title: The histone deacetylase inhibitor trichostatin A sensitizes estrogen receptor alpha-negative breast cancer cells to tamoxifen.
abstract: Many cases of breast cancer show loss of estrogen receptor (ER) alpha expression, which leads to unresponsiveness to antihormonal treatment even though there is no loss of the structurally and biochemically similar ER beta. ER activity is positively and negatively regulated by transcriptional regulators such as histone deacetylase (HDAC), which is known to be a negative ER regulator. Here, we evaluated using ER beta as an alternative target for tamoxifen therapy by treating ER alpha-negative, beta-positive breast cancer cells with the HDAC inhibitor trichostatin A (TSA), and testing whether tamoxifen responsiveness increased following upregulation of ER beta. TSA enhanced the overall ER transcriptional activity in these cells, as visualized by estrogen response element-regulated reporter and the expression of progesterone receptor, a known ER target, without ER alpha restoration. Additionally, TSA induced the expression and nuclear translocation of ER beta but not alpha, suggesting that these actions leading to increase of ER transcriptional activity are mediated through ER beta rather than alpha. Furthermore, following treatment with TSA, the formerly unresponsive MDA-MB-231 and Hs578T breast cancer cells became responsive to tamoxifen. However, reduction of ER beta expression by short interfering RNA abrogated this TSA-induced sensitization effect in these cells. Together, these results show that the HDAC inhibitor TSA sensitized ER alpha-negative, antihormone-unresponsive breast cancer cells to tamoxifen treatment possibly by upregulating ER beta activity.
authors.affiliation: Research Institute and Hospital, National Cancer Center, 411-764, Republic of Korea.
authors.forename: Eun Ryoung
authors.initials: ER
authors.lastname: Jang
authors.forename: Soo-Jeong
authors.initials: SJ
authors.lastname: Lim
authors.forename: Eun Sook
authors.initials: ES
authors.lastname: Lee
authors.forename: Gajin
authors.initials: G
authors.lastname: Jeong
authors.forename: Tae-You
authors.initials: TY
authors.lastname: Kim
authors.forename: Yung-Jue
authors.initials: YJ
authors.lastname: Bang
authors.forename: Jong-Soo
authors.initials: JS
authors.lastname: Lee
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D004965:Estrogen Antagonists / Q000494:pharmacology / Q000627:therapeutic use; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006367:HeLa Cells; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000172:deficiency* / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D013629:Tamoxifen / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D013629:Tamoxifen; C012589:trichostatin A; D006655:Histone Deacetylases