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Galapagos giant tortoises are long-lived in part because their cells are surprisingly sensitive to certain forms of stress. As well as informing research into human medicine, the finding reveals how animals have evolved different ways to resist cancer and ageing.

鈥�There鈥檚 lots of different ways to get to a large body and a long, healthy lifespan,鈥� says at the University at Buffalo, New York.

We would expect large animals to be more susceptible to cancer because they have a greater number of cells, each of which has a small chance to become cancerous. But recent studies have shown how big, long-lived animals such as elephants experience paradoxically low cancer rates by having extra copies of genes involved in suppressing tumour development.

These studies have mostly been done in mammals, raising the question of how other animals have evolved similar adaptations. So Lynch and his colleagues turned to turtles, which come in a large range of body sizes, have lower rates of cancer and can show remarkable longevity. Galapagos giant tortoises, for example, can live for more than 150 years.

Lynch鈥檚 team found that Galapagos giant tortoises have evolved a marked reduction in cancer risk, and that their genomes contain extra copies of genes involved in responding to cellular stress caused by damaged or misshaped proteins. The accumulation of such proteins in cells has been associated with ageing and cancer.

When the researchers applied a drug that triggers this kind of stress to giant tortoise cells in a lab dish, they were surprised to see that the cells immediately self-destructed. 鈥淲e thought that they might be super resistant to the kinds of stresses that cause cancer, but it ends up that they鈥檙e very sensitive,鈥� says Lynch. Killing damaged cells before they turn cancerous protects the animal from developing tumours, he says, adding that this is likely to be just one of many ways in which giant tortoises reduce their risk.

鈥淚t鈥檚 a very original and interesting study,鈥� says at the University of Liverpool, UK. 鈥淭he more species we learn tricks from, the greater our understanding will be of natural mechanisms that confer resistance to ageing and cancer.鈥�

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