BRCA2 protein expression in sporadic breast carcinoma with or without allelic loss of BRCA2.

To elucidate the cellular role of BRCA2 in sporadic breast tumors, we studied the cellular localization and the expression of BRCA2 in carcinomas presenting or not allelic loss of BRCA2. The breast tumors were first classified with or without allelic loss of BRCA2 and then immunohistochemical staining was performed on tumors and matched normal tissues using antibodies raised against BRCA2. We showed that BRCA2 is found either in the nucleus or in perinuclear compartments such as the endoplasmic reticulum and the Golgi vesicles. We have earlier demonstrated the presence of BRCA1 as an exocrine secretion in the lumen of ductules in the normal mammary gland, as well as BRCA1 and BRCA2 in milk-fat globules inside mammary-gland ductules during lactation. Here we show that BRCA2 is present within the lumina of breast ductules, indicating that BRCA2 protein may also be secreted in the mammary gland. No correlation was found in breast tumors between the expression of BRCA2 protein and allelic loss of BRCA2.