• 1 January 1977
    • journal article
    • research article
    • Vol. 37  (9) , 3329-3332
Abstract
Human breast cancer cells in tissue culture contain estrogen receptors in their nuclei despite the absence of estrogen. Solid human breast cancer biopsies showed that proteolytic activities in extracts from the nuclear pellets of these biopsies interfere with or prevent the measurement of nuclear estrogen receptors when the protamine assay is used. The problems of receptor degradation can be avoided by the use of a hydroxylapatite assay.