| 1. |
- Bergh, Gösta, et al.
(författare)
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Altered expression of the retinoblastoma tumor-suppressor gene in leukemic cell lines inhibits induction of differentiation but not G1-accumulation
- 1997
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Ingår i: Blood. - 1528-0020. ; 89:8, s. 2938-2950
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Tidskriftsartikel (refereegranskat)abstract
- The retinoblastoma tumor-suppressor gene, RB, has been implicated in tumor suppression, in regulation of the cell cycle, and in mediating cell differentiation. RB is necessary for hematopoiesis in mice, and aberrant RB-expression is associated with the progress and prognosis of leukemia. We have used antisense oligonucleotides, established clones stably expressing an antisense RB construct, and also established clones over expressing the retinoblastoma protein (pRb) to study the role of RB expression in monocytic differentiation induced by all-trans retinoic acid (ATRA) or 1-alpha-25-dihyroxycholecalciferol (Vit D3) in the monoblastic cell line U-937 and erythroid differentiation induced by transforming growth factor beta1 (TGFbeta1) and hemin in the erythroleukemic cell line K562. A reduction in pRb production in antisense RB-transfected U-937 clones was shown. Antisense oligonucleotides as well as expression of the antisense RB construct suppressed differentiation responses to ATRA or Vit D3, as judged by the capability to reduce nitro blue tetrazolium, by the appearance of monocyte-related cell surface antigens and by morphologic criteria. K562 cells showed decreased differentiation response to TGFbeta1, but not to hemin, when incubated with antisense oligonucleotides. U-937 antisense RB-transfected cells were also suppressed in their ability to upregulate levels of hypophosphorylated pRb when induced to differentiate. Although U-937 cells incubated with antisense oligonucleotides and clones expressing the antisense RB construct were hampered in their ability to differentiate on incubation with ATRA or Vit D3, the induced G0/G1-accumulation was similar to differentiating control cells treated with ATRA or Vit D3. Intriguingly, U-937 clones overexpressing RB were also inhibited in their differentiation response to ATRA or Vit D3 but not inhibited in their ability to respond with G0/G1 accumulation when induced with these substances. The results indicate that pRb plays a role in induced differentiation of U-937 cells as well as K562 cells involving mechanisms that, at least partially, are distinct from those inducing G1 accumulation.
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| 2. |
- Ehinger, Mats, et al.
(författare)
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Expression of the p53 tumor suppressor gene induces differentiation and promotes induction of differentiation by 1,25-dihydroxycholecalciferol in leukemic U-937 cells
- 1996
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Ingår i: Blood. - 1528-0020. ; 87:3, s. 1064-1074
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Tidskriftsartikel (refereegranskat)abstract
- Leukemic U-937 cells, which lack normal p53, were stably transfected with a temperature-sensitive mutant of p53 to investigate the consequences for growth and differentiation. On induction of wild-type p53 activity at the permissive temperature, some of these cells underwent maturation as judged by the capacity for oxidative burst and the appearance of monocyte related cell surface molecules. Moreover, wild-type p53-expressing cells were more sensitive than p53-negative control cells to induction of differentiation by 1,25-dihydroxycholecalciferol; a twofold to fourfold increase of the fraction of cells showing signs of terminal maturation was observed when wild-type p53-expressing cells were incubated with 1,25-dihydroxycholecalciferol at concentrations that only slightly affected control cells. Whereas wild-type p53 activity per se induced maturation of certain cells, other underwent cell death judging from the reduced capability to exclude trypan blue and the appearance of fragmented DNA in flow cytometric analysis. The p53-induced cell death could be inhibited by incubation with 1,25-dihydroxy-cholecalciferol, but not all-trans retinoic acid. Thus, 1,25-dihydroxycholecalciferol, seemed to increase the survival of wild-type p53-expressing cells and to cooperate with wild-type p53 to induce differentiation. The data imply that p53-mediated maturation in U-937 cells depends on optimal regulation of signals for differentiation, survival and proliferation, and suggest a role for p53 in the differentiation induction of leukemic cells.
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| 3. |
- Ehinger, Mats, et al.
(författare)
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Involvement of the tumor suppressor gene p53 in tumor necrosis factor-induced differentiation of the leukemic cell line K562
- 1995
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Ingår i: Cell Growth and Differentiation. - 1044-9523. ; 6:1, s. 9-17
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Tidskriftsartikel (refereegranskat)abstract
- The cDNA of the human wild-type p53 tumor suppressor gene was constitutively overexpressed in the leukemic cell line K562 (which lacks detectable amounts of p53 protein) in order to investigate the consequences for growth and differentiation. Several stable clones were established by transfection of the expression vector pc53SN3. Expression of p53 protein was characterized by biosynthetic labeling and immunoprecipitation with the monoclonal antibodies pAb 1801 (reacting with wild-type and mutant human p53), pAb 240 (reacting with mutant human p53) and pAb 1620 (reacting with wild-type human p53). All clones which were 1801+, 240-, 1620- or 1801+, 240-, 1620+ were defined as "wild-type-like p53-expressing" clones. Our results show that expression of p53 protein is compatible with continuous proliferation of K562 cells. The growth characteristics of wild-type-like p53-expressing clones did not differ from that of control clones. However, the former were more sensitive than p53-negative control clones to growth inhibition by tumor necrosis factor (TNF), a cytokine with a potential role in growth and differentiation of myeloid leukemic cells. In addition, a 2- to 4-fold increase of the amount of hemoglobin, a marker of erythroid differentiation, was observed when wild-type-like p53 protein-expressing clones were incubated with TNF. This suggests that differentiation is the mechanism responsible for the increased TNF sensitivity of these clones. Our results support a role for p53 in mediating growth inhibitory and differentiation inducing signals by TNF.
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| 4. |
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| 5. |
- Olsson, Inge, et al.
(författare)
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Blodbildning. : Biologisk massproduktion under noggrann kontroll av cytokiner
- 1995
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Ingår i: Lakartidningen. - 0023-7205. ; 92:14, s. 6-1475
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Forskningsöversikt (refereegranskat)abstract
- Haematopoiesis is regulated by unrelated, pleiotropic, and diverse regulatory molecules, cytokines, whose membrane receptors are related and restricted to a few families manifesting sequence homology. Most members of the cytokine receptor family which lack tyrosine kinase activity are composed of multiple chains. An accessory signal transducer can be shared by members of the receptor family. Cytokine receptor oligomerisation is required for signal transduction, which includes phosphorylation of receptors and cytoplasmic proteins. Upon ligand binding, the receptors for erythropoietin and G-CSF form homodimers, whereas other members of the receptor family form hetero-oligomers in order to generate high-affinity receptor and signal transduction. In their cytoplasmic part, cytokine receptors contain distinct functional domains, proximal and distal to the membrane, that generate separate signals. Cytokines can be used to minimise chemotherapy-induced neutropenia and treat chronic neutropenia, and to shorten the period of aplasia following bone marrow transplantation.
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| 6. |
- Svedberg, Helena, et al.
(författare)
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Constitutive expression of the Wilms' tumor gene (WT1) in the leukemic cell line U937 blocks parts of the differentiation program
- 1998
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 1476-5594 .- 0950-9232. ; 16:7, s. 925-932
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Tidskriftsartikel (refereegranskat)abstract
- The Wilms tumor gene, WT1, encodes a zinc-finger DNA binding protein which is thought to function as a tissue specific transcription factor, regulating cell growth and differentiation. High expression of WT1 has been detected in a range of acute leukemias. To elucidate a role for WT1 in leukemogenesis, we transfected the monoblastic cell line U937, which lacks detectable levels of endogenous WT1, with two isoforms of WT1. We showed that, in contrast to U937 control cells, cells constitutively expressing either of the isoforms, WT1(-KTS) or WT1(+KTS), did not respond to differentiation induction by retinoic acid or vitamin D3, as judged by the capacity to reduce nitro blue tetrazolium and morphology. Although U937 cells expressing WT1 were hampered in their ability to differentiate on incubation with retinoic acid and vitamin D3, the induced G1/G0-accumulation was similar to differentiating control cells treated with inducers. Furthermore, distinct effects on the maturation process were indicated by downregulation of the myeloid cell surface makers CD13 and CD15, while the upregulation of CD14 and CD11c on WT1 transfected cells was similar to control cells upon incubation with retinoic acid and vitamin D3. Taken together our results demonstrate that a constitutive expression of WT1 in the leukemic cell line U937 leads to impairment of differentiation responses, indicating that a high expression of WT1 can contribute to the differentiation block of acute leukemia.
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