Abstract
Data describing relationships between the tumor immune microenvironment and patient outcome are limited for esophageal squamous cell cancer (ESCC). The present study investigated the prognostic values of programmed death-ligand 1 (PD-L1) expression and CD8+ or forkhead box protein 3+ (FOXP3+) tumor-infiltrating lymphocytes (TILs) in 133 pathological T3N0M0 stage ESCC patients who underwent radical resection without neoadjuvant or adjuvant therapy. CD8+ and FOXP3+ TIL densities as well as PD-L1 levels in tumor cells and lymphocytes, were assessed through immunohistochemical staining. Patient survival was not associated with CD8+ or FOXP3+ TILs alone, but PD-L1 expression and the CD8+/FOXP3+ ratio were independent predictors of both disease-free and overall survival. PD-L1 expression correlated with age (p = 0.029), tumor length (p < 0.001), tumor differentiation status (p = 0.002) and reduced intratumoral CD8+ TIL density (p < 0.001). Our results suggest pT3N0M0 ESCC clinical outcomes correlate with CD8+ and FOXP3+ TIL densities and PD-L1 levels. Moreover, an intrinsic mechanism for induction of PD-L1 overexpression may be occurring during early tumor oncogenesis. This information may be useful for stratifying patients and guide the application of checkpoint blockade therapy in ESCC.