FASLG and breast cancer: Gruber et al. found that the CD95L/FasL (ligand molecule) expressed on CTCs in patients with breast cancer interacted with the upregulated transmembrane receptor CD95 (APO-1/FAS) on the surface of peripheral T-helper (Th) cells, which might mediate the transmission of apoptosis signal, contribute to systemic immunosuppression, and lead to the dormancy of CTCs [43].