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DLBCL-reminiscent MyD88- or CARD11-mutant aggressive B-cell lymphomas exhibit strong pro-senescent and immune-evasive phenotypes [part2]

ABSTRACT: Aberrant B-cell receptor (BCR)/NF-kB signaling activity is a prominent feature of diffuse large B-cell lymphoma (DLBCL), particularly of, but not restricted to the activated B-cell (ABC) subtype. Recurrent mutations in this cascade, e.g. in CD79B, CARD11, A20/TNFAIP3 or NFKBIZ, but also in the Toll-like receptor (TLR) pathway transducer MyD88, all converge at NF-kB deregulation, but their differential impact on lymphoma development and biology remains to be dissected. Recapitulating oncogenic myc rearrangements as another common feature of DLBCL, we functionally investigate here primary mouse lymphomas that formed after propagation of Eµ-myc transgenic hematopoietic stem cells (HSC), stably transduced with naturally occurring DLBCL-derived NF-kB mutants, in recipient mice. While most mutants tested supported Myc-driven lymphoma formation through repressed apoptosis, selectively deregulated CARD11- or MyD88-mutant lymphoma cells presented with a macrophage-activating secretion profile, which, in turn, enforced TGF-b-mediated feedback senescence in the lymphoma cell compartment. Moreover, MyD88- or CARD11-mutant Eµ-myc lymphomas – mirrored by matching signatures in their mutant DLBCL counterparts – exhibited high-level expression of the immune checkpoint mediator PD-L1, thus preventing their efficient clearance by adaptive host cell immunity. Conversely, these mutant-specific dependencies were therapeutically exploitable by anti-PD1 immune checkpoint blockade, leading to the direct T-cell-mediated lysis of predominantly but not exclusively senescent lymphoma cells. Our functional, cross-species interrogation of a syngeneic and fully immune-competent, BCR/NF-kB-deregulated and DLBCL-reminiscent in vivo-model platform unveils common principles and therapeutic vulnerabilities related to human DLBCL subsets that will inform future personalized treatment strategies. Specifically, for the shown FLC transplantation experiments, 8-12 week-old female C57BL/6N recipient mice (Charles River Laboratories) received a single, myelo-ablative dose of 9 Gy total-body gamma-irradiation. After in vitro-transduction of FLC, 10% GFP-positive Sca1+; c-Kit+; lin- cells with the indictaed transgenic and/or knock out genotypes were transplanted via tail vein injection into irradiated mice, which were subsequently monitored until a well-palpable lymphadenopathy had formed. Retroviral vectors used in this experiment were the MSCV 2.2 derived constructs

ORGANISM(S): Mus musculus

PROVIDER: GSE141453 | GEO | 2020/12/07

REPOSITORIES: GEO

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Project description:Diffuse large B-cell lymphoma (DLBCL), the most common form of lymphoma in adulthood, comprises multiple biologically and clinically distinct subtypes including germinal center B cell-like (GCB) and activated B cell like (ABC) DLBCL. Gene expression profile studies have shown that its most aggressive subtype, ABC-DLBCL, is associated with constitutive activation of the NF-kB transcription complex. However, except for a small fraction of cases, it remains unclear whether NF-kB activation in these tumors represents an intrinsic program of the tumor cell of origin or a pathogenetic event. Here we show that >50% of ABC-DLBCL and a smaller fraction of GCB-DLBCL carry somatic mutations at multiple genes, including negative (TNFAIP3/A20) and positive (CARD11, TRAF2, TRAF5, MAP3K7/TAK1 and TNFRSF11A/RANK) regulators of NF-kB. Of these, the A20 gene, which encodes for a ubiquitin-modifying enzyme involved in termination of NF-kB responses, is the most commonly affected one, with ~30% of the patients displaying biallelic inactivation by mutations and/or deletions, suggesting a tumor suppressor role. Less frequently, missense mutations of TRAF2 and CARD11 produce molecules with significantly enhanced ability to activate NF-kB. Thus, our results demonstrate that NF-kB activation in DLBCL is caused by genetic lesions affecting multiple genes, whose loss or activation may promote lymphomagenesis by leading to abnormally prolonged NF-kB responses. We show that most ABC-DLBCL and a smaller fraction of GCB-DLBCL display genetic lesions affecting multiple NFkB pathway genes, with A20 representing the most frequently mutated gene Experiment Overall Design: DLBCL biopsies from 73 patients were collected from the archives of the Departments of Pathology at Columbia University and Weill Cornell Medical College. Total RNA was extracted from frozen tumor biopsies and processed according to Affymetrix standard protocols. Purified tonsillar geminal center cells (centroblasts and centrocytes, 5 samples each from different individuals) were purified by magnetic cell separation as described in Klein et al, PNAS 2003.

Project description:The ABC subtype of diffuse large B cell lymphoma (DLBCL) remains the least curable form of this lymphoma despite recent advances in therapy. We have combined structural and functional genomics to triangulate on new oncogenic mechanisms and devise new therapeutic strategies. RNA interference screen revealed a dependence of ABC DLBCL cell lines on MYD88 and IRAK1. High throughput resequencing of RNA (RNA-Seq) revealed frequent somatic mutations in MYD88 that preferentially occurred in the ABC DLBCL subtype. Remarkably, one third of ABC DLBCL tumor samples harbored the same amino acid substitution, L265P, in the MYD88 TIR domain at an evolutionarily invariant residue in its hydrophobic core. This mutation was rare or absent in two other DLBCL subtypes, but was observed in 9% of MALT lymphomas. At a lower frequency, multiple other mutations were observed in the MYD88 TIR domain, occurring in both the ABC and GCB subtypes of DLBCL. Survival of ABC DLBCL lines bearing the L265P mutation was sustained by the mutant but not wild type MYD88 isoform, demonstrating that this MYD88 mutant is oncogenic and gain-of-function. The MYD88 L265P mutant assembled a protein complex that spontaneous triggers the phosphorylation of IRAK1, leading to NF-kB signaling, secretion of the cytokines IL-6, IL-10 and interferon-b, and JAK kinase signaling. These findings demonstrate that the MYD88 signaling pathway is integral to the pathogenesis of ABC DLBCL, providing a genetic rationale for therapeutic targeting of the MYD88 signaling pathway in this lymphoma subtype. To generate a gene expression signature of MYD88 signaling in ABC DLBCL, the HBL-1 cell line was transduced with retroviral vectors expressing either shMYD88-4 or shMYD88-7. Following puromycin selection, shRNA expression was induced for 24 or 48 hours and gene expression was measured, comparing uninduced (Cy3) to induced (Cy5) cells, using genome-wide Agilent 4x44K oligonucleotide microarrays. A signature of NF-kB signaling in ABC DLBCL was generated by treating HBL-1 cells with the IkB kinase beta inhibitor MLN120B for 2h, 3h, 4h, 6h, 8h, 12h, 16h, and 24h (Cy5), and comparing their gene expression to untreated cells (Cy3). A signature of JAK signaling in ABC DLBCL was generated by treating HBL-1 cells with JAK inhibitor I (5 micromolar; Calbiochem) for 2h, 4h, 6h, and 8h (Cy5) and comparing their gene expression to vehicle-treated cells (DMSO, Cy3). RNA-Seq data not provided.

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DLBCL-reminiscent MyD88- or CARD11-mutant aggressive B-cell lymphomas exhibit strong pro-senescent and immune-evasive phenotypes [part2]

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