title: Regulation of expression of BIK proapoptotic protein in human breast cancer cells: p53-dependent induction of BIK mRNA by fulvestrant and proteasomal degradation of BIK protein.
abstract: Induction of mRNA for BIK proapoptotic protein by doxorubicin or gamma-irradiation requires the DNA-binding transcription factor activity of p53. In MCF7 cells, pure antiestrogen fulvestrant also induces BIK mRNA and apoptosis. Here, we provide evidence that, in contrast to doxorubicin or gamma-irradiation, fulvestrant induction of BIK mRNA is not a direct effect of the transcriptional activity of p53, although p53 is necessary for this induction. It is known that p53 up-regulated modulator of apoptosis (PUMA) mRNA is induced directly by the transcriptional activity of p53. Whereas gamma-irradiation induced both BIK and PUMA mRNA, only BIK mRNA was induced by fulvestrant. Whereas both fulvestrant and doxorubicin induced BIK mRNA, only doxorubicin enhanced the DNA-binding activity of p53 and induced PUMA mRNA. Small interfering RNA (siRNA) suppression of p53 expression as well as overexpression of dominant-negative p53 effectively inhibited the fulvestrant induction of BIK mRNA, protein, and apoptosis. Transcriptional activity of a 2-kb BIK promoter, which contained an incomplete p53-binding sequence, was not affected by fulvestrant when tested by reporter assay. Fulvestrant neither affected the stability of the BIK mRNA transcripts. Interestingly, other human breast cancer cells, such as ZR75-1, constitutively expressed BIK mRNA even without fulvestrant. In these cells, however, BIK protein seemed to be rapidly degraded by proteasome, and siRNA suppression of BIK in ZR75-1 cells inhibited apoptosis induced by MG132 proteasome inhibitor. These results suggest that expression of BIK in human breast cancer cells is regulated at the mRNA level by a mechanism involving a nontranscriptional activity of p53 and by proteasomal degradation of BIK protein.
authors.affiliation: Department of Tumor Biology, Massachusetts General Hospital Center for Cancer Research, Charlestown, Massachusetts 02129, USA.
authors.forename: Jingyung
authors.initials: J
authors.lastname: Hur
authors.forename: Daphne W
authors.initials: DW
authors.lastname: Bell
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Dean
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Coser
authors.forename: Pablo C
authors.initials: PC
authors.lastname: Hilario
authors.forename: Ross A
authors.initials: RA
authors.lastname: Okimoto
authors.forename: Erica M
authors.initials: EM
authors.lastname: Tobey
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Smith
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Isselbacher
authors.forename: Toshi
authors.initials: T
authors.lastname: Shioda
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000235:genetics; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077267:Fulvestrant; D005720:Gamma Rays; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D024101:Mitochondrial Proteins; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011960:Receptors, Estrogen / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D000970:Antineoplastic Agents; D018931:Antineoplastic Agents, Hormonal; D051017:Apoptosis Regulatory Proteins; C096820:BIK protein, human; D007976:Leupeptins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D011960:Receptors, Estrogen; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D000077267:Fulvestrant; D004958:Estradiol; D004317:Doxorubicin; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde