title: Differential regulation of sodium/iodide symporter gene expression by nuclear receptor ligands in MCF-7 breast cancer cells.
abstract: The sodium/iodide symporter (NIS) mediates iodide uptake in lactating breast tissue and is expressed in some breast cancers. We have previously demonstrated that all-trans retinoic acid (tRA) stimulates NIS gene expression and the selective cytotoxic effect of beta-emitting radioiodide-131 ((131)I) in both in vitro and in vivo MCF-7 breast cancer cell systems. We studied the ability of natural and synthetic retinoids, in combination with other nuclear receptor ligands, to achieve greater and more sustained induction of NIS in MCF-7 cells and enhance (131)I-mediated cytotoxicity. Selective stimulation of retinoic acid receptor (RAR) beta/gamma produced marked NIS induction; and selective stimulation of RARalpha, RARgamma, or retinoid X receptor produced more modest induction. Maximal NIS induction was seen with 9-cis retinoic acid and AGN190168, a RAR beta/gamma-agonist. Dexamethasone (Dex), but not the other nuclear receptor ligands, in combination with tRA synergistically induced iodide uptake and NIS mRNA expression, predominantly by prolonging NIS mRNA half-life. The addition of Dex reduced the EC(50) of tRA for NIS stimulation to approximately 7%, such that 10(-7) m tRA with addition of Dex enhanced iodide uptake and selective cytotoxicity of (131)I greater than 10(-6) m tRA alone. AGN190168 combined with Dex synergistically increased iodide uptake and significantly prolonged induction (5 d) of iodide uptake compared with that induced by the combination of tRA/Dex or 9-cis retinoic acid/Dex. The addition of Dex reduced the effective dose of retinoid and prolonged the induction of NIS, especially with AGN190168, suggesting higher efficacy of (131)I after combination treatment.
authors.affiliation: Molecular Endocrinology Laboratory, Veterans Affairs Greater Los Angeles Healthcare System, David Geffen School of Medicine at the University of California, Los Angeles, CA 90073, USA.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kogai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kanamoto
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Li
authors.forename: Lisa H
authors.initials: LH
authors.lastname: Che
authors.forename: Emi
authors.initials: E
authors.lastname: Ohashi
authors.forename: Katsumi
authors.initials: K
authors.lastname: Taki
authors.forename: Roshantha A
authors.initials: RA
authors.lastname: Chandraratna
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Saito
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Brent
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology; D004334:Drug Administration Schedule; D004338:Drug Combinations; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D007454:Iodides / Q000493:pharmacokinetics; D007457:Iodine Radioisotopes / Q000494:pharmacology; D008024:Ligands; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D012176:Retinoids / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology; D014410:Tumor Stem Cell Assay; D000099209:Sodium-Iodide Symporters
chemical_list: D000970:Antineoplastic Agents; D018931:Antineoplastic Agents, Hormonal; D003907:Dexamethasone; D004338:Drug Combinations; D005938:Glucocorticoids; D007454:Iodides; D007457:Iodine Radioisotopes; D008024:Ligands; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D012176:Retinoids; D027981:Symporters; D014212:Tretinoin; D000099209:Sodium-Iodide Symporters