Our fur-babies share a deep connection with us; not just in their love but in their genes. Cancer researchers at the University of Minnesota and North Carolina State University have found that they also share the same genetic basis for certain types of cancer.
Quick Background
Genomes are divided into chromosomes, which act like the folders on your computer with genes located in specific places (e.g. My Documents, My Music, etc.).
"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." (ScienceDaily)
In other words, researchers found that the genetic changes that occur 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 virtually identical to genetic abnormalities in humans diagnosed with the same cancers. But this is just one research study.
A similar study, conducted at Purdue University, found that pre-melignant mammary lesions in dogs and humans display many of the same characteristics; discovery that could lead to a better understanding of breast cancer, the second leading cause of deaths in women. (Elisabetta Antuofermo)
These two images are examples of a mammary lesion in tissue surrounding a tumor from a dog (left) and one in human mammary tissue (right). Purdue research shows that the similarity between canine and human lesions associated with breast cancer makes dogs an ideal model to study progression of the disease while it is still treatable. (Graphic of slides provided by Sulma Mohammed, Purdue University School of Veterinary Medicine) (Elisabetta Antuofermo)
The similarities don’t end there. The most frequently diagnosed form of lymphoma affecting dogs mimics the medium to high-grade B cell non-Hodgkin’s lymphoma in people; this is the type of cancer that Angel had. Osteosarcoma, the most common bone cancer of large and giant breed dogs, closely resembles the osteosarcoma in teenagers in its skeletal location and aggressiveness. Female dogs spayed before puberty are less prone to breast cancer than are their non-spayed counterparts, much as women who have their ovaries removed, who begin to menstruate late or who go into menopause early have a reduced risk for breast cancer. (Wildasin)
Why Are Dogs So Similar and Why Do They Make Good Research Subjects?
According to leading cancer researchers, dogs are good research subjects because they develop the disease spontaneously, and many of the modern breeds have developed over the past few hundred years using restricted gene pools. This selective breeding has preserved the genetics of a breed. It has also made some breeds more susceptible to certain cancers. These factors, coupled with the high degree of similarity between the genomes of dogs and humans, provided the researchers with an opportunity to compare the genomes and study the evolutionary genetic changes associated with cancer. (ScienceDaily)
Another reason has to do with how human drug trials are conducted. Comparative oncologists can test new treatment ideas against early-stage cancers; delivering the drugs just as they would ultimately be in people. This means more effective treatments can be developed more quickly, with less adverse health risks, for human trials and ultimately viable human treatments. They also have shorter life spans than humans (most unfortunate), meaning scientists can more quickly determine whether a prevention strategy or therapy has a good chance of improving human survival rates. (Wildasin)
In Closing
We can’t think of a better way end this entry then with this quote from Matthew Breen, Ph.D., North Carolina State University's Center for Comparative Medicine and Translational Research.
"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." (ScienceDaily)
Sources
Elisabetta Antuofermo, Margaret Miller, Salvatore Pirino, Jun Xie,. "Spontaneous Mammary Intraepithelial Lesions in Dogs: A Model of Breast Cancer." Purdue University News (2007).
ScienceDaily. "Genetic Cancer Link Between Humans And Dogs Discovered." ScienceDaily (2008).
Wildasin, Dr. David J. Waters and Kathleen. "The Vital Importance of Comparative Oncology: Cancer Clues from Dogs." Scientific American (2006).