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  • American Society of Hematology  (14)
  • 1
    In: Blood, American Society of Hematology, Vol. 104, No. 11 ( 2004-11-16), p. 1977-1977
    Abstract: AMN107 (Novartis Pharmaceuticals, Basel, Switzerland) is a potent aminopyrimidine tyrosine kinase (TK) inhibitor, which is active at nanomolar concentrations against c-Kit, PDGFR as well as the wild type Bcr-Abl and common variety of mutant Bcr-Abl (e.g., M351T, F317L and E255V) TK. In a previous report, we demonstrated that treatment with the hydroxamic acid analogue histone deacetylase inhibitor LBH589 (Novartis) (20 to 100 nM) induces hsp90 acetylation and promotes polyubiquitylation and proteasomal degradation of Bcr-Abl, which is associated with apoptosis of the cultured Bcr-Abl expressing human chronic myeloid leukemia-blast crisis (CML-BC) K562 and LAMA-84 cells, as well as of primary CML-BC cells. In the present studies, we determined the cell cycle and apoptotic effects of AMN107 and/or LBH589 in K562, LAMA-84 and primary CML-BC cells. Treatment with AMN107 (20 to 100 nM) induced cell cycle G1 phase accumulation and apoptosis, exerting 10 to 20 fold more potent effect than imatinib mesylate (IM) in K562 and LAMA-84 cells. This was associated with marked induction of p27, inhibition of Bcr-Abl TK activity, as well as attenuation of the levels of p-STAT5, p-AKT, Bcl-xL, and c-Myc levels in a dose dependent manner. Co-treatment with LBH589 (50 nM) and AMN107 (100 nM) induced more G1 phase accumulation than either agent alone. The combination of AMN107 and LBH589 also exerted synergistic apoptotic effects in K562 cells, as determined by the median effect isobologram analysis. This was associated with more attenuation of the levels of pro-growth and pro-survival proteins, e.g., p-STAT5, p-ERK1/2, c-Myc and Bcl-xL, as well as greater induction of the levels of pro-death p27 and Bim proteins. Treatment of human AML HL-60 cells containing ectopic expression of the IM-refractory, mutant Bcr-AblT315I with LBH589 (50 nM for 24 hours) attenuated the mutant Bcr-Abl levels and induced apoptosis of HL-60/Bcr-AblT315I cells. Treatment with AMN107 (up to 2.0 μM) alone was ineffective in inducing loss of viability of HL-60/Bcr-AblT315I cells, and co-treatment with LBH589 (50 nM) and AMN107 did not induce more loss of cell viability of HL-60/Bcr-AblT315I cells than treatment with LBH589 alone. AMN107 levels ≥ 200 nM significantly inhibited survival of HL-60/Bcr-AblE255K and HL-60/Bcr-AblM351T cells. Consistent with this, the combined treatment with LBH589 and AMN107 also induced more loss of viability than treatment with either agent alone in 4 samples of IM-refractory primary CML-BC cells. These studies demonstrate that both AMN107 and LBH589 are active against IM-resistant CML-BC and the combination of the two exerts superior activity against IM-sensitive and IM-resistant, wild type and mutant Bcr-Abl expressing cultured and primary CML cells.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2004
    detail.hit.zdb_id: 1468538-3
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  • 2
    In: Blood, American Society of Hematology, Vol. 105, No. 3 ( 2005-02-01), p. 1246-1255
    Abstract: Bcr-Abl–expressing primary or cultured leukemia cells display high levels of the antiapoptotic heat shock protein (hsp) 70 and are resistant to cytarabine (Ara-C), etoposide, or Apo-2L/TRAIL (TNF-related apoptosis-inducing ligand)–induced apoptosis. Conversely, a stable expression of the cDNA of hsp70 in the reverse orientation attenuated not only hsp70 but also signal transducers and activators of transcription 5 (STAT5) and Bcl-xL levels. This increased apoptosis induced by cytarabine, etoposide, or Apo-2L/TRAIL. Ectopic expression of hsp70 in HL-60 cells (HL-60/hsp70) inhibited Ara-C and etoposide-induced Bax conformation change and translocation to the mitochondria; attenuated the accumulation of cytochrome c, Smac, and Omi/HtrA2 in the cytosol; and inhibited the processing and activity of caspase-9 and caspase-3. Hsp70 was bound to death receptors 4 and 5 (DR4 and DR5) and inhibited Apo-2L/TRAIL-induced assembly and activity of the death-inducing signaling complex (DISC). HL-60/hsp70 cells exhibited increased levels and DNA binding activity of STAT5, which was associated with high levels of Pim-2 and Bcl-xL and resistance to apoptosis. Expression of the dominant negative (DN) STAT5 resensitized HL-60/hsp70 cells to cytarabine, etoposide, and Apo-2L/TRAIL–induced apoptosis. Collectively, these findings suggest that hsp70 inhibits apoptosis upstream and downstream of the mitochondria and is a promising therapeutic target for reversing drug-resistance in chronic myeloid leukemia-blast crisis and acute myeloid leukemia cells. (Blood. 2005;105:1246-1255)
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2005
    detail.hit.zdb_id: 1468538-3
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  • 3
    In: Blood, American Society of Hematology, Vol. 120, No. 7 ( 2012-08-16), p. 1458-1465
    Abstract: STAT3 plays a crucial role in promoting progression of human cancers, including several types of B-cell lymphoma. However, as a transcription factor lacking its own enzymatic activity, STAT3 remains difficult to target with small-molecule drugs in the clinic. Here we demonstrate that persistent activated STAT3 colocalizes with elevated expression of S1PR1, a G-protein–coupled receptor for sphingosine-1-phosphate (S1P), in the tumor cells of the activated B cell–like subtype of diffuse large B-cell lymphoma patient specimens. Inhibition of S1PR1 expression by shRNA in the lymphoma cells validates that blocking S1PR1 affects expression of STAT3 downstream genes critically involved in tumor cell survival, proliferation, tumor invasion, and/or immunosuppression. Using S1PR1 shRNA, or FTY720, an antagonist of S1P that is in the clinic for other indications, we show that inhibiting S1PR1 expression down-regulates STAT3 activity and causes growth inhibition of the lymphoma tumor cells in vitro and in vivo. Our results suggest that targeting S1P/S1PR1 using a clinically relevant and available drug or other approaches is potentially an effective new therapeutic modality for treating the activated B cell–like subtype of diffuse large B-cell lymphoma, a subset of lymphoma that is less responsive to current available therapies.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2012
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  • 4
    In: Blood, American Society of Hematology, Vol. 114, No. 22 ( 2009-11-20), p. 3083-3083
    Abstract: Abstract 3083 Poster Board III-20 Histone Deacetylase Inhibitors (HDACi) such as LBH589, which inhibit the zinc containing catalytic domain of HDAC of classes I, II, and IV, demonstrate activity against various malignancies, particularly lymphoid malignancies. SIRT1 is an NAD+ dependent class III histone deacetylase, which deacetylates histones as well as non-histone proteins and is not affected directly by HDACi such as LBH589. It remains controversial whether inhibition of SIRT1 or its activation is more efficacious in anticancer therapy. We have studied the activity of two novel SIRT1 activators, SRT501 and SRT2183, in Philadelphia chromosome negative acute lymphoblastic leukemia (ALL) cell lines. Both pre B (NALM-6, Reh) and T cell (MOLT-4) ALL lines were treated with either SRT501 or SRT2183, as well as in combination with LBH589 and evaluated for biological and gene expression responses. SRT501 induced growth arrest and apoptosis at doses ranging from 10-100 uM, with even the lowest doses inhibiting growth at 72 hours. SRT2183 is much more potent, with growth arrest and apoptosis induced at doses ranging from 1-20 uM. PCR array analysis revealed that SRT2183 treatment leads to increased mRNA levels of pro-apoptosis, growth arrest, and DNA damage response genes. We have previously demonstrated that the activity of LBH589 is mediated in part through upregulation or acetylation of proteins involved in the DNA damage response pathways. Quantitative real-time PCR confirms that the combination of LBH589 with SRT2183 leads to significantly higher expression of GADD45A and GADD45G than either agent alone. The combination of LBH589 plus SRT2183 showed enhanced inhibition of c-Myc protein levels, phosphorylation of H2A.X, and interestingly, increased acetylation of p53 (acetylation of p53 was not seen with SRT2183 alone). In summary, the novel SIRT1 activators SRT501 and SRT2183 show growth inhibitory and pro-apoptotic activity in Ph- ALL alone and enhanced activity in combination with LBH589. Clinical studies of these agents, particularly in combination with HDACi are warranted. Disclosures Kirschbaum: Novartis: Consultancy. Cermak:Sirtris: Employment. Atadja:Novartis: Employment.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2009
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  • 5
    In: Blood, American Society of Hematology, Vol. 122, No. 21 ( 2013-11-15), p. 2512-2512
    Abstract: Mantle cell lymphoma (MCL) is rarely curable and therapy resistance often leaves few viable treatment options for patients. Previous studies have identified the importance of cyclin D1 (CCND1) translocation and overexpression in MCL pathogenesis, which leads to increased cyclin-dependent kinase 4 (CDK4) activity and accelerated cell cycle progression. However, targeting this abnormal cell cycle control, mainly through CDK4 inhibition causes only G1-phase growth arrest without significant cell death (Marzec et al. 2006). In contrast, prolonged inhibition of CCND1 with RNA interference induces apoptosis in MCL cell lines (Weinstein et al. 2012), suggesting an essential function of CCND1 independent of CDK4 activity. The mechanism of this non-catalytic role of CCND1 in maintaining MCL cell survival is largely unknown. To clarify the cell cycle role of CCND1 in addition to its CDK4-dependent function, we compared the effects of CCND1 and CDK4 silencing on MCL cell survival. MCL cell lines co-expressing GFP and doxycycline-inducible shRNA targeting CCND1 or CDK4 were generated. Cells with similar GFP expression levels were FACS sorted to normalize for shRNA expression. Both CCND1 and CDK4 silencing resulted in G1-phase arrest, but only CCND1-silenced cells demonstrated a marked increase in apoptosis. Investigation of the potential cause of apoptosis revealed significant accumulation of DNA double-strand breaks following CCND1 ablation, as measured by nuclear gamma-H2AX focus formation. Interestingly, CCND1-silenced cells exhibited a significant increase in 53BP1+ nuclear bodies in G1-phase, reminiscent of 53BP1 foci observed by Lukas and colleagues in cells undergoing aphidicolin-induced replication stress (Lukas et al. 2011). Analysis of replication fork movement in CCND1-depleted cells showed substantially reduced fork speed and increased frequency of origin firing, both of which are indicative of replication stress. In contrast, knockdown of CDK4 did not result in slower forks or increase in the frequency of origin firing. Genomic instability associated with replication stress was also apparent in CCND1-silenced cells, including increased micronucleus formation and recurrent chromatid gaps or breaks detected by cytokinesis-block assay and karyotyping, respectively. Analysis of DNA replicative and damage checkpoints revealed that both ATR-CHEK1 and ATM-CHEK2 pathways were activated by phosphorylation following CCND1 silencing in MCL cell lines, a xenograft animal model, and primary tumor samples, but not in non-MCL tumors. Interestingly, this activation (with the exception of ATM phosphorylation) was unsustainable over time and did not cause down-regulation of the downstream targets CDC25 and CDK1/2 but, instead, we observed an increase in CDC25A/B protein levels and CDK1/2 activity, indicating defective cell cycle checkpoints. Exposing CCND1-silenced cells to replication stress-inducing or DNA-damaging agents such hydroxyurea, aphidicolin, etoposide or ionizing radiation further amplified the checkpoint defects seen in unperturbed cells. We did not observe any significant difference in this checkpoint signaling in control and CDK4 knockdown cells under these conditions. Furthermore, CCND1-deficient cells were more sensitive to pharmacological inhibition of ATR and CHEK1 but not ATM, confirming a constitutive role of CCND1 in the ATR-CHEK1 pathway. In conclusion, these studies revealed an unexpected CDK4-independent role of CCND1 in maintaining DNA replicative checkpoints to prevent replication stress and genome instability in MCL cells. As most cancer treatments rely on agents that create DNA replication stress, targeting this function of CCND1 could provide a rational approach to overcome resistance to conventional therapies in MCL. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2013
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  • 6
    In: Blood, American Society of Hematology, Vol. 126, No. 23 ( 2015-12-03), p. 2731-2731
    Abstract: Background MLN8237 is an oral inhibitor of aurora kinase A (AURKA) that causes mitotic spindle defects, mitotic delay, and apoptosis in lymphoma cell lines and mouse models. Human studies have shown promising responses in hematologic malignancies. Vorinostat is an oral HDAC inhibitor that is FDA-approved for cutaneous T-cell lymphoma, and is under study in other lymphomas. AURKA inhibitors in combination with vorinostat show synergistic pro-apoptotic effects in vitro in Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) cell lines (Kretzner 2011, Cancer Res 71:3912). Our phase I multicenter study assessed the safety and tolerability of MLN8237 combined with vorinostat in patients with lymphoid malignancies [NCT01567709] and determined the maximum tolerated dose (MTD) to be 20 mg twice daily (BID) of MLN8237 and 200 mg BID of vorinostat orally in an interrupted dosing schedule (Schedule II). We have recently completed accrual to an expanded cohort at MTD and report preliminary data on our secondary endpoints among patients treated on Schedule II of this study. Methods Eligible patients were ≥18 years old with relapsed or refractory (r/r) lymphoid malignancies (HL, B-NHL, T-NHL), measureable disease, ECOG performance status 0-2, neutrophils ≥1500/µL, platelets ≥100,000/µL, and adequate kidney and liver function. Secondary endpoints were toxicities, clinical response, pharmacokinetic (PK) analysis, and correlative studies. A 3+2 modified rolling-6 design was employed to determine the MTD. Enrollment was initiated on a continuous dosing schedule (Schedule I) that was poorly tolerated, with adverse events (AEs) on dose levels 1 and 2 leading to many dose delays primarily due to gastrointestinal intolerance and myelosuppression. The protocol was amended to the interrupted dosing Schedule II: MLN8237 escalated from 20 to 50 mg BID on days 1-3 and 8-10, and vorinostat given at 200 mg BID on days 1-5 and 8-12 of a 21-day cycle. Results We treated 25 patients (11 DLBCL, 7 HL, 3 FL, 2 MCL, 1 PTCL, 1 NK/T cell) on the interrupted dosing Schedule II. Median age was 59 years (range 26-78). Mediannumber of prior therapies was 4 (range 1-10); 9 patients (36%) underwent prior stem cell transplantation. See Table for treatment summary. MTD of the combination is 20 mg BID for MLN8237 and 200 mg BID for vorinostat on the interrupted schedule. The commonest ( 〉 5%) ≥ grade 3 drug-related AEs were neutropenia (52%), thrombocytopenia (44%), leukopenia (44%), anemia (28%), lymphopenia (24%), febrile neutropenia (12%), oral mucositis (8%), diarrhea (8%), and lung infection (8%). There were no study-related deaths. 4 patients stopped treatment due to AEs and 13 due to progressive disease (PD). 2 patients achieved complete remission (CR); both had DLBCL, and both halted therapy after completing 2 further cycles of treatment post-CR. They both remain in CR (18 months and 1 month at data lock). 1 patient had a partial response (PR), and 8 patients maintained stable disease (SD). PKs demonstrated a clearance of 230 L/h (sd=495) and 2.94 L/h (sd=1.57) for vorinostat and MLN8237, respectively. Archived baseline biopsies are being analyzed to determine AURKA expression. Six fresh paired tumor biopsies were obtained before and on-treatment in the expanded cohort at MTD for correlative studies. Conclusions MLN8237 when given in combination with vorinostat is safe and tolerable in an interrupted dosing schedule among heavily pre-treated patients with r/r lymphoid malignancies. The MTD for MLN8237 is 20 mg BID on days 1-3 and 8-10, combined with vorinostat at 200 mg BID on days 1-5 and 8-12, of 21 day cycles. The commonest AEs were hematologic and gastrointestinal. Promising responses were seen in several patients, especially those with DLBCL, which support phase 2 exploration of this therapy in patients with intermediate-high grade NHL. PK analysis suggests that combination therapy exposures are similar to single agent exposure. Correlative studies done in a 12-patient expanded cohort will be presented. [Trial supported in part by UM1CA186717] Table 1. Schedule II:MLN8237 (mg)/ Vorinostat (mg) # of patients treated # of cycles completed Median (range) # of dose limiting toxicities (DLT) DLT Description Best response Dose level 1 (30/200) 7 3 (0-18) 2 1 pt had grade 3 febrile neutropenia; 1 pt had grade 3 thrombocytopenia requiring transfusion 1 CR, 3 SD, 2 PD, 1 N/A Dose level -1 (20/200) 18 2 (0-14) 0 1 CR, 1 PR, 5 SD, 8 PD, 3 too early to assess Disclosures Siddiqi: Kite pharma: Other: attended advisory board meeting; Seattle Genetics: Speakers Bureau; Pharmacyclics/Jannsen: Speakers Bureau. Off Label Use: Vorinostat is only FDA-approved for CTCL but in this study it is being used in conjunction with MLN8237 (not FDA-approved) for all lymphomas.. Beumer:Millenium: Other: Research support. Forman:Mustang Therapeutics: Research Funding.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2015
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  • 7
    In: Blood, American Society of Hematology, Vol. 110, No. 11 ( 2007-11-16), p. 2796-2796
    Abstract: We investigated the mechanism of action of LBH589, a novel broad-spectrum HDAC inhibitor belonging to the hydroxamate class, in Philadelphia chromosome-negative (Ph−) acute lymphoblastic leukemia (ALL). Two model human Ph− ALL cell lines (T-cell MOLT-4, and non-T non-B cell Reh) were treated with LBH589 and evaluated for biological and gene expression responses. Low nM concentrations (IC50 5–20 nM) of LBH589 induced cell cycle arrest, apoptosis and histone (H3 and H4) hyperacetylation. PCR array analysis revealed that LBH589 treatment increased mRNA levels of pro-apoptosis, growth arrest and DNA damage repair genes. Quantitative real-time PCR confirmed that LBH589 induces expression of FANCG, FOXO3A, GADD45A, GADD45B and GADD45G. The most dramatically expressed gene (up to 45-fold induction) observed after treatment with LBH589 is GADD45G. Chromatin immunoprecipitation (ChIP) assays demonstrated increased histone acetylation at the GADD45G promoter following LBH589 treatment. Finally, treatment with LBH589 was active against cultured primary Ph− ALL cells, including those from a relapsed patient, inducing loss of cell viability (up to 70%). Thus, LBH589 possesses potent growth inhibitory activity against Ph− ALL cells associated with upregulation of genes critical for DNA repair. These findings provide a rationale for exploring the clinical activity of LBH589 in the treatment of patients with Ph− ALL.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2007
    detail.hit.zdb_id: 1468538-3
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  • 8
    In: Blood, American Society of Hematology, Vol. 114, No. 22 ( 2009-11-20), p. 1690-1690
    Abstract: Abstract 1690 Poster Board I-716 Background Patients with relapsed or refractory Hodgkin (HL) and Non Hodgkin Lymphoma (NHL) have few options after salvage therapy and transplant, and new agents are thus needed. MK-5108 is a novel aurora kinase inhibitor (AKI) with specificity against aurora kinase A, that produces G2/M phase cell cycle arrest. We show that addition of vorinostat, a histone and protein deacetylase inhibitor, to AKI treatment results in reactivation of proapoptotic genes and enhanced lymphoma cell death. A panel of HL and NHL cell lines was studied with either drug or the combination, using cell growth, apoptosis, and flow cytometry assays, followed by molecular studies. Results MK-5108 alone at 0.1 – 3 mM results in significant growth inhibition and apoptosis in multiple cell lines representing Hodgkin, Burkitt, and Non-Hodgkin lymphoma types, interestingly,DHL-4 and DHL-6 cells were more sensitive to this agent than to the pan-AKI MK-0457. Vorinostat alone at a dose range of 0.5 – 3 mM reduces cell growth by 50% or more in all lines tested. The combination of 1.5 mM vorinostat and 100 nM MK-5108 results in over 85% apoptosis of multiple lymphoma lines tested at 72 hours. Cell cycle analyses by FACS of MK-5108 treated cells show an increased percentage of cells in G2/M with few cells in sub-G1, whereas in combination with vorinostat the G2/M peak decreases and there is a significant increase in the apoptotic sub-G1 population. Real-time PCR analysis and immunoblotting of L540 cells treated with either single agent or in combination revealed that vorinostat treatment leads to alteration in pro-apoptosis, growth arrest, and DNA damage response genes. Myc mRNA and protein levels are reduced by vorinostat, and repression of microRNAs (miRNAs) in the Myc-regulated polycistronic cluster of miRNAs of chromosome 13, such as miR-17.5p, -17.3p, and 18, occurs with vorinostat and TSA. Prosurvival genes such as bcl-XL and hTERT are downregulated five-fold by vorinostat treatment, while the proapoptotic BAK gene is upregulated 1.5 – 2-fold. Vorinostat treatment leads to enhanced acetylation of p53, with a corresponding increase in the p53 target genes p21 and Noxa. To analyze the role of Myc inhibition in the sensitization by vorinostat of lymphoma cells to MK-5108, siRNA-mediated knock-down of Myc expression in L540 cells was performed. The siRNA-Myc transfected L540 cells showed enhanced sensitivity to MK-5108 as compared to control siRNA-null cells, as well as decreased hTERT levels, confirming the role of Myc inhibition by vorinostat as an integral part of the sensitization of lymphoma cells to MK-5108. Conclusions The HDACi vorinostat leads to both transcriptional and post-transcriptional changes that create a pro-apoptotic milieu, sensitizing the cell to centrosome-acting agents such as the aurora kinase A inhibitor MK-5108. These preclinical data support clinical trials of MK-5108 plus vorinostat in patients with relapsed or refractory lymphomas. [We acknowledge Merck Inc for providing Vorinostat, MK-0457, MK-5108, and research support.] Disclosures Kretzner: Merck: Research Funding. Yen:Merck: Research Funding. Kirschbaum:Merck: Research Funding, Speakers Bureau.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2009
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  • 9
    In: Blood, American Society of Hematology, Vol. 124, No. 21 ( 2014-12-06), p. 5197-5197
    Abstract: Mantle cell lymphoma (MCL) is a heterogeneous disease, ranging from indolent to aggressive conditions. Prognostic markers that predict aggressive MCL include blastoid cytologic features, high proliferation index (Argatoff et al. 1997), INK4A/ARF locus deletion (Dreyling et al. 1997), TP53 deletion and/or mutations (Greiner et al. 1996), elevated cyclin D1 (CCND1) expression (Rosenwald et al. 2003), and NOTCH1/2 mutations (Kridel et al. 2012, Bea et al. 2013). Among these, TP53 lesions are the most recurrent, suggesting their important role in MCL pathogenesis. In response to DNA damage, TP53 in normal cells activates cell cycle checkpoints to stall DNA replication allowing time for DNA repair or induces apoptosis when damage is severe (Zhou and Elledge. 2000). Tumor cells lacking TP53 function rely on the ATR-CHEK1 signaling for cell cycle checkpoints following DNA damage (Powell et al. 1995). Although both TP53 deficiencies and elevated CCND1 expression levels have been associated with poor survival, possible cooperation of TP53 status and CCND1 expression in aggressive MCL has not been examined. In this study, we hypothesize that CCND1 overexpression collaborates with TP53 deficiency to promote MCL survival and chemoresistance. We compared the effects of CCND1 knockdown on cell survival and resistance to hydroxyurea (HU) and cytarabine to that of knockdown or pharmacological inhibition of CDK4 in MCL lines differing in TP53 status. Inducible gene knockdown was generated in UPN-1 cells to investigate the role of CCND1 in preventing replication stress and DNA damage and in the maintenance of the ATR and CHEK1 signaling. In addition, knockdown of TP53 in TP53-proficient MCL cells was performed to determine the contribution of TP53 status to tumor response to HU and the requirement of CCND1 in the chemosensitivity of these cells. We demonstrate that the survival of TP53-deficient MCL lines (UPN-1 and JEKO-1) is more dependent on CCND1 than on CDK4, but neither of these proteins is essential in TP53-proficient lines (REC-1 and Z-138). Using inducible gene knockdown in UPN-1 cells, we show that CCND1 depletion-induced apoptosis is caused by endogenous replication stress and DNA damage, which are related to defects in the DNA replication checkpoints ATR and CHEK1. The protective effect of CCND1 in MCL cell lines was also confirmed in vivo tumor model. Silencing of CCND1, but not CDK4, sensitizes TP53-deficient MCL cells to hydroxyurea (HU) or cytarabine, which activates the S-phase checkpoint. In addition, forced expression of CCND1 rescues TP53-deficient cells from HU-induced apoptosis in an ATR-dependent manner. In contrast, neither silencing of CCND1 nor CDK4 increases the sensitivity of TP53-proficient cells to these agents. Finally, knockdown of TP53 sensitizes REC-1 cells (TP53 competent) to combination of HU exposure and CCND1 inhibition, confirming the role of TP53 status and CCND1 expression in the chemosensitivity of MCL cells. In summary, these results uncover a novel role for CCND1 in maintaining the ATR and CHEK1 signaling in TP53-deficient MCL. This role of CCND1 could contribute to its oncogenic potential and chemoresistance in aggressive MCL that lack TP53. Disclosures No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2014
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  • 10
    In: Blood, American Society of Hematology, Vol. 108, No. 11 ( 2006-11-01), p. 2165-2165
    Abstract: Chronic myelogenous leukemia (CML) is associated with the bcr-abl fusion gene product, a constitutively active non-receptor tyrosine kinase driving cell division. The potent bcr-abl kinase inhibitor, dasatinib, is now FDA approved for imatinib-refractory patients, being active in most cases other than those with the T315I mutation. However, accelerated phase CML is typified by further genetic changes, including the suppression of various DNA damage response and apoptosis related proteins (Radich, et al PNAS 2006). Thus a novel approach which may reverse these changes, might provide better treatment of accelerated phase CML. A new class of agents targeting epigenetic processes, the histone deacetylase inhibitors (HDACi), is believed to act upon chromatin allowing re-expression of tumor suppressor genes believed to be closed off to transcription by the tumor in its effort to grow in an uncontrolled manner. We reasoned that adding an HDACi to dasatinib treatment of CML cells could promote re-expression of genes responding to genetic instability in these cells. To test this hypothesis we tested dasatinib (D) and the HDACi Vorinistat (V, suberoylanilide hydroxamic acid, SAHA) alone and in combination, using K562 cells. Apoptosis was measured by Annexin V staining after 48 hours. Apoptosis results: 1uM Vorinostat: 10%; 2 uM V: 16%. Dasatinib 0.5 nM: 28%, 1 nM D: 44% In combination, 1uM V + 0.5 nM D: 41%, 1 uM V + 1nM D: 64%, 2 uM V + 0.5 nM D: 65%, 2 uM V + 1 nM D: 67%, suggesting significant increase in apoptosis for the combination over either single agent treatment alone. We therefore began surveying panels of DNA damage- and apoptosis-related genes by means of RT-PCR. Studying the combination of 2 uM V + 1 nM D, we found increased expression of several proteins, including GADD45G and FANCG, both DNA damage response proteins suppressed in the progression to accelerated phase CML. Other proapoptotic proteins were increased such as MAP2K6, SEMA4A, BIK, and TNF superfamily members 7 and 25. This data suggests that the changes associated with progression from chronic phase to accelerated and blast crisis CML may be epigenetic in nature, and that these changes may be reversed by the combination of vorinostat and dasatinib. A clinical trial of dasatanib and vorinostat in advanced phase CML would be of value.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2006
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