CX3CL1 and neoplasm: Because CX3CL1 can bind to a wide variety of cell types, including immune cells, endothelial cells and tumor cells [54], [55], elucidating the different mechanisms by which CX3CL1 acts on various cell types to regulate tumor formation and progression, either positively or negatively, is critical for fully understanding its likely complex role in the tumor microenvironment.