Purpose To clarify the role of KAI1/CD82 in metastasis of nasopharyngeal carcinom and to evaluate the clinical efficacy of KAI1/CD82-expressing EPCs in the prevention of nasopharyngeal carcinoma.Method Umbilical vein-derived EPCs were infected with KAI1/CD82-expressing lenti-virus to get a KAI1/CD82-overexpressing EPC cell line (KAI1/CD82-EPCs).A xenograft mouse model of human nasopharyngeal carcinoma was established,and KAI1/CD82-EPCs were injected through the tail vein.The effect of the KAI1/CD82-EPCs on growth and metastasis of the xenograft was observed.Results Time required for tumor formation was 14.70 ± 3.81,15.05 ±3.85,14.20 ± 3.55 days respectively for the EPCs,EPCs-NC,and KAI1/CD82-EPCs groups,with no significant difference among the three groups (P =0.771).Weight of the xenograft was (1.388 ±0.204) g,(1.487 ±0.223) g,(1.485 ±0.234) g respectively for the EPCs,EPCs-NC,and KAI1/CD82-EPCs groups,with no significant difference (P =0.274).Rate of lung metastasis was 55％,45％ and 10％ for the EPCs,EPCs-NC,and KAI1/CD82-EPC groups,and the difference was significant (P =0.005).Number of metastatic lesions was 34.27 ± 5.35,38.44 ± 9.63,17.50 ± 3.54 for the three groups,and the difference was also significant (P =0.007).Immunohistochemistry indicated positive KAI1/CD82 expression in metastatic lesion of the KAI1/CD82-EPCs group,but no KAI1/CD82 expression in the EPCs group or EPCs-NC group.Conclusion KAI1/CD82-expressing EPCs inhibits lung metastasis of the xenograft mouse model of human nasopharyngeal carcinoma.