PD-L1 expression as a predictive biomarker in lung cancer immunotherapy

Muhammad Vohra

Introduction. Non-Small Cell Lung Carcinoma (NSCLC) is a type of lung cancer that originates from epithelial lung cells and is responsible for 85% of all lung cancers.[1] Programmed death ligand 1(PD-L1), a member of the CD28 family, is a key immune checkpoint receptor expressing on the surface of activated T, B and NK cells which plays a crucial role in tumor mediated immune escape.[2] NSCLC tumor variability in PD-L1 expression is directly linked to the effectiveness of monoclonal anti-PDL1 antibodies.[3] Immunohistochemistry (IHC) is primarily used in detecting PD-L1 expression in NSCLC tumor cells. This method is problematic due to the lack of standardization and the possibility of heterogenous expression of PD-L1.[4]  PD-L1 expression is directly linked with greater survival rates and the effectiveness of monoclonal antibodies.[5] Methods. 22 NSCLC cases including mediastinal lymph node biopsies were evaluated for PD-L1 protein on tumor and immune cells and PD-L1 mRNA using the CheckPoint Typer assay.6] The impact of various PD-L1 expression rates on prognostic prediction in 321 patients whose NSCLC was evaluated with the use of immunohistochemistry.[5] Results. PD-L1 mRNA and IHC biomarker extraction data showed that there was agreement in the positive results. PD-L1 expression was positively detected in >50% of 28-8 IHC, and was reliable with the use of RT-qPCR.[6] PD-L1 expression on tumor cells was also associated with greater survivability in pulmonary squamous cell carcinomas.[5] Conclusions. PD-L1 expression on NSCLC cells as a predictive biomarker has utility to be used for prognostics and antibody treatment. The level of expression of PD-L1 and the survivability of the patient are related. The use of IHC in determining PD-L1 expression is problematic due to the lack of standardization. PD-L1 mRNA expression should be discussed as a possible alternative to this issue.


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