title: Retinoic acid-induced expression of apolipoprotein D and concomitant growth arrest in human breast cancer cells are mediated through a retinoic acid receptor RARalpha-dependent signaling pathway.
abstract: Apolipoprotein D (apoD) is a human plasma protein, belonging to the lipocalin superfamily, that is produced by a specific subtype of highly differentiated breast carcinomas and that is strongly up-regulated by retinoic acid (RA) in breast cancer cells. In this work, we have examined the molecular mechanisms mediating the induction of apoD gene expression by retinoids in T-47D human breast cancer cells. Northern blot analysis revealed that Ro40-6055, a synthetic retinoid that selectively binds and activates the retinoic acid receptor RARalpha, induced the accumulation of apoD mRNA in breast cancer cells in a time- and dose-dependent manner. The time course analysis demonstrated that apoD mRNA was induced 14-fold over control cells after 48 h of incubation with 10(-8) M Ro40-6055. As little as 10(-11) M of this retinoid induced apoD mRNA 5-fold over the control, whereas incubation with 10(-7) M Ro40-6055 induced maximally 15-fold over control cells. RARalpha-selective antagonists counteracted the inductive effects of all-trans-RA, 9-cis-RA, and Ro40-6055 on the expression of apoD, when present at the same concentration as the retinoid agonists. By contrast, RARbeta-, RARgamma-, and RXR-selective retinoids did not affect apoD gene expression. The retinoid agonist Ro40-6055 had an antiproliferative effect on T-47D cells, with maximal growth inhibition of approximately 60% obtained after 7 days of incubation with 10(-7) M. This antiproliferative effect could be counteracted by a 100-fold excess of the antagonist Ro41-5253. Treatment of the cells with retinoids that do not bind the nuclear retinoic acid receptors did not affect apoD expression, despite the fact that they did have a strong antiproliferative effect on T-47D cells. On the basis of these results, a role for RARalpha on apoD gene expression induction by retinoids in breast cancer cells is proposed.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Oviedo, 33006-Oviedo, Spain.
authors.forename: Y S
authors.initials: YS
authors.lastname: López-Boado
authors.forename: M
authors.initials: M
authors.lastname: Klaus
authors.forename: M I
authors.initials: MI
authors.lastname: Dawson
authors.forename: C
authors.initials: C
authors.lastname: López-Otín
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001053:Apolipoproteins / Q000096:biosynthesis*; D053399:Apolipoproteins D; D001565:Benzoates / Q000494:pharmacology; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D002839:Chromans / Q000494:pharmacology; D005260:Female; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism*; D012176:Retinoids / Q000494:pharmacology; D015398:Signal Transduction; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D001053:Apolipoproteins; D053399:Apolipoproteins D; D001565:Benzoates; D002839:Chromans; D009025:Morpholines; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D012176:Retinoids; D013764:Tetrahydronaphthalenes; C068073:Am 580; C084904:Ro 41-5253; D014212:Tretinoin; C081137:mofarotene