Whales Rarely Get Cancer Because of How They Evolved, Research Suggests

Genes linked to cancer suppression have been found to occur in whales, which may hint towards their generally long lives.

In a study, published by The Royal Society, scientists looked at a map of tumor-suppressing genes present in two types of whales—toothed and baleen—and then compared this to other mammals including humans.

It found that tumor suppressor genes (TSGs) occurred at a 2.4-fold higher turnover rate—defined by gene gains and gene losses combined—in cetaceans compared to other mammals. Cetaceans are the animal family to which whales and dolphins belong.

This turnover rate was even higher in baleen whales, and the researchers suggested this could be behind the evolution of cancer resistance in this species. It also may have allowed them to develop "gigantism and longevity" the study states.

"Overall, these results provide evolutionary evidence that natural selection in TSGs could act on species with large body sizes and extended lifespan, providing novel insights into the genetic basis of disease resistance."

It is not clear how the findings could help human cancer treatments, but Vincent Lynch, an assistant professor in the department of biological sciences at the University at Buffalo, New York, told New Scientist: "If you can find the genes that play a role in tumor suppression in other animals, and if you could figure out what they're doing, maybe you can make a drug that mimics that for human treatment."

Scientists have been intrigued in the past about a paradox surrounding whales and cancer. It has been called Peto's paradox, named after the epidemiologist Richard Peto who observed the relationship between cancer and time.

Whales are known for their vast size, and the bigger an animal is, the more cells are required to build their bodies. The more cells there are in a body, the more likely it is that one of them will become cancerous.

In addition, cetaceans are some of the longest-lived animals on the planet. Some whales have been found to live for as long as 200 years.

Large animal size and long length of life should both be risk factors in terms of developing cancer, according to a 2017 study on the matter published in the journal BMC Biology.

It reads: "Large bodied and long-lived organisms should face a higher lifetime risk of cancer simply due to the fact that their bodies contain more cells and will undergo more cell divisions over the course of their lifespan."

"However, a 2015 study that compared cancer incidence from zoo necropsy data for 36 mammals found that a higher risk of cancer does not correlate with increased body mass or lifespan."

This phenomenon has also been shown in other large animals such as elephants, which do not develop cancer at a rate higher than humans do.

Whale jumping
A humpback whale jumps out of the Pacific Ocean's waters in Los Cabos, Baja California Sur, Mexico on March 14, 2018. Scientists studied toothed and baleen whales in the report. Fernando Castillo/AFP/Getty