The food poisoning bug salmonella can be injected into tumours to flag cancer to the immune system so that it can be quickly cleared from the body, scientists have shown.
Cancer is extremely good at evading the body’s immune system, largely because a tumour is normal tissue which has gone awry, so the body does not see it as an invader.
Some cancers have also evolved to suppress or hide from the immune system.
But scientists have now shown they can use the salmonella bacteria as a ‘Trojan horse’ to infiltrate cancer cells so that the body knows they should be attacked.
Researchers at the Chonnam National University Hwasun Hospital in Jeonnam.
Republic of Korea, have engineered a safe form of salmonella which is one million times less potent that the strain which causes food poisoning, but is still recognized by the immune system.
Animals trials have been so successful that the team are now seeking funding for testing in humans. In tests on mice with colon cancer more than half were completely cured without any side effects.
British scientists said it offered a ‘fascinating new way’ to tackle cancer.
Joon Haeng Rhee, Professor of Microbiology at Chonnam, said: “We believe that this was a kind of groundbreaking trial to turn tumour-helping immune cells, Dr Jekyll, into tumour-killing ones, Mr Hyde.
“We use very cheap attenuated bacterial to target the tumor tissue and very promptly changed Dr. Jekyll into very furious Mr. Hyde by inducing salmonella in situ.
The bacterial strain, which specifically targeting tumours, are approximately 1 million fold attenuated in virulence. In other words, they are very safe. strain does not seem to cause any systemic inflammation or toxicity in internal organs.
Previous studies have looked at using bacteria like salmonella to carry anti-cancer drugs into tumours.
But it is the first time the scientists have tried using the body’s own response to salmonella to fight a tumour.
The team discovered the possibility while working on unrelated research in which they noticed that the bacteria that attacked shellfish produced a protein called FlaB that caused a strong immune response.
That led them to genetically modify the common salmonella bacteria so that it, too, would produce the protein – and spur the immune system into action.
Professor Kevin Harrington, Professor of Biological Cancer Therapies at The Institute of Cancer Research, London, said: “It has been known for some time that certain types of bacteria, including strains of salmonella, are able to grow in tumours but not in normal tissues.
“However, until now, attempts to use bacteria as anti-cancer therapies have had limited success, both in the laboratory and in the clinic.
“The current work by Zheng and colleagues represents a fascinating new approach to using bacteria.
“Instead of asking the bacteria to kill cancer cells directly, the researchers have genetically engineered salmonella so that it triggers the immune system to mount an attack on the tumour.”
Professor Paul Dyson, of Swansea University, who is also studying the use of salmonella in fighting cancer: “We believe there is huge mileage in pursuing research into this type of treatment. Existing evidence indicates there would few or no side effects.”
The research was published in the journal Science Translational Medicine