THE EFFECT OF THE CYCLIN-DEPENDENT KINASE INHIBITOR OLOMOUCINE ON CELL-CYCLE KINETICS

The effect of the cyclin-dependent (CDK) inhibitors olomoucine and ros covitine on cell kinetics was studied. To this end, nonsmall cell lung cancer (NSCLC) cell line MR65 and neuroblastoma cell line CHP-212 wer e pulse labeled with bromodeoxyuridine (BrdUrd) and chased in culture medium, to which various concentrations of olomoucine or roscovitine w ere added. A dose-dependent inhibition of the G(1)/S-phase and G(2)/M- /G(1) transitions was observed. Furthermore, S-phase progression was a lso inhibited in a dose-dependent manner. Similarly, roscovitine, anot her CDK inhibitor with a 10-fold higher efficiency for both CDK1 and C DK2 as compared to olomoucine, showed the same effects at a 10-fold lo wer concentration. At the highest tested doses both olomoucine (200 mu M) and roscovitine (40 mu M) induced a complete cell cycle block in b oth cell lines, paralleled by the appearance of apoptotic figures. In these cultures a decrease in CDK1 protein level was found as shown by Western blotting. Bivariate CDK1/DNA analysis confirmed these observat ions and showed that a subpopulation of cells with characteristics of apoptosis became CDK1 negative. The presented data suggest that cyclin s and CDKs are involved at an important nodal point shared by pathways regulating cellular proliferation and apoptosis. (C) 1997 Academic Pr ess.