Roles of circRNAs on tumor autophagy

Mechanistic insights into circRNA-mediated regulation of PI3K signaling pathway in glioma progression

Circular RNAs (CircRNAs) are non-coding RNAs (ncRNAs) characterized by a stable circular structure that regulates gene expression at both transcriptional and post-transcriptional levels. They play diverse roles, including protein interactions, DNA methylation modification, protein-coding potential, pseudogene creation, and miRNA sponging, all of which influence various physiological processes. CircRNAs are often highly expressed in brain tissues, and their levels vary with neural development, suggesting their significance in nervous system diseases such as gliomas. Research has shown that circRNA expression related to the PI3K pathway correlates with various clinical features of gliomas. There is an interact between circRNAs and the PI3K pathway to regulate glioma cell processes such as proliferation, differentiation, apoptosis, inflammation, angiogenesis, and treatment resistance. Additionally, PI3K pathway-associated circRNAs hold potential as biomarkers for cancer diagnosis, prognosis, and treatment. In this study, we reviewed the latest advances in the expression and cellular roles of PI3K-mediated circRNAs and their connections to glioma carcinogenesis and progression. We also highlighted the significance of circRNAs as diagnostic and prognostic biomarkers and therapeutic targets in glioma.

Exploration of lncRNA/circRNA-miRNA-mRNA network in patients with chronic atrophic gastritis in Tibetan plateau areas based on DNBSEQ-G99 RNA sequencing

A higher incidence of chronic atrophic gastritis (CAG) is generally considered as a precancerous lesion in gastric cancer (GC). The aim of this study was to identify potential molecules involved in the pathogenesis of CAG in the Tibetan plateau, hoping to help the diagnosis and management of the disease. Atrophic and non-atrophic gastric mucosal tissue samples were collected from seven patients with chronic gastritis (CG). Differentially expressed lncRNAs, circRNAs, miRNAs, and mRNAs between CAG and chronic non-atrophic gastritis (CNAG) groups were identified based on DNBSEQ-G99 RNA sequencing. Subsequently, competitive endogenous RNA (ceRNA) regulatory networks (lncRNA/circRNA-miRNA-mRNA networks) were constructed. Two datasets (GSE153224 and GSE163416), involving data from non-Tibetan plateau areas, were used to further screen out Tibetan plateau key mRNAs, followed by the common genes of Tibetan plateau key and ferroptosis-related mRNAs were also identified. Functional enrichment analyses were performed to investigate the biological functions of Tibetan plateau mRNAs in the CAG. A total of seven lncRNA-miRNA-mRNA relationship pairs and 424 circRNA-miRNA-mRNA relationship pairs were identified in this study. The relationship pairs of hsa_circ_0082984-hsa-miR-204-5p-CACNG8, lncRNA DRAIC/has_circ_0008561-hsa-miR-34a-5p-AR/GXYLT2, lncRNA GAS1RR/RGMB-AS1/hsa_circ_0008561-hsa-miR-3614-5p-TMEM216/SUSD5, and LINC00941/hsa_circ_0082984-hsa-miR-873-3p-TMC5 can be involved in the pathogenesis of CAG. Additionally, eight common genes of Tibetan plateau key and ferroptosis-related differentially expressed mRNAs (DEmRNAs) (CBS, SLC2A4, STAT3, ALOX15B, ATF3, IDO1, NOX4, and SOCS1) were identified in CAG. The common genes of Tibetan plateau key and ferroptosis-related DEmRNAs can play a role in the JAK-STAT signaling pathway. This study identified important molecular biomarkers that may be involved in regulating the pathological mechanisms of CAG in the Tibetan plateau, which provides potential research directions for future research.

Non-coding RNAs in enzalutamide resistance of castration-resistant prostate cancer

Enzalutamide (Enz) is a next-generation androgen receptor (AR) antagonist used to treat castration-resistant prostate cancer (CRPC). Unfortunately, the relapsing nature of CRPC results in the development of Enz resistance in many patients. Non-coding RNAs (ncRNAs) are RNA molecules that do not encode proteins, which include microRNAs (miRNA), long ncRNAs (lncRNAs), circular RNAs (circRNAs), and other ncRNAs with known and unknown functions. Recently, dysregulation of ncRNAs in CRPC, particularly their regulatory function in drug resistance, has attracted more and more attention. Herein, we introduce the roles of dysregulation of different ncRNAs subclasses in the development of CRPC progression and Enz resistance. Recently determined mechanisms of Enz resistance are discussed, focusing mainly on the role of AR-splice variant-7 (AR-V7), mutations, circRNAs and lncRNAs that act as miRNA sponges. Also, the contributions of epithelial-mesenchymal transition and glucose metabolism to Enz resistance are discussed. We summarize the different mechanisms of miRNAs, lncRNAs, and circRNAs in the progression of CRPC and Enz resistance, and highlight the prospect of future therapeutic strategies against Enz resistance.

Circular RNAs in hepatocellular carcinoma: biogenesis, function, and pathology

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Both genetic and environmental factors through a multitude of underlying molecular mechanisms participate in the pathogenesis of HCC. Recently, numerous studies have shown that circular RNAs (circRNAs), an emerging class of non-coding RNAs characterized by the presence of covalent bonds linking 3' and 5' ends, play an important role in the initiation and progression of cancers, including HCC. In this review, we outline the current status of the field of circRNAs, with an emphasis on the functions and mechanisms of circRNAs in HCC and its microenvironment. We also summarize and discuss recent advances of circRNAs as biomarkers and therapeutic targets. These efforts are anticipated to throw new insights into future perspectives about circRNAs in basic, translational and clinical research, eventually advancing the diagnosis, prevention and treatment of HCC.

Profiling of circRNA expressions in radiation-treated head and neck cancer cells and the potential role of circPVT1

OBJECTIVE

Radiotherapy is an indispensable treatment modality for head and neck cancers (HNCs). Due to their stable structure, circular RNAs (circRNA) have been implicated as potential biomarkers for clinical use in cancers. The purpose of this study was profiling the circRNA in radiation-treated head and neck cancer cells to identify potential differentially expressed circRNAs.

DESIGN

The effects of radiation on the expression level of circRNAs were investigated in HNCs cells, compared to healthy cell lines. To predict the potential role of circRNAs in HNC patients, tissue expression levels, survival analyses of circRNAs, and circRNA-miRNA network were evaluated using TCGA/CPTAC datasets. Based on expression level in irradiated cells, circPVT1 (plasmacytoma variant translocation 1) was further investigated by sequence analysis.

RESULTS

The study revealed the characterization of differentially expressed circRNAs in cancer cells and that irradiation made significant changes in the expression of circRNAs. These findings suggest that certain circRNAs, especially circPVT1, may be potential biomarkers to monitor radiotherapy effects in patients with HNCs.

CONCLUSIONS

CircRNAs may be promising molecules for improving and understanding radiotherapy efficacy in HNCs.

Circular RNA-regulated autophagy is involved in cancer progression

Circular RNAs (circRNAs) are a sort of long, non-coding RNA molecules with a covalently closed continuous ring structure without 5'-3' polarity and poly-A tail. The modulative role of circRNAs in malignant diseases has been elucidated by many studies in recent years via bioinformatics and high-throughput sequencing technologies. Generally, circRNA affects the proliferative, invasive, and migrative capacity of malignant cells via various mechanisms, exhibiting great potential as novel biomarkers in the diagnoses or treatments of malignancies. Meanwhile, autophagy preserves cellular homeostasis, serving as a vital molecular process in tumor progression. Mounting studies have demonstrated that autophagy can not only contribute to cancer cell survival but can also induce autophagic cell death in specific conditions. A growing number of research studies have indicated that there existed abundant associations between circRNAs and autophagy. Herein, we systemically reviewed and discussed recent studies on this topic in different malignancies and concluded that the circRNA–autophagy axis played crucial roles in the proliferation, metastasis, invasion, and drug or radiation resistance of different tumor cells.

Use of Circular RNAs in Diagnosis, Prognosis and Therapeutics of Renal Cell Carcinoma

Renal cell carcinoma is the most common type of kidney cancer, representing 90% of kidney cancer diagnoses, and the deadliest urological cancer. While the incidence and mortality rates by renal cell carcinoma are higher in men compared to women, in both sexes the clinical characteristics are the same, and usually unspecific, thereby hindering and delaying the diagnostic process and increasing the metastatic potential. Regarding treatment, surgical resection remains the main therapeutic strategy. However, even after radical nephrectomy, metastasis may still occur in some patients, with most metastatic renal cell carcinomas being resistant to chemotherapy and radiotherapy. Therefore, the identification of new biomarkers to help clinicians in the early detection, and treatment of renal cell carcinoma is essential. In this review, we describe circRNAs related to renal cell carcinoma processes reported to date and propose the use of some in therapeutic strategies for renal cell carcinoma treatment.

Novel insights into the role of circular RNAs in Parkinson disease: An emerging renaissance in the management of neurodegenerative diseases

Parkinson's disease (PD), as a debilitating neurodegenerative disease, particularly affects the elderly population, and is clinically identified by resting tremor, rigidity, and bradykinesia. Pathophysiologically, PD is characterized by an early loss of dopaminergic neurons in the Substantia nigra pars compacta, accompanied by the extensive aggregation of alpha-synuclein (α-Syn) in the form of Lewy bodies. The onset of PD has been reported to be influenced by multiple biological molecules. In this context, circular RNAs (circRNAs), as tissue-specific noncoding RNAs with closed structures, have been recently demonstrated to involve in a set of PD's pathogenic processes. These RNA molecules can either up- or downregulate the expression of α-Syn, as well as moderating its accumulation through different regulatory mechanisms, in which targeting microRNAs (miRNAs) is considered the most common pathway. Since circRNAs have prominent structural and biological characteristics, they could also be considered as promising candidates for PD diagnosis and treatment. Unfortunately, PD has become a global health concern, and a large number of its pathogenic processes are still unclear; thus, it is crucial to elucidate the ambiguous aspects of PD pathophysiology to improve the efficiency of diagnostic and therapeutic strategies. In line with this fact, the current review aims to highlight the interplay between circRNAs and PD pathogenesis, and then discusses the diagnostic and therapeutic potential of circRNAs in PD progression. This study will thus be the first of its kind reviewing the relationship between circRNAs and PD.

Liquid biopsy in lung cancer: significance in diagnostics, prediction, and treatment monitoring

Primary lung cancer is one of the most common malignant tumors in China. Approximately 60% of lung cancer patients have distant metastasis at the initial diagnosis, so it is necessary to find new tumor markers for early diagnosis and individualized treatment. Tumor markers contribute to the early diagnosis of lung cancer and play important roles in early detection and treatment, as well as in precision medicine, efficacy monitoring, and prognosis prediction. The pathological diagnosis of lung cancer in small biopsy specimens determines whether there are tumor cells in the biopsy and tumor type. Because biopsy is traumatic and the compliance of patients with multiple biopsies is poor, liquid biopsy has become a hot research direction. Liquid biopsies are advantageous because they are nontraumatic, easy to obtain, reflect the overall state of the tumor, and allow for real-time monitoring. At present, liquid biopsies mainly include circulating tumor cells, circulating tumor DNA, exosomes, microRNA, circulating RNA, tumor platelets, and tumor endothelial cells. This review introduces the research progress and clinical application prospect of liquid biopsy technology for lung cancer.

hsa_circ_0013401 Accelerates the Growth and Metastasis and Prevents Apoptosis and Autophagy of Neuroblastoma Cells by Sponging miR-195 to Release PAK2

Background

Increased levels of circRNAs have been identified in a variety of cancers. However, the specific functions and mechanisms of circRNAs in neuroblastoma (NB) have not been fully explored.

Methods

The levels of hsa_circ_0045997, hsa_circ_0080307, hsa_circ_0013401, hsa_circ_0077578, and microRNA-195 were confirmed by RT-qPCR in NB. Gain- and loss-of-function assays and rescue experiments were conducted to determine the influence of hsa_circ_0013401, miR-195, and P21-activated kinase 2 (PAK2) on the proliferation, apoptosis, autophagy, migration, and invasion of NB cells. Regulatory gene targets were validated by the luciferase assay. A xenograft mouse model was used to determine the in vivo effects of hsa_circ_0013401.

Results

hsa_circ_0013401 was highly expressed, miR-195 was lowly expressed, and there was a negative correlation between hsa_circ_0013401 and miR-195 in NB. The inhibitory effects of hsa_circ_0013401 knockdown suppressed the proliferation, migration, and invasion and induced the apoptosis and autophagy of NB cells by targeting miR-195 to downregulate PAK2 expression. Luciferase reporter assays showed that miR-195 was a direct target of hsa_circ_0013401, and PAK2 was the downstream target gene of miR-195. In vivo studies showed that hsa_circ_0013401 promotes tumor formation.

Conclusions

hsa_circ_0013401 induced NB progression through miR-195 to enhance PAK2. Therefore, we might highlight a novel regulatory axis (hsa_circ_0013401/miR-195/PAK2) in NB.

CircRNAs as promising biomarker in diagnosis of breast cancer: An updated meta-analysis

Background

Circular RNAs (circRNAs) have been identified to be involved in onset and progression of multiple malignant tumors. The present study aimed to systematically evaluate the diagnostic values of circRNAs in breast cancer.

Methods

The PubMed, Web of Science, Embase, CNKI, and Wanfang online databases were searched for the relevant studies before December 31, 2020. Statistical analysis of the diagnostic tests was performed based on STATA 16.0, Meta‐DiSc 1.4, and RevMan 5.3 software. The threshold effect and publication bias were measured by the Spearman correlation and Deeks’ funnel plot asymmetry test, respectively.

Results

Twenty‐one studies from 13 articles were included in this meta‐analysis. The pooled sensitivity and specificity were 0.77 and 0.71, respectively. The pooled positive likelihood ratio (PLR), negative likelihood ratio (NLR), and overall diagnostic odds ratio (DOR) were 2.6, 0.33, and 8, respectively. Furthermore, the area under the summary receiver operator characteristic curve was 0.80. In addition, down‐regulated circRNAs achieved a diagnostic performance higher than up‐regulated circRNAs, with area under curve (AUC) values of 0.81 and 0.74, respectively. Studies based on tissue samples presented better diagnostic accuracy than those based on plasma samples, with AUC values of 0.80 and 0.67. In addition, two circRNAs, including circ_0001073 and circTADA2A‐E5/E6, showed higher diagnostic values, with AUC value of 0.990 and 0.937, respectively. According to the results of meta‐regression, the case size (p<0.05) might be the source of the heterogeneity.

Conclusion

CircRNAs exhibited a high diagnostic value for breast cancer and may function as potential diagnostic biomarkers for breast cancer.

Autophagy-related circRNA evaluation reveals hsa_circ_0001747 as a potential favorable prognostic factor for biochemical recurrence in patients with prostate cancer

Prostate cancer (PCa) is a common high-incidence malignancy in men, some of whom develop biochemical recurrence (BCR) in the advanced stage. However, there are currently no accurate prognostic indicators of BCR in PCa. The aim of our study was to identify an autophagy-related circular RNA prognostic factor of BCR for patients with PCa. In this study, immunochemistry revealed that the classic autophagy marker MAP1LC3B was positively correlated with Gleason score. Least absolute shrinkage and selector operator regression were conducted to develop a novel prognostic model with tenfold cross-validation and an L1 penalty. Five autophagy-related circRNA signatures were included in the prognostic model. Patients with PCa were ultimately divided into high- and low-risk groups, based on the median risk score. Patients with PCa, who had a high risk score, were more likely to develop BCR in a shorter period of time. Univariate and multivariate Cox regression analyses demonstrated that the risk score was an independent variable for predicting BCR in PCa. In addition, a prognostic nomogram integrated with the risk score and numerous clinicopathological parameters was developed to accurately predict 3- and 5-year BCR of patients with PCa. Finally, the hsa_circ_0001747 signature was selected for further experimental verification in vitro and in vivo, which showed that downregulated hsa_circ_0001747 might facilitate PCa via augmenting autophagy. Our findings indicate that the autophagy-related circRNA signature hsa_circ_0001747 may serve as a promising indicator for BCR prediction in patients with PCa.