Whales should have a greater risk of developing cancer than humans because they are bigger and have more cells. In fact, whales are some of the animals least likely to get cancer. The answer is in their genes, according to a new study.
Cancer should be a near certainty for whales, being the longest-living and largest mammals there are. Across species, the higher the number of cells, the greater the number of cell divisions and the higher the probability of DNA damage and the transformation of a normal cell into a cancerous one.
However, the occurrence of cancer does not show a correlation with body mass. The lack of correlation between body mass and cancer risk is known as Peto’s paradox.
Whales have developed mechanisms against diseases such as cancer, although the underlying molecular bases of these remain unknown. Now, it has been found they have a gene duplication that appears to slow the division of cells, allowing the whales to live longer—but at the cost of reduced male fertility.
A study led by Daniela Tejada-Martinez, a postdoctoral researcher at Thomas Jefferson University in Philadelphia, investigated the evolution of tumour suppressor genes (TSGs), in the ancestor of cetaceans, as well as in baleen and toothed whales. TSGs are considered among the most important anti-cancer responses in the body.
Cancer happens precisely when the TSGs are not working properly.
The study showed that over the course of evolution in cetaceans, genes involved in the control of cancer onset were duplicated many times and progression was positively selected. It also found that cetaceans have a 2.4 times faster turnover rate of tumour-suppressing genes than other mammals.