An American study shows that a dog’s size influences the risk of cancer. Small breeds such as Chihuahuas and Pomeranians are less likely to develop cancer than larger breeds. But size does not appear to be everything.
Just like humans, dogs can suffer from various diseases including cancer. But some dog species are more sensitive to this than others. To find out why, researchers from the… University of California the data of more than 70,000 dogs of 82 different breeds, registered with the Veterinary Medical Database. In this dataset they looked at cancer mortality, body size and the amount of inbreeding. From this they drew the conclusion: the larger the dog, the greater the risk of cancer – except for the largest dogs.
Cell divisions
The researchers think why large dogs are more likely to develop cancer has to do with the number of cell divisions. Cancer can be caused by an accumulation of mutations in the DNA of cells. The more cell divisions take place, the greater the chance that errors will arise in the DNA. Larger dogs have more cells and therefore a greater chance of mutations. In addition, larger dogs grow faster and have a higher metabolism, which can also lead to more DNA damage.
Exceptions
However, this cannot explain all differences in cancer risks in dogs. The study found that some breeds, such as the Flat-Coated Retriever, Scottish Terrier, Bernese Mountain Dog and Bullmastiff, had a higher cancer risk than you would expect based on their size. This may be due to genetic factors specific to these breeds.
Other exceptions to the ‘rule’: the larger the dog, the greater the risk of cancer, are the largest breeds. This is because a dog’s size also affects its lifespan. Because larger dogs generally live less long than smaller dogs, the largest dogs also have less time to develop cancer, because the disease often only develops at a later age. Inbreeding, in which animals that are closely related to each other produce offspring, does not appear to be related to the risk of cancer. “It does, however, generally shorten the dog’s lifespan,” the study states.
The researchers hope that their research will contribute to greater insight into the causes and prevention of cancer in dogs, but also in humans. The variation in body size and inbreeding in dogs offers a unique opportunity to investigate the influence of these factors on cancer. Furthermore, the researchers estimate that each dog acquires approximately 1.4 mutations per cell per generation, which is also comparable to humans.
The golden retriever has a 65 percent chance of dying from cancer. At the same time, however, there are also golden retrievers that manage to escape this dance and live to be 16 years old, or very old. Researchers from the University of California examined the genetic material of more than 300 golden retrievers. They soon discovered that dogs with certain variants of the HER4 gene tended to live longer. “The hope is that we can eventually select for dogs with a longer lifespan,” a researcher previously told Scientias.nl. It is important to keep in mind that lifespan and cancer risk cannot be traced back to one gene. “There are a lot of genes involved,” added a colleague. “But the fact that the gene that can be associated with longevity is also a gene that plays a role in cancer is very interesting.”
