Editorial - 'Sponging' a carcinoma as a Circular RNA

CircRNA Biogenesis and miRNA Sponging CircularRNAs (circRNAs) are endogenous non-coding RNAs, stable, abundant, and conserved through evolution, regulating several physiological and pathological mechanisms, assuming an emerging pivotal role in biomedical sciences. CircRNAs have been reported in all eukaryotes known, including plants, yeast, fishes, worms and they are from 5-30% conserved in human and mice transcriptome. CircRNAs are covalently closed circular RNA molecules forming between a downstream 3? splice site and an upstream 5? splice site in a linear precursor mRNA and are transcribed by RNA polymerase II and originate from exons, introns, antisense, 5? or 3? untranslated and intergenic genomic regions1. The most important mechanism unfolding the biological function of circRNAs is the capacity to sponge microRNAs2. Sponging miRNAs, the circRNAs modulate the post-transcriptional regulation of mRNA gene target, inhibiting miRNA-mediated repression of translation. In addition, circRNAs compete with endogenous RNA molecules, associate and bind RNA-binding proteins, and tune splicing. CircRNAs are abundantly expressed in the brain and up to 50% they are expressed in a tissue-dependent manner, assuming a clinical importance in cancer pathogenesis and neurodegenerative diseases as valuable diagnostic biomarkers3. The circular RNA-miRNAs connection represents one of the most investigated research field in cancer translational medicine, opening a new therapeutic perspective.