Estradiol down regulates expression of vasoactive intestinal polypeptide receptor type-1 in breast cancer cell lines.
Three breast carcinoma cell lines were tested for 17beta-estradiol (E(2)) mediated regulation of vasoactive intestinal polypeptide receptor type-1 (VPAC(1)) expression. In all three, E(2) was found to down-regulate the mRNA level. We studied T47D cells in more details and found a 25 and 70% decrease in the VPAC(1) mRNA level upon 7 and 48 h of E(2) treatment, respectively. The number of vasoactive intestinal polypeptide (VIP) binding sites was reduced 66% upon treatment with E(2) for 72 h. After cycloheximide pretreatment, the E(2) mediated mRNA reduction was attenuated from 50% to 25% after 24 h suggesting the effect to be at least partly independent of protein synthesis. Experiments with the transcriptional inhibitor actinomycin D showed that E(2) did not influence the VPAC(1) mRNA half-life while nuclear run-on experiments indicated that E(2) decreased the VPAC(1) transcription rate. Two antiestrogens: ICI 182780 (ICI) and 4-hydroxy-tamoxifen (4-OHT) mediated a concentration dependent inhibition of E(2)'s effect on the mRNA level. Transient transfection with reporter-gene constructs containing various portions of the VPAC(1) 5'-flanking sequence revealed the most proximal 100 bp to be essential for the basal transcriptional activity. However, E(2) did not influence the expression of the reporter gene using up to 3250 bp of the VPAC(1) 5'-flariking region.
Madsen
B
B
Department of Clinical Biochemistry, Bispebjerg Hospital, University of Copenhagen NV, Bispebjerg Bakke 23, Dk-2400, Copenhagen, Denmark.
Georg
B
B
Madsen
M W
MW
Fahrenkrug
J
J
D020121:5' Untranslated Regions / Q000235:genetics; D001667:Binding, Competitive / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000494:pharmacology; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000502:physiology; D018005:Receptors, Vasoactive Intestinal Peptide / Q000235:genetics* / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D014407:Tumor Cells, Cultured / Q000187:drug effects
D020121:5' Untranslated Regions; D004965:Estrogen Antagonists; D012333:RNA, Messenger; D018005:Receptors, Vasoactive Intestinal Peptide; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D004958:Estradiol