ABSTRACT
Linkage of a 11beta-chloromethyl group to estradiol-17beta (E2) dramatically increases the binding affinity of the steroid for the estrogen receptor (ER) with the formation of a quasi-irreversible steroid-receptor complex. We have synthesized the two isomers of 11beta-chloromethyl-17alpha-iodovinyl-estradiol (E-CMIV and Z-CMIV) by a novel route. Both derivatives demonstrated high binding affinity and selectivity for ER (RBAs: ER = 820 and 1008; SHBG = 1.2 and 0.25, respectively; E2 = 100). On the basis of X-ray crystallographic data for Z-CMIV and its precursor, we have postulated that Z-CMIV might interact strongly with aromatic amino-acids within a hydrophobic groove of the ER hormone binding domain (HBD) that incorporates pockets corresponding to the 11beta and 17alpha steroid substituents. The binding properties of Z-CMIV labeled with 125I were investigated, especially its ability to detect and quantify altered ER forms with low binding affinity for E2. Sucrose density gradient analysis revealed that Z-CMIV has a higher activation potency than E2 as it converts a higher proportion of non-activated monomers in the cytosol into activated monomers with the potential to dimerize. In in vitro (MCF-7 cells) and in vivo (rat uterus) determinations of estrogenic activity, Z-CMIV was as potent as E2 in increasing progesterone receptor (PgR) concentrations and decreasing ER levels and in stimulating uterine growth. [125I]-Z-CMIV could open the way to new applications in the diagnosis and therapy of ER-positive breast cancers, especially those containing altered (variant) ERs.
Subject(s)
Estradiol/analogs & derivatives , Neoplasm Proteins/analysis , Neoplasms, Hormone-Dependent/chemistry , Receptors, Estrogen/analysis , Adenocarcinoma/pathology , Animals , Binding Sites/drug effects , Breast Neoplasms/pathology , Crystallography, X-Ray , Cytosol/chemistry , Drug Design , Estradiol/chemical synthesis , Estradiol/chemistry , Estradiol/pharmacology , Female , Gene Expression Regulation/drug effects , Humans , Mice , Models, Molecular , Molecular Structure , Neoplasm Proteins/metabolism , Neoplasms, Hormone-Dependent/pathology , Organ Size/drug effects , Protein Binding , Rats , Receptors, Estrogen/genetics , Receptors, Estrogen/isolation & purification , Receptors, Estrogen/metabolism , Receptors, Progesterone/biosynthesis , Receptors, Progesterone/genetics , Structure-Activity Relationship , Tumor Cells, Cultured/drug effects , Uterus/anatomy & histology , Uterus/chemistry , Uterus/drug effectsABSTRACT
Complexation of ligands containing an N3S donor set has been affected with [99mTc]. These are part of a ligand series of analogous structures which exhibit similar chemistry and potentially interesting biology. The complexes which have been characterized with [99Tc] as [TcOL] are neutral and lipophilic and their biological behaviour has been assessed in rats. After HPLC purification of the no-carrier added preparation, brain uptake of the tracers was greater than 1% at 15 min p.i. Muscle activity was significant with slow blood clearance.
Subject(s)
Brain/diagnostic imaging , Technetium , Animals , Blood Proteins/metabolism , Female , Ligands , Protein Binding , Radionuclide Imaging , Rats , Rats, Inbred Strains , Sodium Pertechnetate Tc 99m/chemistry , Sulfhydryl Compounds , Tissue DistributionABSTRACT
MRP20 (N-(2(1H pyrolylmethyl]N'-(4-pentene-3-one-2] ethane-1,2-diamine) complexes with technetium-99m, yielding a neutral, lipophilic species. This compound has been characterized as [TcO(MRP20)]. Biologic investigation of [99mTc][TcO(MRP20)] in female rats showed 2.35% ID in the brain 30 min p.i. with no significant wash-out over 3 hr. A single-photon emission computed tomography (SPECT) study in a dog demonstrated rapid tracer uptake in the brain, reaching a maximum within 1 min, with 2.24% i.d. 15 min p.i., decreasing to 1.7% after 4 hr. The complex undergoes hydrolysis in vitro forming a cationic species. This is possibly the trapping mechanism in the brain in vivo. The main excretory route of [99mTc][TcO(MRP20)] is via the hepatobiliary tract. There is evidence of some "in vivo" cell labeling and soft-tissue uptake.