For many years, researchers have been intrigued by a fascinating phenomenon known as Peto’s Paradox. Theoretically, larger animals with longer lifespans should experience increased cancer occurrences due to having more cells and extended time for mutations. However, creatures like elephants, whales, and other massive animals seem to develop cancer significantly less frequently than humans.
Currently, scientists are uncovering the reasons behind this. A study conducted in 2015 revealed that elephants possess 19 additional copies of a potent cancer-inhibiting gene known as TP53. This gene functions as a genetic protector, identifying DNA damage and initiating cell death in potentially cancerous cells. For elephants, this augmented genetic defense likely accounts for their remarkably low cancer rates despite their size.
Nonetheless, recent research has expanded this inquiry to nearly 300 animal species. The scientists examined over 16,000 necropsy records and discovered that elephants are not unique in this regard. Numerous other species have developed their own cancer resistance mechanisms.
Certain birds, bats, and even lizards exhibited surprisingly low cancer rates, while animals such as ferrets and opossums displayed significantly higher rates. The study also illuminated how different traits impact cancer risk, and this correlation isn’t solely tied to the number of copies of the cancer-suppressing gene in an animal’s genome.
A larger body mass was associated with a slightly increased likelihood of cancer development, but the connection was not as robust as anticipated. Extended gestation periods seemed to reduce cancer risk, possibly due to improved cellular protections that emerge during prolonged fetal development. However, the researchers noted that animals in captivity did not exhibit unnaturally high cancer incidence as a result of living longer than their wild counterparts.
What implications does this hold for human cancer research?
TP53 is already a significant factor in human cancer prevention and evaluating cancer risks, yet humans possess only two copies of this gene. Understanding how elephants and other species bolster their cancer defenses may pave the way for innovative cancer treatments that enhance the resilience of human cells.
