Lack of synergy between estrogen and progesterone on local IGF-I, IGFBP-3 and IGFBP-2 secretion by both hormone-dependent and hormone-independent breast cancer explants in vitro. Effect of tamoxifen and mifepristone (RU 486)

In conclusion, the presented data suggest that there is no synergistic action of E2 and P4 in influencing IGF/IGFBPs ratio and, additionally, suggest a protective action of antiestrogen and antiprogestagen against excessive IGF-I secretion.