Circular RNAs (circRNAs) are a special class of non-coding RNAs that are widely expressed in tissues and cells. Owing to their lack of a 5'-cap and 3'-polyadenylated [poly(A)] tail, they are more structurally stable and difficult to degrade compared with linear RNA. Numerous studies published recently have suggested that circRNAs can encode peptides or proteins through cap-independent translation mechanisms and participate in the occurrence and development of cancer. In the present review, the translation mechanism underlying the encoding of proteins by circRNAs, the biological information tools that are available for predicting translation, and the identification and verification of their translational abilities are summarized and analyzed. Finally, the mechanisms associated with circRNA-encoded proteins or polypeptides in various types of cancer are summarized. In this review and its discussion on circRNAs and their coding function, we hope to provide novel perspectives and possibilities for the treatment of cancer as knowledge in this area is added to and developed in the future. Contents 1. Introduction 2. Translational mechanisms of circRNAs 3. Bioinformatics tools for the analysis of circRNA-encoded proteins 4. Role of circRNA-encoded proteins in cancer 5. Concluding remarks

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