Contagious Cancer Found in Dogs

Dan East writes "Scientists in England have gathered definitive evidence that a kind of cancer in dogs, known as Sticker's sarcoma, is contagious. It is spread by tumor cells getting passed from dog to dog through sex or from animals biting or licking each other. Robin Weiss and his colleagues did genetic studies on the tumor cells from 40 dogs with Sticker's sarcoma, collected from five continents, which showed that all the tumor cells are clones of each other. The parent cell probably arose in a domesticated dog of Asian origin — perhaps a husky — hundreds of years ago, and perhaps more than 1,000 years ago. A similarly transmissible cancer has recently been discovered spreading through populations of Tasmanian devils."

Comments

tasmanian devil & spreading cancer

[fredouil]

unfortunately this kind of cancer is not new, here in Australia, the Tasmanian devil are diying and will soon disapear. http://news.nationalgeographic.com/news/2006/02/02 27_060227_tasmanian.html

How are these Cancer Cells?

[mochan_s]

It is spread by tumor cells getting passed from dog to dog through sex or from animals biting or licking each other. Robin Weiss and his colleagues did genetic studies on the tumor cells from 40 dogs with Sticker's sarcoma, collected from five continents, which showed that all the tumor cells are clones of each other.

So, all tumor cells are clones of each other and not related to the dog. How is this cancer? Isn't it just a regular pathogen then?

Damn...I just lost my dog to cancer.

[ip_freely_2000]

A 9 year old Border Collie with an aggressive tumor in her front leg. This happened two weeks ago. She spent a lot of time playing with other dogs in the park. I'd hate to think that me wanting my dog to have some fun is what killed her. I'd hate to have to wonder and worry about this with my next dog.

How does it evade the immune system?

[neatfoote]

My understanding was that normal cancers survive in the body because they're part of its own tissue, and are recognized by the immune system as normal body cells. If, as the article says, this sarcoma really is transmitted via the cancer cells themselves (as opposed to an infectious cancer-causing agent like a virus), then shouldn't the infected dog's immune system recognize the cells as coming from another dog and attack them?

Tasmanian Devils have it worse...

[aapold]

Tasmanian Devils are being wiped out by a transmissable cancer called Devil Facial Tumor Disease, its a pretty hideous disease that eventually causes the animals to starve to death as they are unable to eat. It is transmitted when Tasmanian Devils fight each other. It is estimated 100% fatal within 12-18 months, it is estimated that over half of all remaining Tasmanian Devils in the wild have it, and it has decimated their population.

confusing

[i_should_be_working]

FTA:
A cancer cell is usually an animal's or person's own cell..

..the cells are not genetically related to the dogs they are in -- proof that they did not arise from the dogs' own cells.

..all the tumor cells, no matter where they were collected, are clones of each other.

If every cell of this cancer is a clone, and not the dog's own cells screwing up, then I'd say this is more like an infection. An alien organism has invaded the dog's body and then replicates. What's the difference (in terms of the vector) between this and a bacterial infection (also single-celled)?

Re:Which is why...

[RsG]

Finally, for the cancer to spread in the way described, we must be talking about cells with a high degree of mobility. This can't be something attached to something, like a tumour, or it couldn't spread identically from organism to organism.

I could be way out of line here, but I'm pretty sure that metasticized cancer cells have a high degree of mobility in normal, non-contagious cancers. The ability to jump from one organ to another via bodily fluids doesn't seem that far removed from the ability to jump from one organism to another via those same fluids. So I don't think the distinction here is mobility.

Part of what's unusual about this strain of cancer is mentioned in TFA:

Studies suggest that, unlike most tumor cells, which contribute to their own demise by becoming increasingly genetically fragile, Sticker's tumor cells are remarkably genetically stable, perhaps explaining in part their evolutionary success.

So the cells are unusual, at least when compared to other forms of cancer.

Another thing I find odd is that the dog's immune system doesn't recognize these cells as foreign and attack them; one of the reasons that your own immune system has trouble attacking your own cancer cells is because they're identical to the host's. OTOH, they say the cancer isn't fatal in dogs, so it's quite possible that the immune system does limit it's development.

Re:Which is why...

[Reziac]

[Hat: I am a professional dog trainer and breeder with 37 years experience.]

I first noticed an apparently-contagious tumour in dogs about 15 years ago. Transmission seems to require direct contact (not necessarily venereal), and the growth is always located in or just under the skin. Superficially, it resembles an ordinary fatty tumour. Under the microscope it looks like it's not exactly benign, but not like a "hot" cancer either. I've never seen one develop into anything serious.