Suppression of Circular RNA Hsa_circ_0109320 Attenuates Non-Small Cell Lung Cancer Progression via MiR-595/E2F7 Axis

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.

The role of E2F2 in cancer progression and its value as a therapeutic target

The E2F family of transcription factors plays a crucial role in the regulation of cell cycle progression and cell proliferation. Accumulative evidence indicates that aberrant expression or activation of E2F2 is a common phenomenon in malignances. E2F2 has emerged as a key player in the development and progression of various types of tumors. A wealth of research has substantiated that E2F2 could contribute to the enhancement of tumor cell proliferation, angiogenesis, and invasiveness. Moreover, E2F2 exerts its influence on a myriad of cellular processes by engaging with a spectrum of auxiliary factors and downstream targets, including apoptosis and DNA repair. The dysregulation of E2F2 in the context of carcinogenesis may be attributable to a multitude of mechanisms, which encompass modifications in upstream regulatory elements or epigenetic alterations. This review explores the function of E2F2 in cancer progression and both established and emerging therapeutic strategies aiming at targeting this oncogenic pathway, while also providing a strong basis for further research on the biological function and clinical applications of E2F2.

The functional significance of circRNA/miRNA/mRNA interactions as a regulatory network in lung cancer biology

Lung cancer, the leading cause of cancer-related deaths, presents significant challenges to patients due to its poor prognosis. Recent research has increasingly implicated circular RNAs in the development and progression of lung cancer. These circular RNAs have been found to impact various aspects of tumor behavior, including proliferation, metastasis, cell cycle regulation, apoptosis, cancer stem cells, therapy response, and the tumor microenvironment. One of the key mechanisms by which circular RNAs exert their influence is through their ability to act as miRNA sponges, sequestering microRNAs and preventing them from targeting other RNA molecules. Accumulating evidence suggests that circular RNAs can function as competing endogenous RNAs, affecting the expression of target mRNAs by sequestering microRNAs. Dysregulation of competing endogenous RNAs networks involving circular RNAs, microRNAs, and mRNAs leads to the aberrant expression of oncogenes and tumor suppressors involved in lung cancer pathogenesis. Understanding the dynamic interplay and molecular mechanisms among circular RNAs, microRNAs, and mRNAs holds great promise for advancing early diagnosis, personalized therapeutic interventions, and improved patient outcomes in lung cancer. Therefore, this study aims to provide an in-depth exploration of the executive roles of circular RNAs/microRNAs/ mRNAs interactions in lung cancer pathogenesis and their potential utility for diagnosing lung cancer, predicting patient prognosis, and guiding targeted therapies. By offering a comprehensive overview of the dysregulation of the axes as driving factors in lung cancer, we aim to pave the way for their translation into clinical practice in the future.

Exosomal circular RNA: a signature for lung cancer progression

Membrane vesicles having a diameter of 30-150 nm are known as exosomes. Several cancer types secrete exosomes, which may contain proteins, circular RNAs (circRNAs), microRNAs, or DNA. CircRNAs are endogenous RNAs that do not code for proteins and can create continuous and covalently closed loops. In cancer pathogenesis, especially metastasis, exosomal circRNAs (exo-circRNAs) have a crucial role mainly due to the frequently aberrant expression levels within tumors. However, neither the activities nor the regulatory mechanisms of exo-circRNAs in advancing lung cancer (LC) are obvious. A better understanding of the regulation and network connections of exo-circRNAs will lead to better treatment for LCs. The main objective of the current review is to highlight the functions and mechanisms of exo-circRNAs in LC and assess the relationships between exo-circRNA dysregulation and LC progression. In addition, underline the possible therapeutic targets based on exo-circRNA modulating.

MicroRNA-631 deriving from bone marrow mesenchymal stem cell exosomes facilitates the malignant behavior of non-small cell lung cancer via modulating the E2F family of transcription factor 2/phosphatidylinositol 3-kinase/Akt signaling pathway

The exosomes (Exo) had always been considered as transport vectors for microRNA (miRNA). An increasing number of data had clarified the influence of Exo on the cell progression of non-small cell lung cancer (NSCLC). Nevertheless, its specific mechanism had not yet been verified. This work was to explore the potential mechanism of Exo-derived miR-631 targeting and regulating E2F family of transcription factor 2 (E2F2) to repress the malignant behavior of NSCLC cells. Test of microRNA (miR)-631 and E2F2 in NSCLC was performed. BMSCs-Exo that altered miR-631 was co-cultured with NSCLC cells. Detection of the cloning and progression of NSCLC cells was performed. Testification of the targeting of miR-631 with E2F2 was conducted. In vivo experiments were performed to verify the results in vitro. In short, elevation of miR-631 Exo repressed the advancement and phosphatidylinositol 3‐kinase/Akt activation of NSCLC cells, while silence of miR-631 was in the opposite. In terms of mechanism, miR-631 exerted the influence via targeting E2F2. The coincident results were obtained in animal models. In brief, BMSC-Exo mediated E2F2 via delivering miR-631 to NSCLC cells to modulate the malignant behavior of NSCLC.

CDKN2B-AS1 promotes the proliferation, clone formation, and invasion of nasopharyngeal carcinoma cells by regulating miR-98-5p/E2F2 axis

OBJECTIVE

To explore the effect of CDKN2B antisense RNA 1 (CDKN2B-AS1) on the proliferation, clone formation, and invasion of nasopharyngeal carcinoma (NPC) cells by regulating miR-98-5p/E2F transcription factor 2 (E2F2) axis.

METHODS

The expressions of CDKN2B-AS1, miR-98-5p, and E2F2 in NPC tissues and cell lines (SUNE-1, 5-8F, 6-10B, and HK-1) as well as in peritumoral normal tissues and cell line NP69 were determined by qRT-PCR. Subcellular localization of CDKN2B-AS1 was detected using the fluorescence in situ hybridization assay. The targeting relationships between CDKN2B-AS1 and miR-98-5p as well as between miR-98-5p and E2F2 were analyzed by the dual-luciferase reporter assay and RNA binding protein immunoprecipitation assay. The proliferation, clone formation and invasion of 5-8F cells were measured using the CCK-8 assay, Clone formation assay, and transwell assay, respectively.

RESULTS

CDKN2B-AS1 was highly expressed in NPC tissues and cells, whereas the expression of miR-98-5p decreased in the NPC tissues and cells. Silencing of CDKN2B-AS1 inhibited the proliferation, clone formation, and invasion of NPC cells (all P<0.05). CDKN2B-AS1 acted asceRNA of miR-98-5p, and miR-98-5p inhibitor could partially reverse the inhibitory effect of silencing CDKN2B-AS1 on NPC cells (all P<0.05). CDKN2B-AS1 upregulated E2F2 by inhibiting miR-98-5p, and the upregulation of E2F2 partially reversed the inhibitory effect of miR-98-5p overexpression on the NPC cells (all P<0.05).

CONCLUSION

CDKN2B-AS1, as a lncRNA, can regulate E2F2 by sponging miR-98-5p to promote the proliferation, clone formation, and invasion of NPC cells.

Expression and Prognostic Role of E2F2 in Hepatocellular Carcinoma

Introduction

Hepatocellular carcinoma (HCC) is a common clinical malignancy. Recent studies reported that E2F transcription factor 2 (E2F2) plays a significant role in tumor progression. However, its expression and biological function in HCC are still unclear. Therefore, we explored the relationship between E2F2 expression and tumor progression in HCC.

Methods

In this study, we utilized some online tools to explore the E2F2 expression in pan-carcinoma and HCC. The association of E2F2 expression with the clinical characteristics and prognosis of HCC was further studied. In addition, we explored the co-expressed genes of E2F2 and mined the positively/negatively corrected significant genes and excavated the possible functions. Meanwhile, the hub gene set was constructed based on protein-protein interaction (PPI) network, and the relationship between E2F2 and immunity was discovered.

Results

We observed that the expression level of E2F2 was generally upregulated in HCC. However, E2F2 expression was not significantly different between HCC and normal tissues in regard to the disease stage 4. Furthermore, we also observed the poor prognosis in patients with high E2F2 expression. The co-expressed genes of E2F2 were identified and further detected. Thereafter, we identified the positively/negatively corrected significant genes and constructed the hub gene network of E2F2 based on PPI network. We also found that E2F2 expression was positively correlated with the infiltration levels of CD4+ T, CD8+ T cells, macrophages, neutrophils, and dendritic cells.

Conclusion

Our findings suggested that E2F2 could be a potential prognostic factor for HCC, which could provide a therapeutic target for the molecular treatment of HCC.

[Research Progress in CircRNA and Radiotherapy Resistance of Non-small Cell Lung Cancer]

As the main type of lung cancer, non-small cell lung cancer (NSCLC) is a common cancer which is characterized by low 5-year survival rate and worse prognosis. Nowadays, some studies show that the low survival rate and worse prognosis are due to the resistance to radiotherapy caused by circRNA. Therefore, to find out the relationship between circRNA and radiotherapy resistance of NSCLC was imoprtant. According to research the relevant literatures, the relationship between circRNA and radiotherapy resistance of NSCLC was explored. CircRNA plays an important role in the invasion, metastasis, proliferation and treatment resistance of NSCLC. The radiation resistance of tumor cells induced by circRNA has become a crucial problem in radiotherapy. CircRNA plays an important role in the radiotherapy resistance of NSCLC.
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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.

Effect of circular RNA, mmu_circ_0000296, on neuronal apoptosis in chronic cerebral ischaemia via the miR-194-5p/Runx3/Sirt1 axis

Chronic cerebral ischaemia (CCI) is a common pathological disorder, which is associated with various diseases, such as cerebral arteriosclerosis and vascular dementia, resulting in neurological dysfunction. As a type of non-coding RNA, circular RNA is involved in regulating the occurrence and development of diseases, such as ischaemic brain injury. Here, we found that HT22 cells and hippocampus treated with CCI had low expression of circ_0000296, Runx3, Sirt1, but high expression of miR-194-5p. Overexpression of circ_0000296, Runx3, Sirt1, and silenced miR-194-5p significantly inhibited neuronal apoptosis induced by CCI. This study demonstrated that circ_0000296 specifically bound to miR-194-5p; miR-194-5p bound to the 3'UTR region of Runx3 mRNA; Runx3 directly bound to the promoter region of Sirt1, enhancing its transcriptional activity. Overexpression of circ_0000296 by miR-194-5p reduced the negative regulatory effect of miR-194-5p on Runx3, promoted the transcriptional effect of Runx3 on Sirt1, and inhibited neuronal apoptosis induced by CCI. mmu_circ_0000296 plays an important role in regulating neuronal apoptosis induced by CCI through miR-194-5p/Runx3/Sirt1 pathway.

Construction of a prognostic model for non-small-cell lung cancer based on ferroptosis-related genes

We wished to construct a prognostic model based on ferroptosis-related genes and to simultaneously evaluate the performance of the prognostic model and analyze differences between high-risk and low-risk groups at all levels. The gene-expression profiles and relevant clinical data of patients with non-small-cell lung cancer (NSCLC) were downloaded from public databases. Differentially expressed genes (DEGs) were obtained by analyzing differences between cancer tissues and paracancerous tissues, and common genes between DEGs and ferroptosis-related genes were identified as candidate ferroptosis-related genes. Next, a risk-score model was constructed using univariate Cox analysis and least absolute shrinkage and selection operator (Lasso) analysis. According to the median risk score, samples were divided into high-risk and low-risk groups, and a series of bioinformatics analyses were conducted to verify the predictive ability of the model. Single-sample gene set enrichment analysis (ssGSEA) was used to investigate differences in immune status between high-risk and low-risk groups, and differences in gene mutations between the two groups were investigated. A risk-score model was constructed based on 21 ferroptosis-related genes. A Kaplan-Meier curve and receiver operating characteristic curve showed that the model had good prediction ability. Univariate and multivariate Cox analyses revealed that ferroptosis-related genes associated with the prognosis may be used as independent prognostic factors for the overall survival time of NSCLC patients. The pathways enriched with DEGs in low-risk and high-risk groups were analyzed, and the enriched pathways were correlated significantly with immunosuppressive status.

Circ_0035483 Functions as a Tumor Promoter in Renal Cell Carcinoma via the miR-31-5p-Mediated HMGA1 Upregulation

Background

Renal cell carcinoma (RCC) that originates from the proximal renal tubules is the most common cancer of the human kidney. Increasing circRNA/miRNA/mRNA networks have been found in RCC regulation. This study will explore the regulatory relation of circular RNA (circRNA) circ_0035483, microRNA-31-5p (miR-31-5p) and high mobility group A1 (HMGA1).

Methods

The levels of circ_0035483, miR-31-5p and HMGA1 were measured by real-time polymerase chain reaction (qRT-PCR) or Western blot. Cell proliferation was determined using Cell Counting Kit-8 (CCK-8) and colony formation assays. Cell migration and invasion were assessed by transwell assay. HMGA1 and epithelial–mesenchymal transition (EMT)-related protein levels were quantified using Western blot. Glycolytic metabolism was evaluated by glucose consumption and lactate production. The interaction between targets was confirmed via dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays. In vivo experiment was performed through the establishment of xenograft models in mice.

Results

Circ_0035483 expression was upregulated in RCC tissues and cells. The inhibitory effects on RCC cell proliferation, migration, invasion, EMT and glycolysis were induced after circ_0035483 was downregulated. MiR-31-5p was identified as a target of circ_0035483 and miR-31-5p upregulation was related to the function of circ_0035483 knockdown in RCC cells. Additionally, miR-31-5p targeted HMGA1 and inhibited the malignant behaviors of RCC cells by negatively regulating HMGA1. Moreover, HMGA1 expression was regulated by circ_0035483 via targeting miR-31-5p. Circ_0035483 also affected tumor growth in vivo by relying on the miR-31-5p/HMGA1 axis.

Conclusion

These findings clarified that the tumor-promoting function of circ_0035483 in RCC was partly achieved by regulating the miR-31-5p/HMGA1 axis.