10-Year Study Challenges Peto’s Paradox on Cancer Resistance in Vertebrates

Estimated reading time: 4 minutes

Cancer is a leading cause of death worldwide, yet its prevalence varies significantly across species. A groundbreaking 10-year study by Arizona State University has analyzed cancer prevalence in 292 vertebrate species, using over 16,000 necropsy records. The research challenges Peto’s paradox, which posits that larger animals should have higher cancer rates due to their greater number of cells and longer lifespans. Instead, the findings reveal that large animals have evolved effective cancer suppression mechanisms, offering new insights into the complex relationship between body size, longevity, and cancer resistance.

Key Findings
The study found that while cancer rates do increase with body size, the increase is minimal, suggesting that larger animals have developed robust mechanisms to suppress cancer. For example, elephants and whales, despite their massive size, exhibit low cancer rates, likely due to multiple copies of cancer-suppressing genes like TP53.

Cancer prevalence was also found to decrease with longer gestation periods, indicating that better cell regulation and reduced high-impact mutations during development may play a role in cancer resistance. Species such as the common porpoise and black-footed penguin showed remarkably low cancer rates, potentially offering clues for cancer prevention in humans. Conversely, species like ferrets and opossums exhibited high cancer rates, possibly due to shorter life cycles and less evolutionary pressure to develop cancer defenses.

The study also highlighted differences in cancer prevalence across animal groups. Mammals had the highest cancer rates, followed by reptiles, birds, and amphibians, underscoring the link between an animal’s biological traits and its cancer risk.

Methodology
Researchers analyzed necropsy records from over 16,000 individuals across 292 vertebrate species, spanning mammals, reptiles, birds, and amphibians. They examined the relationship between body size, lifespan, gestation periods, and cancer prevalence.

To understand the mechanisms behind cancer resistance, the team conducted DNA damage response assays, studying how different species react to radiation and chemotherapy. These assays focused on processes such as cell cycle arrest and apoptosis. While the responses varied among species, they did not directly correlate with cancer prevalence, suggesting that other factors, such as immune function and metabolic processes, may play a more significant role in cancer resistance.

Strengths and Limitations
One of the key strengths of this study is its extensive dataset, encompassing a wide range of vertebrate species and providing a comprehensive overview of cancer prevalence across the animal kingdom. The findings challenge long-standing assumptions about cancer risk and body size, offering new avenues for research into cancer suppression mechanisms.

However, the study has some limitations. While it identifies correlations between species traits and cancer prevalence, it does not establish causation. Additionally, the mechanisms underlying cancer resistance in certain species remain poorly understood and require further investigation. The study also relies on necropsy records, which may not capture all cases of cancer, particularly in wild populations.

Implications and Future Directions
The findings have significant implications for cancer research and prevention. By studying species with low cancer rates, such as elephants and whales, researchers may uncover novel cancer suppression mechanisms that could be applied to human medicine. The study also highlights the importance of understanding the role of gestation periods, DNA repair mechanisms, and immune function in cancer resistance.

Future research should focus on identifying the specific genetic and molecular mechanisms that enable certain species to resist cancer. This could lead to the development of new cancer treatments and prevention strategies for humans. Additionally, further studies are needed to explore the interplay between immune function, metabolism, and cancer resistance across species.

Conclusion
This 10-year study provides valuable insights into cancer resistance across vertebrate species, challenging Peto’s paradox and revealing the complex relationship between body size, longevity, and cancer risk. By identifying species with low cancer rates and uncovering potential mechanisms of cancer suppression, the research opens new doors for understanding and combating cancer in humans. The findings underscore the importance of studying diverse species to inform cancer prevention and treatment strategies, offering hope for breakthroughs in the fight against this devastating disease.

Reference: “Cancer Prevalence across Vertebrates” by Zachary T. Compton, Walker Mellon, Valerie K. Harris, Shawn Rupp, Diego Mallo, Stefania E. Kapsetaki, Mallory Wilmot, Ryan Kennington, Kathleen Noble, Cristina Baciu, Lucia N. Ramirez, Ashley Peraza, Brian Martins, Sushil Sudhakar, Selin Aksoy, Gabriela Furukawa, Orsolya Vincze, Mathieu Giraudeau, Elizabeth G. Duke, Simon Spiro, Edmund Flach, Hannah Davidson, Christopher I. Li, Ashley Zehnder, Trevor A. Graham, Brigid V. Troan, Tara M. Harrison, Marc Tollis, Joshua D. Schiffman, C. Athena Aktipis, Lisa M. Abegglen, Carlo C. Maley and Amy M. Boddy, 13 January 2025, Cancer Discovery.
DOI: 10.1158/2159-8290.CD-24-0573