As dogs became domestic animals, they walked the path of coexisting with humans and advanced to all over the planet with humans. These dogs have cancer cells that have been metastasized between dogs over 8,500 years.
CTVT (canine transmissible venereal tumor) is an infectious cancer that occurs in canines. It is mainly transmitted by mating and forms external tumors. An example of cancer that is a major cause of infection is cervical cancer. Cervical cancer is caused by a virus called HPV (Human papillomavirus). On the other hand, CTVT is infected by directly transferring cancer cells from dogs to dogs by contact with the genital organs of dog mating. It is quite rare that cancer is transmitted in this way. In addition to CTVT, only 8 species, including the Tasmanian Devil, are confirmed.
To find the origin of CTVT, Cambridge University researchers collected 546 CTVT samples from dogs around the world and analyzed their genes. As a result, it was found that all CTVTs originated from just one CTVT cell that lived in Central Asia 4,000 to 5,000 years ago. The research team also succeeded in finding the footsteps of CTVT’s spread around the world in the traces of genome mutations.
CTVTs that originated in Central Asia have existed only in Central Asia for thousands of years. It is presumed that the origin of CTVT lived in an isolated environment in another group of dogs. Later, from 1,900 years ago, it slowly began to advance toward Europe, but it exploded 500 years ago, spreading even among American dogs, and eventually spread all over the world. Currently, most CTVTs around the world are directly ancestors of American CTVTs.
The strange nature of CTVT isn’t just that it is infected. The general cancer genome remains that cancer cells in unstable tumors are genetically completely different cells. It is said that genome instability is the property of increasing malignancy as it evolves by repeating mutations in turn. It is also the biggest factor that makes cancer a difficult disease to eradicate.
On the other hand, as can be seen from the fact that the origin of the CTVT gene can be traced back thousands of years, CTVT has a stable genome and a gentle mutation rate. It is known that if a dog is healthy, the progression is slow and it is rare that it can cause direct death. In addition, it is relatively easy to treat because it cannot obtain resistance to the drug, in fact, almost all of the 546 animals that provided CTVT samples were also cured.
The research team says that CTVT coexists with dogs. The cells themselves behave like cancer cells, but the overall condition is like a parasite. It is the view that CTVT chose not to kill the infected, but to live with the infected.
He also points out that the possibility of being tamed by mutating tumors through CTVT research is suggested. Already, among cancer researchers, a treatment called adaptive therapy to replace chemotherapy has begun to be considered. Unlike active treatment aimed at eradicating cancer, adaptive therapy is an attempt to tame and control cancer. Some places like the Mayo Clinic are planning clinical trials that apply the treatment to metastatic breast cancer.
Experts say that it is surprising that most cancer cells continue to evolve for decades until the patient dies, while CTVT has not made any new adaptations over thousands of years. Expected. Related information can be found here .