Can Capybaras Help Fight Cancer?

Last summer, I vacationed in the amazing city of San Diego. Along with reveling in the beautiful beaches and historical parks, my family made a point to visit the most famous zoo in the US - the San Diego Zoo. With 100 acres of land and hundreds of different species, the San Diego Zoo was certainly an exhilarating place. While most people likely look forward to seeing the majestic lions or cuddly koalas, I was most excited to see the capybaras. 

A capybara with its two capybara pups - how cute!!

I'm sure you've seen capybaras on TikTok, Instagram Reels, or anywhere else you get your fill of social media. From the viral capybara song to videos that make you go "aww" - capybaras are everywhere now - and rightfully so! Capybaras are undeniably adorable animals. Just look at their tiny legs and shaggy fur! As the biggest living rodents on Earth, capybaras can grow to be over 4 ft in length and weigh over 150 pounds, a far cry from other rodents (guinea pigs, mice, hamsters, etc.). Yet despite their size, they truly are gentle giants. They can be found to have birds, monkeys, or their own pups riding on their backs as they walk around or wade through water, as capybaras are excellent swimmers. In Japan, zoos often let them enjoy relaxing in hot springs - tell me that's not absolutely precious. 

Capybaras enjoying a hot spring bath 

In addition to being endearing, capybaras are truly fascinating creatures from a biological standpoint. With capybaras being so drastically different in size compared to their rodent relatives, the question to ask is - how did they evolve? Small size has proved to be an advantage for most rodents as it protects them from predators - especially since most rodents (including capybaras) are herbivores, and carnivorous rodents are equally as unthreatening, sticking to insects and other small organisms. Scientists have hypothesized that capybaras were able to grow in size due to the lack of predators in their habitat when they first developed. The large size of capybaras calls another aspect of their evolution into question - one that might provide insight into treating cancer. 

Cancer is the uncontrolled dividing of cells due to mutations in a cell's DNA, mutations that may develop randomly during DNA replication and cell division. The more cells an animal has, the more DNA replication and cell division occurs, increasing the likelihood of replication errors and mutations. The large size of capybaras mean they have more cells and therefore should indicate an increased risk of cancer, however this is not the case. In fact, there have only been 3 known cases of cancer in capybaras, whilst mice are even more susceptible to cancer than humans are. This absence of a correlation between animal size and cancer risk has confused scientists for years, and is known as Peto's Paradox. A full explanation for this paradox is yet to be found, however, scientists have found that various large animals have developed their own mechanisms for fighting cancer. For example, elephants have twenty copies of the p53 gene, as opposed to most animals having only one. The p53 gene codes for proteins that repair damaged DNA before division or induce apoptosis to prevent cancer development, decreasing the frequency of cancer in elephants. Similarly, bowhead whales are quicker at repairing damage to their DNA than other animals, and are less likely to have errors as well. 

Peto's Paradox demonstrated by comparing the expected vs observed cancer rate

In 2018, scientists found that capybaras had their own cancer-fighting mechanism. The capybara genome was found to have 3 gene families that were larger compared to other rodent genomes. This expansion contributes to the size difference, as well as to a signaling pathway that suppresses cancer cells and is regulated by T-cells. T-cells are a type of white blood cell and an important part of the immune system. T-cells help destroy infected or cancerous cells, and signal for other cells to fight harmful pathogens. This means that capybaras have an immune system that is much better at identifying and terminating cells that divide too fast and have the potential to become cancer. Their innate mechanism is similar to a treatment provided to cancer patients called immunotherapy, in which a patient's immune response is amplified to destroy more cancer cells. Just a few years ago, a groundbreaking form of immunotherapy called CAR T-cell therapy was developed to treat lymphoma and leukemia. This treatment genetically modifies T-cells to synthesize chimeric antigen receptors, allowing the T-cells to find and destroy cancer cells that contain a specific protein. CAR T-cell therapy has proven to be very successful, with 83% of leukemia patients showing complete remission after 3 months, and 50% of lymphoma patients showing signs of remission after 15 to 24 months. With immunotherapy proving to be revolutionary and worthy of further research, capybaras could be a useful thing to study. 

It is with great sorrow and shame that I admit I was unsuccessful in my very important pursuit to see a capybara - though in my defense, the map was very confusing and the zoo is enormous...and I am not big on walking. I was even more disheartened when I visited Turtle Back Zoo the following Fall and found that we do not have capybaras here in Essex County - what a travesty. I have not lost faith, though, and I am even more determined to see one, especially now that I know capybaras are more than just a pretty face. I didn't know it before, and I doubt they know it themselves, but the mere existence of capybaras brings up a whole host of questions as part of the continuously intriguing world of biology.