Enhanced apoptotic response to photodynamic therapy after bcl-2 transfection.
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.
Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D001940:Breast / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D002461:Cell Line, Transformed / Q000187:drug effects / Q000528:radiation effects; D003574:Cytochrome c Group / Q000032:analysis; D003587:Cytomegalovirus / Q000235:genetics; D004847:Epithelial Cells / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D005348:Fibrocystic Breast Disease / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D019254:Genes, bcl-2; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008027:Light; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D009942:Organometallic Compounds / Q000494:pharmacology; D010778:Photochemotherapy; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D003574:Cytochrome c Group; D007211:Indoles; D009942:Organometallic Compounds; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011838:Radiation-Sensitizing Agents; D011993:Recombinant Fusion Proteins; D051028:bcl-2-Associated X Protein; C060570:aluminum phthalocyanine; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases