Antitumor effects of endotoxin against solid murine Meth A tumors of different ages. Quantitative histology of the tumors and regional lymph nodes.

Mice with 3-, 6-, 9- and 15-day Meth A tumors in the skin were injected intravenously with endotoxin to study age-dependent induction of tumor necrosis and reactive changes in draining lymph nodes. By 24 h after treatment with endotoxin, macroscopic necrosis was seen in 9-day, and to an even greater extent in 15-day tumors; microscopy showed extensive necrosis in 9-day tumors and some necrosis in 6-day tumors. The necrosis was predominantly coagulative, but the 9- and 15-day tumors showed a rim of hemorrhagic necrosis near the skin with surviving tumor tissue located at the lateral and basal margins. All the tumors showed about equal hyperemia by 4 h and mitotic arrest by 4 and 24 h. Depletion of mast cells, which were most numerous in the 9-day tumors, was seen on the dermal aspects by 24 h. Endotoxin did not change the morphology of the lymph nodes and disseminated tumor cells within 24 h. Endotoxin is known to cure 9-day Meth A tumors, and the extent of the rapid necrosis induced is clearly the crucial factor. Necrosis, however, is not a direct consequence of early hyperemia or mitotic arrest and other factors related to the age and site of the tumor, apparently affect whether or not necrosis ensues.