Emerging roles of circular RNAs in non‑small cell lung cancer (Review)

Transcription factor MAFK binds to circRPPH to regulate SIRT gene-mediated cellular pyroptosis and lung adenocarcinoma progression

OBJECTIVE

Lung adenocarcinoma (LUAD) represents the most prevalent subtype of lung cancer (LC), accounting for 50% of all LC cases, with its occurrence continuing to rise. Multiple pyroptotic pathway mediators are implicated in LC initiation. The study delved into the mechanism of circRPPH1 in pyroptosis in LUAD.

METHODS

We first examined the relationship between circRPPH1 and the clinical features of LUAD patients by analyzing circRNA gene expression profiles from the GEO database and validating findings with clinical samples. Downstream pathways influenced by circRPPH1 were identified and assessed for their roles in LUAD cell growth and pyroptosis using gain-and-loss-of-function assays.

RESULTS

circRPPH1 was significantly upregulated in LUAD and associated with poor prognosis. It binds to the transcription factor MAFK, enhancing SIRT1 expression and activating the MAFK-Keap1 signaling pathway. Reducing circRPPH1 expression decreased SIRT1 levels, inhibited cell proliferation both in vivo and ex vivo, and increased markers of cellular pyroptosis. Additionally, overexpressing SIRT1 mitigated the effects of circRPPH1 silencing.

CONCLUSION

circRPPH1 promotes LUAD progression by binding to MAFK, enhancing SIRT1 expression, and inhibiting cellular pyroptosis.

circ-ZEB1 Enhances NSCLC Metastasis and Proliferation by Modulating the miR-491-5p/EIF5A Axis

Background: Circular RNAs (circRNAs), covalently closed single-stranded RNAs, have been implicated in cancer progression. A previous investigation revealed that circ-ZEB1 is expressed abnormally in liver cancer. However, the roles of circ-ZEB1 in non-small cell lung cancer (NSCLC) are unknown. Methods: In this study, we used fluorescence in situ hybridization (FISH) and RT-qPCR to study circ-ZEB1 expression in NSCLC cells and tissues. A luciferase reporter assay was performed to validate downstream targets of circ-ZEB1. Transwell migration, 5-ethynyl-20-deoxyuridine (EdU), and cell counting kit-8 (CCK8) assays were performed to assess proliferation and migration. In vivo metastasis and tumorigenesis assays were also performed to investigate circ-ZEB1 functions during NSCLC. Results: Our results showed that circ-ZEB1 expression was increased in NSCLC tissues and cells. circ-ZEB1 downregulation suppressed NSCLC cell proliferation as well as migration in vitro and in vivo. Luciferase data confirmed EIF5A and miR-491-5p as downstream targets of circ-ZEB1. EIF5A overexpression and miR-491-5p suppression reversed NSCLC cell migration post circ-ZEB1 silencing. Conclusion: Our collective findings advised that circ-ZEB1 takes part in the malignant progression through regulating the miR-491-5p/EIF5A axis, highlighting its potential as an effective NSCLC therapeutic target.

From non-coding RNAs to histone modification: The epigenetic mechanisms in tomato fruit ripening and quality regulation

Ripening is one of the most important stages of fruit development and determines the fruit quality. Various factors play a role in this process, with epigenetic mechanisms emerging as important players. Epigenetic regulation encompasses DNA methylation, histone modifications and variants, chromatin remodeling, RNA modifications, and non-coding RNAs. Over the past decade, studies using tomato as a model have made considerable progress in understanding the impact of epigenetic regulation on fleshy fruit ripening and quality. In this paper, we provide an overview of recent advancements in the epigenetic regulation of tomato fruit ripening and quality regulation, focusing on three main mechanisms: DNA/RNA modifications, non-coding RNAs, and histone modifications. Furthermore, we highlight the unresolved issues and challenges within this research field, offering perspectives for future investigations to drive agricultural innovation.

The potential role of circular RNAs -regulated PI3K signaling in non-small cell lung cancer: Molecular insights and clinical perspective

Non-small cell lung cancer (NSCLC), accounting for more than 80% of all cases, is the predominant form of lung cancer and the leading cause of cancer-related deaths worldwide. Significant progress has been made in diagnostic techniques, surgical interventions, chemotherapy protocols, and targeted therapies at the molecular level, leading to enhanced treatment outcomes in patients with NSCLC. Extensive evidence supports the use of circular RNAs (circRNAs), a specific category of naturally occurring non-coding small RNAs (ncRNAs), for the diagnosis, monitoring of treatment efficacy, and assessment of survival in NSCLC. CircRNAs have been identified to play significant roles in various aspects of cancer formation, either as tumor suppressors or tumor promoters, contributing to cancer development through several signaling pathways, including the phosphoinositide 3-kinases (PI3Ks) pathway. This pathway is well-established because of its regulatory role in essential cellular processes. CircRNAs regulate the PI3K/AKT pathway by targeting diverse cellular elements. This review aims to provide insight into the involvement of several circRNAs linked to the PI3K/AKT pathway in NSCLC.

Non-Coding RNAs as Key Regulators in Lung Cancer

For several decades, most lung cancer investigations have focused on the search for mutations in candidate genes; however, in the last decade, due to the fact that most of the human genome is occupied by sequences that do not code for proteins, much attention has been paid to non-coding RNAs (ncRNAs) that perform regulatory functions. In this review, we principally focused on recent studies of the function, regulatory mechanisms, and therapeutic potential of ncRNAs including microRNA (miRNA), long ncRNA (lncRNA), and circular RNA (circRNA) in different types of lung cancer.

Circular RNA in Non-small Cell Lung Carcinoma: Identification of Targets and New Treatment Modalities

Despite availability of several treatment options for non-small cell lung cancer (NSCLC), such as surgery, chemotherapy, radiation, targeted therapy and immunotherapy, the survival rate of patients for five years is in the range of 22%. Therefore, identification of new targets and treatment modalities for this disease is an important issue. In this context, we screened the PubMed database for up-regulated circular RNAs (circRNAs) which promote growth of NSCLC in preclinical models in vitro as well as in vivo xenograft models in immuno-compromised mice. This approach led to potential targets for further validation and inhibition with small molecules or antibody-derived entities. In case of preclinical validation, the corresponding circRNAs can be inhibited with small interfering RNAs (siRNA) or short hairpin RNAs (shRNA). The identified circRNAs act by sponging microRNAs (miRs) preventing cleavage of the mRNA of the corresponding targets. We identified nine circRNAs up-regulating transmembrane receptors, five circRNAs increasing expression of secreted proteins, nine circRNAs promoting expression of components of signaling pathways, six circRNAs involved in regulation of splicing and RNA processing, six circRNAs up-regulating actin-related and RNA processing components, seven circRNAs increasing the steady-state levels of transcription factors, two circRNAs increasing high-mobility group proteins, four circRNAs increasing components of the epigenetic modification system and three circRNAs up-regulating protein components of additional systems.

Revealing Landscape of Competing Endogenous RNA Networks in Sepsis-Induced Cardiovascular Diseases

Cardiovascular dysfunction induced by sepsis is one of the most common phenotypes of cardiovascular diseases (CVDs), which is closely related to the high mortality of sepsis and is an urgent health problem to be solved worldwide. Unfortunately, the exact pathogenesis and pathophysiology of sepsis-induced cardiovascular dysfunction are not clear. As a research hotspot in recent years, competing endogenous RNA (ceRNA) networks are involved in the modulation of the pathophysiological progression of many diseases, including sepsis-related CVDs. Both long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) can specifically bind to microRNAs (miRNAs) as ceRNAs to target messenger RNAs (mRNAs), forming a ceRNA network composed of lncRNA/circRNA-miRNA-mRNA. This review demonstrates the potential regulatory mechanism of the ceRNA networks in sepsis-induced cardiovascular toxicity, hoping to provide novel therapeutic strategies and monitoring targets for sepsis-related CVDs.

CircDLG1 promotes malignant development of non-small cell lung cancer through regulation of the miR-630/CENPF axis

BACKGROUND

Circular RNAs (circRNAs) have been reported to be crucial modulatory molecules in the etiology of non-small cell lung cancer (NSCLC). This study aimed to probe the precise role and mechanism of circRNA discs large MAGUK scaffold protein 1 (circDLG1) in the malignant progression of NSCLC.

METHODS

The abundances of circDLG1, miR-630, and centromere protein F (CENPF) mRNAs were gauged by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was tested in 3‑(4, 5‑dimethylthiazol-2-yl)-2, 5‑diphenyltetrazolium bromide (MTT) assay and 5‑ethynyl-2'-deoxyuridine (EdU)-incorporation assay. Cell apoptosis was analyzed by flow cytometry. Cell migration and invasion were assessed by transwell assay. Western blot was exploited to examine the levels of all proteins. The interaction between miR-630 and circDLG1 or CENPF was verified by dual-luciferase reporter, RNA pull-down, and/or RNA immunoprecipitation assays. Tumor xenograft assay and immunohistochemistry (IHC) were executed for the role of circDLG1 in tumor growth in vivo.

RESULTS

CircDLG1 and CENPF were highly expressed in NSCLC, while miR-630 was downregulated. CircDLG1 silencing repressed proliferation, migration, and invasion, and expedited apoptosis of NSCLC cells in vitro. Mechanistically, circDLG1 deficiency modulated NSCLC cell malignant development through interacting with miR-630. Furthermore, CENPF was targeted by miR-630, and circDLG1 could positively control CENPF expression through acting as an miR-630 sponge. Furthermore, CENPF overexpression reversed the repressive impacts of circDLG1 inhibition in the malignant behaviors of NSCLC cells. Besides, circDLG1 interference hindered tumor growth in vivo.

CONCLUSION

CircDLG1 knockdown could impede NSCLC advancement through modulating the miR-630/CENPF axis, manifesting as a promising molecular target for NSCLC treatment.

Epigenetic regulation of autophagy by non-coding RNAs in gastrointestinal tumors: Biological functions and therapeutic perspectives

Cancer is the manifestation of changes and mutations in genetic and epigenetic levels. Non-coding RNAs (ncRNAs) are commonly dysregulated in disease pathogenesis, and their role in cancer has been well-documented. The ncRNAs regulate various molecular pathways and mechanisms in cancer that can lead to induction/inhibition of carcinogenesis. Autophagy is a molecular "self-digestion" mechanism its function can be pro-survival or pro-death in tumor cells. The aim of the present review is to evaluate the role of ncRNAs in regulating autophagy in gastrointestinal tumors. The role of the ncRNA/autophagy axis in affecting the progression of gastric, liver, colorectal, pancreatic, esophageal, and gallbladder cancers is investigated. Both ncRNAs and autophagy mechanisms can function as oncogenic or onco-suppressor and this interaction can determine the growth, invasion, and therapy response of gastrointestinal tumors. ncRNA/autophagy axis can reduce/increase the proliferation of gastrointestinal tumors via the glycolysis mechanism. Furthermore, related molecular pathways of metastasis, such as EMT and MMPs, are affected by the ncRNA/autophagy axis. The response of gastrointestinal tumors to chemotherapy and radiotherapy can be suppressed by pro-survival autophagy, and ncRNAs are essential regulators of this mechanism. miRNAs can regulate related genes and proteins of autophagy, such as ATGs and Beclin-1. Furthermore, lncRNAs and circRNAs down-regulate miRNA expression via sponging to modulate the autophagy mechanism. Moreover, anti-cancer agents can affect the expression level of ncRNAs regulating autophagy in gastrointestinal tumors. Therefore, translating these findings into clinics can improve the prognosis of patients.

Circular RNA Sec61 subunit alpha isoform 1 by competitive absorption of microRNA-513a-5p mediates peroxisomal biogenesis factor 5 expression and promotes the malignant phenotype of non-small cell lung cancer

Circular RNAs (circRNAs) are functional RNAs in the development and metabolism of non-small cell lung cancer (NSCLC). Therein, this paper particularly elucidated the circRNA SEC61 subunit alpha isoform 1 (circSEC61A1) in NSCLC has not been fully elucidated. Clinical analysis of circSEC61A1 expression was performed on specimens collected from 51 patients with primary NSCLC, together with patients' survival. Cell experiments were performed after interfering with circSEC61A1, microRNA (miR)-513a-5p, and peroxisomal biogenesis factor 5 (PEX5) expression, respectively, and cell malignant phenotypes and aerobic glycolysis were evaluated, as well as epithelial-to-mesenchymal transition (EMT)-related markers and Wnt/β-catenin pathway. Xenografts experiments studied the performance of circSEC61A1 in vivo. The downstream molecules of circSEC61A1 were searched. Our data demonstrated that circSEC61A1 was upregulated in NSCLC patients, showing an association with poorer survival outcomes. In cell experiments, circSEC61A1 overexpression promoted NSCLC malignant phenotypes, glycolysis, EMT, and Wnt/β-catenin pathway activation, whereas circSEC61A1 underexpression did the opposite. Knockdown of circSEC61A1 limited tumor growth and metastasis. Furthermore, circSEC61A1 could regulate PEX5 expression through competitive absorption of miR-513a-5p. Generally, circSEC61A1 is a potential biomarker for NSCLC, and circSEC61A1 serves tumor-promoting action in the progression of NSCLC.

Role of circular RNAs in the diagnosis, regulation of drug resistance and prognosis of lung cancer (Review)

Lung cancer is one of the most common malignant tumors in China and is the highest cause of mortality among male and female patients, both in urban and rural areas. A subset of patients with lung cancer only display chest tightness without any other obvious symptoms. This is because most symptoms do not manifest during the early stages of disease development. Consequently, most patients with lung cancer are diagnosed when the disease is in the advanced stages, when they are already unfit for surgical treatment. Furthermore, the prognosis of patients with lung cancer is poor. The 5-year survival rate of patients with stage IA lung cancer is 85%, compared with 6% in those with stage IV. This requires the development of strategies for early diagnosis, treatment and prognosis to improve the management of lung cancer. Circular RNAs (circRNAs) belong to a class of closed circular non-coding RNAs formed by reverse splicing of a precursor mRNA. These RNAs are highly stable, ubiquitously expressed, conserved, and show high specificity. CircRNAs regulate biological processes, such as the proliferation, differentiation and invasion of lung cancer cells. Therefore, they can be used as biomarkers for the early diagnosis and prognosis prediction of lung cancer, as well as novel targets for therapy design. In the present review, the biological characteristics and functions of circRNAs, as well as their application in the diagnosis, control of drug resistance and effect on the prognosis of patients with lung cancer, will be discussed.

CircRNA SOD2 motivates non-small cell lungs cancer advancement with EMT via acting as microRNA-2355-5p’s competing endogenous RNA to mediate calmodulin regulated spectrin associated proteins-2

Circular RNAs (circRNAs) are closely linked with human cancer development such as non-small-cell lung cancer (NSCLC). However, the characteristics and specific functions of most circRNAs in NSCLC remained unknown. Previous studies have suggested that circRNA SOD2 (CircSOD2) expression was upregulated in a number of cancers. This study aimed to explore the functions of circSOD2 in NSCLC advancement with epithelial-mesenchymal transition (EMT). Expression profile analysis of circSOD2, miR-2355-5p, and calmodulin-regulated spectrin-associated protein 2 (CAMSAP2) was detected by real-time quantitative PCR (RT-qPCR). Transwell assay, cell migration assay, CCK8, ELISA, RIP assay, RNA pull-down assay, and Western blot analysis were performed to evaluate the functions of circSOD2, miR-2355-5p, and CAMSAP2. We found elevated expression of circSOD2 and CAMSAP2 while reduced expression of miR-2355-5p in NSCLC tumor tissues. Silencing or overexpression of CircSOD2 resulted in increased or decreased expression of miR-2355-5p, respectively. Mechanically, we showed that silencing of CircSOD2 and overexpression of miR-2355-5p resulted in the reduced rate of NSCLC cell proliferation. Inhibition of miR-2355-5p reversed the changes induced via silencing of CircSOD2. MiR-2355-5p binds to the CircSOD2 promoter and triggered its stimulation, which further activated circSOD2 expression. CircSOD2 suppression impaired lung cancer cell growth, cell migration, prohibited cell cycle progression, and in vivo tumor growth by targeting miR-2355-5p expression in NSCLC tissues. Meanwhile, increased expression of CAMSAP2 reversed the changes stimulated by the elevated level of miR-2355-5p in NSCLC progression. This innovative signaling axis CircSOD2/miR-2355-5p/CAMSAP2 illustrated the new horizon to investigate NSCLC tumorigenesis and provided new prognosis and treatment of NSCLC.