Clinicopathological analysis of programmed cell death 1 and programmed cell death ligand 1 expression in the tumour microenvironments of diffuse large B cell lymphomas

Aims: To investigate the clinicopathological characteristics of programmed cell death ligand 1 (PD-L1) and programmed cell death 1 (PD-1) expression in the tumour microenvironments of diffuse large B cell lymphoma (DLBCL). Methods and results: Tumour tissues from 126 DLBCL patients were immunostained for PD-L1 and PD-1. The expression of PD-L1 by tumour cells and/or tumourinfiltrating immune cells (mainly macrophages) was evaluated, and the number of tumour-infiltrating PD-1(+) cells was assessed. PD-L1 expression in tumour cells was observed in 61.1% of DLBCLs, with a weak intensity in 29.4%, moderate intensity in 21.4% and strong intensity in 10.3% of cases. Strong PD-L1 expression in tumour cells was associated significantly with the presence of B symptoms (adjusted P = 0.005) and Epstein-Barr virus (EBV) infection (adjusted P = 0.015), and tended to be higher in activated B cell-like immunophe-notype (16.7%) than germinal centre B cell-like immunophenotype (2.5%) (adjusted P = 0.271). DLBCLs with PD-L1 expression in tumour cells/macrophages showed similar clinicopathological characteristics. The quantity of PD-1(+) tumour-infiltrating lymphocytes correlated positively with the level of PDL1 expression in tumour cells (P = 0.042) or in tumour cells/macrophages (P = 0.03). Increased infiltration of PD-1(+) cells was associated with prolonged progression-free survival (P = 0.005) and overall survival (P = 0.026) in DLBCL patients treated with rituximab-cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP), whereas PD-L1 expression had no prognostic significance. Conclusions: PD-L1 and PD-1 were expressed variably in DLBCLs by tumour cells and tumour-infiltrating immune cells and might be potential therapeutic targets using PD-1/PD-L1 blockade.