FGFR1 and cancer: FGF1 binds to FGFR1 and activates ERαin BC cells, potentially stimulating cancer progression even after estrogen deprivation.[36] FGF1 activates the MAPK and PI3K signaling pathways through FGFR3, leading to tamoxifen resistance in MCF-7 cells.[37] Additionally, when MCF-7 cells transfected with FGF1 are transplanted into ovariectomized mice, they promote the occurrence of endocrine-resistant tumors.[38] FGF7 is another significant risk factor for the development of ER+ BC.