title: Complex agonist-like properties of ICI 182,780 (Faslodex) in human breast cancer cells that predominantly express progesterone receptor-B: implications for treatment resistance.
abstract: ICI 182,780 (Faslodex), considered a pure anti-estrogen, is approved for treatment of post-menopausal breast cancer patients who fail to respond to tamoxifen therapy. We recently reported that, like mifepristone, ICI 182,780 exhibits anti-progestin activity, blocking the progestin-dependent increase in endogenous vascular endothelial growth factor (VEGF) mRNA and protein release. Some anti-progestins have partial agonist-like activity in breast cancer cells expressing high levels of progesterone receptor B (PRB). Our results show that ICI 182,780 can also induce reporter activity from a plasmid containing a simple progestin responsive element (PRE) in these cells. Using small interfering RNA, we determined that induction is dependent on the presence of PR, estrogen receptor and SRC-1. Regulation of more complex progestin-responsive promoters was context-dependent; induction was observed from the MMTV promoter but not from the VEGF promoter. In contrast, ICI 182,780 increased the release of angiogenically active VEGF from cells expressing elevated levels of PRB. This effect was dependent on the phosphatidylinositol-3 kinase and ERK/MAPK signaling pathways. We hypothesize that these agonist-like properties of ICI 182,780 (one genomic and one non-genomic) may contribute to the acquisition of drug resistance, suggesting that both anti-hormonal and anti-angiogenic treatment may be appropriate in these patients.
authors.affiliation: Dalton Cardiovascular Research Center and Biomedical Sciences, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wu
authors.forename: Yayun
authors.initials: Y
authors.lastname: Liang
authors.forename: Zafar
authors.initials: Z
authors.lastname: Nawaz
authors.forename: Salman M
authors.initials: SM
authors.lastname: Hyder
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D000077267:Fulvestrant; D015870:Gene Expression / Q000187:drug effects; D051548:Histone Acetyltransferases; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D015735:Mifepristone / Q000494:pharmacology; D056920:Nuclear Receptor Coactivator 1; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D000906:Antibodies; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D011980:Receptors, Progesterone; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C101118:progesterone receptor A; C097314:progesterone receptor B; D000077267:Fulvestrant; D015735:Mifepristone; D011374:Progesterone; D004958:Estradiol; D008156:Luciferases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases