Effect of @entity172 and antiestrogens on growth of @entity1 @entity0 cells in athymic XXXX .

@entity172 @entity1 @entity0 @entity440 @entity8413 @entity19 @entity5 @entity53 @entity73288 @entity441
Endocrine therapy with @entity172 deprivation or with antiestrogens results in @entity5 regression in a subset of @entity1 with @entity0 . To better understand the mechanisms by which @entity172 and antiestrogens modulate @entity0 growth in vivo, we have studied the effects of endocrine manipulation on the development and growth of @entity5 derived from cultured @entity1 @entity0 cells in the athymic nude @entity19 . MCF-7 @entity0 cells were inoculated into 6-week-old female BALB/c athymic @entity19 . @entity5 growth did not occur in ovariectomized @entity19 . Cells remained viable, however, since @entity172 supplementation more than 30 days later resulted in @entity5 formation. Minimal @entity5 growth was observed in intact female @entity19 which have low circulating @entity172 levels. @entity5 development and growth in ovariectomized or intact @entity19 supplemented with @entity53 in the form of a s.c. pellet were dose dependent; growth rates increased with @entity172 doses ranging from 0.01 to 0.5 mg. Antiestrogen treatment with either @entity440 or @entity441 caused transient stimulation of @entity5 growth, followed by a prolonged stationary phase. Growth resumed with @entity172 supplementation. Treatment of @entity19 bearing established MCF-7 @entity5 with @entity172 withdrawal (removal of @entity172 pellet) resulted in cessation of @entity5 growth, but not in @entity5 regression. Growth inhibition was also observed with antiestrogens and was dose dependent. However, @entity5 regression did not occur, even in @entity19 treated with high doses of @entity440 (serum concentration of 1.0 microM) for as long as 60 days. @entity5 growth was restored in these @entity19 with @entity172 replenishment. @entity5 cells also remained viable histologically despite prolonged (1 month) @entity172 deprivation or antiestrogen therapy, although the mitotic index was markedly reduced. Similar observations were made with @entity19 inoculated with the hormone-responsive ZR75-1 @entity1 @entity0 cells, but not with hormone-independent MDA-231 cells which were not influenced by @entity172 or @entity8413 treatment. In summary, development and growth of MCF-7 and ZR75-1 @entity5 in @entity19 are @entity172 dependent. @entity73288 therapy by @entity172 deprivation or antiestrogen treatment inhibits @entity5 cell proliferation in @entity19 , but does not cause @entity5 regression or loss of cell viability.
