Hyperactivation of PI3K promotes escape from hormone dependence in estrogen receptor-positive breast cancer

Hyperactivation of phosphatidylinositol-3 kinase (PI3K) promotes escape from hormone dependence in estrogen receptor-positive breast cancer. A significant fraction of breast cancers exhibit de novo or acquired resistance to estrogen deprivation. We used gene expression microarrays to identify genes and pathways that are commonly dysregulated in ER+ cell lines with acquired hormone-independent growth. MCF-7, ZR75-1, MDA-361, and HCC-1428 ER+, estrogen-responsive breast cancer cells were cultured under hormone-depleted conditions (10% DCC-FBS) for several months until sustainable hormone-independent cell populations emerged. Parental and long-term estrogen-deprived (LTED) cells were treated with 10% dextran-coated charcoal-treated fetal bovine serum (DCC-FBS) x 24 hrs prior to RNA harvest for array analysis.