<p>PVT1 Mediates Cell Proliferation, Apoptosis and Radioresistance in Nasopharyngeal Carcinoma Through Regulating miR-515-5p/PIK3CA Axis</p>
Yanyan Han, Fang Li, Jun Xie, Yi Wang, Hua Zhang
Abstract
Background: Radioresistance greatly hinders the treatment of nasopharyngeal carcinoma (NPC). Long noncoding RNA (lncRNA) plasmacytoma variant translocation 1 ( PVT1 ) has been corroborated to participate in diverse cancers, including NPC. Our aim was to investigate the underlying molecular mechanism of PVT1 in NPC radioresistance. Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to measure the expression levels of PVT1 , microRNA (miR)-515-5p and phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha ( PIK3CA ) in NPC tissues and cells. Cell counting kit-8 (CCK8) assay, colony formation assay and flow cytometry assay were employed to detect cell proliferation, radiosensitivity and apoptosis, respectively. The protein levels of Cyclin D1, B-cell lymphoma 2 associated X (Bax), Cleaved-caspase-3, PIK3CA, protein kinase B (AKT) and phosphorylated AKT (p-AKT) in samples were measured by Western blot. The starBase was used to predict the binding sites between miR-515-5p and PVT1 or PIK3CA . Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the interaction. Xenograft tumor model was established to investigate the biological role of PVT1 in vivo. Results: The levels of PVT1 and PIK3CA were upregulated in NPC tissues and cells, opposite to the expression of miR-515-5p . Knockdown of PVT1 inhibited cell proliferation, radioresistance and promoted cell apoptosis in NPC cells. Meanwhile, PVT1 silencing downregulated Cyclin D1, and upregulated Bax and Cleaved-casp-3 in NPC cells after radiotherapy. Besides, miR-515-5p interacted with PVT1 and targeted PIK3CA in NPC cells. Further studies indicated that PVT1 regulated radioresistance via miR-515-5p/PIK3CA axis and modulated the AKT pathway by interacting with miR-515-5p . Moreover, knockdown of PVT1 suppressed tumor growth in vivo. Conclusion: Downregulation of PVT1 inhibited proliferation, radioresistance and promoted apoptosis by downregulating PIK3CA via sponging miR-515-5p in NPC cells. Keywords: NPC, PVT1, miR-515-5p, PIK3CA, radioresistance