Washington, Feb 29 : Oncologists at the University of Minnesota and North Carolina State University have found one more association between dogs and humans other than friendship and companionship -the same basis for certain type of cancers.
They said that the similarities and genetic links between canine and human cancers may provide crucial insights to help fight the disease.
The team of researchers, led by Jaime Modiano, V.M.D., Ph.D., University of Minnesota College of Veterinary Medicine and Cancer Center, and Matthew Breen, Ph.D., North Carolina State University's Center for Comparative Medicine and Translational Research, also said that getting cancer may be inevitable for some humans and dogs, because of the way the genomes have evolved.
It is known that genomes have been divided into chromosomes that play the role of nature's biological filing cabinets with genes located in specific places.
"Many forms of human cancer are associated with specific alterations to the number or structure of chromosomes and the genes they contain. We have developed reagents to show that the same applies to dog cancers, and that the specific genome reorganization which occurs in comparable human and canine cancers shares a common basis," said Breen.
The researchers specifically discovered that the genetic changes occurring in dogs diagnosed with certain cancers of the blood and bone marrow, including chronic myelogenous leukemia (CML), Burkitt's lymphoma (BL), and chronic lymphocytic leukemia (CLL), are almost the same as the genetic abnormalities in humans diagnosed with the same cancers.
"We believe the implication of this finding is that cancer may be the consequence of generations of genetic evolution that has occurred similarly in dogs and humans. This means that to some degree, cancer may be inevitable in some humans and dogs just because of the way our genomes have developed since the separation from a common ancestor," said Modiano.
He added: "Since we know now that dogs and humans seem to share a common pathogenetic basis for some cancers, we believe that studying dog cancers may allow us to identify cancer-associated genes more easily in dog populations than in human populations. Once identified, we may be able to translate these findings to human cancers as we seek to provide a greater level of insight into cancer risk, diagnosis, and prognosis."
Researchers believe that the dogs are good research subjects because they develop the disease spontaneously, and a number of the contemporary breeds have developed over the past few hundred years using restricted gene pools. And this selective breeding has conserved the genetics of a breed. It has also resulted in making some breeds more susceptible to certain cancers.
Researchers found an opportunity to compare the genomes and study the evolutionary genetic changes associated with cancer, due to all these factors along with the large number of similarities between the genomes of dogs and humans.
While the human genome has 46 chromosomes, the dog genome contains 78 chromosomes and quiet a few times, chromosomes can become rearranged or relocated in the normal duplication process of cells. This rearrangement or relocation is known as translocation and it can cause a cell to lose its normal function, becoming abnormal, and possibly developing into cancer.
"Interestingly, we found that the same translocation of chromosomes happens in dogs as in humans for the three blood and bone marrow cancers we studied," said Modiano.
Concluding, the researchers said that despite millions of years of divergence, the evolving genomes of dogs and humans seem to have retained the mechanism associated with cancer, and also these retained changes in the genomes have similar effects in both dogs and humans.
"Like ourselves, our pet dogs suffer from a wide range of spontaneous cancers. For thousands of years humans and dogs have shared a unique bond. In the 21st century this relationship is now strengthened to one with a solid biomedical basis; the genome of the dog may hold the keys to unlocking some of nature's most intriguing puzzles about cancer," said Breen.
The findings of this study are published in the current issue of the journal Chromosome Research, a special edition on comparative cytogenetics and genomics research by scientists from around the world.