SPARC and neoplasm: Copper is also an essential cofactor of various metalloproteins known to be closely correlated with tumor growth and metastatic invasion (Mitogen-Activated Protein Kinase Kinase 1 (MAP2K1), lysyl oxidase (LOX) and lysyl oxidase-like, (LOXL), Secreted Protein Acidic and Cysteine Rich (SPARC), ...).