XCL1 and neoplasm: studies indicated that NK cells can also produce chemokines, C-C-motif ligands such as CCL3, CCL4, CCL5, X-C-motif chemokine ligand 1 (XCL1) and C-X-C-motif chemokine ligand 8 (CXCL8), which attract a variety of immune cells to transformed tissues and inhibit tumor progression (49).