title: Tumor suppressor protein p53 promotes 2-methoxyestradiol-induced activation of Bak and Bax, leading to mitochondria-dependent apoptosis in human colon cancer HCT116 cells.
abstract: To examine the effect of tumor suppressor protein p53 on the antitumor activity of 2- methoxyestradiol (2-MeO-E2), 2-MeO-E2-induced cell cycle changes and apoptotic events were compared between the human colon carcinoma cell lines HCT116 (p53(+/+)) and HCT116 (p53(-/-)). When both cell types were exposed to 2-MeO-E2, a reduction in the cell viability and an enhancement in the proportions of G2/M cells and apoptotic sub-G1 cells commonly occurred dose-dependently. These 2-MeO-E2-induced cellular changes, except for G2/M arrest, appeared to be more apparent in the presence of p53. Immunofluorescence microscopic analysis using anti-α-tubulin and anti-lamin B2 antibodies revealed that after 2-MeO-E2 treatment, impaired mitotic spindle network and prometaphase arrest occurred similarly in both cell types. Following 2-MeO-E2 treatment, only HCT116 (p53(+/+)) cells exhibited an enhancement in the levels of p53, p-p53 (Ser-15), p21(WAF1/CIP1), and Bax; however, the Bak level remained relatively constant in both cell types, and the Bcl-2 level decreased only in HCT116 (p53(+/+)) cells. Additionally, mitochondrial apoptotic events, including the activation of Bak and Bax, loss of Δpsim, activation of caspase-9 and -3, and cleavage of lamin A/C, were more dominantly induced in the presence of p53. The Bak-specific and Bax-specific siRNA approaches confirmed the necessity of both Bak and Bax activations for the 2-MeO-E2-induced apoptosis in HCT116 cells. These results show that among 2-MeO-E2-induced apoptotic events, including prometaphase arrest, up-regulation of Bax level, down-regulation of Bcl-2 level, activation of both Bak and Bax, and mitochondria-dependent caspase activation, the modulation of Bax and Bcl-2 levels is the target of the pro-apoptotic action of p53.
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Su Bean
authors.initials: SB
authors.lastname: Jee
authors.forename: Won Young
authors.initials: WY
authors.lastname: Park
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Choi
authors.forename: Bokyung
authors.initials: B
authors.lastname: Kim
authors.forename: Yoon Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Do Youn
authors.initials: do Y
authors.lastname: Jun
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000077584:2-Methoxyestradiol; D017209:Apoptosis; D002453:Cell Cycle / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004958:Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism; D045325:HCT116 Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects*; D050257:Tubulin Modulators / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494772:BAK1 protein, human; C494826:BAX protein, human; D050257:Tubulin Modulators; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D004958:Estradiol; D000077584:2-Methoxyestradiol