Progesterone-induced secretion of growth hormone,insulin-like growth factor I and prolactin by human breast cancer explants

The aim of the study was to evaluate the potential of human breast cancer tissue to secrete growth hormone (GH) ,insulin-like growth factor I (IGF-I) and prolactin in response to 10^?7 M progesterone stimulation. Explants were divided according to estrogen receptor (ER)/progesterone receptor (PR) phenotype (ER(?)PR(?); ER(+)PR(?); ER(+)PR(+); ER(?)PR(+)). Our results show distinct differences in cultured breast cancer tissue responses to progesterone stimulation with regard to secretion of proliferative agents such as GH ,IGF-I and prolactin. All but ER(?)PR(?) breast cancer cell types responded in vitro to progesterone stimulation with an increase in local GH secretion ,while in non-malignant tissue progesterone induced local GH secretion only in PR(+) cells. Moreover ,only in PR(+) cells did progesterone stimulate local IGF-I and prolactin secretion ,in both malignant and non-malignant tissue. This study provides evidence for the first time that in PR(+) breast cancer tissue ,progesterone may increase GH ,prolactin and IGF-I secretion in both malignant and surrounding non-malignant tissue. These hormones may act as local growth factors that stimulate the proliferation of mammary tumors.