Ara-G cytotoxicity against mitochondrial DNA-depleted CEM (ρ
CEM) cells. (a) Determination of cytochrome c oxidase activity in ρ0CEM cells. The activity was completely suppressed in mitochondrial DNA-depleted variant cell line ρ0CEM as compared with CEM cells. (b, c) CEM cells and ρ0CEM cells were treated with 10 μM (b) or 100 μM (c) ara-G for 48 h. Sub-G1 induction was calculated by using flow cytometry. The values shown are the means ± SD of at least three independent experiments. The difference in the values between CEM cells and ρ0CEM cells was not significant for either concentration (P = 0.28 for 10 μM ara-G (b), P = 0.40 for 100 μM ara-G (c), unpaired T test).