Association of FGFR1 with ERα Maintains Ligand-Independent ER Transcription and Mediates Resistance to Estrogen Deprivation in ER Breast Cancer.

amplification occurs in approximately 15% of estrogen receptor-positive (ER) human breast cancers. We investigated mechanisms by which amplification confers antiestrogen resistance to ER breast cancer. ER tumors from patients treated with letrozole before surgery were subjected to Ki67 IHC, FGFR1 FISH, and RNA sequencing (RNA-seq).