ESR1 and breast cancer: This may be due to the paracrine interactions of PDGF-CC released from breast cancer cells interacting with fibroblasts through PDGFRs, orchestrating an ERα-negative phenotype through stimulation of hepatocyte growth factor (HGF), insulin-like growth factor binding protein (IGFBP) 3 and stanniocalcin (STC) 1 secretion from CAFs (73).