Knockdown of circHIPK3 Facilitates Temozolomide Sensitivity in Glioma by Regulating Cellular Behaviors Through miR-524-5p/KIF2A-Mediated PI3K/AKT Pathway

LncRNA MCM3AP-AS1 promotes chemoresistance in triple-negative breast cancer through the miR-524-5p/RBM39 axis

Triple-negative breast cancer (TNBC) is the most lethal subtype of BC, with unfavorable treatment outcomes. Evidence suggests the engagement of lncRNA MCM3AP-AS1 in BC development. This study investigated the action of MCM3AP-AS1 in chemoresistance of TNBC cells. Drug-resistant TNBC cell lines SUM159PTR and MDA-MB-231R were constructed by exposure to increasing concentrations of doxorubicin/docetaxel (DOX/DXL). MCM3AP-AS1 and miR-524-5p expression levels were determined by RT-qPCR. RNA binding motif 39 (RBM39) level was measured using Western blot. Cell viability and apoptosis were assessed by CCK-8 assay and flow cytometry. The targeted binding of miR-524-5p with MCM3AP-AS1 or RBM39 was predicted by ECORI database and validated by dual-luciferase assays. The gain-and-loss of function assays were conducted in cells to investigate the interactions among MCM3AP-AS1, miR-524-5p, and RBM39. TNBC xenograft mouse models were established through subcutaneous injection of MCM3AP-AS1-silencing MDA-MB-231R cells and intraperitoneally administrated with DOX/DXL to verify the role of MCM3AP-AS1 in vivo. MCM3AP-AS1 was upregulated in drug-resistant TNBC cells, and MCM3AP-AS1 silencing could sensitize drug-resistant TNBC cells to chemotherapeutic drugs by promoting apoptosis. MCM3AP-AS1 targeted miR-524-5p. After DOX/DXL treatment, miR-524-5p inhibition partially reversed the effect of MCM3AP-AS1 silencing on inhibiting chemoresistance and promoting apoptosis of drug-resistant TNBC cells. miR-524-5p targeted RBM39. Silencing MCM3AP-AS1 promoted apoptosis via the miR-524-5p/RBM39 axis, thereby enhancing chemosensitivity of drug-resistant TNBC cells. MCM3AP-AS1 knockdown upregulated miR-524-5p, downregulated RBM39, and restrained tumor development in vivo. MCM3AP-AS1 silencing potentiates apoptosis of drug-resistant TNBC cells by upregulating miR-524-5p and downregulating RBM39, thereby suppressing chemoresistance in TNBC.

The potential of circHIPK3 as a biomarker in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by leukocytosis and left shift. The primary molecular alteration is the BCR::ABL1, chimeric oncoprotein with tyrosine kinase activity, responsible for the initial oncogenesis of the disease. Therapy of CML was revolutionized with the advent of tyrosine kinase inhibitors, but it is still not considered curative and may present resistance and serious adverse effects. Discoveries in CML inaugurated a new era in cancer treatment and despite all the advances, a new biomarker is needed to detect resistance and adverse effects. Circular RNAs (circRNAs) are a special type of non-coding RNA formed through a process called backsplicing. The majority of circRNAs are derived from protein-coding genes. CircHIPK3 is formed from the second exon of the HIPK3 gene and has been found in various pathologies, including different types of cancer. New approaches have demonstrated the potential of circular RNAs in cancer research, and circHIPK3 has shown promising results. It is often associated with cellular regulatory pathways, suggesting an important role in the molecular dynamics of tumors. The identification of biomarkers is an important tool for therapeutic improvement; thus we review the role of circHIPK3 and its potential as a biomarker in CML.

CircHIPK3 contributes to cisplatin resistance in gastric cancer by blocking autophagy-dependent ferroptosis

Cisplatin is the first-line chemotherapy for gastric cancer (GC). However, its efficacy is dampened by the development of chemoresistance, which leads to poor prognosis in GC patients. Recently, evidence has revealed that circular RNAs (circRNAs) and dysregulation of autophagy-dependent ferroptosis play critical roles in cancer chemoresistance. Herein, for the first time we report that circHIPK3 has a vital role in GC cisplatin resistance. CircHIPK3 regulated cisplatin resistance by targeting autophagy and ferroptosis. In brief, knockdown circHIPK3 decreased GC cell cisplatin resistance by enhancing ferroptosis via the miR-508-3p/Bcl-2/beclin1/SLC7A11 axis. Taken together, our results demonstrate that ferroptosis is a promising strategy to ameliorate cisplatin resistance. Importantly, serum exosomal circHIPK3 could also be a noninvasive indicator to evaluate cisplatin resistance in GC.

Epigenetic regulation of temozolomide resistance in human cancers with an emphasis on brain tumors: Function of non-coding RNAs

Brain tumors, which are highly malignant, pose a significant threat to health and often result in substantial rates of mortality and morbidity worldwide. The brain cancer therapy has been challenging due to obstacles such as the BBB, which hinders effective delivery of therapeutic agents. Additionally, the emergence of drug resistance further complicates the management of brain tumors. TMZ is utilized in brain cancer removal, but resistance is a drawback. ncRNAs are implicated in various diseases, and their involvement in the cancer is particularly noteworthy. The focus of the current manuscript is to explore the involvement of ncRNAs in controlling drug resistance, specifically in the context of resistance to the chemotherapy drug TMZ. The review emphasizes the function of ncRNAs, particularly miRNAs, in modulating the growth and invasion of brain tumors, which significantly influences their response to TMZ treatment. Through their interactions with various molecular pathways, miRNAs are modulators of TMZ response. Similarly, lncRNAs also associate with molecular pathways and miRNAs, affecting the efficacy of TMZ chemotherapy. Given their functional properties, lncRNAs can either induce or suppress TMZ resistance in brain tumors. Furthermore, circRNAs, which are cancer controllers, regulate miRNAs by acting as sponges, thereby impacting the response to TMZ chemotherapy. The review explores the correlation between ncRNAs and TMZ chemotherapy, shedding light on the underlying molecular pathways involved in this process.

CircTTLL13 Promotes TMZ Resistance in Glioma via Modulating OLR1-Mediated Activation of the Wnt/β-Catenin Pathway

Glioma, originating from neuroglial progenitor cells, is a type of intrinsic brain tumor with poor prognosis. temozolomide (TMZ) is the first-line chemotherapeutic agent for glioma. Exploring the mechanisms of circTTLL13 underlying TMZ resistance in glioma is of great significance to improve glioma treatment. Bioinformatics was adopted to identify target genes. The circular structure of circTTLL13 and its high expression in glioma cells were disclosed by quantitative real time-PCR (qRT-PCR) and PCR-agarose gel electrophoresis. Functional experiments proved that oxidized LDL receptor 1 (OLR1) promotes TMZ resistance of glioma cells. CircTTLL13 enhances TMZ resistance of glioma cells via modulating OLR1. Luciferase reporter, RNA-binding protein immunoprecipitation (RIP), RNA pulldown, mRNA stability, N6-methyladenosine (m6A) dot blot and RNA total m6A quantification assays were implemented, indicating that circTTLL13 stabilizes OLR1 mRNA via recruiting YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) and promotes m6A methylation of OLR1 pre-mRNA through recruiting methyltransferase-like 3 (METTL3). TOP/FOP-flash reporter assay and western blot verified that circTTLL13 activates Wnt/β-catenin signaling pathway by regulating OLR1. CircTTLL13 promotes TMZ resistance in glioma through regulating OLR1-mediated Wnt/β-catenin pathway activation. This study offers an insight into the efficacy improvement of TMZ for glioma treatment.

HPV16 E6E7 up-regulates KIF2A expression by activating JNK/c-Jun signal, is beneficial to migration and invasion of cervical cancer cells

Cervical cancer is the fourth most common cancer and the fourth leading cause of cancer death in women. Human papillomavirus (HPV16) E6/E7 heterogenous expression in C33A cells increased the mRNA and protein levels of KIF2A, while siRNA deletion of endogenous E6/E7 reduced the mRNA and protein levels of KIF2A in SiHa cells. KIF2A promoted cell migration and invasion, and regulated the expression of epithelial-mesenchymal transition-related proteins in C33A and SiHa cells. The exogenous expression of E6/E7 in C33A cells increased the phosphorylation of Akt, ERK, and JNK. However, Akt (API-2) and ERK (PD98059) inhibitors had no effect on the increase in KIF2A expression induced by E6/E7, while JNK inhibitors (JNK-IN-8 and SP600125) blocked the increase in KIF2A expression induced by E6/E7. The exogenous expression of E6/E7 increased the levels of transcription factor c-Jun, which is the classic substrate of JNK. Knockdown of c-Jun reduced the increase in KIF2A expression induced by E6/E7. In summary, KIF2A plays a key role in the motility and metastasis of cervical cancer. HPV16 E6/E7 can increase the levels of transcription factor c-Jun by activating the JNK signal, thereby up-regulating the transcriptional expression of KIF2A.

Exosomal noncoding RNAs in central nervous system diseases: biological functions and potential clinical applications

Central nervous system (CNS) disease is a general term for a series of complex and diverse diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), CNS tumors, stroke, epilepsy, and amyotrophic lateral sclerosis (ALS). Interneuron and neuron-glia cells communicate with each other through their homeostatic microenvironment. Exosomes in the microenvironment have crucial impacts on interneuron and neuron-glia cells by transferring their contents, such as proteins, lipids, and ncRNAs, constituting a novel form of cell-to-cell interaction and communication. Exosomal noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and PIWI-interacting RNAs (piRNAs), regulate physiological functions and maintain CNS homeostasis. Exosomes are regarded as extracellular messengers that transfer ncRNAs between neurons and body fluids due to their ability to cross the blood-brain barrier. This review aims to summarize the current understanding of exosomal ncRNAs in CNS diseases, including prospective diagnostic biomarkers, pathological regulators, therapeutic strategies and clinical applications. We also provide an all-sided discussion of the comparison with some similar CNS diseases and the main limitations and challenges for exosomal ncRNAs in clinical applications.

The Diagnostic and Therapeutic Role of Circular RNA HIPK3 in Human Diseases

Circular RNAs (circRNAs) are a class of noncoding RNAs with closed-loop of single-stranded RNA structure. Although most of the circRNAs do not directly encode proteins, emerging evidence suggests that circRNAs play a pivotal and complex role in multiple biological processes by regulating gene expression. As one of the most popular circRNAs, circular homeodomain-interacting protein kinase 3 (circHIPK3) has frequently gained the interest of researchers in recent years. Accumulating studies have demonstrated the significant impacts on the occurrence and development of multiple human diseases including cancers, cardiovascular diseases, diabetes mellitus, inflammatory diseases, and others. The present review aims to provide a detailed description of the functions of circHIPK3 and comprehensively overview the diagnostic and therapeutic value of circHIPK3 in these certain diseases.

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.

Non-coding RNAs and glioblastoma: Insight into their roles in metastasis

Glioma, also known as glioblastoma multiforme (GBM), is the most prevalent and most lethal primary brain tumor in adults. Gliomas are highly invasive tumors with the highest death rate among all primary brain malignancies. Metastasis occurs as the tumor cells spread from the site of origin to another site in the brain. Metastasis is a multifactorial process, which depends on alterations in metabolism, genetic mutations, and the cancer microenvironment. During recent years, the scientific study of non-coding RNAs (ncRNAs) has led to new insight into the molecular mechanisms involved in glioma. Many studies have reported that ncRNAs play major roles in many biological procedures connected with the development and progression of glioma. Long ncRNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs) are all types of ncRNAs, which are commonly dysregulated in GBM. Dysregulation of ncRNAs can facilitate the invasion and metastasis of glioma. The present review highlights some ncRNAs that have been associated with metastasis in GBM. miRNAs, circRNAs, and lncRNAs are discussed in detail with respect to their relevant signaling pathways involved in metastasis.

circHIPK3 Exacerbates Folic Acid-Induced Renal Tubulointerstitial Fibrosis by Sponging miR-30a

Renal tubulointerstitial fibrosis is a common pathological feature of progressive chronic kidney disease (CKD), and current treatment has limited efficacy. The circular RNA circHIPK3 is reported to participate in the pathogenesis of various human diseases. However, the role of circHIPK3 in renal fibrosis has not been examined. In this study, we aimed to determine whether and how circHIPK3 might participate in the pathogenesis of renal fibrosis. Mice received a peritoneal injection of folic acid (250 mg/kg). Of note, 30 days later, renal fibrosis was present on periodic acid-Schiff (PAS) and Masson staining, and mRNA and protein of profibrotic genes encoding fibronectin (FN) and collagen 1 (COL1) were increased. Renal circHIPK3 was upregulated, while miR-30a was downregulated, assessed by quantitative PCR (qPCR) and fluorescence in situ hybridization (FISH). The expression of transforming growth factor beta-1 (TGF-β1) was increased by qPCR analysis, immunoblotting, and immunofluorescence. Renal circHIPK3 negatively correlated with miR-30a, and kidney miR-30a negatively correlated with TGF-β1. Target Scan and miRanda algorithms predicted three perfect binding sites between circHIPK3 and miR-30a. We found that circHIPK3, miR-30a, and TGF-β1 colocalized in the cytoplasm of human tubular epithelial cells (HK-2 cells) on FISH and immunofluorescence staining. We transfected circHIPK3 and a scrambled RNA into HK-2 cells; miR-30a was downregulated, and the profibrotic genes such as TGF-β1, FN, and COL1 were upregulated and assessed by qPCR, immunoblotting, and immunofluorescence staining. Third, the upregulation of circHIPK3, downregulation of miR-30a, and overproduction of profibrotic FN and COL1 were also observed in HK-2 cells exposed to TGF-β1. Finally, renal biopsies from patients with chronic tubulointerstitial nephritis manifested similar expression patterns of circHIPK3, miR-30a, and profibrotic proteins, such as TGF-β1, FN, and COL1 as observed in the experimental model. A feed-forward cycle was observed among circHIPK3, miR-30a, and TGF-β1. Our results suggest that circHIPK3 may contribute to progressive renal fibrosis by sponging miR-30a. circHIPK3 may be a novel therapeutic target for slowing CKD progression.

The Role of Circular RNAs in the Drug Resistance of Cancers

Cancer is a major threat to human health and longevity. Chemotherapy is an effective approach to inhibit cancer cell proliferation, but a growing number of cancer patients are prone to develop resistance to various chemotherapeutics, including platinum, paclitaxel, adriamycin, and 5-fluorouracil, among others. Significant progress has been made in the research and development of chemotherapeutic drugs over the last few decades, including targeted therapy drugs and immune checkpoint inhibitors; however, drug resistance still severely limits the application and efficacy of these drugs in cancer treatment. Recently, emerging studies have emphasized the role of circular RNAs (circRNAs) in the proliferation, migration, invasion, and especially chemoresistance of cancer cells by regulating the expression of related miRNAs and targeted genes. In this review, we comprehensively summarized the potential roles and mechanisms of circRNAs in cancer drug resistance including the efflux of drugs, apoptosis, intervention with the TME (tumor microenvironment), autophagy, and dysfunction of DNA damage repair, among others. Furthermore, we highlighted the potential value of circRNAs as new therapeutic targets and prognostic biomarkers for cancer.

Crosstalk between circRNAs and the PI3K/AKT signaling pathway in cancer progression

Circular RNAs (circRNAs), covalently closed noncoding RNAs, are widely expressed in eukaryotes and viruses. They can function by regulating target gene expression, linear RNA transcription and protein generation. The phosphoinositide 3-kinase (PI3K)/AKT signaling pathway plays key roles in many biological and cellular processes, such as cell proliferation, growth, invasion, migration, and angiogenesis. It also plays a pivotal role in cancer progression. Emerging data suggest that the circRNA/PI3K/AKT axis modulates the expression of cancer-associated genes and thus regulates tumor progression. Aberrant regulation of the expression of circRNAs in the circRNA/PI3K/AKT axis is significantly associated with clinicopathological characteristics and plays an important role in the regulation of biological functions. In this review, we summarized the expression and biological functions of PI3K-AKT-related circRNAs in vitro and in vivo and assessed their associations with clinicopathological characteristics. We also further discussed the important role of circRNAs in the diagnosis, prognostication, and treatment of cancers.

Research Progress on Circular RNA in Glioma

The discovery of circular RNA (circRNA) greatly complements the traditional gene expression theory. CircRNA is a class of non-coding RNA with a stable cyclic structure. They are highly expressed, spatiotemporal-specific and conservative across species. Importantly, circRNA participates in the occurrence of many kinds of tumors and regulates the tumor development. Glioma is featured by limited therapy and grim prognosis. Cancer-associated circRNA compromises original function or creates new effects in glioma, thus contributing to oncogenesis. Therefore, this article reviews the biogenesis, metabolism, functions and properties of circRNA as a novel potential biomarker for gliomas. We elaborate the expression characteristics, interaction between circRNA and other molecules, aiming to identify new targets for early diagnosis and treatment of gliomas.

miRNA-223-3p modulates ibrutinib resistance through regulation of the CHUK/Nf-κb signaling pathway in mantle cell lymphoma

Since the use of Bruton's tyrosine kinase (BTK) inhibitor ibrutinib in relapsed/refractory (R/R) mantle cell lymphoma (MCL), the problem of drug resistance has become increasingly prominent. Though it has been proven that the nonclassic nuclear factor κB pathway (nonclassic NF-κB pathway) correlates with ibrutinib resistance in MCL, the upstream regulator is unknown. In the present study, conserved helix-loop-helix ubiquitous kinase (CHUK) overexpression accelerated proliferation and suppressed apoptosis of MCL cells after ibrutinib treatment in vitro. The results of luciferase reporter assay, real-time quantitative polymerase chain reaction (RT-qPCR), and Western blot revealed that CHUK was targeted and negatively regulated by miRNA-223-3p. miRNA-223-3p knockdown promoted proliferation and inhibited apoptosis of MCL cells after ibrutinib treatment in vitro and vivo, whereas CHUK knockdown reversed downregulated miRNA-223-3p-promoted cell proliferation after ibrutinib treatment in vitro. In conclusion, miRNA-223-3p modulates ibrutinib resistance through regulation of the CHUK/NF-κB signaling pathway in MCL, which is crucial in providing a marker to predict disease response.

Hsa_circ_0004674 promotes osteosarcoma doxorubicin resistance by regulating the miR-342-3p/FBN1 axis

Background

The occurrence of chemoresistance is a common problem in tumor treatment. Circular RNA (circRNA) has been confirmed to be related to tumor chemoresistance. However, the role and the underlying molecular mechanism of hsa_circ_0004674 in the chemoresistance of osteosarcoma (OS) are still unclear.

Methods

The expression of hsa_circ_0004674, miR-342-3p, and fibrillin-1 (FBN1) was determined by qRT-PCR. Cell counting kit 8 assay was used to evaluate the doxorubicin (DXR) resistance of cells. The proliferation and apoptosis of cells were measured using colony formation assay and flow cytometry. Western blot analysis was utilized to examine the protein levels of resistance markers, Wnt/β-catenin pathway markers and FBN1. The interaction between miR-342-3p and hsa_circ_0004674 or FBN1 was confirmed by dual-luciferase reporter assay and RNA pull-down assay. Moreover, animal experiments were performed to assess the effect of hsa_circ_0004674 silencing on the DXR sensitive of OS in vivo.

Results

The upregulated hsa_circ_0004674 was found in DXR-resistant OS tissues and cells. Knockdown of hsa_circ_0004674 could inhibit the DXR resistance of OS cells in vitro and promote the DXR sensitive of OS tumors in vivo. In addition, we discovered that hsa_circ_0004674 could sponge miR-342-3p, and miR-342-3p could target FBN1. MiR-342-3p inhibitor could reverse the inhibition effect of hsa_circ_0004674 knockdown on the DXR resistance of OS cells. Similarly, the suppressive effect of miR-342-3p on the DXR resistance of OS cells also could be reversed by FBN1 overexpression. Furthermore, we revealed that hsa_circ_0004674 silencing inhibited the activity of Wnt/β-catenin pathway by the miR-342-3p/FBN1 axis.

Conclusion

Hsa_circ_0004674 facilitated the DXR resistance of OS through Wnt/β-catenin pathway via regulating the miR-342-3p/FBN1 axis, suggesting that hsa_circ_0004674 was a promising target for the chemoresistance of OS.

Exosomal noncoding RNAs: key players in glioblastoma drug resistance

Glioma, as one of the most severe human malignancies, is defined as the Central Nervous System's (CNS) tumors. Glioblastoma (GBM) in this regard, is the most malignant type of gliomas. There are multiple therapeutic strategies to cure GBM, for which chemotherapy is often the first-line treatment. Still, various cellular processes, such as uncontrolled proliferation, invasion and metastasis, may disturb the treatment efficacy. Drug resistance is another process in this way, which can also cause undesirable effects. Thereupon, identifying the mechanisms, involved in developing drug resistance and the relevant mechanisms can be very helpful in GBM management. The discovery of exosomal non-coding RNAs (ncRNAs), RNA molecules that can be transferred between the cells and different tissues using the exosomes, was a milestone in this regard. It has been revealed that the key exosomal ncRNAs, including circular RNAs, microRNAs, and long ncRNAs, are able to modulate GBM drug resistance through different signaling pathways or by affecting regulatory proteins and their corresponding genes. Nowadays, researchers are trying to overcome the limitations of chemotherapy by targeting these RNA molecules. Accordingly, this review aims to clarify the substantial roles of exosomal ncRNAs in GBM drug resistance and involved mechanisms.

Biogenesis, cellular effects, and biomarker value of circHIPK3

Competing endogenous RNAs (ceRNAs) can indirectly regulate gene expression by competitively binding to microRNA(miRNA) through miRNA response elements (MREs) to affect miRNA-induced gene regulation, which is of great biological significance. Among them, circular RNA (circRNA) has become a hotspot due to its highest binding capacity. A specific circRNA discussed in this review, circHIPK3, has been studied for its biological characteristics, function, cellular effects and its relationship with tumors and various diseases. Here, we review the recent researches about circHIPK3 in detail and aim to elucidate accurate conclusions from them. These circHIPK3-miRNAs-mRNA pathways will further advance the application of circHIPK3 in diseases development, early diagnosis and gene targeting therapy.

Competing Endogenous RNA Networks in Glioma

Gliomas are the most common and malignant primary brain tumors. Various hallmarks of glioma, including sustained proliferation, migration, invasion, heterogeneity, radio- and chemo-resistance, contribute to the dismal prognosis of patients with high-grade glioma. Dysregulation of cancer driver genes is a leading cause for these glioma hallmarks. In recent years, a new mechanism of post-transcriptional gene regulation was proposed, i.e., "competing endogenous RNA (ceRNA)." Long non-coding RNAs, circular RNAs, and transcribed pseudogenes act as ceRNAs to regulate the expression of related genes by sponging the shared microRNAs. Moreover, coding RNA can also exert a regulatory role, independent of its protein coding function, through the ceRNA mechanism. In the latest glioma research, various studies have reported that dysregulation of certain ceRNA regulatory networks (ceRNETs) accounts for the abnormal expression of cancer driver genes and the establishment of glioma hallmarks. These achievements open up new avenues to better understand the hidden aspects of gliomas and provide new biomarkers and potential efficient targets for glioma treatment. In this review, we summarize the existing knowledge about the concept and logic of ceRNET and highlight the emerging roles of some recently found ceRNETs in glioma progression.

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.

Circ_0110805 Knockdown Enhances Cisplatin Sensitivity and Inhibits Gastric Cancer Progression by miR-299-3p/ENDOPDI Axis

Background

Gastric cancer is a prevalent primary stomach tumor. Cisplatin is frequently used to treat gastric cancer. However, the resistance of cisplatin in gastric cancer often occurs, which brings a heavy burden to gastric cancer treatment.

Methods

In this study, we revealed a novel underlying mechanism about cisplatin-resistant effect in gastric cancer. A Cell Counting Kit-8 (CCK-8) cell viability assay and a xenograft model were performed to evaluate the function of circRNA in the cisplatin resistance of gastric cancer.

Results

Compared with control groups, we observed that circ_0110805 was highly expressed, the mRNA and protein expression levels of ENDOPDI were dramatically upregulated, and the expression of miR-299-3p was significantly downregulated in gastric cancer cells, cisplatin-resistant gastric cancer tissues or cells. Functionally, circ_0110805 knockdown improved cisplatin sensitivity, induced cell apoptosis, whereas repressed cell viability, migration and invasion in AGS/DDP and HGC-27/DDP cells, which was reversed by miR-299-3p inhibitor. Additionally, ENDOPDI overexpression hindered the effects of miR-299-3p on cisplatin sensitivity and gastric cancer progression. Circ_0110805 knockdown enhanced cisplatin sensitivity in vivo. Mechanistically, circ_0110805 acted as a sponge of miR-299-3p and its targeted ENDOPDI.

Conclusion

We showed that circ_0110805 knockdown increased the sensitivity of gastric cancer to cisplatin, which also repressed gastric cancer progression by sponging miR-299-3p to downregulate ENDOPDI expression. It might provide a new insight for future studying cisplatin-resistant gastric cancer.