CircRNAs are a new type of endogenous ncRNAs, and are characterized by a covalently closed continuous loop structure having no 5′ terminal cap and 3′ ends. With the progression of RNA sequencing and the rapid growth of bioinformatics analyses, circRNAs were identified across a broad range of organisms from eukaryotes, prokaryotes, microbes and viruses. Growing evidence suggests that circRNAs are found to impact several pathological and physiological processes as either tumor suppressor genes or oncogenes, and play multiple biological functions in both occurrence and development of many diseases, especially in cancers. A recently identified a circRNA, circFoxo3, were found to be closely associated with different cancers. Therefore, it seems that further research on circFoxo3 could facilitate the diagnosis and treatment of cancers. The current review summarized the characteristics, biogenesis and function of circRNAs and focused on the latest advance concerning the roles of circFoxo3 research and their potential to be used as a promising therapeutic targets and diagnostic biomarkers. [ABSTRACT FROM AUTHOR]