The concentration of programmed cell death-ligand 1 in the peripheral blood is a useful biomarker for esophageal squamous cell carcinoma

Background We determined the serum concentrations of Programmed cell death-1 (PD-1) and its ligands (PD-L1 and PD-L2) in patients with esophageal squamous cell carcinoma (ESCC). Methods Blood samples were collected from 85 patients with histologically proved ESCC. Serum levels of PD-1, PD-L1, and PD-L2 were measured using enzyme linked immunosorbent assays. Correlations between serum PD-1, PD-L1, and PD-L2 concentration and tumor depth, number of lymph node metastases, organ metastasis status, or disease stage were assessed and five-year survival rates according to clinicopathological characteristics were calculated. Results The concentration of PD-1 was not differed according to tumor progression. On the other hand, the average concentration of PD-L1 in patients with T3/T4 disease was 15.6 (12.2–18.3) pg/mL (25–75%), and this was significantly higher than that in patients with Tis/T1/T2 disease ( p = 0.020). Similarly, PD-L1 levels were significantly higher in patients with positive lymph nodes than in cases with negative lymph node involvement ( p = 0.006) and were higher in patients with organ metastasis ( p = 0.123) and in more advanced stage ( p = 0.006). Similar tendency was observed regarding PD-L2 concentrations. PD-L2 concentration was higher in T3, T4 cases ( p = 0.008), in LN positive cases ( p = 0.032), and in more advanced stage ( p = 0.024). Conclusion Our data showed that a concentration of PD-L1 in peripheral blood was high in advanced cancer and high concentration of PD-L1 predicted disease progression and also poor survival in patients with ESCC.