Progesterone receptor membrane component 1 promotes the growth of breast cancers by altering the phosphoproteome and augmenting EGFR/PI3K/AKT signalling.

Increased expression of the progesterone receptor membrane component 1 (PGRMC1) has been linked to multiple cancers, including breast cancer. Despite being a regulatory receptor and a potential therapeutic target, the oncogenic potential of PGRMC1 has not been studied. The impact of PGRMC1 on breast cancer growth and progression was studied following chemical inhibition and alteration of PGRMC1 expression, and evaluated by using online-based gene expression datasets of human breast cancer tissue. MTS, flow cytometry, qPCR, Western blotting, confocal microscopy and phosphoproteome analysis were performed. We observed higher PGRMC1 levels in both ER-positive ZR-75-1 and TNBC MDA-MB-468 cells. Both chemical inhibition and silencing decreased cell proliferation, induced cell-cycle arrest, promoted apoptosis and reduced the migratory and invasive capabilities of ZR-75-1 and MDA-MB-468 cells. Further, phosphoproteome analysis demonstrated an overall decrease in activation of proteins involved in PI3K/AKT/mTOR and EGFR signalling pathways. In contrast, overexpression of PGRMC1 in non-malignant MCF10A cells resulted in increased cell proliferation, and enhanced activity of PI3K/AKT/mTOR and EGFR signalling pathways. Our data demonstrate that PGRMC1 plays a prominent role in regulating the growth of cancer cells by altering the PI3K/AKT/mTOR and EGFR signalling mechanisms in both ER-positive and TNBC cells.