Expression of programmed death-ligand 1 protein in head and neck squamous cell carcinoma and its clinicopathological correlates

The ability to escape immune surveillance is a hallmark of malignancy. Programmed death ligand 1 (PD-L1) facilitates tumor progression by binding to the immune inhibitory receptor known as programmed cell death protein 1 (PD1) on immune cells, resulting in suppression of the cytotoxic T lymphocyte function. The degree of PD-L1 expression may have a prognostic value in some cancer types, and it may vary according to the genetic makeup and the ethnicity of patients. The expression level of PD-L1 in 63 cases of primary head and neck squamous cell carcinoma (HNSCC) tumor tissues was evaluated using immunohistochemistry (IHC). Also, PD-L1 association with various clinicopathologic characteristics and overall survival was studied. The positive expression rate of PD-L1 in HNSCC was 85.7%, 60.3%, and 52.3% of the total number of cases using combined positive score (CPS)<i> ≥ </i>1, CPS<i> ≥ </i>5, and CPS <i>≥ </i>20 cutoff values, respectively. Statistical analysis revealed no significant relationship between the expression of PD-L1 protein and clinicopathological features except for tobacco use using a cutoff CPS ≥ 20. The log-rank chi-square results showed that PD-L1 was not a significant factor affecting the 4-year overall survival of HNSCC patients. Also, the overall survival rate was not significantly affected by the patient's age, tumor differentiation, tumor size, and lymphovascular invasion. However, survival curves demonstrated lower overall survival in HNSCC female patients, disease recurrence, and positive perineural invasion. Our findings showed relatively high PDL-1 expression in most HNSCC patients. No significant association was found between PD-L1 protein expression and overall survival.