Effects of progestagens and Org OD14 in in vitro and in vivo tumor models

Sex steroids, in particular estradiol (E2) and progesterone (P4), play, together with other hormones and growth factors, a role in the development of normal breast tissue. The effect of four progestagens (norethisterone, 3-ketodesogestrel, gestodene and P4) and Org OD14, a steroid with weak estrogenic, progestagenic and androgenic properties were studied on growth of breast tumor cells in vitro using two subclones of MCF-7 (H and A) and T47D (S and A) cells. In addition, we investigated the effects of 3-ketodesogestrel, gestodene and Org OD14 on the growth of 7,12-dimethyl-benz(a)anthracene(DMBA)-induced mammary tumors in rats. In the in vitro assays with MCF-7 cells norethisterone, 3-ketodesogestrel and gestodene stimulated growth only at high doses (10^?7 M), whereas P4 had no effect. Gestodene was more potent than 3-ketodesogestrel and norethisterone. Org OD14, stimulated cell growth at a dose of 10^?8 M, while E2 is active at 10^?10 M. In T47D-A cells similar effects were found, but the subclone S did not respond to the progestagens and Org OD14. The two T47D subclones also reacted differently to progestagens during growth stimulation with E2. In T47D-S the progestagens and Org OD14 inhibited, while in T47D-A these compounds did not modulate the effect of E2. In the DMBA model we found that gestodene and 3-ketodesogestrel were able to inhibit tumor growth to the same extent. Surprisingly, Org OD14 was even more effective in the DMBA model using the therapeutic approach. Using the prophylaxic approach tumor development was delayed and tumor growth was strongly suppressed. The inhibitory effects of Org OD14 on tumor growth in the DMBA model may be attributed to its mixed hormonal profile. From these studies we conclude that different cell lines and even subclones thereof respond quite differently to steroids. Both in vitro and in vivo studies are required to judge whether synthetic steroids might be involved in an increased risk for the development of breast tumors.