Nasopharyngeal carcinoma (NPC) is a unique subtype of head and neck cancer, with tendency to spread to regional lymph nodes and distant organs at early stage. Vimentin, a major cytoskeletal protein constituent of the intermediate filament, plays a critical role in the epithelial-mesenchymal transition. Overexpression of vimentin is considered to be a critical prerequisite for metastasis in numerous human cancers. Therefore, targeting vimentin for cancer therapy has gained a lot of interest. In the present study, we detected vimentin expression in NPC tissues and found that overexpression of vimentin is associated with poor prognosis of NPC patients. Silencing of vimentin in NPC CNE2 cells by RNAi suppresses cells migration and invasion in vitro. However, blocking vimentin did not affect cell proliferation of CNE2 cells. In addition, the in vivo metastatic potential of CNE2 cells transfected with Vimentin shRNA was suppressed in a nude mouse model of pulmonary metastasis. Silencing of Vimentin in CNE2 cells leads to a decrease of microvessel density and VEGF, CD31, MMP2, and MMP9 expressions in pulmonary metastatic tumors. Importantly, we found that it is easier for the tumor cells from the high vimentin-expressing pulmonary metastatic tumors to reinvade the microvessel and to form stable tumor plaques attached to the endothelial cells, which resemble the resource of circulating tumor cells and are very hard to eliminate. However, depletion of vimentin inhibits the formation of vascular tumor plaques. Our findings suggest that RNAi-based vimentin silencing may be a potential and promising anti-metastatic therapeutic strategy for NPC.
Keywords: Metastasis; Nasopharyngeal carcinoma; Tumor plaque; Vimentin.