Cancer vaccine hopeGene therapy vaccine to treat prostate cancer
A new type of cancer vaccine has been used to successfully treat prostate tumours in animals.
The gene therapy vaccine cured 80 per cent of mice with the disease, and only attacked prostate cancer cells, while leaving healthy tissue unharmed.
The scientists from Leeds University and the Mayo Clinic used a "completely new approach" to create the vaccine.
Traditional vaccines are given to healthy people to prevent them developing an infection.
Potential cancer "vaccines" are a type of immunotherapy or gene therapy, and work by making cancer patients' immune systems attack tumours which are already there.
Cancer vaccines have within them a single gene related to the cancer it is aiming to destroy. The gene is responsible for producing a protein, known as an antigen, which triggers the immune system to seek out and destroy cancer cells with the same antigen.
One of the many hurdles faced by cancer researchers is finding an antigen which is unique to the cancerous tumour which could be incorporated into a vaccine.
The scientists worked round this by creating a "library" of many bits of DNA from healthy human prostate tissue. As the library contained so many fragments of DNA, it was likely that it contained many possible antigens each of which could trigger the immune system.
The DNA was then inserted into a virus and cultured in the laboratory. The genetically altered virus, now the vaccine, was then injected into mice with prostate cancer.
The vaccinated animals produced an immune response which attacked the prostate tumours but left healthy tissue unharmed.
Scientists feared that using multiple genes in a vaccine would send the immune system into overdrive which would be too strong for the body to cope with. However, using a range of DNA meant that the vaccine targeted the tumour through many routes, the researchers said.
As the DNA was isolated from the same organ as the tumour, the immune system self-selected which cancer antigens it responded to, while ignoring healthy parts of the body.
Study leader Professor Richard Vile of the Mayo Clinic said: "Nobody really knows how many antigens the immune system can really see on tumour cells.
"By expressing all of these proteins in highly immunogenic viruses, we increased their visibility to the immune system.
"The immune system now thinks it is being invaded by the viruses, which are expressing cancer-related antigens that should be eliminated."
This approach could be used in the treatment of many aggressive cancers, such as lung, brain and pancreatic cancer.
Professor Peter Johnson, chief clinician at Cancer Research UK, which helped fund the research, 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."
The researchers think the same approach could also be used to treat aggressive cancers such as lung, brain and pancreatic cancer.
The study is published in the journal Nature Medicine
This article was published on Mon 20 June 2011
Image © Alexander Raths - Fotolia.com
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