Bacteria Defeat Tumors
Infections train the immune system to destroy cancerous cells

Context: Many clinicians and researchers attempt to treat cancer without resorting to debilitating chemo- and radio­therapy. But even "magic bullet" drugs, which hone in specifically on cancer cells, have serious side effects. A better option may be to train a patient's own immune system to attack tumors. Now researchers at Johns Hopkins University, led by Bert Vogelstein, have found that bacteria show promise as a means of priming the immune system, and might be used to treat cancer of the liver, lungs, and pancreas.

Methods and Results: Animals with cancerous tumors were injected with bacteria that thrive in the oxygen-deprived centers of solid tumors and die off in healthy, oxygenated tissues. The researchers hoped that the bacteria would destroy the tumors from the inside out, leaving an outer rim of cancer cells that could be more easily treated with standard therapies. The bacteria did just that. However, the researchers also found that the infection frequently prompted the subject's immune system to recognize the cancer and attack it. In 23 of 70 test animals, this immune response destroyed the remains of the tumor without additional therapy. Even after the bacterial infections cleared, the animals' immune systems attacked newly injected cancerous cells of the type successfully treated. The treatment had similar effects in both mice and rabbits, making it plausible that it could also work in other species, including humans.