Potential role of estrogen receptor α (ERα) phosphorylated at Serine in human breast cancer in vivo

Post-translational modifications of proteins are known to be important in protein activity and ERα is known to be phosphorylated at multiple sites within the protein. The exact function of site-specific phosphorylation in ERα is unknown, although several hypotheses have been developed using site-directed mutagenesis and cell culture models. Targeting the ERα at the level of such post-translational modification pathways would be a new and exciting approach to endocrine therapy in breast cancer, but adequate knowledge is lacking with regard to the relevance of site-specific phosphorylation in ERα in human breast cancer in vivo. Recently, antibodies to P-Serine¹¹⁸-ERα and P-Serine¹⁶⁷-ERα, two major sites of phosphorylation in ERα, have become available and some in vivo data are now available to complement studies in cells in culture. However, the in vivo data are somewhat contradictory and limited by the small cohorts used and the lack of standard well-characterized reagents and protocols.