Circular RNA in tumor metastasis

Circular RNAs (circRNAs) are a type of endogenous non-coding RNA that were discovered to regulate gene expression through multiple pathways. Metastasis remains one of the biggest obstacles in cancer treatment. In this review, we focus on circRNAs involved in cancer tumorigenesis and metastasis. We present recently identified tumor-related circRNAs and discuss their functioning in tumor progression and metastasis. These circRNAs are categorized into different functional mechanisms, including microRNA (miRNA) sponging, protein binding, regulation of host genes, translation of circRNAs, and exosomal circRNAs. Additionally, the indirect functions of circRNAs that regulate epithelial-mesenchymal transition and autophagy are also discussed. [Display omitted] Large numbers of differentially expressed circRNAs have been identified in tumors and metastasis. Gain-of-function and loss-of-function approaches have been developed to manipulate specific circRNA expression in order to modulate tumor development. circRNAs may be used as potential biomarkers for early diagnosis and may be targets for therapeutic strategies.