CircFADS2: A potential prognostic biomarker of colorectal cancer
Authors: Xiao Yi-Sheng , Tong Hua-Zhang , Yuan Xi-Hong , Xiong Chang-Hui , Xu Xiao-Yang , Zeng Yuan-Feng 
Published: June 2020

Recent studies have displayed that circular RNA plays a key regulatory role in tumorigenesis and development. However, evidence supporting the critical role of circular RNA in the prognosis of colorectal cancer (CRC) is still limited. This study was designed to screen and identify novel circular RNA biomarkers in CRC. The microarray analysis of circular RNA expression profile was performed in three matched CRC and normal tissues. Compared with normal mucosa, a total of 208 differentially expressed circular RNAs were found in CRC, of which 95 were upregulated and 113 were downregulated. Then, the top 10 circular RNAs with the most significant differential expression were selected for verification by quantitative polymerase chain reaction (qPCR) in the above samples. The results of qPCR basically coincided with the findings of microarray analysis. The hsa_circ_022382 expression was the most significant upregulation in CRC among the 10 circular RNAs validated by qPCR. Because hsa_circ_022382 is derived from the human FADS2 gene, we named it circFADS2. Next, the increased expression of circFADS2 was further confirmed by qPCR, and its correlation with clinicopathologic parameters was analyzed in 200 CRC tissues. Herein, the expression of circFADS2 was shown to increase in 187 cases and decrease in 13 cases of CRC, and the elevated circFADS2 expression was closely related to the size, differentiation, infiltration depth, lymphatic and distant metastasis, and tumor/node/metastasis (TNM) stage of CRC. The survival analyses by Kaplan–Meier method demonstrated that patients with higher circFADS2 expression levels had shorter overall survival time and vice versa. Cox regression and area under ROC curve analyses revealed that the circFADS2 expression may be a promised biomarker for prognosis of CRC patients and had better prediction value when combined with TNM stage. In conclusion, our study identifies circFADS2 as an oncogenic biomarker and a potential prognostic factor in CRC. Impact statement Colorectal cancer (CRC) is the third most common malignancy worldwide with the second highest mortality rate. Although multidisciplinary cooperative therapies are helpful for improving the survival of CRC patients, the prognosis remains poor. Therefore, it is imperative to seek new biomarkers for the development of individualized treatment for each CRC patient. Circular RNA, an endogenous transcript with specific covalent closed loop, exhibits higher stability, conservation and expression abundance than the corresponding linear component and thus may be utilized as a promised biomarker. Although the majority of studies have focused on circular RNA expression profiling in various types of cancers, evidence supporting their critical role in the diagnosis and prognosis of CRC is limited. This study aimed to screen and identify novel circular RNA biomarkers of CRC by chip analysis and qPCR verification, and to highlight their potential as targets for CRC prognosis, and therapy.