MicroRNAs Are Differentially Expressed in Primary Central Nervous (CNS) and Nodal Diffuse Large B-Cell Lymphomas.
Authors: Fischer Lars , Hummel Michael , Korfel Agnieszka , Lenze Dido , Jöhrens Korinna , Thiel Eckhard 
Published: October 2019

Abstract
Abstract 2929
Poster Board II-905
Primary CNS lymphoma (PCNSL) is a rare subtype of diffuse large B-cell lymphoma (DLBCL) confined exclusively to the CNS. Mechanisms leading to lymphoma development in the immunoprivileged CNS are still not fully understood. MicroRNAs (miR) play key regulatory roles in eukaryotic gene expression. Recently aberrant miR expression has been demonstrated in several lymphoma entities. We investigated the expression pattern of miR in PCNSL using a wide panel of miRNA-species and compared it to nodal DLBCL. Biopsy samples derived from newly diagnosed PCNSL and nodal DLBCL were subtyped immunohistologically into a GCB- and non-GCB type according to the Hans classifier (CD10, BCL6, MUM1). Total RNA was extracted from formalin-fixed and paraffin-embedded tissue sections and reverse transcribed using eight predefined primer pools containing up to 48 multiplex RT primers each. Gene expression was measured by quantitative real-time (RT) PCR using commercially available TaqMan low density arrays (TLDA). Each TLDA contained specific primer-probe combinations for 365 miRNA species, 3 small nuclear RNAs serving as endogenous controls and 2 negative controls. Each RT-PCR was run in duplicate. Only miRNA with a Ct value of ≤37 in both replicates were considered being present in the sample. Normalized expression levels were calculated using the 2-ΔCT method. Mean expression levels in PCNSL and nodal DLBCL of each miRNA were compared using the Mann-Whitney-U test. Twenty one samples were analyzed; 11 PCNSL: 6 non-GCB, 4 GCB, and 1 non-classifiable type, and 10 nodal DLBCL: 5 non-GCB and 5 GCB type (χ2, p=0.65). Of 365 miR species 29% and 33% were detected in more than half of the samples of DLBCL and PCNSL respectively. The expression of 11 miR was significantly higher in PCNSL, and of 5 miR lower compared to DLBCL. Expression levels differed from 3.9-fold upregulation to 4.4-fold downregulation (Table). Comparing miR expression according to GCB-type across all samples, only 3 miR were significantly different. Those miR were dissimilar from the 16 miR differentially expressed in PCNSL and DLBCL.
This is the first report demonstrating a differential expression of a wide panel of specific miRNA in PCNSL and nodal DLBCL. Several of the differentially expressed miRNA have been implicated in pathways promoting tumor cell survival and angiogenesis. Two members of the miR-17-92 cluster (miR-17-5p and miR-20a) known to be involved in B-cell lymphomagenesis by induction through c-myc and by targeting of CDKN1A(p21) were upregulated in PCNSL. MiR-155 which is induced by B-cell receptor activation is overexpressed in various B-cell lymphomas and has prognostic value in ABC-type DLBCL. The miR-30 family and miR-9 are regulators in the GC to plasma cell transition. PCNSL were further characterized by downregulation of tumor suppressor miRNAs (miR-145, miR-199a) and upregulation of oncogenic miRNAs like miR27b or an inhibitor of innate immune responses (miR-146b).
Thus, exacerbated dysregulation of miRNAs may contribute to the localization and poor prognosis of PCNSL.Table:MiRNA species which differed significantly in expressionmicroRNA Expression level PCNSL/DLBCLphsa-miR-17-5p3.880.012hsa-miR-1553.270.008hsa-miR-92.780.006hsa-miR-20a2.700.029hsa-miR-30b2.620.003hsa-miR-27b2.580.008hsa-miR-146b2.440.010hsa-miR-26b1.910.029hsa-let-7g1.840.006hsa-miR-30c1.780.024hsa-miR-251.620.035hsa-miR-5940.490.010hsa-miR-193b0.400.027hsa-miR-1450.340.007hsa-miR-199a0.250.009hsa-miR-2140.230.004GCB/non-GCBhsa-miR-181d2.760.036hsa-miR-3422.670.031hsa-miR-29c1.500.012

Disclosures:
No relevant conflicts of interest to declare.