Benzothiophenes 3 and 4, derived from the acrylophenone antiestrogen trioxifene (2), are characterized by high estrogen receptor (ER) affinity and low residual estrogenicity compared to tamoxifen (1a). In order to characterize further the growth suppression mechanism for these structural types we have prepared structural variants of 2 bearing hydroxy groups positioned to maximize ER affinity. Thus, dihydronaphthalenes 5 and 6 and benzofluorenes 7 and 8 were prepared and studied in MCF-7 human breast cancer cells, in comparison with 3 and 4. All compounds were powerful suppressants of cell growth, with 50% inhibition ranging from 4.5 to 160 nM. Greatest potency was seen with diphenols 6 and 8. These compounds had intracellular ER affinities ranging from 0.2 to 4.1% of that of estradiol, suggestive of a potential for partial agonist effects. Simultaneous exposure of cells to 0.1 microM concentrations of estradiol and 3 or 4 did not affect the degree of growth inhibition seen with 0.1 microM 3 or 4 alone. Partial reversal of inhibition occurred when 0.1 microM 5-8 were each accompanied by 0.1 microM estradiol. Under these conditions complete reversal of growth inhibition has been found with 1a, 1b, and other triarylethylenes. Calmodulin, a putative target for triarylethylenes, and which is antagonized by 1a, was shown to interact weakly with 7 and 8 and not at all with 3-6. These results suggest that MCF-7 cell growth suppression by 3-8 may be due to interaction with unidentified receptors besides ER and extend earlier findings indicating that events occurring after interaction of these compounds with ER differ from those of triarylethylene antiestrogens.

Acylation of the sodio anion of beta-tetralone with phenyl anisoate, followed by a Grignard reaction of the resultant 4 with 4-methoxyphenylmagnesium bromide, gave rise to two novel dihydronaphthalene isomers 5 and 6. Regioselective demethylation of either 5 or 6 by NaSEt produced [3,4-dihydro-2-(4-methoxyphenyl)-1-naphthalenyl](4-hydroxyphenyl)methanone (7). Etherification of the phenolic group of 7 by N-(2-chloroethyl)pyrrolidine and subsequent methanesulfonate salt formation provided [3,4-dihydro-2-(4-methoxyphenyl)-1-maphthalenyl]]4-]2-(1-pyrrolidinyl)ethoxy]phenyl]methanone, methane sulfonic acid salt (3). Potent antiestrogenic activity of 3 was demonstrated by both oral and subcutaneous administration to rats and mice. In vitro binding studies with rat uterine cytosol estrogen receptors indicate compound 3 has a very high binding affinity which exceeds that of estradiol.

No abstract