It would seem logical that large, long-lived organisms would have a greater chance of developing cancer than small, short-lived organisms - if every cell has a chance of becoming cancerous there is a greater probability that a tumour will form. However scientists have been studying the lack of this correlation in animals, known as Peto’s Paradox, as it has been shown that only 5% of elephants die from cancer compared to up to 25% of humans, despite having 100 times more cells than us! According to Cancer Research UK, 1 in 2 people will survive cancer for ten or more years meaning that the rarity of cancer in elephants offers a fascinating route of research into the prevention of this virulent disease.
Cancer is a condition where cells mutate and divide in an uncontrolled way due to a disruption in the signals controlling how much and often cells divide, resulting in the formation of a growth called a tumour. Mutations occur independently in everybody over time; some mutations are harmless but some can offer a reproductive advantage over other cells by increasing the rate of replication. As a tumour grows it switches from being benign to malignant and gains the ability to invade healthy tissue. Metastasis can also occur where cancer cells from the primary site enter the bloodstream or lymphatic system; here they can spread to other parts of the body and form a secondary tumour. Many strains of research are currently looking at how to control the growth and spread of cancer. What is exciting is that this research into elephants and cancer offers a potential pathway into tackling the very initial stages of cancer.
So what makes the occurrence of cancer so rare in elephants? Scientists have recently discovered that it is due to the presence of multiple copies of the gene that code for the p53 protein in elephant cells. This particular multifunctional protein is part of a group called ‘tumour suppressor proteins’, the roles of which are to stop the uncontrolled proliferation of cells by sensing DNA damage and contributing to the formation genes which check for abnormalities in the cell cycle. Humans only inherit one copy of the p53 from each parent, whereas it has been found from analysing blood samples that African elephants have at least 20 copies of the p53 gene from each parent. For cancer to occur, both copies within a cell must be mutated and be unable to function correctly, therefore it holds that it is far more likely for humans to develop cancer.
Additionally, further research has highlighted the link between the numbers of working copies of the p53 gene in a cell and the cell’s response to DNA damage. Experiments with elephant cells showed that radiation damage doubled the likelihood that the cells would die. This is an important evolutionary mechanism as it is beneficial for the body to kill cells with damaged DNA before they can multiply and form a tumour. This strategy displayed by elephants is of particular interest to cancer researchers as it could be have applications in the field of cancer prevention.
Scientists are currently exploring biomimicry (imitating biological designs, structures and systems) by attempting to emulate the elephant’s success in lowering the risk of cancer. A team at the University of Utah has plans to screen a wide variety of compounds which are designed to produce the same effect as the large number of p53 copies in elephants- programming cell death instead of repair in the event of DNA damage. The insertion of elephant’s p53 copies into human cells as a form of cancer prevention is also in the research pipeline.
These potential applications of p53 research are in the very early stages of medical science but demonstrate the exciting progress in the field of oncology. However in the meantime we could take a leaf out of an elephant’s book and battle the prevalence of cancer by cutting down on the bombardment of environmental stressors we place on our bodies such as toxins from cigarettes and alcohol. Cancer cases show that smoking is the most preventable cause of cancer accounting for more than 1 in 4 UK cancer deaths so the next time someone offers you a cigarette in the smoking area perhaps take a moment to think ‘What would an elephant do?!’.