Circular RNA circ-PVT1 contributes to paclitaxel resistance of gastric cancer cells through the regulation of ZEB1 expression by sponging miR-124-3p. Biosci Rep. 2019;39. [PMID: 31793989 PMCID: PMC6928529 DOI: 10.1042/bsr20193045]

Exosomal circPVT1 promotes angiogenesis in laryngeal cancer by activating the Rap1b-VEGFR2 signaling pathway

Laryngeal cancer (LC) is the second most common head and neck cancer and has a decreasing 5-year survival rate worldwide. Circular RNAs (circRNAs) regulate cancer development in diverse ways based on their distinct biogenesis mechanisms and expansive regulatory roles. However, currently, there is little research on how exosomal circRNAs are involved in the development of LC. Here, we demonstrated that circPVT1, a circRNA derived from the well-studied long noncoding RNA PVT1, is correlated with disease progression in LC and promotes angiogenesis both in vivo and in vitro. Mechanistically, circPVT1 is loaded into LC cell-secreted exosomes and taken up by vascular epithelium cells. By sponging miR-30c-5p, exosomal circPVT1 promotes Rap1b expression, which dramatically enhances vascular endothelial growth factor receptor 2 and the phosphatidylinositol 3-kinase (PI3K)/AKT pathway activation, ultimately resulting in the induction of angiogenesis. Furthermore, our xenograft models demonstrated that the combination of short hairpin RNA-circPVT1 and cetuximab showed high efficacy in inhibiting tumor growth and angiogenesis. Collectively, these findings uncover a novel mechanism of exosomal circRNA-mediated angiogenesis modulation and provide a preclinical rationale for testing this analogous combination in patients with LC.

Novel role of circRNAs in the drug resistance of gastric cancer: regulatory mechanisms and future for cancer therapy

Cancer, including gastric cancer, has become a serious disease that jeopardizes public life. Currently, the main treatment methods are surgery, radiation therapy, and chemotherapy. One of the primary causes of death for patients with gastric cancer is drug resistance. Several mechanisms of anticancer drugs resistance have been reported, including changes in drugs transport and metabolism, mutations in drug targets, changes in DNA repair systems, inhibition of cell apoptosis and autophagy, gastric cancer stem cells, invasion and migration. It is becoming more widely known that non-coding RNAs, like circRNAs, play a critical role in the resistance of drugs used to treat gastric cancer. CircRNAs have a unique structure and function that is related to gastric cancer resistance, cell proliferation, apoptosis, autophagy, DNA repair systems, migration, and invasion. A clear understanding of the molecular mechanism of circRNAs mediated the resistance of gastric cancer drugs will open a new window for the treatment and management of gastric cancer. Therefore, in this review, we will summarize the current mechanism of drug resistance, and finally discuss the molecular mechanism of circRNAs in regulating the development of drug resistance in gastric cancer.

Overcoming cancer drug-resistance calls for novel strategies targeting abnormal alternative splicing

Abnormal gene alternative splicing (AS) events are strongly associated with cancer progression. Here, we summarize AS events that contribute to the development of drug resistance and classify them into three categories: alternative cis-splicing (ACS), alternative trans-splicing (ATS), and alternative back-splicing (ABS). The regulatory mechanisms underlying AS processes through cis-acting regulatory elements and trans-acting factors are comprehensively described, and the distinct functions of spliced variants, including linear spliced variants derived from ACS, chimeric spliced variants arising from ATS, and circRNAs generated through ABS, are discussed. The identification of dysregulated spliced variants, which contribute to drug resistance and hinder effective cancer treatment, suggests that abnormal AS processes may together serve as a precise regulatory mechanism enabling drug-resistant cancer cell survival or, alternatively, represent an evolutionary pathway for cancer cells to adapt to changes in the external environment. Moreover, this review summarizes recent advancements in treatment approaches targeting AS-associated drug resistance, focusing on cis-acting regulatory elements, trans-acting factors, and specific spliced variants. Collectively, gaining an in-depth understanding of the mechanisms underlying aberrant alternative splicing events and developing strategies to target this process hold great promise for overcoming cancer drug resistance.

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.

RP11-789C1.1 inhibits gastric cancer cell proliferation and accelerates apoptosis via the ATR/CHK1 signaling pathway

BACKGROUND

Long non-coding RNAs (lncRNAs) plays an important role in the progression of gastric cancer (GC). Their involvement ranges from genetic regulation to cancer progression. However, the mechanistic roles of RP11-789C1.1 in GC are not fully understood.

METHODS

We identified the expression of lncRNA RP11-789C1.1 in GC tissues and cell lines by real-time fluorescent quantitative polymerase chain reaction. A series of functional experiments revealed the effect of RP11-789C1.1 on the proliferation of GC cells. In vivo experiments verified the effect of RP11-789C1.1 on the biological behavior of a GC cell line. RNA pull-down unveiled RP11-789C1.1 interacting proteins. Western blot analysis indicated the downstream pathway changes of RP11-789C1.1, and an oxaliplatin dosing experiment disclosed the influence of RP11-789C1.1 on the drug sensitivity of oxaliplatin.

RESULTS

Our results demonstrated that RP11-789C1.1 inhibited the proliferation of GC cells and promoted the apoptosis of GC cells. Mechanistically, RP11-789C1.1 inhibited checkpoint kinase 1 (CHK1) phosphorylation by binding ataxia-telangiectasia mutated and Rad3 related (ATR), a serine/threonine-specific protein kinase, promoted GC apoptosis, and mediated oxaliplatin sensitivity.

CONCLUSION

In general, we discovered a tumor suppressor molecule RP11-789C1.1 and confirmed its mechanism of action, providing a theoretical basis for targeted GC therapy.

Knockdown of circ_0076305 decreases the paclitaxel resistance of non-small cell lung cancer cells by regulating TMPRSS4 via miR-936

Background

Paclitaxel (PTX) is a commonly used as a chemotherapeutic drug for non-small cell lung cancer (NSCLC). Exploring the underlying mechanism of PTX resistance is of great significance for NSCLC treatment.

Methods

The expression levels of RNA and protein were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot assays. The targeted relationship was confirmed by dual-luciferase reporter assay and RNA-pull down assay. The PTX resistance and cell proliferation were assessed by cell counting kit-8 (CCK-8) assay and 5-Ethynyl-2'-deoxyuridine (EDU) assay, respectively. Cell migration and invasion were analyzed by transwell assays. Cell apoptosis was analyzed by flow cytometry, and cell glycolysis was analyzed using the commercial kits. The role of circular RNA_0076305 (circ_0076305) in regulating the PTX sensitivity in vivo was explored in xenograft tumor model.

Results

Circ_0076305 was up-regulated in PTX-resistant NSCLC tissues and cells. Mechanically, circ_0076305 bound to microRNA-936 (miR-936), and miR-936 targeted transmembrane serine protease 4 (TMPRSS4). Circ_0076305 could up-regulate TMPRSS4 expression by sponging miR-936 in NSCLC cells. miR-936 knockdown or TMPRSS4 overexpression reversed the anti-tumor effects of circ_0076305 knockdown in NSCLC cells with PTX treatment. Circ_0076305 silencing increased the PTX sensitivity of xenograft tumors in vivo.

Conclusion

Circ_0076305 silencing promoted PTX sensitivity by targeting miR-936/TMPRSS4 axis in NSCLC cells.

New insights into the potential of exosomal circular RNAs in mediating cancer chemotherapy resistance and their clinical applications

Chemotherapy resistance typically leads to tumour recurrence and is a major obstacle to cancer treatment. Increasing numbers of circular RNAs (circRNAs) have been confirmed to be abnormally expressed in various tumours, where they participate in the malignant progression of tumours, and play important roles in regulating the sensitivity of tumours to chemotherapy drugs. As exosomes mediate intercellular communication, they are rich in circRNAs and exhibit a specific RNA cargo sorting mechanism. By carrying and delivering circRNAs, exosomes can promote the efflux of chemotherapeutic drugs and reduce intracellular drug concentrations in recipient cells, thus affecting the cell cycle, apoptosis, autophagy, angiogenesis, invasion and migration. The mechanisms that affect the phenotype of tumour stem cells, epithelial-mesenchymal transformation and DNA damage repair also mediate chemotherapy resistance in many tumours. Exosomal circRNAs are diagnostic biomarkers and potential therapeutic targets for reversing chemotherapy resistance in tumours. Currently, the rise of new fields, such as machine learning and artificial intelligence, and new technologies such as biosensors, multimolecular diagnostic systems and platforms based on circRNAs, as well as the application of exosome-based vaccines, has provided novel ideas for precision cancer treatment. In this review, the recent progress in understanding how exosomal circRNAs mediate tumour chemotherapy resistance is reviewed, and the potential of exosomal circRNAs in tumour diagnosis, treatment and immune regulation is discussed, providing new ideas for inhibiting tumour chemotherapy resistance.

circPDK1 competitively binds miR-4731-5p to mediate GIGYF1 expression and increase paclitaxel sensitivity in non-small cell lung cancer

OBJECTIVE

To investigate the action of circPDK1 in paclitaxel (PTX) resistance in non-small cell lung cancer (NSCLC).

METHODS

circPDK1, miR-4731-5p, and GIGYF1 levels were determined by RT-qPCR and Western blot. Cell proliferation was detected by CCK-8 and colony formation assay, apoptosis by flow cytometry, invasion by Transwell assay. The targeting relationship between miR-4731-5p and circPDK1 or GIGYF1 was confirmed by dual luciferase reporter gene and RIP assay. A xenograft tumor model was established to determine the role of circPDK1 in PTX resistance.

RESULTS

circPDK1 was overexpressed in PTX-resistant NSCLC, and depleting circPDK1 hampered proliferation and invasion of PTX-resistant cells, activated apoptosis, and improved PTX sensitivity. circPDK1 bound to miR-4731-5p, and increasing miR-4731-5p expression salvaged the effect of circPDK1 depletion on PTX resistance. miR-4731-5p directly targeted GIGYF1, and upregulating GIGYF1 offset the promoting effect of circPDK1 knockdown on PTX sensitivity. NSCLC tumor growth was inhibited and PTX sensitivity improved when circPDK1 was suppressed.

CONCLUSION

Depleting circPDK1 promotes PTX sensitivity of NSCLC cells via miR-4731-5p/GIGYF1 axis, thereby inhibiting NSCLC pregnancy.

miRNA-383-5p Regulated Migration and Invasion of Tumor Cells by Inhibiting NCKAP1 Expression in Gastric Cancer

Gastric cancer (GC) is the second deadliest disease in Asia, so it is crucial to find its promising therapeutic targets. The expression profile data of miR383-5p in the Cancer Genome Atlas (TCGA) were analyzed. The expression levels of miR383-5p in the collected clinical tissue samples and peripheral blood samples were examined by qPCR, and the relationship between its expression and the clinical data of patients was evaluated. MiR383-5p was overexpressed in the AGS cells, and cell biology assays, such as Transwell, were performed to detect the cell proliferation, migration, invasion and other cell biology abilities of miR383-5p. Target prediction and dual luciferase reporter gene assay were performed to find and validate the target genes of miR383-5p. The expression and activity of MMP and related proteins after overexpression of miR383-5p and NCKAP1 were detected by WB and gelatin zymography assay. The expression of miR383-5p was down-regulated in GC tissues, and its low expression was associated with lymph node metastasis. Restoration of miR383-5p expression in GC cells can inhibit the invasion and migration abilities of GC cells. MiR383-5p negatively regulated NCKAP1 through direct interaction with the 3'UTR sequence of NCKAP1. The overexpression of NCKAP1 can improve the migration and invasion abilities of GC cells, whereas overexpression of miR383-5p can inhibit growth of the aforementioned abilities of GC cells induced by NCKAP1 overexpression. The overexpression of NCKAP1 can increase the expression level and activity of MMP2, while the overexpression of miR383-5p can inhibit the increase of MMP2 expression level and activity in GC cells induced by NCKAP1 overexpression. NCKAP1 is a target gene of miR383-5p, and miR383-5p could be a valuable therapeutic target for stomach adenocarcinoma.

The potential role and mechanism of circRNAs in Ferroptosis: A comprehensive review

Cell death encompasses various mechanisms, including necrosis and apoptosis. Ferroptosis, a unique form of regulated cell death, emerged as a non-apoptotic process reliant on iron and reactive oxygen species (ROS). Distinguishing itself from other forms of cell death, ferroptosis exhibits distinct morphological, biochemical, and genetic features. Circular RNAs (circRNAs), a novel class of RNA molecules, play crucial regulatory roles in ferroptosis-mediated pathways and cellular processes. With their circular structure and stability, circRNAs function as microRNA sponges and participate in protein regulation, offering diverse mechanisms for cellular control. Accumulating evidence indicates that circRNAs are key players in diseases associated with ferroptosis, presenting opportunities for diagnostic and therapeutic applications. This study explores the regulatory roles of circRNAs in ferroptosis and their potential in diseases such as cancer, neurological disorders, and cardiovascular diseases. By investigating the relationship between circRNAs and ferroptosis, this research provides new insights into the diagnosis, treatment, and prognosis of ferroptosis-related diseases. Furthermore, the therapeutic implications of targeting circRNAs in cancer treatment and the modulation of ferroptosis pathways demonstrate the potential of circRNAs as diagnostic markers and therapeutic targets. Overall, understanding the involvement of circRNAs in regulating ferroptosis opens up new avenues for advancements in disease management.

Emerging roles of circular RNAs in tumorigenesis, progression, and treatment of gastric cancer

With an estimated one million new cases reported annually, gastric cancer (GC) ranks as the fifth most diagnosed malignancy worldwide. The early detection of GC remains a major challenge, and the prognosis worsens either when patients develop resistance to chemotherapy or radiotherapy or when the cancer metastasizes. The precise pathogenesis underlying GC is not well understood, which further complicates its treatment. Circular RNAs (circRNAs), a recently discovered class of noncoding RNAs that originate from parental genes through "back-splicing", have been shown to play a key role in various biological processes in both eukaryotes and prokaryotes. CircRNAs have been linked to cardiovascular diseases, diabetes, hypertension, Alzheimer's disease, and the occurrence and progression of tumors. Prior studies have established that circRNAs play a crucial role in GC, impacting tumorigenesis, diagnosis, progression, and therapy resistance. This review aims to summarize how circRNAs contribute to GC tumorigenesis and progression, examine their roles in the development of drug resistance, discuss their potential as biotechnological drugs, and summarize their response to therapeutic drugs and microorganism in GC.

Combination of multiple omics techniques for a personalized therapy or treatment selection

Despite targeted therapies and immunotherapies have revolutionized the treatment of cancer patients, only a limited number of patients have long-term responses. Moreover, due to differences within cancer patients in the tumor mutational burden, composition of the tumor microenvironment as well as of the peripheral immune system and microbiome, and in the development of immune escape mechanisms, there is no "one fit all" therapy. Thus, the treatment of patients must be personalized based on the specific molecular, immunologic and/or metabolic landscape of their tumor. In order to identify for each patient the best possible therapy, different approaches should be employed and combined. These include (i) the use of predictive biomarkers identified on large cohorts of patients with the same tumor type and (ii) the evaluation of the individual tumor with "omics"-based analyses as well as its ex vivo characterization for susceptibility to different therapies.

Emerging roles of noncoding RNAs in human cancers

Studies have found that RNA encoding proteins only account for a small part of the total number, most RNA is non-coding RNA, and non-coding RNA may affect the occurrence and development of human cancers by affecting gene expression, therefore play an important role in human pathology. At present, ncRNAs studied include miRNA, circRNA, lncRNA, piRNA, and snoRNA, etc. After decades of research, the basic role of these ncRNAs in many cancers has been clear. As far as we know, the role of miRNAs in cancer is one of the hottest research directions, however, it is also found that the imbalance of ncRNAs will affect the occurrence of gastric cancer, breast cancer, lung cancer, meanwhile, it may also affect the prognosis of these cancers. Therefore, the study of ncRNAs in cancers may help to find new cancer diagnostic and treatment methods. Here, we reviewed the biosynthesis and characteristics of miRNA, cricRNA, and lncRNA etc., their roles in human cancers, as well as the mechanism through which these ncRNAs affect human cancers.

CircPVT1 promotes ER-positive breast tumorigenesis and drug resistance by targeting ESR1 and MAVS

The molecular mechanisms underlying estrogen receptor (ER)-positive breast carcinogenesis and endocrine therapy resistance remain incompletely understood. Here, we report that circPVT1, a circular RNA generated from the lncRNA PVT1, is highly expressed in ERα-positive breast cancer cell lines and tumor samples and is functionally important in promoting ERα-positive breast tumorigenesis and endocrine therapy resistance. CircPVT1 acts as a competing endogenous RNA (ceRNA) to sponge miR-181a-2-3p, promoting the expression of ESR1 and downstream ERα-target genes and breast cancer cell growth. Furthermore, circPVT1 directly interacts with MAVS protein to disrupt the RIGI-MAVS complex formation, inhibiting type I interferon (IFN) signaling pathway and anti-tumor immunity. Anti-sense oligonucleotide (ASO)-targeting circPVT1 inhibits ERα-positive breast cancer cell and tumor growth, re-sensitizing tamoxifen-resistant ERα-positive breast cancer cells to tamoxifen treatment. Taken together, our data demonstrated that circPVT1 can work through both ceRNA and protein scaffolding mechanisms to promote cancer. Thus, circPVT1 may serve as a diagnostic biomarker and therapeutic target for ERα-positive breast cancer in the clinic.

The critical role of circular RNAs in drug resistance in gastrointestinal cancers

Nowadays, drug resistance (DR) in gastrointestinal (GI) cancers, as the main reason for cancer-related mortality worldwide, has become a serious problem in the management of patients. Several mechanisms have been proposed for resistance to anticancer drugs, including altered transport and metabolism of drugs, mutation of drug targets, altered DNA repair system, inhibited apoptosis and autophagy, cancer stem cells, tumor heterogeneity, and epithelial-mesenchymal transition. Compelling evidence has revealed that genetic and epigenetic factors are strongly linked to DR. Non-coding RNA (ncRNA) interferences are the most crucial epigenetic alterations explored so far, and among these ncRNAs, circular RNAs (circRNAs) are the most emerging members known to have unique properties. Due to the absence of 5' and 3' ends in these novel RNAs, the two ends are covalently bonded together and are generated from pre-mRNA in a process known as back-splicing, which makes them more stable than other RNAs. As far as the unique structure and function of circRNAs is concerned, they are implicated in proliferation, migration, invasion, angiogenesis, metastasis, and DR. A clear understanding of the molecular mechanisms responsible for circRNAs-mediated DR in the GI cancers will open a new window to the management of GI cancers. Hence, in the present review, we will describe briefly the biogenesis, multiple features, and different biological functions of circRNAs. Then, we will summarize current mechanisms of DR, and finally, discuss molecular mechanisms through which circRNAs regulate DR development in esophageal cancer, pancreatic cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma.

PCGEM1 promotes cell proliferation and migration in endometriosis by targeting miR-124-3p-mediated ANTXR2 expression

BACKGROUND

Endometriosis, a common gynaecological disease in women, affects 10% of women of childbearing age. Among infertile women, this proportion is as high as 30-50%. Despite the high prevalence of endometriosis, the pathogenesis of endometriosis is still unclear.

METHODS

In the present study, bioinformatics analysis and molecular and animal experiments were employed to explore the functions of PCGEM1 in the pathogenesis of endometriosis. We established an endometriosis rat model and isolated endometrial stromal cells (ESCs) and primary normal ESCs (NESCs). Bioinformatics analysis was adopted to study the roles of PCGEM1 in promoting the pathogenesis of endometriosis. Luciferase reporter assays and RNA pull-down assays were carried out to study the mechanism by which PCGEM1 regulates ANTXR2.

RESULTS

Our results indicated that PCGEM1 promoted the motility and proliferation of ectopic endometrial cells, and the underlying mechanism was due to the direct binding of PCGEM1 to miR-124-3p to modulate ANTXR2 expression.

CONCLUSION

PCGEM1 can influence endometrial stromal cell proliferation and motility and may be a novel therapeutic target for endometriosis.

Silencing of circ_002136 sensitizes gastric cancer to paclitaxel by targeting the miR-16-5p/HMGA1 axis

The dysregulated expression of circRNA in gastric cancer (GC) induces paclitaxel (Tax) resistance of cancer cells, which in turn affects disease progression and prognosis. Here, we sought to investigate the role and mechanism of circ_002136 in Tax-resistant GC. In this study, we found the enriched circ_002136 level and the declined miR-16-5p level in Tax-resistant GC tissues and cells. Biologically, knockdown of circ_002136 elevated the Tax sensitivity of Tax-resistant GC cells, inhibited the cell motility properties, and simultaneously drove the apoptosis. Mechanically, circ_002136 promoted the HMGA1-mediated cellular Tax resistance and cell invasion by sponging miR-16-5p. Furthermore, circ_002136 silencing impeded the growth of Tax-resistant GC tumors in vivo. Overall, our study revealed a novel signaling pathway that could be used for future clinical applications, namely the circ_002136/miR-16-5p/HMGA1 axis to regulate the Tax resistance of GC cells.

CircRNA: A new class of targets for gastric cancer drug resistance therapy

Gastric cancer (GC) is one of the most common malignancies worldwide. Patients with advanced GC need palliative care to ensure survival. This includes the use of chemotherapy agents, such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, and pemetrexed, as well as targeted agents. However, the emergence of drug resistance evidence in poor patient outcomes and poor prognosis is a motivation to determine the specific mechanism of drug resistance. Interestingly, circular RNAs (circRNAs) play an important part in the carcinogenesis and progression of GC and are involved in GC drug resistance. This review systematically summarizes the functions and mechanisms of circRNAs underlying GC drug resistance, especially chemoresistance. It also emphasizes that circRNAs can serve as promising targets for improving drug resistance and therapeutic efficacy.

The strategy and clinical relevance of in vitro models of MAP resistance in osteosarcoma: a systematic review

Over the last 40 years osteosarcoma (OS) survival has stagnated with patients commonly resistant to neoadjuvant MAP chemotherapy involving high dose methotrexate, adriamycin (doxorubicin) and platinum (cisplatin). Due to the rarity of OS, the generation of relevant cell models as tools for drug discovery is paramount to tackling this issue. Four literature databases were systematically searched using pre-determined search terms to identify MAP resistant OS cell lines and patients. Drug exposure strategies used to develop cell models of resistance and the impact of these on the differential expression of resistance associated genes, proteins and non-coding RNAs are reported. A comparison to clinical studies in relation to chemotherapy response, relapse and metastasis was then made. The search retrieved 1891 papers of which 52 were relevant. Commonly, cell lines were derived from Caucasian patients with epithelial or fibroblastic subtypes. The strategy for model development varied with most opting for continuous over pulsed chemotherapy exposure. A diverse resistance level was observed between models (2.2-338 fold) with 63% of models exceeding clinically reported resistance levels which may affect the expression of chemoresistance factors. In vitro p-glycoprotein overexpression is a key resistance mechanism; however, from the available literature to date this does not translate to innate resistance in patients. The selection of models with a lower fold resistance may better reflect the clinical situation. A comparison of standardised strategies in models and variants should be performed to determine their impact on resistance markers. Clinical studies are required to determine the impact of resistance markers identified in vitro in poor responders to MAP treatment, specifically with respect to innate and acquired resistance. A shift from seeking disputed and undruggable mechanisms to clinically relevant resistance mechanisms may identify key resistance markers that can be targeted for patient benefit after a 40-year wait.

Emerging roles of circular RNAs in gastric cancer metastasis and drug resistance

Gastric cancer (GC) is an aggressive malignancy with a high mortality rate and poor prognosis, primarily caused by metastatic lesions. Improved understanding of GC metastasis at the molecular level yields meaningful insights into potential biomarkers and therapeutic targets. Covalently closed circular RNAs (circRNAs) have emerged as crucial regulators in diverse human cancers including GC. Furthermore, accumulating evidence has demonstrated that circRNAs exhibit the dysregulated patterns in GC and have emerged as crucial regulators in GC invasion and metastasis. However, systematic knowledge regarding the involvement of circRNAs in metastatic GC remains obscure. In this review, we outline the functional circRNAs related to GC metastasis and drug resistance and discuss their underlying mechanisms, providing a comprehensive delineation of circRNA functions on metastatic GC and shedding new light on future therapeutic interventions for GC metastases.

Epigenetic regulation in myocardial infarction: Non-coding RNAs and exosomal non-coding RNAs

Myocardial infarction (MI) is one of the leading causes of deaths globally. The early diagnosis of MI lowers the rate of subsequent complications and maximizes the benefits of cardiovascular interventions. Many efforts have been made to explore new therapeutic targets for MI, and the therapeutic potential of non-coding RNAs (ncRNAs) is one good example. NcRNAs are a group of RNAs with many different subgroups, but they are not translated into proteins. MicroRNAs (miRNAs) are the most studied type of ncRNAs, and have been found to regulate several pathological processes in MI, including cardiomyocyte inflammation, apoptosis, angiogenesis, and fibrosis. These processes can also be modulated by circular RNAs and long ncRNAs via different mechanisms. However, the regulatory role of ncRNAs and their underlying mechanisms in MI are underexplored. Exosomes play a crucial role in communication between cells, and can affect both homeostasis and disease conditions. Exosomal ncRNAs have been shown to affect many biological functions. Tissue-specific changes in exosomal ncRNAs contribute to aging, tissue dysfunction, and human diseases. Here we provide a comprehensive review of recent findings on epigenetic changes in cardiovascular diseases as well as the role of ncRNAs and exosomal ncRNAs in MI, focusing on their function, diagnostic and prognostic significance.

Regulation of the Key Epithelial Cancer Suppressor miR-124 Function by Competing Endogenous RNAs

A decrease in the miR-124 expression was observed in various epithelial cancers. Like a classical suppressor, miR-124 can inhibit the translation of multiple oncogenic proteins. Epigenetic mechanisms play a significant role in the regulation of miR-124 expression and involve hypermethylation of the MIR-124-1/-2/-3 genes and the effects of long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) according to the model of competing endogenous RNAs (ceRNAs). More than 40 interactomes (lncRNA/miR-124/mRNA) based on competition between lncRNAs and mRNAs for miR-124 binding have been identified in various epithelial cancers. LncRNAs MALAT1, NEAT1, HOXA11-AS, and XIST are the most represented in these axes. Fourteen axes (e.g., SND1-IT1/miR-124/COL4A1) are involved in EMT and/or metastasis. Moreover, eight axes (e.g., OIP5-AS1/miR-124-5p/IDH2) are involved in key pathways, such as Wnt/b-catenin, E2F1, TGF-β, SMAD, ERK/MAPK, HIF-1α, Notch, PI3K/Akt signaling, and cancer cell stemness. Additionally, 15 axes impaired patient survival and three axes reduced chemo- or radiosensitivity. To date, 14 cases of miR-124 regulation by circRNAs have been identified. Half of them involve circHIPK3, which belongs to the exonic ecircRNAs and stimulates cell proliferation, EMT, autophagy, angiogenesis, and multidrug resistance. Thus, miR-124 and its interacting partners may be considered promising targets for cancer therapy.

CircRNAs in Tumor Radioresistance

Circular RNAs (circRNAs) are endogenous, non-coding RNAs, which are derived from host genes that are present in several species and can be involved in the progression of various diseases. circRNAs’ leading role is to act as RNA sponges. In recent years, the other roles of circRNAs have been discovered, such as regulating transcription and translation, regulating host genes, and even being translated into proteins. As some tumor cells are no longer radiosensitive, tumor radioresistance has since become a challenge in treating tumors. In recent years, circRNAs are differentially expressed in tumor cells and can be used as biological markers of tumors. In addition, circRNAs can regulate the radiosensitivity of tumors. Here, we list the mechanisms of circRNAs in glioma, nasopharyngeal carcinoma, and non-small cell lung cancer; further, these studies also provide new ideas for the purposes of eliminating radioresistance in tumors.

CXCL12/CXCR7/β-arrestin1 biased signal promotes epithelial-to-mesenchymal transition of colorectal cancer by repressing miRNAs through YAP1 nuclear translocation

BACKGROUND

Chemokine CXC motif receptor 7 (CXCR7) is an atypical G protein-coupled receptor (GPCR) that signals in a biased fashion. CXCL12/CXCR7 biased signal has been reported to play crucial roles in multiple stages of colorectal cancer (CRC). However, the mechanism of CXCL12/CXCR7 biased signal in promoting CRC progression and metastasis remains obscure.

RESULTS

We demonstrate that CXCR7 activation promotes EMT and upregulates the expression of Vimentin and doublecortin-like kinase 1 (DCLK1) in CRC cells with concurrent repression of miR-124-3p and miR-188-5p through YAP1 nuclear translocation. Cell transfection and luciferase assay prove that these miRNAs regulate EMT by targeting Vimentin and DCLK1. More importantly, CXCL12/CXCR7/β-arrestin1-mediated biased signal induces YAP1 nuclear translocation, which functions as a transcriptional repressor by interacting with Yin Yang 1 (YY1) and recruiting YY1 to the promoters of miR-124-3p and miR-188-5p. Pharmacological inhibitor of YAP1 suppresses EMT and tumor metastasis upon CXCR7 activation in vivo in tumor xenografts of nude mice and inflammatory colonic adenocarcinoma models. Clinically, the expression of CXCR7 is positively correlated with nuclear YAP1 levels and EMT markers.

CONCLUSIONS

Our studies reveal a novel mechanism and clinical significance of CXCL12/CXCR7 biased signal in promoting EMT and invasion in CRC progression. These findings highlight the potential of targeting YAP1 nuclear translocation in hampering CXCL12/CXCR7 biased signal-induced metastasis of colorectal cancer.

lncRNA PVT1: a novel oncogene in multiple cancers

Long noncoding RNAs are involved in epigenetic gene modification, including binding to the chromatin rearrangement complex in pre-transcriptional regulation and to gene promoters in gene expression regulation, as well as acting as microRNA sponges to control messenger RNA levels in post-transcriptional regulation. An increasing number of studies have found that long noncoding RNA plasmacytoma variant translocation 1 (PVT1) plays an important role in cancer development. In this review of a large number of studies on PVT1, we found that PVT1 is closely related to tumor onset, proliferation, invasion, epithelial–mesenchymal transformation, and apoptosis, as well as poor prognosis and radiotherapy and chemotherapy resistance in some cancers. This review comprehensively describes PVT1 expression in various cancers and presents novel approaches to the diagnosis and treatment of cancer.

CircRNA 0009043 suppresses non-small-cell lung cancer development via targeting the miR-148a-3p/DNAJB4 axis

Background

Circular RNAs (circRNAs) are important regulators of the development and progression of non-small-cell lung cancer (NSCLC) and many other malignancies. The functional importance of circ_0009043 in NSCLC, however, has yet to be established.

Methods

The expression of circ_0009043, miR-148a-3p, and DnaJ heat shock protein family (Hsp40) member B4 (DNAJB4) in NSCLC cells was assessed via qPCR. The proliferative activity of these cells was examined through EdU uptake and CCK-8 assays, while flow cytometry approaches were used to examine apoptotic cell death rates. Protein expression was measured through Western immunoblotting. Interactions between miR-148a-3p and circ_0009043 or DNAJB4 were detected through RNA immunoprecipitation (RIP) and dual-luciferase reporter assays. The in vivo importance of circ_0009043 as a regulator of oncogenic activity was assessed using murine xenograft models.

Results

Both NSCLC cells and tissue samples were found to exhibit circ_0009043 upregulation, and lower circ_0009043 expression levels were found to be related to poorer NSCLC patient overall survival. Knocking down circ_0009043 resulted in the enhancement of NSCLC cell proliferative activity and the suppression of apoptotic tumor cell death in vitro, while also driving more rapid in vivo tumorigenesis. Mechanistically, circ_0009043 was found to function as a molecular sponge that sequestered miR-148a-3p, which was in turn able to directly suppress DNAJB4 expression. When miR-148a-3p was overexpressed, this reversed the impact of knocking down circ_0009043 on the apoptotic death and proliferation of NSCLC cells. Conversely, miR-148a-3p inhibition resulted in the suppression of NSCLC cell apoptosis and the enhancement of tumor cell growth, while the downregulation of DNAJB4 reversed these changes.

Conclusion

Circ_0009043 acts as a tumor suppressor in NSCLC cells, promoting DNAJB4 upregulation via the sequestration of miR-148a-3p.

Prospects of circular RNAs: the regulators of drug resistance and metastasis in gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors. Although there are multiple therapeutic methods, the 5-year survival rate for GC remains low primarily due to metastasis and resistance to chemotherapy. GC treatments, which include chemotherapy drugs, targeted drugs, and immunologic drugs, improve the prognosis of advanced GC patients. Nevertheless, resistance to these drugs may result in treatment failure. Tumor metastasis also plays a key role in tumor progression and limits the clinical efficacy of treatments. Recently, it has been reported that circular RNAs (circRNAs), non-coding RNAs, regulate GC drug resistance and metastasis to improve prognosis. In this review, we summarized systematically the underlying mechanisms of circRNA regulation of gastric neoplasm drug resistance and tumor metastasis. Thus we shed light on the potential of circRNAs to function as potential GC biomarkers and therapeutics.

Oncogenic circular RNA circ_0007534 contributes to paclitaxel resistance in endometrial cancer by sponging miR-625 and promoting ZEB2 expression

Circular RNAs (circRNAs) and epithelial to mesenchymal transition (EMT) have been implicated in the development of human cancer and paclitaxel resistance. CircRNA circ_0007534 has been described as a key oncogenic circular RNA that is upregulated in a variety of cancer tissues. However, whether circ_0007534 causes EMT and paclitaxel resistance in endometrial cancer is still unknown. In this work, we revealed that circ_0007534 levels were significantly higher in endometrial cancer tissues, and that high circ_0007534 expression was associated with poor differentiation, advanced tumor stage, cancer invasion, cancer metastasis, and poor prognosis in endometrial cancer patients. Overexpression of circ_0007534 boosted endometrial cancer cell proliferation, invasion, EMT, and paclitaxel resistance. Knockdown of circ_0007534 restored paclitaxel sensitivity and reversed EMT in endometrial cancer cells. We also showed that circ_0007534 enhanced endometrial cancer aggressiveness, progression, and paclitaxel resistance by sponging microRNA-625 (miR-625) and subsequently increasing the expression of the miR-625 target gene ZEB2. Our cell functional studies demonstrated that inhibiting miR-625 or increasing ZEB2 mimicked the effects of circ_0007534 overexpression. Consequently, our data show that circ_0007534 plays a crucial role in EMT and paclitaxel resistance through miR-625/ZEB2 signaling. Targeting the circ_0007534/miR-625/ZEB2 pathway might be an effective strategy for overcoming paclitaxel resistance in endometrial cancer.

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.

Noncoding RNAs and their therapeutics in paclitaxel chemotherapy: Mechanisms of initiation, progression, and drug sensitivity

The identification of agents that can reverse drug resistance in cancer chemotherapy, and enhance the overall efficacy is of great interest. Paclitaxel (PTX) belongs to taxane family that exerts an antitumor effect by stabilizing microtubules and inhibiting cell cycle progression. However, PTX resistance often develops in tumors due to the overexpression of drug transporters and tumor-promoting pathways. Noncoding RNAs (ncRNAs) are modulators of many processes in cancer cells, such as apoptosis, migration, differentiation, and angiogenesis. In the present study, we summarize the effects of ncRNAs on PTX chemotherapy. MicroRNAs (miRNAs) can have opposite effects on PTX resistance (stimulation or inhibition) via influencing YES1, SK2, MRP1, and STAT3. Moreover, miRNAs modulate the growth and migration rates of tumor cells in regulating PTX efficacy. PIWI-interacting RNAs, small interfering RNAs, and short-hairpin RNAs are other members of ncRNAs regulating PTX sensitivity of cancer cells. Long noncoding RNAs (LncRNAs) are similar to miRNAs and can modulate PTX resistance/sensitivity by their influence on miRNAs and drug efflux transport. The cytotoxicity of PTX against tumor cells can also be affected by circular RNAs (circRNAs) and limitation is that oncogenic circRNAs have been emphasized and experiments should also focus on onco-suppressor circRNAs.

Circular RNA hsa_circ_0011298 enhances Taxol resistance of non-small cell lung cancer by regulating miR-486-3p/CRABP2 axis

Background

Circular RNAs (circRNAs) serve as critical regulators in the chemoresistance of human cancers, including non‐small cell lung cancer (NSCLC). We aimed to explore the role of hsa_circ_0011298 (circ_0011298) and its mechanism in Taxol resistance of NSCLC.

Methods

Circ_0011298, microRNA‐486‐3p (miR‐486‐3p), and CRABP2 mRNA expression were determined using qRT‐PCR. EdU and MTT assays were used to detect cell proliferation. Cell cycle distribution and cell apoptosis were detected by flow cytometry. Cell migratory and invasive abilities were detected using transwell assay. Cellular glycolysis was determined by specific kits. Protein levels were examined by western blot. Dual‐luciferase reporter and RIP assays were performed to confirm the relationship between miR‐486‐3p and circ_0011298 or CRABP2. Xenograft mice model was established to confirm the function of circ_0011298 in vivo.

Results

Circ_0011298 was overexpressed in Taxol‐resistant NSCLC cells and tissues. Circ_0011298 knockdown enhanced Taxol sensitivity by decreasing cell proliferation, migration, invasion, and glycolysis and inducing apoptosis and cell cycle arrest in Taxol‐resistant NSCLC cells. Circ_0011298 was a sponge of miR‐486‐3p, and the impact of circ_0011298 silencing on Taxol resistance was rescued by miR‐486‐3p inhibition. Moreover, miR‐486‐3p directly targeted CRABP2, and miR‐486‐3p inhibited Taxol resistance by targeting CRABP2. Furthermore, circ_0011298 regulated CRABP2 expression through targeting miR‐486‐3p. Importantly, circ_0011298 interference elevated Taxol sensitivity of NSCLC in vivo.

Conclusion

Circ_0011298 elevated Taxol resistance of NSCLC by sponging miR‐486‐3p and upregulating CRABP2, providing a possible circRNA‐targeted therapy for NSCLC.

Circ_0011292 Enhances Paclitaxel Resistance in Non-Small Cell Lung Cancer by Regulating miR-379-5p/TRIM65 Axis

Background: Non-small cell lung cancer (NSCLC) is the most prevalent cancer in the world. Chemotherapy resistance is a major obstacle to NSCLC therapy. This study explored the role and molecular mechanism of circular RNA 0011292 (circ_0011292) in tumorigenesis and chemoresistance of NSCLC. Methods: The levels of circ_0011292, miR-379-5p, and tripartite motif-containing protein 65 (TRIM65) were measured by quantitative real-time polymerase chain reaction or Western blot assay. Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was monitored by flow cytometry. Cell migration and invasion were detected by transwell assay. The levels of apoptosis-related and epithelial-mesenchymal transition-related proteins were examined by Western blot. The half-inhibition concentration (IC50) of paclitaxel (PTX) was evaluated by CCK-8 assay. Xenograft model was established to analyze the effect of circ_0011292 on PTX resistance of NSCLC in vivo. The interaction among circ_0011292, miR-379-5p, and TRIM65 was verified by dual-luciferase reporter assay and RNA immunoprecipitation assay. Results: Circ_0011292 and TRIM65 were upregulated, while miR-379-5p was downregulated in NSCLC tissues and cells. Circ_0011292 knockdown hindered NSCLC progression and enhanced PTX sensitivity of NSCLC. Circ_0011292 silencing reduced PTX resistance in vivo. Besides, miR-379-5p potentiated PTX sensitivity by targeting TRIM65. Also, circ_0011292 increased PTX resistance by sponging miR-379-5p. Conclusion: Circ_0011292 facilitated tumorigenesis and PTX resistance in NSCLC by regulating the miR-379-5p/TRIM65 axis, suggesting that circ_0011292 was a promising therapeutic target for NSCLC chemotherapy.

Exosomal circPVT1 derived from lung cancer promotes the progression of lung cancer by targeting miR-124-3p/EZH2 axis and regulating macrophage polarization

This study aims to probe the mechanism by which circPVT1 in lung cancer (LC)-derived exosomes (Exos) promotes proliferation, invasion and migration of LC cells by regulating macrophage polarization through miR-124-3p/EZH2 axis. The expressions of circPVT1 in blood-derived Exos extracted from lung adenocarcinoma (LA) patients were measured. Loss or gain-of-function experiments of circPVT1 and miR-124-3p were carried out to evaluate the effects of circPVT1 in LC-derived Exos and miR-124-3p on macrophage polarization toward M2 phenotype, whichi found that incubation of Exo-A with macrophages induced macrophage polarization to M2 type and M2-polarized macrophages co-incubated with A549 cells enhanced the biological function of LC cells. Co-incubation with M+ Exo-A-oecircPVT1 increased the proliferation, migration and invasion abilities of LC cells, while coculture with M+ Exo-A-si-circPVT1 reversed these abilities. The verification among circPVT1, miR-124-3p and EZH2 showed that miR-124-3p was negatively related to circPVT1 and EZH2, and EZH2 was positively related to circPVT1. CircPVT1 in LC-derived Exos increased EZH2 expression through inhibiting miR-124-3p expression level in macrophage. Taken togther, exosomal circPVT1 derived from LC mediates macrophage polarization via the miR-124-3p/EZH2 axis to potentiate LC cells' proliferation, invasion and migration.

CircRNA PVT1 promotes proliferation and chemoresistance of osteosarcoma cells via the miR-24-3p/KLF8 axis

OBJECTIVE

To investigate the regulatory effect and mechanism of circular RNA PVT1 (circPVT1) in proliferation and chemoresistance of osteosarcoma (OS) cells.

METHODS

The expression of circPVT1 in human OS and adjacent normal tissues was detected. The correlation between circPVT1 expression and clinical features of OS was analyzed. The expressions of circPVT1 and miR-24-3p in OS cells resistant to cisplatin, doxorubicin or methotrexate and parental OS cells were detected after cell transfection. CCK-8 and colony formation assay assessed the viability and proliferative ability of OS cells. qRT-PCR and Western blotting measured the expression of KLF8. Dual-luciferase reporter and RNA pull-down assays verified the targeting relationships of circPVT1/miR-24-3p and miR-24-3p/KLF8.

RESULTS

CircPVT1 was over-expressed in OS tissues and cells, and correlated with clinical features of OS. Over-expressed circPVT1 reduced the survival of OS patients. CircPVT1 was up-regulated in chemoresistant OS cells compared to their parental cells. CircPVT1 inhibition suppressed the proliferation and chemoresistance of OS cells. MiR-24-3p was under-expressed in OS cells and further down-regulated in chemoresistant cells. CircPVT1 could bind and down-regulate miR-24-3p. MiR-24-3p overexpression inhibited the proliferation and chemoresistance of OS cells. KLF8 was over-expressed in OS cells and further up-regulated in chemoresistant cells. MiR-24-3p negatively regulated the expression of KLF8.

CONCLUSION

CircPVT1 mediates proliferation and chemoresistance of OS cells via the miR-24-3p/KLF8 axis. The findings may provide guidance for clinical treatment of OS.

circ_AKT3 knockdown suppresses cisplatin resistance in gastric cancer

Background

Circular RNAs (circRNAs) are associated with cisplatin resistance in gastric cancer (GC). This study aims to explore the role of circRNA AKT serine/threonine kinase 3 (circ_AKT3) in the resistance of GC to cisplatin.

Methods

42 sensitive and 23 resistant GC patients were recruited for tissue collection. The cisplatin-resistant GC cells MKN-7/DDP and HGC-27/DDP were used for in vitro study. circ_AKT3, microRNA-206 (miR-206) and protein tyrosine phosphatase non-receptor type 14 (PTPN14) levels were detected via quantitative reverse transcription real-time PCR (qPCR) and Western blot. Cisplatin resistance was assessed by detecting P-glycoprotein (P-gp) level, half maximal inhibitory concentration (IC₅₀) of cisplatin and cell apoptosis. The target relationship between miR-206 and circ_AKT3 or PTPN14 was analyzed via dual-luciferase reporter and RNA pull-down assays. The role of circ_AKT3 in vivo was assessed using xenograft model.

Results

circ_AKT3 level was increased, but miR-206 was declined in cisplatin-resistant GC tissues and cells. circ_AKT3 knockdown or miR-206 overexpression decreased the level of P-gp and IC₅₀ of cisplatin and increased apoptosis of MKN-7/DDP and HGC-27/DDP cells. Additionally, circ_AKT3 targeted miR-206, and regulated cisplatin resistance by interacting with miR-206. PTPN14 was regulated by circ_AKT3 through miR-206 as a bridge. Also, circ_AKT3 knockdown decreased xenograft tumor growth.

Conclusion

circ_AKT3 knockdown suppressed cisplatin resistance using miR-206/PTPN14 axis in cisplatin-resistant GC cells.

Construction of a circRNA-miRNA-mRNA network based on differentially co-expressed circular RNA in gastric cancer tissue and plasma by bioinformatics analysis

BACKGROUND

Increasing evidence implicates circular RNAs (circRNAs) have been involved in human cancer progression. However, the mechanism remains unclear. In this study, we identified novel circRNAs related to gastric cancer and constructed a circRNA-miRNA-mRNA network.

METHODS

Microarray datasets GSE83521 and GSE93541 were obtained from the Gene Expression Omnibus (GEO). Then, we used computational biology to identify circRNAs that were differentially expressed in both GC tissue and plasma compared to normal controls; then, we detected the expression of the selected circRNAs in gastric cell lines by quantitative real-time polymerase chain reaction (qRT-PCR). We also identified circRNA-related candidate miRNAs and their target genes with online tools. Combining the predicted miRNAs and target mRNAs, a competing endogenous RNA regulatory network was established. Functional and pathway enrichment analyses were performed, and interactions between proteins were predicted by using String and Cytoscape. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to elucidate the possible functions of these differentially expressed circRNAs. The regulatory network constructed using the microarray datasets (GSE83521 and GSE93541) contained three differentially co-expressed circRNAs (DECs). A circRNA-miRNA-mRNA network was constructed based on 3 circRNAs, 43 miRNAs and 119 mRNAs.

RESULTS

GO and KEGG analysis showed that the regulation of apoptotic signaling pathway and PI3K-Akt signaling pathway were highest degrees of enrichment respectively. We established a protein-protein interaction (PPI) network consisting of 165 nodes and 170 edges and identified hub genes by using MCODE plugin in Cytoscape. Furthermore, a core circRNA-miRNA-mRNA network was constructed based on hub genes. Hsa_circ_0001013 was finally determined to play an important role in the pathogenesis of GC according to the core circRNA-miRNA-mRNA network.

CONCLUSIONS

We propose a new circRNA-miRNA-mRNA network that is associated with the pathogenesis of GC. The network may become a new molecular biomarker and could be used to develop potential therapeutic strategies for gastric cancer.

Circ_0006948 Contributes to Cell Growth, Migration, Invasion and Epithelial-Mesenchymal Transition in Esophageal Carcinoma

BACKGROUND

Circular RNAs (circRNAs) can act as promoters or inhibitors in cancer progression. Has_circ_0006948 (circ_0006948) was reported to aggravate the malignant behaviors of esophageal carcinoma (EC).

AIMS

This study focused on investigating the molecular mechanism of circ_0006948 in EC progression.

METHODS

The quantitative real-time polymerase chain reaction was performed to detect the expression of circ_0006948, microRNA-4262 (miR-4262) and fibronectin type III domain containing 3B (FNDC3B). Cell growth analysis was conducted by Cell Counting Kit-8 and colony formation assays. Cell migration and invasion were assessed by transwell assay. Epithelial-mesenchymal transition (EMT)-associated proteins and FNDC3B protein expression were assayed using western blot. Dual-luciferase reporter and RNA pull-down assays were performed to validate the target combination. Xenograft tumor assay was used for investigating the role of circ_0006948 in vivo.

RESULTS

Circ_0006948 was upregulated in EC tissues and cells. Downregulating the expression of circ_0006948 or FNDC3B repressed cell growth, migration, invasion and EMT in EC cells. Target analysis indicated that miR-4262 was a target for circ_0006948 and FNDC3B was a downstream gene for miR-4262. Moreover, circ_0006948 could affect the expression of FNDC3B via sponging miR-4262. The effects of si-circ_0006948#1 on EC cells were partly restored by miR-4262 inhibition or FNDC3B overexpression. In addition, circ_0006948 also facilitated EC tumorigenesis in vivo by targeting the miR-4262/FNDC3B axis.

CONCLUSION

Taken together, circ_0006948 functioned as an oncogenic factor in EC by the miR-4262-mediated FNDC3B expression regulation.

Noncoding RNAs and hyperthermic intraperitoneal chemotherapy in advanced gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors globally. About 20-30% of patients with gastric cancer show peritoneal implantation metastasis at the first diagnosis. Peritoneal metastasis is responsible for 70% of deaths of patients with advanced gastric cancer. Although there are many ways to treat advanced gastric cancer, the prognosis of patients with recurrence is unsatisfactory. An auxiliary treatment with hyperthermic intraperitoneal chemotherapy (HIPEC), is an internationally recognized recommended treatment for advanced gastric cancer. A series of clinical trials have shown that HIPEC significantly improves the overall survival of patients with cancer. Compared with the cytoreductive surgery (CRS) alone, HIPEC combined with CRS markedly reduced the rate of peritoneal metastasis in patients with ovarian cancer and colorectal cancer. It has been demonstrated that HIPEC alters transcription of many genes by affecting non-coding RNAs, which may contribute to the suppressive effect of HIPEC on the synthesis of nucleic acids and proteins in cancer cells. This paper reviews the recent advances in understanding the role of non-coding RNAs in tumor invasion and metastasis of advanced gastric cancer. We also consider changes in noncoding RNA levels and other molecules in advanced gastric cancer cases treated with HIPEC. We hope that our review will provide a reference for future research on molecular epidemiology and etiology of advanced gastric cancer and promote precise treatment of this malignancy using HIPEC.

CircPVT1: a pivotal circular node intersecting Long Non-Coding-PVT1 and c-MYC oncogenic signals

The role of circular RNAs in oncogenesis has begun to be widely studied in recent years, due to the significant impact that these molecules have in disease pathogenesis, as well as their potential for the future of innovative therapies. Moreover, due to their characteristically circular shape, circular RNAs are very resistant molecules to RNA degradation whose levels are easily assessed in body fluids. Accordingly, they represent an opportunity for the discovery of new diagnostic and prognostic markers in a wide range of diseases. Among circular RNAs, circPVT1 is a rather peculiar one that originates from the circularization of the exon 2 of the PVT1 gene that encodes a pro-tumorigenic long non-coding RNA named lncPVT1. There are a few examples of circular RNAs that derive from a locus producing another non-coding RNA. Despite their apparent transcriptional independence, which occurs using two different promoters, a possible synergistic effect in tumorigenesis cannot be excluded considering that both have been reported to correlate with the oncogenic phenotype. This complex mechanism of regulation appears to also be controlled by c-MYC. Indeed, the PVT1 locus is located only 53 Kb downstream c-MYC gene, a well-known oncogene that regulates the expression levels of about 15% of all genes. Here, we review circPVT1 origin and biogenesis highlighting the most important mechanisms through which it plays a fundamental role in oncogenesis, such as the well-known sponge activity on microRNAs, as well as its paradigmatic interactome link with lncPVT1 and c-MYC expression.

The Emerging Roles of Circular RNAs in the Chemoresistance of Gastrointestinal Cancer

Gastrointestinal (GI) cancer represents a major global health problem due to its aggressive characteristics and poor prognosis. Despite the progress achieved in the development of treatment regimens, the clinical outcomes and therapeutic responses of patients with GI cancer remain unsatisfactory. Chemoresistance arising throughout the clinical intervention is undoubtedly a critical barrier for the successful treatment of GI cancer. However, the precise mechanisms associated with chemoresistance in GI cancer remain unclear. In the past decade, accumulating evidence has indicated that circular RNAs (circRNAs) play a key role in regulating cancer progression and chemoresistance. Notably, circRNAs function as molecular sponges that sequester microRNAs (miRNAs) and/or proteins, and thus indirectly control the expression of specific genes, which eventually promote or suppress drug resistance in GI cancer. Therefore, circRNAs may represent potential therapeutic targets for overcoming drug resistance in patients with GI cancer. This review comprehensively summarizes the regulatory roles of circRNAs in the development of chemoresistance in different GI cancers, including colorectal cancer, gastric cancer and esophageal cancer, as well as deciphers the underlying mechanisms and key molecules involved. Increasing knowledge of the important functions of circRNAs underlying drug resistance will provide new opportunities for developing efficacious therapeutic strategies against GI cancer.

CircRNF121 knockdown suppresses the progression of cervical cancer by regulating miR-153-3p/ATF2 axis and wnt/β-catenin pathway

Cervical cancer (CC) is a common malignancy in gynecology. Emerging evidence has demonstrated that circular RNAs (circRNAs) act as vital mediators in CC. However, the roles of circRNA ring finger protein 121 (circRNF121) in CC are largely unknown. Herein, we focused on the exact function and underlying mechanism of circRNF121 in CC development. Our results showed that circRNF121 was highly expressed in CC tissues and cells. Knockdown of circRNF121 suppressed cell growth, metastasis, epithelial-mesenchymal transition (EMT), autophagy, and wnt/β-catenin pathway in CC cells in vitro and blocked tumor formation in vivo. For mechanism investigation, circRNF121 could affect activating transcription factor 2 (ATF2) expression by decoying miR-153-3p, thereby accelerating CC cell development. In conclusion, circRNF121 exerted the tumor-suppressive role in CC progression by altering miR-153-3p/ATF2 axis. These results suggested that circRNF121 might be a possible circ-targeted therapy for patients with CC.

The Molecular Roles and Clinical Implications of Non-Coding RNAs in Gastric Cancer

Gastric cancer (GC) is one of the most common malignancies in the world. It is also the fifth most common cancer in China. In recent years, a large number of studies have proved that non-coding RNAs (ncRNAs) can regulate cell proliferation, invasion, metastasis, apoptosis, and angiogenesis. NcRNAs also influence the therapeutic resistance of gastric cancer. NcRNAs mainly consist of miRNAs, lncRNAs and circRNAs. In this paper, we summarized ncRNAs as biomarkers and therapeutic targets for gastric cancer, and also reviewed their role in clinical trials and diagnosis. We sum up different ncRNAs and related moleculars and signaling pathway in gastric cancer, like Bcl-2, PTEN, Wnt signaling. In addition, the potential clinical application of ncRNAs in overcoming chemotherapy and radiotherapy resistance in GC in the future were also focused on.

Mechanisms of Action And Clinical Implications of MicroRNAs in the Drug Resistance of Gastric Cancer

Gastric cancer (GC) is one of the most common malignant tumors of digestive systems worldwide, with high recurrence and mortality. Chemotherapy is still the standard treatment option for GC and can effectively improve the survival and life quality of GC patients. However, with the emergence of drug resistance, the clinical application of chemotherapeutic agents has been seriously restricted in GC patients. Although the mechanisms of drug resistance have been broadly investigated, they are still largely unknown. MicroRNAs (miRNAs) are a large group of small non-coding RNAs (ncRNAs) widely involved in the occurrence and progression of many cancer types, including GC. An increasing amount of evidence suggests that miRNAs may play crucial roles in the development of drug resistance by regulating some drug resistance-related proteins as well as gene expression. Some also exhibit great potential as novel biomarkers for predicting drug response to chemotherapy and therapeutic targets for GC patients. In this review, we systematically summarize recent advances in miRNAs and focus on their molecular mechanisms in the development of drug resistance in GC progression. We also highlight the potential of drug resistance-related miRNAs as biomarkers and therapeutic targets for GC patients.

CircARVCF Contributes to Cisplatin Resistance in Gastric Cancer by Altering miR-1205 and FGFR1

Background: Chemoresistance is a major barrier to the treatment of human cancers. Circular RNAs (circRNAs) are implicated in drug resistance in cancers, including gastric cancer (GC). In this study, we aimed to explore the functions of circRNA Armadillo Repeat gene deleted in Velo-Cardio-Facial syndrome (circARVCF) in cisplatin (DDP) resistance in GC.

Methods: The expression of circARVCF, microRNA-1205 (miR-1205) and fibroblast growth factor receptor 1 (FGFR1) was detected by quantitative real-time polymerase chain reaction (qRT-PCR), western blot assay or immunohistochemistry (IHC) assay. Cell Counting Kit-8 (CCK-8) assay and colony formation assay were performed to evaluate DDP resistance and cell colony formation ability. Transwell assay was conducted to assess cell migration and invasion. Flow cytometry analysis was done to analyze cell apoptosis. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were manipulated to analyze the relationships of circARVCF, miR-1205 and FGFR1. Murine xenograft model was constructed to explore DDP resistance in vivo.

Results: CircARVCF level was increased in DDP-resistant GC tissues and cells. CircARVCF silencing inhibited DDP resistance, colony formation and metastasis and induced apoptosis in DDP-resistant GC cells. CircARVCF directly interacted with miR-1205 and miR-1205 inhibition reversed circARVCF silencing-mediated effect on DDP resistance in DDP-resistant GC cells. FGFR1 served as the target gene of miR-1205. MiR-1205 overexpression restrained the resistance of DDP-resistant GC cells to DDP, but FGFR1 elevation abated the effect. In addition, circARVCF knockdown repressed DDP resistance in vivo.

Conclusion: CircARVCF enhanced DDP resistance in GC by elevating FGFR1 through sponging miR-1205.

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.

A Concise Review on the Role of CircPVT1 in Tumorigenesis, Drug Sensitivity, and Cancer Prognosis

CircPVT1 (hsa_circ_0001821) is a cancer-related circular RNA (circRNA) that originated from a genomic locus on chromosome 8q24. This locus has been previously found to encode the oncogenic long non-coding RNA PVT1. Expression of this circRNA has been found to be upregulated in diverse neoplastic conditions. CircPVT1 acts as a sponge for miR-125a, miR-125b, miR-124-3p, miR-30a-5p, miR-205-5p, miR-423-5p, miR-526b, miR-137, miR-145-5p, miR-497, miR-30d/e, miR-455-5p, miR-29a-3p, miR-204-5p, miR-149, miR-106a-5p, miR-377, miR-3666, miR-203, and miR-199a-5p. Moreover, it can regulate the activities of PI3K/AKT, Wnt5a/Ror2, E2F2, and HIF-1α. Upregulation of circPVT1 has been correlated with decreased survival of patients with different cancer types. In the current review, we explain the oncogenic impact of circPVT1 in different tissues based on evidence from in vitro, in vivo, and clinical investigations.

Non-Coding RNAs in Gastric Cancer: From Malignant Hallmarks to Clinical Applications

Gastric cancer (GC) is one of the most lethal malignancies worldwide. However, the molecular mechanisms underlying gastric carcinogenesis remain largely unknown. Over the past decades, advances in RNA-sequencing techniques have greatly facilitated the identification of various non-coding RNAs (ncRNAs) in cancer cells, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Accumulating evidence has revealed that ncRNAs are essential regulators in GC occurrence and development. However, ncRNAs represent an emerging field of cancer research, and their complex functionality remains to be clarified. Considering the lack of viable biomarkers and therapeutic targets in GC, further studies should focus on elucidating the intricate relationships between ncRNAs and GC, which can be translated into clinical practice. In this review, we summarize recent research progress on how ncRNAs modulate the malignant hallmarks of GC, especially in tumor immune escape, drug resistance, and stemness. We also discuss the promising applications of ncRNAs as diagnostic biomarkers and therapeutic targets in GC, aiming to validate their practical value for clinical treatment.

Research progress of circRNAs in chemotherapy resistance of digestive system neoplasms

Circular RNAs (circRNAs) are a novel class of noncoding RNA molecules with a unique closed continuous loop structure. CircRNAs are abundant in eukaryotic cells, have unique stability and tissue specificity, and can play a biological regulatory role at various levels, such as transcriptional and posttranscriptional levels. Accumulating evidence indicates that circRNAs play critical roles in tumor genesis, development, and chemotherapy. Chemotherapy is a primary type of intervention for most cancers, but its therapeutic efficacy is usually retarded by intrinsic and acquired resistance. CircRNAs regulate tumor chemoresistance through various molecular mechanisms, such as affecting apoptosis, promoting drug transportation, promoting DNA repair, promoting epithelial-mesenchymal transformation, regulating the characteristics of tumor stem cells, and affecting autophagy. This review summarizes the recent progress and mechanisms of circRNAs in cancer cell resistance to chemotherapy.

Circ_0061140 knockdown inhibits tumorigenesis and improves PTX sensitivity by regulating miR-136/CBX2 axis in ovarian cancer

Background

Ovarian cancer is an aggressive tumor in women with high mortality. Paclitaxel (PTX) can be used for the chemotherapy of ovarian cancer. Here, the roles of circular_0061140 (circ_0061140) in PTX sensitivity and malignant progression of ovarian cancer are unveiled.

Methods

The expressions of circ_0061140, microRNA-136 (miR-136) and chromobox 2 (CBX2) mRNA were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Protein expression was determined by western blot. The half maximal inhibitory concentration (IC₅₀) of PTX was determined by 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was investigated by cell counting kit-8 (CCK-8) and colony formation assays. Cell apoptosis was demonstrated by flow cytometry analysis. Cell migration and invasion were evaluated by transwell assay. The binding relationship between miR-136 and circ_0061140 or CBX2 was predicted by interactome or starbase online database, and identified by dual-luciferase reporter assay. The effects of circ_0061140 on tumor formation and PTX sensitivity in vivo were disclosed by tumor formation assay.

Results

Circ_0061140 and CBX2 expressions were upregulated, while miR-136 expression was downregulated in PTX-resistant tissues and cells compared with control groups. Circ_0061140 knockdown repressed cell proliferation, migration and invasion, and promoted cell apoptosis and PTX sensitivity; however, these effects were restrained by miR-136 RNAi. Additionally, circ_0061140 was a sponge of miR-136, and miR-136 bound to CBX2. Furthermore, circ_0061140 knockdown inhibited tumor formation and improved PTX sensitivity in vivo.

Conclusions

Circ_0061140 silencing repressed the progression and PTX resistance of ovarian cancer by downregulating CBX2 expression via sponging miR-136, which provided novel insight into studying the therapy of ovarian cancer with PTX.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13048-021-00888-9.