Radioactive Listeria Delivers Therapy To Kill Cancer

Radioactive Listeria Delivers Therapy To Kill Cancer
Researchers attached radioactive isotopes to bacteria to deliver radiation for treating pancreatic cancer. Creative Commons

In the arduous battle against cancer, radiation therapy has come a long way from its toxic undertakings to breakthroughs in irradiating the dreaded disease.

For pancreatic cancer, there are no effective alternatives.  It's one of the deadliest forms, causing certain death to nearly 38,460 people in the United States alone.  But a new study introduces an unlikely microbial helper, specifically the Listeria bacteria, which was shown to effectively deliver radiation to even the most severe forms of metastatic pancreatic tumors without harming the healthy tissue.

"We're encouraged that we've been able to achieve a 90 percent reduction in metastases in our first round of experiments," said Claudia Gravekamp, co-author and associate professor of microbiology and immunology at Albert Einstein College of Medicine. "With further improvements, our approach has the potential to start a new era in the treatment of metastatic pancreatic cancer."

In this study, researchers attached radioactive isotope rhenium to a weakened Listeria and injected them into the abdomens of mice with metastatic pancreatic cancer once a day for a week.  The procedure was followed by a week of rest, then four more days of injections. 

On the 21st day, cancer growth was cut 90 percent and the bacteria had focused its fight against the tumor-fested cells instead of the healthy ones.   

Normally, Listeria causes infection and could lead to fever, aches, nausea and diarrhea after eating contaminated food.  If it spreads it could cause headache, stiffness to neck, confusion and convolutions. 

Researchers previously found that the Listeria bacteria could infect only cancer cells because it allows them to thrive under the body's weak immune system.  They wanted to see how this played out in animals and whether the bacteria could carry treatments to annihilate the tumors.

"We chose rhenium because it emits beta particles, which are very effective in treating cancer," said Ekaterina Dadachova, co-author and professor of radiology and microbiology and immunology. "Also, rhenium has a half-life of 17 hours, so it is cleared from the body relatively quickly, minimizing damage to healthy tissue."

Healthy cells have a lot of times been compromised when it comes to treating cancers.  Chemotherapy drugs are known for causing serious side effects because they kill cells that are constantly dividing, including hair follicles, bone marrow and skin cells.

According to the American Cancer Society, more than 45,200 people will be diagnosed with pancreatic cancer in the United States. The lifetime risk of getting pancreatic cancer is about one in 78 and patients who receive the diagnosis have a five-year survival rate of 4 percent.

"At this point, we can say that we have a therapy that is very effective for reducing metastasis in mice," Gravekamp said. "Our goal is to clear 100 percent of the metastases, because every cancer cell that stays behind can potentially form new tumors."

The study's findings appear in the Proceedings of the National Academy of Sciences.

Join the Discussion