[Antitumor effects of bacterial lipopolysaccharide and tumor necrosis factor in mice]

Using C3H/He mice, the antitumor effect and mechanism of lipopolysaccharide (LPS) were studied. The antitumor effect of rabbit serum containing tumor necrosis factor (TNF) was also studied. LPS and TNF, which were administered into mice with tumors, induced hemorrhagic necrosis. LPS and TNF significantly inhibited the tumor growth, as compared with findings in the controls. In the initial stage after LPS administration, dilatation of tumor vessels and thrombus formation in tumor vessels were observed in the histologic study. Tumor blood flow was measured by the hydrogen clearance technique. Tumor blood flow was very small, and was remarkably decreased at 2 hours after LPS administration. These results suggest that hemorrhagic necrosis after LPS administration was due to the decrease of the tumor blood flow. In the study in vitro, YAC-1 cells were damaged but K562 cells were not damaged by rabbit serum containing TNF. In order to find the effect of LPS or TNF on cellular immunity, the delayed type hypersensitivity (DTH) was studied. LPS and TNF prevented the decrease of DTH in the tumor bearing mice on day 25.