Underlying metastasis mechanism and clinical application of exosomal circular RNA in tumors (Review)

Abstract

Circular RNA (circRNA) is a long non-coding RNA molecule with a closed loop structure lacking a 5'cap and 3'tail. circRNA is stable, difficult to cleave and resistant to RNA exonuclease or RNase R degradation. circRNA molecules have several clinical applications, especially in tumors. For instance, circRNA may be used for non-invasive diagnosis, therapy and prognosis. Exosomes play a crucial role in the development of tumors. Exosomal circRNA in particular has led to increased research interest into tumorigenesis and tumor progression. Additionally, exosomal circRNA plays a role in cell-cell communication. Exosomal circRNA facilitates tumor metastasis by altering the tumor microenvironment and the pre-metastatic niche. Additionally, studies have revealed the mechanism by which exosomal circRNA affects malignant progression through signal transduction. Moreover, exosomal circRNA promotes tumor metastasis by regulating gene expression, RNA transcription and protein translation. In this review, the biological features and clinical application of exosomal circRNA are described, highlighting the underlying mechanisms through which they regulate tumor metastasis. The application of circRNA as clinical diagnostic biomarkers and in the development of novel therapeutic strategies is also discussed.

Circular RNAs in hepatocellular carcinoma: Recent advances

“…Compared with other types of competing endogenous RNAs, circRNAs have the following advantages. First, circRNAs are not easily degraded by RNA enzymes (RNase or RNA exonucleases)[ 21 , 22 ], which makes the circRNA structure stable and enables the possibility to stably inhibit the performance of miRNA function, with a stronger adsorption capacity for miRNAs than linear mRNAs and long noncoding RNAs. Second, existing studies have shown that the majority of circRNAs are highly expressed and that they can contain substantial miRNA response elements in a single molecule[ 23 - 25 ]; therefore, circRNAs are able to instantly bind or release large amounts of miRNAs to efficiently exert their regulatory roles.…”

Roles and mechanisms of CircRNAs in ovarian cancer

“…CircRNAs are mainly produced by exon cyclization, and while some circRNAs can also be derived from introns, antisense RNAs and 5′ or 3′ untranslated or intergenic genomic regions ( Guo et al, 2022 ). Sanger first identified the structural characteristics of circRNAs, which consist of a single-stranded, highly stable and closed loop structure lacking a 5’cap or 3’poly-A tail ( Wei et al, 2021 ). Unlike conventional forward splicing, circRNAs originate from the same precursor as linear RNA transcriptsto form circular RNAs, which is named as back-splicing ( Vromman et al, 2021 ).…”

Comprehensive circular RNA expression profile of lung adenocarcinoma with bone metastasis: Identification of potential biomarkers

“…Compared to miRNAs, circRNAs are more stable and not easily degraded by exonucleases. CircRNAs are involved in various cancer-related physiological cellular processes and are recognized as potential biomarkers in cancer metastasis ( Li and Yang, 2021 ; Wei et al, 2021 ; Yarmishyn et al, 2022 ).…”