Expression level of PD-L1 is involved in ALDH1A1-mediated poor prognosis in patients with head and neck squamous cell carcinoma.

Objective: To evaluate the expression levels of ALDH1A1, PDL1, and PDL2 in head and neck squamous cell carcinoma (HNSCC) patients, and explore their clinical relevance in prognosis of patients with HNSCC.

Methods: Immunohistochemistry of ALDH1A1 and PD-L1/PD-L2 in 85 primary HNSCC patients was carried out. The expression level of PD-L2 was assessed with the modified Moratin's immune response scoring (IRS) system. tumor proportion score (TPS) was defined as the percentage of viable tumor cells showing partial or complete membrane staining at any intensity. The chi-square test and Fisher's exact test were used to analyze the associations between ALDH1A1 expression and clinicopathological features. The Spearman's correlation was applied to analyze the correlation of ALDH1A1 expression with PD-L1/PD-L2 expression.

Results: kaplan-Meier analysis showed that the expression levels of ALDH1A1 and PD-L1/PD-L2 were inversely associated with recurrence-free survival (RFS; P = 0.001, 0.014, and 0.023, respectively). Moreover, expression levels of ALDH1A1 and PD-L1 were correlated with poor overall survival (OS; P = 0.002 and 0.039, respectively). Furthermore, multivariate logistics regression analyses demonstrated that expression level of ALDH1A1 was independently associated with shorter RFS (P = 0.013) and poorer OS (P = 0.014) in HNSCC patients, and the expression level of PD-L2 was only negatively associated with RFS (P = 0.041), rather than PD-L1. Spearman's correlation analysis unveiled that expression levels of PD-L1 and PD-L2 were positively correlated with ALDH1A1 expression in HNSCC patients (P = 0.000 and 0.015, respectively). Especially, the patients with expression levels of ALDH1A1 and PD-L1 had the worst prognosis.

Conclusions: Our results indicated that ALDH1A1 is an independent prognostic factor in patients with HNSCC, and the expression level of PDL-1 may be involved in ALDH1A1-mediated poor prognosis in patients with HNSCC.