Download PD-1/PD-L1 pathway status in patients with non

PD-1/PD-L1 pathway status in patients with non-small cell lung cancer
Yoon Kyung Jeon
Department of Pathology, Seoul National University College of Medicine
Immune checkpoint pathway generally refers to a variety of inhibitory interactions between
T cells and antigen presenting cells or host cells, as represented by the CD80 or
CD86/CTLA4 pathway and the programmed cell death 1 ligand-1 (PD-L1) or PD-L2/PD-1
pathway. Physiologically, this pathway contributes to the maintenance of self-tolerance and
control of immune responses, thereby preventing autoimmunity and harmful tissue
damage. Cancer also utilizes immune checkpoints to evade the immune surveillance by
host. Blockade of these immune checkpoints reactivate and enhance anti-tumor immune
responses, and has emerged as a highly promising therapeutic strategy for cancer. However,
CTLA4 and PD-1/PD-L1 blockade have shown clinical efficacy in a subset of cancer patients,
thus demanding identification of predictive biomarkers. PD-1/PD-L1 blockade has achieved
favorable clinical benefit in patients with several types of cancer including malignant
melanoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, bladder cancer, and
Hodgkin lymphoma. In NSCLC, responsiveness to PD-1/PD-L1 blockade was related with
the PD-L1 expression level in tumor cells and/or tumor-infiltrating immune cells, preexisting adaptive immune responses, and the mutational load of tumor. Among these, PDL1 expression in tumor cells has been approved for companion diagnostics for PD-1
blockade therapy in NSCLC. In this talk, expression pattern and clinicopathological feature
of PD-1/PD-L1 pathway in NSCLC and the mechanism of PD-L1 induction by EML4-ALK
will be briefly reviewed.