S61-1 Genome-wide reprogramming of the chromatin landscape underlies endocrine therapy resistance in breast cancer

Program: Symposia
Session: S61-Long-Range, Rapid Signaling-Mediated and Epigenetic Control of Gene Expression by Nuclear Receptors
Monday, June 17, 2013: 4:00 PM-5:30 PM
Presentation Start Time: 4:00 PM
Room 133 (Moscone Center)
Mathieu Lupien*
University of Toronto, Toronto, ON, Canada
Talk Description:

The estrogen receptor alpha (ERα) drives growth in two-thirds of all breast cancers. Several targeted therapies, collectively termed endocrine therapy, impinge on estrogen-induced ERα activation to block tumor growth. However, half of ERα-positive breast cancers are tolerant or acquire resistance to endocrine therapy. We demonstrate that genome-wide reprogramming of the chromatin landscape, defined by epigenomic maps for regulatory elements or transcriptional activation and chromatin openness, underlies resistance to endocrine therapy. This annotation reveals endocrine therapy-response specific regulatory networks where NOTCH pathway is overactivated in resistant breast cancer cells while classical ERα signaling is epigenetically disengaged. Blocking NOTCH signaling abrogates growth of resistant breast cancer cells. Its activation state in primary breast tumors is a prognostic factor of resistance in endocrine treated patients. Overall, our work demonstrates that chromatin landscape reprogramming underlies changes in regulatory networks driving endocrine therapy resistance in breast cancer.

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