| 1. |
|
|
| 2. |
- Bergh, Gösta, et al.
(författare)
-
Altered expression of the retinoblastoma tumor-suppressor gene in leukemic cell lines inhibits induction of differentiation but not G1-accumulation
- 1997
-
Ingår i: Blood. - 1528-0020. ; 89:8, s. 2938-2950
-
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.
|
|
| 3. |
|
|
| 4. |
- Ehinger, Mats, et al.
(författare)
-
p53-dependent and -independent differentiation of leukemic U-937 cells : relationship to cell cycle control
- 1998
-
Ingår i: Experimental Hematology. - 1873-2399. ; 26:11, s. 52-1043
-
Tidskriftsartikel (refereegranskat)abstract
- Observations based on overexpression of the suppressor gene p53 or interference with endogenous p53 support a role for p53 in mediating not only growth inhibition and apoptosis but also differentiation. The aim of this study was to characterize the mechanisms of p53-dependent differentiation in the monoblastic leukemia cell line U-937. These cells were transfected with a mutant of the p53 gene expressing wild-type p53 at a permissive temperature. The results showed that wild-type p53 and interferon (IFN)-gamma were able to work synergistically to promote differentiation. This cooperative response was not associated with early G1 arrest of the cell cycle, indicating that p53 can mediate differentiation by mechanisms other than those used for mediating G1 arrest. The differentiation response to transfected p53 with or without INF-gamma was inhibited by cyclic adenosine monophosphate (cAMP)-inducing agents (dibutyryl cyclic adenosine 3':5'-monophosphate, forskolin, and 3-isobutyl-1-methylxanthine) in a dose-dependent manner. In contrast, the differentiation response of p53-negative U-937 cells to 1,25-dihydroxychole-calciferol or all-trans retinoic acid was enhanced by cAMP-inducing agents at optimal concentrations and inhibited at higher concentrations. In addition, 1,25-dihydroxycholecalciferol-mediated differentiation could be achieved in cells arrested in G1 by concomitant incubation with cAMP-inducing agents, indicating that differentiation can occur in the absence of proliferation. In conclusion, the results of this study indicate that p53-dependent and -independent differentiation can occur independently of cell cycle regulation.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Johnsson, Markus, et al.
(författare)
-
Effect of PEO-PPO-PEO Triblock Copolymers on Structure and Stability of Phosphatidylcholine Liposomes
- 1999
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 15:19, s. 6314-6325
-
Tidskriftsartikel (refereegranskat)abstract
- The interactions of five poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) (PEO-PPO-PEO), Pluronic, copolymers and phosphatidylcholine liposomes of varying composition have been studied. Structural studies were performed by means of cryo-transmission electron microscopy (c-TEM) and reveal that inclusion of low amounts (similar to 2 mol %) of Pluronics gives rise to significant morphological changes of the liposome preparations. Pluronics with large poly(oxyethylene) (PEO) blocks, such as F127, F108, and F87, induce the formation of bilayer disks, whereas those with comparably short PEO blocks, P105 and P85, tend to to promote a reduction in the liposome size. Inclusion of cholesterol in the liposomal preparations reduces the incorporation of copolymers in the lipid bilayer and thus reduces, and in some cases even abolishes, the morphological changes observed in the absence of cholesterol. The effect of the copolymers on liposome permeability was also investigated. All investigated copolymers were found to increase the leakage of carboxyfluorescein from preformed liposomes. This was true also in the case of cholesterol-containing Liposomes despite the fact that no change in the liposome structure could be observed by means of c-TEM. The magnitude of the induced leakage was found to correlate well with the hydrophobicity, as measured by the cmc, of the respective Pluronic. By raising the temperature or decreasing the solvency of the copolymer in the solution, the effect of the copolymer on liposome leakage was found to increase significantly.
|
|
| 9. |
- Silvander, Mats, et al.
(författare)
-
Effects of PEG-lipids on permeability of phosphatidylcholine/cholesterol liposomes in buffer and in human serum
- 1998
-
Ingår i: Chemistry and Physics of Lipids. - 0009-3084 .- 1873-2941. ; 97:1, s. 15-26
-
Tidskriftsartikel (refereegranskat)abstract
- The permeability of liposomal membranes was studied as a function of the amount of incorporated PEG-lipid. The fluorescent dyes ethidium, propidium and 5(6)-carboxy fluorescein were used as markers for measurements of spontaneous leakage. The results show that addition of up to 8 mol% of PEG(2000)-DSPE into liposomal membranes of DSPC/Cho and EPC/Cho reduces the permeability of carboxyfluorescein in buffer solution. In contrast, the leakage of the more amphiphilic dye ethidium was not to any measurable extent affected by PEG-lipid inclusion. Another important difference was that ethidum leakage showed a clear dependence on temperature whereas leakage of carboxyfluorescein from pegylated liposomes did not. We conclude that the mechanisms by which the two dyes permeate the liposomal bilayer are qualitatively different. Both ethidium and carboxyfluorescein did interact with human serum components in a way that made measurements in serum unreliable. The more hydrophilic ethidium analogue propidium was shown not to interact with human serum components to any detectable extent. This made propidium suitable for permeability determinations in human serum. It was found that liposomes composed of pure EPC or EPC with 5 mol% DSPE-PEG, displayed a dramatic increase in permeability when subjected to a medium composed of 20% human serum in buffer. Addition of 40 mol% cholesterol to the EPC bilayers reduced the observed release rate in human serum substantially, whereas no stabilizing effect was observed upon PEG-lipid inclusion.
|
|
