Slug overexpression is associated with poor prognosis in thymoma patients.

Slug, a member of the Snail family of transcriptional factors, is a newly identified suppressive transcriptional factor of E-cadherin. The present study investigated the expression pattern of Slug in thymomas to evaluate its clinical significance. Immunohistochemistry was used to investigate the expression pattern of the Slug protein in archived tissue sections from 100 thymoma and 60 histologically normal thymus tissue samples. The associations between Slug expression and clinicopathological factors, such as prognosis, were analyzed. Positive expression of Slug was detected in a greater proportion of thymoma samples [51/100 (51%) patients, P<0.001] compared with normal thymus tissues [9/60 (15%) cases]. Of the 100 patients with thymoma, 42 (42%) displayed high levels of Slug expression (high-level group) and 58 (58%) displayed low levels of Slug expression (low-level group). The 10-year survival rate was improved for patients in the low-level group when compared with those in the high-level group (P=0.002). A multivariate analysis using the Cox proportional hazards regression model demonstrated that Slug overexpression was not an independent prognostic factor. In conclusion, the present study demonstrated that Slug overexpression was associated with poor prognosis in patients with thymoma. Therefore, Slug may be a potential diagnostic biomarker and a predictor of poor prognosis in thymoma patients.