FASLG and cancer: During immunosurveillance, NK and T cells expressing FasL induce apoptosis of cancer cells having functional Fas receptors (a death receptor).64–66 However, cancer cells with altered Fas receptors evade the immune response.64,67 Besides these survival mechanisms, cancer cells can activate local immunological tolerance by overexpressing certain ligands, such as programmed cell death-ligand 1 (PD-L1), that keeps NK and T cells under their control.68