Circular RNAs (circRNAs), a group of non-coding RNA characterized by the presence of covalent bonds linking 3′ and 5′ ends, act as miRNA sponges to participate in the tumorigenesis. Being stable, conserved and cell- or tissue-specific, circRNAs have shown their potentials as molecular markers for cancer. Convenient and noninvasive approaches may be developed based on the roles of circRNAs to diagnose or predict the prognosis of tumors. Although most of the potential mechanisms are not entirely clear, circRNAs have shown a universal and critical role in regulating cellular processes of cancers. This review summarized the classification, formation, characteristics, detection, and biological functions of circRNAs. We proposed the possibility of using circRNAs as biomarkers for cancer diagnosis, treatment and prognosis.

环状RNA（circRNA）是一组非编码RNA，其特征在于存在连接3'和5'末端的共价键，它们充当miRNA海绵，参与肿瘤发生。circRNA稳定，保守且具有细胞或组织特异性，已显示出其潜在的癌症分子标记物。可以基于circRNA在诊断或预测肿瘤预后中的作用，开发出便利且非侵入性的方法。尽管大多数潜在机制尚不完全清楚，但circRNA在调节癌症的细胞过程中已显示出普遍而关键的作用。这篇综述总结了circRNA的分类，形成，特征，检测和生物学功能。我们提出了使用circRNAs作为生物标志物进行癌症诊断，治疗和预后的可能性。