Previous work has demonstrated the OPN-induced initiation of mesenchymal stem cell adoption of the myCAF phenotype with a consequent juxtacrine increase in MDA-MB-231 cell and HepG2 cell stemness, using separate co-culture models of human MDA-MB-231 breast cancer and Hep-G2 liver cancer [13,22-24]. Here, SPP1 is linked to breast carcinoma.