COL2A1 and cancer: Yet, the downregulation of the type II collagen gene (COL2A1) in PC3SFRP2, which is involved in cancer stemness in various cancer types [38], and the upregulation of CDH15 (Cadherin 15) in PC3SFRP2, which mediates intracellular adhesion [39], are promising predictors of the role of SFRP2 in cancer metastasis.