Progesterone receptor membrane component 1promotes survival of human breast cancer cells and the growth of xenograft tumors- Scytek Laboratories. Triple negative breast cancers (TNBCs) are highly aggressive and grow in response to sex steroid hormones despite lacking expression of the classical estrogen (E2) and progesterone (P4) receptors. Since P4 receptor membrane component 1 (PGRMC1) is expressed in breast cancer tumors and is known to mediate P4-induced cell survival, Breast cancer is diagnosed in over 230,000 women annually in the United States