title: ORG-2058 as a ligand in the assay of progesterone receptor in breast cancer.
abstract: Tritiated [(16 alpha-ethyl-21-hydroxy-19-nor-pregn-4-ene-3,20-dione)-6,7-3H] (ORG-2058) and 17,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione (R5020) were compared as ligands in the assay of progesterone receptor in human and rat breast tumors. We found that ORG-2058 is a better ligand because of its low nonspecific binding. Most of the nonspecific binding of the other ligand R5020, is to proteins which bind corticosteroids. In cancerous tissue ORG-2058 binds to progesterone receptor linearly in a range of protein concentrations which are normally used in the receptor assay. On the other hand, R5020 exhibits binding linearity over a narrower protein concentration in many tumor biopsies, which may cause severe limitation in the assay procedure or frequent underestimation of receptor content.
authors.affiliation: Endocrinology Laboratory, Soroka University Hospital, Ben-Gurion University of the Negev, Beer Sheva, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Sharoni
authors.forename: B
authors.initials: B
authors.lastname: Feldman
authors.forename: N
authors.initials: N
authors.lastname: Karny
authors.forename: J
authors.initials: J
authors.lastname: Levy
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism; D011282:Pregnenediones; D011397:Promegestone; D051381:Rats; D011980:Receptors, Progesterone / Q000032:analysis*; D014599:Uterus / Q000378:metabolism
chemical_list: D011282:Pregnenediones; D011980:Receptors, Progesterone; C020175:16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione; D011397:Promegestone