In recent years there has been an increasing interest in the azinomycin epoxide (2S, 3S)-benzyl 3,4-epoxy-2-(3-methoxy-5-methyl-1-naphthoyloxy)-3-methylbut anamide (EA), a potent cytotoxic and anti-tumour antibiotic. However, the molecular mechanisms of its cytotoxic activity have not yet been investigated. Here we report that exposure of the THP-1 human myeloid leukaemia cells to EA leads to the activation of apoptosis signal-regulating kinase 1 via a redox-dependent mechanism in a concentration and time-dependent manner. Accumulation of p53 and activation of caspase 3 were also seen. This was consistent with EA concentration-dependent accumulation of HIF-1alpha protein peaking after 4 h of stimulation with EA. Experiments with THP-1 cells, where the activity of ASK1 was blocked by transfection with the dominant-negative form of ASK1 demonstrated the importance of this enzyme for EA-dependent activation of caspase 3. Accumulated HIF-1alpha protein did not, however, promote EA-induced activation of caspase 3 or accumulation of p53. The experiments with p53 knockdown THP-1 cells demonstrated that this protein is not important for EA-induced activation of ASK1, caspase 3 or accumulation of HIF-1alpha protein. This is consistent with previous results indicating a reduced activity of p53 in THP-1 cells.