Second, given the low levels of CXCR3 expression in CX3CR1+ CD8+ T cells (Fig. 2b), which is required to traffic to tumors41, it is possible that CX3CR1+ CD8+ T cells remain in circulation, and might not actively traffic to the tumor unless fractalkine (CX3CL1), the ligand of CX3CR1 is produced from the TME. This evidence concerns the gene CX3CR1 and neoplasm.