Pancreatic cancer is known to be very deadly because it has a tendency to spread, or metastasis, to other parts of the body before the symptoms of the disease appear. In previous work in mice, Claudia Gravekamp of the Albert Einstein College of Medicine in New York has been able to show that weakened listeria bacteria fight against tumour tissue but not healthy tissue. Further to that, the bacteria seem to home in on the metastatic tumours.
To take advantage of this and make the most of the opportunity to do some damage to cancer, her team have now armed the bacteria with a radioactive payload – attaching the isotope rhenium-188 to the listeria with a form of antibody.
They gave mice different degrees of human pancreatic tumours and then injected them every day with the powered-up bacteria for a week, giving them a week off before four more days of treatment injections. A few days later, there were on average 90 per cent fewer of the tumours in this group than there were in untreated mice, and the average weights of original pancreatic tumours had decreased by 64 per cent.
After a week, the animals’ livers and kidneys had completely cleared themselves of the radioactive bacteria from their systems, with no damage to either organ. This was a very important aspect of study as there would be no use treating the cancer only to poison the body with something else.
Gravekamp believes that the radiation affected the metastatic tumours most because cells there were still rapidly multiplying, leaving their chromosomes more vulnerable to damage than those in healthy tissues or in the original tumour. The bacteria also play a part by producing reactive oxygen molecules that again damage the tumour’s DNA.