CCL2 and cancer: Other chemokine axes, such as the CXCL8-CXCR1/2 axis (105, 106), the CXCL9-CXCR3 axis (107, 108), the CXCL13-CXCR5 axis (109), the CCL2-CCR2 axis (110, 111), and the CCL20-CCR6 axis (112, 113), are also involved in cancer metastasis; the chemokine axis can vary depending on the type of cancer (114–116).