Estrogen priming of breast cancer ZR-75-1 cells results in a unique response to a timecourse of progesterone and medroxyprogesterone acetate exposure

A timecourse assessment of the response of ZR-75-1 breast cancer cells to progestogens in cells pretreated with estrogen. P4 treatment in cells pretreated with E2 results in a unique transcriptional response, including upregulation of ErbB growth factor pathways and alteration of the intrinsic subtype of the breast cancer cells. Cells were plated in 10nM estrogen or vehicle for 72h, followed by an overlay treatment for 4, 8 or 16h in triplicate with 10nM progesterone, 10nM medroxyprogesterone acetate, or equivalent vehicle (ethanol). 16hr samples were also treated with 10nM estrogen plus 10nM progesterone or 10nM estrogen plus medroxyprogesterone acetate. RNA was isolated for each sample and hybridised to Affymetrix Human Gene 1.0ST chips.