CX3CL1 and CXCL13 were shown to play an important role in the brain extravasation of breast cancer [72], while the following cytokines/chemokines were involved in the extravasation of melanoma cells (9IL-23 [115], CXCL10 [116], CXCR3 [116], CXCL10 receptor [116], CCR4 [117], CCL17 [117], and CCR4 [117]) and lung cancer cells (TNF-α [131] and CX3CR1 [143]). The gene discussed is CCR4; the disease is lung carcinoma.