Abstract: Objective To investigate the effects and mechanism of periostin on their invasiveness of nasopharyngeal carcinoma cells EM>in vitro/EM>. Methods Western blotting was employed to detect the expression levels of periostin in the stroma of nasopharyngeal carcinoma (NPC) and normal nasopharyngeal mucosa (NNM), nasopharyngeal carcinoma cells 6-10B (low metastatic potential cell line ) and 5-8F (high metastatic potential cell line), NIH 3T3 fibroblasts. Eukaryotic expression plasmids of periostin were constructed and transfected into NIH 3T3 fibroblasts to obtain transient transfection cells, the expression of periostin was detected by Western blotting in NIH 3T3 cells before and after transfection. The biological effects were observed, including in vitro invasion by Boyden charmber assay, matrix metalloproteinase(MMPs) activation by gelatin zymogram. Results The expression levels of periostin protein varied in the two different metastatic-potential nasopharyngeal carcinoma cell lines and NIH 3T3 fibroblasts. Periostin was not expressed in 6-10B and NIH 3T3 cells, and 5-8F cells showed weak expression in comparison to the stroma of nasopharyngeal carcinoma. Boyden chamber assay indicated that the invasive capacity of 6-10B was significantly promoted by co-culture with Periostin-overexpression NIH 3T3 cells, and further study by gelatin zymogram assay indicated that MMPs in supernatant of periostin-overexpression NIH 3T3 cells co-culture with 6-10B were more active than negative controls and blank controls. Conclusion Periostin overexpression may promote the invasive capacity of nasopharyngeal carcinoma cells EM>in vitro/EM>. The action may exert through regulating the activity of MMPs. The study will provide a new idea for finding stromal targets in tumor therapy，and periostin is expected to be a new target

Key words: Periostin, Nasopharyngeal carcinoma, Metastasis, Matrix metalloproteinase, Transfection, Zymography, Boyden charmber