Color-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells.
Credit: Rocky Mountain Laboratories, NIAID, NIH
SYDNEY: Treating tumours with Salmonella bacteria induces an immune response that effectively kills cancer cells, Italian scientists announced.
This research could lead to that holy grail of modern medicine: a cure for cancer.
“We demonstrated that it is possible … to generate immunotherapy protocols that are effective in controlling the growth of established tumours or in vaccinating against tumours,” said co-author Maria Rescigno of the study published in Science Translational Medicine.
Invisible cancer cells
The body’s natural immune responses are often able to detect and destroy early cancer cells. But as tumour cells progress and proliferate, they can become invisible to immune cells.
Salmonella bacteria cause illnesses such as typhoid fever and the food-bourn disease salmonellosis. Since their discovery they have generally been reviled by humanity, but that may be about to change.
A team of Italian scientists have demonstrated that an injection of Salmonella bacteria into tumours can render them ‘visible’ again.
Vital role in immune detection
The findings may help scientists create tumour-killing immune cells for injection into patients, or might prove useful in developing a potential ‘vaccine’ against cancer.
Working under laboratory conditions, the scientists found that Salmonella-infected melanoma cells from both mice and humans increased the amount of connexin 43 in the cells.
Connexin 43 is a protein that plays a vital role in immune detection of cancer cells, and this new infusion of connexin 43 spread among the tumour cells, playing its part in ‘revealing’ them and provoking an immune response.
Killed off tumours in mice
The researchers wanted to find out whether this method would work in living animals. They treated cancerous mice with Salmonella and observed that just like isolated cells in the lab, the immune cells suddenly recognised and killed tumour cells in the mice.
This approach also protected mice from cancer spreading to other parts of the body – a vaccination-style preventative strategy.
In mice, treatment with Salmonella bacteria killed off tumours and worked as a kind of ‘cancer vaccine’, preventing the spread of cancer.
If these results could be replicated for live humans, as it worked on cultured human cells, then it might be possible not only to actually destroy cancer tumours, but to vaccinate against cancer and wipe out the disease altogether.
First direct evidence provided
Rodney Scott of the University of Newcastle, Hunter Medical Research Institute Cancer Researcher of the Year 2004, said that although this was not a new concept - treating tumour cells with pathogens to provoke an immune response and destroy tumours - this was the first time anyone had provided direct evidence of the mechanism by which it took place.
He said the experiment's clear delineation of the events underlying the provoked immune response was admirable, and that the research also shed more light on the process by which tumour cells become invisible to the body’s immune system.
But the research “needs some more work” before it could lead to a genuine cancer cure. Although some melanoma patients have responded to this kind of treatment, others have not. But, Scott said, this study explains the reason for this disparity.
Further research might yield true cure
Rescigno confirmed that use of this procedure in humans was the next step. And not only will those who are treated be tumour-free, but they won’t have to worry about food poisoning, either.
“There are several strains [of Salmonella] that … don’t cause disease and can be safely used in humans,” Rescigno reported. “In fact, we already have a protocol in melanoma patients in which we inject Salmonella directly [into] the tumour.”
On how this new research would affect ordinary people, she said, “We can now generate patient-tailored therapies.”
