Because the heparan sulfate proteoglycans of syndecan-1 are known to facilitate the assembly of signaling complexes between growth factors and their cognate receptors on breast cancer cells [32,33], Maeda and coworkers concluded that stromal syndecan-1 on the surface of fibroblasts is a crucial factor regulating epithelial–stromal interactions in breast cancer. The gene discussed is SDC1; the disease is breast carcinoma.