Cytokins, N6-subsitued adenine derivatives play an important role in many different processes in plant development (

Mok et al,
Annu Rev Plant. Physiol Plant Mol Biol
), including the cell growth and division control, the vegetable cell differentiation with auxin and the storage of various metabolites as alkaloids (
Yahia et al,
Plant Science
). Furthermore, several studies suggest that cytokinins and their purin derivated are able to control mammalian cell apoptosis and differentiation of human leukemic cells (HL-60 myeloblastic cell line) into mature granulocytes (
Ishii et al,
Cell Growth Differ
). All these compounds exert their biological activity via Cyclin-Dependant Kinase (CDK) inhibition and particulary CDK1 and CDK2. The aim of our study was the synthesis of new 7-azaindole derivates as cytokinin analogues and the evaluation of their biological effects on HL-60 cells.

Eight analogues of 7-azaindole were prepared by the condension of (N-methyl-)4-chloropyrrolo[2,3-b]pyridine with corresponding amines using palladium-catalyzed reaction (

Hartwig et al,
Angew Chem IN Ed
). The four derivates from 1H-pyrrolo[2,3-b]pyridine were 4-phenylamino-7-azaindole, 4-benzylamino-7-azaindole, 4-phenethylamino-7-azaindole and 4-phenylpiperazylamino-7-azaindole. The four derivates from 1-methyl-pyrrolo[2,3-b]pyridine were 4-phenylamino-N-methyl-7-azaindole, 4-benzylamino-N-methyl-7-azaindole, 4-phenetylamino-N-methyl-7-azaindole and 4-phenylpiperazylamino-N-methyl-7-azaindole. HL-60 cells were exposed to three concentrations of these compounds (10–100–500 μM) during 72h at 37°C. The number of viable cells was determined by Trypan blue exclusion, and the cell cycle was assessed by propidium iodide staining followed by flow cytometric analysis. All these compounds decreased the number of viable cells. The compounds of the NH serie were more active than their methyl-analogues, especially 4-phenylamino-N-methyl-7-azaindole and 4-phenethylamino-7-azaindole which presented an estimated IC50 of 2 μM. Moreover, when used at 10 μM, 4-phenylamino-N-methyl-7-azaindole induced apoptosis whereas 4-phenethylamino-7-azaindole promoted inhibition of the cell cycle without pro-apoptotic effect.

These results suggest that cytokinin analogues derived from 1H-pyrrolo[2,3-b]pyridine may present interesting therapeutic potential as cytostatic agents. Further studies will clarify their biological effects on leukemic cells.

Disclosure: No relevant conflicts of interest to declare.

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