Independent actions on cyclin-dependent kinases and aryl hydrocarbon receptor mediate the antiproliferative effects of indirubins.
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.
Knockaert
Marie
M
C.N.R.S., Cell Cycle Group and UPS-2682, Station Biologique, BP 74, 29682 ROSCOFF cedex, Bretagne, France.
Blondel
Marc
M
Bach
Stéphane
S
Leost
Maryse
M
Elbi
Cem
C
Hager
Gordon L
GL
Nagy
Scott R
SR
Han
Dalho
D
Denison
Michael
M
Ffrench
Martine
M
Ryan
Xiaozhou P
XP
Magiatis
Prokopios
P
Polychronopoulos
Panos
P
Greengard
Paul
P
Skaltsounis
Leandros
L
Meijer
Laurent
L
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
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