Augmented antiproliferative effect of tumor necrosis factor (TNF), lymphotoxin and glycyrrhizin in combined use with diethyldithiocarbamate on Meth A tumor cells in vitro.

Role of oxygen free radicals in inhibition of proliferation of Meth A tumor cells was studied. Diethyldithiocarbamate (DDC), a chelator which inactivates superoxide dismutase, was used to examine the effect of tumor necrosis factor (TNF), lymphotoxin preparation derived from a human lymphoid cell line (c-LT) and glycyrrhizin (GL) on in vitro proliferation of Meth A tumor cells. High degree of antiproliferative effect was observed when DDC was added simultaneously with TNF to target cells. Similar effect was obtained by the addition of GL. However, augmentation of antiproliferative effect was not observed when c-LT was added. However, augmentation of antiproliferative effect was observed when the target cells had been treated with DDC in advance of the addition of TNF, GL or c-LT. Roles of oxygen free radicals in inhibition of tumor cell proliferation were discussed.