Multiple extractions of hormone receptors from mixed human breast tumors.

Multiple extractions of hormone receptors from mixed human breast tumors revealed a considerable amount of ER and PgR activity remaining in the second and third cytosol fractions extracted by the same tris buffer system (TEDG, pH 7.4, containing 10 mM tris, 1.5 mM EDTA, 2.0 mM dithiothreitol, and 10% glycerol). The incomplete and inefficient extraction of tumors with tris buffer system after only one homogenization and centrifugation is a serious concern in efforts to achieve accurate determinations of receptor concentrations which permit the accurate prediction of hormone responsiveness of breast cancers.