Circ5615 functions as a ceRNA to promote colorectal cancer progression by upregulating TNKS

Zhifei Ma,Xiang Li,Chencheng Han,Siwei Wang,Rong Yin,Lin Xu,Wenjia Xia,Panqi Fang,Liu Yang

doi:10.1038/s41419-020-2514-0

Abstract

Circular RNAs (circRNAs), non-coding RNAs generated by precursor mRNA back-splicing of exons, have been reported to fulfill multiple roles in cancer. However, the role of quite a lot circRNAs in colorectal cancer (CRC) remains mostly unknown. Herein, we explored the expression profiles of circRNAs in 5 paired samples of CRC patients by microarray and noted a circRNA, hsa_circ_0005615 (circ5615), was significantly upregulated in CRC tissues. Circ5615 was derived from exon 2 of NFATC3 and its upregulation was tightly correlated with higher T stage and poor prognosis in CRC patients. Studies in vitro and in vivo demonstrated that knockdown of circ5615 in cancer cells inhibited proliferation and cell cycle acceleration, while overexpression promoted malignant phenotypes. Mechanistically, RNA immunoprecipitation, biotin-coupled probe pull-down and luciferase reporter assays revealed circ5615 effectively bound to miR-149-5p and might play a role like miR-149-5p sponge. Additionally, tankyrase (TNKS), regulator of β-catenin stabilization, was identified as circ5615 downstream and the potential miR-149-5p targets by RNA-seq and bioinformatics analysis. We further verified the upregulation of β-catenin and cyclin D1 induced by circ5615. Our results indicated that circ5615 exerted oncogenic function as competing endogenous RNA (ceRNA) of miR-149-5p to release TNKS and activated Wnt/β-catenin pathway.

Highlights

Colorectal cancer (CRC) is the third most common cancer with over 1.8 million new cases in 2018 and the second leading cause of cancer-related death worldwide[1]
Our results revealed that circ5615 preferentially located in the cytoplasm of SW480 cells (Fig. 2d), which was identified by the fluorescence in situ hybridization (FISH) assay for circ5615 (Fig. 2e)
Circ5615 expression correlated with poor clinical outcome We explored the clinicopathologic significance of circ5615 using tissue microarray (TMA) constructed by 99 pairs of colorectal cancer (CRC) tissues and adjacent nontumor tissues

Summary

Introduction

Colorectal cancer (CRC) is the third most common cancer with over 1.8 million new cases in 2018 and the second leading cause of cancer-related death worldwide[1]. With further study of characterization and biology of circRNAs, it has been found that circRNAs generally exhibit cell-type-specific and tissue-specific patterns and are implicated in various diseases such as diabetes mellitus, cardiovascular diseases, and cancer[5]. Due to their circular structures being resistant to most RNA degradation machineries, circular RNAs are deemed to be stable and show bright prospects in clinical. It has been widely proposed that the circRNAs can act as competing endogenous RNA (ceRNA) for miRNAs through their binding sites and modulate the activity of miRNAs on target genes. CircRNAs might serve as a biomarker for prognosis predication[14]

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Results

Conclusion