The relevance of phosphorylated forms of estrogen receptor in human breast cancer in vivo

Estrogen receptor (ER)α activity is regulated by phosphorylation at several sites. Recently several antibodies specific for individual phosphorylated sites within ERα have became available. Validation and use of these antibodies suggests that several forms of phosphorylated ERα can be detected in multiple ER+ human breast tumor samples, thus providing relevance for investigating the regulation and function of phosphorylated ERα in human breast cancer. Generally, the phosphorylated ERα isoforms are associated with parameters that suggest that they are markers of an intact estrogen dependent signaling pathway and better clinical outcome with respect to tamoxifen therapy. Profiling of phosphorylated ERα may provide better biomarkers of endocrine therapy response over and above those currently available.