Estrogen and prolactin play important role in mammary carcinogenesis. The present study was undertaken to evaluate the effect of prolactin and estrogen cross-talk on HIF-1 α level and expression of some HIF-1 α- dependent signaling proteins. Since up-regulation of prolidase activity inhibits HIF-1 α degradation, the enzyme was considered as an interface of estrogen/prolactin signaling. The experiments were performed on MCF-7 cells cultured with prolactin in the presence or absence of estradiol. It was found that in the presence of estradiol, prolactin inhibits prolidase activity and its down-stream signaling proteins: HIF-1α, mTOR, AKT and MAPK p-38, while in the absence of estradiol, an opposite effect was observed. These results suggest that prolactin/estrogen cross-talk exert beneficial effect on prolidase-dependent down regulation of HIF-1α. It suggests that dual action of prolactin and estrogen may be considered as a strategy in therapy of breast cancer.
