Identification of a claudin‐4 and E‐cadherin score to predict prognosis in breast cancer

The elevated expression of claudins (CLDN) and E‐cadherin (CDH‐1) was found to correlate with poor prognostic features. Our aim was to perform a comprehensive analysis to assess their potential to predict prognosis in breast cancer. The expression of CLDN‐1, ‐3–5, ‐7, ‐8, ‐10, ‐15, ‐18, and E‐cadherin at the mRNA level was evaluated in correlation with survival in datasets containing expression measurements of 1809 breast cancer patients. The breast cancer tissues of 197 patients were evaluated with tissue microarray technique and immunohistochemical method for CLDN‐1–5, ‐7, and E‐cadherin protein expression. An additional validation set of 387 patients was used to test the accuracy of the resulting prognostic score. Based on the bioinformatic screening of publicly‐available datasets, the metagene of CLDN‐3, ‐4, ‐7, and E‐cadherin was shown to have the most powerful predictive power in the survival analyses. An immunohistochemical protein profile consisting of CLDN‐2, ‐4, and E‐cadherin was able to predict outcome in the most effective manner in the training set. Combining the overlapping members of the above two methods resulted in the claudin‐4 and E‐cadherin score (CURIO), which was able to accurately predict relapse‐free survival in the validation cohort (P = 0.029). The multivariate analysis, including clinicopathological variables and the CURIO, showed that the latter kept its predictive power (P = 0.040). Furthermore, the CURIO was able to further refine prognosis, separating good versus poor prognosis subgroups in luminal A, luminal B, and triple‐negative breast cancer intrinsic subtypes. In breast cancer, the CURIO provides additional prognostic information besides the routinely utilized diagnostic approaches and factors. (Cancer Sci 2011; 102: 2248–2254)