Independent actions on cyclin-dependent kinases and aryl hydrocarbon receptor mediate the antiproliferative effects of indirubins

M. Knockaert , M. Blondel , S. Bach , M. Leost (1) , C. Elbi , Hager G. L. , Nagy S. R. , D. Han , M. Denison , M. Ffrench , Ryan X. P. , P. Magiatis , P. Polychronopoulos , P. Greengard , L. Skaltsounis , L. Meijer (1)

1 MCT - Molécules et cibles thérapeutiques

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.

Mots clés: Animals Cell Cycle/drug effects Cell Cycle Proteins/biosynthesis/genetics Cell Line; Tumor/drug effects Cyclin-Dependent Kinase Inhibitor p27 Cyclin-Dependent Kinases/*antagonists & inhibitors Drug Screening Assays; Antitumor G1 Phase/drug effects Growth Inhibitors/*pharmacology Humans Indoles/chemistry/metabolism/*pharmacology Ligands Liver Neoplasms; Experimental/pathology Mice Protein Binding Protein Transport/drug effects Receptors; Aryl Hydrocarbon/deficiency/*drug effects/metabolism Research Support; Non-U.S. Gov't Research Support; U.S. Gov't; P.H.S. Structure-Activity Relationship Tetrachlorodibenzodioxin/metabolism/pharmacology Tumor Suppressor Proteins/biosynthesis/genetics

Domaines: Biochimie, Biologie Moléculaire

M. Knockaert, M. Blondel, S. Bach, M. Leost, C. Elbi, et al.. Independent actions on cyclin-dependent kinases and aryl hydrocarbon receptor mediate the antiproliferative effects of indirubins. Oncogene, 2004, 23, pp.4400-4412. ⟨hal-00020122⟩