Anti-tumor activity of endotoxin depends on activation of serum complement fragments

The anti-tumor activity of endotoxin (LPS), derived from E. coli O127, on the subcutaneous tumor MH134 inoculated into C3H/He mice in vivo was examined. On repeated examination, LPS administration of 50-100 micrograms/head induced a 50% complete cure rate. However, pretreatment with K76COONa inhibited the anti-tumor activity of LPS, and no case of cure could be found. These results showed that the main anti-tumor activity of LPS administration consisted of complementary activation, mainly from the C5 step. The fact that the intraperitoneal administration of human complement activated serum with agar apparently inhibited the tumor growth in vivo certified these phenomena.