Characterization of tumor microenvironment and cell interaction patterns in testicular and diffuse large B-cell lymphomas.

The tumor microenvironments (TME) of diffuse large B-cell lymphoma (DLBCL) subgroups have remained poorly characterized. Here, we dissected the composition and spatial organization of the TME in germinal center B-cell (GCB), activated B-cell (ABC), and testicular (T-) DLBCL using gene expression profiling and multiplex immunohistochemistry. We found that high proportions of M2-like tumor-associated macrophages (TAM) and cytotoxic tumor-infiltrating T cells (TIL) were characteristic of ABC DLBCL TME. Furthermore, high CD8+ TIL content translated to favorable outcomes. In contrast, GCB DLBCL TME was enriched in CD4+ TIL, regulatory TIL, and a higher M1-like: M2-like TAM ratio, and high proportions of TAM and Granzyme B+ cells associated with worse survival. TIL and TAM interacted more frequently with M2-like TAM and cytotoxic TIL in the ABC DLBCL in contrast to GCB subtype, where the interactions were more abundant with other TIL and CD4+ TIL. In T-DLBCL, TME resembled that of ABC DLBCL with a higher proportion of M2-like TAM and cytotoxic cells, except that checkpoint-positive TIL were less prominent compared to DLBCL NOS. Cytotoxic TIL also interacted more with TIL and TAM. A large number of CD163+ TAM interactions with distinct TIL translated to unfavorable survival both in GCB DLBCL and T-DLBCL, whereas a high number of interactions between TIL and TAM, CD4+ TIL and TAM, and CD4+ TIL and other TIL were associated with favorable outcomes only in T-DLBCL. Together, our data demonstrate biologically and clinically relevant differences in the composition of and cellular interactions in the TME between various DLBCL entities.