Leukemia is contagious

leukemiaCancer is contagious in mussels

The virologist Stephen Goff of New York's Columbia University unexpectedly received a call for help from a marine researcher a few years ago. Carol Reinisch had long been looking for the cause of a disease that occurs in sand gape clams on the entire east coast of the USA and Canada. The mussels suffer from a form of leukemia in which certain cells in their blood-like body fluid, the hemolymph, multiply uncontrollably until the animals die of it. Carol Reinisch believed that there was a virus behind the disease. Stephen Goff recalls:

"She told me about this mussel disease that I had never heard of before. We are researching retroviruses here, especially the mouse leukemia virus. Up until then, we didn't know anything about mussels. But she said: I'll send you some mussels with leukemia, I'll send you samples of the hemolymph and the cells it contains. Could you please check whether there is a virus in it. And we said: Of course we can. "

"It is a contagious form of cancer"

When Stephen Goff examined the diseased mussels and their hemolymph, he found no viruses, but noticeable genetic changes in the tumor cells. In order to decipher their origin, he sequenced and compared the DNA of the tumors with the genetic material of other cells in the mussels. The samples for this came from various sand gape clams, collected between New York and the Canadian Prince Edward Island, some more than 500 kilometers apart.

"We found that all tumor cells did not genetically match the animals in which they were found. The tumors did not develop from the typical cells of the animals. In addition, all tumors, up and down the east coast, were genetically identical to one another. That can only be explained by the fact that this tumor spreads from animal to animal as a cell clone. It is therefore a contagious form of cancer. "

It is still completely unclear how the tumor cells spread in the sea. Sand gape clams are sedentary animals that spend their lives buried in the silt and hardly ever have direct physical contact with one another. Nevertheless, the leukemic tumor cells have to somehow get out of one mussel and into another - even over great distances.

"In a way, it is similar to the development of metastases in a human being. An important question in cancer research is how tumor cells leave the tumor in one place, spread through the blood or lymph and finally find a new place in the body where they can again be found What we're seeing in mussels is something like the expanded version of it. The tumor cells can even migrate to another body and successfully colonize there. We're dying to understand how they do it. "

Unlikely in humans

Stephen Goff considers it very unlikely that people could also contract other people's tumors in a similar way.

"Vertebrates like humans have a strong immune system that would simply reject a foreign tumor like this one. If someone had leukemia, I wouldn't worry about contracting leukemia."

However, this is apparently possible in molluscs with a less developed immune system. Stephen Goff and Carol Reinisch want to next investigate to what extent leukemia is caused by contagion in other mussel species as well. Perhaps the tumor cells could even spread not only across body but also across species.