A novel circular RNA, circ-ATAD1, contributes to gastric cancer cell progression by targeting miR-140-3p/YY1/PCIF1 signaling axis

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

circ-ATAD1 as Competing Endogenous RNA for miR-191-5p Forces Non-small Cell Lung Cancer Progression

The association of circular RNAs (circRNAs) with non-small cell lung cancer (NSCLC) has been recognized extensively. In view of this, our study particularly surveyed the underlying mechanism of circ-ATAD1 in the disease. First, an analysis of the clinical expression of circ-ATPase family AAA domain containing 1 (ATAD1) was performed, followed by further evaluation of the relationship between circ-ATAD1 expression and prognosis. Then, A549 cells were treated with single transfection or combined transfection with the plasmid vectors that interfere with circ-ATAD1 or miR-191-5p. circ-ATAD1 and miR-191-5p levels were detected by reverse transcription quantitative polymerase chain reaction to verify the transfection success. Then, cell proliferation was checked by cell count kit-8 and clonal formation test. Cell apoptosis was analyzed by flow cytometry. Cell migration and invasion were examined by wound healing assay and Transwell. Finally, the targeting of miR-191-5p to circ-ATAD1 or Forkhead Box K1 (FOXK1) was verified by bioinformation website starBase analysis and dual-luciferase reporter assay. circ-ATAD1 was expressed abundantly in tumor tissues of NSCLC patients and had a predictive value in poor prognosis. circ-ATAD1 underexpression or miR-191-5p overexpression could obstruct A549 cells to behave aggressively, while circ-ATAD1 upregulation or miR-191-5p depletion resulted in the promotion of aggressiveness of A549 cells. Interestingly, circ-ATAD1 could decoy miR-191-5p. miR-191-5p negatively regulated FOXK1 expression, and downregulating miR-191-5p or upregulating FOXK1 rescued circ-ATAD1 downregulation-mediated influences on NSCLC cells. circ-ATAD1 accelerates NSCLC progression by absorbing miR-191-5p to upregulate FOXK1 expression.

A comprehensive analysis of minimally differentially methylated regions common to pediatric and adult solid tumors

Cancer is the second most common cause of death in children aged 1-14 years in the United States, with 11,000 new cases and 1200 deaths annually. Pediatric cancers typically have lower mutational burden compared to adult-onset cancers, however, the epigenomes in pediatric cancer are highly altered, with widespread DNA methylation changes. The rarity of pediatric cancers poses a significant challenge to developing cancer-type specific biomarkers for diagnosis, prognosis, or treatment monitoring. In the current study, we explored the potential of a DNA methylation profile common across various pediatric cancers. To do this, we conducted whole genome bisulfite sequencing (WGBS) on 31 recurrent pediatric tumor tissues, 13 normal tissues, and 20 plasma cell-free (cf)DNA samples, representing 11 different pediatric cancer types. We defined minimal focal regions that were differentially methylated across samples in the multiple cancer types which we termed minimally differentially methylated regions (mDMRs). These methylation changes were also observed in 506 pediatric and 5691 adult cancer samples accessed from publicly available databases, and in 44 pediatric cancer samples we analyzed using a targeted hybridization probe capture assay. Finally, we found that these methylation changes were detectable in cfDNA and could serve as potential cfDNA methylation biomarkers for early detection or minimal residual disease.

PCIF1, the only methyltransferase of N6,2-O-dimethyladenosine

N6-methyladenosine(m6A), is the most abundant post-transcriptional modification of mRNA in biology. When the first nucleotide after the m7G cap is adenosine, it is methylated at the N6 position to form N6,2-O-dimethyladenosine (m6Am). m6Am is a reversible modification located at the first transcribed nucleotide, which is present in about 30% of cellular mRNAs, thus m6Am can have a significant impact on gene expression in the transcriptome. Phosphorylated CTD interaction factor 1(PCIF1), the unique and specific methyltransferase of m6Am, has been shown to affect mRNA stability, transcription, and translation. Several studies have shown that PCIF1 is clearly associated with tumor, viral, and endocrine diseases. Moreover, PCIF1 may be related to the tumor microenvironment, immune cell typing, and programmed cell death protein 1(PD-1) drug resistance. Here, we summarize the mechanism of PCIF1 involvement in mRNA modifications, and outline m6Am modifications and diseases in which PCIF1 is involved. We also summarized the role of PCIF1 in immune and immune checkpoint blockade(ICB) treatment, and predicted the possibility of PCIF1 as a biomarker and therapeutic target.

Genetic Deletion of Thorase Causes Purkinje Cell Loss and Impaired Motor Coordination Behavior

Thorase belongs to the AAA+ ATPase family, which plays a critical role in maintaining cellular homeostasis. Our previous work reported that Thorase was highly expressed in brain tissue, especially in the cerebellum. However, the roles of Thorase in the cerebellum have still not been characterized. In this study, we generated conditional knockout mice (cKO) with Thorase deletion in Purkinje cells. Thorase cKO mice exhibited cerebellar degenerative diseases-like behavior and significant impairment in motor coordination. Thorase deletion resulted in more Purkinje neuron apoptosis, leading to Purkinje cell loss in the cerebellum of Thorase cKO mice. We also found enhanced expression of the inflammatory protein ASC, IL-1β, IL-6 and TNF-α in the Thorase cKO cerebellum, which contributed to the pathogenesis of cerebellar degenerative disease. Our findings provide a better understanding of the role of Thorase in the cerebellum, which is a theoretical basis for Thorase as a therapeutic drug target for neurodegenerative diseases.

circUBAP2 inhibits cisplatin resistance in gastric cancer via miR-300/KAT6B axis

Circular RNAs play an important role in regulating cisplatin (CDDP) resistance in gastric cancer (GC). The aim of this study was to examine the role and downstream regulation mechanisms of circUBAP2 in CDDP resistance of GC. The expression of circUBAP2 in GC and its correlation with the prognosis of GC patients were analyzed using qRT-PCR and the Kaplan-Meier plotter database. The effects of circUBAP2 on cell viability and apoptosis were investigated by Cell Counting Kit 8 assay and flow cytometry. The expressions of drug-resistance-related proteins, P-gp and MRP1, were detected by Western blot. The interaction between circUBAP2 and miR-300 was confirmed using RNA pulldown and immunoprecipitation assays. The correlation between miR-300 and KAT6B was assessed using dual-luciferase reporter assay and TCGA database. CircUBAP2 was downregulated in GC tissues and cell lines, and correlated with the poor prognosis of GC. In addition, circUBAP2 enhanced apoptosis but inhibited cell viability and the CDDP resistance of GC cells in vitro . CircUBAP2 acted as a sponge of microRNA-300 (miR-300) and was negatively correlated with miR-300. Moreover, the upregulation of miR-300 partially removed the effects of circUBAP2 on cell viability, apoptosis and CDDP resistance in GC cells. MiR-300 directly targeted to lysine acetyltransferase 6B (KAT6B), and KAT6B overexpression showed an inhibitory effect on cell viability and CDDP resistance of GC cells. Our data suggested that the circUBAP2/miR-300/KAT6B axis was involved in the inhibition of CDDP resistance in GC, which might provide a novel focus for potential GC therapy.

CircRNA circ-ATAD1 suppresses miR-618 maturation to participate in colorectal cancer

BACKGROUND

CircRNA circ-ATAD1 has been characterized as an oncogenic circRNA in gastric cancer, while its role in colorectal cancer (CRC) is unknown. This study was carried out to explore the role of circ-ATAD1 in CRC.

METHODS

Paired CRC and adjacent non-tumor tissue samples collected from 64 CRC patients were subjected to RNA extractions and RT-qPCRs to analyze the expression of circ-ATAD1, premature miR-618, and mature miR-618 in CRC. The effects of circ-ATAD1 overexpression on miR-618 maturation were analyzed by transfecting circ-ATAD1 expression vector into CRC cells, followed by determining the expression of premature miR-618 and mature miR-618 using RT-qPCR. The subcellular location of circ-ATAD1 was analyzed by nuclear fractionation assay, and the interaction between circ-ATAD1 and premature miR-618 was analyzed by RNA pull-down assay. The roles of circ-ATAD1, premature miR-618, and mature miR-618 in regulating CRC cell proliferation were explored by CCK-8 assay.

RESULTS

Circ-ATAD1 was upregulated in CRC and predicted poor survival. In addition, circ-ATAD1 was inversely correlated with mature miR-618 but not premature miR-618. In CRC cells, circ-ATAD1 overexpression decreased the level of mature miR-618 but not premature miR-618. Circ-ATAD1 was detected in both the nucleus and cytoplasm. A direct interaction between circ-ATAD1 and miR-618 was observed. Moreover, circ-ATAD1 overexpression reduced the inhibitory effects of miR-618 overexpression on cell proliferation.

CONCLUSION

Circ-ATAD1 is overexpressed in CRC and may suppress miR-618 maturation to participate in CRC.

A Pan-Cancer Analysis of the Oncogenic and Immunogenic Role of m6Am Methyltransferase PCIF1

Background

Phosphorylated CTD-interacting factor 1 (PCIF1) is identified as the only known methyltransferase of N6,2′-O-dimethyladenosine (m6Am) in mRNA. However, its oncogenic and immunogenic role in cancer research is at an initial stage.

Methods

Herein, we carried out a pan-cancer analysis of PCIF1, with a series of datasets (e.g., TIMER2.0, GEPIA2, cBioPortal).

Results

PCIF1 expression was higher in most cancers than normal tissues and was discrepant across pathological stages. Highly expressed PCIF1 was positively correlated with overall survival (OS) or disease-free survival (DFS) of some tumors. PCIF1 expression had a positive correlation with CD4⁺ T-cell infiltration in kidney renal clear cell carcinoma (KIRC), CD8⁺ T cells, macrophages, and B cells in thyroid carcinoma (THCA), and immune checkpoint genes (ICGs) in LIHC but a negative correlation with CD4⁺ T cells, neutrophils, myeloid dendritic cells, and ICGs in THCA. It also affected tumor mutational burden (TMB) and microsatellite instability (MSI) of most tumors.

Conclusion

PCIF1 expression was correlated with cancer prognosis and immune infiltration, suggesting it to be a potential target for cancer therapy.

Circ-ATAD1 is overexpressed in osteosarcoma (OS) and suppresses the maturation of miR-154-5p to increase cell invasion and migration

Background

Circ-ATAD1 plays an oncogenic role in gastric cancer. However, its roles in other cancers are unclear. We aimed to analyze the role of circ-ATAD1 in osteosarcoma (OS).

Methods

The expression levels of circ-ATAD1, mature miR-154-5p, and premature miR-154-5p in paired OS and non-tumor tissues from 56 OS patients were determined using RT-qPCR. Nuclear fractionation assay was performed to analyze the subcellular location of circ-ATAD1. The interaction between circ-ATAD1 and premature miR-154-5p was analyzed using RNA pull-down assay. The role of circ-ATAD1 in regulating miR-154-5p maturation was analyzed using RT-qPCR in cells with overexpression. Transwell assays were performed to analyze the roles of circ-ATAD1 and miR-154-5p in regulating OS cell invasion and migration.

Results

Circ-ATAD1 was overexpressed in OS compared to non-tumor tissues and was detected in the nuclei of OS cells. Mature miR-154-5p, but not premature miR-154-5p, was downregulated in OS tissues compared to non-tumor tissues and was inversely correlated with circ-ATAD1. In OS cells, circ-ATAD1 overexpression decreased the expression of mature miR-154-5p, but not premature miR-154-5p. Transwell assay analysis showed that circ-ATAD1 overexpression increased cell invasion and migration, and mature miR-154-5p overexpression suppressed these cell behaviors. In addition, circ-ATAD1 overexpression reduced the effects of mature miR-154-5p overexpression on cell behaviors.

Conclusions

Circ-ATAD1 is overexpressed in OS and suppresses miR-154-5p maturation to increase cell invasion and migration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02809-4.

Circ_0004104 Accelerates the Progression of Gastric Cancer by Regulating the miR-539-3p/RNF2 Axis

BACKGROUND

Circular RNA (circRNA) has been shown to be closely associated with cancer progression, including gastric cancer (GC). However, the function of circ_0004104 in GC progression has not been clarified.

AIMS

The purpose of this study was to explore the role of circ_0004104 in GC progression.

METHODS

The expression levels of circ_0004104, miR-539-3p, and ring finger protein 2 (RNF2) were assessed using quantitative real-time polymerase chain reaction. Cell proliferation was measured by 3-(4,5-dimethyl-2 thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, and cell migration and invasion were detected using transwell assay. The levels of glutamine, glutamate, and α-ketoglutarate were determined to evaluate the glutaminolysis of cells, and the protein levels of glutaminolysis-related markers and RNF2 were detected using western blot analysis. Furthermore, Dual-Luciferase Reporter Assay was employed to assess the interaction between miR-539-3p and circ_0004104 or RNF2. Animal experiments were carried out to evaluate the effect of circ_0004104 silencing on GC tumor growth in vivo.

RESULTS

Circ_0004104 was upregulated in GC, and its knockdown repressed the proliferation, metastasis, and glutaminolysis of GC cells in vitro and reduced GC tumor growth in vivo. Furthermore, we discovered that circ_0004104 could sponge miR-539-3p and miR-539-3p could target RNF2. The rescue experiments suggested that miR-539-3p inhibitor could reverse the suppressive effect of circ_0004104 silencing on GC progression, and RNF2 overexpression also reversed the inhibition effect of miR-539-3p mimic on GC progression.

CONCLUSION

Circ_0004104 accelerated GC progression via regulating the miR-539-3p/RNF2 axis, indicating that circ_0004104 might be a potential therapeutic target for GC.

circSLC30A7 Inhibits Hepatocellular Carcinoma Cell Proliferation via the miR-767-5p/FBXW7/NOTCH1 Axis

Circular RNAs, noncoding RNAs, have attracted much attention in various human tumor research fields. They regulate the development of various human cancers via microRNA sponges. This study aimed to assess the molecular mechanism of circSLC30A7 in hepatocellular carcinoma (HCC). In our study, we identified that circSLC30A7 was significantly downregulated in HCC cell lines and tissues. Furthermore, gain and loss function experiments were conducted to elucidate the biological functions of circSLC30A7 in HCC cell lines. Mechanistically, circSLC30A7 sponged miR-767-5p, inhibiting the expression of its downstream protein, FBXW7. In summary, this study revealed that circSLC30A7 is an essential tumor suppressor that inhibits HCC tumorigenesis through the miR-767-5p/FBXW7/NOTCH1 axis. Taken together, circSLC30A7 reduces HCC malignancy and can be a biomarker for HCC management.

miR-140-3p is involved in the occurrence and metastasis of gastric cancer by regulating the stability of FAM83B

Background

Gastric cancer (GC) is a malignant tumor and microRNAs (miRNAs) are closely connected to GC development. The purpose of this study is to investigate the effect of miR-140-3p on the occurrence and metastasis of GC.

Methods

We detected miR-140-3p expression in GC cells and tissues. The correlation between miR-140-3p and prognosis and clinicopathological features in GC was analyzed. The role of miR-140-3p in GC cell migration, invasion, and proliferation was analyzed. The model of tumor transplantation and metastasis in nude mice was established, and the effect of miR-140-3p on the development and metastasis of GC was assessed. The relation between miR-140-3p and SNHG12 and the relations among HuR, SNHG12, and FAM83B were analyzed.

Results

miR-140-3p was poorly expressed in GC. GC patients with low miR-140-3p expression had a poor prognosis and unfavorable clinicopathologic features. Overexpression of miR-140-3p inhibited GC cell migration, invasion, and proliferation, and inhibited the development and metastasis of GC. miR-140-3p directly bound to SNHG12 in GC tissues and downregulated SNHG12 expression. SNHG12 overexpression induced HuR nuclear transportation. HuR can bind to FAM83B and up-regulate the mRNA level of FAM83B. Overexpression of SNHG12 or FAM83B reduced the inhibition of overexpression of miR-140-3p on GC.

Conclusion

miR-140-3p directly bound to SNHG12 in GC and down-regulated the expression of SNHG12, reduced the binding of SNHG12 and HuR, thus inhibiting the nuclear transportation of HuR and the binding of HuR and FAM83B, and reducing the transcription of FAM83B, and finally inhibiting the growth and metastasis of GC.

Circular RNA ATAD1 is upregulated in acute myeloid leukemia and promotes cancer cell proliferation by downregulating miR-34b via promoter methylation

A previous study has reported the oncogenic role of circular RNA (circ)-ATAD1 in gastric cancer. The aim of the present study was to investigate the role of circ-ATAD1 in acute myeloid leukemia (AML). Bone marrow mononuclear cells were collected from 60 patients with AML and 60 healthy controls, followed by RNA isolation and reverse transcription-quantitative PCR to assess the expression of circ-ATAD1 and microRNA (miR)-34b. A subcellular fractionation assay was used to determine the subcellular location of circ-ATAD1 in AML cells. Furthermore, circ-ATAD1 and miR-34b were overexpressed in AML cells to study crosstalk between the two molecules. The effect of circ-ATAD1 overexpression on miR-34b gene methylation was also analyzed by methylation-specific PCR, and the roles of circ-ATAD1 and miR-34b in the regulation of AML cell proliferation were analyzed by BrdU assay. circ-ATAD1 expression was found to be elevated, and inversely correlated with that of miR-34b, in patients with AML. Subcellular fractionation assays showed that circ-ATAD1 was specifically expressed in the nucleus. In addition, circ-ATAD1 overexpression in AML cells decreased miR-34b expression and increased miR-34b gene methylation. Moreover, AML cell proliferation was increased by circ-ATAD1 overexpression, but decreased by miR-34b overexpression, and the effect of circ-ATAD1 overexpression on AML cell proliferation was reduced by miR-34b overexpression. Together, these results indicate circ-ATAD1 as a nucleus-specific circRNA in AML, which promotes AML cell proliferation by downregulating miR-34b via methylation.

Contribution of circRNAs in gastric cancer

Gastric cancer (GC) is one of the most commonly diagnosed neoplasms in the world. A number of environmental and lifestyle factors, particularly chronic infection with Helicobacter pylori, have been found to partake in the pathogenesis of GC. The advent of high-throughput genome and transcriptome analysis has enhanced the knowledge about molecular mechanisms of the pathogenesis of GC. However, data regarding the expression of several circRNAs, such as circLMTK2, are not consistent. We explain the role of circRNAs in the development of GC. We searched databases for the newest publications using the terms gastric cancer and circRNA. Each circRNA alteration, downstream targets, its impacts on cancer cells, and the prognostic and diagnostic roles of these circRNAs have been discussed. Taken together, circRNAs can be putative biomarkers in GC and potential targets for the treatment of this cancer. Yet, this field is still in its infancy and needs further experiments for reaching the clinical application. As these transcripts are stable in circulation, they can be used in non-invasive methods of cancer detection and patients' follow-up.

Prognostic and clinicopathological importance of microRNA-140 expression in cancer patients: a meta-analysis

Background

MicroRNA-140 (miR-140) is one of the most widely investigated miRNAs in cell carcinogenesis and cancer development. Despite present proposals of employing miR-140 as a candidate biomarker for cancer prognosis, its effectiveness in predicting patient survival and clinicopathological outcome is still under debate.

Methods

A systematic search for English literature using online databases was performed with pre-established criteria. Odds ratios (ORs) or hazard ratios (HRs) with 95% confidence intervals (CIs) were collected to delineate the correlation between miR-140 levels and cancer patient prognosis.

Results

For this meta-analysis, we selected 12 papers for analysis, involving 1386 participants. Based on our analysis, high levels of miR-140 were strongly correlated with enhanced patient overall survival (OS) (HR = 0.728, 95% CI = 0.601-0.882, P = 0.001). In addition, we also observed that elevated miR-140 levels significantly led to better OS in patients with cancers in different parts of the body like digestive system (HR = 0.675, 95% CI = 0.538-0.848, P = 0.001), digestive tract (HR = 0.709, 95% CI = 0.565-0.889, P = 0.003), and head and neck (HR = 0.603, 95% CI = 0.456-0.797, P < 0.001). Additionally, we verified that the low miR-140 levels was related to advanced TNM stage (OR = 0.420, 95% CI = 0.299-0.590, P < 0.001), worse histologic grade (OR = 0.410, 95% CI = 0.261-0.643, P < 0.001), and positive lymph node metastasis status (OR = 0.341, 95% CI = 0.144-0.807, P = 0.014).

Conclusions

Taken together, our results suggest that elevated miR-140 levels can be employed as a favorable biomarker for cancer patient prognosis. This information can greatly benefit in the formation of an individualized therapeutic plan for the treatment of cancer patients.

CircRNA circ-ATAD1 is downregulated in endometrial cancer and suppresses cell invasion and migration by downregulating miR-10a through methylation

It has been reported that circ-ATAD1 promotes the development of gastric cancer. This study was carried out to analyze the role of circ-ATAD1 in endometrial cancer (EC). EC and paired non-tumor tissues from EC patients (n = 60) were subjected to the isolation of total RNA and RT-qPCR to analyze the expression of circ-ATAD1 and miR-10a. Correlations between circ-ATAD1 and miR-10a were analyzed by Pearson's correlation coefficient. The effects of circ-ATAD1 overexpression on miR-10a expression and methylation were analyzed by RT-qPCR and methylation-specific PCR (MSP). The roles of circ-ATAD1 and miR-10a in regulating EC cell invasion and migration were analyzed by Transwell assays. We found that circ-ATAD1 was downregulated in EC, while miR-10a was upregulated in EC. An inverse correlation between circ-ATAD1 and miR-10a was observed across EC samples. In EC cells, circ-ATAD1 overexpression decreased miR-10a expression and increased miR-10a gene methylation. Transwell assay analysis showed that circ-ATAD1 overexpression totally reversed the enhancing effects of miR-10a on EC cell invasion and migration. Circ-ATAD1 is downregulated in EC and may suppress EC cell invasion and migration by downregulating miR-10a through methylation.

CircRNA circ-ATAD1 Is Upregulated in Cervical Squamous Cell Carcinoma and Regulates Cell Proliferation and Apoptosis by Suppressing the Maturation of miR-218

The oncogenic function of circ-ATAD1 has been characterized in gastric cancer, while its role in cervical squamous cell carcinoma (CSCC) is unclear. This study explored the role of circ-ATAD1 in CSCC. To evaluate the differential expression of circ-ATAD1, mature miR-218, and premature miR-218 in CSCC, a total of 62 CSCC patients were subjected to biopsies to collect CSCC and paired normal tissues. Gene expression levels were quantified by RT-qPCRs. Nuclear fractionation assay was performed to analyze the subcellular location of circ-ATAD1. CSCC cells were used to perform cell transfections to explore the crosstalk between circ-ATAD1 and miR-218. The roles of circ-ATAD1 and miR-218 in CSCC cell behaviors were explored by BrdU assay, Transwell assay, cell apoptosis assay, and cell stemness assay. CSCC tissues exhibited upregulated expression of circ-ATAD1, which was localized to both nucleus and cytoplasm. Mature miR-218 was downregulated in CSCC tissues and was inversely correlated with circ-ATAD1, while premature miR-218 was not differentially expressed in CSCC. Upregulation of circ-ATAD1 in CSCC cells decreased the expression levels of mature miR-218, but not that of premature miR-218. In addition, overexpression of circ-ATAD1 increased cell proliferation and decreased cell apoptosis, while overexpression of miR-218 decreased cell proliferation and increased cell apoptosis, and it also attenuated the effects of overexpression of circ-ATAD1 on cell proliferation. However, CSCC cell invasion, migration, and stemness were not affected by circ-ATAD1 and miR-218. Circ-ATAD1 is upregulated in CSCC and may regulate cell proliferation and apoptosis by suppressing the maturation of miR-218.

Circular RNAs emerge as important regulators with great potential for clinical application in gastric cancer

Gastric cancer (GC) is a common digestive malignancy with a high-ranking morbidity and mortality. Therefore, it is urgent to identify novel indicators and develop new strategies for clinical diagnosis and treatment of GC. As a type of noncoding RNA, circular RNAs (circRNAs) have received increased attention in GC during recent years. To more comprehensively understand current research progress on circRNAs in GC, in this review, we introduce basic knowledge of circRNAs, summarize abnormally expressed circRNAs and discuss their functions and regulatory molecular mechanisms in GC. Then, we review potential applications of circRNAs for GC diagnosis, prognosis and treatment. Finally, we conclude by highlighting major advancements of circRNAs in GC research, and we discuss existing challenges and possible future research directions of GC-associated circRNAs.

Circular RNAs: Emerging Role in Cancer Diagnostics and Therapeutics

Circular RNAs (circRNAs) are rapidly coming to the fore as major regulators of gene expression and cellular functions. They elicit their influence via a plethora of diverse molecular mechanisms. It is not surprising that aberrant circRNA expression is common in cancers and they have been implicated in multiple aspects of cancer pathophysiology such as apoptosis, invasion, migration, and proliferation. We summarize the emerging role of circRNAs as biomarkers and therapeutic targets in cancer.

Circular RNAs in gastrointestinal cancer: Current knowledge, biomarkers and targeted therapy (Review)

Circular RNAs (circRNAs) are a type of endogenous non‑coding RNAs that are connected at the 3' and 5' ends by exon or intron cyclization, which forms a covalently closed loop. They are stable, well conserved, exhibit specific expression in mammalian cells and can function as microRNA (miRNA or miR) sponges to regulate the target genes of miRNAs, which influences biological processes. Such as tumor proliferation, invasion, metastasis, apoptosis and tumor stage. circRNAs represent promising candidates for clinical diagnosis and treatment. In the present review, the biogenesis, classification and functions of circRNAs in tumors are briefly summarized and discussed. In addition, the participation of circRNAs in signal transduction pathways regulating gastrointestinal cancer cellular functions is highlighted.

RETRACTED ARTICLE: Circ_002117 binds to microRNA-370 and promotes endoplasmic reticulum stress-induced apoptosis in gastric cancer

BACKGROUND

Mounting evidence implicates circular RNAs (circRNAs) in various biological processes during cancer progression. Gastric cancer is a main cause of cancer-related deaths worldwide. Herein, we aimed at investigating whether circ_002117 mediates gastric cancer progression through endoplasmic reticulum (ER) stress.

METHODS

Bioinformatics analysis detected differentially expressed circRNAs and their target miRNA candidates, and RT-qPCR was performed to detect expression of circ_002117, microRNA (miRNA)-370 and HERPUD1 in gastric cancer tissues and cells. Gastric cancer cells were transfected with plasmids and their proliferative ability and apoptosis were detected with gain- and loss-of-function assay. The ER of treated cells was observed under a transmission electron microscope. Dual-luciferase reporter gene assay and RIP were performed to detect the interaction between HEPRUD1, miR-370 and circ_002117-treated cells were injected into mice to establish xenograft tumor model.

RESULTS

Circ_002117 and HEPRUD1 were poorly expressed whereas miR-370 was highly expressed in clinical cancer tissues and cells. Circ_002117 was indicated to target and suppress miR-370 expression, while HERPUD1 was directly targeted by miR-370. Circ_002117 overexpression or miR-370 deficiency promoted ER stress-induced apoptosis and decreased proliferation of gastric cancer cells, which was reversed by silencing of HEPRUD1. Circ_002117 overexpression or miR-370 depletion significantly suppressed gastric cancer tumorigenesis in vivo.

CONCLUSIONS

Taken altogether, circ_002117 facilitated ER stress-induced apoptosis in gastric cancer by upregulating HERPUD1 through miR-370 inhibition.

hsa_circ_0000520 influences herceptin resistance in gastric cancer cells through PI3K-Akt signaling pathway

Background

To investigate whether hsa_circ_0000520 affects Herceptin resistance in gastric cancer by regulating the PI3K‐AKT signaling.

Methods

The expression of hsa_circ_0000520 was detected by qRT‐PCR in gastric cancer tissues and cell lines. A Herceptin‐resistant gastric cancer cell was established. PcDNA and pcDNA‐hsa_circ_0000520 were transfected into NCI‐N87R cells and treated with Herceptin at a concentration of 10 μg/mL for 24 hours. MTT tested cell proliferation, and apoptosis was measured by flow cytometry. IGF‐1 treatment was used to activate PI3K‐Akt signaling. The expression levels of related proteins were detected.

Results

The expression of hsa_circ_0000520 was reduced in gastric cancer tissues and cell lines, and hsa_circ_0000520 in NCI‐N87R cells was significantly lower than that of NCI‐N87 cells. Compared with the CON group, the cell viability of the Herceptin group was significantly reduced, the apoptosis rate was significantly increased, the level of Bax protein was significantly increased, and the levels of Bcl‐2, p‐PI3K, and p‐Akt protein were significantly reduced. Compared with the Herceptin + pcDNA group, the cell viability of the Herceptin + hsa_circ_0000520 group was significantly reduced, the apoptosis rate was significantly increased, the level of Bax protein was significantly increased, and the levels of p‐PI3K and p‐Akt proteins were significantly reduced. After IGF‐1 treatment, the cell viability was significantly increased, the apoptosis rate was significantly reduced, the level of Bax protein was significantly reduced, and the level of Bcl‐2 protein was significantly increased.

Conclusion

Hsa_circ_0000520 overexpression may reverse the Herceptin resistance of gastric cancer cells by inhibiting the PI3K‐Akt signaling pathway.

Circular RNAs in Gastric Cancer: Potential Biomarkers and Therapeutic Targets

Circular RNAs (circRNAs), as a recently established group of endogenous noncoding RNAs, have been involved in the occurrence and development of different malignancies. Gastric cancer (GC) remains a globally significant contributor to death in cancer patients due to insufficient early diagnosis, limited treatment measures, and poor prognosis. An increasing number of studies have found that many circRNAs are dysregulated in GC and are closely associated with its tumorigenesis and metastasis. Thus, circRNAs have the potential to serve as diagnostic and prognostic biomarkers and even therapeutic targets. This review comprehensively summarizes the most recent findings on how circRNAs influence GC progression and their clinical value. In addition, we present several methological deficiencies in the studies and provide some promising ideas for future research.

Circular RNAs in gastric cancer: Biomarkers for early diagnosis

Circular RNAs (circRNAs) are highly conserved and stable closed-loop non-coding RNAs. They are involved in numerous biological functions, including regulating gene transcription or protein translation by interacting with proteins and regulating expression of microRNAs. The aberrant expression of circRNAs has been reported in many cancers, including gastric cancer. By regulating gene expression, circRNAs are able to affect the proliferation, invasion and metastasis of gastric cancer. The current review focused on the characteristics and biological functions of circRNAs, the carcinogenic potential and the possible implications of circRNAs on the diagnosis and treatment of gastric cancer. In conclusion, circRNAs may serve as potential biomarkers for diagnosis, as well as therapeutic targets.