Circular RNAs in Cancer

Abstract

Circular RNAs (circRNAs) are a class of single-stranded closed RNA molecules that are formed by precursor mRNA back-splicing or skipping events of thousands of genes in eukaryotes as covalently closed continuous loops. High-throughput sequencing and bioinformatics approaches have uncovered the broad expression of circRNAs across species. Their high stability, abundance, and evolutionary conservation among species points to their distinct properties and diverse cellular functions as efficient microRNAs and protein sponges; they also play important roles in modulating transcription and splicing. Additionally, most circRNAs are aberrantly expressed in pathological conditions and in a tissue-specific manner such as development and progression of cancer. Herein, we highlight the characteristics, functions, and mechanisms of action of circRNAs in cancer; we also provide an overview of recent progress in the circRNA field and future application of circRNAs as cancer biomarkers and novel therapeutic targets.

Keywords: biogenesis; biological functions; cancer biomarkers; circular RNAs; exosomes; hallmarks of cancer; hematological malignancies; malignant tumors; oncogenic function; platelets.

Figure 1

The Experimental Scheme of the Study The discovery cohort was composed of healthy controls and cancer patients. circKLHDC10 and circCDYL are isolated from exosomes and profiles from RNA-seq analyses and a computational pipeline (see text for details).

Figure 2

The Role of circRNAs Is Correlated with Hallmarks of Cancer circRNAs have been indicated to contribute to various aspects of cancer progression (see text for details). (Adapted from Bach et al.⁹)