Elephants have 100 times more cells than humans. But they rarely get cancer. Cancer is caused by faulty cell division, and the more cells there are, the more likely some are to mutate into tumors. And elephants have a long lifespan. It is surprising that elephants, which have a large number of cells and long-lived animals, rarely get cancer.
The intuitive observation that cancer risk is not always related to the size or lifespan of a species is known as Peto’s Paradox, named after the British epidemiologist Richard Peto, who first mentioned this phenomenon in 1977. Cancer does not occur equally in all living things. Some animals have evolved powerful ways to prevent diseases, and others are very vulnerable to diseases.
A few years ago, Joshua Schiffman, M.D., a pediatric oncologist at the Huntsman Cancer Institute, University of Utah School of Medicine, discovered 40 TP53 genes in elephants that inhibit tumor cells before cancer grew and spread. In comparison, humans and most other animals have only two TP53 genes. Schiffman and research partner Carlo Maley said many of these inhibitory genes seem to give elephants a powerful ability to protect mutant cells.
Scientists have long known that TP53 helps kill malignant cells before they can be transformed into tumors. However, Schiffman and Marley found in their studies that no animal has 40 genes and that elephants appear to have made a unique evolution to fight cancer.
The elephant story represents one way that evolution may have overcome cancer. Other evidence suggests that naked mole rats and bowhead whales have evolved different approaches to the problem.
Scientists are working on ways to apply the results obtained through elephants to fight cancer in humans.