ABSTRACT: Comparison of the effects of EM-652 [SCH57068], tamoxifen,
toremifene, droloxifene, idoxifene, GW-5638 and raloxifene on
the growth of human ZR-75-1 breast tumors in nude mice
EM-652 exerts pure antiestrogenic activity in the mammary
gland and endometrium, while tamoxifen, the antiestrogen
most widely used for the treatment of breast cancer, exerts mixed
antiestrogenic-estrogenic activity in these tissues. Our objective
was to compare the agonistic and antagonistic effects of EM-652
with tamoxifen and 5 other antiestrogens on the growth of ZR-75-1
human breast xenografts in ovariectomized nude mice.
23 weeks of treatment at a daily oral dose of 50 g, EM-652 was
the only compound that decreased tumor size relative to pretreatment
values, whereas the 6 other antiestrogens only decreased to various
extents the progression rate stimulated by estrone. Under estrone
stimulation, all groups of animals had more than 60% of their
tumors in the progression category except for the EM-652-treated
group, where only 7% of the tumors progressed.
In the absence
of estrone stimulation, progression was seen in 60%, 33%, 21%
and 12% of tumors in the tamoxifen-, idoxifene-, toremifene-
and raloxifene-treated groups, respectively, while only 4% of
tumors progressed in the EM-652-treated group.
and antagonistic actions of each antiestrogen were also measured
on endometrial epithelial cell thickness. Our present findings
indicate that EM-652, in addition to being the most potent antiestrogen
on human breast tumor growth, has no agonistic effect in breast
and endometrial tissues.
Since previous data have shown benefits
of EM-652 on bone density and lipid profile, this compound could
be an ideal candidate for chemoprevention of breast and uterine
cancers, while protecting against osteoporosis and cardiovascular
[04/15/2002; International Journal of Cancer]
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