Inhibition of CRM1-Mediated Nuclear Export of Transcription FACTORS by Leukemogenic NUP98 Fusion Proteins.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1959-1959
Author(s):  
Akiko Takeda ◽  
Anmaar M Abdul-Nabi ◽  
Nabeel R. Yaseen
Keyword(s):  
Transcription Factors ◽  
Nuclear Export ◽  
Fusion Proteins ◽  
Conflicts Of Interest ◽  
Nuclear Accumulation ◽  
Human Leukemia ◽  
Dependent Manner ◽  
Nucleocytoplasmic Trafficking ◽  
Nuclear Retention

Abstract Abstract 1959 Poster Board I-982 NUP98 is a nucleoporin that plays complex roles in the nucleocytoplasmic trafficking of macromolecules. Rearrangements of the NUP98 gene in human leukemia result in the expression of numerous fusion oncoproteins whose effect on nucleocytoplasmic trafficking is poorly understood. The present study was undertaken to determine the effects of leukemogenic NUP98 fusion proteins on CRM1-mediated nuclear export. NUP98-HOXA9, a prototypic NUP98 fusion, inhibited the nuclear export of two known CRM1 substrates: mutated cytoplasmic nucleophosmin (NPMc) and HIV-1 Rev. In-vitro binding assays revealed that NUP98-HOXA9 binds CRM1 through the FG-repeat motif in a Ran-GTP dependent manner similar to but stronger than the interaction between CRM1 and its export substrates. Two NUP98 fusions, NUP98-HOXA9 and NUP98-DDX10, whose fusion partners are structurally and functionally unrelated, interacted with endogenous CRM1 in cells as shown by co-immunoprecipitation. These leukemogenic NUP98 fusion proteins interacted with CRM1, Ran, and the nucleoporin NUP214 in a manner fundamentally different from that of wild-type NUP98. NUP98-HOXA9 and NUP98-DDX10 formed characteristic aggregates within the nuclei of myeloid cells and caused aberrant localization of CRM1 to these aggregates. These NUP98 fusions caused nuclear accumulation of two transcription factors, NFAT and NFΚB, that are regulated by CRM1-mediated export. The nuclear entrapment of NFAT and NFΚB correlated with enhanced transcription from promoters responsive to these transcription factors. Taken together, the results suggest a new mechanism by which NUP98 fusions dysregulate transcription and cause leukemia, namely, inhibition of CRM1-mediated nuclear export with aberrant nuclear retention of transcriptional regulators. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The Mechanism of Nuclear Export of Smad3 Involves Exportin 4 and Ran

2006 ◽  
Vol 26 (4) ◽  
pp. 1318-1332 ◽  
Author(s):  
Akira Kurisaki ◽  
Keiko Kurisaki ◽  
Marcin Kowanetz ◽  
Hiromu Sugino ◽  
Yoshihiro Yoneda ◽  
...  
Keyword(s):  
Transforming Growth Factor Beta ◽  
Nuclear Export ◽  
Transforming Growth Factor ◽  
Peptide Sequence ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Nucleotide Exchange ◽  
Interaction Domain

ABSTRACT Transforming growth factor beta (TGF-β) receptors phosphorylate Smad3 and induce its nuclear import so it can regulate gene transcription. Smad3 can return to the cytoplasm to propagate further cycles of signal transduction or to be degraded. We demonstrate that Smad3 is exported by a constitutive mechanism that is insensitive to leptomycin B. The Mad homology 2 (MH2) domain is responsible for Smad3 export, which requires the GTPase Ran. Inactive, GDP-locked RanT24N or nuclear microinjection of Ran GTPase activating protein 1 blocked Smad3 export. Inactivation of the Ran guanine nucleotide exchange factor RCC1 inhibited Smad3 export and led to nuclear accumulation of phosphorylated Smad3. A screen for importin/exportin family members that associate with Smad3 identified exportin 4, which binds a conserved peptide sequence in the MH2 domain of Smad3 in a Ran-dependent manner. Exportin 4 is sufficient for carrying the in vitro nuclear export of Smad3 in cooperation with Ran. Knockdown of endogenous exportin 4 completely abrogates the export of endogenous Smad3. A short peptide representing the minimal interaction domain in Smad3 effectively competes with Smad3 association to exportin 4 and blocks nuclear export of Smad3 in vivo. We thus delineate a novel nuclear export pathway for Smad3.

scholarly journals CTNI-18. FINAL RESULTS OF A PHASE 2 STUDY OF EFFICACY, SAFETY AND INTRATUMORAL PHARMACOKINETICS (PK) OF SELINEXOR MONOTHERAPY IN RECURRENT GLIOBLASTOMA (rGBM)

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii46-ii46
Author(s):  
Andrew Lassman ◽  
Patrick Wen ◽  
Martin van den Bent ◽  
Scott Plotkin ◽  
Annemiek Walenkamp ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Phase 1 ◽  
Progression Free Survival ◽  
Median Number ◽  
Recurrent Glioblastoma ◽  
Phase 2 ◽  
Nuclear Retention ◽  
Phase 2 Trial ◽  
Human Gbm

Abstract BACKGROUND Selinexor is an FDA-approved first-in-class, oral selective nuclear export inhibitor which forces nuclear retention of many tumor suppressor proteins. METHODS We conducted a phase 2 trial of selinexor monotherapy for adults with recurrent GBM including a surgical arm to explore intratumoral PK and 3 medical arms to optimize dosing. Prior treatment with radiotherapy and temozolomide was required; prior bevacizumab was exclusionary. The primary endpoint was 6-month progression-free survival (6mPFS) rate. RESULTS Selinexor administered ~2 hours pre-operatively yieleded average intratumoral concentration (136 nM, n=6) comparable to the in vitro IC50 (130 nM) from 7 primary human GBM cell lines. Among all 68 patients accrued to 3 medical arms (~85 mg BIW, n=24; 60 mg BIW, n=14; 80 mg QW, n=30), median age was 56 years (21–78). Median number of prior lines of therapies was 2 (1–7). At 80 mg QW, 28% patients were progression-free at the end of cycle 6; the 6mPFS was 17%; disese control rate by RANO was 37% (1 CR, 2 PRs, 7 SD) among 27 evaluable patients; responses were durable (median 11.1 months), and treatment lasted for 442, 547 and 1282 days in 3 responders, as of data lock, with one responder remaining on treatment off study; median overall survival was 10.2 months with 95% CI (7.0, 15.4). The ~85 mg BIW-schedule was abandoned due to poor tolerability. The related adverse events (all grades) in patients on ~85 mg BIW/60 mg BIW/80 mg QW were nausea (41.7%/64.3%/66.7%), fatigue (70.8%/71.4%/50.0%), neutropenia (29.2%/14.3%/33.3%), decreased appetite (45.8%/71.4%/26.7%), thrombocytopenia (66.7%/28.6%/23.3%) and weight loss (16.7%,/42.9%/6.7%). CONCLUSION Selinexor monotherapy demonstrated encouraging intratumoral penetration and efficacy, with durable disease control in rGBM. Monotherapy dose at 80 mg QW is recommended for further development in rGBM. A phase 1/2 study of combination therapy for newly diagnosed or rGBM has been initiated (NCT04421378).

scholarly journals Multicomponent differentiation-regulated transcription factors in F9 embryonal carcinoma stem cells.

1991 ◽  
Vol 11 (3) ◽  
pp. 1686-1695 ◽  
Author(s):  
M K Shivji ◽  
N B La Thangue
Keyword(s):  
Stem Cells ◽  
Transcription Factors ◽  
Dna Binding ◽  
Embryonal Carcinoma ◽  
Regulatory Sequence ◽  
Dependent Manner ◽  
Sequence Specificity ◽  
Dna Sequence Specificity ◽  
Cell Extracts

Murine F9 embryonal carcinoma (F9 EC) stem cells have an E1a-like transcription activity that is down-regulated as these cells differentiate to parietal endoderm. For the adenovirus E2A promoter, this activity requires at least two sequence-specific transcription factors, one that binds the cyclic AMP-responsive element (CRE) and the other, DRTF1, the DNA-binding activity of which is down-regulated as F9 EC cells differentiate. Here we report the characterization of several binding activities in F9 EC cell extracts, referred to as DRTF 1a, 1b and 1c, that recognize the DRTF1 cis-regulatory sequence (-70 to -50 region). These activities can be chromatographically separated but are not distinguishable by DNA sequence specificity. Activity 1a is a detergent-sensitive complex in which DNA binding is regulated by phosphorylation. In contrast, activities 1b and 1c are unaffected by these treatments but exist as multicomponent protein complexes even before DNA binding. Two sets of DNA-binding polypeptides, p50DR and p30DR, affinity purified from F9 EC cell extracts produce complexes 1b and 1c. Both polypeptides appear to be present in the same DNA-bound protein complex and both directly contact DNA. These affinity-purified polypeptides activate transcription in vitro in a binding-site-dependent manner. These data indicate the in F9 EC stem cells, multicomponent differentiation-regulated transcription factors contribute to the cellular E1a-like activity.

scholarly journals Activating Signal Cointegrator 2 Belongs to a Novel Steady-State Complex That Contains a Subset of Trithorax Group Proteins

2003 ◽  
Vol 23 (1) ◽  
pp. 140-149 ◽  
Author(s):  
Young-Hwa Goo ◽  
Young Chang Sohn ◽  
Dae-Hwan Kim ◽  
Seung-Whan Kim ◽  
Min-Jung Kang ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Steady State ◽  
Nuclear Receptors ◽  
Transcriptional Activation ◽  
Retinoic Acid Receptor ◽  
Dependent Manner ◽  
Trithorax Group ◽  
Trithorax Group Proteins

ABSTRACT Many transcription coactivators interact with nuclear receptors in a ligand- and C-terminal transactivation function (AF2)-dependent manner. These include activating signal cointegrator 2 (ASC-2), a recently isolated transcriptional coactivator molecule, which is amplified in human cancers and stimulates transactivation by nuclear receptors and numerous other transcription factors. In this report, we show that ASC-2 belongs to a steady-state complex of approximately 2 MDa (ASC-2 complex [ASCOM]) in HeLa nuclei. ASCOM contains retinoblastoma-binding protein RBQ-3, α/β-tubulins, and trithorax group proteins ALR-1, ALR-2, HALR, and ASH2. In particular, ALR-1/2 and HALR contain a highly conserved 130- to 140-amino-acid motif termed the SET domain, which was recently implicated in histone H3 lysine-specific methylation activities. Indeed, recombinant ALR-1, HALR, and immunopurified ASCOM exhibit very weak but specific H3-lysine 4 methylation activities in vitro, and transactivation by retinoic acid receptor appears to involve ligand-dependent recruitment of ASCOM and subsequent transient H3-lysine 4 methylation of the promoter region in vivo. Thus, ASCOM may represent a distinct coactivator complex of nuclear receptors. Further characterization of ASCOM will lead to a better understanding of how nuclear receptors and other transcription factors mediate transcriptional activation.

Comparison of the Effects on Reversal of Multi-Drug Resistance of 5-Bromotetrandrine and Tetrandrine in K562/A02 Cell Line in Vivo and in Vitro

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5059-5059
Author(s):  
Bao-An Chen ◽  
Jue-qiong Wang ◽  
Jian Cheng ◽  
Feng Gao ◽  
Wen-lin Xu ◽  
...  
Keyword(s):  
Cell Line ◽  
Nude Mice ◽  
Leukemia Cell Line ◽  
Multi Drug Resistance ◽  
Human Leukemia ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Intracellular Accumulation

Abstract Objective This study was to compare the reversal effect of 5-bromotetrandrine (BrTet) with Tetrandrine (Tet) when combined with ADM on multidrug resistance cell line K562/A02 and to investigate the reversal mechanism of this new derivative. Methods The protein levels of P-glycoprotein (P-gp) were detected by fluorospectrophotometry and Western blot. The mRNA levels of P-gp were determined by RT-PCR. The in vivo effect of Tet was investigated using nude mice grafted with sensitive human leukemia cell line K562 and MDR cell line K562/A02. Results Flow cytometry assay showed that 1.0 μMol/L BrTet significantly increased the apoptosis percentage. BrTet also enhanced the intracellular accumulation of ADM in K562/A02 cells and its potency was greater than that of Tet at the same concentrations. BrTet inhibited the overexpression of P-gp and down regulated MDR1 mRNA expression in K562/A02 cells in a dose-dependent manner. In nude mice bearing K562 xenografts on the left flank and K562/A02 xenografts on the right flank, i.p. injection of 10 mg/kg BrTet significantly enhanced the antitumor activity of ADM against K562/A02 xenografts with inhibitory rates of 26.1%, while ADM alone inhibited the growth of KBv200 xenografts by only 5.8%. Conclusion BrTet showed significant MDR reversal activity in vitro and in vivo. Its activity may be related to the inhibition of P-gp overexpression and the increase in intracellular accumulation of anticancer drugs, which lead to more K562/A02 cells apoptosis.

CBX8, a Polycomb-Group Protein, Is Essential for MLL-AF9-Induced Leukemogenesis

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4174-4174
Author(s):  
Jiaying Tan ◽  
Jay L. Hess
Keyword(s):  
Gene Expression ◽  
Cell Growth ◽  
Cell Lines ◽  
Transcriptional Activation ◽  
Fusion Proteins ◽  
Conflicts Of Interest ◽  
Leukemia Cell ◽  
Polycomb Group ◽  
Human Leukemia ◽  
Interaction Sites

Abstract Abstract 4174 Trithorax and Polycomb-group (Trx-G and Pc-G) proteins are antagonistic regulators of homeobox-containing (Hox) gene expression that play a major role in regulation of hematopoiesis and leukemogenesis. Mixed lineage leukemia (MLL), a mammalian Trx-G protein, is a histone methyltransferase crucial for embryonic development and hematopoiesis that is commonly altered by translocation in acute leukemia. Recent evidence suggests that transformation by MLL fusion proteins is dependent on multiple interaction complexes, including the polymerase associated factor complex (PAFc) and the elongation activating protein complex (EAPc) or a closely related AF4 family/ENL family/P-TEFb complex (AEPc). CBX8 is a human PcG protein, functioning as a transcription repressor in the polycomb repressive complex 1 (PRC1). Previous studies have shown that CBX8 also interacts with the EAPc components AF9 and ENL; however, its role in leukemogenesis is unknown. To elucidate the significance of this interaction between these two proteins thought to have antagonistic function, we generated a large series of point mutations in AF9 and identified two amino acids that are essential for CBX8 interaction but preserve the interaction with other EAP components. Mutation of the two sites reduced the transcriptional activation of the MLL-AF9 target promoters by nearly 50% and completely inhibits the ability of MLL-AF9 to immortalize bone marrow (BM) as assessed by methylcellulose replating assays. This finding suggests that CBX8 interaction is essential for MLL-AF9-induced leukemogenesis. Several lines of evidence further support this finding. First, CBX8 knockdown by siRNAs decreased MLL-AF9-induced transcriptional activation by approximately 50%. Second, the ability of MLL-AF9 to transform primary BM was markedly reduced by retroviral shCbx8 transduction. Notably, this inhibitory effect is specific for MLL-AF9 because the BM transformation ability of E2A-HLF was unaffected by Cbx8 suppression. Third, Cbx8 suppression by shCbx8 in MLL-AF9 and MLL-ENL, but not E2A-HLF transformed AML cell lines, significantly inhibited the expression of MLL-dependent target genes, as well as cell growth and colony forming ability. Fourth, inducing CBX8 knockdown in human leukemia cell lines expressing MLL-AF9 led to a marked decrease in the localization of basic transcription machinery at the Hoxa9 locus and a corresponding reduction in Hoxa9 transcription. Importantly, the observed effects of CBX8 on MLL-rearranged leukemia cells are PRC1-independent: no effects on MLL target gene expression, cell growth, or BM transformation ability were observed by suppressing other core components of PRC1. Taken together, our results indicate that CBX8, independent of its transcription repression role in PRC1, interacts with and synergizes with MLL fusion proteins to promote leukemogenesis. Defining the interaction sites between AF9/ENL and CBX8 and the dependence of other AML subtypes and normal hematopoiesis on CBX8 will be important for the further development of agents that target this mechanism in MLL-rearranged and potentially other AML subtypes. Disclosures: No relevant conflicts of interest to declare.

Quantitative Phosphoproteomics Identified a New Syk-Lyn-Axl Signalling Pathway Involved In Resistance to Nilotinib In Chronic Myeloid Leukemia Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3376-3376
Author(s):  
Romain Gioia ◽  
Cedric Leroy ◽  
Claire Drullion ◽  
Valérie Lagarde ◽  
Serge Roche ◽  
...  
Keyword(s):  
Chronic Myeloid Leukemia ◽  
Tyrosine Kinase ◽  
Myeloid Leukemia ◽  
Conflicts Of Interest ◽  
Critical Role ◽  
Dependent Manner ◽  
Stable Isotope Labelling ◽  
Resistant Cells

Abstract Abstract 3376 Nilotinib has been developed to overcome resistance to imatinib, the first line treatment of chronic myeloid leukemia (CML). To anticipate resistance to nilotinib, we generate nilotinib resistant CML cell lines in vitro to characterize mechanisms and signaling pathways that may contribute to resistance. Among the different mechanisms of resistance identified, the overexpression of the Src-kinase Lyn was involved in resistance both in vitro, in a K562 cell line (K562-rn), and in vivo, in nilotinib-resistant CML patients. To characterize how Lyn mediates resistance, we performed a phosphoproteomic study using SILAC (Stable Isotope Labelling with Amino acid in Cell culture). Quantification and identification of phosphotyrosine proteins in the nilotinib resistant cells point out two tyrosine kinases, the spleen tyrosine kinase Syk and the UFO receptor Axl. The two tyrosine kinase Syk and Axl interact with Lyn as seen by coimmunopreciptation. Syk is phosphorylated on tyrosine 323 and 525/526 in Lyn dependent manner in nilotinib resistant cells. The inhibition of Syk tyrosine kinase by R406 or BAY31-6606 restores sensitivity to nilotinib in K562-rn cells. In parallel, the inhibition of Syk expression by ShRNA in K562-rn cells abolishes Lyn and Axl phosphorylation and then interaction between Lyn and Axl leading to a full restoration of nilotinib efficacy. In the opposite, the coexpression of Lyn and Syk in nilotinib sensitive K562 cells induced resistance to nilotinib whereas a Syk kinase dead mutant did not. These results highlight for the first time the critical role of Syk in resistance to tyrosine kinase inhibitors in CML disease emphasizing the therapeutic targeting of this tyrosine kinase. Moreover, Axl, which is already a target in solid tumor, will be also an interesting pathway to target in CML. Disclosures: No relevant conflicts of interest to declare.

Effect of Hepcidin on Hypoxia-Induced Erythropoietin Production

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3219-3219
Author(s):  
Gail A Dallalio ◽  
Robert T. Means
Keyword(s):  
Hepg2 Cells ◽  
Conflicts Of Interest ◽  
Iron Concentration ◽  
Chronically Ill ◽  
Dependent Manner ◽  
Red Cell ◽  
Trypan Blue Exclusion ◽  
Anemia Of Chronic Disease ◽  
Iron Stores

Abstract Abstract 3219 The anemia of chronic disease (ACD) is the major etiology of the anemia observed in in chronically ill patients. ACD typically manifests itself as a hypoproliferative anemia accompanied by a low serum iron concentration despite adequate reticuloendothelial iron stores. In ACD, a slight shortening of red cell survival creates a demand for a small increase in red cell production by the bone marrow. The marrow cannot respond adequately to this demand due to impaired erythropoiesis and impaired mobilization of reticuloendothelial system iron stores. Increased production of the iron regulatory peptide hepcidin has been proposed as the primary factor resulting in ACD. Hepcidin has also been reported to decrease erythroid colony formation in vitro under conditions of restrictive Epo concentration. A blunted erythropoietin (Epo) response to anemia is a characteristic feature of ACD. If hepcidin is the major factor responsible for ACD, then it should also contribute to the impaired Epo production observed in this syndrome. The effect of hepcidin on hypoxia-induced Epo production was evaluated in HepG2 cells exposed to 5% oxygen for 24 hr. 24 hr exposure to hepcidin during hypoxia at the concentrations studied (up to 100 ng/mL) had no adverse effect on HepG2 cell viability compared to controls as evaluated by cell number and Trypan blue exclusion or on cellular synthetic function as measured by alpha fetoprotein. Epo production (whether measured by Western blot or by ELISA) was increased by hypoxia; however, this increase was blunted by the addition of hepcidin to the incubation medium. Impairment of hypoxia-induced Epo production by hepcidin showed a dose-response relationship. The addition of iron-replete transferrin to the incubation mixture did not significantly alter hepcidin effects, suggesting that these effects do not primarily reflect changes in iron availability. In order to evaluate mechanisms by which hepcidin might decrease Epo production, effects of hepcidin 0–100 ng/mL on hypoxia-inducible factor (HIF)-1α protein expression were evaluated in HepG2 cells (HIF expression was normalized to actin expression). The increment in HIF-1α caused by hypoxia was decreased by hepcidin in a dose-dependent manner. The ratio of Epo to HIF was not altered by hepcidin, suggesting that hepcidin effects on HIF may be the mechanism of its effects on Epo production. In conclusion, hepcidin appears to blunt the increment in Epo production induced by hypoxia in vitro. This mechanism does not appear to be reversible by exposure to increased quantities of transferrin-bound iron. This finding is consistent with a role for hepcidin in the impaired Epo production of ACD independent of its effects on iron flux. Disclosures: No relevant conflicts of interest to declare.

Oral Supplementation with Omega3 Fatty Acids Inhibits NFkB Activation In Chronic Lymphocytic Leukemia (CLL) Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4607-4607
Author(s):  
Oscar F. F Ballester ◽  
Johannes Fahrmann ◽  
Theodore Witte ◽  
Gabriela Ballester ◽  
W. Elaine Hardman
Keyword(s):  
Conflicts Of Interest ◽  
Early Stage ◽  
Gradient Centrifugation ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Dependent Manner ◽  
Red Cell ◽  
Omega 3 ◽  
Dose Dependent

Abstract Abstract 4607 Introduction: Nuclear factor kappa B (NFkB) is a critical transcription factor involved in the growth and survival of CLL cells. NFkB is recognized as an important target for the development of novel therapies for the treatment of various malignancies. In vitro and in experimental animal models, OMEGA-3 fatty acid (O3FA) supplementation has been shown to inhibit NFkB activity. Patients and Methods: Patients with early stage CLL (Rai stages 0-II) who required no therapy, where accrued to this phase I-II trial. O3FA supplements were given for a total of 12 months at doses ranging from 2250 mg (EPA plus DHA), escalated to 4500 mg and 6750 mg per day as tolerated. NFkB activity was measured in peripheral blood samples after separation of mononuclear cell by gradient centrifugation and expressed as luminescence units/μ g of protein. Baseline and multiple serial samples were obtained during the study period. In-vitro cytotoxicity assays to doxorubicin were conducted using standard LD50 methods. Compliance was monitored by analysis of red cell and lymphocyte membrane lipid composition by gas chromatography. Results: Fifteen patients have been accrued to the trial, 8 of them have currently completed the planned 12 months of the study period. No significant clinical changes in disease activity were noted. O3FA was well tolerated. Supplementation resulted in a dose-dependent increase of O3FA composition of red cell and lymphocyte membranes in a dose dependent manner. At baseline, CLL patients had NFkB above the range observed in normal controls (2.05 × 104 to 2.32 × 105 NFkB lum units/μ g). The median value in CLL patients at baseline was 11.60 × 106 NFkB lum units/μ g (range 0.9 × 105 to 23.12 × 106). Among 5 patients with the highest baseline levels of NFkB, a decrease in NFkB activity ranging from 0.02 to 0.19 of the baseline value, was noted at the 2 higher doses of O3FA supplementation. Similar results were seen in patients with relatively lower levels of baseline NFkB activity (0.9 × 105 to 2.96 × 106 lum units/μ g). In vitro, significant doxorubicin cytotoxicity (>50%) was noted in samples obtained during supplementation, at μ gM concentrations which produced no detectable cell kill in baseline samples. Conclusions: O3FA supplementation resulted in significant inhibition of NFkB activity in leukemic cells from patients with CLL. In-vitro, after O3FA supplementation CLL cells became more sensitive to doxorubicin. Preliminary analysis of whole genome micro arrays revealed significant down-regulation of multiple genes associated with O3FA supplementation. Disclosures: No relevant conflicts of interest to declare.

The bHLH Transcription Factors SCL and LYL1 Awaken Hematopoietic Stem Cells by Repression of p21

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 214-214
Author(s):  
David J. Curtis ◽  
Nhu-Y Nguyen ◽  
Jessica Salmon
Keyword(s):  
Cell Cycle ◽  
Transcription Factors ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Short Term ◽  
Hematopoietic Stem ◽  
Bhlh Factors ◽  
Mild Defect ◽  
Bhlh Transcription Factors

Abstract Abstract 214 The basic helix-loop-helix (bHLH) transcription factors SCL (TAL1) and LYL1 are regulators of adult hematopoietic stem cell (HSC) activity with significant functional redundancy: HSCs lacking SCL (SCLδ/δ) have a mild defect in short-term repopulating activity whilst HSCs lacking LYL1 (LYL1−/−) have normal repopulating activity. In contrast, we have shown previously that HSCs lacking both SCL and LYL1 (DKO) are unable to grow in vitro and have no in vivo repopulating activity. Phenotypic and expression analyses of SCLδ/δ, LYL1−/− and DKO mice were performed to determine how bHLH factors regulate HSC activity. Consistent with the short-term repopulating defects of SCLδ/δ HSC, Lineage negative Sca-1+ c-Kit+ (LSK) bone marrow cells from SCLδ/δ mice had reduced in vitro replating activity associated with increased quiescence – 90% in G0 compared with 70% in normal LSK. Increased quiescence was associated with delayed hematopoietic recovery following treatment of mice with 5-Fluorouracil. Consistent with the increased quiescence, expression of the cell cycle inhibitor, Cdkn1a (p21) was increased three-fold in SCLδ/δ and LYL1−/− LSK. Moreover, p21 levels in LSK isolated from DKO mice were increased 50-fold. To determine the functional relevance of the elevated levels of p21 in DKO HSCs, we generated DKO mice on a p21-deficient (p21−/−) background. Remarkably, loss of p21 rescued in vitro cell growth of DKO progenitors. More importantly, primary and secondary competitive repopulation assays demonstrated multi-lineage repopulating activity of p21−/− DKO HSCs. These results suggest the bHLH factors SCL and LYL1 function as repressors of p21, allowing HSCs to enter cell cycle during stress hematopoiesis. Disclosures: No relevant conflicts of interest to declare.

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