​Programmed death 1 (PD-1) is an immune inhibitory receptor that is widely expressed by cells of the immune system, especially cytotoxic T lymphocytes. Upregulation of the ligand PD-L1 prevents T-cell activation and contributes the evasion of tumour cells from immune recognition. Immune checkpoint inhibitors such as nivolumab and pembrolizumab are monoclonal antibody therapies that target PD-1 on the patient’s T-cells, thereby blocking PD-1/PD-L1 interaction and preventing tumour cells from inactivating the local cytotoxic T-cell response.

Upregulation of PD-L1 expression in tumour cells is demonstrated by immunohistochemistry. The resulting tumour percentage score (TPS) is used to estimate the likelihood of a patient’s tumour responding to first line pembrolizumab therapy.

Analysis of PD-L1 expression is carried out as an extension to the lung cancer testing panel, which also includes EGFR and KRAS mutation and ALK and ROS1 gene rearrangement analysis.

For clinical advice on appropriate investigations, please contact our Immunohistochemistry team 0131 242 7167.