Circular RNAs and human glioma

As a newly discovered type of RNA, circular RNAs (circRNAs) are widespread throughout the eukaryotic genome. The expression of circRNAs is regulated by both cis-elements and trans-factors, and the expression pattern of circRNAs is cell type- and disease-specific. Similar to other types of non-coding RNAs, functions of circRNAs are also versatile. CircRNAs have been reported previously to function as microRNA (miRNA) sponges, protein sponges, coding RNAs or scaffolds for protein complexes. Recently, several circRNAs have been reported to play important roles in human malignancies, including glioma. Here, we reviewed several reports related to circRNAs and glioma, as well as the potential diagnostic and therapeutic applications of circRNAs in brain cancer. In general, some circRNAs, such as circSMARCA5 and circCFH, are found to be expressed in a glioma-specific pattern, these circRNAs may be used as tumor biomarkers. In addition, some circRNAs have been found to play oncogenic roles in glioma (e.g., circNFIX and circNT5E), whereas others have been reported to function as tumor suppressors (e.g., circFBXW7 and circSHPRH). Furthermore, circRNA is a good tool for protein expression because of its higher stability compared to linear RNAs. Thus, circRNAs may also be an ideal choice for gene/protein delivery in future brain cancer therapies. There are some challenges in circRNA research in glioma and other diseases. Research related to circRNAs in glioma is comparatively new and many mysteries remain to be solved.