PDCD1 and small cell lung carcinoma: Furthermore, in light of the remarkable success seen in NSCLC, parallel studies undertaken in SCLC have also shown considerable promise for immunotherapies that include antibodies against programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte antigen 4 (CTLA4; Figure 1) [37,38] discussed below.