PD-L1 AND FOXP3 EXPRESSION IN ORAL DYSPLASTIC TISSUES AND ORAL SQUAMOUS CELL CARCINOMA

Background Oral squamous cell carcinoma (OSCC) is an aggressive, highly immunosuppressive cancer with a high mortality rate. Interactions between programmed cell death protein 1 (PD-1; on T cells) and programmed death ligand 1 (PD-L1; on tumor cells) within the tumor microenvironment facilitates T-lymphocyte exhaustion. Regulatory T cells (Treg) are a distinct lymphocyte population, expressing the transcription factor forkhead homeobox protein-3 (FoxP3), which downregulates immune responses in OSCC. PD-L1+ tumor cells and FoxP3+ Treg expression in OSCC has been associated with poor prognosis. This research investigates the expression of PD-L1+ cells and Tregs in control, dysplastic, and OSCC tissues. Objective To investigate and compare the expression of PD-L1+ tumor cells and FoxP3+ Tregs in nondysplastic tisssue, dysplastic tissue, and OSCC using immunohistochemistry. Methods Immunohistochemistry was performed on formalin-fixed, paraffin-embedded, archival tissues. Qualitative and quantitative analyses of positively stained cells were undertaken and the dysplastic (n = 20) and OSCC groups (n = 20) were compared against the non-dysplastic control group (n = 20), using image analysis Results A higher proportion score and immunoreactive score for PD-L1+ and FoxP3+ Tregs was found in OSCC and dysplastic groups when compared to the nondysplastic control group (P Conclusions Significantly more PD-L1+ cells and Tregs were detected in dysplastic and OSCC tissues. An increase in PD-L1 and FoxP3 expression may serve as an indicator of progression from normal to a potentially malignant lesion.