RESUMEN
Polo-like kinases (Plks) have several functions in mitotic progression and are upregulated in many tumor types. Small-molecule Plk inhibitors would be valuable as tools for studying Plk biology and for developing antitumor agents. Guided by homology modeling of the Plk1 kinase domain, we have discovered a chemical series that shows potent and selective Plk1 inhibition. The effects of one such optimized benzthiazole N-oxide, cyclapolin 1 (1), on purified centrosomes indicate that Plks are required to generate MPM2 epitopes, recruit gamma-tubulin and enable nucleation of microtubules. The compound can also promote loss of centrosome integrity and microtubule nucleating ability apparently through increased accessibility of protein phosphatases. We show that treatment of living S2 cells with cyclapolin 1 leads to collapsed spindles, in contrast to the metaphase-arrested bipolar spindles observed after RNAi. This different response to protein depletion and protein inhibition may have significance in the development of antitumor agents.
Asunto(s)
Benzotiazoles/farmacología , Proteínas de Ciclo Celular/antagonistas & inhibidores , Óxidos N-Cíclicos/farmacología , Drosophila melanogaster/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Huso Acromático/efectos de los fármacos , Animales , Benzotiazoles/química , Sitios de Unión , Proteínas de Ciclo Celular/fisiología , Línea Celular , Centrosoma/efectos de los fármacos , Centrosoma/metabolismo , Óxidos N-Cíclicos/química , Drosophila melanogaster/citología , Células HeLa , Humanos , Microtúbulos/efectos de los fármacos , Microtúbulos/metabolismo , Modelos Moleculares , Estructura Molecular , Proteínas Serina-Treonina Quinasas/fisiología , Proteínas Proto-Oncogénicas/fisiología , Huso Acromático/fisiología , Estereoisomerismo , Relación Estructura-Actividad , Factores de Tiempo , Quinasa Tipo Polo 1RESUMEN
CDK2 inhibitors have been proposed as effective anti-cancer therapeutics. We show here that CYC202 (R-roscovitine) is a potent inhibitor of recombinant CDK2/cyclin E kinase activity (IC(50) = 0.10 microM) with an average cytotoxic IC(50) of 15.2 microM in a panel of 19 human tumour cell lines, and we also demonstrate selectivity for rapidly proliferating cells over non-proliferating cells. A study of the cell cycle effects of CYC202 in Lovo colorectal carcinoma cells showed that the major effect was not the predicted arrest in one part of the cycle, but rather an induction of cell death from all compartments of the cell cycle. The maximum tolerated dose given intravenously to mice was in excess of 20 mg/kg. Doses up to 2,000 mg/kg were tolerated when administered orally in mice. Following repeated intraperitoneal administration (3 times daily for 5 days) of 100 mg/kg to nude mice bearing the Lovo human colorectal tumour, CYC202 induced a significant antitumour effect with a 45% reduction in tumour growth compared to controls. A second experiment using the human uterine xenograft MESSA-DX5 treated with orally administered CYC202 (500 mg/kg 3 times daily for 4 days) also exhibited a significant reduction in the rate of growth of the tumour (62%). These data, showing enzyme and cellular potency together with antitumour activity, confirm the potential of CDK2 inhibitors such as CYC202 as anticancer drugs.