Circular RNAs in cholangiocarcinoma

Cholangiocarcinoma (CCA) is the most common primary biliary malignancy with an adverse prognosis. Although its incidence is relatively low, early diagnosis is difficult due to the lack of specific symptoms. Current treatment options for CCA are limited, resulting in a low curative rate. Circular RNAs (circRNAs) have become a new research hotspot in recent years, and they are frequently dysregulated in CCA and may become therapeutic targets and prognostic biomarkers of CCA. Accumulating evidence has demonstrated that numerous dysregulated circRNAs are vital players in the etiopathogenesis of CCA. Aberrant expression of specific circRNAs was correlated with unfavourable clinical characteristics in CCA. Many studies have found that circRNAs are involved in the progression and development of CCA through various mechanisms, including competitive inhibition of miRNAs via the competing endogenous RNA (ceRNA) network, interaction with RNA-binding proteins (RBPs), activation of cancer-related signalling pathways, and regulation of proteins and peptides. Additionally, some circRNAs are involved in the inflammatory microenvironment of CCA and play a crucial role in chemotherapy drug resistance. Thus, they are essential for the early diagnosis and prediction of CCA, and more attention should be given to the roles and mechanisms of circRNAs in CCA. In this review, we summarize the abnormal expression of circRNAs in CCA and the specific inflammatory microenvironment involved, as well as the roles and mechanisms of circRNAs in the occurrence and development of CCA. We also review the latest knowledge on circRNAs in CCA and discuss the challenges associated with the introduction of circRNAs into clinical practice and their potential clinical value.