Friday, August 2, 2019

Sexually Transmitted Cancer

                 CTVT, or Canine Transmissible Venereal Tumor, is the world's oldest cancer lineage. Interestingly enough, this cancer is transmitted sexually from dog to dog, and manifests itself as genital tumors. This cancer is one of the only known cancers that transmits through touch. Due to the fact that this cancer is transmitted sexually, it has been able to survive for millenia by being transferred from one dog to the next. An original "founder dog" must have had this mutation, which it then passed on. Being roughly 6,000 years old, the study of this cancer lead insight into the evolution of cancer. CTVT is essentially a living biomarker, with the history of it's mutagenic environment recorded on it as it passes from generation to generation and around the world. Normally cellular cancer dies when the host passes. However, this cancer has been passed on for thousands of years serving as a record of it's genetic mutations along the way.
             In order to really understand  CTVT cells, researchers gathered samples from over 500 globally distributed dogs. By analyzing the DNA the team was able to create a phylogenetic tree, which helped them trace the disease around the world. In studying how the cancer cell mutated, and during which time, they were able to trace the origins of the cancer to China around 6,000 years ago. From China, the cancer spread though Asia and into Europe, eventually making it's way to America.
           The CTVT has revealed seemingly unthinkable questions, how come the cancer does not display normal cancerous traits, like genomic instabiltiy? The cancer is mutated greatly from it's original form, but it has been around for 6,000 years. Researchers have not been able to figure out why this cancer mutates at a rate much slower than one would expect. Due to it's slow mutation rate, almost all dogs can be cured by chemotherapy, as the cancer does not evolve a resistance to drugs.  What scientists are truly curious about it the role of this cancer. It seems almost like the dogs and cancer can co-exist with each other.  As if the tumor and the dogs immune system are not competing with each other how a normal cancer would. It almost appears as the CTVT is a cancer but acts as a parasite.
       This was an awesome study, that was actually published today, so I feel really fortunate that I may have been one of the first people I know to really read about this. I truly do not know much about cancer biology, but I do know that I have never heard of sexually transmitted cancer. Thankfully for the dogs, chemotherapy can cure them almost all the time! This was still an interesting article to give a grasp about how much we have yet to learn about the world around us.

https://science.sciencemag.org/content/365/6452/eaau9923
https://www.theatlantic.com/science/archive/2019/08/ctvt-tumor-broke-all-rules/595246/
https://science.sciencemag.org/content/365/6452/440

          

3 comments:

  1. This is a very interesting study and shows the diversity of how different organism have different disease paths. While it seems to be more latent in dogs it is still cancer. In tracking the history of and evolution of cancer in dogs we may be able to develop newer and more effective treatment methods to cure humans. Another thing that is interesting is that this cancer can be transmitted through sexual contact, something I've also never heard of.

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  2. Hi Joe, Very interesting. This study shows how diseases interact within different organisms. No matter the stage, cancer is cancer. Whether it be in dogs or humans it is awful. With pedigrees and evolutionary advances in humans and dogs, more effective treatments may be able to be discovered. Our feline friend may just hold the key to that. Its very interesting that cancer is actually capable of being spread through sexual contact much like HIV or syphilis.

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  3. I found this article to be extremely interesting because it's the first type of cancer that is actually spread through physical interaction. I also found it interesting that chemotherapy was a source of a cure to the disease rather than the symptoms itself. It's intriguing to learn about how different species react to specific diseases. I feel as if we studied how dogs overcame this type of cancer it could potentially lead to some insight with the human bodies machinery to fight off cancer as well.

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