Mammosphere Formation in Breast Cancer Cells

MCF-7 and MDA-MB-231 human breast cancer cells were purchased from the Korea Cell Line Bank (KCLB, Seoul, Korea) and incubated in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin (Gibco, CA, USA) in an incubator (37 °C, 5% CO₂). Human breast cancer cells were cultured at 0.5 × 10⁴ (MDA-MA-231) and 4 × 10⁴ (MCF-7) cells per plate in an ultralow attachment 6-well plate with a MammoCult^TM culture medium (StemCell Technologies, Vancouver, BC, Canada) supplemented with hydrocortisone and heparin for 1 week in an incubator (37 °C, 5% CO₂). Mammosphere formation was assessed using the National Institute of Standards and Technology (NIST)’s integrated colony enumerator (NICE) program [63 (link)]. Mammosphere formation was determined by examining the mammosphere formation efficiency (MFE) (%) [64 (link)].