New approach to cancer vaccines proves successful in early studies

University of Leeds researchers, funded by Cancer Research UK, have used a library of DNA to create a vaccine that could be used to treat cancer, according to a study published in Nature Medicine.

Before now, ‘gene therapy’ vaccines have often delivered just one gene to stimulate the immune system. It produces a protein, called an antigen, which activates the immune system to destroy cancer cells.

It has been difficult to develop successful cancer vaccines because each tumour has specific proteins and identifying the right antigens has been a huge challenge.

Scientists have also tried to boost the effectiveness of vaccines by using several genes to increase the chances of producing successful antigens. But a worry has always been that the immune system’s response would be too strong for the body to handle.

But now researchers, working with the Mayo Clinic in Rochester, US, have solved this problem in experiments involving mice.

The team used doses of a vaccine made from a virus which contained a ‘library’ of DNA, containing multiple fragments of genes and therefore many possible antigens. This approach did not send the immune system into overdrive, which had been a concern. Instead the range of DNA meant the vaccine was able to target the tumour through many routes.

Importantly, the DNA library was harvested from the same organ as the tumour. This meant that the immune system ‘self-selected’ the cancer antigens to respond to and did not react against other healthy parts of the body. Also, the process of self-selection was triggered when the vaccine was injected into the bloodstream, an approach to vaccination that is far more practical than injecting directly into tumours.

The researchers delivered a library of DNA taken from healthy prostate tissue in mice. When delivered in a virus, the vaccine successfully treated mice with prostate cancer.

University of Leeds’ Professor Alan Melcher, co-author of the study, said: “This is the first time we’ve been able to use a whole library of DNA 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.”

The vaccine was made by putting the DNA library inside a vesicular stomatitis virus (VSV), which stimulates an immune response that can then track down and kill tumour cells.

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

“Although the vaccine didn’t trigger the immune system to overreact and cause serious side effects in mice, it will need to be further developed and tested in humans before we can tell whether this technique could one day be used to treat cancer patients.”

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The study was funded by the US National Institutes of Health, Cancer Research UK, The Richard M. Schulze Family Foundation, Mayo Clinic, and a private grant.

For more information:

Contact: Paula Gould, University of Leeds Communications & Press Office: Tel +44 (0)113 343 8059, email .(JavaScript must be enabled to view this email address)

Notes to editors:

1. A copy of the paper is available on request (Broad Antigenic Coverage Induced by Viral cDNA Library-based Vaccination Cures Established Tumors. Kottke et al. Nature Medicine. 19 June 2011. DOI 10.1038/nm.2390).

2. Listen to Professor Alan Melcher talking about the research here: http://url.health.am/348/

3. One of the UK’s largest medical, health and bioscience research bases, the University of Leeds delivers world leading research in medical engineering, cancer, cardiovascular studies, epidemiology, molecular genetics, musculoskeletal medicine, dentistry, psychology and applied health. Treatments and initiatives developed in Leeds are transforming the lives of people worldwide with conditions such as diabetes, HIV, tuberculosis and malaria.

4. Cancer Research UK is the world’s leading cancer charity dedicated to saving lives through research.

  * The charity’s groundbreaking work into the prevention, diagnosis and treatment of cancer has helped save millions of lives. This work is funded entirely by the public.
  * Cancer Research UK has been at the heart of the progress that has already seen survival rates double in the last forty years.
  * Cancer Research UK supports research into all aspects of cancer through the work of over 4,000 scientists, doctors and nurses.
  * Together with its partners and supporters, Cancer Research UK’s vision is to beat cancer. For further information about Cancer Research UK’s work or to find out how to support the charity, please call 020 7121 6699