Estradiol-Induced MMP-9 Expression via PELP1-Mediated Membrane-Initiated Signaling in ERα-Positive Breast Cancer Cells.

Proline-, glutamic acid-, leucine-rich protein 1 (PELP1) is a novel estrogen receptor (ER) coregulator, demonstrated distinctive characters from other ERα coregulators, and has been suggested to be involved in metastasis of several cancers. In ERα-positive breast cancer, PELP1 overexpression enhanced ruffles and filopodium-like structure stimulated by estradiol (E₂) through extranuclear cell signaling transduction hereby increased cell motility. However, whether PELP1 is also involved in extracellular matrix remodeling of ERα-positive breast cancer cells is still unknown. In this study, we investigated the role of PELP1 in E₂-induced MMP-9 expression and the underlined mechanism. The results demonstrated the following: E₂-induced ERα-positive MCF-7 breast cancer cell MMP-9 mRNA and protein expression in a rapid response and concentration-dependent manner. Knocked down PELP1 significantly suppressed E₂-induced MMP-9 expression. E₂-bovine serum albumin (BSA), a large molecular membrane-impenetrable conjugate of E₂, can also upregulate MMP-9 protein expression in MCF-7, and the action of E₂-BSA can be abolished by PI3K inhibitor LY294002; treating MCF-7 simultaneously with PELP1-shRNA and LY294002 did not show synergetic inhibitory effect on E₂-BSA-induced MMP-9 expression. Our results indicated that estrogen-induced MMP-9 expression in ER-positive breast cancer cells may be through PELP1-mediated PI3K/Akt signaling pathway.