MCF7 cell culture

MCF7 cells, a breast cancer cell line of the luminal type (Figure S1), were derived from a single progenitor cell and were grown in DMEM (Dulbecco's Modified Eagle Medium) with 4.5 g/L glucose and L-Glutamine, without sodium pyruvate (DMEM, Corning), supplemented with 10% fetal bovine serum (FBS, Atlanta Biologicals), penicillin (100 U/mL, Gibco) and streptomycin (100 mg/mL, Gibco), and insulin at 10 μg/ml (Insulin solution from bovine pancreas, Sigma). The cells were grown to 80% confluency. They were passaged approximately every 3-4 days: washed with 1XPBS (PBS, pH 7.4, Gibco), trypsinized (Trypsin-EDTA, Gibco) and split at about 1:4 ratio).