Functional estrogen receptors as biochemical marker for the detection of hormone-dependent breast cancer.

The translocatable receptors categorized as functional receptors were quantitated in a cross-incubation study of breast cancer nuclei with receptor-rich uterine cytosol. Data demonstrated that tumors that contained cytosolic estrogen receptor (ER) but had translocation defect might not be hormone dependent, whereas tumors with low ER but intact nuclear translocation step will respond to antiestrogen therapy. Cytosolic ER was estimated in 114 primary breast cancer tissues and ten metastatic axillary lymph nodes; 58% of postmenopausal and 54% of premenopausal breast cancer tissues were ER+ with a cutoff value of 10 fmoles and 3 fmoles/mg protein, respectively. Of tumors in the premenopausal and postmenopausal state, 62% and 57%, respectively, were positive for nuclear ER, with a cutoff value of 10 fmoles/100 micrograms DNA. This study suggested that evaluation of functional ER level would reduce the number of false-negative and false-positive tumors.