Tumor microenvironment and immune escape affect pathogenesis and survival in classical Hodgkin lymphoma (cHL). While tumor-associated macrophage (TAM) content has been associated with poor outcomes, macrophage-derived determinants with clinical impact have remained undefined. Here, we have used multiplex immunohistochemistry and digital image analysis to characterize TAM immunophenotypes with regard to expression of checkpoint molecules programmed cell death ligand 1 (PD-L1) and indoleamine 2,3-dioxygenase 1 (IDO-1) from the diagnostic tumor tissue samples of 130 cHL patients, and correlated the findings with clinical characteristics and survival. We show that a large proportion of TAMs express PD-L1 (CD68+, median 32%; M2 type CD163+, median 22%), whereas the proportion of TAMs expressing IDO-1 is lower (CD68+, median 5.5%; CD163+, median 1.4%). A high proportion of PD-L1 and IDO-1 expressing TAMs from all TAMs (CD68+), or from CD163+ TAMs, is associated with inferior outcome. In multivariate analysis with age and stage, high proportions of PD-L1+ and IDO-1+ TAMs remain independent prognostic factors for freedom from treatment failure (PD-L1+CD68+/CD68+, HR = 2.63, 95% CI 1.17-5.88, p = 0.019; IDO-1+CD68+/CD68+, HR = 2.48, 95% CI 1.03-5.95, p = 0.042). In contrast, proportions of PD-L1+ tumor cells, all TAMs or PD-L1- and IDO-1- TAMs are not associated with outcome. The findings implicate that adverse prognostic impact of TAMs is checkpoint-dependent in cHL.
Keywords: checkpoint molecules; classical hodgkin lymphoma; multiplex immunohistochemistry; survival; tumor microenvironment; tumor-associated macrophages.