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."

Re:It happens in humans, too.

[thebdj]

There is a big difference. In the HPV case, there is a viral infection THAT MAY cause cancer in people with the virus. This is talking about the tumor cells actually transferring from one animal to another to cause infection. So to recap, HPV is a virus that may cause cancer in women with it and should not be confused with communicable cancer. A communicable cancer would be transferred from person one to person two and cause a cancer infection. (You know, how the flu, common cold, and a host of other diseases work.)

Re:It happens in humans, too.

[Anonymous Coward]

If you had RTFA :

Cancer-causing viruses may spread from person to person, but the cancer does not. But the dog cancer, known as Sticker's sarcoma, is spread by tumor cells getting passed from dog to dog through sex or from animals biting or licking each other.

Re:How are these Cancer Cells?

[ComaVN]

Regular pathogens did not originate as animal cells

Re:It happens in humans, too.

[Burlap]

close, but not quite.

Human Papolova Virus (HPV) can be transmitted from person to person, however the cancer cells it creates are from the host. The article states that in this case the very cancer cells themselves are being transmitted and growing in a new host. These tumors have no genitic relation to host, whereas HPV induced cancers do.

It's not even really LIKE a normal cancer...

[ScentCone]

... in the sense that these are not the dogs' own cells. This is much more like the dog being a petri dish for a parasitic cell that's being physically passed along, almost like bacteria. The cells just set up shop in the new dog's tissues.

Slightly annoying, in TFA, is the notion that "DNA will try anything to reproduce itself." That might want to read more like "just about everything happens to DNA as it's cloned, and sometimes the mutations work better, and sometimes they fail." There's nothing worse than anthropomorphizing your description of cellular mechanics.

Re:It happens in humans, too.

[eli pabst]

I haven't read the journal article in Cell yet, but from my understanding this isn't interesting from the standpoint of a virus being able to transform normal cells into a tumor. There are a large number of examples of that (EBV, KSHV, hepatitis B virus). This is interesting because it's the actual tumor cells themselves that are being transmitted from one host to another. You can do that in the lab by injecting tumor cells from one mouse into another and letting a new tumor form, however I haven't seen examples of this occuring naturally and in those experiments the mice need to either be from the same genetic background or immunosuppressed SCID mice.

Original peer-reviewed Cell link

[mapkinase]

In this table of contents [cell.com] go to "Clonal Origin and Evolution of a Transmissible Cancer". Summary:

The transmissible agent causing canine transmissible venereal tumor (CTVT) is thought to be the tumor cell itself. To test this hypothesis, we analyzed genetic markers including major histocompatibility (MHC) genes, microsatellites, and mitochondrial DNA (mtDNA) in naturally occurring tumors and matched blood samples. In each case, the tumor is genetically distinct from its host. Moreover, tumors collected from 40 dogs in 5 continents are derived from a single neoplastic clone that has diverged into two subclades. Phylogenetic analyses indicate that CTVT most likely originated from a wolf or an East Asian breed of dog between 200 and 2500 years ago. Although CTVT is highly aneuploid, it has a remarkably stable genotype. During progressive growth, CTVT downmodulates MHC antigen expression. Our findings have implications for understanding genome instability in cancer, natural transplantation of allografts, and the capacity of a somatic cell to evolve into a transmissible parasite.

This is just great. This is worse that prions.

Re:For that matter...

[Ford Prefect]

From the article linked from elsewhere in the comments [scienceblogs.com]:

The scientists found that the Sticker sarcoma cells make very few of the surface proteins that vertebrates use to distinguish self from non-self. It appears that the tumor cells can avoid an all-out attack from the immune system. Instead, the immune system reins in the cancer cells, which can survive in the dogs even after their tumor disappears.

It's ... evolved.

Re:How are these Cancer Cells?

[rabbitfood]

They are related to the dog simply because they are dog cells (and most dogs are genetically very similar), they just happen to be cancerous, transmissible and genetically identical dog cells. Tumour cells are usually aberrant (mutant) cells from the host animal that don't differentiate (i.e. turn into the right sort of cells for the tissue they are in) and don't regulate their division (i.e. they multiply without restraint). That's what makes them cancerous. And because most of them don't look anything special to the immune system, they don't get rejected.

Contagious cancers aren't a new idea, but the transmission methods aren't very clear. This research clarifies an important element of the process that will be useful in defining healthcare strategies for both animals and humans. Happily, health organizations are well used to managing such threats, and once sex has joined smoking as an unacceptable activity, we'll wonder what all the fuss was about.

Some Informative Links

[JoshDM]

A Readable Technical Discussion of Stickers Sarcoma [scienceblogs.com] and Canine TVT - 2004 to Congress [vin.com].

Excerpt on Geographical Distribution from the latter: TVT is seldom or no more detected in North and Central Europe and in North America, mainly due to the population control of stray animals, the preventive pre-breeding examination and the effective treatment of clinical cases. With a few exceptions, TVT remains endemic in the rest of the world, obviously because of the uncontrolled population of stray dogs and the inadequacies of exerting effective treatments.

Re:Your dog wants a condom

[JoshDM]

How common is Sticker's sarcoma, though? We have a dog, and although she's not getting to fuck like a rabbit, dogs often lick each other and sometimes bite..

See this post [slashdot.org].

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

[Anonymous Coward]

Probably not the cause. From the article: "Sticker's sarcoma is usually not fatal . . .".

Re:It's not even really LIKE a normal cancer...

[axolotl_farmer]

The cancer cells are mutated dog cells, only that they originated in another dog maybe 1000 years ago. The new discovery is that the cancer cells can infect other dogs. Usually, cells from another individual (even cancerous cells), are recognized as foreign and destroyed by the immune system.

Re:How does it evade the immune system?

[lockefire]

From the original article in Cell:

A recent study (Hsiao et al., 2004) shows that, during progressive growth, secretion of TGF-b1 by CTVT acts as a potent local inhibitor of host immune responses, as does the downmodulation of DLA class I and II expression observed by us and others (Cohen et al., 1984).

DLA is basically the dog immune system method of identifying 'self'. These tumor cells are hiding the fact that they are not-'self' well enough that they easily overwhelm any immune response.

Re:How are these Cancer Cells?

[Graff]

The strange thing is their claim that after dog bites these "cancer cells clog up the jaw, and the poor animals die of starvation".

That's the cancer that affects tasmanian devils, not not the cancer that is affecting dogs. The dog version apparently is very rarely fatal to the dogs that contract it.

Which is why...

[jd]

...the cancer cells are identical. Not merely "similar", in that they're cells of cancer type X, but a direct copy of the original cancer. (The genes that are present are from a husky, if I understand the story correctly, and the markers are clear enough to be able to estimate a timeframe. This is how they know the origin, as opposed to finding said husky in a glacier somewhere.)

This story has a lot of implications that aren't necessarily obvious. First, if both dogs and marsupials can have a contageous, directly-transmissable cancer, then so can any species, through ANY mechanism that involves a transfer of cells. I wonder if blood banks are being screened for such cancers. Given the total lack of speed they showed over AIDS or vCJD, I seriously doubt they've got any serious monitoring in place for such pathogens. (Sure, it's a theoretical, but it would seem better to KEEP it a theoretical, rather than wait until it's a major problem.)

Since this was presumably two different spontaneous mutations, transmissable cancer must be capable of arising in almost any organism at almost any time. I doubt there would be many carcinogens in common between Alaska and Australia, despite them having the same first and last letters. Understanding that mechanism would seem very important, as it would seem reasonable to assume that anything that easy to start would be equally easy to stop.

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. It must also be fragile enough that an airborne version has not yet evolved. However, that may be merely a matter of time. I think medical labs should be putting the effort into understanding the mechanisms and the limitations of transmissable cancers, as we really don't want to be in the usual mess of playing catch-up afterwards, but don't need to do more than necessary if research shows that the limitations are barrier enough.

Re:confusing

[ajs]

The OP was right. It all looks the same to the immune system.

Good gods no! To the immune system, this would look very different from an infection. For starters, it's going to appear to be "mostly dog", that is, many of the markers that prevent the immue system from attacking will be expressed. Bacteria don't do that, at least not on this scale (though they might mimic the host's markers enough to bypass some of the more common defenses).

No, this is going to look more like a parasite or perhaps some sort of contamination (e.g. blood or other fluids that were exchanged during sex/combat/etc.) from another dog.

The curious part is how this cell defends itself against the immune system. That's a pretty impressive trick, and one that humans haven't been able to match.