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  • 1
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    Rituximab (R) Maintenance Versus Observation After Short Term Chemoimmunotherapy R-FND as First Line Treatment in Elderly Patients with Advanced Follicular Lymphoma (FL): Updated Results and Safety of the Maintenance of An Intergruppo Italiano Linfomi (IIL) Randomized Trial.
    American Society of Hematology ; 2009
    In:  Blood Vol. 114, No. 22 ( 2009-11-20), p. 1706-1706
    Details
    In: Blood, American Society of Hematology, Vol. 114, No. 22 ( 2009-11-20), p. 1706-1706
    Abstract: Abstract 1706 Poster Board I-732 Introduction in order to maintain efficacy and reduce toxicity of the treatment in elderly follicular lymphoma (FL) patients, we designed a study with a short chemo-immunotherapy R-FND with Rituximab consolidation followed by randomization between R maintenance or observation. Material and methods: From January 2004 to December 2007, 242 patients (age 60-75) with untreated advanced stage FL were enrolled by 33 IIL centres. Treatment plan was: 4 courses of R-FND (standard doses of Rituximab, Fludarabine, Mitoxantrone, Dexamethasone) every 28 days followed by 4 weekly Rituximab infusions as consolidation; responding (CR+CRu+PR) patients were randomized between Rituximab maintenance, one dose every 2 months for a total of 4 doses or observation. Qualitative and quantitative PCR monitoring for IgH/Bcl-2 rearrangement on bone marrow (BM) was performed at diagnosis, after R-FND and R consolidation and during maintenance/observation. Results 234 patients were eligible for the study: median age was 66 yrs; advanced stage II 14%, stage III 21% and stage IV 65%; BM involvement and B symptoms were documented in 55% and 18% respectively. FLIPI score was: Low 11%, Intermediate 34%, High 55%. One and 2 or more comorbidities were present in 36% and 23% of the patients respectively. Qualitative PCR analysis for IgH/Bcl-2 was performed in 223 patients at diagnosis and 51% were positive. Two hundred and two (86%) patients completed the induction treatment and were randomized between maintenance or observation; 32 were not because of: stable/progressive disease (16), adverse events (10) or other causes (6). Overall response at the end of treatment was 86% with 69% CR and 18% PR; PCR negativity at the end of treatment was 75%. Rituximab consolidation was able to induce CR in 37/90 (41%) partial responders and to increase PCR negativity from 61% to 75%. With a median follow-up of 22 months, two-years OS and PFS were 92% (95% CI 87%-95%) and 75% (95% CI 68%-81%), respectively (see Figure). Two-years PFS rates according to FLIPI score were 85% for low/intermediate risk and 65% for high risk (p 〈 0.001); 2-years PFS rates were 57% and 79% respectively in patients with and without B symptoms (p 〈 0.001). The patients in more advanced decade ( 〉 70 years) or those with 2 or more comorbidities did as well as younger ones or those with one or no comorbidities: 2-yr PFS rates for patients more or less seventy were 73% vs 76% (p = 0.39); for patients with ≥2 comorbidities or one or none were 84% vs 67% vs 76%, respectively (p = 0.82). A total of 1119 courses were delivered; the most frequent CTC grade 3-4 toxicity was neutropenia in 25% of the courses, with only 13 serious infections. One patients developed acute myelogenous leukaemia during treatment and died. Two toxic deaths during treatment (0.8%) occurred: 1 HBV reactivation and 1 Steven Johnson syndrome. So far 212 patients are alive; besides the above mentioned deaths, 15 patients died of lymphoma, 2 died of cardiac failure, 1 died of stroke and 1 died of drowning. So far too few events occurred to proper analyse the efficacy of the Rituximab maintenance. In the maintenance/observation phase the following severe (WHO grade 3-4) toxicities were recorded: 15 patients experienced neutropenia, seven cardiac events, four infections; no other relevant toxicities were recorded. The cumulative incidences of toxic events accounting for competing events at 18 months for maintenance arm (Arm A) versus observation arm (Arm B) were as follows: neutropenia 17% vs 1% (p 〈 0.001); infections 2% vs 2% (p = 0.586); cardiac events 4% vs 4% (p= 0.627). Conclusions a short term chemo-immunotherapy R-FND + Rituximab consolidation is safe and effective with a good 2-yr PFS rate also in patients with high risk FLIPI score or in patients in more advanced decade or with comorbidities. Rituximab maintenance is safe with a more frequent neutropenia that was not associated with an increased risk of infections. Final results of the study will provide insights on the role of Rituximab maintenance after R-chemotherapy. Disclosures Vitolo: Roche: Lecture fees; Mundipharma: Lecture fees. Off Label Use: Study was supported by Roche: Rituximab maintenance in first line treatment is off-label. Boccomini:Roche: Lecture fees. Ladetto:Roche Italy: Research Funding; Amgen: Honoraria, Research Funding.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V114.22.1706.1706
    RVK:
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    RVK:
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2009
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  • 2
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    Role of New Tyrosine Kinase Inhibitors in Osteoblastogenesis
    American Society of Hematology ; 2008
    In:  Blood Vol. 112, No. 11 ( 2008-11-16), p. 4751-4751
    Details
    In: Blood, American Society of Hematology, Vol. 112, No. 11 ( 2008-11-16), p. 4751-4751
    Abstract: It has been reported that imatinib mesylate (IM) may affect bone tissue remodeling mainly by both an inhibitory activity on osteoclastogenesis and an induction of osteoblastogenesis. Dasatinib (DA) and Nilotinib (NI) are new generation tyrosine kinase inhibitors presently approved for chronic myeloid leukemia patients after imatinib failure. We therefore evaluated possible effects of DA and NI on osteoblatic differentiation of Mesenchymal Stem Cells derived from bone marrow (BM-MSCs). BM-MSCs are multipotent non-haematopoietic progenitor cells that differentiate into osteoblasts, adipocytes, chondrocytes, skeletal myocytes and nervous cells. Mesenchymal stem cells (hBM-MSCs) were obtained from bone marrow samples of normal healthy adult bone marrow donors, isolated by density gradient (mononuclear fraction) and cultured either in standard medium (SM) or in osteogenic medium (OM) (0.2 mM ascorbic acid, 0.1 μm dexamethasone and 10 mM β-glycerophosphate) with or without DA 2nM or NI 100nM. Osteogenic differentiation of hBM-MSCs was evaluated by changes in morphology, presence of mineralized nodules (evidenced by Alizarin red) and expression of osteoblast-associated genes such as osteocalcin (OCN), RUNX2 and Bone morphogenetic protein (BMP-2) evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and analyzed by Scion Image. After 21days of culture, in comparison to control cultures, hBM-MSCs placed in OM, DA, NI and DA+OM, NI+OM exhibited changes in cell morphology from a spindle-shaped fibroblastic appearance to a rounder more cuboidal shape and the cells formed an extensive network of dense multilayered nodules (extracellular mineralization). Table I indicates mRNA expression of osteogenic markers in different culture conditions and shows that both DA and NI alone or in combination with OM, increase RUNX2, OCN, and BMP-2 expression. SM DA NI OM DA + OM NI + OM SM= standard medium, OM= osteogenic medium, DA= dasatinib, NI= nilotinib In summary, our data show that both DA and NI, as already reported IM, may induce osteogenic differentiation of mesenchymal cells thus indicating that they potentially favour osteoblastogenesis. RUNX2 1,59 0,20 2,09 0,16 4,2 0,31 2,86 0,25 4,41 0,41 4,18 0,24 OCN 2,57 0,28 3,2 0,14 3,14 0,09 3,59 0,17 3,6 0,28 3,62 0,25 BMP-2 1,55 0,19 2,27 0,17 4,16 0,27 2,84 0,28 4,43 0,30 4,21 0,30
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V112.11.4751.4751
    RVK:
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    RVK:
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    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2008
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  • 3
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    NPM1 Mutations Are Responsible for Better Response to Induction Therapy in AML Patients through the Inactivation of NF-kB.
    American Society of Hematology ; 2005
    In:  Blood Vol. 106, No. 11 ( 2005-11-16), p. 105-105
    Details
    In: Blood, American Society of Hematology, Vol. 106, No. 11 ( 2005-11-16), p. 105-105
    Abstract: Mutations in NPM1 exon 12 and the resulting shift of NPM1 into the cytoplasm are the most specific and frequent events in acute myeloid leukaemia patients with normal karyotype. Cytoplasmatic NPM is associated with responsiveness to induction chemotherapy, although its role in predicting outcome after remission remains to be defined. The aim of the study was to identify the molecular mechanisms responsible for chemosensitivity in leukemic cells carrying the mutation of NPM1. NF-kB is a transcription factor involved in many intracellular pathways including apoptosis. NF-kB is a heterodimer of p50 and p65 subunits sequestered in the cytoplasm in its inactive form through interaction with inhibitory IKB proteins and activated in the nucleous after degradation of IKB. The activation of NF-kB is responsible for chemoresistance to different drugs including anthracyclines. Based on this assumption, we analyzed the possible cytoplasmatic interaction between the mutated form of NPM1 (NPM+) and NF-kB. The NF-kB DNA binding activity was analyzed in 20 BM samples collected from AML patients carrying the NPM1 mutations and 30 NPM1 wild type samples (NPM1−) using an ELISA method. Immunofluorescence analysis using NPM1 and p65 antibodies was performed to identify the localization of both proteins. Western blot for p65 and NPM1 was used to confirm the protein amount and localization. Finally, co-immunoprecipitation assay was perform to study the interaction of the two proteins. We found a significant lower DNA binding activity in NPM1 mutated cells when compared to the wild type NPM cells (p=0,001). Immunofluorescence analysis confirmed the cytoplasmatic localization of NPM protein in mutated samples and the nuclear localization in wild type samples. In addition, immunofluoresence analysis performed with a monoclonal antibody against p65 subunit shows different pattern of NF-kB localization in NPM1+ when compared to NPM1−. In particular, in NPM1+ cells NF-kB is mainly localized in the cytoplasm in the inactive form and in NPM− cells is mainly nuclear localized. These data were confirmed by Western blot carried out with the same monoclonal antibody against p65 in the nuclear and cytosolic extracts. The interaction of NPM1 and NF-kB was further investigated and demonstrated by co-immunoprecipitation studies. In conclusion, we demonstrated that p65 and NPM1 interact with each other within the cytoplasm and this interaction results in the sequestration of NF-kB within the cytoplasm. The cytosolic localization of the inactive form of NF-kB explains the reduced NF-kB DNA binding activity observed in NPM1+ patients. These data may provide a possible explanation for the chemosensitivity observed in NPM+ patients. Furthermore, since NF-kB is involved in the transcription of many genes which regulate proliferation and differentiation processes, the disruption of NF-kB function may represent one of the mechanism of leukemogenesis induced by NPM1 mutated proteins.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V106.11.105.105
    RVK:
    XA 33000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2005
    detail.hit.zdb_id: 1468538-3
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  • 4
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    Overexpression of the p65 Subunit of NF-kB and IkB Mediated Nuclear Sequestration of p53 as Common Events in Philadelphia Positive and Negative Chronic Myeloid Leukemia.
    American Society of Hematology ; 2005
    In:  Blood Vol. 106, No. 11 ( 2005-11-16), p. 2871-2871
    Details
    In: Blood, American Society of Hematology, Vol. 106, No. 11 ( 2005-11-16), p. 2871-2871
    Abstract: Introduction. Chronic Myeloid Leukemia (CML) is a myeloproliferative disorder caused by the Philadelphia translocation. Rare patients with a clinical presentation of CML are negative for the Ph chromosome. The pathogenesis of Ph negative CML is still unknown. Different reports have demonstrated that the transcription factor NF-kappaB is essential for Bcr-Abl mediated transformation. NF-kappaB is composed of two subunits (mainly p65 and p50) which are retained into the cytoplasm by the inhibitory protein IkappaB-alpha. Different stimuli trigger IkappaB degradation and nuclear translocation of NF-kappaB, where it mediates the transcription of different genes involved in cellular proliferation, transformation and resistance to apoptosis. Aim of the work. We have evaluated the role of NF-kappaB in primary chronic myeloid leukemia samples both positive and negative for the Philadelphia chromosome. Methods. Bone marrow samples of 10 chronic myeloproliferative disorders (6 Ph positive and 4 Ph negative CML), 1 CML blast phase, 2 Acute Myeloid Leukemia and 3 healthy donor have been collected at diagnosis. Each sample has been lysed to obtain cytosolic and nuclear extracts. Western blot have been performed to evaluate the expression of p65 and the regulatory protein IkappaB-alpha. DNA binding activity of NF-kappaB has been measured with an ELISA method (TransAM). To inhibit NF-kB, primary cells have been incubated with 1 microM MG-132, 90 microM Resveratrol and 5 microM Bay11-7082 or have been infected with a lentivirus construct containing dsRNA directed against the p65 subunit of NF-kB and a lentivirus expressing a mutated IKB which retains NF-kB inactive in the cytoplasm. Results. Ph+ and Ph- CML samples express both in the cytosol and in the nucleus higher levels of p65 respect to normal peripheral blood and normal bone marrow samples. In normal samples IkB-alpha is detectable only in the cytosol while in Ph+ and Ph- CML samples it is predominately expressed in the nucleus. DNA binding activity of NF-kappaB is not particularly increased in CML respect to normal bone marrow samples. Only CML blast phase and Acute Myeloid Leukemia show markedly increased DNA binding activity of NF-kappaB. Immunoprecipitates of nuclear and cytosolic IkappaB-alpha have been performed. The pro-apoptotic p53 co-immunoprecipitates with IkappaB-alpha. Treatment with NF-kappaB inhibitors MG-132, Resveratrol and Bay11-7082 disrupts p53-IkBalpha dimer rendering cells susceptible to the apoptotic stimulation induced by Doxorubicine. To confirm these data, primary CML samples have also been infected with a lentivirus construct containing dsRNA directed against p65 and a lentivirus expressing a mutated IKB which retains NF-kB inactive in the cytoplasm. In both cases cells becomes more sensitive to Doxorubicin-induced apoptosis, due to disruption of IkB - p53 dimer. Conclusion. Nuclear and cytosolic IkappaB-alpha mediated p53 sequestration is a common event in both Ph+ and Ph- CML, which may contribute to the pathogenesis of this disorder due to impairment of p53 pro-apoptotic functions. NF-kB inhibition may represent a powerful strategy to render CML cells more susceptible to apotosis.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V106.11.2871.2871
    RVK:
    XA 33000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2005
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  • 5
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    Role of Imatinib Mesylate in Osteoblastogenesis.
    American Society of Hematology ; 2007
    In:  Blood Vol. 110, No. 11 ( 2007-11-16), p. 1928-1928
    Details
    In: Blood, American Society of Hematology, Vol. 110, No. 11 ( 2007-11-16), p. 1928-1928
    Abstract: Imatinib mesylate (IM), a tyrosine kinase inhibitor, currently used in chronic myeloid leukaemia (CML) may also affect the growth of other cellular systems besides CML cells. It has been reported that IM may affect bone tissue remodeling mainly by an inhibitory activity on osteoclastogenesis. We therefore evaluated possible effects of IM on osteoblatic differentiation of Mesenchymal Stem Cells derived from bone marrow (BMSCs). BMSCs are multi-potent non-haematopoietic progenitor cells that differentiate into osteoblasts, adipocytes, chondrocytes, skeletal myocytes and nervous cells. Culture of normal human BMSCs were treated with osteogenic medium (OM) with or without IM 1 μM. By RT-PCR, we assessed mRNA expression of osteogenic markers such as RUNX2, osteocalcin (OCN) and osteopontin (OPN) at 7, 14, and 21 days of culture. BMSCs treated with OM and IM 1 μM showed increased levels of osteogenic markers mRNA as compared to BMSCs cultured with OM only (RUNX2 ctrl=0,37±0,02 vs OM+IM=0,79±0,06; OCN ctrl=0,36±0,04 vs OM+IM= 0,97±0,03; OPN ctrl=0,94±0,01 vs OM+IM= 1,55±0,13). We also evaluated the OCN levels, and the OPG (osteoprotegerin)/RANKL (receptor activator of nuclear factor-kappa B ligand) ratio (OPG/RANKL ratio) in the surnatant of the culture at day 21 by ELISA assays. OPG/RANKL ratio (OM alone = 55,4±0,4 vs OM+IM = 65,3±0,7; P & lt;0,005) and OCN levels (OM alone = 1,4±0,08 ng/mL vs OM+IM= 4,02±0,21 ng/mL; P & lt;0,005) were increased in BMSCs samples cultured with IM in comparison to control (OM alone). In addition, we examined the OPG/RANKL ratio in serum of 17 CML patients treated for at least two years with IM and we found that it was increased in comparison to normal controls (ctrl=1,0±0,2 vs patients= 3,1±2,63; P= 0,036). In summary, our data show that IM increases osteogenic markers’ mRNA expression in BMSCs and increase the OPG/RANKL ratio both in surnatant of BMSCs cultured with IM and in serum of patients treated with IM, thus indicating that IM potentially favours osteoblastogenesis.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V110.11.1928.1928
    RVK:
    XA 33000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2007
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 6
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    LOW SPARC EXPRESSION IN CML and ITS Upregulation DURING Imatinib TREATMENT.
    American Society of Hematology ; 2009
    In:  Blood Vol. 114, No. 22 ( 2009-11-20), p. 4258-4258
    Details
    In: Blood, American Society of Hematology, Vol. 114, No. 22 ( 2009-11-20), p. 4258-4258
    Abstract: Abstract 4258 SPARC, also known as osteonectin, is a highly conserved between species phosphoprotein that has been recently identified as a tumor suppressor gene. Besides its involvement in bone metabolism, where it mediates collagen deposition, it has been shown that SPARC plays several roles, ranging from cell adhesion to inhibition of cell-cycle progression and VEGF activation. In mice, it has been reported that implanted tumors grow faster in SPARC-null animals. In humans, patients affected by MDS 5q-syndrome responsive to lenalidomide, have an increase of SPARC expression. Chronic myeloid leukemia (CML) is a disease characterized by uncontrolled proliferation and adhesion defect. In our study we investigated the expression of SPARC mRNA by quantitative PCR in 22 CML patients. mRNA SPARC relative expression in mononuclear cells isolated from peripheral blood at diagnosis was significantly lower (range 0.004-0.98, mean 0.3, median 0.21, SD 0.3) than in normal control subjects assumed as a reference (range 0.31-2.5, mean 1, median 0.8, SD 0.8). During imatinib treatment, SPARC mRNA increased of 2 logs at 3 months and of 3 logs at 1 year. In one patient that had to stop imatinib treatment a decrease of expression to levels comparable to normal subjects, around 1 log higher than pretreatment levels, was noticed; when the patient restarted treatment with the tyrosine kinase inhibitor, SPARC level raised of 2 logs again. Bcr/Abl+ K562 cell line has a low level of SPARC mRNA (0.4 relative expression compared to pooled normal controls), probably due to promoter hypermethylation. Treatment of K562 with an hypomethylating agent, such as 5-azacytidine, for 72 h resulted in an increased expression of SPARC mRNA of 1 log. Moreover, K562 proliferation at 72 h was inhibited by adding esogenous SPARC to colture medium with an IC50 of 50 mcg/ml. In the presence of imatinib 1 μM, SPARC IC50 was lowered to 30 mcg/ml. Taken all together these data suggest that SPARC deficiency in CML could play a role in excess growth, cell adhesion and angiogenesis impairment. Furthermore, its upregulation after imatinib treatment may be related to the alteration of bone metabolism that is observed in CML patients treated with this tyrosine kinase inhibitor. Disclosures: No relevant conflicts of interest to declare.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V114.22.4258.4258
    RVK:
    XA 33000
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    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2009
    detail.hit.zdb_id: 1468538-3
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  • 7
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    Valproate enhances imatinib‐induced growth arrest and apoptosis in chronic myeloid leukemia cells
    Wiley ; 2006
    In:  Cancer Vol. 106, No. 5 ( 2006-03), p. 1188-1196
    Details
    In: Cancer, Wiley, Vol. 106, No. 5 ( 2006-03), p. 1188-1196
    Abstract: This study found that administration of valproate enhanced cytotoxic effects of imatinib in those patient resistant to imatinib or in which complete cytogenetic remission had yet to be reached.
    Type of Medium: Online Resource
    ISSN: 0008-543X , 1097-0142
    URL: Issue
    URL: Article
    DOI: 10.1002/cncr.v106:5
    DOI: 10.1002/cncr.21725
    Language: English
    Publisher: Wiley
    Publication Date: 2006
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    detail.hit.zdb_id: 2599218-1
    detail.hit.zdb_id: 2594979-2
    detail.hit.zdb_id: 1429-1
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  • 8
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    CD200 expression may help in differential diagnosis between mantle cell lymphoma and B-cell chronic lymphocytic leukemia
    Elsevier BV ; 2009
    In:  Leukemia Research Vol. 33, No. 9 ( 2009-9), p. 1212-1216
    Details
    In: Leukemia Research, Elsevier BV, Vol. 33, No. 9 ( 2009-9), p. 1212-1216
    Type of Medium: Online Resource
    ISSN: 0145-2126
    URL: Article
    DOI: 10.1016/j.leukres.2009.01.017
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
    detail.hit.zdb_id: 2008028-1
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  • 9
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    Hypoxia Induces Imatinib Resistance in CML Cell Lines.
    American Society of Hematology ; 2006
    In:  Blood Vol. 108, No. 11 ( 2006-11-16), p. 4387-4387
    Details
    In: Blood, American Society of Hematology, Vol. 108, No. 11 ( 2006-11-16), p. 4387-4387
    Abstract: Background: Imatinib is a potent tyrosine kinase inhibitor that is highly effective in the treatment of chronic myeloid leukemia. However, some patients are resistant to imatinib. Some of the mechanisms leading to imatinib resistance include amplification of the BCR-ABL gene, determining overexpression of the protein, and mutations in the BCR-ABL protein with alteration of imatinib binding sites. Imatinib uptake is an active process mediated by a group of transporters that includes the organic cation transporters (hOCT) and it has been shown that different expression of OCT1 may play a critical role on intracellular drug levels and, hence, resistance to imatinib. Hypoxia is another important factor that may contribute to drug resistance. Hypoxia-Inducible Factor (HIF-1α) and its downstream target, Vascular endothelial Growth Factor (VEGF), have been shown to be overexpressed in leukemic bone marrow specimens compared to normal bone marrow. The purpose of this study is to determine if the hypoxic conditions and OCT1 inhibition affect imatinib sensitivity. Methods: Chronic myeloid leukemic cell line K562 and LAMA84 were cultured in 10% serum RPMI medium under hypoxic (3% O2) or normoxic (21% O2) conditions. All samples were treated with imatinib 1μM ± prazosin 13 μM (OCT1 reversible inhibitor) for 24 hs. Results: Cells treated with imatinib and cultured under hypoxic conditions demonstrated decreased apoptosis and increased cell viability compared to normoxic conditions (K562 Annexin + cells 62% vs 94%, p= 0.003, LAMA84 Annexin + cells 61% vs 92%, p=0.0028). The addition of prazosin almost abrogated imatinib efficacy in normoxic environment but did not modify the effect of imatinib under hypoxic conditions. Conclusions: Our data confirm that OCT1 is the most important imatinib carrier. Exposure of CML cell lines to an hypoxic environment results in reduced sensitivity to imatinib and this effect wasn’t affected by OCT1 inhibition. Search for underlying mechanisms of these findings are in progress.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V108.11.4387.4387
    RVK:
    XA 33000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2006
    detail.hit.zdb_id: 1468538-3
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  • 10
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    Effect of Hypoxia on the Expression of BRIT1 in K562 Cell Line: Implication for Resistance to Imatinib.
    American Society of Hematology ; 2007
    In:  Blood Vol. 110, No. 11 ( 2007-11-16), p. 4530-4530
    Details
    In: Blood, American Society of Hematology, Vol. 110, No. 11 ( 2007-11-16), p. 4530-4530
    Abstract: BRIT1 (Microcephalin, MCPH1) is a chromatin binding protein that forms ionizing irradiation-induced nuclear foci (IRIF); it is a crucial DNA damage regulator in the ATM/ATR pathways. Here we have analyzed BRIT1 expression on K562 cell line after treatment with imatinib 0,1-1 μM, UV irradiation (12 μJ/cm2) and after exposure to an hypoxic condition (3% O2). K562 in standard culture conditions (21% O2) were used to establish BRIT1 basal expression. Total RNA from K562 cultures was prepared at 24 and 48 hs. 1 μg total RNA was reverse transcribed from each sample. TaqMan Gene expression assay (Applied Biosystems) in Real-Time PCR was employed to examine the expression of BRIT1. Cellular count was assayed by trypan blue. Treatment with IM (0,1 and 1 μM) and UV induced a 2–3 fold increased expression of BRIT1 at 24 h and a minor increase at 48 h. Cell mortality at 24 h was 30% for IM and 20% for UV while at 48 h cells started to grow again, possibly as a consequence of the DNA damage repair by BRIT1. Exposure of K562 cells to hypoxia increased BRIT1 expression about 5- and 6-folds at 24 and 48 h respectively. Cell mortality at 24 h was 30% while after 48 h it was 20%. We therefore concluded that BRIT1 expression increases in hypoxia more than after IM and UV exposure. Since we have found that K562 in hypoxic conditions are relatively resistant to imatinib, (K562 cell mortality after 24 h exposure to IM 1μM was 30% ± 0,3 in normoxia vs 9% ± 0,8 in hypoxia, P 〈 0,005) we have hypothesized that BRIT1 could be involved in resistance to IM. Therefore, we exposed K562 to UV and, after 48 h we incubated the cells with imatinib 1 μM. Pre-exposure of K562 cells to UV reduced imatinib-induced mortality (9,7% ± 1,6 vs 21,3% ± 1,5 of control, p 〈 0,005) thus indicating that upregulation of BRIT1 (as we have observed especially in hypoxia) could contribute to resistance to imatinib in K562 cell line. Understanding of BRIT1 function may well contribute to novel therapeutic approaches for cancer.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    URL: Article
    DOI: 10.1182/blood.V110.11.4530.4530
    RVK:
    XA 33000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2007
    detail.hit.zdb_id: 1468538-3
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