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Cancer is a cruel disease that affects large parts of the animal kingdom. Few creatures are spared – not even man’s best friend.
But as it turns out, that deadly bond between dogs and humans could save us too. Researchers recently discovered that certain genes in certain dogs are linked to a rare form of cancer. These results could potentially also help scientists better understand how this cancer manifests itself in humans, argues a study published Thursday in the journal PLOS One.
What’s new? In the study, scientists identify two genetic risk factors that together account for 35 percent of a flat-coated retriever’s risk of developing histiocytic sarcoma – a rare, fatal blood cancer.
Flat-Coated Retrievers are an athletic dog known for their cheerful demeanor, energy, and glossy black coat.
The genetic risk factors are two loci – the specific position of a gene on a chromosome – known as CFA5 and CFA19. According to the researchers, CFA19 was “not previously associated with a cancer risk”.
The researchers also found that CFA5 is associated with two other types of cancer in addition to histiocytic sarcoma: hemangiosarcoma and B-cell lymphoma.
The researchers specifically studied this cancer in flat-coated retrievers, which have a high overall risk factor for the disease. About 20 percent of flat-coated retrievers are ultimately diagnosed with the disease.
It is not entirely clear whether these results apply to other dog breeds as well. However, another study published earlier this year found that Bernese Mountain Dogs, Rottweilers, and retrievers who carry certain genes with certain loci were five times more likely to develop histiocytic sarcoma.
What are the cancers in dogs?
A flat-coated retriever. The researchers looked at the genetic risk of blood cancer in flat-coated retrievers. Getty
Like humans, dogs suffer from a number of cancers that can appear in different parts of the body. According to the National Cancer Institute, about 6 million dogs – or one in four puppies – develop cancer each year.
Histiocytic sarcoma is an aggressive but rare cancer that occurs later in a dog’s life. Dogs with this type of cancer usually don’t live long after being diagnosed.
But there are also more common canine cancers. These include:
- Bone cancer
- Mast cell (skin cancer)
- Breast tumors (breast cancer)
- Hemangiosarcoma (tumors that line blood vessels)
One of the most common of these cancers is lymphoma: approximately 20 percent of canine cancers are associated with lymphoma.
How are canine cancers treated?
A retriever is resting at home. Getty
After a dog is diagnosed with cancer, they will be given many of the same treatment options as humans, including:
As with humans, the treatment plan will depend on the type of cancer and the pet’s current health.
However, the researchers in this study suggest another method of preventing cancer in dogs rather than treating it: selective breeding.
The study’s authors note that selective breeding increased the risk of cancer in flat-coated retrievers. Humans selectively breed retrievers for traits such as the length of the dog’s snout, but this breeding practice inadvertently increases the frequency of cancer genes in the dog’s gene pool.
“In general, breeders choose [to] Pairs of mates who they believe will produce healthy pups with the behavioral and physical traits that characterize the breed, ”lead author Jacquelyn Evans, postdoctoral fellow at the National Human Genome Research Institute, told Inverse.
“However, in late-onset cancer like histiocytic sarcoma, dogs are bred before they show signs of disease on their own, and it can be almost impossible to predict whether a particular group of parents will have offspring who will eventually develop cancer,” says Evans.
Evans and colleagues advocate selective breeding to reduce the risk of these cancer genes appearing in the gene pool over time. Evans explains how her results can help dog breeders:
“Knowing the genetic risk factors associated with histiocytic sarcoma in flat-coated retrievers, a genetic test could be developed to provide more information to breeders, if desired, to carefully reduce the risk of this cancer.”
An ongoing study known as the “Canine Cancer Vaccination” – the largest clinical canine cancer study ever conducted – is also trying to prevent cancer from growing in dogs, albeit through vaccines rather than breeding methods. The scientists behind this study also hope they can apply their findings to help cancer patients in humans.
How Does Canine Research Help Human Cancer Patients?
Scientists hope they can apply their findings to help cancer patients in humans
Scientists have long known that dogs can serve as good models for studying cancer in humans. This is in part because cancer occurs similarly in both dogs and humans, and safe cancer treatments in dogs often work well in humans as well. However, it is also easier to study the progression of genetic diseases in dogs because they have a shorter lifespan and selective breeding reduces the complexity of a breed’s gene pool.
The researchers behind the PLOS One study write that dogs serve as “an excellent model for genetic studies of cancer susceptibility.”
Researchers also note that late onset cancers such as histiocytic sarcoma have traditionally been difficult to study because of the late diagnosis in humans. However, since scientists have succeeded in studying the genetic causes of blood cancer in dogs, there may be hope for research in humans as well.
“As dogs accurately model human disease, we expect an overlap in the genes that are important for histiocytic sarcoma in dogs and humans, and our study identified pathways that are affected in some human tumors,” says Evans.
There is another way our puppies can be helpful: After identifying genetic risk factors for cancer in dogs, we may be able to identify them in humans and develop treatments from them.
“Understanding the genes involved in histiocytic sarcoma can lead to the use of therapies that block the progression of cancer by targeting those genes directly or the ways in which they work,” says Evans.
In return, humans might also be able to help our loyal companions. In recent years, scientists have begun investigating various treatments – previously reserved for humans – in dogs with cancer.