title: Arsenic induces functional re-expression of estrogen receptor α by demethylation of DNA in estrogen receptor-negative human breast cancer.
abstract: Estrogen receptor α (ERα) is a marker predictive for response of breast cancers to endocrine therapy. About 30% of breast cancers, however, are hormone- independent because of lack of ERα expression. New strategies are needed for re-expression of ERα and sensitization of ER-negative breast cancer cells to selective ER modulators. The present report shows that arsenic trioxide induces reactivated ERα, providing a target for therapy with ER antagonists. Exposure of ER-negative breast cancer cells to arsenic trioxide leads to re-expression of ERα mRNA and functional ERα protein in in vitro and in vivo. Luciferase reporter gene assays and 3-(4,5-dimethylthiazol-2-yl)- 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays show that, upon exposure to arsenic trioxide, formerly unresponsive, ER-negative MDA-MB-231 breast cancer cells become responsive to ER antagonists, 4-hydroxytamoxifen and ICI 182,780. Furthermore, methylation- specific PCR and bisulfite-sequencing PCR assays show that arsenic trioxide induces partial demethylation of the ERα promoter. A methyl donor, S-adenosylmethionine (SAM), reduces the degree of arsenic trioxide-induced re-expression of ERα and demethylation. Moreover, Western blot and ChIP assays show that arsenic trioxide represses expression of DNMT1 and DNMT3a along with partial dissociation of DNMT1 from the ERα promoter. Thus, arsenic trioxide exhibits a previously undefined function which induces re-expression ERα in ER-negative breast cancer cells through demethylation of the ERα promoter. These findings could provide important information regarding the application of therapeutic agents targeting epigenetic changes in breast cancers and potential implication of arsenic trioxide as a new drug for the treatment of ER-negative human breast cancer.
authors.affiliation: Key Laboratory of Modern Toxicology, Ministry of Education, School of Public Health, Nanjing Medical University, Nanjing, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Nannan
authors.initials: N
authors.lastname: Zhou
authors.forename: Hongxia
authors.initials: H
authors.lastname: Liu
authors.forename: Fei
authors.initials: F
authors.lastname: Jiang
authors.forename: Yubang
authors.initials: Y
authors.lastname: Wang
authors.forename: Chunyan
authors.initials: C
authors.lastname: Hu
authors.forename: Hong
authors.initials: H
authors.lastname: Qi
authors.forename: Caiyun
authors.initials: C
authors.lastname: Zhong
authors.forename: Xinru
authors.initials: X
authors.lastname: Wang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
mesh_terms: D000818:Animals; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D047628:Estrogen Receptor alpha / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010087:Oxides / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D001152:Arsenicals; D004268:DNA-Binding Proteins; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; C489325:MBD2 protein, human; D009363:Neoplasm Proteins; D010087:Oxides; D012333:RNA, Messenger; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; D000077237:Arsenic Trioxide