Knockdown of Notch1 inhibits nasopharyngeal carcinoma cell growth and metastasis via downregulation of CCL2, CXCL16, and uPA

Abstract

Notch pathway is a highly conserved cell signaling system that plays very important roles in controlling multiple cell differentiation processes during embryonic and adult life. Multiple lines of evidence support the oncogenic role of Notch signaling in several human solid cancers; however, the pleiotropic effects and molecular mechanisms of Notch signaling inhibition on nasopharyngeal carcinoma (NPC) remain unclear. In this study, we evaluated Notch1 expression in NPC cell lines (CNE1, CNE2, SUNE1, HONE1, and HK1) by real-time quantitative PCR and Western blot analysis, and we found that CNE1 and CNE2 cells expressed a higher level of Notch1 compared with HONE1, SUNE1, and HK1 cells. Then Notch1 expression was specifically knocked down in CNE1 and CNE2 cells by Notch1 short hairpin RNA (shRNA). In Notch1 knockdown cells, cell proliferation, migration, and invasion were significantly inhibited. The epithelial-mesenchymal transition of tumor cells was reversed in Notch1-shRNA-transfected cells, accompanied by epithelioid-like morphology changes, increased protein levels of E-cadherin, and decreased expression of vimentin. In addition, knockdown of Notch1 markedly inhibited the expression of urokinase plasminogen activator (uPA) and its receptor uPAR, and chemokines C-C motif chemokine ligand 2 and C-X-C motif chemokine ligand 16, indicating that these factors are downstream targets of Notch1. Furthermore, deleting uPA expression had similar effects as Notch1. Finally, knockdown of Notch1 significantly diminished CNE1 cell growth in a murine model concomitant with inhibition of cell proliferation and induction of apoptosis. These results suggest that Notch1 may become a novel therapeutic target for the clinical treatment of NPC.