title: Ligand- and cell-specific effects of signal transduction pathway inhibitors on progestin-induced vascular endothelial growth factor levels in human breast cancer cells.
abstract: We evaluated the signaling pathways involved in regulating vascular endothelial growth factor (VEGF), a potent angiogenic growth factor, in response to natural and synthetic progestins in breast cancer cells. Inhibition of the phosphoinositide-3'-kinase (PI3-kinase) signaling pathway or the specificity protein-1 (SP-1) transcription factor abolished both progesterone- and medroxyprogesterone acetate (MPA)-induced VEGF secretion from BT-474 and T47-DCO)cells. Inhibitors of the MAPK kinase 1/2/MAPK and N-terminal jun kinase/MAPK signaling pathways blocked both progesterone- and MPA-induced VEGF secretion in BT-474 cells. However, these inhibitors blocked only progesterone-, but not MPA-induced VEGF secretion in T47-DCO cells. Inhibitors of PI3-kinase or SP-1 blocked both progesterone- and MPA-induced increases in VEGF mRNA levels in T47-DCO cells. The proximal SP-1 sites within the VEGF promoter were critical for progestin-dependent induction of VEGF. In contrast, MAPK inhibitors did not block the progesterone- or MPA-induced increases in VEGF mRNA in T47-DCO cells, suggesting that MAPK inhibitors decreased progesterone-induced VEGF secretion in T47-DCO cells by blocking posttranscriptional mechanisms. The MAPK kinase/ERK/MAPK-independent induction of VEGF mediated by MPA was associated with the PRB [progesterone receptor (PR) B] isoform of the PR in T47-DCO cells. None of the inhibitors tested reduced basal PR levels or abrogated PR-dependent gene expression from a reporter plasmid, indicating that loss of PR function cannot explain any of the observed effects. Because the PI3-kinase signaling pathway and SP-1 transcription factor play critical roles in progestin-dependent VEGF induction, these may be useful targets for developing antiangiogenic therapies to prevent progression of progestin-dependent human breast cancers.
authors.affiliation: Dalton Cardiovascular Research Center and the Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wu
authors.forename: Sandra
authors.initials: S
authors.lastname: Brandt
authors.forename: Salman M
authors.initials: SM
authors.lastname: Hyder
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D001483:Base Sequence; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D011372:Progestins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004791:Enzyme Inhibitors; D008024:Ligands; D011372:Progestins; D020033:Protein Isoforms; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D011374:Progesterone; D017258:Medroxyprogesterone Acetate; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases