SCOTS scientists have made a landmark discovery that bolstering an ailing immune system – rather than correcting genetic mutations – may hold the key to preventing cancer following a major study.

The Dundee University research has the potential to revolutionise the global anti-cancer effort if the findings are substantiated in further studies.

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Currently the thrust of cancer research is geared to identifying and understanding the genetic mutations which can trigger cancer. People may be genetically predisposed to develop these mutations, or they may result from lifestyle and environmental factors such as smoking or exposure to asbestos.

Cancer risk is known to increase with age, corresponding with theories that the ageing process itself is caused by DNA "wear and tear". The traditional view is that the increased incidence of cancer with age could be understood and quantified if multiple - typically five to six - mutations in one cell are required to spark off cancer.

However, the Dundee-led study suggests that the decline in the immune system with age is a much bigger driver behind increased cancer incidence. Researchers envision it as "a war" between cancer cells and the white blood cells known as T cells which are crucial to maintaining a healthy immune system capable of fighting off disease.

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Dr Sam Palmer, who initiated the research at Dundee before taking a post at Heriot Watt University, said: “The T cells are constantly scanning for cancer cells, looking to destroy them. If they can’t find them soon enough or the immune system is weak then the cancer population has the chance to grow. The chances of this happening will increase with age as the thymus [gland where T cells are produced] is shrinking all the time.

“For our model, we imagined a war between T cells and cancer cells, which the cancer cells win if they grow beyond a certain threshold. We then set this threshold to be declining with age, proportional to T cell production. This simple hypothesis turns out to be able to explain much of the cancer incidence data.”

Dr Thea Newman, formerly Vice Principal of Research and Professor of Biophysics and Systems Biology at Dundee, added: “This is still very early days but if we are proven right then you could be talking about a whole new way to treat and prevent cancer.

“Nearly all of the mainstream research into cancer is based on how we can understand genetic mutations, target them and thereby cure the disease. We’re not debating the fact that mutations cause cancer, but are asking whether mutations alone can account for the rapid rise in cancer incidence with age when ageing causes other profound changes in the body.”

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The thymus roughly halves in size every 16 years, with a corresponding fall in the production of T cells. The researchers found an "extremely strong correlation" between the chances of certain cancers increasing and the new T cell populations falling.

Professor Clare Blackburn, an expert in thymus biology at Edinburgh University, said the findings pointed to a new hope in the fight against cancer.

She said: “This suggests we should also focus on how to boost thymus function in a controlled way, perhaps by transplantation or by controlled regeneration, so we can increase the number of T cells we are making.

"Of course, we also need to look at whether there may be unintended consequences of doing this, and how to minimise these if they occur."

The study was based on data from two million cases of cancer in patients aged 18-70. Researchers developed a mathematical equation for how they would expect cancer incidence to rise in relation to a declining immune system and compared it to the age profiles for 100 different cancers.

Their model fitted the data better than the genetic mutations hypothesis. Additionally, because the immune system generally declines more slowly in women than men, they were also able to account for the gender difference in cancer incidence, something that mutations alone cannot easily explain.

Dr Luca Albergante, formerly of Dundee and now based at the Institut Curie in Paris, said: “The increase of cancer incidence with age is slower in women, something which we would naively expect to be effectively gender-neutral. However, the thymus gland shrinks more slowly in women, so we were able to make a prediction on the differential cancer incidence with gender that once again shows our model to be more accurate than the traditional model.”

The findings are published in Proceedings of the National Academy of Sciences.