Progesterone receptor membrane component 1 is phosphorylated upon progestin treatment in breast cancer cells.

Menopausal hormone therapy, using estrogen and synthetic progestins, is associated with an increased risk of developing breast cancer. The effect of progestins on breast cells is complex and not yet fully understood. In previous and studies, we found different progestins to increase the proliferation of Progesterone Receptor Membrane Component-1 (PGRMC1)-overexpressing MCF7 cells (MCF7/PGRMC1), suggesting a possible role of PGRMC1 in transducing membrane-initiated progestin signals.