FST and breast neoplasm: In order to evaluate the effect of follistatin in ER-ve (MDA-MB-231) and ER + ve (MCF7) cells they were treated with 6000 pg/ml of activin A in the presence or absence of follistatin (64,000 pg/ml) for 72 hours (activin concentrations were chosen to replicate inter-tumoural levels of activin in breast tumours [15]).