Augmented inhibition of tumor cell proliferation in the combined use of disulfiram with ascorbic acid and the involvement of oxygen free radicals.

To examine the roles of oxygen free radicals in the inhibition of tumor cell proliferation, we have used disulfiram (DS), a metal-chelator, to inactivate superoxide dismutase and ascorbic acid (AsA) to inhibit catalase. Simultaneous addition of DS and AsA to Meth A tumor cells or Ehrlich ascites tumor cells induced marked inhibition of the cell proliferation assessed by [3H]thymidine uptake and trypan blue dye exclusion method. Similar augmented inhibition of Meth A tumor cell proliferation was observed when the cells were pretreated with DS and AsA. However, the addition of catalase (2000 u/ml) nullified the augmentation of anti-proliferative effect which can be induced in the combined use of DS and AsA. These results suggest that the steady-state increase of intracellular oxygen free radicals within tumor cells could be induced in the combined use of DS and AsA.