Yorkshire scientists in ‘cancer vaccine’ discovery

The work focuses on harnessing the immune system to attack and kill tumours in cancer patients, as it does with ordinary infections.

Experts have already established that by genetically engineering viruses with specific proteins made by cancer cells, they can stimulate a response from the immune system which is fooled into attacking and destroying tumours.

But concerns have been raised the immune system could go into overdrive and attack healthy tissues, which also produce the same proteins, limiting the range of DNA which can be used.

Now scientists in Leeds University, working with the world-renowned Mayo Clinic in the United States, have successfully used a vaccine in laboratory studies which employs a whole range of proteins to trigger an immune response – but without overstimulating it. Early work using what is being described as a “library of DNA” could open the way to the further development of gene therapy vaccines against cancer.

Prof Alan Melcher, author of the study at the Cancer Research UK Centre in Leeds, said the immune system had evolved to attack certain threats such as viruses but evidence showed tumours were able to escape becoming a target.

“What we are trying to do is harness and use the immune system to attack cancer,” he said.

By smuggling harmless viruses into the body which had been genetically engineered to make proteins, known as antigens, it was hoped to fool the immune system into targeting cancer cells.

“When we vaccinate with this virus, these antigens get made which the immune system recognises and attacks and because the cancer also makes these antigens, when the immune system is stimulated in this way it is stimulated to attack the tumour,” he said.

In the study, experts took DNA harvested from healthy prostate tissue in mice. This had been inserted into a virus and then injected into mice infected with prostate cancer.

This triggered an immune response which attacked the cancer cells but, importantly, did not overstimulate the immune system and attack healthy cells in other parts of the mice.

Prof Melcher said it was the first time a whole library of DNA had been used in a viral vaccine successfully. “The biggest challenge in immunology is developing antigens that can target the tumour without causing harm elsewhere.

“By using DNA from the same part of the body as the tumour, inserted into a virus, we may be able to solve that problem. There has been quite a lot in the past about using the immune system with gene therapy but it has tended to only use very few antigens to stimulate the immune response.

“What we have done here is to take a whole library of DNA from a tissue within which there are lots and lots of different antigens, put that library into a virus and use that as a vaccine.

“In the experiments we have done to date we have not seen a problem with over activation of the immune system causing toxicity or side effects from this virus DNA library approach.”

He added: “It is very early days in terms of applying this to patients.

“What we can say is that viruses similar to the one we have used here have been used in trials and are looking quite promising so the platform is there and appears safe and deliverable so I think there is reason for optimism that this particular vaccine approach can be a future development of current virus-based treatments.”

Prof Peter Johnson, chief clinician at the charity Cancer Research UK, said: “This is an interesting and significant study which could really broaden out the field of immunotherapy research.”