Different G{sub 2}/M accumulation in M059J and M059K cells after exposure to DNA double-strand break-inducing agents

Purpose: To investigate and compare the cell cycle progression in relation to cell death in the human glioma cell lines, M059J and M059K, after exposure to DNA double-strand break-inducing agents. Methods and materials: The M059J and M059K cells, deficient and proficient in the catalytic subunit of the DNA-dependent protein kinase, respectively, were exposed to 1 and 4 Gy of photons or accelerated nitrogen ions. In addition, M059J and M059K cells were treated with 10 and 40 {mu}g/mL of bleomycin for 30 min, respectively. Cell cycle progression, monitored by DNA flow cytometry, was measured up to 72 h after treatment. Results: M059J, but not M059K, cells displayed G{sub 2}/M accumulation after low linear energy transfer irradiation. High linear energy transfer radiation exposure however, resulted in a substantial increase of M059K cells in the G{sub 2}/M phase detected at 48 h. At 72 h, the number of cells in the G{sub 2}/M phase was equivalent to its control. M059J cells accumulated mainly in S phase after high linear energy transfer irradiation. In contrast to M059K, M059J cells were still blocked at 72 h. Bleomycin induced G{sub 2}/M accumulation for both M059J and M059K cells detected 24 h after treatment. At 48 h, the percentage of bleomycin-treated M059J cells in G{sub 2}/M phase remained high, and the number of M059K cells had decreased to control levels. Neither cell line showed cell cycle arrest ({