As the constant struggle to find a cure for cancer goes on and on in the medical world, it’s no surprise that scientists have been studying organisms across the animal kingdom, and therefore it wasn’t long before the phenomenon of Peto’s paradox was discovered.
Cancer is caused by damage to the DNA of a cell or cells in an organism, which causes disruption to the cell cycle, and constantly causes the abnormal, uncontrolled growth of a mass of cells which we know as a tumour. Given that cancer can arise from any cell, it would follow that organisms with a larger number of cells would experience cancer at an increased rate, yet it seems this is not the case. Whilst one in four people with cancer will die from it, only around one in twenty five elephants who have cancer will die, and the occurrence of cancer in elephants is significantly lower than in humans, so what is their secret, as surely an organism with 100x the number of cells should experience cancer 100x more frequently.
So what is their secret, decreased exposure to carcinogens? Skin better at preventing harmful UV light penetrating and damaging their skin? No, it all comes down to the tumour suppressor gene, p53, of which humans have 2 copies, and some elephants have as many as 40. The function of the p53 gene is to activate a protein which either stops cell division and repairs corrupted DNA, or induces the process of apoptosis – cell suicide. It also has the ability to limit blood flow to tumours to halt growth and can alert nearby immune cells to attack the tumour. Because elephants have so many copies of this gene, it appears that they are very good at tackling tumours and consequently cancer caused deaths are very much a rarity for elephants.
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