These findings on a member of the PGRMC family conducted using a mouse model of endometrial cancer advance our prior studies demonstrating that the knockdown of PGRMC1 in a human endometrial xenograft tumor attenuated tumor development, growth, and progression in vivo [31], a finding also supported by ovarian and breast cancer xenograft studies [30,32]. Here, PGRMC1 is linked to breast carcinoma.