Abstract P6-07-07: Low dose of CDB-2914 and CDB-4124 efficiently inhibit the growth of T47D spheroid induced by pre-menopausal and post-menopausal concentrations of estrogen and progesterone

Background: The anti-progestins (RU-486, CDB-2914 and CDB-4124) may have potential to prevent estrogen receptor (ER) and progesterone receptor (PR) positive breast cancer. Physiological estradiol (E2), and progesterone (P4) levels are different in pre- and post-menopausal women. The purpose of this study was to determine: 1) Whether the physiological female hormones at pre- and postmenopausal concentrations affect the growth of an in vitro model of breast cancer, i.e., T47D spheroids, and 2) Whether anti-progestins at pharmacological concentrations work as growth inhibitors in high and low hormonal environments. Methods: T47D cells were grown as spheroids in the presence of serum concentrations of E2 and P4 consistent with pre- and postmenopause. Premenopausal luteal phase concentrations were 262 pM (71.3 pg/mL) of E2 + 18 nM (5.66 ng/mL) of P4; postmenopausal concentrations were 122 pM (33.2 pg/mL) of E2 + 3 nM (1.08 ng/mL) of P4. T47D cells (5000 per well) were seeded in 1.5% agarose coated 96 well plates, and grown in phenol red-free mammary epithelial cell growth basal medium (Lonza) supplemented with 10% double charcoal -stripped FBS. Hormones and anti-progestin treatments started 24 hrs after cell seeding. Three concentrations (50, 250, 1000 nM) of the anti-progestins were tested. Images of each spheroid were taken daily for 14 days, and the sizes of spheroids were analyzed by area (Pixel) using ImageJ software. Results: Results are presented in Table 1. Premenopausal and postmenopausal hormone concentrations stimulated spheroid growth by two- fold and 1.7 fold higher, respectively, when compared to the vehicle control (0.1% DMSO) at14 days. In the premenopausal condition, RU-486 showed moderate inhibition of spheroid growth at all three concentrations; CDB-2914 was more efficient at inhibition than CDB-4124 at 50 nM. At 250 nM and 1000 nM, CDB-2914 and CDB-4124 showed similar efficacy. In the postmenopausal condition, RU-486 showed very minor inhibition on spheroid growth at all three concentrations; CDB-2914 showed significantly higher inhibition than CDB-4124 at 50 nM. At 250 nM and 1000 nM, CDB-4124 was more efficient than CDB-2914. Conclusions: Our results indicate that T47D spheroids will grow in postmenopausal hormone concentrations, but growth is enhanced in premenopausal hormone conditions. RU-486 did not produce effective inhibition at postmenopausal hormone levels; however pharmacological concentrations (50, 250 and 1000 nM) of both CDB-2914 and CDB-4124 efficiently decrease the spheroid growth induced by both premenopausal and postmenopausal hormone levels. These data suggest that low doses of CDB-2914 and CDB-4124 should be further investigated for ER/PR positive breast cancer prevention and therapy. Citation Format: Oukseub Lee, Mi Ran Choi, Susan E Clare, Seema A Khan. Low dose of CDB-2914 and CDB-4124 efficiently inhibit the growth of T47D spheroid induced by pre-menopausal and post-menopausal concentrations of estrogen and progesterone [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-07-07.