Penicillin

T47D-WT breast cancer cells carrying one stably integrated copy of the luciferase reporter gene driven by the MMTV promoter (32 (link)) and its derivative clone T47D/A1-2 that also expresses a functional full length rGR (27 (link)) were routinely grown in Dulbecco's Modified Eagle's medium (DMEM, Thermo Fisher Scientific). MCF-7L cells were kindly provided by Carol Lange although originally obtained from C. Kent Osborne (Baylor College of Medicine, Houston, TX, USA) (33 (link)). These cells were maintained in Dulbecco's Modification of Eagle's Medium supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, 100 mg/ml streptomycin and 1.4 U/ml Insulin (Novo Nordisk^® Pharma). For experiments, all cells were plated in DMEM medium without phenol red supplemented with 10% DEXtran-coated charcoal-treated FBS (DCC/FBS) and 48-h later medium was replaced by fresh medium without serum. After 24 h in serum-free conditions, cells were incubated with R5020 (Sigma) 10 nM and/or DEX (Sigma) 10 nM for different lengths of times at 37°C according to each experiment.