Effects of group B Streptococcus toxin on long-term survival of mice bearing transplanted Madison lung tumors.

GBS toxin is a polysaccharide exotoxin produced by group B Streptococcus. This organism causes sepsis and respiratory distress in human neonates (so-called early onset disease). This disease is marked by a strong inflammatory response only in the lung, with pulmonary sequestration of granulocytes and extensive capillary endothelial damage, and occurs only during the first few days after birth. We have found that a similar inflammatory response can be induced by i.v. infusion of picomole quantities of GBS toxin in the developing vasculature of transplanted tumors in mice and can significantly retard the tumor growth. When optimum treatment with GBS toxin was started shortly after tumor implantation, a majority of tumors in the mice regressed and the mice remained tumor-free for over 5 months. Some tumors regressed in mice receiving short-term treatment with GBS toxin, but recurred after the treatment was stopped. Median survival times were extended by all regimens and all doses of GBS toxin tested. No evidence of toxicity to the vasculature of other tissues was observed. GBS toxin is being tested for cancer therapy in humans.