Significance of Circular FAT1 as a Prognostic Factor and Tumor Suppressor for Esophageal Squamous Cell Carcinoma

Wataru Takaki,Kazuya Takabatake,Satoshi Kataoka,Kiyoshi Masuda,Hirotaka Konishi,Jun Shibamoto,Hitoshi Fujiwara,Hiroki Shimizu,Eigo Otsuji,Tomohiro Arita,Atsushi Shiozaki,Shuhei Komatsu,Katsutoshi Shoda,Hirotaka Furuke

doi:10.1245/s10434-021-10089-9

Abstract

BackgroundCircular RNA is a novel endogenous non-coding RNA with a stable loop structure, and theories for its biogenesis and usefulness as a biomarker in various cancers have been proposed. The present study investigated the significance of circular FAT1 (circFAT1) as a novel biomarker in esophageal squamous cell carcinoma (ESCC).MethodCircFAT1 expression levels were measured in ESCC cell lines and the effects of downregulating circFAT1 on cell migration and invasion were examined using a transwell assay. The functions of miR-548g, which will be sponged by circFAT1, were assessed. Furthermore, the expression of circFAT1 was evaluated in 51 radically resected ESCC tissue samples using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The relationships between circFAT1 expression, clinicopathological factors, and patient prognosis were analyzed.ResultsCircFAT1 expression levels were significantly lower in tumor tissue than in adjacent non-tumorous mucosal tissue (p = 0.01). The downregulation of circFAT1 expression promoted ESCC cell migration and invasive ability, but not proliferation. The expression of miR-548g was upregulated by the downregulation of circFAT1. The overexpression of miR-548g also promoted ESCC cell migration and invasion. Recurrence-free survival (p = 0.02) and cancer-specific survival (p = 0.04) rates were significantly higher in patients with elevated circFAT1 expression levels.ConclusionThe expression level of circFAT1 is a novel prognostic marker in ESCC patients. New treatment strategies may be developed using the tumor suppressive functions of circFAT1.

Highlights

Circular RNA is a novel endogenous noncoding RNA with a stable loop structure, and theories for its biogenesis and usefulness as a biomarker in various cancers have been proposed
The Sanger sequencing of PCR products confirmed the presence of the sequence containing the circFAT1 head-to-tail junction (Fig. 1b), and showed that the 30 and 50 ends of exon 2 formed a head-to-tail junction in esophageal squamous cell carcinoma (ESCC) cells
The results of quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses indicated that circFAT1 expression levels were significantly lower in ESCC cell lines than in normal cell lines (p = 0.01) (Fig. 1d)

Summary

Introduction

Circular RNA is a novel endogenous noncoding RNA with a stable loop structure, and theories for its biogenesis and usefulness as a biomarker in various cancers have been proposed. The present study investigated the significance of circular FAT1 (circFAT1) as a novel biomarker in esophageal squamous cell carcinoma (ESCC). CircFAT1 expression levels were measured in ESCC cell lines and the effects of downregulating circFAT1 on cell migration and invasion were examined using a transwell assay. The functions of miR-548g, which will be sponged by circFAT1, were assessed. The expression of circFAT1 was evaluated in 51 radically resected ESCC tissue samples using quantitative reverse transcription polymerase chain reaction (qRT-PCR). CircFAT1 expression levels were significantly lower in tumor tissue than in adjacent non-tumorous mucosal tissue (p = 0.01). The downregulation of circFAT1 expression promoted ESCC cell migration and

Methods

Results

Conclusion