ATO increased the cytotoxic effect of 2-ME in CLL cells that were resistant to 2-ME alone in vitro.

(A) A total of 10 resistant (IC₅₀ > 30 μM 2-ME) and 8 sensitive (IC₅₀ < 11 μM 2-ME) CLL patient samples were identified, and the basal cellular O₂⁻contents were shown. * indicates a statistically significant difference when compared with the sensitive cells. Error bars indicate SD of the means. (B) The combined effect of 2-ME and ATO in the 2-ME–resistant CLL cells (n = 15 patients). * indicates a statistically significant difference when compared with cells exposed to 2-ME alone (P < .05).