Abstract
BACKGROUND: For the development of PGRMC1, a multifunctional receptor belonging to membrane-associated progesterone receptor proteins (MAPR) family, as possible predictive marker for increased hormone-dependent breast cancer (BC) risk, a systematic research program has been performed, starting with different BC cells, continued with animal studies and finally with clinical studies with BC patients. SUMMARY: In vitro studies showed dose- and time-dependent BC cell proliferations with all available synthetic progestogens (not with progesterone), but mostly significant only in the presence of PGRMC1. Different animal (xenograft) studies confirmed that synthetic progestogens, but not progesterone and dydrogesterone, increased the estradiol-induced tumor proliferation, although with dydrogesterone, a small time-dependent increase could be seen. Clinical studies with hormone replacement therapy (HRT) to confirm these results are still running. In patients with BC expression of PGRMC1 in BC tissue was correlated to tumor characteristics like diameter, grade, and metastatic status. BC patients with PGRMC1 in the tumors had poorer disease-free and overall survival. After developing of an assay, blood levels could be correlated to the expression in BC tissue showing PGRMC1 superior to tumor markers such as CEA, CA125, CA153, and TPS. KEY MESSAGES: This review is summarizing two different functions of PGRMC1: (1) to predict the prognosis of BC patients, already well demonstrated in BC patients and (2) being a possible predictive marker for BC risk during HRT as suggested from in vitro and animal research.