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Background/Aims: Our study aims to investigate the role, effect and mechanisms of ESRP1 (epithelial splicing regulatory protein 1) in epithelial-mesenchymal transition (EMT) in epithelial ovarian cancer (EOC). Methods: Microarray and immunohistochemical analysis of ESRP1 expression were performed in EOC cases. The correlations between ESRP1 expression and clinical factors on EOC were assessed. Lentivirus-mediated RNA interference and EGFP vector which contains ESRP1 gene were used to down-regulate and up-regulate ESRP1 expression in human EOC cell lines. Roles of ESRP1 in cell growth, migration and invasion of EOC cells were also measured by Cell Counting Kit-8 and Transwell systems in vitro and by a nude mice intraperitoneal transplantation model in vivo. Results: By the analysis of Gene Expression Omnibus (GEO) (p<0.05) and our own microarray data (p<0.001), ESRP1 expression in EOC was significantly different from normal ovarian tissue. It was abundant in the nuclei of cancer cells and in malignant lesions. However, it was weakly expressed or negative in both normal and benign lesions. High ESRP1 expression in EOC was associated with poor clinical outcomes. Decreased ESRP1 expression significantly increased cell migration and invasion both in vivo and in vitro. Snail strongly repressed ESRP1 transcription through binding to the ESRP1 promoter in EOC cells. Furthermore, ESRP1 regulated the expression of CD44s. Down-regulated ESRP1 resulted in an isoform switching from CD44v to CD44s, which modulated epithelial-mesenchymal transition (EMT) program in EOC. Up-regulatin of ESRP1 was detected in mesenchymal to epithelial transition (MET) in vivo. Conclusions: ESRP1 regulates CD44 alternative splicing during the EMT process which plays an important role in EOC carcinogenesis. In addition, ESRP1 is associated with disease prognosis in EOC.Jie Tang, MD, Ph.D, Professor 283 Tongzipo Road, Yuelu District,

Background: Ovarian cancer is the third most common gynecological cancer in the world but the leading cause of death among gynecological malignancies. Epithelial splicing regulatory protein-1 (ESRP1), a key negative splicing regulator in epithelial-mesenchymal transition (EMT), has been proven to be overexpressed and may plays a role in epithelial ovarian cancer (EOC) progression. However, the functional roles of ESRP1 and the underlying mechanisms in this process still remain unclear. Methods: Tumor invasion, migration, colony formation and animal experiments were used to study the malignant biological behavior of ESRP1. A vector-based system expressing circ-0005585 was established to investigate circRNA as a microRNAs sponge. RNA-Seq and cytoskeleton staining explored underlying mechanisms of ESRP1. Results: Our results demonstrated that circ-0005585 regulates ESRP1 overexpression via sponging miR-23a/b and miR-15a/15b/16. Overexpression of ESRP1 suppresses EOC cell migration, but promotes colonization and drives a switch from mesenchymal to epithelial phenotype (MET) in association with actin cytoskeleton reorganization, mainly by alternative splicing EPB41L5 and RAC1. Furthermore, we have shown that high ESRP1 expression may be associated with immune-suppression in tumor immune microenvironment in vivo. Conclusions: ESRP1 overexpression promotes MET status and correlates with actin cytoskeleton reorganization in EOC. ESRP1 plays an important role in EOC colonization. In addition, a miRs panel from two miR families can inhibit ESRP1, may provide an innovative approach for cancer theranostics.