Arsenic trioxide (As2O3) has been used to treat all-trans retinoic acid (ATRA) resistant relapsing acute promyelocytic leukemia. Recent investigations in our laboratory have showed that arsenic trioxide is cytotoxic to HL-60 cells, showing a LD50 of 6.4 ± 0.6 μg/mL. In the present study, we investigated the role of reactive oxygen species (ROS) in the anti-cancer activity of arsenic trioxide. We hypothesized that arsenic-induced oxidative stress and subsequent alteration in p53 and c-fos expression is involved in the molecular event leading to cytotoxicity and destruction of cancer cells. To test this hypothesis, we performed lipid peroxidation assay to determine the levels of malondialdehyde (MDA) and 4-hydroxy-2 (E)-nonenal (4-HAE) production in arsenic-treated HL-60 cells. We also performed Western Blot analysis to assess the expression of p53 and c-fos proteins in these cells. Study results showed a gradual increase of lipid peroxidation by-products in HL-60 cells within the dose range of 0-6 μg/mL, followed by a reduction at higher doses, probably due to cell mortality. Western Blot analysis also demonstrated a strong dose-response relationship with regard to p53 expression within the dose range of 0-6 μg/mL. c-fos expression was up-regulated within the dose range of 0-4 μg/mL, followed by a down-regulation between 4-6 μg/mL. In summary, these results showed that oxidative stress plays a significant role in the cytotoxicity of arsenic trioxide to human leukemia cells. It is also demonstrated that oxidative stress is associated with lipid peroxidation and activation of both p53 tumor suppressor protein and c-fos transcription factor in human leukemia cells. [Research supported by the National Institutes of Health RCMI-Grant No. 1G12RR13459].

[Proc Amer Assoc Cancer Res, Volume 46, 2005]