Unknown,Transcriptomics,Genomics,Proteomics

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Compensatory IKKa activation of classical NF-kB signaling during IKKb inhibition

ABSTRACT: A subtype of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like (ABC) DLBCL, depends on constitutive NF-kB pathway signaling for survival. Small molecule inhibitors of IkB kinase b (IKKb), a key regulator of the NF-kB pathway, kill ABC DLBCL cells and hold promise for the treatment of this lymphoma type. We conducted an RNA interference genetic screen to investigate potential mechanisms of resistance of ABC DLBCL cells to IKKb inhibitors. We screened a library of small hairpin RNAs (shRNAs) targeting 500 protein kinases for shRNAs that would kill an ABC DLBCL cell line in the presence of a small molecule IKKb inhibitor more effectively than in its absence. Two independent shRNAs targeting IKKa synergized with the IKKb inhibitor to kill three different ABC DLBCL cell lines but were not toxic by themselves. Surprisingly, IKKa shRNAs blocked the classical rather than the alternative NF-kB pathway in ABC DLBCL cells, as judged by inhibition of IkBa phosphorylation. IKKa shRNA toxicity was reversed by coexpression of wild type but not kinase inactive forms of IKKa, suggesting that IKKa may directly phosphorylate IkBa under conditions of IKKb inhibition. These results suggest that therapy for ABC DLBCL may be improved by targeting both IKKa and IKKb. Keywords: compound treatment design Gene expression profiling of OCI-Ly3 cells with or without expressing IKKa shRNA in the presence or absence of 12.5 uM IKKb inhibitor for 2 and 3 days. Four samples were analyzed.

ORGANISM(S): Homo sapiens

SUBMITTER: Louis Staudt

PROVIDER: E-GEOD-11902 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Compensatory IKKalpha activation of classical NF-kappaB signaling during IKKbeta inhibition identified by an RNA interference sensitization screen.

Lam Lloyd T LT Davis R Eric RE Ngo Vu N VN Lenz Georg G Wright George G Xu Weihong W Zhao Hong H Yu Xin X Dang Lenny L Staudt Louis M LM

Proceedings of the National Academy of Sciences of the United States of America 20081222 52

A subtype of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like (ABC) DLBCL, depends on constitutive nuclear factor-kappaB (NF-kappaB) signaling for survival. Small molecule inhibitors of IkappaB kinase beta (IKKbeta), a key regulator of the NF-kappaB pathway, kill ABC DLBCL cells and hold promise for the treatment of this lymphoma type. We conducted an RNA interference genetic screen to investigate potential mechanisms of resistance of ABC DLBCL cells to IKKbeta inhibitors. We ...[more]

PMID: 19104039

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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:The activated B cell-like (ABC) subgroup of diffuse large B cell lymphoma (DLBCL) is characterized by constitutive activation of the NF-ÃªB pathway. Here we show that the NF- ÃªB pathway induces the expression of the cytokines IL-6 and IL-10 in ABC DLBCL cell lines, which also have high levels of total and phosphorylated STAT3 protein, suggesting autocrine signaling. Using RNA interference for STAT3, we defined a gene expression signature of IL-6 and IL-10 signaling through STAT3. Based on this signature, we constructed a molecular predictor of STAT3 signaling that defined a subset of ABC DLBCL tumors with high expression of STAT3, IL-6 and/or IL-10, and their downstream targets. Although the STAT3-high and STAT3-low subsets had equivalent expression of genes that distinguish ABC DLBCL from GCB DLBCL, STAT3-high ABC DLBCLs had higher expression of signatures that reflected NF-kB activity, proliferation, and glycolysis. A smallmolecule inhibitor of JAK signaling, which blocked STAT3 signature expression, was toxic only for ABC DLBCL lines, and synergized with an inhibitor of NF-kB signaling. These findings suggest that the biological interplay between the STAT3 and NF-kB pathways may be exploited for the treatments of a subset of ABC DLBCLs. Activated B cell-like (ABC) subgroup of diffuse large B cell lymphoma (DLBCL) cell lines were used as model systems to study the cytokine pathways in these cells. We expressed inducible IkB super-repressor for 1 to 24 hours to identify NF-kB target genes in OCI-Ly3 and OCI-Ly10 cells for a total of 13 arrays with replicates of each time point. We treated OCI-Ly3 cells with IL-10 for 1 to 96 hours for a total of 10 arrays with replicates of each time point. We treated OCI-Ly10 cells with IL-6 for 30 minutes to 24 hours for a total of 8 arrays with replicates of each time point. OCI-Ly10 cells transfected with no siRNA versus STAT3-siRNA for 8, 24, or 48 hours for a total of 5 arrays with replicates for 24 and 48 hours. We treated OCI-Ly10 cells with JAK inhibitor I for 3 and 6 hours for a total of 4 arrays with replicates of each time point.

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.

Dataset Information

Compensatory IKKa activation of classical NF-kB signaling during IKKb inhibition

Publications

Compensatory IKKalpha activation of classical NF-kappaB signaling during IKKbeta inhibition identified by an RNA interference sensitization screen.

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