Friday, November 17, 2006

Cancer, the STD?

Most of us know that cancer comes from mutated cells in our body. But scientists have found a cancer in dogs that is derived (or rather transmitted) through sexual contact. The cancer disfigures the face and genitals of the dog but then diminishes. To find the reason, researchers at University College London looked at the DNA of the different species of dogs and the DNA of the cancer to find some answers.

After examining hundreds of dogs of varying breeds around the world, Claudio Murgia was able to tie the cancer to wolves and a breed of dogs in Asia. Genetic differences in the cancer and wolves suggested the cancer has been living continuously for 200 years old from one original source. Analysis of older samples collected years ago also suggests that the cancer was more effective on attacking its host. What actually happens as Murgia found was that the cancer was able to stall the dog’s immune system as it invaded but eventually the immune system was able to identify and neutralize the cancer.

This article brings up a number of key points worthy of further discussion. The article seems to skim over the idea of evolution as a factor in the dog’s ability to rid itself of the cancer. The cancer is genetically more similar to wolves and thousands of years of mutations, genetic drift, lack of gene flow with wolves and artificial selections had set dogs apart from wolves. Therefore, the cancer was not able to blend in with the host’s body. It's DNA was unique enough that after the immune system recovered it was able to spot and target the cancer. Another point that the article skirts over as a possibility was that the dog or even the cancer was able to evolve enough to cope with one another so that the host can live long enough that the cancer can move on.

As to how cancer travels through sexual contact, that’s all relative. Diseased cancer-causing cells can be transmitted in humans through organ transplant or even sexual contact if the immune system is weak enough.


Posted by Tony (11)


At 8:47 PM, Blogger PWH said...

The fact that cancer could possibly be sexually transmitted is scary, yet interesting! What to you mean when you say the cancer 'diminishes'? Does it completely go away, tumors and all, or does it just lessen in severity? Also, did the article say anything about any DNA code in the parts attributed to the susceptibility to this STD-cancer in wolves that was common to humans as well? Humans can get cancer via a virus (females getting cervical cancer because they contract HPV) so I wonder if this possibility extends to other types of cancer.

Posted by LD

At 5:02 PM, Anonymous Anonymous said...

So this cancer that can be transmitted through sexual contact, is this a cause for concern because could it mean something for humans? I wish there were more facts about the genetics of this cancer like the types of organs it affects, how it multiplies, how long it lays dormant before showing and how come we are seeing it just now if it's been around for 200 years.

Posted by Karisma

At 5:11 PM, Anonymous Anonymous said...

does the article say anything in particular about how it multiplies or how it originated in wolves?

how are scientists reacting to this because it could have implications for humans too right?

overall this is a new issue and im glad i know about it

Posted by Karisma

At 5:19 PM, Blogger PWH said...

Interesting article. . . There are a few questions I have though about this article that I am wondering about. I am questioning how many dogs have had cancer via sexual contact in the last few years or so? Can you name some of the types of dogs that had this sexual cancer? How is the immune system able to identify and neutralize the cancer? Nice job though making it easy to read and overall an intriguing subject matter.
CMB (11)

At 5:33 PM, Blogger PWH said...

Very interesting article, a bit odd though. Some of the othre posts touched on a few of the same questions I had reading it, namely the extent of "diminishing" cancer, and as to what breeds were susceptable. Also, how were they able to age the cancer? And if the cancer had survived for such a long time, how was it not selected against? It was a well informed article review, I kept coming back to this one after reading the others.
Posted by BEK (11)

At 11:25 PM, Blogger PWH said...

An important point in the article that this post didn't go over is that this cancer originally developed in one individual, and these same cells are being transmitted to other dogs. The tumor cells these present-day dogs are receiving are from the original cells of the tumor from around 200 years ago. That is how a dog can be harboring tumor cells that have wolf DNA, though mutated of course.

Also, I don't think the article skirted evolution as a reason for the lessening of the harshness of the cancer in dogs. 200 years is a very short time to develop genetic defenses to a specific kind of cancer. If any species could develop a genetic defense and way to rid themselves of cancer in only 200 years of exposure, that would be amazing.

The reason for the lessening of the cancer is more likely that cancer cells are by their nature unstable, and these cells have been being unstable for over 200 years. It's more likely the accumulation of genetic errors that account for its decreasing harmfulness.

Posted by Natural K

At 11:37 PM, Blogger PWH said...

is on the same subject, but more informative.

Posted by Natural K


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