54845

ESRP1

Alternative splicing achieves coordinated changes in post-transcriptional gene expression programmes through the activities of diverse RNA-binding proteins. epithelial splicing regulatory proteins 1 and 2 (ESRP1 and ESRP2) are cell-type-specific regulators of transcripts that switch splicing during the epithelial-mesenchymal transition (EMT). To define a comprehensive programme of alternative splicing that is regulated during the EMT, we identified an extensive ESRP-regulated splicing network of hundreds of alternative splicing events within numerous genes with functions in cell-cell adhesion, polarity, and migration. Loss of this global ESRP-regulated epithelial splicing programme induces the phenotypic changes in cell morphology that are observed during the EMT. Components of this splicing signature provide novel molecular markers that can be used to characterize the EMT. Bioinformatics and experimental approaches revealed a high-affinity ESRP-binding motif and a predictive RNA map that governs their activity. This work establishes the ESRPs as coordinators of a complex alternative splicing network that adds an important post-transcriptional layer to the changes in gene expression that underlie epithelial-mesenchymal transitions during development and disease.

A subset of Non-Small Cell Lung Carcinoma (NSCLC) carries chromosomal rearrangements involving the Anaplastic Lymphoma Kinase (ALK) gene. ALK-rearranged NSCLC are typically adenocarcinoma characterized by a solid signet-ring cell pattern that is frequently associated with a metastatic phenotype. Recent reports linked the presence of ALK rearrangement to an epithelial-mesenchymal transition (EMT) phenotype in NSCLC, but the extent and the mechanisms of an ALK-mediated EMT in ALK-rearranged NSCLC are largely unknown. We found that the ALK-rearranged H2228 and DFCI032, but not the H3122, cell lines displayed a mesenchymal phenotype. In these cell lines, oncogenic ALK activity dictated an EMT phenotype by directly suppressing E-cadherin and up-regulating vimentin expression, as well as expression of other genes involved in EMT. We found that the epithelial splicing regulatory protein 1 (ESRP1), a key regulator of the splicing switch during EMT, was repressed by EML4-ALK activity. The treatment of NSCLC cells with ALK tyrosine kinase inhibitors (TKIs) led to up-regulation of ESRP1 and E-cadherin, thus reverting the phenotype from mesenchymal to epithelial (MET). Consistently, ESRP1 knock-down impaired E-cadherin up-regulation upon ALK inhibition, whereas enforced expression of ESRP1 was sufficient to increase E-cadherin expression. These findings demonstrate an ALK oncogenic activity in the regulation of an EMT phenotype in a subset of NSCLC with potential implications for the biology of ALK-rearranged NSCLC in terms of metastatic propensity and resistance to therapy.

Increased expression of zinc finger E-box binding homeobox 1 (ZEB1) is associated with tumor grade and metastasis in lung cancer, likely due to its role as a transcription factor in epithelial-to-mesenchymal transition (EMT). Here, we modeled malignant transformation in human bronchial epithelial cells (HBECs) and determined that EMT and ZEB1 expression are early, critical events in lung cancer pathogenesis. Specific oncogenic mutations in TP53 and KRAS were required for HBECs to engage EMT machinery in response to microenvironmental (serum/TGF-beta) or oncogenetic (MYC) factors. Both TGF-beta- and MYC-induced EMT required ZEB1, but engaged distinct TGF-beta-dependent and vitamin D receptor-dependent (VDR-dependent) pathways, respectively. Functionally, we found that ZEB1 causally promotes malignant progression of HBECs and tumorigenicity, invasion, and metastases in non-small cell lung cancer (NSCLC) lines. Mechanistically, ZEB1 expression in HBECs directly repressed epithelial splicing regulatory protein 1 (ESRP1), leading to increased expression of a mesenchymal splice variant of CD44 and a more invasive phenotype. In addition, ZEB1 expression in early stage IB primary NSCLC correlated with tumor-node-metastasis stage. These findings indicate that ZEB1-induced EMT and associated molecular changes in ESRP1 and CD44 contribute to early pathogenesis and metastatic potential in established lung cancer. Moreover, TGF-beta and VDR signaling and CD44 splicing pathways associated with ZEB1 are potential EMT chemoprevention and therapeutic targets in NSCLC.

epithelial-to-mesenchymal transition (EMT) has been shown to be associated with tumor progression and metastasis. During this process in breast cancer, a crucial role is played by alternative splicing systems. To identify a new early prognostic marker of metastasis, we evaluated EMT-related gene expression in breast cell lines, and in primary tumor tissue from 31 patients with early breast cancer, focusing our attention on EMT-related splicing factors ESRP1, ESRP2 and RBFOX2. Results showed that the expression patterns of these genes were indicative of the onset of EMT in in-vitro models, but not in tissue samples. However, the ratio between ESRP1 or ESRP2 and RBFOX2 significantly decreased during EMT and positively correlated with the EMT-specific phenotype in cell models, representing a promising prognostic markers. Low ESRP1/RBFOX2 ratio value was associated with a higher risk of metastasis (p < 0.005) in early breast cancer patients, regardless other clinical features. A cut-off of ratio of 1.067 was determined by ROC curve analysis (AUC 0.8375; 95% CI 0.6963-0.9787). Our study show evidence that a decrease in this ratio correlates with cancer progression. The results provide a rationale for using ESRP1/RBFOX2 ratio as a new prognostic biomarker for the early prediction of metastatic potential in breast cancer.

Increased metastasis and a precipitous recurrence contribute to the lethality of ovarian cancer (OC). Several molecular mechanisms including aberrant-splicing have been closely associated with the extent of cancer progression. Numerous gene transcripts are differentially spliced in cancer cells, CD44 being one of them. CD44 splice isoforms contribute to the aggressiveness and gain of stem-like properties in different cancer types, but their role in ovarian cancer remains to be elucidated. We observed augmented CD44 levels in human ovarian cancer patient samples correlated with enhanced expression of the mesenchymal spliced variant CD44s (standard) and a concurrent decrease in the epithelial variants (CD44v). Moreover, CD44s was upregulated upon TGFbeta1-induced EMT, which was mediated through the downregulation of the splicing factor, ESRP1. Furthermore, overexpression of this mesenchymal isoform in the OC cells induced EMT and invasion, followed by the gain of stem-like characteristics and chemoresistance. Since all these phenomena render lethality to this disease type, CD44s can be attributed for playing a major role in deregulated-splicing mediated ovarian cancer progression.CI - (c) 2017 Wiley Periodicals, Inc.

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.CI - (c) 2017 The Author(s). Published by S. Karger AG, Basel.