Bacteria that are known to cause infections have been genetically engineered to deliver an anti-tumor toxin to fight cancer. Jeff Hasty and his team at the University of California, San Diego, have engineered Salmonella bacteria to attack the parts of the tumors in mice that are most difficult to treat. The bacteria will self-destruct after completing their mission.
bacteria that survive without oxygen are well-equipped to live in an anaerobic environment within a tumor.
‘The researchers programmed Salmonella bacteria to self-destruct and break open after a certain number of them had accumulated in the tumor spot.’
"It's only natural that some bacteria have evolved to thrive in tumors," sais Hasty. The researchers used the blood vessels inside the tumors as a way to deliver chemotherapy. But the innermost parts of a tumor does not have blood vessels.
The researchers were inspired by the ability of Salmonella
to live in these areas. Hasty's team engineered the strains Salmonella
bacteria to produce three types of cancer-killing drug:
- One that destroys cell walls
- One that alerts the body's immune system and
- One that triggers cells to die
The researchers programmed the bacteria to self-destruct and break open after a certain number of them had accumulated in the same spot. "It's basically a kamikaze mission," said Hasty.
In mice that had liver tumors, the engineered bacteria traveled directly to the anaerobic regions of the tumors. The researchers found that when the mice were given bacteria that released all the three drugs, their tumors stopped growing.
When the mice were given a combination of bacteria and chemotherapy, their tumors shrank in size and their life expectancy increased by 50 percent.
The idea of using Salmonella
as a weapon to fight cancer has been around sometime, said, Bert Vogelstein at Johns Hopkins University in Baltimore, Maryland, who led one of the first experiments to try to harness bacteria as anti-cancer assassins 15 years ago.
"But every advance is good news. being able to successfully deploy bacteria against things that attack the body would be a game changer."
This new method is the first to deliver drugs by programming bacteria to break apart and die. This technique releases drugs and also keeps the number of bacteria under control.
"The major advance is that this is a way to provide sustained release of therapeutics in tumors," says Neil Forbes at the University of Massachusetts Amherst.
How bacteria get to the liver tumors when fed to the mice is not exactly known, said Hasty. Bacteria could have probably traveled through the hepatic portal vein.