Claudins are major adhesion molecules in tight junctions and are strongly expressed in various cancers. We thus investigated the expression of claudin 5, a member of the claudin family, in breast cancer.
A total of 193 patients with breast cancer were identified based on their pathologic diagnosis. The expression of each claudin 5 was analyzed in the tumor by immunohistochemical staining. Parametric correlations were done between claudin 5 expression and the clinicopathologic findings.
Claudin 5 expression in patients with recurrent breast cancer was statistically significantly higher (P = .004). In addition, analysis of the correlation with other clinicopathologic factors showed statistically significant differences with respect to lymphatic invasion (P = .014), venous invasion (P = .048), estrogen receptor status (P = .002), and human epidermal growth factor 2 status (P = .007). Multivariate analysis revealed that claudin 5 expression was an independent predictive factor in the recurrence for relapse-free survival (RFS) (P = .020). Kaplan-Meier analysis showed that the RFS rate was significantly lower in the high claudin 5 expression group (P = .001).
Patients with breast cancer with high claudin 5 expression had a significantly lower RFS rate. Our findings suggest that claudin 5 may be useful as a new biomarker of a risk factor.