Latest news with #Peto'sParadox
Sydney Morning Herald
20-05-2025
- Health
- Sydney Morning Herald
At 2m tall, I'm at greater risk of cancer. An elephant could fix that
Kean spoke to researchers scouring the genomes of large animals for clues as to why they're so good at suppressing cancer despite having trillions more cells than we do. Some of what they've found can make human cancer cells self-destruct. 1000 times better at cancer suppression Body size and cancer rates only correlate between members of the same species, not between different animals. For example, little dogs such as Pomeranians, shih tzus and chihuahuas have a 10 per cent chance of dying from cancer while the risk for larger breeds including mastiffs and Burmese mountain dogs is up around 40-50 per cent, a 2024 study reported. If this correlation between size and cancer risk applied across different species, mice would never die from cancer and elephants would barely make adulthood. By one estimate, half of all blue whales should get colon cancer by the time they're 50 and all whales should have it by the time they're 80. But that's not the case. Mice actually have a colon cancer risk comparable to humans, even though they're tiny. About 46 per cent of wild mice raised in a lab, in fact, die from some kind of cancer. Blue whales do get colon cancer but at nowhere near the rates you'd expect for their size. They live as long as we do. So what's going on? 'Peto's Paradox suggests that large, long-lived animals such as the blue whale have evolved mechanisms capable of suppressing cancer 1000 times better than humans,' write Professor Carlo Maley and Dr Aleah Caulin in Trends in Ecology & Evolution. If we could harness the cancer-suppression mechanisms of mega-animals, they argue, 'then we could potentially eradicate cancer as a public health threat in humans'. Peto's paradox disproved? Just as I got excited about the idea of using the cancer-suppressing superpowers of the world's largest creatures to treat human cancer, I came across a new paper that slapped me down. No evidence for Peto's paradox in terrestrial vertebrates, the headline read. The authors analysed a dataset of 16,000 necropsy records for 292 species of mammals, amphibians, birds and reptiles and found larger animals did get more cancer. 'We show that there is no evidence for Peto's paradox across amphibians, birds, mammals and squamate reptiles: Larger species do in fact have a higher cancer prevalence compared to smaller species,' they concluded. But other scientists quickly questioned that blunt conclusion. Although the authors did find more cancer in bigger animals, it wasn't enough to disprove Peto's paradox. Most large-bodied animals still had far lower cancer rates than you'd expect. Elephants, for example, had 56 per cent less cancer than the researchers' model predicted. 'The real question is not just whether there is a positive relationship between size and cancer prevalence, but whether this relationship is as strong as expected given the increased number of cell divisions associated with larger body size,' says Dr Antonie Dujon, who's researching cancer and evolution at Deakin University. 'In other words, there may be a positive correlation between size and cancer risk, but if this correlation is weaker than statistically expected, it suggests that natural selection has nonetheless favoured superior anti-cancer defences in large-bodied species.' So, despite the headline, Peto's paradox held up. Scientists remain convinced something powerful is going on within the world's biggest creatures that stops cells going rogue. Here's one way scientists are trying to use that to our advantage. Harnessing elephant evolution to kill cancer Large animals may have evolved to suppress cancer through lower mutation rates, cancer-resistant tweaks in the architecture of their tissue, and immune systems better at surveilling for cancerous cells. One specific example comes from elephants. Circling back to Kean's book about evolution, she writes that humans have an inbuilt defence against tumours in the form of a gene called TP53. Loading The gene codes for a protein called P53 that triggers cancerous cells to 'self-destruct' and repairs damaged DNA. Humans have two copies of the gene in each cell. But elephants, the largest land animals, have 40 copies. The elephant versions are seemingly more powerful at suppressing cancer than the human version of the gene, too. Only 5 per cent of elephants die from cancer compared to a quarter of humans. Now several teams across the globe are scrutinising these elephant genes with a long-term view of harnessing them for targeted cancer therapies. It's very, very early days for this research, but scientists have used the genes to kill the cells of a cancerous bone tumour that affects children during growth spurts.
The Age
20-05-2025
- Health
- The Age
At 2m tall, I'm at greater risk of cancer. An elephant could fix that
Kean spoke to researchers scouring the genomes of large animals for clues as to why they're so good at suppressing cancer despite having trillions more cells than we do. Some of what they've found can make human cancer cells self-destruct. 1000 times better at cancer suppression Body size and cancer rates only correlate between members of the same species, not between different animals. For example, little dogs such as Pomeranians, shih tzus and chihuahuas have a 10 per cent chance of dying from cancer while the risk for larger breeds including mastiffs and Burmese mountain dogs is up around 40-50 per cent, a 2024 study reported. If this correlation between size and cancer risk applied across different species, mice would never die from cancer and elephants would barely make adulthood. By one estimate, half of all blue whales should get colon cancer by the time they're 50 and all whales should have it by the time they're 80. But that's not the case. Mice actually have a colon cancer risk comparable to humans, even though they're tiny. About 46 per cent of wild mice raised in a lab, in fact, die from some kind of cancer. Blue whales do get colon cancer but at nowhere near the rates you'd expect for their size. They live as long as we do. So what's going on? 'Peto's Paradox suggests that large, long-lived animals such as the blue whale have evolved mechanisms capable of suppressing cancer 1000 times better than humans,' write Professor Carlo Maley and Dr Aleah Caulin in Trends in Ecology & Evolution. If we could harness the cancer-suppression mechanisms of mega-animals, they argue, 'then we could potentially eradicate cancer as a public health threat in humans'. Peto's paradox disproved? Just as I got excited about the idea of using the cancer-suppressing superpowers of the world's largest creatures to treat human cancer, I came across a new paper that slapped me down. No evidence for Peto's paradox in terrestrial vertebrates, the headline read. The authors analysed a dataset of 16,000 necropsy records for 292 species of mammals, amphibians, birds and reptiles and found larger animals did get more cancer. 'We show that there is no evidence for Peto's paradox across amphibians, birds, mammals and squamate reptiles: Larger species do in fact have a higher cancer prevalence compared to smaller species,' they concluded. But other scientists quickly questioned that blunt conclusion. Although the authors did find more cancer in bigger animals, it wasn't enough to disprove Peto's paradox. Most large-bodied animals still had far lower cancer rates than you'd expect. Elephants, for example, had 56 per cent less cancer than the researchers' model predicted. 'The real question is not just whether there is a positive relationship between size and cancer prevalence, but whether this relationship is as strong as expected given the increased number of cell divisions associated with larger body size,' says Dr Antonie Dujon, who's researching cancer and evolution at Deakin University. 'In other words, there may be a positive correlation between size and cancer risk, but if this correlation is weaker than statistically expected, it suggests that natural selection has nonetheless favoured superior anti-cancer defences in large-bodied species.' So, despite the headline, Peto's paradox held up. Scientists remain convinced something powerful is going on within the world's biggest creatures that stops cells going rogue. Here's one way scientists are trying to use that to our advantage. Harnessing elephant evolution to kill cancer Large animals may have evolved to suppress cancer through lower mutation rates, cancer-resistant tweaks in the architecture of their tissue, and immune systems better at surveilling for cancerous cells. One specific example comes from elephants. Circling back to Kean's book about evolution, she writes that humans have an inbuilt defence against tumours in the form of a gene called TP53. Loading The gene codes for a protein called P53 that triggers cancerous cells to 'self-destruct' and repairs damaged DNA. Humans have two copies of the gene in each cell. But elephants, the largest land animals, have 40 copies. The elephant versions are seemingly more powerful at suppressing cancer than the human version of the gene, too. Only 5 per cent of elephants die from cancer compared to a quarter of humans. Now several teams across the globe are scrutinising these elephant genes with a long-term view of harnessing them for targeted cancer therapies. It's very, very early days for this research, but scientists have used the genes to kill the cells of a cancerous bone tumour that affects children during growth spurts.
