Claudins 1, 3, and 4 protein expression in ER negative breast cancer correlates with markers of the basal phenotype

In the present study we investigated the protein expression of claudins 1, 3, and 4 and their relationship to clinical variables and outcome in a cohort of ER−ve and ER+ve human invasive breast cancers. Immunohistochemical analysis was performed on tissue microarrays representing a total of 412 tumors and interpretable data was derived from 314, 299, and 306 tumors for claudins 1, 3, and 4, respectively. In the ER+ve subset, 5%, 89%, and 52%, and in the ER−ve subset, 39%, 79%, and 79% of tumors stained positively for claudins 1, 3, and 4, respectively ( p