CCL2 and cancer: CSC-derived tumors contain increased levels of proinflammatory cytokine IL-6 and chemokines IL-8 (CXCL8), MCP-1 (CCL2), and MIP-1α (CCL15), which are potent stimulators of angiogenesis and tumor cell proliferation and play an important role in tumor progression and metastasis in a variety of human cancers, including lung cancers [33].