Moreover, to identify candidate tumor-derived attractants for CTCs, Kim et al. [43] compared the secreted levels of 180 cytokines in conditioned media and found that the levels of several cytokines were higher, including CXCL6, CXCL8, oncostatin M, and vascular endothelial growth factor, among which CXCL6 and CXCL8 showed the sharpest increases. Here, CXCL8 is linked to neoplasm.