Effects of sex- and glucocorticoid steroids on breast cancer cells grown as either multicellular tumor spheroids or monolayers.

The effects of estradiol, medroxyprogesterone acetate (MPA) dexamethasone, dihydrotestosterone and the antihormones 4-OH tamoxifen and RU 38486 were studied in two established breast carcinoma cell lines, the estrogen-sensitive ZR-75-1 and the estrogen-independent BT 20 cells applying two different in vitro systems, spheroid and monolayer cell culture in steroid deprived medium. Growth of ZR-75-1 spheroids was dramatically stimulated by the addition of estradiol, an effect which was neutralized by the simultaneous addition of 4-OH tamoxifen. The antiestrogen alone as well as dihydrotestosterone and MPA reduced ZR-75-1 spheroid growth significantly. While growth of BT 20 spheroids was only transiently inhibited by tamoxifen and dihydrotestosterone, a persistent increase in BT 20 spheroid growth was observed under MPA treatment in a concentration of 1 microM. This effect, although statistically significant, was very moderate. With the exception of this finding, growth effects of the different test compounds were similar in both in vitro systems, tumor spheroids and monolayer cell cultures.