ESR1 mutations maintain higher ER pathway activity relative to vehicle and ERa-WT controls following treatment with Raloxifene or fulvestrant.

The goal of the study was to understand whether mutations in ERa can promote resistance to various ERa antagonists of the SERD and SERM class. We found that ESR1 mutations can maintain higher ER pathway activity relative to control lines following short-term treatment with ERa antagonists raloxifene or fulvestrant. MCF7 lines were grown in media supplemented with 10% FBS. Cells were treated with raloxifene/fulvestrant for 16 hours prior to RNA collection and microarray analysis.