Cancer-Fighting Bacteria

Aug. 30, 2013

By Medical Discovery News

Anyone who has experienced the nightmare of food poisoning would probably steer clear of any chance of that. But now, one of the very causes of such illnesses is being tested as a way to treat cancer.

Typically, Listeria monocytogenes infects people when they eat contaminated foods, resulting in 1,600 cases of listeriosis food poisoning each year. The symptoms are fever and muscle aches sometimes along with diarrhea or other gastrointestinal symptoms. It primarily affects the elderly, newborns, or pregnant women, although occasionally people without these risk factors also become ill. In people with compromised immune systems, symptoms can include headaches, stiff necks, confusion, and convulsions. For some, the infection can lead to septicemia, which means that bacteria are in the blood and can lead to a much more rapid deterioration. Listeriosis can also lead to meningitis, a possibly fatal condition in which the bacteria infect the membranes that cover the brain and spinal column. In older adults and people with other serious medical problems, even immediate treatment may not be effective and they can die. 

But a weakened form of the bacterium might be able to deliver radiation directly to cancer cells and effectively kill them. Scientists genetically engineered listeria cells so they were coated with a protein called a monoclonal antibody. Then they attached a radioactive compound called rhenium-188 to the protein. When injected into mice with human cancerous tumors, these modified bacteria cells delivered radioactivity to the tumor cells without harming normal cells. 

The real advantage of this new approach is that it not only targets the primary tumor, but is even better at finding cancer cells that have migrated to other locations in the body. These other metastatic cancer cells are very difficult to target with other therapies. Scientists were unable to find any damage to normal tissues from either the bacteria cells or the radioactive rhenium. Both the bacteria and the rhenium were no longer detectable in the mice one week after the last treatment.

For the experiment, scientists used pancreatic cancer cells. Pancreatic cancer is the most lethal type of cancer, leaving only 4 percent of its victims alive five years after diagnosis. Its location makes diagnosis difficult, and because symptoms often aren’t recognized until the cancer is too advanced to survive, it’s usually too late. If the tumor is confined to the pancreas, then surgery is an option. Chemotherapy and radiation are also used to kill the cancer cells. That’s where this new treatment comes in.

Although this method must be refined to ensure that the bacteria used are as safe as possible and that no dangerous levels of radiation are released and accumulate in the body, it offers hope to the 40,000 people diagnosed with pancreatic cancer each year.

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