ABSTRACT
Novel gadolinium-based mifepristone conjugates were synthesised using various synthetic routes. Moderate antiprogestagenic activity of the new conjugates was observed in human breast cancer cells (T47-D cells) using AP (alkaline phosphatase) assay. The amount of incorporated Gd determined by inductively coupled plasma mass spectroscopy (ICPMS) indicates the number of binding sites per cell. These conjugates might be important compounds to develop receptor-targeted MRI contrast agents as well as other anti-breast cancer therapeutics.
Subject(s)
Breast Neoplasms/diagnosis , Coordination Complexes/chemical synthesis , Gadolinium/chemistry , Mifepristone/chemistry , Receptors, Progesterone/metabolism , Binding Sites , Breast Neoplasms/drug therapy , Cell Line, Tumor , Coordination Complexes/chemistry , Female , Humans , Magnetic Resonance Imaging , Mifepristone/chemical synthesis , Receptors, Progesterone/antagonists & inhibitorsABSTRACT
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.
