Detection of the level of estrogen receptor and functional variants in human breast cancers by novel assays

The level of estrogen receptor (ER) is a key determinant for the management of ER-positive [ER(+)] breast cancer patients. Growth of many human breast cancers is regulated by estrogen (E2) and progesterone (Pr). Generally; th e ER in ER(+) breast cancer is targeted for therapy with antihormones. Howe ver 40% of ER(+) patients do not respond to antihormone therapy. Thus, the identification of antihormone resistant ER(+) breast cancers is essential t herapeutic predictions. Although H-3-E2 binding and immunodetection can ide ntify ER, these procedures do not assess the functional state of the recept or molecule. In this study we describe a novel and rapid assay for the dete ction of ER and its functional state on the basis of the downstream interac tion with its response element based on the preferential binding of DNA-pro tein complex (ERE-ER) to a nitrocellulose membrane (NBMA). This method perm its measurement of both the total and the functional fraction of ER. The ER status was examined in breast cancer cell lines and iii breast cancer biop sy specimens by (i) H-3-E2 binding assay, (ii) immunodetection assays and ( iii) by its interaction with P-32-ERE The sensitive NMBA assay was validate d with well-characterized ER(+) breast cancer cell lines and also identifie d functional variants of ER among breast tumor biopsy specimens.