It was found that YKL-40 could induce the coupling of syndecan-1 and αvβ3 integrin (Figure 13), resulting in phosphorylation of focal adhesion kinase (FAK) and activation of downstream ERK1/2 signaling pathway, which enhance vascular endothelial growth factor (VEGF) expression in tumor cells, angiogenesis, and tumor growth [214]. Here, PTK2 is linked to neoplasm.