Effects of roscovitine on DNA synthesis in normal and neoplastic glial cells.

MF Vita, MSa, JS Yakisich a, J. Boethius MD PhD b, I. Ohlsson Lindblom MD b, L. Wallstedt MD b, V. Idoyaga Vargas MD PhD c, A. Sidacon MD PhD a, M. Cruz MD PhD a

Karolinska Institute, Stockholm, Stockholm, Sweden

AIM: To study the effects of roscovitine, a purine analogue and inhibitor of cyclin-dependent kinases (CDKs), on DNA synthesis. METHODS: Normal rat brain, experimental rat gliomas (RG2) and 8 human gliomas (grade III and IV) were used for preparation of tissue mini-units: multicellular tissue fragments. Roscovitine concentrations of 1-100 µM were used. DNA synthesis rate was calculated by determination of (methyl-3H)-thymidine incorporation into DNA (cpm/mg of protein/min). The incubation times were 0-90 min. RESULTS: Roscovitine gave a concentration-dependent inhibition of DNA synthesis rate in developing (5-14 postnatal days) rat brain. The inhibition occurred within 30 min. Incubation during 90 min with 100 µM of roscovitine gave 90% inhibition of DNA synthesis rate. Incubation with 250 µM of staurosporine, another potent CDK-inhibitor, during 90 min gave no inhibition. The effects of roscovitine on DNA synthesis rate in human gliomas were similar. Incubation with 100 µM of roscovitine for 90 min gave an inhibition of 71-97%; the IC50 (data from 3 tumors) was <10 µM. DNA synthesis rate in rat gliomas was also inhibited to a significant degree by 90 min incubation with roscovitine: 23% by 5 µM, 60% by 25 µM and 68% by 50 µM. CONCLUSIONS: Roscovitine gives an early and strong inhibition of DNA synthesis rate in developing rat brain, human malignant gliomas and experimental rat gliomas. The early onset, within 30 min, makes it improbable that the mechanism of action is inhibition of CDKs and/or replication licensing factor.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Novel Therapies, Part 1.