The rules of nature tell us that large, long-lived animals should have the highest risk of cancer. The calculation is simple: Tumors grow when genetic mutations cause individual cells to reproduce too quickly. A long life creates more opportunities for those cancerous mutations to arise. So, too, does a massive body: Big creatures — which have many more cells — should develop tumors more frequently. Why, then, does cancer rarely afflict elephants, with their long lifespans and gargantuan bodies? Scientists went looking for the answer…
The first discovery was that elephants possess extra copies of a wide variety of genes associated with tumor suppression. But this phenomenon is not unique to elephants, so they pressed on for more information…
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“One of the expectations is that as you get a really big body, your burden of cancer should increase because things with big bodies have more cells. The fact that this isn’t true across species — a long-standing paradox in evolutionary medicine and cancer biology — indicates that evolution found a way to reduce cancer risk.”
-Vincent Lynch, PhD, assistant professor, Department of Biological Sciences, University at Buffalo College of Arts and Sciences
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The research concluded that duplication of tumor suppressor genes is quite common among elephants’ living and extinct relatives, including in small ones like Cape golden moles (a burrowing animal) and elephant shrews (a long-nosed insectivore). The data suggest that tumor suppression capabilities preceded or coincided with the evolution of exceptionally big bodies, facilitating this development.
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“We found that: Elephants have lots and lots and lots of extra copies of tumor suppressor genes, and they all contribute probably a little bit to cancer resistance.”
-Vincent Lynch, PhD, assistant professor, Department of Biological Sciences, University at Buffalo College of Arts and Sciences
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The final analysis: Elephants do have enhanced cancer protections, compared with relatives. Though many elephant relatives harbor extra copies of tumor suppressor genes, the scientists found that elephant genomes possess some unique duplications that may contribute to tumor suppression through genes involved in DNA repair; resistance to oxidative stress; and cellular growth, aging and death.
Journal Reference: Juan M Vazquez, Vincent J Lynch. Pervasive duplication of tumor suppressors in Afrotherians during the evolution of large bodies and reduced cancer risk. eLife, 2021; 10 DOI: 10.7554/eLife.65041
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