Cancer research at the University of Otago shows that bacteria can help fight cancerous tumors by boosting the body’s immune response.
Associate Professor Alex McLellan from the Department of Microbiology and Immunology explains that, “these natural killer cells are stimulated by the bacteria” which then in turn enables the immune system to more easily identify and attack the cancerous tumor cells. The body sends out cancer-specific T cells which appear to release growth hormones that strengthen other immune cells.
The theory that bacteria can help fight cancer is over a century old and is the foundation immunotherapy cancer research today.
In the 1890s, William B. Coley, M.D. observed that cancer patients who suffered from a bacterial infection often went into remission. He developed a treatment called Coley’s toxins, which is a mix of bacteria injected into the patient to intentionally cause a continuous fever. It was thought that the tumor cells were more susceptible to fever and that the infection activated the body’s immune response, which then attacked the tumors. This treatment was very dangerous and the research methods of the time were not as vigorous as today’s standards, so Coley’s toxins have been largely abandoned in the USA in favor of more modern treatments such as chemotherapy and other immunotherapies.
Recently, Coley’s theories have been revisited using genetic engineering and an advanced understanding of the immune system. In 2013, the Proceedings of the National Academy of Sciences reported that bacteria injected with radioactive isotopes had been successfully used to fight pancreatic cancer. Ekateria Dadchova of the Albert Einstein College of Medicine in New York used the bacteria Listeria monocytogenes to deliver the radiation, turning the cancer’s immune suppression against itself as the rest of the body easily fights off the weak bacteria. Further research is needed on this method to ensure that patients’ healthy body tissue is not damaged by the radiation.
Researchers hope to use different bacteria to attack different types of cancers, and to use them to deliver treatment to the cancer site. For instance, salmonella will congregate in the intestines and may be engineered to attack cancers there. Blood Journal describes this trojan horse method and how it might be used to deliver more helper immune cells to the tumor. If the bacteria also trigger a heightened immune response, then patients may benefit from a two-prong treatment. This research is especially important for cancers that do not respond well to standard treatments.
This breakthrough comes at a time when cancer is predicted to be the #1 Killer in the United States.
Many of these studies have been done using mice. According to Dr. McLellan, the next step in bacterial immunotherapy research is testing using human cells.