title: Independent actions on cyclin-dependent kinases and aryl hydrocarbon receptor mediate the antiproliferative effects of indirubins.
abstract: Indirubin, a bis-indole obtained from various natural sources, is responsible for the reported antileukemia activity of a Chinese Medicinal recipe, Danggui Longhui Wan. However, its molecular mechanism of action is still not well understood. In addition to inhibition of cyclin-dependent kinases and glycogen synthase kinase-3, indirubins have been reported to activate the aryl hydrocarbon receptor (AhR), a cotranscriptional factor. Here, we confirm the interaction of AhR and indirubin using a series of indirubin derivatives and show that their binding modes to AhR and to protein kinases are unrelated. As reported for other AhR ligands, binding of indirubins to AhR leads to its nuclear translocation. Furthermore, the apparent survival of AhR-/- and +/+ cells, as measured by the MTT assay, is equally sensitive to the kinase-inhibiting indirubins. Thus, the cytotoxic effects of indirubins are AhR-independent and more likely to be linked to protein kinase inhibition. In contrast, a dramatic cytostatic effect, as measured by actual cell counts and associated with a sharp G1 phase arrest, is induced by 1-methyl-indirubins, a subfamily of AhR-active but kinase-inactive indirubins. As shown for TCDD (dioxin), this effect appears to be mediated through the AhR-dependent expression of p27(KIP1). Altogether these results suggest that AhR activation, rather than kinase inhibition, is responsible for the cytostatic effects of some indirubins. In contrast, kinase inhibition, rather than AhR activation, represents the main mechanism underlying the cytotoxic properties of this class of promising antitumor molecules.
authors.affiliation: C.N.R.S., Cell Cycle Group and UPS-2682, Station Biologique, BP 74, 29682 ROSCOFF cedex, Bretagne, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Knockaert
authors.forename: Marc
authors.initials: M
authors.lastname: Blondel
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bach
authors.forename: Maryse
authors.initials: M
authors.lastname: Leost
authors.forename: Cem
authors.initials: C
authors.lastname: Elbi
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Hager
authors.forename: Scott R
authors.initials: SR
authors.lastname: Nagy
authors.forename: Dalho
authors.initials: D
authors.lastname: Han
authors.forename: Michael
authors.initials: M
authors.lastname: Denison
authors.forename: Martine
authors.initials: M
authors.lastname: Ffrench
authors.forename: Xiaozhou P
authors.initials: XP
authors.lastname: Ryan
authors.forename: Prokopios
authors.initials: P
authors.lastname: Magiatis
authors.forename: Panos
authors.initials: P
authors.lastname: Polychronopoulos
authors.forename: Paul
authors.initials: P
authors.lastname: Greengard
authors.forename: Leandros
authors.initials: L
authors.lastname: Skaltsounis
authors.forename: Laurent
authors.initials: L
authors.lastname: Meijer
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004354:Drug Screening Assays, Antitumor; D016193:G1 Phase / Q000187:drug effects; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D008024:Ligands; D008114:Liver Neoplasms, Experimental / Q000473:pathology; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D018336:Receptors, Aryl Hydrocarbon / Q000172:deficiency / Q000187:drug effects* / Q000378:metabolism; D013329:Structure-Activity Relationship; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics
chemical_list: C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D006131:Growth Inhibitors; D007211:Indoles; D008024:Ligands; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; C027185:indirubin