Expression of claudins 1, 4, 5, and 7 and occludin, and relationship with prognosis in squamous cell carcinoma of the tongue.

Claudins and occludin are tight junctional proteins known to play a role in normal tissues and epithelial tumors. We analyzed the distribution patterns of claudins 1, 4, 5, and 7 and occludin in the superficial and invasive front of squamous cell carcinoma of the tongue of 97 patients and their relationship to cause-specific (squamous cell carcinoma of the tongue) patient survival (median follow-up period of 33.5 months; range, 1-234 months). Claudins 1 and 7 were strongly expressed, claudin 4 had moderate expression, whereas claudin 5 was least expressed. Occludin staining was mostly negative or very weak. Western blot analysis of tongue carcinoma (HSC-3) cells showed that all these proteins are also expressed in vitro. In cause-specific survival analysis, strong and low immunoreactivity of claudin 7 tended to be associated with decreased survival compared with medium immunoreactivity. We suggest that analyzing the immunohistologic staining levels of claudin 7 could be used for the prognostic purposes in patients with tongue squamous cell carcinoma.