Circular RNA (circRNA) is a class of single-stranded molecules with tissue/development-specific expression patterns. Unlike linear RNA, circRNA forms a covalently closed loop produced from ‘back-splicing’ of primary transcripts, conferring on them inherent resistance to exonucleolytic RNA decay. Increasing evidence demonstrates that many circRNAs exert important biological functions by acting as miRNA inhibitors (‘sponges’), protein ‘decoys’, or by encoding small peptides. Importantly, circRNAs are aberrantly expressed in cancer and play indispensable oncogenic or tumor suppressive roles during tumor development and progression. In this review, we summarize the biogenesis, turnover, and involvements of circRNAs in cancer and also discuss their potential as diagnostic biomarkers or therapeutic targets.

环状RNA（circRNA）是一类具有组织/发育特异性表达模式的单链分子。与线性RNA不同，circRNA形成一个共价的闭合环，由初级转录本的“反向剪接”产生，赋予它们对核酸外切RNA降解的固有抗性。越来越多的证据表明，许多circRNA通过充当miRNA抑制剂（“海绵”），蛋白质“诱饵”或编码小肽发挥重要的生物学功能。重要的是，circRNA在癌症中异常表达，并在肿瘤的发展和进程中起着不可或缺的致癌或抑癌作用。在这篇综述中，我们总结了circRNA的生物发生，更新和参与癌症，并讨论了其作为诊断性生物标志物或治疗靶标的潜力。