Cancer begins as a mutation in a single cell. Organisms with more cells should therefore have a higher risk of developing it. Elephants, which have 100 times as many cells as human beings. Whales, with ten times more again, should be barnacled with tumors. In fact, the planet’s behemoths are blessed with extremely low rates of cancer.. The secret of suppressing cancer may therefore be hidden in the genes of giants.
Elephants. These have a cancer-mortality rate of about 5%, compared with 11-25% in human populations. Some participants in the whale study were previously involved in sequencing African and Asian elephant genomes. They found that an important weapon in the elephants’ arsenal is tp53, a gene that encodes an apoptosis-inducing protein called p53. This protein is known colloquially as “the guardian of the genome”.
Human beings have two copies of tp53 in their chromosomes—one from each parent. Those in whom one of these does not work manifest a condition called Li-Fraumeni syndrome, and are almost certain to develop cancer. Elephants’ chromosomes, by contrast, sport 40 versions of tp53—part of the explanation, surely, of why elephant tumours are so rare.
Joshua Schiffman, a paediatric oncologist at the Huntsman Cancer Institute in Utah who was involved in the elephant study, is investigating how elephants’ multiple copies of tp53 co-ordinate an attack on mutated cells. He is also studying how slight differences in the composition of elephant p53 make it a more efficient mutant-cell killer than its human counterpart. The power of elephant p53 led Dr Schiffman to co-found peelTherapeutics, based in Utah and Israel (the firm’s name is derived from the Hebrew word for elephant). peel’s purpose is to translate discoveries in comparative oncology into human patients. The firm’s researchers are experimenting with minuscule lipid spheres loaded with proteins, including synthetic elephant p53. Their most promising experimental drug is designed to deliver this directly to a patient’s tumour cells. Details are still under wraps, but Dr Schiffman says that, in a laboratory, introducing synthetic elephant p53 to human cancer cells induces “incredibly rapid and robust cell death”.
Researchers are looking at cancer rates in 13,000 animal species, using more than 170,000 records of individual animals. This study is the first of its kind, and is intended to search for patterns that might explain resistance and susceptibility to tumours.
One novel aspect of all this research is its willingness to take the animals under study on their own terms. Medical science uses animals a lot—but almost always they are there to act as stand-ins for human beings.
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