CCR4 and cancer: Chemokines (CXCL12 [67], CXCL8 [68], CXCL5 [69]) and chemokine receptors (CXCR1/2 [70], CCR4 [71, 72], CCR8 [73]) are well-known to deeply participate in the tumor development and progression in various cancers, including LUAD [74].