CX3CL1 and central nervous system cancer: However, recent studies have also suggested that the role of CX3CL1 in glioma progression may be more complicated, with Sciume et al. showing that TGF-β may exert its pro-tumorigenic effects by directly counteracting CX3CL1 activity, resulting in increased tumor invasion, suggesting that the CX3CL1/CX3CR1 axis may also play an inhibitory role in tumor progression [41].