Growth inhibitory effect of LH-RH analogs on human breast cancer cells.

The antiproliferative effect of two LH-RH agonists (Pro 9-LH-RH ethylamide and D Ser(t BU)6 Aza Gly 10-LH-RH, ICI 118630) on the human breast cancer cell line CG5 is reported. Although ineffective when used alone, both analogs inhibited in a dose-dependent fashion the growth stimulatory effect of estradiol. LH-RH analogs did not influence the growth inhibitory effect of tamoxifen and medroxyprogesterone acetate. Likewise, these compounds neither modified basal estrogen and progesterone receptor levels nor prevented estrogen-induced increase of progesterone receptor. A marked antiproliferative effect of the analogs was also seen in cells stimulated with other mitogens, such as insulin and epidermal growth factor.