title: A truncated Ah receptor blocks the hypoxia and estrogen receptor signaling pathways: a viable approach for breast cancer treatment.
abstract: The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor which requires heterodimerization with the Ah receptor nuclear translocator (Arnt) for function. Arnt is also a dimerization partner of the hypoxia inducible factor 1alpha (HIF-1alpha) for the hypoxia signaling. Additionally, Arnt is found to be a potent coactivator of the estrogen receptor (ER) signaling. Thus we examined whether the presence of an increased amount of AhR may suppress both the HIF-1alpha and ER signaling pathways by sequestering Arnt. We tested our hypothesis using a human AhR construct C Delta553 which is capable of heterodimerizing with Arnt in the absence of a ligand. Transient transfection studies using a corresponding luciferase reporter plasmid in MCF-7 cells showed that C Delta553 effectively suppressed the AhR, HIF-1alpha, and ER signaling pathways. Reverse transcription/real-time QPCR data showed that C Delta553 blocked the up-regulation of the target genes controlled by AhR (CYP1A1), HIF-1alpha (VEGF, aldolase C, and LDH-A), and ER (GREB1, pS2, and c-myc) in MCF-7 cells. Since both HIF-1alpha and ER are highly active in the ER-positive breast cancer, C Delta553 has the potential to be developed as a protein drug to treat breast cancer by blocking these two signaling pathways.
authors.affiliation: Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, California 95211, USA.
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Jensen
authors.forename: Tony C
authors.initials: TC
authors.lastname: Luu
authors.forename: William K
authors.initials: WK
authors.lastname: Chan
mesh_terms: D000230:Adenocarcinoma / Q000628:therapy; D051792:Basic Helix-Loop-Helix Proteins; D001943:Breast Neoplasms / Q000628:therapy*; D017353:Gene Deletion; D017930:Genes, Reporter / Q000187:drug effects; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D000860:Hypoxia / Q000517:prevention & control*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism / Q000627:therapeutic use*; D011960:Receptors, Estrogen / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use; D015398:Signal Transduction / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008156:Luciferases; D018336:Receptors, Aryl Hydrocarbon; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; C111235:AHR protein, human; C497442:HIF1A protein, human