Downregulation of c-Myc determines sensitivity to 2-methoxyestradiol-induced apoptosis in human acute myeloid leukemia.
OBJECTIVE
2-Methoxyestradiol (2ME2) has been shown to induce apoptosis in leukemic cells, but its exact mechanism remains unclear. Because c-Myc plays a critical role in leukemogenesis, we evaluated whether 2ME2 acts on acute myeloid leukemia (AML) through modulation of c-Myc activity.


METHODS
AML cell lines and primary AML leukemia were treated with 2ME2 and the relationship between 2ME2-induced apoptosis and changes in c-Myc activity was examined.


RESULTS
2ME2 induced mitochondrial apoptosis of human AML cells through increased reactive oxygen species. Further investigation showed that 2ME2 downregulated c-Myc expression in a time-dependent manner. Increased oxidative stress led to downregulation of c-Myc mRNA and protein, but did not affect the stability of c-Myc protein. To demonstrate the role of c-Myc in 2ME2-induced apoptosis, we ectopically expressed wild-type c-Myc in AML cells and found that ectopic expression of c-Myc abrogated the 2ME2-induced apoptosis. In addition, we showed that 2ME2 treatment inhibited phosphorylation of Akt and binding of nuclear factor-kappaB p65/p50 heterodimers to its DNA targets. As with results from cell lines studied, 2ME2 also induced cytotoxicity to primary AML cells and downregulated their c-Myc expression and induced apoptosis.


CONCLUSIONS
Downregulation of c-Myc is critical for 2ME2-induced oxidative stress and apoptosis in AML cells. Our results might be extended to other types of cancers overexpressing c-Myc.
Chow
Jyh-Ming
JM
Department of Internal Medicine, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan.
Liu
Chien-Ru
CR
Lin
Che-Pin
CP
Lee
Chun-Nin
CN
Cheng
Yun-Chih
YC
Lin
Shufan
S
Liu
H Eugene
HE
D000077584:2-Methoxyestradiol; D017209:Apoptosis / Q000187:drug effects*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology*; D020298:U937 Cells
C489427:MYC protein, human; D052002:NF-kappa B p50 Subunit; D016271:Proto-Oncogene Proteins c-myc; D017382:Reactive Oxygen Species; D051996:Transcription Factor RelA; D050257:Tubulin Modulators; D004958:Estradiol; D000077584:2-Methoxyestradiol; D051057:Proto-Oncogene Proteins c-akt