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Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells.
The kinetics of dexamethasone-induced death of CCRF CEM clone C7A human lymphoblastic leukaemia cells was determined with respect to changes in the expression of the c-myc protein. Cell death was characterised as being by apoptosis: cells with an intact plasma membrane had condensed chromatin and we...
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Formato: | Texto |
Lenguaje: | English |
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Nature Publishing Group
1994
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1968827/ https://www.ncbi.nlm.nih.gov/pubmed/8142255 |
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author | Wood, A. C. Waters, C. M. Garner, A. Hickman, J. A. |
author_facet | Wood, A. C. Waters, C. M. Garner, A. Hickman, J. A. |
author_sort | Wood, A. C. |
collection | PubMed |
description | The kinetics of dexamethasone-induced death of CCRF CEM clone C7A human lymphoblastic leukaemia cells was determined with respect to changes in the expression of the c-myc protein. Cell death was characterised as being by apoptosis: cells with an intact plasma membrane had condensed chromatin and were characterised as having approximately 300 kbp fragments when DNA integrity was analysed by pulsed-field electrophoresis. Onset of apoptosis required a minimum of 36 h exposure to 5 microM dexamethasone; before this time no apoptotic cells were observed. This 36 h incubation period appeared to be necessary to prime the cells for subsequent death by apoptosis. In the continued presence of dexamethasone the percentage of apoptotic cells increased to 60% apoptotic cells by 54 h. Investigation of changes in c-myc protein showed that it was undetectable after 12 h of incubation with dexamethasone, although cells were not committed to die at this time. Cells were treated with dexamethasone for 54 h and for various pulsed periods with a non-toxic concentration of cycloheximide (200 nM). When cycloheximide was present during the first 36 h priming period of dexamethasone treatment, there was an immediate loss of c-myc protein and apoptosis at 54 h was completely inhibited. In contrast, there was no inhibition of apoptosis when dexamethasone-treated cells were incubated with an 18 h pulse of cycloheximide added after 36 h. Cells exposed to dexamethasone for 36 h ('primed') were given various periods of dexamethasone-free incubation before readdition of dexamethasone for a further 18 h. The longer the cells were free of drug after priming, the less susceptible they became to apoptosis, suggesting a slow decay of their 'memory' of the initial 36 h period of exposure. Cycloheximide inhibited the decay of this memory. Removal of dexamethasone after a 36 h exposure was characterised by a subsequent 24 h suppression of c-myc protein expression. Despite this, 90% of cells became refractory to apoptosis before the reappearance of c-myc protein. The evidence does not support the hypothesis that changes in c-myc expression are required for the engagement of apoptosis of CEM cells. IMAGES: |
format | Text |
id | pubmed-1968827 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1994 |
publisher | Nature Publishing Group |
record_format | MEDLINE/PubMed |
spelling | pubmed-19688272009-09-10 Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. Wood, A. C. Waters, C. M. Garner, A. Hickman, J. A. Br J Cancer Research Article The kinetics of dexamethasone-induced death of CCRF CEM clone C7A human lymphoblastic leukaemia cells was determined with respect to changes in the expression of the c-myc protein. Cell death was characterised as being by apoptosis: cells with an intact plasma membrane had condensed chromatin and were characterised as having approximately 300 kbp fragments when DNA integrity was analysed by pulsed-field electrophoresis. Onset of apoptosis required a minimum of 36 h exposure to 5 microM dexamethasone; before this time no apoptotic cells were observed. This 36 h incubation period appeared to be necessary to prime the cells for subsequent death by apoptosis. In the continued presence of dexamethasone the percentage of apoptotic cells increased to 60% apoptotic cells by 54 h. Investigation of changes in c-myc protein showed that it was undetectable after 12 h of incubation with dexamethasone, although cells were not committed to die at this time. Cells were treated with dexamethasone for 54 h and for various pulsed periods with a non-toxic concentration of cycloheximide (200 nM). When cycloheximide was present during the first 36 h priming period of dexamethasone treatment, there was an immediate loss of c-myc protein and apoptosis at 54 h was completely inhibited. In contrast, there was no inhibition of apoptosis when dexamethasone-treated cells were incubated with an 18 h pulse of cycloheximide added after 36 h. Cells exposed to dexamethasone for 36 h ('primed') were given various periods of dexamethasone-free incubation before readdition of dexamethasone for a further 18 h. The longer the cells were free of drug after priming, the less susceptible they became to apoptosis, suggesting a slow decay of their 'memory' of the initial 36 h period of exposure. Cycloheximide inhibited the decay of this memory. Removal of dexamethasone after a 36 h exposure was characterised by a subsequent 24 h suppression of c-myc protein expression. Despite this, 90% of cells became refractory to apoptosis before the reappearance of c-myc protein. The evidence does not support the hypothesis that changes in c-myc expression are required for the engagement of apoptosis of CEM cells. IMAGES: Nature Publishing Group 1994-04 /pmc/articles/PMC1968827/ /pubmed/8142255 Text en https://creativecommons.org/licenses/by/4.0/This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/. |
spellingShingle | Research Article Wood, A. C. Waters, C. M. Garner, A. Hickman, J. A. Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title | Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title_full | Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title_fullStr | Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title_full_unstemmed | Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title_short | Changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
title_sort | changes in c-myc expression and the kinetics of dexamethasone-induced programmed cell death (apoptosis) in human lymphoid leukaemia cells. |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1968827/ https://www.ncbi.nlm.nih.gov/pubmed/8142255 |
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