title: A truncated-Flt1 isoform of breast cancer cells is upregulated by Notch and downregulated by retinoic acid.
abstract: We have previously reported that the major isoform of Flt1/VEGFR-1 expressed in MDA-MB-231 breast cancer cells was a truncated intracellular isoform transcribed from intron 21 (i21 Flt1). This isoform upregulated the active form of Src and increased breast cancer cell invasiveness. Since expression of the transmembrane and soluble Flt1 isoforms of HUVEC is activated by Notch signaling, we wondered whether the expression of the intracellular isoform i21 Flt1 was also dependent on Notch activation. We report here that the expression of i21 Flt1 in HUVEC and MDA-MB-231 cells is downregulated by the γ-secretase inhibitor DAPT. In addition, treatment of MDA-MB-231 cells with siRNA specific for Notch-1 and Notch-3 downregulates the expression of i21 Flt1. In agreement with these findings, HUVEC and MDA-MB-231 breast cancer cells, cultured on dishes coated with recombinant human Dll4 extracellular domain, express higher levels of i21 Flt1. In cancer cells, Flt1 is a target of the micro RNA family miR-200. In MDA-MB-231 breast cancer cells, the truncated intracellular isoform i21 Flt1 is also negatively regulated by miR-200c. Retinoic acid interferes i21 Flt1 expression by downregulating Notch-3 and upregulating miR-200 expression. Treatment of MDA-MB-231 breast cancer cells with both a γ-secretase inhibitor and retinoic acid suppresses the expression of i21 Flt1, providing a new mechanism to explain the effectiveness of this therapeutic approach.
authors.affiliation: Laboratori de Genètica Molecular, Departament de Ciències Fisiològiques I, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Mezquita
authors.forename: Jovita
authors.initials: J
authors.lastname: Mezquita
authors.forename: Carme
authors.initials: C
authors.lastname: Barrot
authors.forename: Silvia
authors.initials: S
authors.lastname: Carvajal
authors.forename: Montserrat
authors.initials: M
authors.lastname: Pau
authors.forename: Pau
authors.initials: P
authors.lastname: Mezquita
authors.forename: Cristóbal
authors.initials: C
authors.lastname: Mezquita
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002135:Calcium-Binding Proteins; D045744:Cell Line, Tumor; D004151:Dipeptides / Q000494:pharmacology; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics; D020033:Protein Isoforms; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism; D000071656:Receptor, Notch3; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C424126:DLL4 protein, human; D004151:Dipeptides; D036341:Intercellular Signaling Peptides and Proteins; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; C497761:NOTCH1 protein, human; C499374:NOTCH3 protein, human; D020033:Protein Isoforms; D051881:Receptor, Notch1; D000071656:Receptor, Notch3; D051880:Receptors, Notch; D014212:Tretinoin; C501162:FLT1 protein, human; D040281:Vascular Endothelial Growth Factor Receptor-1; D053829:Amyloid Precursor Protein Secretases
keywords: BREAST CANCER; CELL INVASION; NOTCH-1; NOTCH-3; Truncated Flt1; VEGFR1; miR-200