CD63 and neoplasm: One important multifunctional secreted glycoprotein is tissue inhibitor of metalloproteinases 1 (TIMP-1) (20), which exhibits a canonical antiproteolytic activity towards metalloproteinases, including various matrix metalloproteinases (MMPs) (21), as well as a noncanonical cytokine-like function via several cell surface receptors (20, 22), including the interaction with the tetraspanin CD63, inducing increased proliferation (23) and survival of tumor cells (24) pointing at its tumor-promoting function in most cancers (25).