ESR1 amplification in breast cancer – A new predictive marker?

Breast cancer is the leading malignancy in women, accounting for more than 350.000 deaths per year worldwide. Several molecular pathways are known to play a role in breast cancer development and progression. Perhaps the most important pathway involves estrogen receptor alpha protein (ER). Binding of estrogen to ER causes phosphorylation and dimerization of the receptor that acts as a transcriptional promoter conferring a growth signal to breast epithelial cells. This makes ER one of the most important therapeutic targets in breast cancer. Gene copy number increase (amplification) is a major mechanism for cancer…