In addition, focusing on the FGF2/FGFR1 functional interaction that occurs between CAFs and breast cancer cells, we determined that FGF2 secretion by estrogens-treated CAFs prompts the up-regulation of CTGF expression through the FGFR1-ERK1/2-AKT signaling cascade in MDA-MB-231 cells. The gene discussed is FGF2; the disease is breast cancer.