Exosomal circRNAs: new players in colorectal cancer

Colorectal cancer (CRC) is one of the most malignant cancer types, characterized by elevated mortality rate and treatment resistance. Despite the progress achieved in the explanation of the molecular basis of the disease as well as introducing potential biomarkers in the clinical practice, further investigation is essential to identify innovative molecules that contribute to colorectal carcinogenesis. Circular RNAs (circRNAs) are a novel and unexplored RNA type, associated with various human pathological conditions. Recently, circRNAs have been identified to be enriched and stable in exosomes and can exert their functions when exosomes reach neighboring or distant cells. Increasing evidence indicates that these so called exosomal circRNAs (exo-circRNAs) act as signaling molecules to regulate cancer proliferation, metastasis, and sensitivity to radio- and chemotherapy. This review aims to discuss the latest progress in exo-circRNAs studies in CRC with an emphasis on their potential as promising diagnostic molecular markers and therapeutic targets.