CircPTK2 inhibits the tumorigenesis and metastasis of gastric cancer by sponging miR-134-5p and activating CELF2/PTEN signaling

Circular RNAs: Epigenetic regulators of PTEN expression and function in cancer

Epigenetic regulation of gene expression, without altering the DNA sequence, is involved in many normal cellular growth and division events, as well as diseases such as cancer. Epigenetics is no longer limited to DNA methylation, and histone modification, but regulatory non-coding RNAs (ncRNAs) also play an important role in epigenetics. Circular RNAs (circRNAs), single-stranded RNAs without 3' and 5' ends, have recently emerged as a class of ncRNAs that regulate gene expression. CircRNAs regulate phosphatase and tensin homolog (PTEN) expression at various levels of transcription, post-transcription, translation, and post-translation under their own regulation. Given the importance of PTEN as a tumor suppressor in cancer that inhibits one of the most important cancer pathways PI3K/AKT involved in tumor cell proliferation and survival, significant studies have been conducted on the regulatory role of circRNAs in relation to PTEN. These studies will be reviewed in this paper to better understand the function of this protein in cancer and explore new therapeutic approaches.

CircRNAs in Alzheimer's disease: What are the prospects?

Circular RNAs (circRNAs) is a fascinating covalently closed circular non-coding RNA that is abundantly present in the transcriptome of eukaryotic cells. Its versatile nature allows it to participate in a multitude of pathological and physiological processes within the organism. One of its crucial functions is acting as a microRNA sponge, modulating protein transcription levels, and forming interactions with essential RNA-binding proteins. Remarkably, circRNAs demonstrates a specific enrichment in various vital areas of the brain, including the cortex, hippocampus, white matter, and photoreceptor neurons, particularly in aging organisms. This intriguing characteristic has led scientists to explore its potential as a significant biological marker of neurodegeneration, offering promising insights into neurodegenerative diseases like Alzheimer's disease (AD). In AD, there has been an interesting observation of elevated levels of circRNAs in both peripheral blood and synaptic terminals of affected individuals. This intriguing finding raises the possibility that circRNAs may have a central role in the initiation and progression of AD. Notably, different categories of circRNAs, including HDAC9, HOMER1, Cwc27, Tulp4, and PTK2, have been implicated in driving the pathological changes associated with AD through diverse mechanisms. For instance, these circRNAs have been demonstrated to contribute to the accumulation of beta-amyloid, which is a hallmark characteristic of AD. Additionally, these circRNAs contribute to the excessive phosphorylation of tau protein, a phenomenon associated with neurofibrillary tangles, further exacerbating the disease. Moreover, they are involved in aggravating neuroinflammation, which is known to play a critical role in AD's pathogenesis. Lastly, these circRNAs can cause mitochondrial dysfunction, disrupting cellular energy production and leading to cognitive impairment. As researchers delve deeper into the intricate workings of circRNAs, they hope to unlock its full potential as a diagnostic tool and therapeutic target for neurodegenerative disorders, paving the way for innovative treatments and better management of such devastating conditions.

Role of CELF2 in ferroptosis: Potential targets for cancer therapy (Review)

Ferroptosis is a novel form of regulated cellular necrosis that plays a critical role in promoting cancer progression and developing drug resistance. The main characteristic of ferroptosis is iron‑dependent lipid peroxidation caused by excess intracellular levels of reactive oxygen species. CUGBP ELAV‑like family number 2 (CELF2) is an RNA‑binding protein that is downregulated in various types of cancer and is associated with poor patient prognoses. CELF2 can directly bind mRNA to a variety of ferroptosis control factors; however, direct evidence of the regulatory role of CELF2 in ferroptosis is currently limited. The aim of the present review was to summarise the findings of previous studies on CELF2 and its role in regulating cellular redox homeostasis. The present review may provide insight into the possible mechanisms through which CELF2 affects ferroptosis and to provide recommendations for future studies.

Circular RNA protein tyrosine kinase 2 aggravates pyroptosis and inflammation in septic lung tissue by promoting microRNA-766/eukaryotic initiation factor 5A axis-mediated ATP efflux

PURPOSE

Sepsis is characterized by an acute inflammatory response to infection, often with multiple organ failures, especially severe lung injury. This study was implemented to probe circular RNA (circRNA) protein tyrosine kinase 2 (circPTK2)-associated regulatory mechanisms in septic acute lung injury (ALI).

METHODS

A cecal ligation and puncture-based mouse model and an lipopolysaccharides (LPS)-based alveolar type II cell (RLE-6TN) model were generated to mimic sepsis. In the two models, inflammation- and pyroptosis-related genes were measured.

RESULTS

The degree of lung injury in mice was analyzed by hematoxylin and eosin (H&E) staining and the apoptosis was by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining. In addition, pyroptosis and toxicity were detected in cells. Finally, the binding relationship between circPTK2, miR-766, and eukaryotic initiation factor 5A (eIF5A) was detected. Data indicated that circPTK2 and eIF5A were up-regulated and miR-766 was down-regulated in LPS-treated RLE-6TN cells and lung tissue of septic mice. Lung injury in septic mice was ameliorated after inhibition of circPTK2.

CONCLUSIONS

It was confirmed in the cell model that knockdown of circPTK2 effectively ameliorated LPS-induced ATP efflux, pyroptosis, and inflammation. Mechanistically, circPTK2 mediated eIF5A expression by competitively adsorbing miR-766. Taken together, circPTK2/miR-766/eIF5A axis ameliorates septic ALI, developing a novel therapeutic target for the disease.

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.