Identification of the tumor‑suppressive function of circular RNA FOXO3 in non‑small cell lung cancer through sponging miR‑155

Role of circRNAs in regulating cell death in cancer: a comprehensive review

Despite multiple diagnostic and therapeutic advances, including surgery, radiation therapy, and chemotherapy, cancer preserved its spot as a global health concern. Prompt cancer diagnosis, treatment, and prognosis depend on the discovery of new biomarkers and therapeutic strategies. Circular RNAs (circRNAs) are considered as a stable, conserved, abundant, and varied group of RNA molecules that perform multiple roles such as gene regulation. There is evidence that circRNAs interact with RNA-binding proteins, especially capturing miRNAs. An extensive amount of research has presented the substantial contribution of circRNAs in various types of cancer. To fully understand the linkage between circRNAs and cancer growth as a consequence of various cell death processes, including autophagy, ferroptosis, and apoptosis, more research is necessary. The expression of circRNAs could be controlled to limit the occurrence and growth of cancer, providing a more encouraging method of cancer treatment. Consequently, it is critical to understand how circRNAs affect various forms of cancer cell death and evaluate whether circRNAs could be used as targets to induce tumor death and increase the efficacy of chemotherapy. The current study aims to review and comprehend the effects that circular RNAs exert on cell apoptosis, autophagy, and ferroptosis in cancer to investigate potential cancer treatment targets.

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.

LGCDA: Predicting CircRNA-Disease Association Based on Fusion of Local and Global Features

CircRNA has been shown to be involved in the occurrence of many diseases. Several computational frameworks have been proposed to identify circRNA-disease associations. Despite the existing computational methods have obtained considerable successes, these methods still require to be improved as their performance may degrade due to the sparsity of the data and the problem of memory overflow. We develop a novel computational framework called LGCDA to predict circRNA-disease associations by fusing local and global features to solve the above mentioned problems. First, we construct closed local subgraphs by using k-hop closed subgraph and label the subgraphs to obtain rich graph pattern information. Then, the local features are extracted by using graph neural network (GNN). In addition, we fuse Gaussian interaction profile (GIP) kernel and cosine similarity to obtain global features. Finally, the score of circRNA-disease associations is predicted by using the multilayer perceptron (MLP) based on local and global features. We perform five-fold cross validation on five datasets for model evaluation and our model surpasses other advanced methods.

CircRNA as an Achilles heel of cancer: characterization, biomarker and therapeutic modalities

Circular RNAs (circRNAs) are a class of endogenous noncoding RNAs characterized by their lack of 5' caps and 3' poly(A) tails. These molecules have garnered substantial attention from the scientific community. A wide range of circRNA types has been found to be expressed in various tissues of the human body, exhibiting unique characteristics such as high abundance, remarkable stability, and tissue-specific expression patterns. These attributes, along with their detectability in liquid biopsy samples such as plasma, position circRNAs an ideal choice as cancer diagnostic and prognostic biomarkers. Additionally, several studies have reported that the functions of circRNAs are associated with tumor proliferation, metastasis, and drug resistance. They achieve this through various mechanisms, including modulation of parental gene expression, regulation of gene transcription, acting as microRNA (miRNA) sponges, and encoding functional proteins. In recent years, a large number of studies have focused on synthesizing circRNAs in vitro and delivering them to tumor tissue to exert its effects in inhibit tumor progression. Herein, we briefly discuss the biogenesis, characteristics, functions, and detection of circRNAs, emphasizing their clinical potential as biomarkers for cancer diagnosis and prognosis. We also provide an overview the recent techniques for synthesizing circRNAs and delivery strategies, and outline the application of engineered circRNAs in clinical cancer therapy.

Bioinformatics analysis and experimental verification of TIGD1 in non-small cell lung cancer

Introduction

Non-small cell lung cancer (NSCLC) is a prevalent respiratory system tumor. Triggered transposable element derivative 1 (TIGD1) exhibits significant overexpression in various tumor cells and tissues, suggesting its involvement in cancer progression.

Methods

Clinical data and gene expression profiles of lung adenocarcinoma were collected from TCGA, UCSC XENA, and GEO databases. Computational techniques and empirical studies were employed to analyze the role of TIGD1 in NSCLC. Cellular experiments were conducted using the H1299 cell line, including RNA interference, cell viability assays, quantitative PCR, wound-healing assays, western blotting, and plate clone formation assays.

Results

Bioinformatics analysis revealed TIGD1's potential as a biomarker for diagnosing and predicting lung cancer. It also indicated promise as a target for immune-related therapy and targeted drug therapy. Cellular studies confirmed TIGD1's involvement in cancer cell proliferation, invasion, and migration. Furthermore, an association between TIGD1 and the PI3K/AKT signaling pathway was suggested.

Discussion

The findings suggest that TIGD1 plays a vital role in NSCLC progression, making it a potential diagnostic biomarker and therapeutic target. The association with the PI3K/AKT signaling pathway provides insights into the underlying molecular mechanisms. Integrating computational analysis with empirical studies enhances our understanding of TIGD1's significance in NSCLC and opens avenues for further research into targeted therapies.

Role of circ-FOXO3 and miR-23a in radiosensitivity of breast cancer

Identifying the radiosensitivity of cells before radiotherapy (RT) in breast cancer (BC) patients allows appropriate switching between routinely used treatment regimens and reduces adverse side effects in exposed patients. In this study, blood was collected from 60 women diagnosed with Invasive Ductal Carcinoma (IDC) BC and 20 healthy women. To predict cellular radiosensitivity, a standard G2-chromosomal assay was performed. From these 60 samples, 20 BC patients were found to be radiosensitive based on the G2 assay. Therefore, molecular studies were finally performed on two equal groups (20 samples each) of patients with and without cellular radiosensitivity. QPCR was performed to examine the expression levels of circ-FOXO3 and miR-23a in peripheral blood mononuclear cells (PBMCs) and RNA sensitivity and specificity were determined by plotting Receiver Operating Characteristic (ROC) curves. Binary logistic regression was performed to identify RNA involvement in BC and cellular radiosensitivity (CR) in BC patients. Meanwhile, qPCR was used to compare differential RNA expression in the radiosensitive MCF-7 and radioresistant MDA-MB-231 cell lines. An annexin -V FITC/PI binding assay was used to measure cell apoptosis 24 and 48 h after 2 Gy, 4 Gy, and 8 Gy gamma-irradiation. Results indicated that circ-FOXO3 was downregulated and miR-23a was upregulated in BC patients. RNA expression levels were directly associated with CR. Cell line results showed that circ-FOXO3 overexpression induced apoptosis in the MCF-7 cell line and miR-23a overexpression inhibited apoptosis in the MDA-MB-231 cell line. Evaluation of the ROC curves revealed that both RNAs had acceptable specificity and sensitivity in predicting CR in BC patients. Binary logistic regression showed that both RNAs were also successful in predicting breast cancer. Although only circ-FOXO3 has been shown to predict CR in BC patients, circ-FOXO3 may function as a tumor suppressor and miR-23a may function as oncomiR in BC. Circ-FOXO3 and miR-23a may be promising potential biomarkers for BC prediction. Furthermore, Circ-FOXO3 could be a potential biomarker for predicting CR in BC patients.

The emerging role of MicroRNA-182 in tumorigenesis; a promising therapeutic target

A wide range of studies have indicated that microRNAs (miRNAs), a type of small single-stranded regulatory RNAs, are dysregulated in a different variety of human cancers. Therefore, they are expected to play important roles in tumorigenesis by functioning as oncogenic (oncomiRs) or tumor-suppressive miRNAs. Subsequently, their potential as diagnostic and therapeutic targets for malignancies has attracted attention in recent years. In particular, studies have revealed the aberrant expression of miR-182 through tumorigenesis and its important roles in various aspects of malignancies, including proliferation, metastasis, and chemoresistance. Accumulating reports have illustrated that miR-182, as a dual-role regulator, directly or indirectly regulates the expression of a wide range of genes and modulates the activity of various signaling pathways involved in tumor progression, such as JAK / STAT3, Wnt / β-catenin, TGF-β, and P13K / AKT. Therefore, considering the high therapeutic and diagnostic potential of miR-182, this review aims to point out the effects of miR-182 dysregulation on the signaling pathways involved in tumorigenesis.

Understanding the roles and regulation patterns of circRNA on its host gene in tumorigenesis and tumor progression

Circular RNAs (circRNAs) are a novel type of endogenous non-coding RNAs, which are covalently closed loop structures formed by precursor mRNAs (pre-mRNAs) through back-splicing. CircRNAs are abnormally expressed in many tumors, and play critical roles in a variety of tumors as oncogenes or tumor suppressor genes by sponging miRNAs, regulating alternative splicing and transcription, cis-regulating host genes, interacting with RNA binding proteins (RBPs) or encoding polypeptides. Among them, the regulation of circRNAs on their corresponding host genes is a critical way for circRNAs to exit their functions. Accumulating evidence suggests that circRNAs are able to regulate the expression of host genes at the transcriptional level, post-transcriptional level, translational level, post-translational level, or by encoding polypeptides. Therefore, this paper mainly summarized the roles and association of circRNAs and their corresponding host genes in tumorigenesis and tumor progression, generalized the circRNAs that function synergistically or antagonistically with their host genes, and elaborated the mechanisms of mutual regulation between circRNAs and their host genes. More importantly, this review provides specific references for revealing the potential application of circRNAs combined with their host genes in tumor diagnosis, treatment and prognosis.

Circular RNA FOXO3 regulates endometrial carcinoma progression through the microRNA-29a-3p/HDAC4 axis

Previous studies determined that circular RNA FOXO3 (circ_FOXO3) plays a critical role in tumorigenesis. The definite molecular mechanism of cir_FOXO3 in endometrial carcinoma (EC), nevertheless, had not been fully explored. Circ_FOXO3 expression was determined using quantitative real-time polymerase chain reaction in human EC tissues and cell lines, whereas small interfering RNAs were used to specifically silence circ_FOXO3 expression in cultured EC cells. The cell counting kit-8 assay was employed to determine the effect of ectopic circ_FOXO3 expression on cell viability. Cell proliferation and apoptosis were evaluated by flow cytometry. Further, migration and invasion of EC cells were characterized using the Transwell assay. The interaction between microRNA (miR)-29a-3p and circ_FOXO3/histone deacetylase 4 (HDAC4) was validated using dual luciferase reporter assay. Additionally, qRT-PCR and WB were employed to determine HDAC4 levels. We found that circ_FOXO3 was highly expressed in EC cells and tissues. Moreover, suppressing circ_FOXO3 expression abrogated EC by regulating cell proliferation, apoptosis, migration, and invasion. Furthermore, circ_FOXO3 could act as a sponge for miR-29a-3p, and inhibition of miR-29a-3p expression reversed the effects of circ_FOXO3 suppression on EC progression. Overexpression of miR-29a-3p inhibited EC cell growth, migration, and invasion through the regulation of HDAC4, as it is a target of miR-29a-3p. In conclusion, circ_FOXO3 promotes EC progression by sponging miR-29a-3p and upregulating HDAC4, making it a promising therapeutic target in EC.

CircRNA has_circ_0017109 promotes lung tumor progression via activation of Wnt/β-catenin signaling due to modulating miR-671-5p/FZD4 axis

INTRODUCTION

Accumulating evidence highlights the critical roles of circular RNAs (circRNAs) in the malignant progression of cancers. In this study, we investigated the expression pattern of a newly identified circRNA (hsa_circ_0017109) in non-small cell lung cancer (NSCLC), and examined its downstream molecular targets.

METHODS

Quantitative real-time PCR (qRT-PCR) and Western blotting (WB) were conducted to quantify gene and protein expression. In vitro functional assays such as colony formation assay, cell counting kit-8 (CCK-8) and flow cytometry were used to study cell proliferation and apoptosis. RNA pull-down assay, luciferase reporter assay and RNA immunoprecipitation were performed to validate molecular interaction. Mouse xenograft model of NSCLC cells was used to assess the role of circ_0017109 in tumorigenesis.

RESULTS

Circ_0017109 was upregulated in NSCLC tumor samples and cells. Silencing circ_0017109 impaired cell proliferation and promoted apoptosis in NSCLC cells, and circ_0017109 knockdown suppressed in vivo tumorigenesis of NSCLC cells in mouse xenograft model. MiR-671-5p was identified as a target of circ_0017109, and circ_0017109 negatively impacted on miR-671-5p expression. MiR-671-5p downregulated FZD4 and dampened the activity of Wnt/β-catenin signaling pathway. Circ_0017109 modulated FZD4 expression by suppressing miR-671-5p activity.

CONCLUSIONS

Elevated circ_0017109 expression promotes tumor progression of NSCLC by modulating miR-671-5p/FZD4/β-catenin axis.

The Role of miRNA-182 and FOXO3 Expression in Breast Cancer

OBJECTIVE

evaluating the role of FOXO3 mRNA and mi RNA 182-5P expression levels in BC patients.

METHOD

25 Samples of breast cancer and paired samples of non-cancerous tissues from the same resected breast were obtained from 25 female patients suffering from breast cancer and examined and analyzed by real time PCR to detect the expression levels of FOXO3 mRNA and mi RNA 182-5P. Patients' data were collected from patients medical records.

RESULTS

Foxo3 m RNA expression was down regulated in BC tissues (1.37± 1.96) as compared to control group (23.62 ± 54.39) and decreased FOXO3 expression was associated with larger tumor size (p= 0.046), late histopathological grading (p= 0.002), late TNM staging (<0.001) and increased miR-182 expression (p= 0.025). We found that expression level of miR-182 was significantly higher among breast cancer group (1.10±1.15) as compared to the control group (0.58±0.96 ) with p value = 0.017. We noted a significant increased expression associated with larger tumor size (p= 0.002), late histopathological grading (p= 0.008), late TNM staging (p= 0.002) and decreased FOXO3 expression (p= 0.025). A significant negative correlation between miR-182 and FOXO3 mRNA fold expression with r = - 0.447, and a p value of 0.025, this could be attributed to miRNA targeting FOXO gene.

COCLUSION

Down regulation of FOXO3 and up regulation of miR-182 expression was associated with advanced breast cancer. The negative correlation between miR-182 and FOXO3 mRNA could be attributed to miRNA targeting FOXO gene.

The Emerging Roles and Clinical Potential of circSMARCA5 in Cancer

Circular RNAs (circRNAs) are a type of endogenous non-coding RNA and a critical epigenetic regulation way that have a closed-loop structure and are highly stable, conserved, and tissue-specific, and they play an important role in the development of many diseases, including tumors, neurological diseases, and cardiovascular diseases. CircSMARCA5 is a circRNA formed by its parental gene SMARCA5 via back splicing which is dysregulated in expression in a variety of tumors and is involved in tumor development with dual functions as an oncogene or tumor suppressor. It not only serves as a competing endogenous RNA (ceRNA) by binding to various miRNAs, but it also interacts with RNA binding protein (RBP), regulating downstream gene expression; it also aids in DNA damage repair by regulating the transcription and expression of its parental gene. This review systematically summarized the expression and characteristics, dual biological functions, and molecular regulatory mechanisms of circSMARCA5 involved in carcinogenesis and tumor progression as well as the potential applications in early diagnosis and gene targeting therapy in tumors.

Long Noncoding RNAs and Circular RNAs Regulate AKT and Its Effectors to Control Cell Functions of Cancer Cells

AKT serine-threonine kinase (AKT) and its effectors are essential for maintaining cell proliferation, apoptosis, autophagy, endoplasmic reticulum (ER) stress, mitochondrial morphogenesis (fission/fusion), ferroptosis, necroptosis, DNA damage response (damage and repair), senescence, and migration of cancer cells. Several lncRNAs and circRNAs also regulate the expression of these functions by numerous pathways. However, the impact on cell functions by lncRNAs and circRNAs regulating AKT and its effectors is poorly understood. This review provides comprehensive information about the relationship of lncRNAs and circRNAs with AKT on the cell functions of cancer cells. the roles of several lncRNAs and circRNAs acting on AKT effectors, such as FOXO, mTORC1/2, S6K1/2, 4EBP1, SREBP, and HIF are explored. To further validate the relationship between AKT, AKT effectors, lncRNAs, and circRNAs, more predicted AKT- and AKT effector-targeting lncRNAs and circRNAs were retrieved from the LncTarD and circBase databases. Consistently, using an in-depth literature survey, these AKT- and AKT effector-targeting database lncRNAs and circRNAs were related to cell functions. Therefore, some lncRNAs and circRNAs can regulate several cell functions through modulating AKT and AKT effectors. This review provides insights into a comprehensive network of AKT and AKT effectors connecting to lncRNAs and circRNAs in the regulation of cancer cell functions.

Effects of circFOXO3 on the Proliferation and Invasion of Liver Cancer Cells by Regulating PI3K/Akt Pathway

Objective

Hepatocellular carcinoma is a malignant disease occurring in the liver and is one of the main causes of death in cancer patients. Tumor cells are the main components of tumors and have a strong proliferative capacity. They are easily transferred to other parts of the body and can produce harmful substances that destroy the normal organ structure and endanger human life and health. In this study, we investigate the effect of circFOXO3 on the proliferation and invasion of hepatocellular carcinoma cells and its possible mechanism.

Methods

Human hepatocellular carcinoma cells BEL-7404, Hep G2, Hep 3B2.1–7, HuH-7, Li-7, and human normal hepatocytes HHL-5 were selected, and the expression level of circFOXO3 in the cell lines was determined by qRT-PCR. The cell line with low circFOXO3 expression level (HuH-7 cells) was used for follow-up experiments. HuH-7 liver cancer cells were divided into the control group (normal cultured), circFOXO3-NC group (transfected with circFOXO3 negative control), circFOXO3 mimic group (transfected with circFOXO3 mimic), PI3K activator group (20 μmol/L PI3K activator 740Y-P), and circFOXO3 mimic + PI3K activator group (transfected with circFOXO3 mimic + treated with PI3K activator 740Y-P). The qRT-PCR method was used to determine the expression level of circFOXO3 in HuH-7 liver cancer cells in each group, WB was used to detect the expression of apoptosis, invasion, and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway related proteins in HuH-7 liver cancer cells in each group, the CCK-8 method was used to determine the viability of HuH-7 liver cancer cells in each group, flow cytometry was used to determine the apoptotic ability of HuH-7 liver cancer cells in each group, the transwell chamber experiment was used to determine the invasion ability of HuH-7 liver cancer cells in each group, and the scratch test was used to determine the migration ability of HuH-7 liver cancer cells in each group.

Results

circFOXO3 showed low expression in liver cancer cells; compared with the control group, the circFOXO3 expression and apoptosis rate of HuH-7 liver cancer cells in the circFOXO3 mimic group were significantly increased (P < 0.05) and the PI3K/Akt pathway-related protein expression, cell viability, invasion, and migration abilities were significantly reduced (P < 0.05); the apoptosis rate of HuH-7 liver cancer cells in the PI3K activator group was significantly reduced (P < 0.05) and the PI3K/Akt pathway related protein expression, cell viability, invasion and migration abilities were significantly increased (P < 0.05). Compared with the circFOXO3 mimic group, the apoptosis rate of HuH-7 liver cancer cells in the circFOXO3 mimic + PI3K activator group was significantly reduced (P < 0.05) and the PI3K/Akt pathway-related protein expression, cell viability, invasion and migration abilities were significantly increased (P < 0.05).

Conclusion

Highly expressed circFOXO3 can inhibit the proliferation and invasion of HuH-7 liver cancer cells, which may be achieved by inhibiting the PI3K/Akt pathway.

Mechanistic insights into the role of FOXO in diabetic retinopathy

Diabetes mellitus (DM), a metabolic disorder characterized by insulin-deficiency or insulin-resistant conditions. The foremost microvascular complication of diabetes is diabetic retinopathy (DR). This is a multifaceted ailment mainly caused by the enduring adverse effects of hyperglycaemia. Inflammation, oxidative stress, and advanced glycation products (AGES) are part and parcel of DR pathogenesis. In regulating many cellular and biological processes, the family of fork-head transcription factors plays a key role. The current review highlights that FOXO is a requisite regulator of pathways intricate in diabetic retinopathy on account of its effect on microvascular cells inflammatory and apoptotic gene expression, and FOXO also has the foremost province in regulating cell cycle, proliferation, apoptosis, and metabolism. Blockage of insulin turns into an exaggerated level of glucose in the bloodstream and can upshot into the exaggerated triggering of FOXO1, which can ultimately uplift the production of several factors of apoptosis and inflammation, such as TNF-α, NF-kB, and various others, as well as reactive oxygen species, which can also come up with diabetic retinopathy. The current review also focuses on various therapies which can be used in the future, like SIRT1 signalling, resveratrol, retinal VEGF, etc., which can be used to suppress FOXO over activation and can prevent the progression of diabetic complications viz. diabetic retinopathy.

miR-155: An Important Role in Inflammation Response

MicroRNAs (miRNAs) are a class of small, mature, noncoding RNA that lead to posttranscriptional gene silencing to regulate gene expression. miRNAs are instrumental in biological processes such as cell development, cell differentiation, cell proliferation, and cell apoptosis. The miRNA-mediated gene silencing is an important part of the regulation of gene expression in many kinds of diseases. miR-155, one of the best-characterized miRNAs, has been found to be closely related to physiological and pathological processes. What is more, miR-155 can be used as a potential therapeutic target for inflammatory diseases. We analyze the articles about miR-155 for nearly five years, review the advanced study on the function of miR-155 in different inflammatory cells like T cells, B cells, DCs, and macrophages, and then summarize the biological functions of miR-155 in different inflammatory cells. The widespread involvement of miR-155 in human diseases has led to a novel therapeutic approach between Chinese and Western medicine.

Accentuating CircRNA-miRNA-Transcription Factors Axis: A Conundrum in Cancer Research

Circular RNAs (circRNAs) are the newly uncovered class of non-coding RNAs being cognized as profound regulators of gene expression in developmental and disease biology. These are the covalently closed RNAs synthesized when the pre-mRNA transcripts undergo a back-splicing event. In recent years, circRNAs are gaining special attention in the scientific world and are no longer considered as "splicing noise" but rather structurally stable molecules having multiple biological functions including acting as miRNA sponges, protein decoys/scaffolds, and regulators of transcription and translation. Further, emerging evidence suggests that circRNAs are also differentially expressed in multiple cancers where they play oncogenic roles. In addition, circRNAs in association with miRNAs change the expression patterns of multiple transcription factors (TFs), which play important roles in cancer. Thus, the circRNA-miRNA-TFs axis is implicated in the progression or suppression of various cancer types and plays a role in cell proliferation, invasion, and metastasis. In this review article, we provide an outline of the biogenesis, localization, and functions of circRNAs specifically in cancer. Also, we highlight the regulatory function of the circRNA-miRNA-TFs axis in the progression or suppression of cancer and the targeting of this axis as a potential therapeutic approach for cancer management. We anticipate that our review will contribute to expanding the knowledge of the research community about this recent and rapidly growing field of circRNAs for further thorough investigation which will surely help in the management of deadly disease cancer.

circRNA LDLRAD3 Enhances the Malignant Behaviors of NSCLC Cells via the miR-20a-5p-SLC7A5 Axis Activating the mTORC1 Signaling Pathway

Circular RNA LDLRAD3 behaved as an oncogene in several malignancies, but its effects in NSCLC and the involvement of downstream molecules and activation of signaling pathways had not been fully reported. We planned to explore how LDLRAD3 facilitated the malignancy of NSCLC. QRT-PCR was performed to evaluate the expression levels of LDLRAD3, miR-20a-5p, and SLC7A5 in NSCLC tissues and cells. si-LDLRAD3 was transfected to A549 and H1299 cells to knock down intrinsic LDLRAD3 to determine its oncogenic roles. CCK-8 assay and transwell assay were executed to assess cell proliferative, migrative, and invasive abilities. Dual-luciferase reporter (DLR) assay was manipulated to verify the ENCORI-predicted relationships between LDLRAD3 and miR-20a-5p and between miR-20a-5p and SLC7A5. Western blot, immunofluorescent assay, and immunohistochemistry were applied to explore the expression levels of SLC7A5, and the levels of mTORC1 pathway-related proteins were evaluated using western blot. Rescue experiments were conducted by transfecting si-LDLRAD3, miR-20a-5p inhibitor, and si-SLC7A5 to explore the influence of the LDLRAD3-miR-20a-5p-SLC7A5 axis on the malignant behaviors of NSCLC cells. The expression levels of LDLRAD3 and SLC7A5 were boosted, whereas miR-20a-5p was impeded in NSCLC tissues and cell lines. Knockdown of LDLRAD3 weakened the proliferation, migration, and invasion of A549 and H1299 cells. LDLRAD3 was verified to sponge miR-20a-5p and miR-20a-5p targeted SLC7A5. LDLRAD3 activated the mTORC1 singling pathway via the miR-20a-5p-SLC7A5 axis to strengthen the malignant properties of A549 and H1299 cells. We concluded that LDLRAD3 exerted oncogenic effects via the miR-20a-5p-SLC7A5 axis to activate the mTORC1 signaling pathway in NSCLC. Our findings enlightened that LDLRAD3 could become a potential therapeutic target in the treatment and management of NSCLC.

Knockdown of hsa_circ_0000729 Inhibits the Tumorigenesis of Non-Small Cell Lung Cancer Through Mediation of miR-1281/FOXO3 Axis

Background

Non-small cell lung cancer (NSCLC) is a subtype of lung cancer which seriously threatens the health of people. Circular RNAs (CircRNAs) are endogenous RNAs which have stable closed structure; they are known to be involved in tumorigenesis of NSCLC. Meanwhile, hsa_circ_0000729 was reported to be upregulated in NSCLC. Nevertheless, the function of hsa_circ_0000729 in NSCLC remains unclear.

Methods

Western blot and RT-qPCR were performed to investigate protein and mRNA levels, respectively. CCK-8 assay was performed to test the cell viability and cell death was investigated by flow cytometry. NSCLC cell pyroptosis was observed by electron microscope. In addition, the migration and invasion of NSCLC cells were detected by wound healing and transwell assay. The relation among hsa_circ_0000729, miR-1281 and FOXO3 was explored by dual luciferase reporter assay and RNA pull-down.

Results

Hsa_circ_0000729 was found to be upregulated in NSCLC cells, and hsa_circ_0000729 knockdown obviously suppressed the proliferation of NSCLC cells through inducing pyroptosis. In addition, silencing of hsa_circ_0000729 notably inhibited the invasion and migration of NSCLC cells. Meanwhile, hsa_circ_0000729 could bind with miR-1281, and FOXO3 was directly targeted by miR-1281. Moreover, the anti-tumor effect of hsa_circ_0000729 siRNAs on NSCLC was markedly reversed by miR-1281 antagomir. Furthermore, silencing of hsa_circ_0000729 inhibited the tumor growth of NSCLC in vivo.

Conclusion

Knockdown of hsa_circ_0000729 inhibits the tumorigenesis of NSCLC through mediation of miR-1281/FOXO3 axis. Thus, hsa_circ_0000729 might be served as a crucial mediator in NSCLC.

Circular RNA FOXO3 accelerates glycolysis and improves cisplatin sensitivity in lung cancer cells via the miR-543/Foxo3 axis

Non-small cell lung cancer (NSCLC) is the most common cause of cancer-associated mortality worldwide. Our previous study revealed that circular RNA (circRNA)-FOXO3 is highly expressed in lung cancer and inhibits cell proliferation. However, to the best of our knowledge, at present, no study has focused on the specific mechanism of circRNA-FOXO3 in drug resistance. Therefore, the present study aimed to provide novel perspectives on the role of circRNA-FOXO3 in cisplatin (DDP) resistance in NSCLC. A Cell Counting Kit-8 assay was used to determine the viability of cells overexpressed with circRNA-FOXO3 and under DDP treatment. Glycolysis was analyzed by measuring glucose consumption and lactate production. The interaction of circRNA-FOXO3, microRNA 543 (miR-543) and Foxo3 was confirmed using a dual-luciferase reporter assay. It was revealed that circRNA-FOXO3 improved cell sensitivity to DDP and repressed glycolysis in DDP-sensitive and DDP-resistant NSCLC cells. Bioinformatics analysis, luciferase reporter assays, quantitative PCR and RNA pull-down assays were employed to verify the binding of circRNA-FOXO3 to miR-543. Functionally, inhibition of miR-543 could sensitize NSCLC cells to DDP, and overexpression of miR-543 at least partially abolished the circRNA-FOXO3-induced decrease in chemoresistance. Furthermore, it was revealed that Foxo3 was a direct target of miR-543. Notably, the inhibitory action of miR-543 silencing on DDP resistance and glycolysis was reversed by overexpression of Foxo3 in DDP-sensitive and DDP-resistant NSCLC cells. In conclusion, the present study demonstrated that circRNA-FOXO3 promoted DDP sensitivity in NSCLC cells by regulating the miR-543/Foxo3 axis-mediated glycolysis balance. The present findings may provide novel perspectives for the treatment of patients with NSCLC resistant to DDP.

Circular RNA Foxo3 enhances progression of ovarian carcinoma cells

Background: Ovarian carcinoma (OC) is the deadliest gynecologic malignancy in females worldwide. Circular RNA Foxo3 (Foxo3) plays essential roles in various cancers. However, the detailed function of Foxo3 in OC remains unclear. This study aimed to investigate the role of Foxo3 in OC and the underlying molecular mechanism.

Methods: The abundance of Foxo3 was detected in OC cell lines by qPCR. Lentivirus transduction, CCK-8, wound healing assays, transwell migration and invasion assays, luciferase reporter assay, western blotting, fluorescence in situ hybridization (FISH), transmission electron microscopy, nanoparticle tracking analysis, and bioinformatics analysis were performed to investigate the underlying mechanism.

Results: The results demonstrated that Foxo3 was significantly upregulated in OC cell lines. Overexpression and knockdown of Foxo3 promoted and inhibited the proliferation, migration, and invasion of OC cells, respectively. Foxo3 could bind to miR-422a to negatively regulate miR-422a expression. Also, proteolipid protein 2 (PLP2) was a targeting gene of miR-422a. Additionally, Foxo3 was highly expressed in exosomes derived from OC cells. Furthermore, Foxo3 could be shuttled to OC cells by exosomes and promoted OC progression.

Conclusions: Foxo3 promoted OC progression through exosome-mediated intercellular interaction to target miR-422a/PLP2 axis. Foxo3 may serve as a potential biomarker for OC.

Circular RNA _0015278 inhibits the progression of non-small cell lung cancer through regulating the microRNA 1278/SOCS6 gene axis

Background

Non-small cell lung cancer (NSCLC) is one of the most lethal malignancies worldwide. Deepening understanding of the pathogenesis of NSCLC is quite important for its treatment. Circular (circ) RNA_0015278 has been found to be downregulated in NSCLC, but its role in NSCLC and the underlying regulatory mechanism is unknown.

Methods

Circ_0015278, microRNA (miR)-1278 and SOCS6 were analyzed with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) or western blot. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) staining were used to evaluate cell proliferation. The colony forming capacity and invasion of NSCLC cells were assessed with colony formation and transwell assays, respectively. The interaction among circ_0015278, miR-1278, and SOCS6 was evaluated using luciferase, receptor interacting protein (RIP), and RNA-pull down assays. Cell apoptosis was analyzed using flow cytometry. A subcutaneous NSCLC xenograft mouse model was established for evaluating circ_0015278-mediated effects on the growth of NSCLC in vivo.

Results

Circ_0015278 was downregulated in NSCLC tissues and cells, and its reduced expression indicated poor prognosis. Overexpression of circ_0015278 restrained the proliferation, colony formation, invasion, and epithelial-mesenchymal transition (EMT) of NSCLC cells and induced NSCLC cell apoptosis. Moreover, overexpression of circ_0015278 inhibited the growth of NSCLC in vivo. Mechanically, circ_0015278 acted as an miR-1278 sponge to reduce its quantity, and miR-1278 targeted SOCS6 to inhibit its expression in NSCLC cells. Circ_0015278 promoted SOCS6 expression by sponging miR-1,278 in NSCLC cells. Overexpression of circ_0015278 attenuated the malignant phenotypes of NSCLC through sponging miR-1278 and consequently promoting SOCS6 expression.

Conclusions

We demonstrated for the first time that circ_0015278 attenuated the progression of NSCLC via targeting the miR-1278/SOCS6 axis, which provides potential diagnostic biomarkers and therapeutic targets.

Biogenesis, Functions, and Role of CircRNAs in Lung Cancer

CircRNAs, a class of endogenous non-coding RNAs with closed-loop structures, have attracted increasing attention because of their good stability, high specificity of tissue expression, long half-life, and highly conserved sequence. CircRNAs have multiple biological functions, including miRNA sponge, transcription regulator, protein translation, interaction with protein, RNA maturation, and so on. These functions indicate the important role of circRNAs in tumorigenesis and malignant progression and their potential as potent diagnostic biomarkers and therapeutic molecules. In recent years, an increasing body of evidence suggests that circRNAs play a crucial role in proliferation, migration, invasion, and apoptosis of lung cancer cells. Therefore, circRNAs have gradually become a research focus in the diagnosis and treatment of lung cancer patients. This review summarizes the classification, biogenesis, and function of circRNAs, and discusses the role of circRNAs in the diagnosis, prognosis, and treatment of lung cancer patients.

CircRNAs and their regulatory roles in cancers

Circular RNAs (circRNAs), a novel type of non-coding RNAs (ncRNAs), have a covalently closed circular structure resulting from pre-mRNA back splicing via spliceosome and ribozymes. They can be classified differently in accordance with different criteria. As circRNAs are abundant, conserved, and stable, they can be used as diagnostic markers in various diseases and targets to develop new therapies. There are various functions of circRNAs, including sponge for miR/proteins, role of scaffolds, templates for translation, and regulators of mRNA translation and stability. Without m7G cap and poly-A tail, circRNAs can still be degraded in several ways, including RNase L, Ago-dependent, and Ago-independent degradation. Increasing evidence indicates that circRNAs can be modified by N-6 methylation (m6A) in many aspects such as biogenesis, nuclear export, translation, and degradation. In addition, they have been proved to play a regulatory role in the progression of various cancers. Recently, methods of detecting circRNAs with high sensitivity and specificity have also been reported. This review presents a detailed overview of circRNAs regarding biogenesis, biomarker, functions, degradation, and dynamic modification as well as their regulatory roles in various cancers. It’s particularly summarized in detail in the biogenesis of circRNAs, regulation of circRNAs by m6A modification and mechanisms by which circRNAs affect tumor progression respectively. Moreover, existing circRNA detection methods and their characteristics are also mentioned.

Circular RNAs in Lung Cancer: Recent Advances and Future Perspectives

Globally, lung cancer is the most commonly diagnosed cancer and carries with it the greatest mortality rate, with 5-year survival rates varying from 4–17% depending on stage and geographical differences. For decades, researchers have studied disease mechanisms, occurrence rates and disease development, however, the mechanisms underlying disease progression are not yet fully elucidated, thus an increased understanding of disease pathogenesis is key to developing new strategies towards specific disease diagnoses and targeted treatments. Circular RNAs (circRNAs) are a class of non-coding RNA widely expressed in eukaryotic cells, and participate in various biological processes implicated in human disease. Recent studies have indicated that circRNAs both positively and negatively regulate lung cancer cell proliferation, migration, invasion and apoptosis. Additionally, circRNAs could be promising biomarkers and targets for lung cancer therapies. This review systematically highlights recent advances in circRNA regulatory roles in lung cancer, and sheds light on their use as potential biomarkers and treatment targets for this disease.

The Emerging Roles of circFOXO3 in Cancer

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs which are mainly formed by reverse splicing of precursor mRNAs. They are relatively stable and resistant to RNase R because of their covalently closed structure without 5' caps or 3' poly-adenylated tails. CircRNAs are widely expressed in eukaryotic cells and show tissue, timing, and disease specificity. Recent studies have found that circRNAs play an important role in many diseases. In particular, they affect the proliferation, invasion and prognosis of cancer by regulating gene expression. CircRNA Forkhead box O3 (circFOXO3) is a circRNA confirmed to be abnormally expressed in a variety of cancers, including prostate cancer, hepatocellular carcinoma, glioblastoma, bladder cancer, and breast cancer, etc. At present, the feature of circFOXO3 as a molecular sponge is widely studied to promote or inhibit the development of cancers. However, the diverse functions of circFOXO3 have not been fully understood. Hence, it is important to review the roles of circFOXO3 in cancers. This review has summarized and discussed the roles and molecular mechanism of circFOXO3 and its target genes in these cancers, which can help to enrich our understanding to the functions of circRNAs and carry out subsequent researches on circFOXO3.

Circular RNA Foxo3: A Promising Cancer-Associated Biomarker

Circular RNAs (circRNAs) are a class of novel non-coding RNAs (ncRNAs). Emerging evidence demonstrates that circRNAs play crucial roles in many biological processes by regulating linear RNA transcription, downstream gene expression and protein or peptide translation. Meanwhile, recent studies have suggested that circRNAs have the potential to be oncogenic or anti-oncogenic and play vital regulatory roles in the initiation and progression of tumors. Circular RNA Forkhead box O3 (circ-Foxo3, hsa_circ_0006404) is encoded by the human FOXO3 gene and is one of the most studied circular RNAs acting as a sponge for potential microRNAs (miRNAs) (Du et al., 2016). Previous studies have reported that circ-Foxo3 is involved in the development and tumorigenesis of a variety of cancers (bladder, gastric, acute lymphocytic leukemia, glioma, etc.). In this review, we summarize the current studies concerning circ-Foxo3 deregulation and the correlative mechanism in various human cancers. We also point out the potential clinical applications of this circRNA as a biomarker for cancer diagnosis and prognosis.

Insights Into circRNAs: Functional Roles in Lung Cancer Management and the Potential Mechanisms

Lung cancer is the most prevalent cancer globally. It is also the leading cause of cancer-related death because of the late diagnosis and the frequent resistance to therapeutics. Therefore, it is impending to identify novel biomarkers and effective therapeutic targets to improve the clinical outcomes. Identified as a new class of RNAs, circular RNAs (circRNAs) derive from pre-mRNA back splicing with considerable stability and conservation. Accumulating research reveal that circRNAs can function as microRNA (miRNA) sponges, regulators of gene transcription and alternative splicing, as well as interact with RNA-binding proteins (RBPs), or even be translated into proteins directly. Currently, a large body of circRNAs have been demonstrated differentially expressed in physiological and pathological processes including cancer. In lung cancer, circRNAs play multiple roles in carcinogenesis, development, and response to different therapies, indicating their potential as diagnostic and prognostic biomarkers as well as novel therapeutics. In this review, we summarize the multi-faceted functions of circRNAs in lung cancer and the underlying mechanisms, together with the possible future of these discoveries in clinical application.

Bufalin inhibits the malignant development of non-small cell lung cancer by mediating the circ_0046264/miR-522-3p axis

BACKGROUND

Bufalin is an active component of the traditional Chinese medicine "Chan Su" and is reported to play anti-tumor roles in cancer development, but its functional mechanism is largely unclear. This study intends to explore a potential action mode of bufalin in NSCLC.

MATERIALS AND METHODS

The malignant properties of NSCLC, including cell viability, proliferation, adhesion capacity, migration and invasion, were monitored by cell counting kit-8 (CCK-8), adhesion assay and transwell assay, respectively. The expression of circ_0046264 and miR-522-3p was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of proliferation- and migration-related markers was examined by western blot. The putative relationship between circ_0046264 and miR-522-3p was verified by dual-luciferase reporter assay, RIP assay and RNA pull-down assay. Animal experiments in nude mice were performed to investigate the role of bufalin in vivo.

RESULTS

Bufalin treatment inhibited cell viability, colony formation, cell adhesion capacity, migration and invasion in NSCLC cells. Bufalin facilitated the expression of circ_0046264, and circ_0046264 overexpression also inhibited NSCLC cell viability, colony formation, cell adhesion capacity, migration and invasion. Besides, circ_0046264 knockdown partially counteracted the effects of bufalin. Further, miR-522-3p was identified as a target of circ_0046264, and its deficiency reversed the effects of circ_0046264 knockdown to suppress malignant activities of NSCLC cells. In addition, bufalin restrained the tumor growth and development in vivo via enhancing the expression of circ_0046264.

CONCLUSION

Bufalin played an anti-tumor role in NSCLC by modulating the circ_0046264/miR-522-3p pathway, which might be a potential functional mechanism of bufalin in NSCLC.

Pathogenic mechanisms and the potential clinical value of circFoxo3 in cancers

Circular RNAs (circRNAs) are covalently closed circular structures that can function in various physiological and pathological processes by acting as microRNA (miRNA) sponges, RNA-binding protein (RBP) sponges, mRNA transcriptional regulators, and protein translational templates. circFoxo3 is one of the most studied circRNAs and is generated from the tumor suppressor gene Foxo3. Increasing studies have demonstrated the multiple functions of circFoxo3 in the pathogenesis of different cancer types. circFoxo3 plays important roles in cancer development mainly by binding to various miRNAs. The diagnostic potential of circFoxo3 has been revealed in several cancers. Some research results have been found to contradict the results of other studies, and this may be due to insufficient sample sizes and inconsistencies in the experimental and nomenclature methods. In this review, we systematically summarize current knowledge about the biogenesis and functions of circRNAs, elucidate the roles of circFoxo3 in different cancers, and explore the clinical applications of circFoxo3.

iCDA-CMG: identifying circRNA-disease associations by federating multi-similarity fusion and collective matrix completion

Circular RNAs (circRNAs) are a special class of non-coding RNAs with covalently closed-loop structures. Studies prove that circRNAs perform critical roles in various biological processes, and the aberrant expression of circRNAs is closely related to tumorigenesis. Therefore, identifying potential circRNA-disease associations is beneficial to understand the pathogenesis of complex diseases at the circRNA level and helps biomedical researchers and practitioners to discover diagnostic biomarkers accurately. However, it is tremendously laborious and time-consuming to discover disease-related circRNAs with conventional biological experiments. In this study, we develop an integrative framework, called iCDA-CMG, to predict potential associations between circRNAs and diseases. By incorporating multi-source prior knowledge, including known circRNA-disease associations, disease similarities and circRNA similarities, we adopt a collective matrix completion-based graph learning model to prioritize the most promising disease-related circRNAs for guiding laborious clinical trials. The results show that iCDA-CMG outperforms other state-of-the-art models in terms of cross-validation and independent prediction. Moreover, the case studies for several representative cancers suggest the effectiveness of iCDA-CMG in screening circRNA candidates for human diseases, which will contribute to elucidating the pathogenesis mechanisms and unveiling new opportunities for disease diagnosis and targeted therapy.

The Current View on the Helicase Activity of RNA Helicase A and Its Role in Gene Expression

RNA helicase A (RHA) is a DExH-box helicase that plays regulatory roles in a variety of cellular processes, including transcription, translation, RNA splicing, editing, transport, and processing, microRNA genesis and maintenance of genomic stability. It is involved in virus replication, oncogenesis, and innate immune response. RHA can unwind nucleic acid duplex by nucleoside triphosphate hydrolysis. The insight into the molecular mechanism of helicase activity is fundamental to understanding the role of RHA in the cell. Herein, we reviewed the current advances on the helicase activity of RHA and its relevance to gene expression, particularly, to the genesis of circular RNA.

Proliferation and Apoptosis of B-Cell Lymphoma Cells under Targeted Regulation of FOXO3 by miR-155

This study aimed to explore B-cell lymphoma cells' proliferation and apoptosis under targeted regulation of FOXO3 by miR-155. We analyzed the differences between B-cell lymphoma cells and B lymphocytes in expressions of miR-155 and FOXO3, explored the effects of miR-155 on proliferation and apoptosis of B-cell lymphoma cells, and relevant mechanisms, and also analyzed the relationship between expressions of miR-155 and FOXO3 in 42 patients with diffuse large B-cell lymphoma (DLBCL) and clinical characteristics of them. B-cell lymphoma cells showed a higher expression of miR-155 and a low expression of FOXO3 than B lymphocytes (both P<0.05). B-cell lymphoma cells transfected with miR-155-inhibitor showed significantly decreased expression of miR-155, significantly weakened cell proliferation ability, and increased cell apoptosis rate (all P<0.05), and they also showed upregulated expression of FOXO3 (P<0.05). Dual-luciferase reporter assay revealed that there were targeted binding sites between miR-155 and FOXO3. Compared with B-cell lymphoma cells transfected with miR-155-inhibitor alone, those with co-transfection showed lower expression of FOXO3, higher proliferation and lower cell apoptosis rate (all P<0.05). The expression of miR-155 in DLBCL tissues was higher than that in tumor-adjacent tissues (P<0.05), and the expressions of miR-155 and FOXO3 were closely related to the international prognostic index (IPI) and the 5-year prognosis and survival of the patients (P<0.05). miR-155 can promote the proliferation of B-cell lymphoma cells and suppress apoptosis of them by targeted inhibition of FOCXO3, and both over-expression of miR-155 and low expression of FOXO3 are related to poor prognosis of DLBCL patients.

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.

TERF1 downregulation promotes the migration and invasion of the PC3 prostate cancer cell line as a target of miR‑155

Telomeric repeat binding factor 1 (TERF1) has been identified as a tumor suppressor gene in numerous types of human cancer. However, the expression of TERF1 and its mechanism in prostate cancer (PCa) remains unclear. The present study aimed to explore the expression and functions of TERF1 in PCa. The UALCAN database was used to analyze the differential expression of TERF1 between normal prostate tissue and primary PCa tissue. Cell apoptosis was analyzed by Annexin V/propidium iodide staining, and wound healing and Transwell assays were used to detect the cell migration and invasion abilities, respectively. The cell viability was analyzed using an MTT assay. Reverse transcription-quantitative PCR and western blotting were used to analyze the mRNA and protein expression levels, respectively, of epithelial-mesenchymal transition (EMT) markers following TERF1 knockdown in the PC3 cell line. A dual luciferase reporter assay was used to verify the association between TERF1 and microRNA (miR)-155 predicted by bioinformatics analysis. Rescue experiments were performed to determine the role of the miR-155/TERF1 axis in regulating the cellular behaviors of PCa. The results demonstrated that the expression levels of TERF1 in the primary prostate tumors were significantly downregulated compared with in prostate normal tissue. TERF1 silencing was discovered to significantly promote cell viability, migration and invasion, while suppressing cell apoptosis. The impact of TERF1 on PC3 cells was suggested to occur through the EMT pathway. TERF1 was confirmed to be the direct target of miR-155. The overexpression of miR-155 promoted the viability, migration and invasion, while suppressing the apoptosis of the PC3 cell line, while the knockdown of miR-155 in PC3 cells achieved the opposite trends. In addition, TERF1 overexpression reversed the promotive effects of upregulated miR-155 expression levels on the migration and apoptosis of PC3 cells. On the contrary, the knockdown of TERF1 reversed the migration and apoptosis abilities of the downregulated miR-155 expression levels on the cellular behaviors of PC3 cells. In conclusion, TERF1, as a direct target of miR-155, was discovered to be significantly downregulated in PCa, which was suggested to promote the migration and invasion of PCa via the EMT pathway.

FOXO transcription factor family in cancer and metastasis

Forkhead box O (FOXO) transcription factors regulate diverse biological processes, affecting development, metabolism, stem cell maintenance and longevity. They have also been increasingly recognised as tumour suppressors through their ability to regulate genes essential for cell proliferation, cell death, senescence, angiogenesis, cell migration and metastasis. Mechanistically, FOXO proteins serve as key connection points to allow diverse proliferative, nutrient and stress signals to converge and integrate with distinct gene networks to control cell fate, metabolism and cancer development. In consequence, deregulation of FOXO expression and function can promote genetic disorders, metabolic diseases, deregulated ageing and cancer. Metastasis is the process by which cancer cells spread from the primary tumour often via the bloodstream or the lymphatic system and is the major cause of cancer death. The regulation and deregulation of FOXO transcription factors occur predominantly at the post-transcriptional and post-translational levels mediated by regulatory non-coding RNAs, their interactions with other protein partners and co-factors and a combination of post-translational modifications (PTMs), including phosphorylation, acetylation, methylation and ubiquitination. This review discusses the role and regulation of FOXO proteins in tumour initiation and progression, with a particular emphasis on cancer metastasis. An understanding of how signalling networks integrate with the FOXO transcription factors to modulate their developmental, metabolic and tumour-suppressive functions in normal tissues and in cancer will offer a new perspective on tumorigenesis and metastasis, and open up therapeutic opportunities for malignant diseases.

Detection of miR-155-5p and imaging lung cancer for early diagnosis: in vitro and in vivo study

Purpose

Currently, the routine screening program has insufficient capacity for the early diagnosis of lung cancer. Therefore, a type of chitosan-molecular beacon (CS-MB) probe was developed to recognize the miR-155-5p and image the lung cancer cells for the early diagnosis.

Methods

Based on the molecular beacon (MB) technology and nanotechnology, the CS-MB probe was synthesized self-assembly. There are four types of cells—three kinds of animal models and one type of histopathological sections of human lung cancer were utilized as models, including A549, SPC-A1, H446 lung cancer cells, tumor-initiating cells (TICs), subcutaneous and lung xenografts mice, and lox-stop-lox(LSL) K-ras G12D transgenic mice. The transgenic mice dynamically displayed the process from normal lung tissues to atypical hyperplasia, adenoma, carcinoma in situ, and adenocarcinoma. The different miR-155-5p expression levels in these cells and models were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The CS-MB probe was used to recognize the miR-155-5p and image the lung cancer cells by confocal microscopy in vitro and by living imaging system in vivo.

Results

The CS-MB probe could be used to recognize the miR-155-5p and image the lung cancer cells significantly in these cells and models. The fluorescence intensity trends detected by the CS-MB probe were similar to the expression levels trends of miR-155 tested by qRT-PCR. Moreover, the fluorescence intensity showed an increasing trend with the tumor progression in the transgenic mice model, and the occurrence and development of lung cancer were dynamically monitored by the differen fluorescence intensity. In addition, the miR-155-5p in human lung cancer tissues could be detected by the miR-155-5p MB.

Conclusion

Both in vivo and in vitro experiments demonstrated that the CS-MB probe could be utilized to recognize the miR-155-5p and image the lung cancer cells. It provided a novel experimental and theoretical basis for the early diagnosis of the disease. Also, the histopathological sections of human lung cancer research laid the foundation for subsequent preclinical studies. In addition, different MBs could be designed to detect other miRNAs for the early diagnosis of other tumors.

circRNA-miRNA-mRNA regulatory network in human lung cancer: an update

Circular RNAs, as hopeful diagnosis markers and therapeutic molecules, have been studied, probed and applied into several diseases, such as cardiovascular diseases, systemic lupus erythematosus, leukemia, pulmonary tuberculosis, and cancer especially. Recently, mounting evidence has supported that circRNAs play a key role in the tumorigenesis, progress, invasion and metastasis in lung cancer. Its special structure—3′–5′ covalent loop—allow it to execute several special functions in both normal eukaryotic cells and cancer cells. Our review summaries the latest studies on characteristics and biogenesis of circRNAs, and highlight the regulatory functions about miRNA sponge of lung-cancer-related circRNAs. In addition, the interaction of the circRNA-miRNA-mRNA regulatory network will also be elaborated in detail in this review. Therefore, this review can provide a new idea or strategy for further development and application in clinical setting in terms of early-diagnosis and better treatment.

Serum Circular FoxO3a Serves as a Novel Prognostic Biomarker in Squamous Cervical Cancer

Purpose

Circular RNAs (circRNAs) are novel type of noncoding RNAs that play important roles and serve as noninvasive biomarkers in various cancers. In the present study, we focused on circFoxO3a and aimed to investigate its prognostic value as a novel serum biomarker for squamous cervical cancer (SCC).

Patients and Methods

Our study included 103 SCC patients from Obstetrics and Gynecology Hospital of Fudan University. Expression levels of circFoxO3a in the serum of patients with SCC were examined by reverse transcription‑quantitative PCR (RT‑qPCR). The correlation between serum circFoxO3a expression and clinicopathologic factors was analyzed. The Kaplan–Meier method and multivariate Cox regression analysis were applied to evaluate the independent prognostic factors for SCC. A prognostic predictive nomogram was constructed using R software.

Results

Levels of serum circFoxO3a were decreased in SCC patients compared with controls. Low expression of circFoxO3a was correlated with deeper stromal invasion and positive lymph node metastasis. Moreover, SCC patients with lower expression of serum circFoxO3a showed poorer prognosis, including both overall survival (OS) and recurrence-free survival (RFS). Multivariate Cox analysis indicated low serum circFoxO3a levels to be an unfavorable prognostic factor for both OS and RFS, independent of positive lymph node metastasis. Notably, the predictive nomogram we established further confirmed that serum circFoxO3a is a useful tool for predicting survival in SCC.

Conclusion

Altogether, our findings demonstrated that serum circFoxO3a could serve as a potential novel noninvasive predictive prognostic biomarker and therapeutic target for SCC.

Dysfunction of regulatory T cells mediated by AKT-FOXO1 signaling pathway occurs during the development of psoriasis

Psoriasis is an immune-mediated skin disease with abnormal T cells. Regulatory T cells (Treg) are a kind of cell group with immunosuppressive effects. This study aimed to explore the role of Treg cells in the pathogenesis of psoriasis and its possible mechanism. Imiquimod induced psoriasis mice model was conducted. The skin lesions were evaluated according to the psoriasis area and severity index (PASI). Skin biopsies were taken for HE staining and immunohistochemical staining of IL-23, IL-17, IL-33 and TNF-α. CD4⁺CD25⁺ Treg cells were isolated. The proportions of Treg cells, cell proliferation, and immunosuppressive activity were analyzed by flow cytometry. The expression of AKT, Foxo1, pAKT, pFoxo1 protein, and the localization of Foxo1 protein in Treg cells were detected by western blot and immunofluorescence. The results showed that the psoriasis mice model was established successfully. There was no significant difference in the proportion of Treg cells between the two groups (P > 0.05). The cell proliferation abilities were decreased, and the immunosuppressive functions of Treg cells were weakened in the psoriatic group (P < 0.05). Western blot showed that pAKT and pFoxo1 levels of Treg cells were significantly increased in the psoriatic group (P < 0.05). Immunofluorescence showed that Foxo1 was mainly expressed in the nucleus of Treg cells in the control group, whereas expressed in the cytoplasm in the psoriasis group. Therefore, we concluded that the cell proliferation and immunosuppressive dysfunction of Treg cells mediated by AKT-FOXO1 signaling pathway may occurs during the development of psoriasis.

Hsa_circ_0012563 promotes migration and invasion of esophageal squamous cell carcinoma by regulating XRCC1/EMT pathway

BACKGROUND

Recent reports have indicated that circular RNA (circRNA) may regulate tumorigenesis development. However, the function of circRNAs in esophageal squamous cell carcinoma (ESCC) is unclear.

MATERIAL AND METHOD

The RT-qPCR assay was performed to detect hsa_circ_0012563 expression in ESCC tissues and cell lines. Then, the MTT assay, colony formation assay, flow cytometric assay, and cell migration and invasion assay were performed to examine the function of hsa_circ_0012563. In addition, the RT-PCR and Western blot were used to detect XRCC1 and epithelial-to-mesenchymal transition (EMT) related gene expression.

RESULTS

The RT-qPCR revealed that the hsa_circ_0012563 expression was remarkably upregulated in ESCC tissue and ESCC cell lines. Functionally, downregulation of hsa_circ_0012563 suppressed cell proliferation, migration, and invasion and promoted cell apoptosis. Mechanically, the knockdown of hsa_circ_0012563 inhibited XRCC1-mediated EMT pathway to suppress cell migration and invasion.

CONCLUSIONS

Therefore, these results reveal hsa_circ_0012563 is a critical oncogene and may be a novel biomarker in ESCC.

The role of noncoding RNAs in epithelial cancer

Regulatory noncoding RNAs (ncRNAs) are a class of RNAs transcribed by regions of the human genome that do not encode for proteins. The three main members of this class, named microRNA, long noncoding RNA, and circular RNA play a key role in the regulation of gene expression, eventually shaping critical cellular processes. Compelling experimental evidence shows that ncRNAs function either as tumor suppressors or oncogenes by participating in the regulation of one or several cancer hallmarks, including evading cell death, and their expression is frequently deregulated during cancer onset, progression, and dissemination. More recently, preclinical and clinical studies indicate that ncRNAs are potential biomarkers for monitoring cancer progression, relapse, and response to cancer therapy. Here, we will discuss the role of noncoding RNAs in regulating cancer cell death, focusing on those ncRNAs with a potential clinical relevance.

Circular RNA in Lung Cancer Research: Biogenesis, Functions, and Roles

Lung cancer is one of the most common and deadly malignancies worldwide, in spite of advances in targeted therapy in recent years. An effective strategy for lung cancer prevention remains a major problem. Advances in next-generation sequencing have helped in understanding the RNA and identifying novel circular RNAs (circRNAs) that may have a broad impact on the early diagnosis and treatment of lung cancer. The circRNAs, exhibiting spatiotemporal-specific expression, are stable and conserved and present diverse biological functions in the normal and diseased states, including cancer. In this review, we summarize the recent advances in elucidating the functional role of circRNAs in lung cancer pathogenesis and discuss their potential mechanisms.

Circ_0000003 promotes the proliferation and metastasis of non-small cell lung cancer cells via miR-338-3p/insulin receptor substrate 2

Background: Circular RNAs (circRNAs) play a pivotal regulatory role in a variety of tumors.Nevertheless, the detailed function of circ_0000003 in non-small cell lung cancer (NSCLC) and its regulatory mechanism remain elusive.Methods: RT-PCR was carried out to detect the expressions of circ_0000003, miR-338-3p and insulin receptor substrate 2 (IRS2)in NSCLC tissues. Besides, western blot was done to monitor IRS2 expression in NSCLC cells. The correlation between circ_0000003 and clinicopathologic characteristics of NSCLC patients was analyzed as well.CCK8 and BrdUassays were used to monitor cell proliferation; flow cytometry was used to detect apoptosis; and transwell assay was conducted to detect its migration and invasion.Moreover, dual luciferase reporter gene assay was done to verify the targeting relationship between circ_0000003 and miR-338-3p.Additionally, the effect of circ_0000003 on the growth of NSCLC cells in vivo was evaluated by tumorigenesis assay in nude mice.Results: The expression of circ_0000003 was significantly high in NSCLC tissues and cell lines, and its high expression level was notably correlated with lymph node metastasis andTNM staging.In vitro experiments showed that overexpression of circ_0000003 facilitated the proliferation, migration, invasion and inhibited the apoptosis of NSCLC cells, while the knockdown of circ_0000003 had the opposite effect.In vivo experiments revealed that knockdown of circ_0000003 impeded tumor growth and metastasis. Further, the underlying mechanism showed that circ_0000003 functioned as endogenous competitive RNA and directly targeted miR-338-3p to positively regulated IRS2 expression.Conclusion: Circ_0000003 promotes the proliferation and metastasis of NSCLC cells via modulating miR-338-3p/IRS2 axis.

Circ_MDM2_000139, Circ_ATF2_001418, Circ_CDC25C_002079, and Circ_BIRC6_001271 Are Involved in the Functions of XAV939 in Non-Small Cell Lung Cancer

Background

The small molecule inhibitor XAV939 could inhibit the proliferation and promote the apoptosis of non-small cell lung cancer (NSCLC) cells. This study was conducted to identify the key circular RNAs (circRNAs) and microRNAs (miRNAs) in XAV939-treated NSCLC cells.

Methods

After grouping, the NCL-H1299 cells in the treatment group were treated by 10 μM XAV939 for 12 h. RNA-sequencing was performed, and then the differentially expressed circRNAs (DE-circRNAs) were analyzed by the edgeR package. Using the clusterprofiler package, enrichment analysis for the hosting genes of the DE-circRNAs was performed. Using Cytoscape software, the miRNA-circRNA regulatory network was built for the disease-associated miRNAs and the DE-circRNAs. The DE-circRNAs that could translate into proteins were predicted using circBank database and IRESfinder tool. Finally, the transcription factor (TF)-circRNA regulatory network was built by Cytoscape software. In addition, A549 and HCC-827 cell treatment with XAV939 were used to verify the relative expression levels of key DE-circRNAs.

Results

There were 106 DE-circRNAs (including 61 upregulated circRNAs and 45 downregulated circRNAs) between treatment and control groups. Enrichment analysis for the hosting genes of the DE-circRNAs showed that ATF2 was enriched in the TNF signaling pathway. Disease association analysis indicated that 8 circRNAs (including circ_MDM2_000139, circ_ATF2_001418, circ_CDC25C_002079, and circ_BIRC6_001271) were correlated with NSCLC. In the miRNA-circRNA regulatory network, let-7 family members⟶circ_MDM2_000139, miR-16-5p/miR-134-5p⟶circ_ATF2_001418, miR-133b⟶circ_BIRC6_001271, and miR-221-3p/miR-222-3p⟶circ_CDC25C_002079 regulatory pairs were involved. A total of 47 DE-circRNAs could translate into proteins. Additionally, circ_MDM2_000139 was targeted by the TF POLR2A. The verification test showed that the relative expression levels of circ_MDM2_000139, circ_CDC25C_002079, circ_ATF2_001418, and circ_DICER1_000834 in A549 and HCC-827 cell treatment with XAV939 were downregulated comparing with the control.

Conclusions

Let-7 family members and POLR2A targeting circ_MDM2_000139, miR-16-5p/miR-134-5p targeting circ_ATF2_001418, miR-133b targeting circ_BIRC6_001271, and miR-221-3p/miR-222-3p targeting circ_CDC25C_002079 might be related to the mechanism in the treatment of NSCLC by XAV939.

Circular RNA circFOXO3 promotes prostate cancer progression through sponging miR-29a-3p

Circular RNA FOXO3 (CircFOXO3, also termed as Hsa_circ_0006404) is derived from exon 2 of forkhead box O3 (FOXO3) gene, and abnormal expression is shown in different diseases. However, whether circFOXO3 plays important roles in tumorigenesis and progression of prostate cancer (PCa) remains unclear. In this study, we found that circFOXO3 was up‐regulated in both PCa tissues and serum samples. Moreover, circFOXO3 was positively correlated with the Gleason score in PCa samples. CircFOXO3 was observed to be up‐regulated in Gleason score > 6 PCa samples compared with Gleason score = 6 PCa samples. Knock‐down circFOXO3 could remarkably inhibit PCa cell cycle, proliferation and promote cell apoptosis in vitro. Furthermore, we demonstrated circFOXO3 could act as miR‐29a‐3p sponge to up‐regulate SLC25A15 expression by bioinformatics analysis, dual‐luciferase reporter assays and biotinylated RNA pull‐down assays. SLC25A15 could reverse the tumour suppressing roles of knock‐down circFOXO3 in PCa. Of note, we found that miR‐29a‐3p was down‐regulated; however, SLC25A15 was overexpressed in PCa samples compared with normal tissues. In conclusion, circFOXO3 acts as a miR‐29a‐3p sponge to exhibit oncogenic activity that affects the cell cycle and cell apoptosis in PCa through transcriptional up‐regulation of SLC25A15. Our analysis suggests circFOXO3 could act as promising prostate cancer biomarkers.

Accuracy Evaluation of Circular RNA in Diagnosing Lung Cancer in a Chinese Population

Circular RNA (circRNA) is a class of recently discovered noncoding RNA. circRNAs can be used as a potent noninvasive biological marker of cancer owing to their varying expression levels among different cancers. This meta-analysis was performed to assess the accuracy of circRNAs in diagnosing lung cancer. A total of eight studies identified through searching the PubMed, Web of Science, Cochrane Library, and Embase from inception to March 20, 2019 were eligible for this meta-analysis. The pooled sensitivity, specificity, positive likelihood ratios, negative likelihood ratios, and diagnostic odds ratio were 0.77 (95% confidence interval (CI): 0.73-0.80; I 2 = 8.98%), 0.76 (95% CI: 0.69-0.82; I 2 = 63.12%), 3.17 (95% CI: 2.43-4.14; I 2 = 33.18%), 0.31 (95% CI: 0.26-0.37; I 2 = 20.36%), and 10.26 (95% CI: 6.87-15.31; I 2 = 97.18%), respectively. The area under the receiver operating characteristic curve was 0.78 (95% CI: 0.74-0.81). The study confirmed the use of circRNAs in diagnosing lung cancer in a Chinese population.