Dear Editor, Cholangiocarcinoma (CCA) is an aggressive malignant tumor of the hepatobiliary system, mainly originating from the cholangiocytes of small intrahepatic bile ducts [1]. The overall survival of patients with CCA is still unfavorable [1]. Circular RNAs (circRNAs) are a type of non-coding RNAs with limited protein-coding capacity [2] and have shown to exert regulatory effects in multiple diseases by interacting with certain miRNAs to inhibit their expression and functions [3]. Emerging evidence indicates that circRNAs can directly bind to several RNA-binding proteins to execute their biological functions. Hence, determining the mechanisms underlying the progression of CCA and searching for new drugs from the perspective of circRNAs are imperative. Details regarding the methods of this work can be found in the Supplementary Materials. To unveil the dysregulated circRNAs in CCA, cancer, and noncancerous tissues from patients with CCA were subjected to circRNA microarray (Figure 1A). Then, eight up-regulated circR-NAs were detected in 15 paired CCA and adjacent noncancerous samples by quantitative real-time polymerase chain reaction (qRT-PCR). The results indicated that hsa_circRNA_104634 was the most up-regulated circRNA in the tumor samples (Figure 1B). Hsa_circRNA_104634 is located on chr8:62593526-62596747. The spliced sequence length of hsa_circRNA_104634 is 264 nt. The genomic structure of hsa_circRNA_104634 is looped by the exons 2, 3, and 4 of the aspartate β-hydroxylase (ASPH) gene