Xylocydine, a novel inhibitor of cyclin-dependent kinases, prevents the tumor necrosis factor-related apoptosis-inducing ligand-induced apoptotic cell death of SK-HEP-1 cells

Xylocydine (4-amino-6-bromo-7-(beta-L-xylofuranosyl) pyrrolo[2,3-d] pyrimidine-5-carboxamide) blocks cyclin-dependent kinase CDK1 and CDK2/cyclin A activity in vitro (IC50 1.4 and 61 nM, respectively) while minimally inhibiting the three other Ser/Thr protein kinases tested (IC50 21-86 muM). Reduced phosphorylated nucleolin and retinoblastoma protein levels showed it also efficiently inhibited cellular CDK1 and CDK2 activity (IC50 50-100 and 200-500 nM, respectively). Moreover, it blocked the functional activity of CDKs in tumor necrosis factor-related apoptosis-inducing ligand-induced SK-HEP-1 cell apoptosis 20 to 1000-fold more potently than olomoucine and roscovitine. Xylocydine is thus a novel and potent CDK inhibitor that could be used to interfere with cell cycle- and apoptosis-related CDK activity in various diseases.