| 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. |
- Bergh, Gösta, et al.
(författare)
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Forced expression of the cyclin-dependent kinase inhibitor p16(INK4A) in leukemic U-937 cells reveals dissociation between cell cycle and differentiation
- 2001
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Ingår i: Experimental Hematology. - 1873-2399. ; 29:12, s. 1382-1391
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to investigate how the tumor suppressor protein p16(INK4A) interferes with growth and differentiation of leukemic U-937 cells. MATERIALS AND METHODS: U-937 clones constantly overexpressing the cyclin-dependent kinase inhibitor p16(INK4A) were established. Clones transfected with empty vector were used as controls. The effects of high-level expression of p16(INK4A) on proliferation and cell cycle progression were investigated (cell cycle distribution, proliferation rate, analyses of different cell cycle regulatory proteins). The effect of introduction of p16(INK4A) on capacity for induced differentiation, assayed by capacity to reduce nitroblue tetrazolium, was determined. RESULTS: Overexpressed p16(INK4A) protein was active as judged by its ability to bind to CDK-4 in a coimmunoprecipitation assay. Clones overexpressing p16(INK4A) grew slower than controls, without any apparent effects on the phosphorylation status of the retinoblastoma protein (pRb). Instead, p16(INK4A) overexpression affected the phosphorylation status of pRb-related pocket protein p130, which was detected in its growth-restraining hypophosphorylated form. Despite an enhanced tendency to accumulate in G(0)/G(1), p16(INK4A)-overexpressing cells were less sensitive to induction of differentiation with vitamin D(3) or ATRA than control cells. CONCLUSIONS: Constitutive expression of p16(INK4A) in U-937 cells resulted in decreased proliferation as a result of activated p130 rather than pRb. Also, we showed that introduction of p16(INK4A) into U-937 cells impaired their capacity to differentiate. Moreover, the results support the notion that cell differentiation and cell cycle progression are dissociated and independently regulated processes.
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| 3. |
- Bergh, Gösta
(författare)
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On the role of the retinoblastoma tumor suppressor gene in hematopoietic differentiation
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study was to investigate the role of some tumor suppressor gene products (with emphasis on the retinoblastoma suppressor gene product) in the regulation of differentiation and proliferation in leukemic and normal hematopoietic cells. For this purpose, the expression of the tumor suppressor genes RB, p53 and p16 were artificially altered. Cells used were human leukemic cell lines and isolated human bone marrow progenitors. The results show that the retinoblastoma protein, pRb, is involved in the differentiation of human leukemic cell lines, probably through mechanisms that are separate from pRb’s well established ability to regulate cell cycle progression. Suppression of pRb by antisense RB oligonucleotides in isolated bone marrow cells inhibited the monocytic maturation but simultaneously promoted the alternative neutrophilic pathway, indicating an important role for pRb in human myeloid lineage commitment. Again, this effect of pRb seemed mediated through mechanisms distinct from pRb’s cell cycle regulatory potential. Artificial over expression of p53 in leukemic cells lacking p53 made them more responsive to differentiation signals. Arrest of cell proliferation did not enhance the capacity for differentiation, suggesting that cell differentiation and cell cycle regulation are separately regulated processes.
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| 4. |
- Bergh, Magnus, et al.
(författare)
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Feasibility of imaging living cells at subnanometer resolutions by ultrafast X-ray diffraction
- 2008
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Ingår i: Quarterly reviews of biophysics (Print). - 0033-5835 .- 1469-8994. ; 41:3-4, s. 181-204
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Forskningsöversikt (refereegranskat)abstract
- Detailed structural investigations on living cells are problematic because existing structural methods cannot reach high resolutions on non-reproducible objects. Illumination with an ultrashort and extremely bright X-ray pulse can outrun key damage processes over a very short period. This can be exploited to extend the diffraction signal to the highest possible resolution in flash diffraction experiments. Here we present an analysis or the interaction of a very intense and very short X-ray pulse with a living cell, using a non-equilibrium population kinetics plasma code with radiation transfer. Each element in the evolving plasma is modeled by numerous states to monitor changes in the atomic populations as a function of pulse length, wavelength, and fluence. The model treats photoionization, impact ionization, Auger decay, recombination, and inverse bremsstrahlung by solving rate equations in a self-consistent manner and describes hydrodynamic expansion through the ion sound speed, The results show that subnanometer resolutions could be reached on micron-sized cells in a diffraction-limited geometry at wavelengths between 0.75 and 1.5 nm and at fluences of 10(11)-10(12) photonS mu M (2) in less than 10 fs. Subnanometer resolutions could also be achieved with harder X-rays at higher fluences. We discuss experimental and computational strategies to obtain depth information about the object in flash diffraction experiments.
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| 5. |
- Chapman, Henry N., et al.
(författare)
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Femtosecond diffractive imaging with a soft-X-ray free-electron laser
- 2006
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 2:12, s. 839-843
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Tidskriftsartikel (refereegranskat)abstract
- Theory predicts(1-4) that, with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft-X-ray free-electron laser. An intense 25 fs, 4 x 10(13) W cm(-2) pulse, containing 10(12) photons at 32 nm wavelength, produced a coherent diffraction pattern from a nanostructured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single-photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling(5-9), shows no measurable damage, and is reconstructed at the diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one(10).
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| 6. |
- Chapman, Henry N, et al.
(författare)
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Femtosecond time-delay X-ray holography
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 448:7154, s. 676-679
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Tidskriftsartikel (refereegranskat)abstract
- Extremely intense and ultrafast X-ray pulses from free-electron lasers offer unique opportunities to study fundamental aspects of complex transient phenomena in materials. Ultrafast time-resolved methods usually require highly synchronized pulses to initiate a transition and then probe it after a precisely defined time delay. In the X-ray regime, these methods are challenging because they require complex optical systems and diagnostics. Here we propose and apply a simple holographic measurement scheme, inspired by Newton's 'dusty mirror' experiment1, to monitor the X-ray-induced explosion of microscopic objects. The sample is placed near an X-ray mirror; after the pulse traverses the sample, triggering the reaction, it is reflected back onto the sample by the mirror to probe this reaction. The delay is encoded in the resulting diffraction pattern to an accuracy of one femtosecond, and the structural change is holographically recorded with high resolution. We apply the technique to monitor the dynamics of polystyrene spheres in intense free-electron-laser pulses, and observe an explosion occurring well after the initial pulse. Our results support the notion that X-ray flash imaging2, 3 can be used to achieve high resolution, beyond radiation damage limits for biological samples4. With upcoming ultrafast X-ray sources we will be able to explore the three-dimensional dynamics of materials at the timescale of atomic motion.
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| 7. |
- 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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| 8. |
- Hagman, Anna, et al.
(författare)
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Obstetric and neonatal outcome after oocyte donation in 106 women with Turner syndrome: a Nordic cohort study.
- 2013
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Ingår i: Human reproduction (Oxford, England). - : Oxford University Press (OUP). - 1460-2350 .- 0268-1161. ; 28:6, s. 1598-609
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Tidskriftsartikel (refereegranskat)abstract
- What are the obstetric and neonatal outcomes of deliveries after oocyte donation (OD) in women with Turner syndrome (TS)? SUMMARY ANSWER: Pregnancies among women with TS carry a substantial risk, particularly for hypertensive disorders. Potentially life-threatening complications occurred in 3.3% of pregnancies. The neonatal outcomes were generally reassuring, with similar rates of preterm birth and low birthweight (LBW) as after conventional IVF and better than previously reported in deliveries after OD in women with TS. WHAT IS KNOWN ALREADY: OD pregnancies in women with TS are known to be high-risk pregnancies. STUDY DESIGN, SIZE, DURATION: This retrospective cohort study included 106 women with TS who delivered after OD (n = 122 deliveries, n = 131 newborns) in three Nordic countries (Finland, Denmark, Sweden) between 1992 and 2011. PARTICIPANTS, SETTING AND METHODS: Women with TS who delivered after OD in three Nordic countries were identified (n = 110). Four women declined to participate or were lost to follow-up, thus 106 women were included in the study. The medical data from fertility clinics, antenatal clinics and the hospitals where the women had been treated and/or delivered were scrutinized. MAIN RESULTS AND THE ROLE OF CHANCE: In this cohort, the karyotype was 45,X in 44% of the women with TS. Ten women (9.4%) had a known cardiac defect before pregnancy. Single embryo transfer was performed in 70.3% of the cases and the multiple birth rate was 7.4%. In total, 35.0% of the pregnancies were associated with a hypertensive disorder including pre-eclampsia in 20.5%. Potentially life-threatening complications occurred in four pregnancies (3.3%), including one woman with aortic dissection, one with mild regurgitation of the tricuspid and mitral valve, one with a mechanical heart valve who developed HELLP syndrome (haemolysis, elevated liver enzymes, low platelets) and one who underwent a post-partum hysterectomy due to severe haemorrhaging. Neonatal outcomes were reassuring, with a preterm birth rate of 8.0% and LBW rate of 8.8% in singletons. Major birth defects were found in 3.8% of the children. The perinatal mortality was 2.3% (3/131), including a set of extremely preterm twins. LIMITATIONS, REASONS FOR CAUTION: Although this study was performed over a period of almost 20 years in three different countries, with a low drop-out rate and little missing data, much larger series are needed to assess rare events. This study also lacks an appropriate control group. WIDER IMPLICATIONS OF THE FINDINGS: This study suggests that cardiovascular evaluation before and during pregnancy may contribute to favourable obstetric outcomes in many cases. Maternal outcomes were in agreement with the literature while neonatal outcomes were generally better than previously reported. The outcomes were consistent across the three countries, supporting generalizability to similar populations. STUDY FUNDING/COMPETING INTEREST(S): No conflict of interest was reported. The study was supported by grants from the Gothenburg Medical Society, the Medical Care Executive Board of the Region Västra Götaland, grants from the ALF agreement at the Sahlgrenska University Hospital, the Hjalmar Svensson foundation, NFOG Nordic Fund, the Finnish Society of Paediatric and Adolescent Gynecology and Liv och hälsa Foundation in Finland. The Nordic Expert group's research work was unconditionally supported by MSD Finland, Norway and Denmark.
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| 9. |
- Nilsson, Lars, et al.
(författare)
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The molecular signature of MDS stem cells supports a stem-cell origin of 5q-myelodysplastic syndromes
- 2007
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:8, s. 3005-3014
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Tidskriftsartikel (refereegranskat)abstract
- Global gene expression profiling of highly purified 5q-deleted CD34+CD38–Thy1+ cells in 5q– myelodysplastic syndromes (MDSs) supported that they might originate from and outcompete normal CD34+CD38–Thy1+ hematopoietic stem cells. Few but distinct differences in gene expression distinguished MDS and normal stem cells. Expression of BMI1, encoding a critical regulator of self-renewal, was up-regulated in 5q– stem cells. Whereas multiple previous MDS genetic screens failed to identify altered expression of the gene encoding the myeloid transcription factor CEBPA, stage-specific and extensive down-regulation of CEBPA was specifically observed in MDS progenitors. These studies establish the importance of molecular characterization of distinct stages of cancer stem and progenitor cells to enhance the resolution of stage-specific dysregulated gene expression.
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| 10. |
- 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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