4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and Breast-Neoplasms

4,4'-Diamino-2,2'-stilbene disulfonic acid (DAS), a key intermediate in the synthesis of dyes and fluorescent whitening agents, has been purported to have weak estrogenic properties based on apparent structural similarity with diethylstibestrol (DES) and unsubstantiated reports of male reproductive dysfunction in an industrial setting. In weanling rats, high doses of DAS (300 mg/kg ip; 1000-3000 mg/kg oral) have been associated with modest increases in the uterus/body weight ratio (Smith & Quinn, 1992). In order to more directly and definitively determine if DAS possesses estrogenic activity, in vitro studies were conducted to establish its relative binding affinity to the human estrogen receptor (ER) in MCF-7 cells, a well-characterized breast cancer cell line. At concentrations approaching its solubility limit (10(-4) M), DAS failed to display [3H]-17beta-estradiol (E2) from the ER. In contrast, DES and E2 demonstrated characteristic competitive binding curves (50% displacement of 3H-E2 at 3.33 x 10(-9) and 1.33 x 10(-8) M, respectively). Parallel in vivo comparisons of DAS (10 or 30 mg/animal) and DES (1 or 3 microgram/animal) were also conducted to assess uterotropic effects. After three daily subcutaneous injections, DAS did not induce uterine weight gain. In contrast, DES consistently and markedly increased uterine weight and induced uterine water imbibition, with the latter effect being absent in DAS-treated rats. Under these experimental conditions, DAS was shown to possess negligible, if any, estrogenic activity, despite apparent structural similarity with known estrogens.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; Animals; Binding, Competitive; Breast Neoplasms; Diethylstilbestrol; Estradiol; Estrogens, Non-Steroidal; Female; Humans; Indicators and Reagents; Injections, Subcutaneous; Male; Organ Size; Rats; Rats, Sprague-Dawley; Receptors, Estrogen; Tumor Cells, Cultured; Uterus

ATP increases intracellular Ca++ ([Ca++]i) by activating different P2-purinoreceptors. Because ATP increases Cl- secretion in cystic fibrosis (CF)-affected epithelia, the current study was designed to establish the link between these two events. Studies were done in epithelial, human MCF-7 breast tumor cells in which the presence of mRNA transcripts encoding CF transmembrane conductance regulator was initially established. Changes in [Ca++]i were measured in single cells by fluorescence microscopy; anion transport was measured by 125I efflux. ATP stimulated concentration-dependent increases in [Ca++]i and 125I efflux from MCF-7 cells. The relative order of agonist potency of various selective P2-purinoreceptor agonists in increasing [Ca++]i and 125I efflux was: UTP > or = ATP > ADP = AMP; 2-chloro-ATP, 2-methylthio-ATP and AMP-phencyclidine were considerably less potent than ATP. The Ca++ ionophore ionomycin increased both intracellular [Ca++]i and 125I secretion. Exposing cells to the intracellular chelator ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetra-acetic acid (EGTA)-acetoxymethylester decreased (AM) decreased ATP- and ionomycin-stimulated 125I efflux. Extracellular EGTA did not alter the Ca++ response to ATP, but inhibited the response to ionomycin. The chelator inhibited both ATP- and ionomycin-induced 125I secretion. Exposure of cells to nifedipine did not affect the responsiveness of MCF-7 cells to ATP. The anion transport antagonist 4,4'-diisothiocyananatostilbene-2,2'-disulfonic acid partially inhibited ATP- and cationophore-stimulated increases in [Ca++]i and 125I secretion. The data suggest that activation of P2 receptors in MCF-7 cells leads to an increase in anion transport as a result of the ability of ATP to increase [Ca++]i; moreover, anion channel antagonists may produce their inhibitory effect on 125I secretion, in part, by blocking agonist-induced intracellular Ca++ signaling.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Adenosine Triphosphate; Breast Neoplasms; Calcium; Chloride Channels; Chlorides; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Dose-Response Relationship, Drug; Humans; Iodine Radioisotopes; Ion Channels; Membrane Proteins; Receptors, Purinergic; RNA, Messenger; Signal Transduction; Tumor Cells, Cultured