title: Susceptibility to drug-induced apoptosis correlates with differential modulation of Bad, Bcl-2 and Bcl-xL protein levels.
abstract: To define the responses of apoptotic regulatory proteins to different chemotherapeutic agents, we investigated the expression of Bcl-2 family gene products, the release of cytochrome c, and the activation of pro-caspase-3 during apoptosis induced by Taxol and Thiotepa, in the MCF-7 breast carcinoma and the HL-60 leukemia cell lines. The earliest event induced by drug exposure was increase in Bad protein levels, followed by Bcl-2 down-regulation, cytochrome c release, and Bcl-xL and Bax up-regulation. Bak accumulation was a late event. Activation of pro-caspase-3 and cleavage of Bcl-2 protein occurred in the HL-60 cells only, and followed the cytochrome c release. The overall responses were qualitatively similar in both cell types, but MCF-7 cells treated with Taxol showed a significant delay in apoptosis, correlating with early up-regulation of Bcl-2 and delayed release of cytochrome c. We conclude that Bad up-regulation is an early indicator of a cellular response that will lead to cell death, but may be modulated by survival mechanisms, which cumulatively govern the ultimate susceptibility to apoptosis.
authors.affiliation: Science Applications International Corporation, National Cancer Institute, Frederick Cancer Resource and Development Center, Frederick, P.O. Box B, Maryland, MD 21702, USA. tudor@dtpax2.ncifcrf.gov
authors.forename: G
authors.initials: G
authors.lastname: Tudor
authors.forename: A
authors.initials: A
authors.lastname: Aguilera
authors.forename: D O
authors.initials: DO
authors.lastname: Halverson
authors.forename: N D
authors.initials: ND
authors.lastname: Laing
authors.forename: E A
authors.initials: EA
authors.lastname: Sausville
mesh_terms: D048948:14-3-3 Proteins; D017209:Apoptosis / Q000187:drug effects*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000235:genetics; D002470:Cell Survival / Q000187:drug effects; D003574:Cytochrome c Group / Q000378:metabolism; D004792:Enzyme Precursors / Q000235:genetics; D015870:Gene Expression; D018922:HL-60 Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D017239:Paclitaxel / Q000494:pharmacology*; D011506:Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D013852:Thiotepa / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D014446:Tyrosine 3-Monooxygenase; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
chemical_list: D048948:14-3-3 Proteins; C494819:BAD protein, human; C494772:BAK1 protein, human; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; D003574:Cytochrome c Group; D004792:Enzyme Precursors; D008565:Membrane Proteins; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D013852:Thiotepa; D014446:Tyrosine 3-Monooxygenase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D017239:Paclitaxel