Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Oncogenic MyD88 Mutants Require Toll-like Receptors

ABSTRACT: In the activated B-cell-like (ABC) subtype of diffuse large B cell lymphoma (DLBCL), the most frequent gain-of-function mutations target MyD88, a signaling adapter for Tolllike receptors (TLRs). The most prevalent oncogenic mutant, MyD88 L265P, occurs in 29% of cases and is the most active in engaging the NF-kappaB pathway. Here we show that MyD88 mutants do not function autonomously, but rather require TLR7, TLR9, and to a lesser extent, TLR4 to promote the survival of ABC DLBCL cells. Unlike wild type MyD88, MyD88 mutants associate constitutively with TLR7 and TLR9 in ABC DLBCL cells. Like ligand-induced TLR7/9 signaling in normal immune cells, the survival of ABC DLBCL cell lines depends upon translocation of TLR7 and TLR9 to acidic endolysosomes, where proteolytic processing of their ligand binding ectodomains is required for their oncogenic signaling. ABC DLBCL viability also depends upon CD14, a co-receptor for TLR7 and TLR9 that promotes engagement of nucleic acid ligands by these receptors. Point mutations in the TLR7 or TLR9 ectodomains that abrogate ligand binding and/or signaling were incapable of sustaining ABC DLBCL survival. An inhibitory oligonucleotide that suppresses TLR9 responses in normal B cells blocked NF-kappaB signaling and survival of ABC DLBCL lines. Together, these data suggest that an endogenous TLR ligand may play a pathogenic role in ABC DLBCL and provide a rationale for targeting TLR signaling to improve therapy of this aggressive lymphoma. Gene expression was analyzed using Agilent human 2-color 4X44K oligo gene expression arrays. Cell line, TMD8 ABC-DLBCL, was infected with control (shControl, Cy3), shLTR7 (Cy5) or shLTR9 (Cy5) and changes in gene expression were monitored on day 1 and day 2 after induction of the shRNA with doxycycline, co-hybridizing control and experimental samples (Cy3+Cy5), for a total of 4 arrays.

ORGANISM(S): Homo sapiens

SUBMITTER: Louis Staudt

PROVIDER: E-GEOD-47147 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

Project description:Interferon regulatory factor 4 (IRF4) is a transcriptional regulator with critical roles in the normal development and malignant transformation of lymphocytes. Recently we have shown that plasma cell cancers (multiple myeloma, MM) are addicted to an aberrant gene expression program ochestrated by wild-type IRF4 for their survival. Here we show that an aggressive malignancy of mature B cells, the activated B cell for of Diffuse Large B Cell lymphoma (ABC-DLBC), also depends on IRF4 for survival. With genome-wide expression profiling and localization (ChIP-Seq) assays, we identified IRF4 target genes in ABC-DLBCL as members of diverse pathways related to B cell biology and malignant behavior, distinct from IRF4 targets in MM. For example, we find the gene encoding the NFkB signal transduction adapter protein CARD11 is a target of IRF4 activation, driving the critical NFkB pathway in ABC-DLBCL. Further, we find enrichment of DNA binding motifs for ETS-IRF factors in regions of IRF4 binding in ABC-DLBCL suggesting cooperative activity between IRF4 and an ETS family transcription factor. Through complementation assays we show that IRF4 and the critical ABC-DLBCL ETS factor SPIB interact with one another and are key to ABC-DLBCL survival. Together our data show that ABC-DLBCL is addicted to the interaction between IRF4 and SPIB, in part through a positive feedback loop invovling CARD11 and the activation of the NFkB pathway. These data suggest theraepeutic potential in targeting the IRF4:SPIB interface in ABC-DLBCL. Gene expression was analyzed using Agilent human 4X44K oligo gene expression arrays. Cell lines (HBL1, OCILY3, TMD8-ABC-DLBCL; KMS12-MM) were infected with control (shControl, Cy3) or shIRF4_3'UTR (Cy5) constructs, and changes in gene expression were monitored over time after induction of the shRNA with doxycyclin. For each of the three ABC-DLBCL cell line a four timepoint series (24, 48, 72, 96 hrs) of shRNA induction was analyzed, for a total of 12 arrays. In HBL-1 a second shRNA targeting the IRF4 cds (shIRF4_cds) was used in a similar time course of shRNA induction (4 arrays). For the KMS12 MM cell line a three point time course was analyzed using the shIRF4_3'UTR with one technical (using the same RNA sample) duplicate time point measurement (4 arrays). ChIP-Seq data not provided.

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Oncogenic MyD88 Mutants Require Toll-like Receptors

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