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.
Keywords: Enzyme-linked immunosorbent assay; Esophageal cancer; Programmed cell death ligand; Programmed cell death-1; Squamous cell carcinoma.