Long noncoding RNA XIST regulates the EGF receptor to promote TGF-ß1-induced epithelial-mesenchymal transition in pancreatic cancer.

ABSTRACT

BACKGROUND: This study focuses on the lncRNA XIST (X inactive-specific transcript), an lncRNA involved in multiple human cancers, and investigates the functional significance of XIST and the molecular mechanisms underlying the epithelial-mesenchymal transition (EMT) in pancreatic cancer (PC). METHODS: Clinical specimens from 25 patients as well as 5 human PC cell lines were analyzed for XIST, YAP, and microRNA(miR)-34a by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. To investigate how XIST influences cell proliferation, invasiveness, and apoptosis in PC, we performed the CCK-8 assays, Transwell assays, and flow cytometry. Luciferase reporter assays, qRT-PCR, and Western blot were applied to prove that miR-34a directly binds to XIST. RESULTS: Up-regulation of XIST and Yes associated protein (YAP) and down-regulation of miR-34a were consistently observed in the clinical specimens and PC cell lines. Silencing XIST reduced the expression of YAP and suppressed transforming growth factor (TGF)-ß1-induced EMT, while over-expression of XIST increased the expression of YAP and promoted EMT. In addition, inhibition of epidermal growth factor receptor (EGFR) hampered the XIST-promoted EMT. The results from the luciferase reporter assays confirmed that miR-34a directly targets XIST and suggested that XIST regulates cell proliferation, invasiveness, and apoptosis in PC by sponging miR-34a. CONCLUSIONS: XIST promotes TGF-ß1-induced EMT by regulating the miR-34a-YAP-EGFR axis in PC.