title: A novel, high-affinity, fluorescent progesterone receptor antagonist. Synthesis and in vitro studies.
abstract: The present paper describes the chemical synthesis and in vitro characterization of a novel, high-affinity, fluorescent progesterone receptor (PR) antagonist. The three-step synthesis was carried out starting from mifepristone. After demethylation with calcium oxide, the methylamino group was alkylated with 6-bromohexanol, and the resulting compound was reacted with fluorescein 5-isothiocyanate, yielding the fluorescein-mifepristone conjugate. Interaction of the conjugate as well as of its precursors with PR was determined in cell culture (alkaline phosphatase assay and transactivation assay). Antiprogestagenic activity of the intermediates were comparable to that of the parent compound. Even after attachment of the bulky fluorescein moiety, considerable antiprogestagenic activity was maintained. Microscopic studies revealed that fluorescence of the conjugate was almost confined to the nuclei of steroid hormone receptor-positive cells, whereas the nuclei of steroid hormone receptor-negative cells remained unstained. To our knowledge, this is the first report on a fluorescent ligand for PR suitable for studies in living cells. It is proposed that the present fluorescent PR antagonist might serve as a lead compound for the development of contrast agents for PR imaging, e.g., by near-infrared optical imaging.
authors.affiliation: Institute for Pharmaceutical Chemistry and Pharmaceutical Technology, Karl-Franzens-University, Universitätsplatz 1, A-8010 Graz, Austria.
authors.forename: Claudia
authors.initials: C
authors.lastname: Hödl
authors.forename: Wolfgang S L
authors.initials: WS
authors.lastname: Strauss
authors.forename: Reinhard
authors.initials: R
authors.lastname: Sailer
authors.forename: Christoph
authors.initials: C
authors.lastname: Seger
authors.forename: Rudolf
authors.initials: R
authors.lastname: Steiner
authors.forename: Ernst
authors.initials: E
authors.lastname: Haslinger
authors.forename: H Wolfgang
authors.initials: HW
authors.lastname: Schramm
mesh_terms: D045744:Cell Line, Tumor; D019793:Fluorescein / Q000138:chemical synthesis* / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D015735:Mifepristone / Q000138:chemical synthesis* / Q000378:metabolism; D011980:Receptors, Progesterone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism
chemical_list: D011980:Receptors, Progesterone; D015735:Mifepristone; D019793:Fluorescein