Crosstalk between circular RNAs and microRNAs in tumorigenesis

Liver cancer is the fifth most common cancer worldwide and the second leading cause of cancer-related mortality, resulting in approximately 750,000 deaths annually (1). Hepatocellular carcinoma (HCC) accounts for 70–90% of all cases of liver cancer (2). Although significant advances have been made toward understanding its causal mechanisms, the 5-year risk of HCC recurrence still exceeds 70% (3). The low survival rate of HCC patients is widely attributed to postsurgical recurrence and metastases of primary tumours (1). Furthermore, the progression and development of HCC involve multiple genes and pathways that are induced by cellular conditions such as oxidative stress and a tumour microenvironment (4). In addition, hypoxia and inflammation act in concert with various molecular events. There is an urgent need for effective strategies to screen for and detect early-stage HCC, thereby improving the long-term survival of HCC patients.