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.
Why it Matters: The ideal cancer treatment, as currently imagined, would kill cancer cells without damaging healthy ones. The Hopkins researchers’ method goes even further, preparing the immune system to defeat cancer cells left behind after a tumor is destroyed. So far, bacterial therapy does not appear to have the side effects associated with current cancer treatments. Of course, many promising treatments in animals have disappointed in human tests. But if the therapy does prove safe and effective for humans, cancer patients could be looking at much more successful and comfortable treatments in the future.
Source: Agrawal, N. et al. 2004. Bacteriolytic therapy can generate a potent immune response against experimental tumors. Proceedings of the National Academy of Sciences 101: 15172-15177.