Assessment of programmed cell death ligand- 1 (PD-L1) expression in oral potentially malignant disorders and oral squamous cell carcinoma - An immunohistochemical study

OSCC is multifactorial and is a multistep process. It may arise de-novo or may be preceded by oral potentially malignant disorders(OPMD). During malignant transformation certain molecular changes are evident at cellular level even in the absence of phenotypic changes in the tissue. With the recent advances in molecular understanding of cancers, immune checkpoint inhibitors have been recognized as perpetrators or supporters in the pathophysiology of various cancers. One of the main immunosuppressive pathways is the programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) in which there is an interaction between T-cell PD-1 receptor and PD-L1 on cancer cells. Upregulation of PD-L1 is associated with disease progression. To assess and compare the PD-L1 expression in OPMD and OSCC. 64 Paraffin embedded tissue sections of histopathologically diagnosed cases of 32 OSCC and 32 OPMD were immunohistochemically stained with PD-L1 & its membranous expression was evaluated. Descriptive statistical analysis was applied. Thus the study showed 100 % PD-L1 positive expression in OSCC and PD-L1 expression increased with increase in histopathological. In case of OPMD 93.74 % showed positive PD-L1 expression. We found PDL1 expression is significantly higher in OSCC (Mean= 4.59 ± 1.965) compared to OPMD (Mean= 2.03 ± 1.204). Assessment of PD-L1 expression in OPMD patients will help us to screen the subjects with or without risk of malignant transformation as increase in PD-L1 expression signifies the increased risk of malignant change.