title: A new strategy for selective targeting of progesterone receptor with passive antagonists.
abstract: Currently available progesterone (P4) receptor (PR) antagonists, such as mifepristone (RU486), lack specificity and display partial agonist properties, leading to potential drawbacks in their clinical use. Recent x-ray crystallographic studies have identified key contacts involved in the binding of agonists and antagonists with PR opening the way for a new rational strategy for inactivating PR. We report here the synthesis and characterization of a novel class of PR antagonists (APRn) designed from such studies. The lead molecule, the homosteroid APR19, displays in vivo endometrial anti-P4 activity. APR19 inhibits P4-induced PR recruitment and transactivation from synthetic and endogenous gene promoters. Importantly, it exhibits high PR selectivity with respect to other steroid hormone receptors and is devoid of any partial agonist activity on PR target gene transcription. Two-hybrid and immunostaining experiments reveal that APR19-bound PR is unable to interact with either steroid receptor coactivators 1 and 2 (SRC1 and SCR2) or nuclear receptor corepressor (NcoR) and silencing mediator of retinoid acid and thyroid hormone receptor (SMRT), in contrast to RU486-PR complexes. APR19 also inhibits agonist-induced phosphorylation of serine 294 regulating PR transcriptional activity and turnover kinetics. In silico docking studies based on the crystal structure of the PR ligand-binding domain show that, in contrast to P4, APR19 does not establish stabilizing hydrogen bonds with the ligand-binding cavity, resulting in an unstable ligand-receptor complex. Altogether, these properties highly distinguish APR19 from RU486 and likely its derivatives, suggesting that it belongs to a new class of pure antiprogestins that inactivate PR by a passive mechanism. These specific PR antagonists open new perspectives for long-term hormonal therapy.
authors.affiliation: Inserm U693, Assistance Publique-Hôpitaux de Paris, Hôpital Bicêtre, 94276 Le Kremlin-Bicêtre, France.
authors.forename: Junaid A
authors.initials: JA
authors.lastname: Khan
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Tikad
authors.forename: Michel
authors.initials: M
authors.lastname: Fay
authors.forename: Abdallah
authors.initials: A
authors.lastname: Hamze
authors.forename: Jérôme
authors.initials: J
authors.lastname: Fagart
authors.forename: Nathalie
authors.initials: N
authors.lastname: Chabbert-Buffet
authors.forename: Geri
authors.initials: G
authors.lastname: Meduri
authors.forename: Larbi
authors.initials: L
authors.lastname: Amazit
authors.forename: Jean-Daniel
authors.initials: JD
authors.lastname: Brion
authors.forename: Mouad
authors.initials: M
authors.lastname: Alami
authors.forename: Marc
authors.initials: M
authors.lastname: Lombès
authors.forename: Hugues
authors.initials: H
authors.lastname: Loosfelt
authors.forename: Marie-Edith
authors.initials: ME
authors.lastname: Rafestin-Oblin
mesh_terms: D021581:Active Transport, Cell Nucleus; D000736:Androstenes; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001665:Binding Sites; D001943:Breast Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D005260:Female; D057809:HEK293 Cells; D006718:Homosteroids / Q000138:chemical synthesis / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D009376:Neoplasms, Hormone-Dependent / Q000188:drug therapy*; D011485:Protein Binding; D059748:Proteolysis / Q000187:drug effects; D011980:Receptors, Progesterone / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013256:Steroids / Q000138:chemical synthesis / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: C585339:APR19 compound; C585340:APR6 compound; D000736:Androstenes; D018931:Antineoplastic Agents, Hormonal; D006718:Homosteroids; D011980:Receptors, Progesterone; D013256:Steroids; D014157:Transcription Factors