Fractalkine （FKN, CX3CL1） is a transmembrane chemokine expressed by neurons in the central nervous system （CNS）. It signals through its unique receptor, CX3CR1, that is expressed in microglia. The biological effects elicited by CX3CL1 on surrounding cells vary depending on a number of factors including its structure, the expression pattern of CX3CR1, and the cell type. Fractalkine/CX3CL1 chemokine ligand 1 （CX3CL1） is a chemokine involved in the anticancer function of lymphocytes-mainly NK cells, T cells and dendritic cells. Its increased levels in tumors improve the prognosis for cancer patients, although it is also associated with a poorer prognosis in some types of cancers, such as pancreatic ductal adenocarcinoma.