环状RNA在肝细胞癌中的作用及机制

肝细胞癌（hepatocellular carcinoma，HCC）治疗困难、预后很差，是肿瘤相关死亡中的第4大癌症，严重危害人类生命健康，但其具体发病机制却仍未完全阐明。因此，探索能调控肝细胞癌发生发展，作为肝细胞癌的诊断标志物或能预测患者预后的关键分子仍十分必要。环状RNA是前体mRNA通过反向剪接产生的由3′, 5′ 磷酸二酯键首尾连接形成的共价闭合环状结构，主要有外显子circRNA（exonic circRNA，ecircRNA）、环状内含子RNA（circular intronic RNA，ciRNA）及外显子 内含子circRNA（exon-intron circRNA，EIciRNA）三大类。由于环状RNA具有普遍性、高度保守性和稳定性，其可以参与多种癌症的发生发展过程，并且可作为肿瘤的早期诊断标志物及预后因子，因此，这是一类新型且非常有潜力应用于临床诊治各阶段的分子。近年来，有大量关于环状RNA与肝细胞癌的研究。这些研究表明，环状RNA在肝细胞癌发生发展进程中发挥的作用十分重要，并且其机制多样。因此，本文主要关注环状RNA在肝细胞癌中的最新进展，总结不同环状RNA分子对于肝细胞癌细胞恶性表型、肿瘤干细胞及肿瘤微环境中免疫细胞的作用，以及其在肝细胞癌临床转移、分期、诊断、预后等各阶段中发挥的功能及其具体作用机制。此外，本文还提出了目前研究中存在的一些问题和不足，以期为未来的研究提供一些新的思路及策略。

The Role and Mechanism of Circular RNAs in epatocellular Carcinoma

Hepatocellular carcinoma (HCC), which is difficult to treat and has a poor prognosis, is the fourth leading cause of cancer-related death and seriously harmful to human life and health, but its specific pathogenesis has not been fully elucidated. Therefore, it is still necessary to explore the key molecules that can regulate the development of HCC, as a diagnostic marker of HCC or predict the prognosis of patients. Circular RNA (circRNA) is a covalent closed ring structure formed by back splicing of precursor mRNA, which mainly includes exonic circRNA (ecircRNA) and circular intronic RNA (ciRNA) and exon-intron circRNA (EIciRNA). Because of its universality, highly conservatism and stability, circular RNAs can be involved in the occurrence and development of many kinds of cancer, and can be used as a marker for early diagnosis and prognosis. Therefore, this is a new class of molecules with great potential for clinical diagnosis and treatment. In recent years, there have been a lot of studies on the role of circular RNAs in HCC. These studies show that circular RNAs play a very important role in the development of HCC, and its mechanisms are diverse. Therefore, this review mainly focuses on the latest progress of circular RNAs in HCC, and summarizes the effects of different circular RNA molecules on the malignant phenotypes of HCC cells, tumor stem cells and immune cells in tumor microenvironment, as well as its functions in the clinical metastasis, staging, diagnosis and prognosis of HCC and correlated mechanisms. In addition, this review also presents the problems and deficiencies in the current research, in order to provide some new ideas and strategies for future research.