As reported in the literature [25], YKL-40 was identified as a tumor angiogenesis factor, inducing coordination of membrane-bound receptor syndecan 1 and integrin αvβ3, and activating an intracellular signaling cascade including FAK (focal adhesion kinase), Erk 1, and Erk 2 [26]. This evidence concerns the gene PTK2 and neoplasm.