Mechanism of 2-methoxyestradiol-induced apoptosis and growth arrest in human breast cancer cells.
2-Methoxyestradiol, a well-known nonpolar endogenous metabolite of 17beta-estradiol, has been shown to selectively induce apoptosis in a number of cancer cell lines, but not in normal cells. The mechanism of 2-methoxyestradiol-induced apoptosis appears to vary considerably in different cell lines examined. In the present study, we systematically analyzed the mechanisms of 2-methoxyestradiol-induced apoptosis in the estrogen receptor-negative MDA-MB-435s human breast cancer cells. We found that 2-methoxyestradiol induced the activation of JNK, ERK, and p38 MAPKs. 2-methoxyestradiol-induced JNK activation was associated with the induction of apoptosis through the mitochondrial pathways as a result of increased phosphorylation (inactivation) of the anti-apoptotic Bcl-2 and Bcl-xL proteins. In comparison, 2-methoxyestradiol-induced activation of ERK and p38 in these cells was found to have a protective effect against 2-MeO-E(2)-induced apoptosis. Consistent with this observation, the presence of pharmacological inhibitor of ERK or p38 enhanced 2-methoxyestradiol-induced apoptosis. Mechanistically, inhibition of ERK and p38 activity was associated with activation of various caspases and PARP cleavage, and it also stabilized the pro-apoptotic proteins Bax and Bim, thereby preventing them from degradation during 2-methoxyestradiol treatment. These results suggest that ERK and p38 MAPKs may serve as viable targets for the sensitization of human breast cancer cells to 2-methoxyestradiol-induced apoptosis.
Department of Pharmacology, Toxicology and Therapeutics, School of Medicine, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Masayuki
M
Fukui
Bao Ting
BT
Zhu
D000077584:2-Methoxyestradiol; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005260:Female; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D050257:Tubulin Modulators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D052246:Cyclooxygenase 2 Inhibitors; D050257:Tubulin Modulators; D004958:Estradiol; D000077584:2-Methoxyestradiol; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases