Transcription profiling by array of human MCF7 breast cancer cells to study the acquisition of resistance to long term estrogen deprivation (LTED) on an aromatase inhibitor (AI)

The human oestrogen-positive breast cancer cell line MCF7 was cultured in phenol red-free RPMI medium supplemented with 10% fetal bovine serum, 10mg/ml insulin and 1nM estradiol (E2) and was referred to as wild-type MCF7. The wt-MCF7 cells were passaged weekly and medium was replenished every two to three days. To model acquisition of resistance to long term estrogen deprivation (LTED) on an aromatase inhibitor (AI), wt-MCF7 cells were cultured in phenol red-free RPMI medium supplemented with 10% dextran charcoal-stripped bovine serum (DCC) and 10mg/ml insulin. RNA was extracted from the LTED monolayers using RNeasy columns (Qiagen) according to manufacturer's protocol. RNA amplification, labeling and hybridization on HumanWG-6 v3 Expression BeadChips were performed according to the manufacturer's instructions (http://www.illumina.com) to assess changes in gene expression during adaptation to LTED.