What do you get when you cross an STD with cancer? Probably the worst disease imaginable, or so you would think; but such an infection does actually exist in dogs.
Rather ominously called Canine Transmissible Venereal Tumour (CTVT), the disease is not actually as bad as you might expect; CTVT is rarely fatal and most dogs recover without the need for treatment. It is one of a few examples of a cancer that is directly transmissible by contact; another is Devil Facial Tumour Disease (DFTD). DFTD affects Tasmanian devils and is a somewhat more devastating disease responsible for their endangered species status.
CTVT was brought to my attention through writing an article for Imperial’s student newspaper, Felix, last week. Imperial College researchers have just published a study in the journal Science demonstrating that the contagious cells survive by exhibiting a behaviour never before seen in nature. They “steal” genes from the cells of their canine host by adopting their mitochondria. Mitochondria are often described as “powerhouses” of the cell due to their role in generating energy.
Having been taught throughout my education in biology that mitochondria can only be transmitted through maternal inheritance, this came as quite a shock, and I wanted to know a bit more about this strange cancer.
Fortunately there are no cases of these sorts of directly transmissible cancers in humans…thank goodness! The closest we have is the Human Papillomavirus, which causes genital warts and can cause cervical cancer – though in this case it is the virus that is transmissible and not the cancer itself. A few cases have been recorded of cancer being transmitted from mother to foetus and via organ transplants but these are all very different from a cancer cell that is itself infectious.
Despite being so different from cancers usually found in humans, studies into CTVT are still likely to prove important for human health. According to Dr Clare Rebbeck, one of the authors of the paper recently published in Science “[the research] opens up the potential for treatments in diseases relating to defective mitochondria”. It remains to be seen whether normal cancers also transfer mitochondria, in which case investigations into CTVT could provide insight into tumor growth in general. It is also unknown exactly how this transfer happens but Dr Rebbeck says, “our work reports yet another interesting feature of CTVT and shows just how adaptable and highly evolved these cells are.”
Therefore, although we can breath a huge sigh of relief that humans are not plagued by such a pathogen, research into the doggy disease should not be overlooked. Aside from being fascinating in their own right, these unusual cells could help improve our biological understanding of more conventional cancers.