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

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:How are these Cancer Cells?

[ComaVN]

Regular pathogens did not originate as animal cells

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 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.

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.