Abstract
Etoposide is a potent anticancer agent that is used to treat various tumors. We have investigated the dose-dependent effect of etoposide on apoptosis using chronic myeloid leukemia K562 cells treated with low (5 microM) or high (100 microM) concentrations of the drug. At a low concentration, etoposide induced little apoptosis at 24 h, while about 20% of the cells showed apoptosis morphologically at a high concentration. Processing of caspase-3 was slightly detected from 12 h and became obvious at 24 h with 100 microM etoposide. Caspase-3-like protease activity was detected at 24 h with a high concentration. Moreover, these changes were accompanied by cleavage of poly ADP ribose polymerase (PARP). Changes of the mRNA levels of most apoptosis-regulating genes were not prominent at both concentrations, except for the rapid induction of c-IAP-2/HIAP-1 and the down-regulation of Bcl-X(L) by 100 microM etoposide. The downregulation of Bcl-X(L) protein occurred from 6 h, while Bax protein conversely showed a slight increase from 6 h. Taken together, the present findings show that the dose-dependent apoptotic effect of etoposide is based on a change in the balance between Bcl-X(L) and Bax, which precedes the activation of caspase-3.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Antineoplastic Agents, Phytogenic / pharmacology*
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Apoptosis / drug effects
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Caspase 3
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Caspases / metabolism
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DNA Damage / drug effects
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DNA Primers / chemistry
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DNA, Neoplasm / drug effects
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Dose-Response Relationship, Drug
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Down-Regulation
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Etoposide / pharmacology*
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Gene Expression Regulation
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Genes, bcl-2 / drug effects*
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Humans
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Immunoblotting
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K562 Cells / drug effects*
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K562 Cells / metabolism
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / genetics
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / metabolism
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Microscopy, Fluorescence
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases
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Proteins / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism*
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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bcl-2-Associated X Protein
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bcl-X Protein
Substances
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Antineoplastic Agents, Phytogenic
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BAX protein, human
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BCL2L1 protein, human
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DNA Primers
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DNA, Neoplasm
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Proteins
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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RNA, Messenger
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bcl-2-Associated X Protein
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bcl-X Protein
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Etoposide
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PARP1 protein, human
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Poly (ADP-Ribose) Polymerase-1
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Poly(ADP-ribose) Polymerases
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CASP3 protein, human
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Caspase 3
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Caspases