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Objective:Growing evidence indicates that FAT atypical cadherin 1 (FAT1) has aberrant genetic alterations and exhibits potential tumor suppressive function in esophageal squamous cell carcinoma (ESCC).However,the role of FAT1 in ESCC tumorigenesis remains not well elucidated.The aim of this study was to further investigate genetic alterations and biological functions of FAT1,as well as to explore its transcriptional regulation and downstream targets in ESCC.Methods:The mutations of FAT1 in ESCC were achieved by analyzing a combined study from seven published genomic data,while the copy number variants of FAT1 were obtained from an analysis of our previous data as well as of The Cancer Genome Arias (TCGA) and Cancer Cell Line Encyclopedia (CCLE) databases using the cBioPortal.The transcriptional regulation of FAT1 expression was investigated by chromatin immunoprecipitation (ChIP) and the luciferase reporter assays.In-cell west,West blot and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to assess the indicated gene expression.In addition,colony formation and Transwell migration/invasion assays were employed to test cell proliferation,migration and invasion.Finally,RNA sequencing was used to study the transcriptomes.Results:FAT1 was frequently mutated in ESCC and was deleted in multiple cancers.Furthermore,the transcription factor E2F1 occupied the promoter region of FAT1,and depletion of E2F1 led to a decrease in transcription activity and mRNA levels of FAT1.Moreover,we found that knockdown of FAT1 promoted KYSE30 and KYSE150 cell proliferation,migration and invasion;while overexpression of FAT1 inhibited KYSE30 and KYSE410 cell proliferation,migration and invasion.In addition,knockdown of FAT1 led to enrichment of the mitogen-activated protein kinase (MAPK) signaling pathway and cell adhesion process.Conclusions:Our data provided evidence for the tumor suppressive function of FAT1 in ESCC cells and elucidated the transcriptional regulation of FAT1 by E2F1,which may facilitate the understanding of molecular mechanisms of the progression of ESCC.