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

Abstract

<h3>Background</h3> 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. <h3>Objective</h3> To investigate and compare the expression of PD-L1⁺ tumor cells and FoxP3⁺ Tregs in nondysplastic tisssue, dysplastic tissue, and OSCC using immunohistochemistry. <h3>Methods</h3> 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 <h3>Results</h3> 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 (<i>P</i> < .05). There was no significant difference between the OSCC and dysplastic tissues. <h3>Conclusions</h3> 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.