Abstract: ObjectiveTo evaluate the protein expression of chromosome 2 open reading frame 40 (C2orf40) in nasopharyngeal carcinoma (NPC) tissues and cells, and to explore its association with cell differentiation and clinicopathological features. MethodsA total of 122 patients with NPC between January 2001 and December 2003 were enrolled in Cancer Hospital of Shantou University Medical College. The paraffinembedded tissue sections and medical records were collected. Twentyfive samples with chronic nasopharyngitis were used as controls. Tumor and control tissues from biopsies underwent immunohistochemical staining for C2orf40. C2orf40 expression was analyzed with clinicopathological variables. Besides, the protein expressions of C2orf40 were measured by Western blotting in three NPC cell lines, including CNE1, CNE2 and C6661. ResultsNinetysix percent (24/25) of control tissues showed positive expression, among which 88.0% showed dense staining. Otherwise, only 58.3% (71/122) of NPC samples were positive for C2orf40 protein and 82.0% showed weak staining. There was significantly difference between the two groups (U=255.500, P＜0.001). It was inversely related to lymph nodes status (r=-0.058, P＜0.001) and clinical stage (r=-0.202, P=0.026) by Spearman rank correlation test. In vitro, higher level of C2orf40 protein was found in well differentiated CNE1 cells, while lower levels were found in poorly differentiated cell lines CNE2 and C6661. ConclusionDownregulated C2orf40 expression is correlated with tumor cell differentiation, lymph nodes metastasis and clinical stage, and may be a molecular event in the occurrence and development of NPC. C2orf40 is likely to be a potential target of anticancer therapy.

Key words: Nasopharyngeal neoplasms, Pathology, clinical, C2orf40