Bcl-2 protects murine erythroleukemia cells from p53-dependent and -independent radiation-induced cell death.
To better understand the molecular basis of radiation-induced cell death, we studied the role of the bcl-2 oncogene and the p53 tumor suppressor gene in this process. A temperature-sensitive mutant of murine p53 (p53Val-135) and/or bcl-2 was transfected into murine erythroleukemia cells (MEL, DP16-1, which are null in p53). We demonstrate that radiation-induced cell death occurs by both p53-dependent and -independent pathways and overexpression of bcl-2 modulates both pathways. When viability was measured 24 h post-radiation, cells that had been briefly exposed to wtp53 immediately after X-ray irradiation had decreased survival as compared to unirradiated cells expressing wtp53 or X-ray irradiated DP16-1 cells. However, at later times X-ray irradiated parental DP16-1 cells also had decreased survival compared to the unirradiated control. This decrease in survival began 48 h following radiation. Bcl-2 prevented radiation-induced cell death in DP16-1 cells expressing wtp53 and delayed radiation-induced cell death in DP16-1 cells without wtp53. X-ray irradiated cells expressing wtp53 displayed microscopic and biochemical characteristics consistent with cell death due to apoptosis. DP16-1 cells which were untransfected or co-transfected with wtp53 and bcl-2 displayed characteristics of cells undergoing necrosis. These results suggest that radiation-induced cell death occurs by both p53-dependent and p53-independent pathways. The p53-dependent pathway results in cell death via apoptosis and occurs approximately 24 h following radiation. The p53-independent pathway does not appear to involve apoptosis and occurs at a later time, starting 48 h after X-ray exposure. Thus, bcl-2 protects cells from p53-dependent radiation-induced apoptotic cell death and attenuates p53-independent radiation-induced cell death.
Fukunaga-Johnson
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N
Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor 48109, USA.
Ryan
J J
JJ
Wicha
M
M
Nuñez
G
G
Clarke
M F
MF
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D002478:Cells, Cultured; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology; D051379:Mice; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D014964:X-Ray Therapy
D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53