Altered intracellular region of MUC 1 and disrupted correlation of polarity‐related molecules in breast cancer subtypes

MUC 1 glycoprotein is overexpressed and its intracellular localization altered during breast carcinoma tumorigenesis. The present study aimed to clarify the relationship of cytoplasmic localization of MUC1 with the breast cancer subtype and the correlation of 10 molecules associated with cell polarity in breast cancer subtypes. We immunostained 131 formalin‐fixed and paraffin‐embedded breast cancer specimens with an anti‐MUC1 antibody (MUC1/CORE). For 48 of the 131 tumor specimens, laser‐assisted microdissection and real‐time quantitative RT‐PCR were performed to analyze mRNA levels of MUC1 and 10 molecules, β‐catenin, E‐cadherin, claudin 3, claudin 4, claudin 7, RhoA, cdc42, Rac1, Par3 and Par6. Localization of MUC1 protein varied among breast cancer subtypes, that is, both the apical domain and cytoplasm in luminal A‐like tumors ( P