Exosomes Mediated Transfer of Circ_UBE2D2 Enhances the Resistance of Breast Cancer to Tamoxifen by Binding to MiR-200a-3p

The Impact of miRNAs on the Efficacy of Tamoxifen in Breast Cancer Treatment: A Systematic Review

Seventy percent of breast cancer patients have an active estrogen receptor. Tamoxifen interferes with estrogen's ability to bind to cancer cells. The most challenging aspect of tamoxifen, however, is that breast cancer cells become resistant to its effects. Some studies have shown that alterations in miRNA expression contribute significantly to drug resistance in breast cancer. Therefore, the present systematic review aims to investigate miRNAs that significantly influence the response to tamoxifen treatment. The present study follows the PRISMA instructions. The Web of Science, PubMed, and Scopus databases were searched to retrieve English articles. The searches were conducted up to September 11, 2022. The search strategy included the terms "Tamoxifen", "Breast Neoplasm", and "MicroRNA". The inclusion criteria of this study are English, original, and experimental studies investigating miRNAs that are effective in the treatment efficacy of tamoxifen. A total of 565 articles were retrieved. After screening, 75 studies met our inclusion criteria. This systematic review study examined 105 miRNAs, of which 44 have a positive effect, and 47 miRNAs inhibit tamoxifen function. Fourteen miRNAs have a controversial effect, ie, some studies show positive and negative effects. The study of miRNAs affecting tamoxifen function in breast cancer patients may facilitate the identification of individuals at higher risk of disease recurrence. Conversely, it can potentially utilize appropriate interventions to defeat drug resistance effectively.

Drug resistance in breast cancer is based on the mechanism of exocrine non-coding RNA

Breast cancer (BC) ranks first among female malignant tumors and involves hormonal changes and genetic as well as environmental risk factors. In recent years, with the improvement of medical treatment, a variety of therapeutic approaches for breast cancer have emerged and have strengthened to accommodate molecular diversity. However, the primary way to improve the effective treatment of breast cancer patients is to overcome treatment resistance. Recent studies have provided insights into the mechanisms of resistance to exosome effects in BC. Exosomes are membrane-bound vesicles secreted by both healthy and malignant cells that facilitate intercellular communication. Specifically, exosomes released by tumor cells transport their contents to recipient cells, altering their properties and promoting oncogenic components, ultimately resulting in drug resistance. As important coordinators, non-coding RNAs (ncRNAs) are involved in this process and are aberrantly expressed in various human cancers. Exosome-derived ncRNAs, including microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), have emerged as crucial components in understanding drug resistance in breast cancer. This review provides insights into the mechanism of exosome-derived ncRNAs in breast cancer drug resistance, thereby suggesting new strategies for the treatment of BC.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Cancer Therapy Resistance: from Biology to Clinical Opportunity

Mesenchymal stem cells (MSCs) are a type of stromal cells characterized by their properties of self-renewal and multi-lineage differentiation, which make them prominent in regenerative medicine. MSCs have shown significant potential for the treatment of various diseases, primarily through the paracrine effects mediated by soluble factors, specifically extracellular vesicles (EVs). MSC-EVs play a crucial role in intercellular communication by transferring various bioactive substances, including proteins, RNA, DNA, and lipids, highlighting the contribution of MSC-EVs in regulating cancer development and progression. Remarkably, increasing evidence indicates the association between MSC-EVs and resistance to various types of cancer treatments, including radiotherapy, chemotherapy, targeted therapy, immunotherapy, and endocrinotherapy. In this review, we provide an overview of the recent advancements in the biogenesis, isolation, and characterization of MSC-EVs, with an emphasis on their functions in cancer therapy resistance. The clinical applications and future prospects of MSC-EVs for mitigating cancer therapy resistance and enhancing drug delivery are also discussed. Elucidating the role and mechanism of MSC-EVs in the development of treatment resistance in cancer, as well as evaluating the clinical significance of MSC-EVs, is crucial for advancing our understanding of tumor biology. Meanwhile, inform the development of effective treatment strategies for cancer patients in the future.

Circular RNAs in breast cancer diagnosis, treatment and prognosis

Breast cancer has surpassed lung cancer to become the most common malignancy worldwide. The incidence rate and mortality rate of breast cancer continue to rise, which leads to a great burden on public health. Circular RNAs (circRNAs), a new class of noncoding RNAs (ncRNAs), have been recognized as important oncogenes or suppressors in regulating cancer initiation and progression. In breast cancer, circRNAs have significant roles in tumorigenesis, recurrence and multidrug resistance that are mediated by various mechanisms. Therefore, circRNAs may serve as promising targets of therapeutic strategies for breast cancer management. This study reviews the most recent studies about the biosynthesis and characteristics of circRNAs in diagnosis, treatment and prognosis evaluation, as well as the value of circRNAs in clinical applications as biomarkers or therapeutic targets in breast cancer. Understanding the mechanisms by which circRNAs function could help transform basic research into clinical applications and facilitate the development of novel circRNA-based therapeutic strategies for breast cancer treatment.

Circulating tumor biomarkers in early-stage breast cancer: characteristics, detection, and clinical developments

Breast cancer is the most common form of cancer in women, contributing to high rates of morbidity and mortality owing to the ability of these tumors to metastasize via the vascular system even in the early stages of progression. While ultrasonography and mammography have enabled the more reliable detection of early-stage breast cancer, these approaches entail high rates of false positive and false negative results Mammograms also expose patients to radiation, raising clinical concerns. As such, there is substantial interest in the development of more accurate and efficacious approaches to diagnosing breast cancer in its early stages when patients are more likely to benefit from curative treatment efforts. Blood-based biomarkers derived from the tumor microenvironment (TME) have frequently been studied as candidate targets that can enable tumor detection when used for patient screening. Through these efforts, many promising biomarkers including tumor antigens, circulating tumor cell clusters, microRNAs, extracellular vesicles, circulating tumor DNA, metabolites, and lipids have emerged as targets that may enable the detection of breast tumors at various stages of progression. This review provides a systematic overview of the TME characteristics of early breast cancer, together with details on current approaches to detecting blood-based biomarkers in affected patients. The limitations, challenges, and prospects associated with different experimental and clinical platforms employed in this context are also discussed at length.

The role of non-coding RNAs in extracellular vesicles in breast cancer and their diagnostic implications

Breast Cancer (BC) is the most common form of cancer worldwide, responsible for 25% of cancers in women. Whilst treatment is effective and often curative in early BC, metastatic disease is incurable, highlighting the need for early detection. Currently, early detection relies on invasive procedures, however recent studies have shown extracellular vesicles (EVs) obtained from liquid biopsies may have clinical utility. EVs transport diverse bioactive cargos throughout the body, play major roles in intercellular communication and, importantly, mirror their cell of origin. In cancer cells, EVs alter the behaviour of the tumour microenvironment (TME), forming a bridge of communication between cancerous and non-cancerous cells to alter all aspects of cancer progression, including the formation of a pre-metastatic niche. Through gene regulatory frameworks, non-coding RNAs (ncRNAs) modulate vital molecular and cellular processes and can act as both tumour suppressors and oncogenic drivers in various cancer types. EVs transport and protect ncRNAs, facilitating their use clinically as liquid biopsies for early BC detection. This review summarises current research surrounding ncRNAs and EVs within BC, focusing on their roles in cancer progression through bi-directional communication with the microenvironment and their diagnostic implications. The role of EV ncRNAs in breast cancer. A representation of the different EV ncRNAs involved in tumourigenic processes in breast cancer. Pro-tumourigenic ncRNAs displayed in green and ncRNAs which inhibit oncogenic processes are shown in red.

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.

Exosomes are involved in the intercellular transfer of rapamycin resistance in the breast cancer cells

Introduction

Resistance to chemotherapy and/or irradiation remains one of the key features of malignant tumors, which largely limits the efficiency of antitumor therapy. In this work, we studied the progression mechanism of breast cancer cell resistance to target drugs, including mTOR blockers, and in particular, we studied the exosome function in intercellular resistance transfer.

Methods

The cell viability was assessed by the MTT assay, exosomes were purified by successive centrifugations, immunoblotting was used to evaluate protein expression, AP-1 activity was analyzed using reporter assay.

Results

In experiments on the MCF-7 cell line (breast cancer) and the MCF-7/Rap subline that is resistant to rapamycin, the capability of resistant cell exosomes to trigger a similar rapamycin resistance in the parent MCF-7 cells was demonstrated. Exosome-induced resistance reproduces the changes revealed in MCF-7/Rap resistant cells, including the activation of ERK/AP-1 signaling, and it remains for a long time, for at least several months, after exosome withdrawal. We have shown that both the MCF-7 subline resistant to rapamycin and cells having exosome-triggered resistance demonstrate a stable decrease in the expression of DNMT3A, the key enzyme responsible for DNA methylation. Knockdown of DNMT3A in MCF-7 cells by siRNA leads to partial cell resistance to rapamycin; thus, the DNMT3A suppression is regarded as one of the necessary elements for the development of acquired rapamycin resistance.

Conclusion

We propose that DNA demethylation followed by increased expression of key genes may be one of the factors responsible for the progression and maintenance of the resistant cell phenotype that includes exosome-induced resistance.

Mechanisms of circRNA/lncRNA-miRNA interactions and applications in disease and drug research

In recent years, breakthroughs in bioinformatics have been made with the discovery of many functionally significant non-coding RNAs (ncRNAs). The discovery of these ncRNAs has further demonstrated the multi-level characteristics of intracellular gene expression regulation, which plays an important role in assisting diagnosis, guiding clinical drug use and determining prognosis in the treatment process of various diseases. microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) are the three major types of ncRNAs that interact with each other. Studies have shown that lncRNAs and circRNAs can sponge miRNAs, thereby influencing normal physiological processes and regulating mRNA expression and, thus, the physiological state of cells. This paper summarizes the mechanism of action and research progress of the three ncRNA and seven types of modalities. This summary is intended to provide new ideas for diagnosing and treating diseases and researching and developing new drugs.

Non-Coding RNAs Modulating Estrogen Signaling and Response to Endocrine Therapy in Breast Cancer

The largest part of human DNA is transcribed into RNA that does not code for proteins. These non-coding RNAs (ncRNAs) are key regulators of protein-coding gene expression and have been shown to play important roles in health, disease and therapy response. Today, endocrine therapy of ERα-positive breast cancer (BC) is a successful treatment approach, but resistance to this therapy is a major clinical problem. Therefore, a deeper understanding of resistance mechanisms is important to overcome this resistance. An increasing amount of evidence demonstrate that ncRNAs affect the response to endocrine therapy. Thus, ncRNAs are considered versatile biomarkers to predict or monitor therapy response. In this review article, we intend to give a summary and update on the effects of microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) on estrogen signaling in BC cells, this pathway being the target of endocrine therapy, and their role in therapy resistance. For this purpose, we reviewed articles on these topics listed in the PubMed database. Finally, we provide an assessment regarding the clinical use of these ncRNA types, particularly their circulating forms, as predictive BC biomarkers and their potential role as therapy targets to overcome endocrine resistance.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

Inferring disease-associated circRNAs by multi-source aggregation based on heterogeneous graph neural network

Emerging evidence has proved that circular RNAs (circRNAs) are implicated in pathogenic processes. They are regarded as promising biomarkers for diagnosis due to covalently closed loop structures. As opposed to traditional experiments, computational approaches can identify circRNA-disease associations at a lower cost. Aggregating multi-source pathogenesis data helps to alleviate data sparsity and infer potential associations at the system level. The majority of computational approaches construct a homologous network using multi-source data, but they lose the heterogeneity of the data. Effective methods that use the features of multi-source data are considered as a matter of urgency. In this paper, we propose a model (CDHGNN) based on edge-weighted graph attention and heterogeneous graph neural networks for potential circRNA-disease association prediction. The circRNA network, micro RNA network, disease network and heterogeneous network are constructed based on multi-source data. To reflect association probabilities between nodes, an edge-weighted graph attention network model is designed for node features. To assign attention weights to different types of edges and learn contextual meta-path, CDHGNN infers potential circRNA-disease association based on heterogeneous neural networks. CDHGNN outperforms state-of-the-art algorithms in terms of accuracy. Edge-weighted graph attention networks and heterogeneous graph networks have both improved performance significantly. Furthermore, case studies suggest that CDHGNN is capable of identifying specific molecular associations and investigating biomolecular regulatory relationships in pathogenesis. The code of CDHGNN is freely available at https://github.com/BioinformaticsCSU/CDHGNN.

The landscape of exosomal non-coding RNAs in breast cancer drug resistance, focusing on underlying molecular mechanisms

Breast cancer (BC) is the most common malignancy among women worldwide. Like many other cancers, BC therapy is challenging and sometimes frustrating. In spite of the various therapeutic modalities applied to treat the cancer, drug resistance, also known as, chemoresistance, is very common in almost all BCs. Undesirably, a breast tumor might be resistant to different curative approaches (e.g., chemo- and immunotherapy) at the same period of time. Exosomes, as double membrane-bound extracellular vesicles 1) secreted from different cell species, can considerably transfer cell products and components through the bloodstream. In this context, non-coding RNAs (ncRNAs), including miRNAs, long ncRNAs (lncRNAs), and circular RNAs (circRNAs), are a chief group of exosomal constituents with amazing abilities to regulate the underlying pathogenic mechanisms of BC, such as cell proliferation, angiogenesis, invasion, metastasis, migration, and particularly drug resistance. Thereby, exosomal ncRNAs can be considered potential mediators of BC progression and drug resistance. Moreover, as the corresponding exosomal ncRNAs circulate in the bloodstream and are found in different body fluids, they can serve as foremost prognostic/diagnostic biomarkers. The current study aims to comprehensively review the most recent findings on BC-related molecular mechanisms and signaling pathways affected by exosomal miRNAs, lncRNAs, and circRNAs, with a focus on drug resistance. Also, the potential of the same exosomal ncRNAs in the diagnosis and prognosis of BC will be discussed in detail.

Exosomal circular RNAs: New player in breast cancer progression and therapeutic targets

Breast cancer is the most prevalent type of malignancy among women. Exosomes are extracellular vesicles of cell membrane origin that are released via exocytosis. Their cargo contains lipids, proteins, DNA, and different forms of RNA, including circular RNAs. Circular RNAs are new class of non-coding RNAs with a closed-loop shape involved in several types of cancer, including breast cancer. Exosomes contained a lot of circRNAs which are called exosomal circRNAs. By interfering with several biological pathways, exosomal circRNAs can have either a proliferative or suppressive role in cancer. The involvement of exosomal circRNAs in breast cancer has been studied with consideration to tumor development and progression as well as its effects on therapeutic resistance. However, its exact mechanism is still unclear, and there have not been available clinical implications of exo-circRNAs in breast cancer. Here, we highlight the role of exosomal circRNAs in breast cancer progression and to highlight the most recent development and potential of circRNAas therapeutic targets and diagnostics for breast cancer.

Extracellular Vesicles in Cancer Drug Resistance: Roles, Mechanisms, and Implications

Extracellular vesicles (EVs) are cell-derived nanosized vesicles that mediate cell-to-cell communication via transporting bioactive molecules and thus are critically involved in various physiological and pathological conditions. EVs contribute to different aspects of cancer progression, such as cancer growth, angiogenesis, metastasis, immune evasion, and drug resistance. EVs induce the resistance of cancer cells to chemotherapy, radiotherapy, targeted therapy, antiangiogenesis therapy, and immunotherapy by transferring specific cargos that affect drug efflux and regulate signaling pathways associated with epithelial-mesenchymal transition, autophagy, metabolism, and cancer stemness. In addition, EVs modulate the reciprocal interaction between cancer cells and noncancer cells in the tumor microenvironment (TME) to develop therapy resistance. EVs are detectable in many biofluids of cancer patients, and thus are regarded as novel biomarkers for monitoring therapy response and predicting prognosis. Moreover, EVs are suggested as promising targets and engineered as nanovehicles to deliver drugs for overcoming drug resistance in cancer therapy. In this review, the biological roles of EVs and their mechanisms of action in cancer drug resistance are summarized. The preclinical studies on using EVs in monitoring and overcoming cancer drug resistance are also discussed.

Biological functions and potential implications of circular RNAs

Circular RNAs (circRNAs) are characterized by a covalent closed-loop structure with an absence of both 5' cap structure and 3' polyadenylated tail. Numerous studies have found that circRNAs play an important role in various diseases and have a variety of biological regulatory mechanisms, including acting as microRNA sponges, interacting with proteins, modulating the expression of related genes and translating into peptides or proteins. CircRNAs have also been used as biomarkers for a number of diseases, which could improve clinical practice. This review summarizes the most recent advances in biogenesis and knowledge of the biological functions of circRNAs as well as the related bioinformatics databases. We specifically describe developments in understanding of circRNA functions in the field of environmental exposure-induced diseases. Finally, we focus on potential clinical implications of circRNAs to facilitate their clinical transformation into disease treatment.

The role of CircRNA/miRNA/mRNA axis in breast cancer drug resistance

Multidrug resistance is one of the major obstacles in the treatment of cancers. This undesirable feature increases the mortality rate of cancers, including breast cancer. Circular RNA (CircRNA)/microRNA (miRNA)/messenger RNA (mRNA) is one of the important axes with major roles in the promotion and resistance of breast cancer. This heterogeneous pathway includes mRNA of oncogenes and tumor suppressors, which are controlled by miRNAs and CircRNAs. Unfortunately, this network could be easily deregulated, resulting in drug resistance and tumor development. Therefore, understanding these dysregulations may thus help to identify effective therapeutic targets. On this basis, we try to review the latest findings in the field, which could help us to better comprehend this significant axis in breast cancer.

CircRNA RNF10 inhibits tumorigenicity by targeting miR-942-5p/GOLIM4 axis in breast cancer

We aimed to explore the action of a circRNA produced by ring finger protein 10 (circ_RNF10; hsa_circ_0028899) in the malignant behaviors of breast cancer (BC) and to explore its potential action-of-mechanism. The levels of circ_RNF10, miR-942-5p and Golgi integral membrane protein 4 (GOLIM4) were measured through quantitative real-time polymerase chain reaction, western blot, or immunohistochemistry, and the competing endogenous RNA (ceRNA) relationship among them was verified by dual-luciferase reporter assay. Cell counting kit-8, 5-ethynyl-2'-deoxyuridine, and colony formation assays, transwell assays, and flow cytometry were used to examine cell proliferation, migration and invasion, and apoptosis, respectively. Levels of proliferation and invasion-related markers were determined by western blot. Xenograft assay was performed to assess tumor growth. Circ_RNF10 level was significantly reduced in BC tissues and cells. Elevation of circ_RNF10 blocked BC cell proliferation, migration and invasion while promoted the apoptosis in vitro, companied with decreased PCNA and Twist1 and increased E-cadherin. Furthermore, upregulating circ_RNF10 delayed tumor growth of BC cells in nude mice. Mechanistically, circ_RNF10 acted as a ceRNA for miR-942-5p, and miR-942-5p could target GOLIM4. In addition, miR-942-5p overexpression reversed the influence of circ_RNF10 overexpression on BC progression. Furthermore, GOLIM4 silencing attenuated the inhibitory effect of miR-942-5p knockdown on BC progression. We found that circ_RNF10 suppressed BC malignant behavior by targeting miR-942-5p/GOLIM4 axis.

Spotlight on Exosomal Non-Coding RNAs in Breast Cancer: An In Silico Analysis to Identify Potential lncRNA/circRNA-miRNA-Target Axis

Breast cancer (BC) has recently become the most common cancer type worldwide, with metastatic disease being the main reason for disease mortality. This has brought about strategies for early detection, especially the utilization of minimally invasive biomarkers found in various bodily fluids. Exosomes have been proposed as novel extracellular vesicles, readily detectable in bodily fluids, secreted from BC-cells or BC-tumor microenvironment cells, and capable of conferring cellular signals over long distances via various cargo molecules. This cargo is composed of different biomolecules, among which are the novel non-coding genome products, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and the recently discovered circular RNA (circRNA), all of which were found to be implicated in BC pathology. In this review, the diverse roles of the ncRNA cargo of BC-derived exosomes will be discussed, shedding light on their primarily oncogenic and additionally tumor suppressor roles at different levels of BC tumor progression, and drug sensitivity/resistance, along with presenting their diagnostic, prognostic, and predictive biomarker potential. Finally, benefiting from the miRNA sponging mechanism of action of lncRNAs and circRNAs, we established an experimentally validated breast cancer exosomal non-coding RNAs-regulated target gene axis from already published exosomal ncRNAs in BC. The resulting genes, pathways, gene ontology (GO) terms, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis could be a starting point to better understand BC and may pave the way for the development of novel diagnostic and prognostic biomarkers and therapeutics.

Circ_UBE2D2 Attenuates the Progression of Septic Acute Kidney Injury in Rats by Targeting miR-370-3p/NR4A3 Axis

As circ_UBE2D2 has been confirmed to have targeted binding sites with multiple miRNAs involved in septic acute kidney injury (SAKI), efforts in this study are directed to unveiling the specific role and relevant mechanism of circ_UBE2D2 in SAKI. HK-2 cells were treated with lipopolysaccharide (LPS) to construct SAKI model in vitro. After sh-circ_UBE2D2 was transfected into cells, the transfection efficiency was detected by qRT-PCR, cell viability and apoptosis were determined by MTT assay and flow cytometry, and expressions of Bcl-2, Bax and Cleaved-caspase 3 were quantified by western blot. Target genes associated with circ_UBE2D2 were predicted using bioinformatics analysis. After the establishment of SAKI rat model, HE staining and TUNEL staining were exploited to observe the effect of circ_UBE2D2 on tissue damage and cell apoptosis. The expression of circ_UBE2D2 was overtly elevated in LPS-induced HK-2 cells. Sh-circ_UBE2D2 can offset the inhibition of cell viability and the promotion of cell apoptosis induced by LPS. Circ_UBE2D2 and miR-370-3p as well as miR-370-3p and NR4A3 have targeted binding sites. MiR-370-3p inhibitor reversed the promoting effect of circ_UB2D2 silencing on viability of LPS-treated cells, but shNR4A3 neutralized the above inhibitory effect of miR-370-3p inhibitor. MiR-370-3p inhibitor weakened the down-regulation of NR4A3, Bax and Cleaved caspase-3 and the up-regulation of Bcl-2 induced by circ_UB2D2 silencing, but these trends were reversed by shNR4A3. In addition, sh-circ_UBE2D2 could alleviate the damage of rat kidney tissue. Circ_UBE2D2 mitigates the progression of SAKI in rats by targeting miR-370-3p/NR4A3 axis.

Exosome-Mediated Response to Cancer Therapy: Modulation of Epigenetic Machinery

Exosomes, the extracellular vesicles produced in the endosomal compartments, facilitate the transportation of proteins as well as nucleic acids. Epigenetic modifications are now considered important for fine-tuning the response of cancer cells to various therapies, and the acquired resistance against targeted therapies often involves dysregulated epigenetic modifications. Depending on the constitution of their cargo, exosomes can affect several epigenetic events, thus impacting post-transcriptional regulations. Thus, a role of exosomes as facilitators of epigenetic modifications has come under increased scrutiny in recent years. Exosomes can deliver methyltransferases to recipient cells and, more importantly, non-coding RNAs, particularly microRNAs (miRNAs), represent an important exosome cargo that can affect the expression of several oncogenes and tumor suppressors, with a resulting impact on cancer therapy resistance. Exosomes often harbor other non-coding RNAs, such as long non-coding RNAs and circular RNAs that support resistance. The exosome-mediated transfer of all this cargo between cancer cells and their surrounding cells, especially tumor-associated macrophages and cancer-associated fibroblasts, has a profound effect on the sensitivity of cancer cells to several chemotherapeutics. This review focuses on the exosome-induced modulation of epigenetic events with resulting impact on sensitivity of cancer cells to various therapies, such as, tamoxifen, cisplatin, gemcitabine and tyrosine kinase inhibitors. A better understanding of the mechanisms by which exosomes can modulate response to therapy in cancer cells is critical for the development of novel therapeutic strategies to target cancer drug resistance.

Advances in the Study of CircRNAs in Tumor Drug Resistance

Recent studies have revealed that circRNAs can affect tumor DNA damage and repair, apoptosis, proliferation, and invasion and influence the transport of intratumor substances by acting as miRNA sponges and transcriptional regulators and binding to proteins in a variety of ways. However, research on the role of circRNAs in cancer radiotherapy and chemoresistance is still in its early stages. Chemotherapy is a common approach to oncology treatment, but the development of tumor resistance limits the overall clinical efficacy of chemotherapy for cancer patients. The current study suggests that circRNAs have a facilitative or inhibitory effect on the development of resistance to conventional chemotherapy in a variety of tumors, suggesting that circRNAs may serve as a new direction for the study of antitumor drug resistance. In this review, we will briefly discuss the biological features of circRNAs and summarize the recent progression of the involvement of circRNAs in the development and pathogenesis of cancer chemoresistance.

Circular RNAs and Their Role in Exosomes

As a novel class of endogenous non-coding RNAs discovered in recent years, circular RNAs (circRNAs) are highly conserved and stable covalently closed ring structures with no 5'-end cap or 3'-end poly(A) tail. CircRNAs are formed by reverse splicing, mainly by means of a noose structure or intron complementary pairing. Exosomes are tiny discoid vesicles with a diameter of 40-100 nm that are secreted by cells under physiological and pathological conditions. Exosomes play an important role in cell-cell communication by carrying DNA, microRNAs, mRNAs, proteins and circRNAs. In this review, we summarize the biological functions of circRNAs and exosomes, and further reveal the potential roles of exosomal circRNAs in different diseases, providing a scientific basis for the diagnosis, treatment, and prognosis of a wide variety of diseases.

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.

CircCDK1 knockdown reduces CDK1 expression by targeting miR-489-3p to suppress the development of breast cancer and strengthen the sensitivity of Tamoxifen

Circular RNAs (circRNAs) are implicated with the progression of multiple cancers, including breast cancer. Besides, circRNA dysregulation is involved in the chemoresistance of cancer development. This study aimed to investigate the role of circRNA-cyclin dependent kinase 1 (circCDK1) in breast cancer. Quantitative real-time PCR (qPCR) and western blot were applied for expression analysis. Cell viability was determined by the cell counting kit-8 (CCK-8). Cell proliferation was evaluated by CCK-8, colony formation and 5-ethynyl-2'-deoxyuridine assays. Cell apoptosis was assessed by flow cytometry and the activities of caspase3 and caspase9. The potential binding between miR-489-3p and circCDK1 or CDK1 was verified by RNA immunoprecipitation assay, dual-luciferase reporter assay and pull-down assay. Animal models were constructed to explore the role of circCDK1 in vivo. CircCDK1 was overexpressed in Tamoxifen-resistant breast cancer cells, LCC2 and LCC9. The expression of circCDK1 in tumor tissues with Tamoxifen resistance was higher than that in tissues without Tamoxifen resistance. CircCDK1 knockdown strengthened the sensitivity of Tamoxifen in LCC2 and LCC9 cells and reduced Tamoxifen IC50. The downregulation of circCDK1 inhibited LCC2 andLCC9 cell proliferation and promoted cell apoptosis. CDK1 was the parent gene of circCDK1 and circCDK1 positively regulated CDK1 expression by targeting miR- 489-3p. CDK1 overexpression reversed the effects of circCDK1 knockdown. MiR-489-3p inhibition also reversed the effects of circCDK1 knockdown. CircCDK1 knockdown was verified to enhance Tamoxifen sensitivity in animal models. CircCDK1 knockdown enhanced the sensitivity of Tamoxifen in breast cancer cells and suppressed cell growth and survival by depleting CDK1 expression via releasing miR- 489-3p.

Circular RNA-UBE2D2 accelerates the proliferation and metastasis of non-small cell lung cancer cells via modulating microRNA-376a-3p/Eukaryotic Translation Initiation Factor 4γ2 axis

Non-small cell lung cancer (NSCLC) ranks first in the morbidity and mortality of malignant tumors in China. As reported, circular RNAs (circRNAs) are emerged in the progress of NSCLC. The study was to figure out the potential mechanism of circ-UBE2D2 in the progression of NSCLC. First, plasmid vectors intervening circ-UBE2D2, microRNA (miR)-376a-3p or Eukaryotic Translation Initiation Factor 4γ2 (EIF4G2) expression were transfected into NSCLC cells, and the expression of circ-UBE2D2, miR-376a-3p and EIF4G2 was detected by reverse transcription quantitative polymerase chain reaction or Western blot. Then, cell proliferation was detected by Cell counting kit-8 assay and plate cloning. Cell apoptosis was tested by flow cytometry. Plate scratches and Transwell were used to detect cell migration and invasion. Finally, the binding sites of circRNA UBE2D2, EIF4G2 and miR-376a-3p were verified by bioinformatics website starBase analysis and dual luciferase reporter gene assay. The results manifested the up-regulation of circ-UBE2D2 expression in NSCLC tissues and cells. Circ-UBE2D2 promoted the proliferation, migration and invasion, but repressed apoptosis of NSCLC cells. Interestingly, circ-UBE2D2 directly targeted miR-376a-3p and up-regulated miR-376a-3p restrained proliferation, migration and invasion, but accelerated apoptosis of NSCLC cells. More importantly, EIF4G2 was the target of miR-376a-3p, and overexpression of EIF4G2 reversed the effects of circ-UBE2D2 downregulation on proliferation, migration, invasion and apoptosis of NSCLC cells. These results suggest that circ-UBE2D2 promotes the proliferation, migration and invasion but restrains apoptosis of lung cancer cells by regulating miR-376a-3p/EIF4G2 axis.

Enigmatic role of exosomes in breast cancer progression and therapy

Breast cancer (BC) is reported to be the leading cause of mortality in females worldwide. At the beginning of the year 2021, about 7.8 million women were diagnosed with BC in past 5 years. High prevalence and poor neoadjuvant chemotherapeutic efficacy has motivated the scientists around the globe to investigate alternative management strategies. In recent years, there has been an exponential rise in the scientific studies reporting the role of tumor derived exosomes (TDEs) in the BC pathophysiology and management. TDEs play an important role in the intercellular communication and transportation of biomolecules. This manuscript reviews the role of exosomes in the BC pathophysiology, diagnosis, and therapy. Role of TDEs in the mechanistic pathways of BC metastasis, immunosuppression, migration, dormancy and chemo-resistance is extensively reviewed. We have also highlighted the epigenetic modulations orchestrated by exosomal miRNAs and long noncoding RNAs (lnc RNAs) in the BC environment. Liquid biopsies analyzing blood circulating exosomes for early and accurate detection of the BC have been discussed. Characterization of exosomes, strategies to use them in BC chemotherapy, BC immunotherapy and potential challenges that will present themselves in translating exosomes based technologies to market are discussed.

CircFBXW8 Acts an Oncogenic Role in the Malignant Progression of Non-small Cell Lung Carcinoma by miR-370-3p-Dependent Regulation of TRIM44

Non-small cell lung carcinoma (NSCLC) is an aggressive malignant tumor. Growing evidences have revealed that circular RNA (circRNA) is involved in NSCLC progression. This study aims to investigate the role of circular RNA F-box and WD repeat domain containing 8 (circFBXW8) in NSCLC progression and the underlying mechanism. The expression of circFBXW8, microRNA-370-3p (miR-370-3p) and tripartite motif containing 44 (TRIM44) mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was detected by western blot analysis or immunohistochemistry assay. Additionally, cell viability, colony-forming ability, proliferation and apoptosis were investigated by 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide, cell colony formation, 5-Ethynyl-29-deoxyuridine and flow cytometry analysis assays, respectively. Cell migratory and invasive abilities were examined by wound-healing and transwell assays. The regulatory relationship between miR-370-3p and circFBXW8 or TRIM44 was identified by dual-luciferase reporter and RNA pull-down assays. Furthermore, xenograft experiment was employed to explain the effect of circFBXW8 silencing on tumor formation. CircFBXW8 and TRIM44 expression were upregulated, while miR-370-3p was downregulated in NSCLC tissues, cells and the exosomes from NSCLC cells compared with respective controls. CircFBXW8 depletion repressed NSCLC cell proliferation, migration and invasion, but promoted cell apoptosis. CircFBXW8 acted as a sponge of miR-370-3p and regulated NSCLC cell malignancy by binding to miR-370-3p. Additionally, miR-370-3p repressed NSCLC cell processes by regulating TRIM44. CircFBXW8 knockdown inhibited tumor formation in vivo. Further, circFBXW8 secretion was mediated by exosomes. CircFBXW8 modulated NSCLC progression by increasing TRIM44 expression through sponging miR-370-3p, which provided a new direction for studying the therapy of NSCLC.

Exosomal circRNAs: Emerging Players in Tumor Metastasis

Metastasis is an important feature of malignant tumors, and is the primary cause of poor prognosis and treatment failure, in addition to representing a potentially fatal challenge for cancer patients. Exosomes are small extracellular vesicles 30–150 nm in diameter that transmit cargo, such as DNA, RNA, and proteins, as a means of intercellular communication. Exosomes play crucial roles in a range of human diseases, especially malignant tumors. A growing number of studies have verified that circRNAs can be enveloped in exosomes and transferred from secretory cells to recipient cells, thereby regulating tumor progression, especially tumor metastasis. Exosomal circRNAs regulate tumor cell metastasis not only by regulating the signaling pathways, but also by affecting the tumor microenvironment. Moreover, exosomal circRNAs have the potential to serve as valuable diagnostic biomarkers and novel therapeutic targets in cancer patients. In this review, we summarize the mechanism by which exosomal circRNAs modulate metastatic phenomena in various types of tumors, and put forward the prospects of clinical applications of exosomal circRNAs in tumor therapy.

Exosomal circRNAs: a new communication method in cancer

Exosomes are extracellular vesicles with unique membrane markers and components that participate in cellular communication. The contents of exosomes, including growth factors, microRNAs, long noncoding RNAs, and circular RNAs (circRNAs), have been recognized as prognostic biomarkers and promote cancer progression through cancer cell growth, metastasis, angiogenesis, and cancer development. One of the components of exosomes, circRNAs, are covalently closed and prevented from degrading, which results in their continually accumulating in exosomes. Evidence suggests that exosomal circRNAs are abundant and stable in body fluids and have been implicated in many diseases. In this article we summarize the biogenesis and function of circRNAs and explore the expressions of exosomal circRNAs in cancer, emphasizing the fact that exosomal circRNAs are a novel diagnostic biomarker in the early stages of cancer and/or a therapeutic target in further cancer treatment.

Towards Unravelling the Role of ERα-Targeting miRNAs in the Exosome-Mediated Transferring of the Hormone Resistance

Hormone therapy is one of the most effective breast cancer treatments, however, its application is limited by the progression of hormonal resistance, both primary or acquired. The development of hormonal resistance is caused either by an irreversible block of hormonal signalling (suppression of the activity or synthesis of hormone receptors), or by activation of oestrogen-independent signalling pathways. Recently the effect of exosome-mediated intercellular transfer of hormonal resistance was revealed, however, the molecular mechanism of this effect is still unknown. Here, the role of exosomal miRNAs (microRNAs) in the transferring of hormonal resistance in breast cancer cells has been studied. The methods used in the work include extraction, purification and RNAseq of miRNAs, transfection of miRNA mimetics, immunoblotting, reporter analysis and the MTT test. Using MCF7 breast cancer cells and MCF7/T tamoxifen-resistant sub-line, we have found that some miRNAs, suppressors of oestrogen receptor signalling, are overexpressed in the exosomes of the resistant breast cancer cells. The multiple (but not single) transfection of one of the identified miRNA, miR-181a-2, into oestrogen-dependent MCF7 cells induced the irreversible tamoxifen resistance associated with the continuous block of the oestrogen receptor signalling and the activation of PI3K/Akt pathway. We suppose that the miRNAs-ERα suppressors may act as trigger agents inducing the block of oestrogen receptor signalling and breast cancer cell transition to an aggressive oestrogen-independent state.

Tumor-Derived Exosomal Non-Coding RNAs: The Emerging Mechanisms and Potential Clinical Applications in Breast Cancer

Breast cancer (BC) is the most frequent malignancy and is ranking the leading cause of cancer-related death among women worldwide. At present, BC is still an intricate challenge confronted with high invasion, metastasis, drug resistance, and recurrence rate. Exosomes are membrane-enclosed extracellular vesicles with the lipid bilayer and recently have been confirmed as significant mediators of tumor cells to communicate with surrounding cells in the tumor microenvironment. As very important orchestrators, non-coding RNAs (ncRNAs) are aberrantly expressed and participate in regulating gene expression in multiple human cancers, while the most reported ncRNAs within exosomes in BC are microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Notably, ncRNAs containing exosomes are novel frontiers to shape malignant behaviors in recipient BC cells such as angiogenesis, immunoregulation, proliferation, and migration. It means that tumor-derived ncRNAs-containing exosomes are pluripotent carriers with intriguing and elaborate roles in BC progression via complex mechanisms. The ncRNAs in exosomes are usually excavated based on specific de-regulated expression verified by RNA sequencing, bioinformatic analyses, and PCR experiments. Here, this article will elucidate the recent existing research on the functions and mechanisms of tumor-derived exosomal miRNA, lncRNA, circRNA in BC, especially in BC cell proliferation, metastasis, immunoregulation, and drug resistance. Moreover, these tumor-derived exosomal ncRNAs that existed in blood samples are proved to be excellent diagnostic biomarkers for improving diagnosis and prognosis. The in-depth understanding of tumor-derived exosomal ncRNAs in BC will provide further insights for elucidating the BC oncogenesis and progress and exploring novel therapeutic strategies for combating BC.

The Role of Non-Coding RNAs in Breast Cancer Drug Resistance

Breast cancer (BC) is one of the commonly occurring malignancies in females worldwide. Despite significant advances in therapeutics, the mortality and morbidity of BC still lead to low survival and poor prognosis due to the drug resistance. There are certain chemotherapeutic, endocrine, and target medicines often used for BC patients, including anthracyclines, taxanes, docetaxel, cisplatin, and fluorouracil. The drug resistance mechanisms of these medicines are complicated and have not been fully elucidated. It was reported that non-coding RNAs (ncRNAs), such as micro RNAs (miRNA), long-chain non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) performed key roles in regulating tumor development and mediating therapy resistance. However, the mechanism of these ncRNAs in BC chemotherapeutic, endocrine, and targeted drug resistance was different. This review aims to reveal the mechanism and potential functions of ncRNAs in BC drug resistance and to highlight the ncRNAs as a novel target for achieving improved treatment outcomes for BC patients.

Circular RNA FAT atypical cadherin 1 (circFAT1)/microRNA-525-5p/spindle and kinetochore-associated complex subunit 1 (SKA1) axis regulates oxaliplatin resistance in breast cancer by activating the notch and Wnt signaling pathway

Increasing evidence has confirmed the vital roles of circular RNAs (CircRNAs) in the drug resistance of breast cancer (BC). Herein, we intended to study the effect of circular RNA FAT atypical cadherin 1 (circFAT1) on BC oxaliplatin (OX) resistance and find out the potential molecular mechanism in it. In this study, mRNA and protein levels of genes were measured by RT-qPCR and western blotting, respectively. Luciferase reporter assay confirmed the relationship between microRNA-525-5p (miR-525-5p) and circFAT1 or spindle and kinetochore-associated complex subunit 1 (SKA1). CCK-8, transwell, and flow cytometry experiments were utilized to investigate the chemosensitivity, migration, invasion, and apoptosis of BC cells. Gene Set Enrichment Analysis (GSEA) was applied to discover possible pathways related to SKA1. It was uncovered that circFAT1 was overexpressed in OX-resistant BC tissues and cells. Functional experiments showed that circFAT1 depletion reduced the level of chemoresistance-related genes. Moreover, circFAT1 knockdown remarkably facilitated apoptosis and decreased OX (half-maximal inhibitory concentration) IC₅₀ value, migration, and invasion in OX-resistant BC cells. It was identified that miR-525-5p directly targeted circFAT1 and SKA1. Besides, rescue assays exhibited that circFAT1 promoted OX resistance in BC cells via the miR-525-5p/SKA1 regulatory network. Furthermore, GSEA and western blotting identified that SKA1 activated the Notch and Wnt pathway in OX-resistant BC cells. In conclusion, our results demonstrated that circFAT1 conferred OX resistance in BC by regulating the miR-525-5p/SKA1 via the Notch and Wnt pathway, providing a potential therapeutic target for patients with OX-resistant BC.

The Regulation Network and Clinical Significance of Circular RNAs in Breast Cancer

Breast cancer is one of the most common malignant tumors in women worldwide. Circular RNA (circRNA) is a class of structurally stable non-coding RNA with a covalently closed circular structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been discovered and have proven to be clinically significant in the development and progression of breast cancer. Importantly, several regulators of circRNA biogenesis have been discovered. Here, we systematically summarize recent progress regarding the network of regulation governing the biogenesis, degradation, and distribution of circRNAs, and we comprehensively analyze the functions, mechanisms, and clinical significance of circRNA in breast cancer.

Exosomes Mediated Transfer of Circ_0000337 Contributes to Cisplatin (CDDP) Resistance of Esophageal Cancer by Regulating JAK2 via miR-377-3p

Background: Chemoresistance remains a major obstacle to the treatment of esophageal cancer patients. Exosome-mediated transfer of circular RNAs (circRNAs) has been reported to be related to drug resistance in esophageal cancer. This study is designed to explore the role and mechanism of exosomal circ_0000337 on CDDP resistance in esophageal cancer. Methods: Cell viability, proliferation, colony number, apoptosis, migration, and invasion were assessed by Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, and transwell assays. Circ_0000337, microRNA-377 (miR-377-3p), and Janus kinase 2 (JAK2) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Exosomes were isolated and detected by differential centrifugation and a transmission electron microscope. Protein levels of CD9, CD63, and JAK2 were tested by Western blot assay. The binding relationship between miR-377-3p and circ_0000337 or JAK2 was predicted by circinteractome or Starbase and then verified by dual-luciferase reporter assay and RNA pull-down assay. The biological role of exosomal circ_0000337 and CDDP on esophageal cancer cell growth was examined by the xenograft tumor model in vivo. Results: Circ_0000337 and JAK2 were highly expressed, and miR-377-3p was decreased in CDDP-resistant esophageal cancer tissues and cells. Moreover, circ_0000337-containing exosomes secreted by CDDP-resistant esophageal cancer cells could promote CDDP resistance, cell growth, and metastasis in CDDP-sensitive esophageal cancer cells in vitro. The mechanical analysis discovered that circ_0000337 functioned as a sponge of miR-377-3p to regulate JAK2 expression. Exosomal circ_0000337 increased the drug resistance of esophageal cancer in vivo. Conclusion: Exosomal circ_0000337 accelerated CDDP resistance of esophageal cancer cells partly by regulating the miR-377-3p/JAK2 axis, hinting a promising therapeutic target for the esophageal cancer treatment.

Circular RNA circ-MMP11 Contributes to Lapatinib Resistance of Breast Cancer Cells by Regulating the miR-153-3p/ANLN Axis

Background

Drug-resistance is a major obstacle to the treatment of breast cancer. Circular RNA (circRNA) circ-MMP11 has been reported to be promoting the progression of breast cancer. This study is designed to explore the role and mechanism of circ-MMP11 in lapatinib resistance in breast cancer.

Methods

Circ-MMP11, microRNA-153-3p (miR-153-3p), and Anillin (ANLN) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, number of colonies, apoptosis, migration, and invasion were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), colony formation, flow cytometry, and transwell assays, respectively. Exosomes were exerted and detected by differential centrifugation and a transmission electron microscope. The protein levels of CD63, CD9, and ANLN were assessed by western blot assay. The binding relationship between miR-153-3p and circ-MMP11 or ANLN was predicted by circinteractome or starbase, and then verified by a dual-luciferase reporter assay and RNA pull-down assay. The biological role of circ-MMP11 on breast cancer tumor growth and drug resistance was detected by the xenograft tumor model in vivo.

Results

Circ-MMP11 and ANLN were highly expressed, and miR-153-3p was decreased in LR breast cancer tissues and cells. Circ-MMP11 could be transported by exosomes. Furthermore, circ-MMP11 knockdown promoted lapatinib sensitivity by repressing cell viability, colony number, migration, invasion, and boosting apoptosis in LR breast cancer cells. Circ-MMP11 deficiency improved the drug sensitivity of breast cancer in vivo. Mechanically, circ-MMP11 could regulate ANLN expression through sponging miR-153-3p.

Conclusion

Circ-MMP11 could be transferred by exosomes in breast cancer cells. And circ-MMP11 functioned as a sponge of miR-153-3p to regulate ANLN expression, thereby promoting lapatinib resistance in breast cancer cells, providing therapeutic targets for the treatment of breast cancer.

Exosomal Circ-XIAP Promotes Docetaxel Resistance in Prostate Cancer by Regulating miR-1182/TPD52 Axis

Background

Exosomal circular RNAs (circRNAs) are involved in the pathogenesis of prostate cancer (PCa) and chemotherapy resistance. This research aimed to explore the function and molecular mechanism of circRNA X-linked inhibitor of apoptosis (circ-XIAP) in docetaxel (DTX) resistance of PCa.

Methods

The expression of circ-XIAP, microRNA-1182 (miR-1182), tumor protein D52 (TPD52) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Exosomes were detected with transmission electron microscopy (TEM). Cluster of differentiation 63 (CD63), cluster of differentiation 9 (CD9) and TPD52 protein levels were detected by Western blot (WB). FIfty percent inhibitory concentration (IC50) of DTX and cell viability were determined using Cell Counting Kit-8 (CCK-8) assay. Colony formation assay was applied to assess colony-forming ability. Cell cycle distribution and apoptosis were analyzed by flow cytometry. Transwell assay was used for measuring cell migration and invasion. Dual-reporter luciferase assay was performed to confirm the interaction between miR-1182 and circ-XIAP or TPD52. The role of circ-XIAP in vivo was confirmed via the mice xenograft model.

Results

Circ-XIAP and TPD52 were upregulated and miR-1182 was downregulated in DTX-resistant PCa tissue specimens and cell lines. Circ-XIAP was also overexpressed in exosomes from DTX-resistant cells and could be transmitted via exosomes. Circ-XIAP knockdown enhanced DTX sensitivity by suppressing DTX-resistant cell proliferation, migration and invasion and inducing cell cycle arrest and apoptosis. Circ-XIAP directly targeted miR-1182, and the effects of circ-XIAP knockdown were reversed by downregulating miR-1182 in DTX-resistant cells. TPD52 was the target of miR-1182, and its upregulation weakened the promotive effect of miR-1182 on DTX sensitivity. Importantly, circ-XIAP depletion inhibited tumor growth and increased DTX sensitivity in vivo.

Conclusion

Exosomal circ-XIAP promoted DTX resistance of PCa by regulating miR-1182/TPD52 axis, providing a promising therapeutic target for PCa chemotherapy.

Breast Cancer Microenvironment Cross Talk through Extracellular Vesicle RNAs

Exploration of extracellular communication has been at the forefront of research efforts in recent years. However, the mechanisms of cell-to-cell communication in complex tissues are poorly understood. What is clear is that cells do not exist in isolation, that they are constantly interacting and communicating with cells in the immediate vicinity and with cells at a distance. Intercellular communication by the release of small extracellular vesicles, called exosomes, loaded with RNAs is one mechanism by which cells communicate. In recent years, research has shown that exosomes, a class of extracellular vesicles, can play a major role in the pathogenesis of breast cancer. Specifically, exosomes have been demonstrated to play a role in promoting primary cancer development, invasion, metastasis, and chemotherapeutic resistance. This review summarizes what is known about the mechanisms of exosome-mediated transfer of RNAs among cells in the breast microenvironment and discusses outstanding questions and the potential for new therapeutic intervention targeted at these interactions.

Circular RNAs: new biomarkers of chemoresistance in cancer

Chemotherapeutics are validated conventional treatments for patients with advanced cancer. However, with continual application of chemotherapeutics, chemoresistance, which is often predictive of poor prognosis, has gradually become a concern in recent years. Circular RNAs (circRNAs), a class of endogenous noncoding RNAs (ncRNAs) with a closed-loop structure, have been reported to be notable targets and markers for the prognosis, diagnosis, and treatment of many diseases, particularly cancer. Although dozens of studies have shown that circRNAs play major roles in drug-resistance activity in tumors, the mechanisms by which circRNAs affect chemoresistance have yet to be explored. In this review, we describe the detailed mechanisms of circRNAs and chemotherapeutics in various cancers and summarize potential therapeutic targets for drug-resistant tumors.

Circular RNAs: Their Role in the Pathogenesis and Orchestration of Breast Cancer

As one of the most frequently occurring malignancies in women, breast cancer (BC) is still an enormous threat to women all over the world. The high mortality rates in BC patients are associated with BC recurrence, metastatic progression to distant organs, and therapeutic resistance. Circular RNAs (circRNAs), belonging to the non-coding RNAs (ncRNAs), are connected end to end to form covalently closed single-chain circular molecules. CircRNAs are widely found in different species and a variety of human cells, with the features of diversity, evolutionary conservation, stability, and specificity. CircRNAs are emerging important participators in multiple diseases, including cardiovascular disease, inflammation, and cancer. Recent studies have shown that circRNAs are involved in BC progress by regulating gene expression at the transcriptional or post-transcriptional level via binding to miRNAs then inhibiting their function, suggesting that circRNAs may be potential targets for early diagnosis, treatment, and prognosis of BC. Herein, in this article, we have reviewed and summarized the current studies about the biogenesis, features, and functions of circRNAs. More importantly, we emphatically elucidate the pivotal functions and mechanisms of circRNAs in BC growth, metastasis, diagnosis, and drug resistance. Deciphering the complex networks, especially the circRNA-miRNA target gene axis, will endow huge potentials in developing therapeutic strategies for combating BC.

Regulatory mechanisms, functions, and clinical significance of CircRNAs in triple-negative breast cancer

Circular RNAs (circRNAs) are a new class of endogenous regulatory RNAs characterized by covalently closed cyclic structure lacking poly-adenylated tails, and are capable of regulating gene expression at transcription or post-transcription levels. Recently, plentiful circRNAs have been discovered in breast cancer and some circRNAs expression profiles are specifically involved in the triple-negative breast cancer (TNBC). TNBC is a type of malignant tumor defined by the lack of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 expression. Considering its clinical characteristics of high invasion, metastasis, poor prognosis, and lack of effective response to conventional chemotherapies or targeted therapies, it could be a promosing option to discover specific circRNAs as new targets for TNBC treatment. Meanwhile, accumulating evidence has demonstrated that circRNAs are dysregulated in TNBC tissues and are correlated with clinicopathological features and prognosis of TNBC patients. Furthermore, looking for circRNAs with high specificity and sensitivity will provide a new opportunity for the early diagnosis, clinical treatment, and prognosis monitoring of TNBC. Herein, we reviewed the biogenesis, regulatory mechanisms, and biological functions of circRNAs in TNBC and summarized the relationship between circRNAs expression and the clinicopathology, diagnosis, and prognosis of patients with TNBC.