Differential responses of Bcl-2 family genes to etoposide in chronic myeloid leukemia K562 cells.
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.
Fukumi
S
S
Department of Oncology, Institute of DNA Medicine, The Jikei University School of Medicine, Tokyo, Japan.
Horiguchi-Yamada
J
J
Nakada
S
S
Nagai
M
M
Ohno
T
T
Yamada
H
H
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D017931:DNA Primers / Q000737:chemistry; D004273:DNA, Neoplasm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005047:Etoposide / Q000494:pharmacology*; D005786:Gene Expression Regulation; D019254:Genes, bcl-2 / Q000187:drug effects*; D006801:Humans; D015151:Immunoblotting; D020014:K562 Cells / Q000187:drug effects* / Q000378:metabolism; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D000972:Antineoplastic Agents, Phytogenic; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D017931:DNA Primers; D004273:DNA, Neoplasm; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D005047:Etoposide; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases