title: Mechanisms of 2-methoxyestradiol-induced apoptosis and G2/M cell-cycle arrest of nasopharyngeal carcinoma cells.
abstract: 2-Methoxyestradiol (2ME2) is an endogenous metabolite of 17beta-estradiol (E(2)). This study aims to examine the anti-tumour activities of 2ME2 on the poorly differentiated HONE-1 NPC cell line. At the concentration of 1 microM, 2ME2 was found to induce a short-term reversible G2/M cell-cycle arrest. Further 10-fold increase to 10 microM, 2ME2 induced both irreversible G2/M phase cell-cycle arrest and apoptosis. Induction of apoptosis and G2/M cell-cycle arrest was due to oxidative stress as both apoptosis and the proportion of cells arresting at G2/M phase could be reduced by the superoxide dismutase (SOD) mimetic, TEMPO. Induction of apoptosis was accompanied with proteolytic cleavage of caspase-9 and -3, but not caspase-8. Kinetics studies revealed that 2ME2 induced a time-dependent inhibition of extracellular signal-regulated protein kinase (ERK) and an activation of c-jun N-terminal kinases (JNKs). The chemical inhibitor of JNKs, SP600125, was found to reduce 2ME2-induced apoptosis of the HONE-1 cells. Confocal microscopy revealed that the induction of G2/M cell-cycle arrest was associated with the presence of immunoreactivity of p-cdc2 (Tyr15) in the nucleus. The G2/M cell-cycle arrest is also correlated with an increased level of inactive p-cdc25C (Ser216) in 2ME2-treated HONE-1 cells. Results from this study indicate that production of superoxide anions might be involved in 2ME2-induced apoptosis and G2/M cell-cycle arrest of the HONE-1 cells.
authors.affiliation: Department of Biology, Hong Kong Baptist University, Hong Kong.
authors.forename: Yee-Man
authors.initials: YM
authors.lastname: Lee
authors.forename: Choi-Man
authors.initials: CM
authors.lastname: Ting
authors.forename: Yuen-Kit
authors.initials: YK
authors.lastname: Cheng
authors.forename: Tai-Ping
authors.initials: TP
authors.lastname: Fan
authors.forename: Ricky Ngok-Shun
authors.initials: RN
authors.lastname: Wong
authors.forename: Maria Li
authors.initials: ML
authors.lastname: Lung
authors.forename: Nai-Ki
authors.initials: NK
authors.lastname: Mak
mesh_terms: D000077584:2-Methoxyestradiol; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000473:pathology; D018384:Oxidative Stress; D013482:Superoxide Dismutase / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D004958:Estradiol; D000077584:2-Methoxyestradiol; D013482:Superoxide Dismutase; D048031:JNK Mitogen-Activated Protein Kinases