The expression and prognostic relevance of programmed cell death protein 1 in tongue squamous cell carcinoma

Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor which plays an important role in a patient's immune responses to microbial and cancer antigens. It is expressed in tumor-infiltrating lymphocytes (TILs) with many different malignancies. The aim of the study was to evaluate PD-1 expression and its prognostic value in tongue cancer. The data of tongue squamous cell carcinoma (TSCC) patients (N = 81) treated in Tampere University Hospital between 1999 and 2013 were used. Control data consisted of patients with non-malignant tongue mucous membrane lesions (N = 48). The formalin-fixed paraffin-embedded samples were stained immunohistochemically and scanned via digital microscope. The staining of PD-1 was examined semi-quantitatively. The density and intensity of PD-1 + cells were significantly higher in TSCC than in control samples. The expression of PD-1 correlated with better survival. The expression of PD-1 could be a potential prognostic marker in TSCC. Further research using larger sample size is needed.