About 200 years ago, a single cancer cell detached from a dog’s or wolf’s tumor and began to travel as a dog’s sexually transmitted disease or a disease of intimacy. It can be transmitted by licking, biting, and sniffing of tumours. The resulting disease, CTVT for canine transmissible venereal tumor, is found on dogs all around the world. Scientists noticed that the tumors were similar. They found that the tumors were related to each other rather than to the dogs they were infecting.
Now the cancer has been shown to be a clone of a single cell–the oldest known living cancer. It’s a cancer cell that has become a parasite. It has split into two related strains that each have a broad geographical distribution. The tumor seems most closely related to grey wolves.
The tumour is foreign tissue that “ought not” to grow. In most dogs, there’s a fast, aggressive growth stage, but after several months, the tumor shrinks and disappears. It seems that the dog’s immune system wins after all.
The research was described in the August, 2006 issue of the journal Cell.
P.S. This was covered much more thoroughly by Ed Yong at Not Exactly Rocket Science, “Of dogs and devils – the rise of contagious cancer” and by Azra Reza at Three Quarks Daily, “Long-lived Cancer Goes to the Dogs”.
