Expression of PD-L1 and CD4+ tumor-infiltrating lymphocytes predict survival in head and neck squamous cell carcinoma

The clinical efficacy of immune checkpoint blockade has been recently demonstrated in a variety of cancer types. The aim of the present study was to characterize the expression profile of tumor-infiltrating lymphocytes (TILs) and programmed death-ligand 1 (PD-L1) in head and neck squamous carcinoma (HNSCC). A total of 63 patients with HNSCC were enrolled in the present study. CD3⁺ and CD4⁺ TILs and the expression of PD-L1 were detected by immunohistochemistry. PD-L1 mRNA levels were evaluated by reverse transcription-quantitative PCR analysis. The association of TILs and PD-L1 with patient clinicopathological characteristics was also assessed. CD3⁺ and CD4⁺ TILs were detected in 100% of the samples. CD3⁺ was the predominant subset of TILs. PD-L1 was expressed in 53 of 61 (86%) patients when a score of ≥1 on tumor cells was considered positive and in 28 patients (45.2%) when a score of >5 on tumor cells was considered positive. PD-L1 mRNA levels were determined to be significantly correlated with PD-L1 protein expression. Survival analysis demonstrated that high CD4⁺ TILs were associated with improved overall survival (OS) and disease-free survival (DFS), and furthermore, the association of high PD-L1 expression with unfavorable OS and DFS was statistically significant. Multivariate analysis identified CD4⁺ TILs and PD-L1 as prognostic markers for HNSCC. The results of the present study suggested that increased CD4⁺ TILs in HNSCC may be associated with improved outcomes, while high expression of PD-L1 may indicate unfavorable OS and DFS; thus, these factors may serve as predictors of the response to immune checkpoint therapy.