SV40 T/t-antigens sensitize mammary gland epithelial cells to oxidative stress and apoptosis.
As shown recently, the SV40 T/t-antigens (T/t-ag) exert a strong apoptotic activity in mouse mammary gland epithelial cells (ME-cells) leading to premature gland involution at late pregnancy. This high spontaneous cell death rate (20%) is also maintained in T/t-ag positive ME-tissue culture cell lines (e.g., 8/61-A), but not in those ME-cells that have switched off the SV40 T/t-transgene expression. In this study, we demonstrate for the first time that the T/t-ag sensitize ME-cells to oxidative stress leading to apoptosis. Treatment of the 8/61-A ME-cells with catalase, a scavenger of H2O2, completely blocked spontaneous cell death, which was linked to downregulation of caspase-3 activity. Furthermore, exposure of the cells to low concentrations of H2O2 highly increased the apoptosis rate. These findings suggest that the T/t-ag positive ME-cells contain either elevated levels of reactive oxygen species or reduced antioxidant activities. During spontaneous and H2O2-induced apoptosis, the activity of caspase-3 is significantly increased. In addition, the 8/61-A cells accumulated p21 and Bax proteins while the level of the anti-apoptotic protein Bcl-2 decreased implying a posttranscriptional regulation of apoptosis.
Kohlhoff
S
S
Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Berlin, Germany.
Ziechmann
C
C
Gottlob
K
K
Graessmann
M
M
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002374:Catalase / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018384:Oxidative Stress / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein
D000952:Antigens, Polyomavirus Transforming; D000975:Antioxidants; C494827:Bax protein, mouse; D061945:Caspase Inhibitors; D016166:Free Radical Scavengers; D005609:Free Radicals; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D006861:Hydrogen Peroxide; D002374:Catalase; D005982:Glutathione Transferase; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases