Primary central nervous system lymphoma (PCNSL) is confined to the brain, eyes, and cerebrospinal fluid without evidence of systemic spread. Rarely, PCNSL occurs in the context of immunosuppression, e.g. post-transplant lymphoproliferative disorders (PTLD) or HIV (AIDS-related PCNSL). These cases are poorly characterized, have dismal outcome and are typically Epstein-Barr virus (EBV)-tissue positive. We used targeted sequencing and digital multiplex gene expression to compare the genetic landscape and tumor microenvironment (TME) of 91 PCNSL tissues all with diffuse large B-cell lymphoma histology. 47 were EBV-tissue negative: 45 EBV(-) HIV(-) PCNSL, 2 EBV(-) HIV(+) PCNSL; and 44 were EBV-tissue positive: 23 EBV(+) HIV(+) PCNSL, 21 EBV(+) HIV(-) PCNSL. As with prior studies, EBV(-) HIV(-) PCNSL had frequent MYD88, CD79B and PIM1 mutations, and enrichment for the activated B-cell (ABC) cell-of-origin (COO) sub-type. In contrast, these mutations were absent in all EBV-tissue positive cases and ABC frequency was low. Furthermore, copy number loss in HLA-class I/II and antigen presenting/processing genes were rarely observed, indicating retained antigen presentation. To counter this, EBV(+) HIV(-) PCNSL had a tolerogenic TME with elevated macrophage and immune-checkpoint gene expression, whereas AIDS-related PCNSL had low CD4 gene counts. EBV-tissue positive PCNSL in the immunosuppressed is immunobiologically distinct from EBV(-) HIV(-) PCNSL, and despite expressing an immunogenic virus retains the ability to present EBV-antigens. Results provide a framework for targeted treatment.
Blockade of the PD-1 axis has modest efficacy in diffuse large B-cell lymphoma (DLBCL), but data regarding LAG3 are sparse. The impact of LAG3 digital gene expression was tested in 309 patients with DLBCL treated with standard chemoimmunotherapy. Cellular distribution of LAG3 protein was determined by immunohistochemistry and flow cytometry. In tumor-infiltrating lymphocytes (TILs), LAG3 expression was highest on CD4+ regulatory T cells (Tregs) and was also highly expressed on CD8+ T cells compared with CD4+ non-Tregs (both P = .008). LAG3high TILs were enriched in PD-1 and TIM-3. LAG3 was also expressed on a proportion of malignant B cells, and these patients had significantly higher LAG3 messenger RNA in their biopsies (P = .03). LAG3high gene expression was associated with inferior survival in discovery/validation cohorts, independent of cell of origin and the international prognostic index. Patients who were PD-L1high were fivefold more likely to be LAG3high (P < .0001). Patients who were LAG3high/PD-L1high had an inferior progression-free survival (P = .011) and overall survival (P = .005) compared with patients who were LAG3low/PD-L1high. Digital spatial protein analysis confirms LAG3 expression on T cells and, surprisingly, tumor-associated macrophages (TAMs) at higher levels than found on CD20+ B cells in the tumor microenvironment. LAG3 is frequently expressed on CD4+ Tregs and CD8+ TILs, typically with other immune checkpoints, and is also present in a proportion of malignant B cells in DLBCL and in areas enriched for TAMs. LAG3high expression is associated with poor outcome independent of conventional prognosticators.
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