PD-L1 expression in human cancers and its association with clinical outcomes

• Published in: OncoTargets and therapy Vol. 9; pp. 5023 - 5039
• Main Authors: Yu, Jinming, Wang, Xin, Teng, Feifei, Kong, Li
• Format: Journal Article
• Language: English
• Published: New Zealand Taylor & Francis Ltd 01.01.2016; Dove Medical Press
• Subjects: Antigens; Apoptosis; Binding sites; Bladder; Bladder cancer; Breast cancer; Cancer immunotherapy; Cell growth; Clinical outcomes; Colorectal cancer; Cytokines; Dendritic cells; Esophageal cancer; Immune checkpoint; Kidney cancer; Ligands; Liver cancer; Lung cancer; Lymphocytes; Lymphoma; Medical prognosis; Melanoma; Ovarian cancer; Pancreatic cancer; PD-L1 protein; Renal cell carcinoma; Review; Signal transduction; Skin cancer; T cell receptors; Tumors; PD-L1; checkpoint blockade; prognostic value; clinical outcome; immunotherapy
• ISSN: 1178-6930; 1178-6930
• DOI: 10.2147/OTT.S105862

PD-L1 is an immunoinhibitory molecule that suppresses the activation of T cells, leading to the progression of tumors. Overexpression of PD-L1 in cancers such as gastric cancer, hepatocellular carcinoma, renal cell carcinoma, esophageal cancer, pancreatic cancer, ovarian cancer, and bladder cancer is associated with poor clinical outcomes. In contrast, PD-L1 expression correlates with better clinical outcomes in breast cancer and merkel cell carcinoma. The prognostic value of PD-L1 expression in lung cancer, colorectal cancer, and melanoma is controversial. Blocking antibodies that target PD-1 and PD-L1 have achieved remarkable response rates in cancer patients who have PD-L1-overexpressing tumors. However, using PD-L1 as an exclusive predictive biomarker for cancer immunotherapy is questionable due to the low accuracy of PD-L1 immunohistochemistry staining. Factors that affect the accuracy of PD-L1 immunohistochemistry staining are as follows. First, antibodies used in different studies have different sensitivity. Second, in different studies, the cut-off value of PD-L1 staining positivity is different. Third, PD-L1 expression in tumors is not uniform, and sampling time and location may affect the results of PD-L1 staining. Therefore, better understanding of tumor microenvironment and use of other biomarkers such as gene marker and combined index are necessary to better identify patients who will benefit from PD-1/PD-L1 checkpoint blockade therapy.