Augmentation of in vitro cytotoxicity and in vivo tumor-inhibition by combined use of lymphotoxin-containing supernatants and antitumor drugs.

The cytotoxicity of combined antitumor drugs and lymphotoxin (LT)-containing supernatants was studied on target cells. Marked reduction of L cells was observed after combined use of LT-containing supernatants with actinomycin D, adriamycin or aclacinomycin A but not with mitomycin C or vincristine sulphate. Similar effects were observed in Sarcoma 180 cells and Ehrlich ascites tumor cells in vitro. The survival of mice injected i.p. with Ehrlich ascites tumor cells was prolonged by the combined use of LT-containing supernatants and actinomycin D (0.1 or 0.3 microgram/mouse). The mechanisms of the synergistic effect are discussed in regard to the mode of action of antitumor drugs.