Analysis of FGF ligand expression in MDA-MB-231 cells revealed increased expression of ligands known to bind FGFR1, including FGF1, FGF19, FGF21 and FGF23 [24], suggesting that breast cancer cells express multiple potential regulators of FGFR1 activation that may act redundantly to induce FGFR signaling in osteoclasts. The gene discussed is FGF21; the disease is breast cancer.