Cancer drugs are tested on pets

Last December, Luisa Bozana's dog Einstein was diagnosed with brain cancer. The large tumor took up most of the 8-year-old dog's left lobe. With few options, the owner decided to perform surgery to remove the tumor, along with half of Einstein's skull. The skull is replaced with a polymer-based binder.

Everything went well until the middle of the year when the tumor returned.

Now, it has more tassels, like an octopus that puts its arms crept through the nerve cells of important organs. The only option left to prevent the growth of the mass is an experimental treatment, which involves inserting a virus into the animal's brain. In theory, the virus will only infect cells that are rapidly dividing, and then an antiviral method will be applied to kill the virus along with the infected tumor cells.

Scientists plan to one day use this therapy in humans. However Einstein will become the first animal to experiment with this new method.

Bozano said: 'It is in very bad condition, and this is the only chance.'

Einstein is one of 6 million dogs diagnosed with cancer in the United States each year. From this group, a new field of research is developed, called comparative oncology, in which the companion animal (mostly dogs) is used as a model for human cancer. Cases like Einstein provide a unique opportunity for scientists to experiment with new cancer treatments on naturally growing tumors, instead of artificial tumors formed in animals. experiment.

Researchers hope knowledge from these therapies can help many people and their close pets.

Recent steps

This is not the first time dogs have been used as cancer research models. Guinea pig has been used for bone marrow transplantation in the 1960s and 1970s, and surgery to preserve limbs for bone cancer in the 1980s and 1990s.

But in recent years, scientists have found great potential for livestock to help us fight cancer, and in 2003, the National Cancer Institute (NCI) established the Cancer Program. Comparative library. This program aims to use pets to learn more about the biology of cancer and to help experiment and improve new therapies to be applicable in humans.

Dr. Melissa Paoloni, a veterinary oncologist and researcher at NCI, said: 'In 20 or 30 years, we can confirm that the comparative method has made valuable contributions in the field. science, and special areas, the field of cancer research and treatment '.

The complete dog genome sequencing in 2005 promoted research in this area, because scientists can study the genetics of cancer in dogs and apply that knowledge to humans. .

Why choose pets?

Why use pets? The first reason is that cancers in animals form naturally, like cancer in humans.

Paoloni said: 'Cancer in pets is much more complicated than what we can simulate in the laboratory. All problems with cancer that patients encounter also appear in pets'.

Like cancer in humans, cancers in pets can resist chemotherapy, can recur after treatment and can spread to other parts of the body.

Another great advantage is that scientists can evaluate new treatments on livestock early in the disease process, while for humans, they may have to use new methods as the last option. when cancer has grown.

Dr. Barbara Kitchell, director of the Center for Comparative Oncology at Michigan State University Veterinary College, said: ' We can lose the advantage of therapeutic strategies that can be effective at the stage. head of the disease, through the selection of patient components not suitable for testing '.

Einstein is one of 6 million dogs diagnosed with cancer in the United States each year. From this group, a new field of research is developed, called comparative oncology, in which the companion animal (mostly dogs) is used as a model for human cancer. (Photo: stock.xchng)

People and pets often share similar environments. That means dogs can be exposed to some of the same cancer-causing agents as their owners, and may develop similar forms of cancer. '

Because dogs often have a shorter life cycle than humans, cancer in this animal grows faster than cancer in humans, allowing scientists to monitor the effects of the disease in a shorter period of time . Kitchell said: ' If you have a cure and it takes 5 to 10 years to clearly see results in people, then that time period is actually shorter in dogs.'

The scope of the cancer varies

When dogs and people have the same type of cancer, the biology of cancer can be quite similar. However, the frequency of different types of cancer depends on the species. Kitchell said: ' Dogs have' different 'diseases than humans'. Some types of cancers are common in people, such as breast cancer and prostate cancer, which is very rare in dogs because they are often castrated or sadly cut. Lung cancer is also not frequent in dogs, because they do not smoke; and high-fiber diets protect them from colon cancer.

However, studying cancer in dogs is still important for cancer research in humans, even if the cancer is not the same. Because two different types of cancer can be similar at the molecular level - for example, the cell process leading to skin cancer in dogs can be similar to the process that leads to breast cancer in women. Scientists can take advantage of this same feature to use models in dogs to develop a treatment for humans.

In addition, rare cancers in humans often occur in dogs. For example, dogs have a higher incidence of bone cancer than people.

Scientists can take advantage of this fact and use dogs to study rare cancers on a larger scale. Kitchell said: 'It is difficult to gather enough patients together to model a rare cancer, but we can do this easily in dogs.'

Drug development

Researchers and pharmaceutical companies have used dog models to help them design medical experiments in humans and develop new anti-cancer drugs. For example, from 2003 to 2006, Dr. Phil Bergman of Memorial Sloan-Kettering Cancer Center in New York used dogs to develop a vaccine for melanoma, or skin cancer. The vaccine was approved for use in dogs in 2007, but the results of the study helped scientists develop similar vaccines in humans.

Paoloni said: 'Data from experiments for pet dogs can be used to help design human health experiments'. These experiments can help scientists learn how to use the most appropriate and time-consuming new drugs, understand the amount of medication to use, and evaluate possible side effects or toxicity. Comes with treatments'.

Experiments on new methods in dogs and other pets also have a drawback. These treatments are tailored to fit an animal and cannot be used in other species. At the same time, pharmaceutical companies worry that drugs that can be completely safe to use in people may have adverse effects on dogs.

Kitchell explains: 'What if they found a side effect in the experiment for dogs that collapsed FDA approval plans for a lead compound, and they had to explain why dogs have This side effect, while humans will never encounter '.

However, pharmaceutical companies still welcome the opportunity to have new models that can help them in the expensive and often less successful drug development process. A new cancer drug costs $ 1 billion to develop, and only about 5% of all cancer drugs reach the market.

Paoloni said: 'The enthusiasm and money spent in drug development make the scientific community and pharmaceutical companies even more interested in finding new models.'

Personalize the treatment

In the future, doctors hope to be able to transform cancer treatments to fit each person's tumor. Called 'personalized medicine', such treatments include tumor sampling, genetic analysis, and appropriate application to treat each patient.

However, before the period of personalized medicine began, Paolini said comparative oncology was the best model for scientists.

She said: 'I think the development of personal medicine strategy is one of the special and important contributions of the comparative method that we will see in the next few years.'

For dog owners like Bozano, participating in a medical experiment for a new treatment is the last chance to save your pet. She said: 'This is our last hope, the last thing we can try.'

According to Paoloni's experience, pet owners sign up for their pets to participate in experiments like this, not only to help their animals but also help others.'Realizing that studies using comparative methods can be used to help other patients, I think that is a great motivation for the pet owner community'.