SMAD2 and breast carcinoma: Studies have shown that SRGN promotes cell migration by binding to its receptor in CD44 in blood cells.18 CD44 is thought to be a classic marker of breast cancer stem cells and has an important role in tumor stem cell adhesion, invasion, metastasis, apoptosis resistance, chemoresistance, and EMT formation.17 For example, the binding of CD44 to its classical ligand, hyaluronic acid (HA), activates protein kinase C, which in turn activates transcription factor SMAD2/3, and subsequently has an important role in EMT formation.19, 20