Sp1 is over-expressed in nasopharyngeal cancer and is a poor prognostic indicator for patients receiving radiotherapy.

Nasopharyngeal cancer (NPC) is a tumor of epithelial origin with complex etiology. Currently the standard treatment of NPC is radiotherapy, but therapy failure is quite common, making radioresistance an important issue. This study explores the association of specificity protein 1 (Sp1) protein expression with clinicopathological significance and disease prognosis in NPC patients receiving radiotherapy. A total of 82 NPC patients (55 males and 27 females, median age: 48 years old) were enrolled and received radiotherapy between September 2011 and March 2014. Tumor tissue and grossly adjacent normal mucosa were obtained in each patient. Sp1 expression was detected by western blot and immunohistochemical analysis, and the associations with clinicopathological status and radiotherapy response were analyzed. Our Results showed Sp1 protein expression was higher in CNE-1 and CNE-2 nasopharyngeal cancer cells than in normal nasopharyngeal mucosal NP69 cells. All 82 patients' tissue sections were stained positive for the Sp1 protein, and 39 (47.6%) patients showed higher level than adjacent normal mucosa. Sp1-overexpression in the tumor tissue was correlated with a higher tumor stage, nodal status, clinical stage and distant metastasis (P < 0.01). Patients with higher Sp1 expression in pretreatment biopsies had a lower radiotherapy response compared to those with lower expression. In conclusion, Sp1 may play roles in radioresistance of nasopharyngeal cancer which attributes to tumor invasiveness, and serve as a novel prognostic marker of NPC radiotherapy. However, further studies are required to validate our findings in larger samples and explore more detailed mechanisms underlying radioresistance of Sp1.