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| 2. |
- Arabi, A., et al.
(författare)
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Proteomic screen reveals Fbw7 as a modulator of the NF-kappa B pathway
- 2012
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 3, s. 976-
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Tidskriftsartikel (refereegranskat)abstract
- Fbw7 is a ubiquitin-ligase that targets several oncoproteins for proteolysis, but the full range of Fbw7 substrates is not known. Here we show that by performing quantitative proteomics combined with degron motif searches, we effectively screened for a more complete set of Fbw7 targets. We identify 89 putative Fbw7 substrates, including several disease-associated proteins. The transcription factor NF-κB2 (p100/p52) is one of the candidate Fbw7 substrates. We show that Fbw7 interacts with p100 via a conserved degron and that it promotes degradation of p100 in a GSK3 2 phosphorylation-dependent manner. Fbw7 inactivation increases p100 levels, which in the presence of NF-κB pathway stimuli, leads to increased p52 levels and activity. Accordingly, the apoptotic threshold can be increased by loss of Fbw7 in a p100-dependent manner. In conclusion, Fbw7-mediated destruction of p100 is a regulatory component restricting the response to NF-κB2 pathway stimulation.
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| 5. |
- Pokrovskaja, K, et al.
(författare)
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Proteasome inhibitor induces nucleolar translocation of Epstein-Barr virus-encoded EBNA-5
- 2001
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Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 82:Pt 2, s. 345-358
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that Epstein–Barr virus (EBV)-encoded EBNA-5 is localized to PML bodies (PODs) in EBV-immortalized lymphoblastoid cell lines (LCLs). Here we have extended our study of the subnuclear localization of EBNA-5 and found a strict co-localization with PML in LCLs and in BL lines with an immunoblastic, LCL-like phenotype. Moreover, GFP–EBNA-5 accumulated in PML bodies upon transfection into LCLs. In contrast, transfection of cell lines of non-immunoblastic origin with an EBNA-5 expression construct showed preferential localization of the protein to the nucleoplasm. Since PML is involved in proteasome-dependent protein degradation, we investigated the total levels and sub-cellular localization of EBNA-5 upon inhibition of proteasome activity. We found that a proteasome inhibitor, MG132, induced the translocation of both endogenous and transfected EBNA-5 to the nucleoli in every cell line tested. The total EBNA-5 protein levels were not affected by the proteasomal block. EBNA-5 forms complexes with heat shock protein Hsp70. The proteasome inhibitor induced a rise in total levels of Hsp70 and dramatically changed its homogeneous nuclear and cytoplasmic distribution into nucleolar and cytoplasmic. This effect was EBNA-5-independent. The nucleolar localization of Hsp70 was enhanced by the presence of EBNA-5, however. EBNA-5 also enhanced the nucleolar translocation of a mutant p53 in a colon cancer line, SW480, treated with MG132. The coordinated changes in EBNA-5 and Hsp70 localization and the effect of EBNA-5 on mutant p53 distribution upon MG132 treatment might reflect the involvement of EBNA-5 in the regulation of intracellular protein trafficking associated with the proteasome-mediated degradation.
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| 6. |
- Szekely, L, et al.
(författare)
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Human herpesvirus-8-encoded LNA-1 accumulates in heterochromatin- associated nuclear bodies
- 1999
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Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 8080 ( Pt 11), s. 2889-2900
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Tidskriftsartikel (refereegranskat)abstract
- Subnuclear distribution of the human herpesvirus-8 (HHV-8)- encoded nuclear protein LNA-1 was analysed at high resolution in body cavity (BC) lymphoma-derived cell lines, in cell hybrids between BC cells and various human and mouse cells and in freshly infected K562 and ECV cell lines. Three-dimensional reconstruction of nuclei from optical sections and quantitative analysis of the distribution of LNA-1 fluorescence in relation to chromatin showed that LNA-1 associates preferentially with the border of heterochromatin in the interphase nuclei. This was further confirmed in the following systems: in endo- and exonuclease-digested nuclei, in human–mouse (BC-1–Sp2- 0) hybrids and on chromatin spreads. LNA-1 was found to bind to mitotic chromosomes at random. Epstein–Barr virus (EBV), but not HHV-8, was rapidly lost from mouse–human hybrid cells in parallel with the loss of human chromosomes. HHV-8 could persist on the residual mouse background for more than 8 months. In early human–mouse hybrids that contain a single fused nucleus, LNA-1 preferentially associates with human chromatin. After the gradual loss of the human chromosomes, LNA-1 becomes associated with the murine pericentromeric heterochromatin. In human–human hybrids derived from the fusion of the HHV-8-carrying BCBL-1 cells and the EBV-immortalized lymphoblastoid cell line IB4, LNA-1 did not co-localize with EBNA-1, EBNA-2, EBNA-5 or EBNA-6. LNA-1 was not associated with PML containing ND10 bodies either. DNase but not RNase or detergent treatment of isolated nuclei destroys LNA-1 bodies. In advanced apoptotic cells LNA- 1 bodies remain intact but are not included in the apoptotic bodies themselves.
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| 8. |
- Buentke, E, et al.
(författare)
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Glucocorticoid-induced cell death is mediated through reduced glucose metabolism in lymphoid leukemia cells
- 2011
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Ingår i: Blood Cancer Journal. - : Macmillan Publishers Limited. - 2044-5385. ; 1:e31, s. 9-
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Tidskriftsartikel (refereegranskat)abstract
- Malignant cells are known to have increased glucose uptake and accelerated glucose metabolism. Using liquid chromatography and mass spectrometry, we found that treatment of acute lymphoblastic leukemia (ALL) cells with the glucocorticoid (GC) dexamethasone (Dex) resulted in profound inhibition of glycolysis. We thus demonstrate that Dex reduced glucose consumption, glucose utilization and glucose uptake by leukemic cells. Furthermore, Dex treatment decreased the levels of the plasma membrane-associated glucose transporter GLUT1, thus revealing the mechanism for the inhibition of glucose uptake. Inhibition of glucose uptake correlated with induction of cell death in ALL cell lines and in leukemic blasts from ALL patients cultured ex vivo. Addition of di-methyl succinate could partially overcome cell death induced by Dex in RS4;11 cells, thereby further supporting the notion that inhibition of glycolysis contributes to the induction of apoptosis. Finally, Dex killed RS4;11 cells significantly more efficiently when cultured in lower glucose concentrations suggesting that modulation of glucose levels might influence the effectiveness of GC treatment in ALL. In summary, our data show that GC treatment blocks glucose uptake by leukemic cells leading to inhibition of glycolysis and that these effects play an important role in the induction of cell death by these drugs.
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| 9. |
- Busker, S., et al.
(författare)
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Irreversible TrxR1 inhibitors block STAT3 activity and induce cancer cell death
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:12
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Tidskriftsartikel (refereegranskat)abstract
- Because of its key role in cancer development and progression, STAT3 has become an attractive target for developing new cancer therapeutics. While several STAT3 inhibitors have progressed to advanced stages of development, their underlying biology and mechanisms of action are often more complex than would be expected from specific binding to STAT3. Here, we have identified and optimized a series of compounds that block STAT3-dependent luciferase expression with nanomolar potency. Unexpectedly, our lead compounds did not bind to cellular STAT3 but to another prominent anticancer drug target, TrxR1. We further identified that TrxR1 inhibition induced Prx2 and STAT3 oxidation, which subsequently blocked STAT3-dependent transcription. Moreover, previously identified inhibitors of STAT3 were also found to inhibit TrxR1, and likewise, established TrxR1 inhibitors block STAT3-dependent transcriptional activity. These results provide new insights into the complexities of STAT3 redox regulation while highlighting a novel mechanism to block aberrant STAT3 signaling in cancer cells.
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| 13. |
- Herold, Nikolas, et al.
(författare)
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Targeting SAMHD1 with the Vpx protein to improve cytarabine therapy for hematological malignancies
- 2017
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Ingår i: Nature Medicine. - : Springer Science and Business Media LLC. - 1078-8956 .- 1546-170X. ; 23:2, s. 256-263
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Tidskriftsartikel (refereegranskat)abstract
- The cytostatic deoxycytidine analog cytarabine (ara-C) is the most active agent available against acute myelogenous leukemia (AML). Together with anthracyclines, ara-C forms the backbone of AML treatment for children and adults'. In AML, both the cytotoxicity of ara-C in vitro and the clinical response to ara-C therapy are correlated with the ability of AML blasts to accumulate the active metabolite ara-C triphosphate (ara-CTP)(2-5), which causes DNA damage through perturbation of DNA synthesis(6). Differences in expression levels of known transporters or metabolic enzymes relevant to ara-C only partially account for patient-specific differential ara-CTP accumulation in AML blasts and response to ara-C treatment(7-9). Here we demonstrate that the deoxynucleoside triphosphate (dNTP) triphosphohydrolase SAM domain and HD domain 1 (SAMHD1) promotes the detoxification of intracellular ara-CTP pools. Recombinant SAMHD1 exhibited ara-CTPase activity in vitro, and cells in which SAMHD1 expression was transiently reduced by treatment with the simian immunodeficiency virus (SIV) protein Vpx were dramatically more sensitive to ara-C-induced cytotoxicity. CRISPR-Cas9-mediated disruption of the gene encoding SAMHD1 sensitized cells to ara-C, and this sensitivity could be abrogated by ectopic expression of wild-type (WT), but not dNTPase-deficient, SAMHD1. Mouse models of AML lacking SAMHD1 were hypersensitive to ara-C, and treatment ex vivo with Vpx sensitized primary patient derived AML blasts to ara-C. Finally, we identified SAMHD1 as a risk factor in cohorts of both pediatric and adult patients with de novo AML who received ara-C treatment. Thus, SAMHD1 expression levels dictate patient sensitivity to ara-C, providing proof-of-concept that the targeting of SAMHD1 by Vpx could be an attractive therapeutic strategy for potentiating ara-C efficacy in hematological malignancies.
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| 22. |
- Panaretakis, T, et al.
(författare)
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Doxorubicin requires the sequential activation of caspase-2, protein kinase Cdelta, and c-Jun NH2-terminal kinase to induce apoptosis
- 2005
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Ingår i: Molecular biology of the cell. - : American Society for Cell Biology (ASCB). - 1059-1524 .- 1939-4586. ; 16:8, s. 3821-3831
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Tidskriftsartikel (refereegranskat)abstract
- Here, we identified caspase-2, protein kinase C (PKC)δ, and c-Jun NH2-terminal kinase (JNK) as key components of the doxorubicin-induced apoptotic cascade. Using cells stably transfected with an antisense construct for caspase-2 (AS2) as well as a chemical caspase-2 inhibitor, we demonstrate that caspase-2 is required in doxorubicin-induced apoptosis. We also identified PKCδ as a novel caspase-2 substrate. PKCδ was cleaved/activated in a caspase-2–dependent manner after doxorubicin treatment both in cells and in vitro. PKCδ is furthermore required for efficient doxorubicin-induced apoptosis because its chemical inhibition as well as adenoviral expression of a kinase dead (KD) mutant of PKCδ severely attenuated doxorubicin-induced apoptosis. Furthermore, PKCδ and JNK inhibition show that PKCδ lies upstream of JNK in doxorubicin-induced death. Jnk-deficient mouse embryo fibroblasts (MEFs) were highly resistant to doxorubicin compared with wild type (WT), as were WT Jurkat cells treated with SP600125, further supporting the importance of JNK in doxorubicin-induced apoptosis. Chemical inhibitors for PKCδ and JNK do not synergize and do not function in doxorubicin-treated AS2 cells. Caspase-2, PKCδ, and JNK were furthermore implicated in doxorubicin-induced apoptosis of primary acute lymphoblastic leukemia blasts. The data thus support a sequential model involving caspase-2, PKCδ, and JNK signaling in response to doxorubicin, leading to the activation of Bak and execution of apoptosis.
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| 24. |
- Pilheden, Mattias, et al.
(författare)
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Duplex sequencing uncovers recurrent low-frequency cancer-associated mutations in infant and childhood KMT2A-rearranged acute leukemia
- 2022
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Ingår i: HemaSphere. - : Wolters Kluwer. - 2572-9241. ; 6:10
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Tidskriftsartikel (refereegranskat)abstract
- Infant acute lymphoblastic leukemia (ALL) with KMT2A-gene rearrangements (KMT2A-r) have few mutations and a poor prognosis. To uncover mutations that are below the detection of standard next-generation sequencing (NGS), a combination of targeted duplex sequencing and NGS was applied on 20 infants and 7 children with KMT2A-r ALL, 5 longitudinal and 6 paired relapse samples. Of identified nonsynonymous mutations, 87 had been previously implicated in cancer and targeted genes recurrently altered in KMT2A-r leukemia and included mutations in KRAS, NRAS, FLT3, TP53, PIK3CA, PAX5, PIK3R1, and PTPN11, with infants having fewer such mutations. Of identified cancer-associated mutations, 62% were below the resolution of standard NGS. Only 33 of 87 mutations exceeded 2% of cellular prevalence and most-targeted PI3K/RAS genes (31/33) and typically KRAS/NRAS. Five patients only had low-frequency PI3K/RAS mutations without a higher-frequency signaling mutation. Further, drug-resistant clones with FLT3D835H or NRASG13D/G12S mutations that comprised only 0.06% to 0.34% of diagnostic cells, expanded at relapse. Finally, in longitudinal samples, the relapse clone persisted as a minor subclone from diagnosis and through treatment before expanding during the last month of disease. Together, we demonstrate that infant and childhood KMT2A-r ALL harbor low-frequency cancer-associated mutations, implying a vast subclonal genetic landscape.
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