Norbert: As a microbiologist, Dave, would you recommend injecting a bacterium called Listeria monocytogenes into people?

Dave: Only people I don't like! That's the same bacteria that killed thirty-three people who ate contaminated cantaloupes two years ago.

Norbert: That's why it's fascinating when scientists find potentially lifesaving uses for bacteria such as this.

In clinical trials, researchers have engineered the Listeria bacteria to kill pancreatic cancer cells. Pancreatic cancer is among the deadliest forms of the disease, so there's absolutely a need for more effective treatments.

In this new approach, the bacteria was first weakened to make it safe to use. Next, researchers coated it with a protein called a monoclonal antibody and then linked a radioactive compound to the antibody. The radioactive-listeria were injected in mice carrying human pancreatic tumors that had metastasized.

The designer bacteria were able to destroy 90% of metastasized cells and 60% of the primary tumor. The therapy did not harm healthy cells because the mouse immune system could clear out the bacteria in healthy tissue.

The bacteria was left alone around cancer cells because cancer cells produce proteins that suppress the immune system. So, this therapy uses the cancer cells defense system against itself, allowing the radioactive-listeria to accumulate around tumors and deliver radioactivity to them. Researchers haven't conducted human clinical trials and they need to be sure the radioactive elements don't stay in the body before doing so. If the treatment is effective, it could help the 40,000 people who die from pancreatic cancer every year.