FASLG and non-small cell lung carcinoma: Although the exact mechanisms remain unclear, we speculate that blockade of NSCLC-intrinsic PD-1 can release PD-L1 and stimulate the expression of co-inhibitory molecules such as Fas ligand, which jointly mediate the apoptotic pathway of activated lymphocytes after application of PD-1 mAb (Zhao et al., 2018).