Reflections on immune checkpoint inhibition in non-small cell lung cancer

Despite the expanding armamentarium of treatment modalities against metastatic non-small cell lung cancer (NSCLC) this disease remains incurable. The introduction of targeted therapies provides transient control of disease for some molecular subtypes but virtually all patients’ progress. Recently immunotherapies have been approved for the treatment of metastatic melanoma and prostate cancer, and have shown promise for the treatment of NSCLC. More specifically, the blockade of immune checkpoints may improve outcomes in the treatment of NSCLC. Immune checkpoints modulate immune responses to effectively balance self-tolerance and tissue destruction. Many tumors express immune checkpoints or their ligands to inhibit anti-tumor immune responses. One of the most important immune checkpoints is programmed cell death ligand 1 (PD-L1), which was discovered at Mayo Clinic (1).