Alex doesn't know it, but the 12-year-old golden retriever is actually a hero of cancer research.
"When she was about 10, we noticed that she started to limp," said her owner, Kevin Darling, an IT professional living near Columbus, Ohio. "She had the beginning stages of osteosarcoma -- bone cancer."
Because the tumor was confined to Alex's left front leg, veterinarians recommended amputating the limb and then giving the dog chemo. "They said she probably had a 50 percent chance of living one year," said Darling, 45.
He took that chance, and nearly three years later, Alex, minus one front leg, is still "full-tilt running, keeping up with my other dogs," Darling said.
And the bone cancer? A tiny piece of it, along with blood samples from a number of Alex's littermates and other relatives, is slated to become part of the first U.S. canine tumor tissue bank in Frederick, Md. The bank -- formally called a "biospecimen repository" -- began accepting the first of a projected 3,000 canine biopsy samples on May 1.
The new facility lies adjacent to the U.S. National Cancer Institute's own library of human cancer samples. That's no accident -- the canine tissue bank is the dream of a group of researchers who know that malignancies that occur spontaneously in dogs hold vital clues to human cancer.
"The cells of the dog are actually very, very similar to our own cells in terms of their genetic makeup," explained Dr. Matthew Breen, an associate professor of genomics at the college of veterinary medicine at North Carolina State University in Raleigh. Breen is also the treasurer of the nonprofit Canine Comparative Oncology Genomics Consortium (CCOGC), the driving force behind the tissue bank.
The mapping of both the dog and human genomes over the past decade "has shown very clearly that humans and dogs are very closely related," Breen said. "The gene that causes brown eyes in you is probably the gene that causes brown eyes in a dog."
Dogs share something else with humans that makes them ideal models for cancer research, added Dr. Jaime Modiano, an associate professor of immunology at the University of Colorado Health Sciences Center and a CCOGC board member.
"Environmental risk factors for human cancers are virtually duplicated in a dog," he noted. Unlike lab rats or mice, companion dogs "swim in the same water we swim in, they run on the same grass we run on," Modiano said.
And unlike lab animals -- which are usually artificially induced to develop cancers -- the samples collected in the canine cancer tissue bank will come from pet dogs who develop malignancies spontaneously, just as Alex did.
"Mice don't 'get' cancer, they are given cancer," Breen pointed out. "That's why this is so exciting. We, as a community, see the dog as the best biological model for spontaneous cancers, just as they occur in humans."
Americans' four-legged friends -- especially purebreds -- have other tricks of biology that make them invaluable models for cancer research. Humans -- much like "mutt" dogs -- breed willy-nilly, Breen said. But pedigreed dogs are bred so tightly that their DNA remains relatively unchanged.
That genetic purity cuts down on what Breen described as "background noise" within the genome, making cancer-causing mutations easier to identify.
In people, cancer genomics "is like trying to listen to a radio that's out of tune," Breen said. "There's just too much interference. But in some dog populations, all of a sudden a lot of that background interference is removed. So nature's message -- the pinpoint of this or that particular gene -- comes in loud and clear. It's like the radio gets tuned in."
That could mean more and quicker discoveries in cancer genetics, he said.
"I predict that we will find more cancer-associate genes by studying dog cancers over the next 10 years than is likely possible by studying human cancers over the same time," Breen said. And once a particular "oncogene" is spotted somewhere on the dog genome, scientists will simply head for the corresponding locus on the human genome to find it there.
"We can immediately translate that information into human genome information, then go look in human populations with human cancers," Breen said.
Canine cancer research is already saving and improving human lives, Modiano added.
One example: A recent NCI study into an experimental drug aimed at helping children with bone cancer was stopped early after it failed to extend the lives of dogs with the same disease.
"That saved innumerable kids from being treated with something that wasn't going to help them and was going to cause them toxicity," Modiano explained.
Even better, a new vaccine against deadly malignant melanoma has gotten much closer to FDA approval after researchers at New York's Memorial-Sloan Kettering Cancer Center showed it worked wonders in dogs stricken with the skin cancer.
"In fact, it's going to be available as a viable commercial product that vets can get off the shelf" for dogs later this year, Modiano said.
He and Breen are hard at work themselves, developing blood tests that can predict how well dogs with leukemia will respond to particular treatments. "We are also now working with groups of medical oncologists to see about these liquid tumors in people, trying to see how well it carries over for them," Modiano said.
All of this research should gain new momentum with the launch of the new biospecimen repository. According to Breen, the CCOGC, in partnership with the American Kennel Club's Canine Health Foundation, has already raised $1.7 million of the $2.2 million it needs to open the repository.
They also hope to open five dedicated specimen-collection sites nationwide. Three of those sites -- at Colorado State University, Ohio State University and the University of Wisconsin -- have already started collecting biopsy and blood samples as of the beginning of May.
Darling said he's just proud Alex has been able to help.
"Alex may get cancer again and not survive," he said. "But if what I have done has helped somebody in the future -- a person, a dog -- I'd like to know that. To know that I played a part in making that happen."
More information
There's more about the CCOGC and the biospecimen repository at the Canine Health Foundation.
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