A groundbreaking study from Arizona State University (ASU) has examined cancer prevalence among various vertebrate species, revealing significant patterns that challenge existing theories in evolutionary biology. Researchers analyzed over 16,000 necropsy records from 292 species, providing fresh perspectives on how cancer evolves in multicellular organisms.
The research contests Peto’s paradox, which posits that larger animals, with their greater cell numbers and longer lifespans, should experience higher cancer rates. The study found that while cancer rates do increase with body size, the increase is minimal. This suggests that larger animals have developed effective mechanisms to suppress cancer, complicating our understanding of cancer risks across different species.
The study indicates that cancer rates rise with body size and mutation rates but decrease with longer gestation periods. This complexity reveals that the relationship between size, longevity, and cancer resistance is more nuanced than previously thought. The findings could offer insights for developing better cancer treatments.
Lead author Carlo Maley, a researcher at the Biodesign Center for Biocomputing, Security, and Society, expressed the importance of this research. “Until now, we knew little about cancer rates in species other than humans, dogs, and naked mole rats,” he said. The study features contributions from an interdisciplinary team across various U.S. and international research institutions and is published in the journal Cancer Discovery.
Data Collection and Findings
The study’s data were gathered from 99 zoological facilities, including aquariums, where veterinary pathologists performed necropsies to identify tumors. The results showed striking disparities in cancer prevalence. For example, up to 63% of ferrets developed tumors, while species like the common porpoise and black-footed penguin exhibited cancer rates below 2%. These trends suggest that species with shorter lifespans may lack sufficient evolutionary pressure to develop strong cancer defenses.
Mammals generally displayed the highest rates of tumors, followed by reptiles, birds, and amphibians. Notably, elephants and whales, despite their large sizes, showed low cancer rates. This is likely due to multiple copies of cancer-suppressing genes, such as TP53, and other protective mechanisms that researchers are still exploring.
Additional Cancer Defense Mechanisms
Beyond TP53, the study uncovered other cancer defense strategies. Species with fewer random mutations in their cells tended to have lower cancer rates, indicating that effective DNA protection and repair could shield them from cancer. The research also found that species with longer gestation periods had reduced cancer rates, possibly allowing cells more time to regulate themselves and minimize harmful mutations.
Researchers examined how different species responded to DNA damage from radiation and chemotherapy. Their findings suggest that factors like immune system function and metabolic processes may play a significant role in cancer resistance, beyond the direct responses to DNA damage.
Co-author Zach Compton noted the potential benefits of these findings for human cancer prevention. “We are excited to harness nature’s strategies for combating cancer,” he said.
Future Research Directions
The study highlights the discovery of species with remarkable cancer prevention abilities. Researchers aim to understand the mechanisms behind these defenses, exploring various strategies such as robust DNA repair and lower mutation rates. Insights gained from these species could lead to new cancer treatments and preventive measures for humans.
The team emphasizes the need for further research to expand knowledge on cancer across species. By collecting more data from wild populations and studying additional species, researchers hope to uncover new patterns of cancer resistance and susceptibility. These efforts could ultimately advance cancer prevention strategies, benefiting both humans and numerous animal species.
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