Listeria bacteria has been enlisted by researchers to selectively infect metastatic pancreatic cancer 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. Mice livers are shown above. The saline control liver on the left presents a large number of metastases compared to the liver on the right which was subject to the radioactive Listeria treatment.