Prognostic impact of the bone marrow tumor microenvironment, HLA-I and HLA-Ib expression in MDS and CMML progression to sAML.

Genetic aberrations and immune escape are fundamental in MDS and CMML initiation and progression to sAML. Therefore, quantitative and spatial immune cell organization, expression of immune checkpoints (ICP), classical human leukocyte antigen class I (HLA-I) and the non-classical HLA-Ib antigens were analyzed in 274 neoplastic and 50 non-neoplastic bone marrow (BM) biopsies using conventional and multiplex immunohistochemistry and correlated to publicly available dataset. Higher numbers of tissue infiltrating lymphocytes (TILs) were found in MDS/CMML (8.8%) compared to sAML (7.5%) and non-neoplastic BM (5.3%). Higher T cell abundance, including the CD8+ T cell subset, inversely correlated with the number of pathogenic mutations and was associated with blast BM counts, ICP expression, spatial T cell distribution and improved patients' survival in MDS and CMML. In MDS/CMML, higher PD-1/PD-L1/PD-L2 and HLA-I, but lower HLA-G expression correlated with a significantly better patients' outcome. Moreover, a closer spatial proximity of T cell subpopulations and their proximity to myeloid blasts showed a stronger prognostic impact when compared to TIL numbers. In sAML - the continuum of MDS and CMML - the number of TILs had no impact on prognosis, but higher CD28 and HLA-I expression correlated with a better outcome of sAML patients. This study underlines the independent prognostic value of the tumor microenvironment in MDS/CMML progression to sAML, which shows the most pronounced immune escape. Moreover, new prognostic markers, like HLA-G expression and spatial T cell distribution, were described for the first time, which might also serve as therapeutic targets.

Identification and characterization of the anti-viral interferon lambda 3 as direct target of the Epstein-Barr virus microRNA-BART7-3p.

The human Epstein-Barr virus (EBV), as a member of the human γ herpes viruses (HHV), is known to be linked with distinct tumor types. It is a double-stranded DNA virus and its genome encodes among others for 48 different microRNAs (miRs). Current research demonstrated a strong involvement of certain EBV-miRs in molecular immune evasion mechanisms of infected cells by, e.g., the disruption of human leukocyte antigen (HLA) class Ia and NKG2D functions. To determine novel targets of EBV-miRs involved in immune surveillance, ebv-miR-BART7-3p, an EBV-encoded miR with high expression levels during the different lytic and latent EBV life cycle phases, was overexpressed in human HEK293T cells. Using a cDNA microarray-based comparative analysis, 234 (229 downregulated and 5 upregulated) deregulated human transcripts were identified in ebv-miR-BART7-3p transfectants, which were mainly involved in cellular processes and molecular binding. A statistically significant downregulation of the anti-proliferative and tumor-suppressive hsa-miR-34A and the anti-viral interferon lambda (IFNL)3 mRNA was found. The ebv-miR-BART7-3p-mediated downregulation of IFNL3 expression was due to a direct interaction with the IFNL3 3'-untranslated region (UTR) as determined by luciferase reporter gene assays including the identification of the accurate ebv-miR-BART7-3p binding site. The effect of ebv-miR-BART7-3p on the IFNL3 expression was validated both in human cell lines in vitro and in human tissue specimen with known EBV status. These results expand the current knowledge of EBV-encoded miRs and their role in immune evasion, pathogenesis and malignant transformation.