Radioactive Bacteria Targets Metastatic Pancreatic Cancer

Researchers at Albert Einstein College of Medicine of Yeshiva University have developed a therapy for pancreatic cancer that uses Listeria bacteria to selectively infect tumor cells and deliver radioisotopes into them.

The experimental treatment dramatically decreased the number of metastases (cancers that have spread to other parts of the body) in a mouse model of highly aggressive pancreatic cancer without harming healthy tissue.

Pancreatic cancer is among the deadliest of cancers, with a five-year survival rate of only 4 percent. The National Cancer Institute predicts that this year, 45,220 new cases of pancreatic cancer will be diagnosed and 38,460 people will die from the disease. Pancreatic cancer confined to the pancreas can be treated through surgery. But early pancreatic cancer is difficult to detect, since it rarely causes noticeable signs or symptoms. Most pancreatic cancer cases are diagnosed only after the cancer has spread (metastasized), typically resulting in jaundice, pain, weight loss and fatigue.

Several years ago, scientists observed that an attenuated (weakened) form of Listeria monocytogenes can infect cancer cells, but not normal cells. In a 2009 study, Dr. Gravekamp discovered the reason: The tumor microenvironment suppresses the body's immune response, allowing Listeria to survive inside the tumors. By contrast, the weakened bacteria are rapidly eliminated in normal tissues.

Scientists coupled a radioactive isotope called rhenium to the weakened Listeria bacteria. "We chose rhenium because it emits beta particles, which are very effective in treating cancer," said Dr. Dadachova. "Also, rhenium has a half-life of 17 hours, so it is cleared from the body relatively quickly, minimizing damage to healthy tissue."