Circular RNA ciRS-7-A Promising Prognostic Biomarker and a Potential Therapeutic Target in Colorectal Cancer.

Colorectal cancer is one of the most common malignancies worldwide. Recently, a novel circular RNA, ciRS-7, was proposed to be a potential miR-7 sponge. As miR-7, a putative tumor-suppressor, regulates the expression of several important drivers of colorectal cancer, we analyzed the clinical significance of ciRS-7 in colorectal cancer patients. Initially, we evaluated the expression levels of ciRS-7 in a training cohort comprising of 153 primary colorectal cancer tissues and 44 matched normal mucosae. We subsequently confirmed its clinical relevance in an independent validation cohort ( = 165), and evaluated the effect of ciRS-7 on miR-7, and its target genes EGFR and RAF1. Functional analyses were performed in cell lines and an animal model to support clinical findings. Our data revealed that ciRS-7 was significantly upregulated in colorectal cancer tissues compared with matched normal mucosae ( = 0.0018), and its overexpression was associated with poor patient survival ( = 0.0224 and 0.0061 in the training and validation cohorts, respectively). Multivariate survival analysis revealed that ciRS-7 emerged as an independent risk factor for overall survival ( = 0.0656 and 0.0324 in the training and validation cohorts, respectively). Overexpression of ciRS-7 in HCT116 and HT29 cells led to the blocking of miR-7 and resulted in a more aggressive oncogenic phenotype, and ciRS-7 overexpression permitted the inhibition of miR-7 and subsequent activation of EGFR and RAF1 oncogenes. CiRS-7 is a promising prognostic biomarker in colorectal cancer patients and may serve as a therapeutic target for reducing EGFR-RAF1 activity in colorectal cancer patients. .