Cyclin-dependent Kinase (CDK) Inhibitor Olomoucine Enhances γ-Irradiation-induced Apoptosis and Cell Cycle Arrest in Raji Cells

Abstract

Gamma-irradiation leads to apoptosis and cell cycle arrest in eukaryotic cells. Olomoucine is a novel purine analog acting as a cyclin-dependent kinase inhibitor. The effects of olomoucine in gamma-irradiation mediated cell growth inhibition and apoptosis were studied in the Raji cell line (Burkitt's lymphoma). Gamma-irradiation caused a G₂ arrest, increasing the G₂/M fragment of the cells. Apoptosis by gamma-irradiation was apparent both by DNA-electrophoresis and PARP-1 cleavage. The combination of olomoucine with irradiation caused an increased G₂ arrest and decreased cell survival and DNA synthesis in the non-apoptotic fraction of the remaining cells. Irradiation, as well as olomoucine and the combination of both, induced apoptosis. It seems that olomoucine delays the apoptotic process and inhibits DNA fragmentation, but it decreased survival, cell cycle progression and proliferation of irradiated cells.