesenchymal Transition in Cancer

Exosomes are important mediators of intercellular communication and participate in complex biological processes by transferring a variety of bioactive molecules between cells. Epithelial–mesenchymal transition (EMT) is a process in which the cell phenotype changes from epithelioid to mesenchymal-like. EMT is also an important process for cancer cells by which they acquire invasive and metastatic capabilities, which aggravates the degree of tumor malignancy. Numerous studies have demonstrated that exosomes encapsulate various components, such as microRNAs and proteins, and transfer information between tumor cells or between tumor cells and the tumor microenvironment, thereby regulating the EMT process. Exosomes can also be used for cancer diagnosis and treatment or as a drug delivery platform. Thus, they can be used as a therapeutic tool to control the occurrence of EMT and affect cancer progression. In this review, we summarize the latest research advancements in the regulation of the EMT process in tumor cells by the contents of exosomes. Furthermore, we discuss the potential and challenges of using exosomes as a tool for cancer treatment.

Exosomal non-coding RNAs: Emerging roles in bilateral communication between cancer cells and macrophages

The tumor microenvironment (TME) is a dynamic network of cellular organization that comprises diverse cell types and significantly contributes to cancer development. As pivotal immune stromal cells in the TME, macrophages are extensively heterogeneous and exert both antitumor and protumor functions. Exosomes are nanosized extracellular membranous vesicles with diameters between 30 and 150 nm. By transferring multiple bioactive substances such as proteins, lipids, and nucleic acids, exosomes play an important role in the communication between cells. Recently, growing evidence has demonstrated that non-coding RNAs (ncRNAs) are enriched in exosomes and that exosomal ncRNAs are involved in the crosstalk between cancer cells and macrophages. Furthermore, circulating exosomal ncRNAs can be detected in biofluids, serving as promising noninvasive biomarkers for the early diagnosis and prognostic prediction of cancer. Exosome-based therapies are emerging as potent strategies that can be utilized to alleviate tumor progression. Herein, the present knowledge of exosomal ncRNAs and their vital roles in regulating the interplay between cancer cells and macrophages, as well as their clinical applications are summarized.

Role of Circular RNAs in the Regulation of Immune Cells in Response to Cancer Therapies

Circular RNAs (CircRNAs) are a class of small endogenous noncoding RNA that are formed by means of either the spliceosome or lariat-type splicing. CircRNAs have multiple regulatory functions and have been detected in different cell types, like normal, tumor and immune cells. CircRNAs have been suggested to regulate T cell functions in response to cancer. CircRNAs can enter into T cells and promote the expression of molecules that either trigger antitumoral responses or promote suppression and the consequent evasion to the immune response. Additionally, circRNAs may promote tumor progression and resistance to anticancer treatment in different types of neoplasias. In this minireview we discuss the impact of circRNAs and its function in the regulation of the T-cells in immune response caused by cancer therapies.

Liquid biopsy in lung cancer: significance in diagnostics, prediction, and treatment monitoring

Primary lung cancer is one of the most common malignant tumors in China. Approximately 60% of lung cancer patients have distant metastasis at the initial diagnosis, so it is necessary to find new tumor markers for early diagnosis and individualized treatment. Tumor markers contribute to the early diagnosis of lung cancer and play important roles in early detection and treatment, as well as in precision medicine, efficacy monitoring, and prognosis prediction. The pathological diagnosis of lung cancer in small biopsy specimens determines whether there are tumor cells in the biopsy and tumor type. Because biopsy is traumatic and the compliance of patients with multiple biopsies is poor, liquid biopsy has become a hot research direction. Liquid biopsies are advantageous because they are nontraumatic, easy to obtain, reflect the overall state of the tumor, and allow for real-time monitoring. At present, liquid biopsies mainly include circulating tumor cells, circulating tumor DNA, exosomes, microRNA, circulating RNA, tumor platelets, and tumor endothelial cells. This review introduces the research progress and clinical application prospect of liquid biopsy technology for lung cancer.

The potential role of exosomal circRNAs in the tumor microenvironment: insights into cancer diagnosis and therapy

Exosomes are multifunctional regulators of intercellular communication by carrying various messages under both physiological and pathological status of cancer patients. Accumulating studies have identified the presence of circular RNAs (circRNAs) in exosomes with crucial regulatory roles in diverse pathophysiological processes. Exosomal circRNAs derived from donor cells can modulate crosstalk with recipient cells locally or remotely to enhance cancer development and propagation, and play crucial roles in the tumor microenvironment (TME), leading to significant enhancement of tumor immunity, metabolism, angiogenesis, drug resistance, epithelial mesenchymal transition (EMT), invasion and metastasis. In this review, we describe the advances of exosomal circRNAs and their roles in modulating cancer hallmarks, especially those in the TME. Moreover, clinical application potential of exosomal circRNAs in cancer diagnosis and therapy are highlighted, bridging the gap between basic knowledge and clinical practice.

Emerging noncoding RNAs contained in extracellular vesicles: rising stars as biomarkers in lung cancer liquid biopsy

Lung cancer has a high morbidity and mortality rate, and affected patients have a poor prognosis and low survival. The therapeutic approaches for lung cancer treatment, including surgery, radiotherapy, and chemotherapy, are not completely effective, due to late diagnosis. Although the identification of genetic drivers has contributed to the improvement of lung cancer clinical management, the discovery of new diagnostic and prognostic tools remains a critical issue. Liquid biopsy (LB) represents a minimally invasive approach and practical alternative source to investigate tumor-derived alterations and to facilitate the selection of targeted therapies. LB allows for the testing of different analytes such as circulating tumor cells, extracellular vesicles (EVs), tumor-educated platelets, and cell-free nucleic acids including DNAs, RNAs, and noncoding RNAs (ncRNAs). Several regulatory factors control the key cellular oncogenic pathways involved in cancers. ncRNAs have a wide range of regulatory effects in lung cancers. This review focuses on emerging regulatory ncRNAs, freely circulating in body fluids or shuttled by EVs, such as circular-RNAs, small nucleolar-RNAs, small nuclear-RNAs, and piwi-RNAs, as new biomarkers for early detection, prognosis, and monitoring of therapeutic strategy of lung cancer treatment.