Oxidored-nitro domain containing protein 1 (NOR1) expression suppresses slug/vimentin but not snail in nasopharyngeal carcinoma: Inhibition of EMT in vitro and in vivo in mice

Oxidored-nitro domain containing protein 1 (NOR1) is a putative tumor suppressor gene. In this study, NOR1 expression was detected in NPC tissues and non-cancerous nasopharyngeal epithelium. The data showed that NOR1 protein was decreased in NPC tissues. Lost expression NOR1 protein was associated with poor overall and event-free survival of NPC patients. Overexpression of NOR1 in NPC cells resulted in a significant morphological change and decreased expression of epithelial-to-mesenchymal transition (EMT) mediators (e.g., slug and vimentin), but induced cytokeratin 13 expression. A nude mouse metastasis assay revealed that overexpression of NOR1 decreased NPC tumor cells metastasis capacity in vivo. Knockdown of NOR1 expression in HeLa cells was sufficient to abrogate epithelial traits and to enhance cell migration and invasion. Concomitant inhibition of slug or vimentin alleviated induction of EMT, migration or invasion by NOR1 siRNA in HeLa cells in vitro. In conclusion, the data from the current study suggest, for the first time, that NOR1 plays an important role in NPC in ex vivo, in vitro, and in vivo.