CircRNA_0044556 diminishes the sensitivity of triple‑negative breast cancer cells to adriamycin by sponging miR‑145 and regulating NRAS

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.

Circular RNAs as a novel molecular mechanism in diagnosis, prognosis, therapeutic target, and inhibiting chemoresistance in breast cancer

Breast cancer (BC) is the most common cancer among women, characterized by significant heterogeneity. Diagnosis of the disease in the early stages and appropriate treatment plays a crucial role for these patients. Despite the available treatments, many patients due to drug resistance do not receive proper treatments. Recently, circular RNAs (circRNAs), a type of non-coding RNAs (ncRNAs), have been discovered to be involved in the progression and resistance to drugs in BC. CircRNAs can promote or inhibit malignant cells by their function. Numerous circRNAs have been discovered to be involved in the proliferation, invasion, and migration of tumor cells, as well as the progression, pathogenesis, tumor metastasis, and drug resistance of BC. Circular RNAs can also serve as a biomarker for diagnosing, predicting prognosis, and targeting therapy. In this review, we present an outline of the variations in circRNAs expression in various BCs, the functional pathways, their impact on the condition, and their uses in clinical applications.

The role of circRNAs and miRNAs in drug resistance and targeted therapy responses in breast cancer

MicroRNAs (miRNAs) are small non-coding RNAs comprising 19-24 nucleotides that indirectly control gene expression. In contrast to other non-coding RNAs (ncRNAs), circular RNAs (circRNAs) are defined by their covalently closed loops, forming covalent bonds between the 3' and 5' ends. circRNAs regulate gene expression by interacting with miRNAs at transcriptional or post-transcriptional levels. Accordingly, circRNAs and miRNAs control many biological events related to cancer, including cell proliferation, metabolism, cell cycle, and apoptosis. Both circRNAs and miRNAs are involved in the pathogenesis of diseases, such as breast cancer. This review focuses on the latest discoveries on dysregulated circRNAs and miRNAs related to breast cancer, highlighting their potential as biomarkers for clinical diagnosis, prognosis, and chemotherapy response.

CircRNA_0044556 affects the sensitivity of triple-negative breast cancer cells to paclitaxel by regulating miR-665

CircRNAs have been implicated in the development of resistance in triple-negative breast cancer (TNBC). However, the association between circRNA_0044556 and paclitaxel (PTX) resistance in TNBC is still limited. Therefore, the purpose of this study was to investigate the effect of circRNA_0044556 on biological function and PTX resistance in TNBC cells. PTX-resistant TNBC cells (MDA-MB-231/PTX) were obtained by continuously exposing MDA-MB-231 cells to increasing paclitaxel levels. The expression levels of circRNA_0044556 and miR-665 were measured by qRT-PCR. The regulatory relationship between miR-665 and circRNA_0044556 was verified by biological information website analysis and double-luciferase reporter gene detection experiments. MTT assay, clone assay, flow cytometry and Western blot analysis were used to evaluate the influence of cell biological function. Elevated circRNA_0044556 was observed in TNBC, and paclitaxel increased the expression of circRNA_0044556 in TNBC cells. In TNBC, circRNA_0044556 acted as a ceRNA for miR-665. In addition, low expression of circRNA_0044556 combined with miR-665 inhibited the proliferation of TNBC cells and paclitaxel-resistant TNBC cells while inducing cell death. Our study demonstrated that the downregulation of circRNA_0044556 inhibits the malignant progression of TNBC cells and paclitaxel resistance via miR-665. Thus, circRNA_0044556 may be a potential therapeutic target for PTX-resistance TNBC.

Lau AT, Xu YM. The regulation of microRNAs on chemoresistance in triple-negative breast cancer: a recent update

Triple-negative breast cancer (TNBC) has negative expressions of ER, PR and HER2. Due to the insensitivity to both endocrine therapy and HER2-targeted therapy, the main treatment method for TNBC is cytotoxic chemotherapy. However, the curative effect of chemotherapy is limited because of the existence of acquired or intrinsic multidrug resistance. MicroRNAs (miRNAs) are frequently dysregulated in malignant tumors and involved in tumor occurrence and progression. Interestingly, growing studies show that miRNAs are involved in chemoresistance in TNBC. Thus, targeting dysregulated miRNAs could be a plausible way for better treatment of TNBC. Here, we present the updated knowledge of miRNAs associated with chemoresistance in TNBC, which may be helpful for the early diagnosis, prognosis and treatment of this life-threatening disease.

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.

Circular RNAs in the chemoresistance of triple-negative breast cancer: A systematic review

This study aims to assess studies on circular RNAs (circRNAs) in the chemoresistance of triple-negative breast cancer (TNBC) and provide relevant references for the development of new TNBC chemotherapy sensitivity biomarkers and therapeutic targets. The PubMed, Embase, Web of Knowledge, Cochrane Library, and four Chinese databases were searched up to January 27, 2023, and studies related to TNBC chemoresistance were included. The basic characteristics of the studies and the mechanisms of circRNAs in regulating TNBC chemoresistance were analyzed. A total of 28 studies published between 2018 and 2023 were included, and the chemotherapeutics included adriamycin, paclitaxel, docetaxel, 5-fluorouracil, lapatinib, and so forth. A total of 30 circRNAs were identified, 86.67% (n = 26) of these circRNAs were reported to act as microRNA (miRNA) sponges to regulate chemotherapy sensitivity, while only two circRNAs (circRNA-MTO1 and circRNA-CREIT) interacted with proteins. A total of 14, 12, and 2 circRNAs were reported to be associated with chemoresistance to adriamycin, taxanes, and 5-fluorouracil, respectively. Six circRNAs were found to act as miRNA sponges that promote chemotherapy resistance by regulating the PI3K/Akt signalling pathway. CircRNAs participate in the regulation of TNBC chemoresistance and can be used as biomarkers and therapeutic targets for improving chemotherapy sensitivity. However, further studies are needed to confirm the role of circRNAs in TNBC chemoresistance.

Unraveling the significance of exosomal circRNAs in cancer therapeutic resistance

Exosomes are nanoscale extracellular vesicles secreted by a variety of cells, affecting the physiological and pathological homeostasis. They carry various cargoes including proteins, lipids, DNA, and RNA and have emerged as critical mediators of intercellular communication. During cell-cell communication, they can internalize either by autologous or heterologous recipient cells, which activate different signaling pathways, facilitating malignant progression of cancer. Among different types of cargoes in exosomes, the endogenous non-coding RNAs, such as circular RNAs (or circRNAs), have gained tremendous attention for their high stability and concentration, playing promising functional roles in cancer chemotherapeutic response by regulating the targeted gene expression. In this review, we primarily described the emerging evidence demonstrating the important roles of circular RNAs derived from exosomes in the regulation of cancer-associated signaling pathways that were involved in cancer research and therapeutic interventions. Additionally, the relevant profiles of exosomal circRNAs and their biological implications have been discussed, which is under investigation for their potential effect on the control of cancer therapeutic resistance.

Current evidence on circRNAs as potential theranostic markers for detecting chemoresistance in breast cancer: a systematic review and meta‑analysis

This study assessed the value of circRNAs (circular RNAs) as prognostic markers in BC (breast cancer). We searched pertinent studies on the PubMed, Embase, and Web of Science online databases published according to PRISMA guidelines. A random-effects model for meta-analysis was used to assess the combined effect size of the HRs (hazard ratios) of the included studies. The heterogeneity test used Cochran's Q-test and I² statistics. Thirty of the 520 trials retrieved were included in the systematic review. A total of 11 chemotherapeutic agents were used in the included studies. A total of 30 studies on 30 circRNAs were included in the systematic review. Of the 30 relevant circRNAs, 28 were upregulated and two were downregulated in breast cancer versus normal samples, and both were associated with increased drug resistance. Nine of 30 studies were used for the meta-analysis. The results of the meta-analysis showed that the groups with circRNA upregulation and circRNA downregulation showed the same prognostic risk (HR = 1.37, 95% Cl: 0.80-2.36, I² = 63.7%). The results of subgroup analysis showed that both upregulated circRNAs (HR = 2.24, 95% Cl: 1.34-3.75, I² = 0%) and downregulated circRNAs (HR = 0.61, 95% Cl: 0.45-0.83, I² = 0%) were associated with poor BC prognosis. Collectively, the results of all relevant articles collected indicated that circRNAs showed good potential as possible clinical biomarkers of chemoresistance in BC patients.

Non-coding RNA in cancer drug resistance: Underlying mechanisms and clinical applications

Cancer is one of the most frequently diagnosed malignant diseases worldwide, posing a serious, long-term threat to patients’ health and life. Systemic chemotherapy remains the first-line therapeutic approach for recurrent or metastatic cancer patients after surgery, with the potential to effectively extend patient survival. However, the development of drug resistance seriously limits the clinical efficiency of chemotherapy and ultimately results in treatment failure and patient death. A large number of studies have shown that non-coding RNAs (ncRNAs), particularly microRNAs, long non-coding RNAs, and circular RNAs, are widely involved in the regulation of cancer drug resistance. Their dysregulation contributes to the development of cancer drug resistance by modulating the expression of specific target genes involved in cellular apoptosis, autophagy, drug efflux, epithelial-to-mesenchymal transition (EMT), and cancer stem cells (CSCs). Moreover, some ncRNAs also possess great potential as efficient, specific biomarkers in diagnosis and prognosis as well as therapeutic targets in cancer patients. In this review, we summarize the recent findings on the emerging role and underlying mechanisms of ncRNAs involved in cancer drug resistance and focus on their clinical applications as biomarkers and therapeutic targets in cancer treatment. This information will be of great benefit to early diagnosis and prognostic assessments of cancer as well as the development of ncRNA-based therapeutic strategies for cancer patients.

Circular RNAs as novel biomarkers in triple-negative breast cancer: a systematic review

More effective prognostic and diagnostic tools are urgently required for early detecting and treating triple-negative breast cancer, which is the most acute type of breast cancer because of its lower survival rate, aggressiveness, and non-response to various common treatments. So, it remains the most harmful malignancy for women worldwide. Recently, circular RNAs, as a group of non-coding RNAs, with covalently closed loop and high stability have been discovered, which can modulate gene expression through competing with endogenous microRNA sponges. This finding provided further insight into novel approaches for controlling genes affected in many disorders and malignancies. This review concentrates on the dysregulated expression of circRNAs like their diagnostic and prognostic values in TNBC. This review aims to focus on the abnormal expression of circRNAs and their diagnostic and prognostic values in TNBC. We used PubMed, Embase, and Web of Science databases and ClinicalTrials.gov to systematically search for all relevant clinical studies. This review is based on articles published in databases up to April 2022 with the following keywords: "Circular RNA", "CircRNA", "Triple-Negative Breast Cancer" and "TNBC". We conducted a review of published CircRNA profiled-research articles to identify candidate CircRNA biomarkers for TNBC. The review is registered on JBI at https://jbi.global/systematic-review-register . Accumulating evidence has shown that several circRNAs are downregulated and some are upregulated in TNBC. The results of these studies confirm that circRNAs might be potential biomarkers with the diagnostic, prognostic, and therapeutic target value for TNBC. We also consider the connection between circRNAs and TNBC cell proliferation, apoptosis, metastasis, and chemotherapy resistance and sensitivity.

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.