circMTO1 sponges microRNA-219a-5p to enhance gallbladder cancer progression via the TGF-β/Smad and EGFR pathways

Therapeutic importance and diagnostic function of circRNAs in urological cancers: from metastasis to drug resistance

Circular RNAs (circRNAs) are a member of non-coding RNAs with no ability in encoding proteins and their aberrant dysregulation is observed in cancers. Their closed-loop structure has increased their stability, and they are reliable biomarkers for cancer diagnosis. Urological cancers have been responsible for high mortality and morbidity worldwide, and developing new strategies in their treatment, especially based on gene therapy, is of importance since these malignant diseases do not respond to conventional therapies. In the current review, three important aims are followed. At the first step, the role of circRNAs in increasing or decreasing the progression of urological cancers is discussed, and the double-edged sword function of them is also highlighted. At the second step, the interaction of circRNAs with molecular targets responsible for urological cancer progression is discussed, and their impact on molecular processes such as apoptosis, autophagy, EMT, and MMPs is highlighted. Finally, the use of circRNAs as biomarkers in the diagnosis and prognosis of urological cancer patients is discussed to translate current findings in the clinic for better treatment of patients. Furthermore, since circRNAs can be transferred to tumor via exosomes and the interactions in tumor microenvironment provided by exosomes such as between macrophages and cancer cells is of importance in cancer progression, a separate section has been devoted to the role of exosomal circRNAs in urological tumors.

A Circular RNA Generated from Nebulin (NEB) Gene Splicing Promotes Skeletal Muscle Myogenesis in Cattle as Detected by a Multi-Omics Approach

Cattle and the draught force provided by its skeletal muscle have been integral to agro-ecosystems of agricultural civilization for millennia. However, relatively little is known about the cattle muscle functional genomics (including protein coding genes, non-coding RNA, etc.). Circular RNAs (circRNAs), as a new class of non-coding RNAs, can be effectively translated into detectable peptides, which enlightened us on the importance of circRNAs in cattle muscle physiology function. Here, RNA-seq, Ribosome profiling (Ribo-seq), and peptidome data are integrated from cattle skeletal muscle, and detected five encoded peptides from circRNAs. It is further identified and functionally characterize a 907-amino acids muscle-specific peptide that is named circNEB-peptide because derived by the splicing of Nebulin (NEB) gene. This peptide localizes to the nucleus and cytoplasm and directly interacts with SKP1 and TPM1, key factors regulating physiological activities of myoblasts, via ubiquitination and myoblast fusion, respectively. The circNEB-peptide is found to promote myoblasts proliferation and differentiation in vitro, and induce muscle regeneration in vivo. These findings suggest circNEB-peptide is an important regulator of skeletal muscle regeneration and underscore the possibility that more encoding polypeptides derived by RNAs currently annotated as non-coding exist.

Electroacupuncture protective effects after cerebral ischemia are mediated through miR-219a inhibition

BACKGROUND

Electroacupuncture (EA) is a complementary and alternative therapy which has shown protective effects on vascular cognitive impairment (VCI). However, the underlying mechanisms are not entirely understood.

METHODS

Rat models of VCI were established with cerebral ischemia using occlusion of the middle cerebral artery or bilateral common carotid artery. The brain structure and function imaging were measured through animal MRI. miRNA expression was detected by chip and qPCR. Synaptic functional plasticity was detected using electrophysiological techniques.

RESULTS

This study demonstrated the enhancement of Regional Homogeneity (ReHo) activity of blood oxygen level-dependent (BOLD) signal in the entorhinal cortical (EC) and hippocampus (HIP) in response to EA treatment. miR-219a was selected and confirmed to be elevated in HIP and EC in VCI but decreased after EA. N-methyl-D-aspartic acid receptor1 (NMDAR1) was identified as the target gene of miR-219a. miR-219a regulated NMDAR-mediated autaptic currents, spontaneous excitatory postsynaptic currents (sEPSC), and long-term potentiation (LTP) of the EC-HIP CA1 circuit influencing synaptic plasticity. EA was able to inhibit miR-219a, enhancing synaptic plasticity of the EC-HIP CA1 circuit and increasing expression of NMDAR1 while promoting the phosphorylation of downstream calcium/calmodulin-dependent protein kinase II (CaMKII), improving overall learning and memory in VCI rat models.

CONCLUSION

Inhibition of miR-219a ameliorates VCI by regulating NMDAR-mediated synaptic plasticity in animal models of cerebral ischemia.

Investigation of the clinicopathological and prognostic role of circMTO1 in multiple cancers

OBJECTIVE

To observe the prognostic value of circular RNA mitochondrial tRNA translation optimization 1 (circMTO1) in human tumors.

METHODS

We searched multiple databases for related reports published before November 01, 2021. The OR/HR and 95% CI were extracted to explore the correlation between circMTO1 expression and clinicopathological features in various cancers. The stability of the results from meta-analysis was estimated via sensitivity analysis. We adopted Begg's funnel plots and Egger's test to appraise the potential bias of publication. Subgroup analysis for overall survival (OS) were also performed.

RESULTS

11 studies containing 1383 patients and 4 articles including 536 patients were enrolled. We found that low expression status of circMTO1 was significantly related to big tumor size (OR=2.11, 95% CI: 1.26-3.56, P<0.05), poor differentiation tumors (OR=2.09, 95% CI: 1.46-2.98, P<0.05), OS (HR=2.02, 95% CI: 1.63-2.50, P<0.05), disease-free survival (DFS) (HR=1.83, 95% CI: 1.27-2.56, P<0.05) of cancers. Subgroup analysis indicated that low expression status of circMTO1 was correlated with OS, regardless of analysis method, cut-off value, case number and NOS score.

CONCLUSIONS

The low expression of circMTO1 may predict big tumor size, poor differentiation and worse outcome of cancer, presenting that circMTO1 may be a useful biomarker for prognosis of tumors.

Non-coding RNAs as potential biomarkers of gallbladder cancer

Gallbladder cancer (GBC) performs strongly invasive and poor prognosis, and adenocarcinoma is the most common histological type in it. Statistically, the 5-year survival rate of patients with advanced GBC is less than 5%. Such dismal outcome might be caused by chemotherapy resistance and native biology of tumor cells, regardless of emerging therapeutic strategies. Early diagnosis, depending on biomarkers, receptors and secretive proteins, is more important than clinical therapy, guiding the pathologic stage of cancer and the choice of medication. Therefore, it is in urgent need to understand the specific pathogenesis of GBC and strive to find promising novel biomarkers for early screening in GBC. Non-coding RNAs (ncRNAs), especially microRNAs (miRNAs, miRs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are confirmed to participate in and regulate the occurrence and development of GBC. Exceptionally, lncRNAs and circRNAs could act as competing endogenous RNAs (ceRNAs) containing binding sites for miRNAs and crosstalk with miRNAs to target regulatory downstream protein-coding messenger RNAs (mRNAs), thus affecting the expression levels of specific proteins to participate in and regulate the development and progression of GBC. It follows that ncRNAs may become promising biomarkers and potential therapeutic targets for GBC. In this review, we mainly summarize the recent research progress of miRNAs and lncRNAs in regulating the development and progression of GBC, chemoresistance, and predicting the prognosis of patients, and highlight the potential applications of the lncRNA/circRNA-miRNA-mRNA cross-regulatory networks in early diagnosis, chemoresistance, and prognostic evaluation, aiming to better understand the pathogenesis of GBC and develop new diagnostic and therapeutic strategies.

Circular RNAs play roles in regulatory networks of cell signaling pathways in human cancers

AIMS

Circular RNAs (circRNAs) are endogenous covalently closed non-coding RNAs produced by reverse splicing of linear RNA. These molecules are highly expressed in mammalian cells and show cell/tissue-specific expression patterns. They are also significantly dysregulated in various cancers and function as oncogenes or tumor suppressors. Emerging evidence reveals that circRNAs contribute to cancer progression via modulating different cell signaling pathways. Nevertheless, the functional significance of circRNAs in cell signaling pathways regulation is still largely elusive. Considering this, shedding light on the multi-pathway effects of circRNAs may improve our understanding of targeted cancer therapy. Here, we discuss how circRNAs regulate the major cell signaling pathways in human cancers.

MATERIALS AND METHODS

We adopted a systematic search in PubMed using the following MeSH terms: circRNAs, non-coding RNAs, lncRNAs, exosomal circRNAs, cancer, and cell signaling.

KEY FINDINGS

We discussed different roles of circRNAs during tumorigenesis in which circRNAs affect tumor development through activating or inactivating certain cell signaling pathways via molecular interactions using various signaling pathways. We also discussed how crosstalk between circRNAs and lncRNAs modulate tumorigenesis and provides a resource for the identification of cancer therapeutic targets.

SIGNIFICANCE

We here elucidated how circRNAs can modulate different cell signaling pathways and play roles in cancer. This can broaden our horizons toward introducing promising prognostic, diagnostic, and therapeutic targets.

circRNA Expression Pattern and circRNA-miRNA-mRNA Network in HCs, HSCs, and KCs of Murine Liver After Echinococcus multilocularis Infection

Caused by Echinococcus multilocularis (E. multilocularis), alveolar echinococcosis is reported every year around the world and severely threatens the safety of human beings and animals. However, the molecular interaction relationships between host and E. multilocularis still remains unclear. With multiple functions, circRNA plays a crucial role in regulating the development of a parasitic disease. With that in mind, the main purpose of this study was to reveal the circRNA expression profiles and circRNA-miRNA-mRNA network relationships in hepatocytes (HCs), hepatic stellate cells (HSCs), and Kupffer cells (KCs) of murine liver after E. multilocularis infection. After sequencing, 6,290 circRNAs were identified from 12 hepatic cell samples. Based on the subsequent analysis, 426 and 372 circRNAs were significantly different in HC expression at 2 and 3 months after E. multilocularis infection, and similar results were also demonstrated in HSCs (426 and 372 circRNAs) and KCs (429 and 331 circRNAs), respectively. Eight candidate circRNAs were randomly selected to identify the accuracy of the sequencing results by using qRT-PCR. Additionally, three circRNAs-miRNA-mRNA networks in HCs, HSCs, and KCs were constructed. Taken together, our study provided a systematic presentation of circRNAs in murine liver cells after E. multilocularis infection, and these networks are essential for research in circRNAs associated with E. multilocularis infection.

CircMTO1: A circular RNA with roles in the carcinogenesis

Circular RNAs (circRNAs) have a closed loop structure which endows them high stability. These transcripts are made through back splicing instead of classical splicing and are abundant in the human transcriptome. Recent advances in the development and implementation of high-throughput sequencing methods in cooperation with novel bioinformatics tools have shown contribution of circRNAs in the developmental processes, physiological settings and pathoetiology of cancers. CircMTO1 is a circRNA which was firstly identified as a down-regulated circRNA in hepatocellular carcinoma through circRNA profiling using microarray technique. Subsequent independent studies in lung adenocarcinoma, colorectal cancer, bladder cancer, glioblastoma, prostate cancer, osteosarcoma, gastric cancer and ovarian cancer have verified down-regulation of circMTO1 in neoplastic tissues compared with non-neoplastic ones. However, expression of circMTO1 has been found to be up-regulated in cervical and gallbladder cancers. miR-17, miR-9, miR-221, miR-6893, miR-92, miR-219a-5p, miR-337, miR-630, miR-3200-5p and miR-199a-3p have been shown to be sequestered by circMTO1. This circRNA can regulate activity of Notch, Wnt/β-Catenin, TGF-β/Smad, JAK1/STAT3 and AMPK signaling pathways. In the current study, we review the literature on the role of circMTO1 in the tumorigenesis.