Cancer involves the uncontrolled growth of cells, forming tumors that disrupt bodily functions. For animals of immense size and longevity, like whales, a key question is whether they also develop cancer.
Do Whales Get Cancer?
Despite their colossal size and extended lifespans, whales can get cancer. However, the incidence in these marine giants is remarkably low, especially considering their vast number of cells. Evidence suggests they are susceptible to various malignancies affecting different tissues. This low incidence makes whales a subject of significant scientific interest.
The Paradox of Large Size
The study of cancer in whales highlights Peto’s Paradox. This paradox notes that larger, longer-lived animals do not necessarily have a higher cancer incidence, defying the intuitive expectation that more cells and a longer lifespan increase mutation chances. If cancer risk were proportional to cell count and lifespan, a blue whale, with trillions of cells and over 80 years of life, should theoretically develop cancer constantly. Yet, whales show a far lower cancer rate than predicted.
This challenge makes whales particularly interesting to researchers. Richard Peto first noted this discrepancy in the late 1970s, observing that humans, despite more cells and longer lives than mice, lack a proportionally higher cancer rate. The existence and successful reproduction of large, long-lived species like whales suggests they possess effective natural cancer suppression mechanisms. Understanding how these animals overcome risks associated with their size and longevity is a focus of comparative oncology.
Mechanisms of Cancer Resistance
Researchers investigate the biological mechanisms allowing whales to resist cancer. One area of focus is enhanced DNA repair. Studies on bowhead whales, known for longevity, show their cells efficiently repair DNA damage, including double-strand breaks. This repair system is supported by elevated levels of proteins like CIRBP and RPA2, which improve DNA repair fidelity and efficiency.
Another potential adaptation involves tumor suppressor genes. While whales lack the numerous TP53 gene duplications seen in elephants, their genomes show other evolutionary changes linked to cancer resistance. Whales exhibit duplications in various tumor suppressor genes and accelerated evolution in genes related to cell cycle control, signaling, and proliferation. These genomic adaptations suggest whales evolved multiple strategies, including robust DNA repair and sophisticated cell cycle regulation, to prevent uncontrolled cell growth.
Implications for Human Health
Studying cancer resistance in whales offers valuable insights for human health. By uncovering the unique anti-cancer mechanisms in these large, long-lived species, scientists hope to identify novel targets for cancer prevention and therapy. Adaptations found in whale genomes, such as enhanced DNA repair and specific gene duplications, could inform new drug or treatment strategies.
Comparative oncology, the study of cancer across different species, allows researchers to learn from nature’s solutions. Understanding how organisms like whales evolved to suppress cancer over millions of years provides a unique perspective beyond human-centric research. This research holds the promise of leading to more effective ways to combat cancer in humans.