title: Tamoxifen-induced apoptosis in breast cancer cells relates to down-regulation of bcl-2, but not bax and bcl-X(L), without alteration of p53 protein levels.
abstract: Tamoxifen (TAM) has been shown to induce apoptosis in breast cancer cells. bcl-2 family genes, which can interact with each other, have been shown to interfere with apoptosis after various stimuli. In this study, we investigated the effects of TAM on bcl-2 family gene products bcl-2, bax, and bcl-X(L) and on p53 levels in estrogen receptor-positive MCF-7 breast cancer cells. We found that TAM induced time- and concentration-dependent down-regulation of bcl-2 at both the mRNA and protein level. Down-regulation of bcl-2 correlated with TAM-induced apoptosis. In addition, estradiol treatment significantly increased bcl-2 protein expression and blocked the reduction of bcl-2 by TAM. TAM did not, however, affect bax, bcl-X(L), or p53 expression at the mRNA or protein level. Our results demonstrate that TAM can induce apoptosis in a time- and dose-dependent manner by modulating bcl-2 levels in breast cancer cells, and down-regulation of bcl-2 induced by TAM was not accompanied by alterations in p53 levels.
authors.affiliation: Department of Surgery II, Fukushima Medical University School of Medicine, Japan. zhang@cc.fmu.ac.jp
authors.forename: G J
authors.initials: GJ
authors.lastname: Zhang
authors.forename: I
authors.initials: I
authors.lastname: Kimijima
authors.forename: M
authors.initials: M
authors.lastname: Onda
authors.forename: M
authors.initials: M
authors.lastname: Kanno
authors.forename: H
authors.initials: H
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: A
authors.initials: A
authors.lastname: Tsuchiya
authors.forename: R
authors.initials: R
authors.lastname: Abe
authors.forename: S
authors.initials: S
authors.lastname: Takenoshita
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005260:Female; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D013629:Tamoxifen / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D018931:Antineoplastic Agents, Hormonal; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D013629:Tamoxifen