The control of tumor progression by circular RNAs: novel prognostic and therapeutic insights resulting from the analysis of the circAGO2/human antigen R complex

Circular RNAs (circRNAs) represent a relatively novel class of non-coding RNA (ncRNA) characterized by a covalently bound loop (1). Due to their circular structure, circRNAs are very stable and resistant to the action of exonucleases and this characteristic distinguishes them from the other linear RNAs (2). They belong to the largest class of long ncRNA (lncRNA), and consist of several hundred nucleotides; they are endogenous, abundantly expressed, conserved and able to perform own peculiar functions (3,4).