PD-1/PD-L1 expression and interaction by automated quantitative immunofluorescent analysis show adverse prognostic impact in patients with diffuse large B-cell lymphoma having T-cell infiltration: a study from the International DLBCL Consortium Program

Programmed cell death protein 1/programmed cell death protein ligand1 (PD-1/ PD-L1) interaction is an important immune checkpointtargeted by anti-PD-1/ PD-L1immunotherapies. However, the observed prognosticsignificance of PD-1/ PD-L1expression in diffuse large B-cell lymphomatreated with the standard of care has been inconsistent and even contradictory. To clarify the prognosticrole of PD-1/ PD-L1expression and interaction in diffuse large B-cell lymphoma, in this study we used 3-marker fluorescent multiplex immunohistochemistry and Automated Quantitative Analysis Technology to assess the CD3+, PD-L1+, and PD-1+ CD3+ expression in diagnostic samples and PD-1/ PD-L1interaction as indicated by presence of PD-1+ CD3+ cells in the vicinity of PD-L1+ cells, analyzed their prognosticeffects in 414 patients with de novo diffuse large B-cell lymphoma, and examined whether PD-1/ PD-L1interaction is required for the prognosticrole of PD-1+/ PD-L1+ expression. We found that low T-cell tissue cellularity, tissue PD-L1+ expression (irrespective of cell types), PD-1+ CD3+ expression, and PD-1/ PD-L1interaction showed hierarchical adverse prognosticeffects in the study cohort. PD-1/ PD-L1interaction showed higher sensitivity and specificity than PD-1+ and PD-L1+ expression in predicting inferior prognosis in patients with high CD3+ tissue cellularity (“hot”/inflammatory tumors). However, both PD-1+ and PD-L1+ expression showed adverse prognosticeffects independent of PD-1/ PD-L1interaction, and PD-1/ PD-L1interaction showed favorable prognosticeffect in PD-L1+ patients without high CD3+ tissue cellularity. Macrophage function and tumor-cell MYC expression may contribute to the PD-1-independent adverse prognosticeffect of PD-L1+ expression. In summary, low T-cell tissue cellularity has unfavorable prognosticimpact in diffuse large B-cell lymphoma, and tissue PD-L1+ expression and T-cell-derived PD-1+ expression have significant adverse impact only in patients with high T-cell infiltration. PD-1/ PD-L1interaction in tissue is essential but not always responsible for the inhibitory effect of PD-L1+/PD-1+ expression. These results suggest the benefit of PD-1/ PD-L1blockade therapies only in patients with sufficient T-cell infiltration, and the potential of immunofluorescent assays and Automated Quantitative Analysis in the clinical assessment of PD-1/ PD-L1expression and interaction.