The interaction between programmed death ligand-1 (PD-L1) and programmed death receptor-1 (PD-1) on activated T cells sends an inhibitory signal that dampens the immune response. Tumors can express PD-L1 and evade the immune system. In advanced non-small cell lung carcinoma, expression of PD-1 in tumor-infiltrating lymphocytes (TILs) correlates with PD-L1 expression in tumor cells (TCs). However, this relationship has not been thoroughly explored in early disease.
To investigate the correlation of PD-1 and PD-L1 in non-small cell lung carcinoma tumor samples, with emphasis on stage I disease.
Whole tissue sections from non-small cell lung carcinoma tumors were retrospectively evaluated by immunohistochemistry for PD-1 and PD-L1 expression. The scoring was based on the percentage of cells positive for PD-1 in TILs and PD-L1 in TCs and tumor-infiltrating immune cells (ICs).
Expression of PD-1 in TILs was observed in 147 of 161 non-small cell lung carcinoma cases (91%). The majority of cases negative for PD-1 also lacked PD-L1 in TCs. The 68 cases with highest PD-1 expression in TILs included 33 (49%) with expression of PD-L1 in TCs and ICs. Strong correlations were observed in patients with elevated PD-1 expression in TILs and PD-L1 in TCs ( P = .01) and ICs ( P = .003). Expression of PD-1 also correlated with increased PD-L1 in TCs and ICs when the 2 were grouped together ( P < .001). Finally, stage I patients with negative PD-1 and PD-L1 expression showed trends toward increased disease-specific survival.
Expression of PD-1 in TILs correlates with PD-L1 expression in both TCs and ICs. Furthermore, negative expression of PD-1 and PD-L1 suggest trends toward disease-specific survival, even in early disease stages.