Abstract
Apoptosis is a cellular death process involving the sequential activation of a series of caspases, endonucleases, and other enzymes. The initiation of apoptosis can be inhibited by overexpression of bcl-2 and certain other members of a related family of proteins. We examined the effects of bcl-2 overexpression on the apoptotic response to photodynamic therapy (PDT), using aluminum phthalocyanine as the photosensitizing agent. In this study, we compared the immortalized human breast epithelial cell line MCF10A with a subline (MCF10A/bcl-2) transfected with the human bcl-2 gene. The latter was approximately 2-fold more sensitive to the phototoxic effects of PDT. At a 50 mJ/cm2 light dose, photodamage to MCF-10A/bcl-2 resulted in a greater loss of the mitochondrial membrane potential (delta(psi)m), enhanced release of mitochondrial cytochrome c, a more rapid and greater activation of caspase-3, and a greater apoptotic response. Western blot analysis revealed that the transfected cell line showed overexpression of both bcl-2 and bax, and that PDT caused selective destruction of bcl-2, leaving bax unaffected. The greater apoptotic response by the transfected line is, therefore, attributed to the higher bax:bcl-2 ratio after photodamage.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Apoptosis / drug effects*
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Apoptosis / radiation effects
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Breast / pathology
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Caspase 3
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Caspases / analysis
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Cell Line, Transformed / drug effects
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Cell Line, Transformed / radiation effects
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Cytochrome c Group / analysis
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Cytomegalovirus / genetics
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Epithelial Cells / drug effects
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Epithelial Cells / radiation effects
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Female
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Fibrocystic Breast Disease / pathology
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Gene Expression Regulation, Neoplastic / drug effects
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Gene Expression Regulation, Neoplastic / radiation effects
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Genes, bcl-2*
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Humans
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Indoles / pharmacology
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Light
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Mitochondria / drug effects
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Mitochondria / enzymology
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Mitochondria / radiation effects
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Organometallic Compounds / pharmacology
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Photochemotherapy*
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Promoter Regions, Genetic
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Proto-Oncogene Proteins / biosynthesis
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Proto-Oncogene Proteins c-bcl-2 / biosynthesis
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Radiation-Sensitizing Agents / pharmacology
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Recombinant Fusion Proteins / biosynthesis
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Recombinant Fusion Proteins / genetics
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Transfection
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bcl-2-Associated X Protein
Substances
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BAX protein, human
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Cytochrome c Group
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Indoles
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Organometallic Compounds
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Radiation-Sensitizing Agents
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Recombinant Fusion Proteins
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bcl-2-Associated X Protein
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aluminum phthalocyanine
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CASP3 protein, human
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Caspase 3
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Caspases