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Induction of mitochondrial manganese superoxide dismutase confers resistance to apoptosis in acute myeloblastic leukaemia cells exposed to etoposide
Author(s) -
Mäntymaa Pentti,
Siitonen Timo,
Guttorm Tanja,
Säily Marjaana,
Kinnula Vuokko,
Savolainen EevaRiitta,
Koistinen Pirjo
Publication year - 2000
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.2000.01852.x
Subject(s) - etoposide , microbiology and biotechnology , apoptosis , programmed cell death , biology , mitochondrion , blot , annexin , superoxide dismutase , superoxide , cell culture , cytosol , cytochrome c , flow cytometry , biochemistry , oxidative stress , enzyme , genetics , chemotherapy , gene
We investigated the possible roles of mitochondrial manganese superoxide dismutase (MnSOD) and bcl‐2 in etoposide‐induced cell death in acute myeloblastic leukaemia (AML) using two subclones of the OCI/AML‐2 cell line, the etoposide‐sensitive (ES) and the etoposide‐resistant (ER), as models. Cell death after 24 h exposure to 10 μmol/l etoposide was about 60% and 70% in the ES subclone and about 20% and 25% in the ER subclone, when analysed by trypan blue and annexin V respectively. Cytochrome c efflux from mitochondria to cytosol was observed after 4 h of exposure in both subclones, whereas the activation of caspase‐3 was not detectable until after 12 h of exposure in the ES subclone and 24 h of exposure in the ER subclone, using Western blotting. The decrease in mitochondrial membrane potential, when analysed by the JC‐1 probe fluorocytometrically, also appeared to take place later in the ER than in the ES subclone. Both subclones showed evident basal expression of MnSOD and bcl‐2 by Western blotting. Etoposide caused a potent induction of MnSOD, more than 400% at 12 h, in the ER but not in the ES subclone. No significant change in bcl‐2 expression could be observed in either of the subclones during exposure to etoposide when analysed by Western blotting or flow cytometry. In conclusion, we suggest that MnSOD might have a special role in the protection of AML cells against etoposide‐induced cell death. Although unable to influence the cytochrome c efflux to cytosol, MnSOD might prevent the disruption of mitochondrial membrane potential, which evidently leads to cell death by releasing various activators of apoptosis.