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Similar to an infectious disease: animals can transmit cancer


Researchers uncover transmission of cancer in mussels
Cancer is not an infectious disease, so there is usually no risk of infection for humans. The situation is different for animals, however, because it has been known for an infectious form of cancer exists in dogs. Scientists from Columbia University Medical Center (CUMC) have now discovered that mussels can also spread the disease to other specimens. In view of the new results, the question arises from an expert's perspective what this could mean for the infection of cancer in humans.

Cancer is usually not communicable in humans
Animals can also get cancer. While the disease is not communicable in humans, there is, for example, an infectious form in dogs, which is the so-called "sticker sarcoma" that is rare in Europe. This is mainly transmitted through mucosal contact during sexual intercourse, and dogs can also become infected with the tumor cells by licking and smelling the genitals.

Researchers are studying different types of mussels
Now, American researchers have discovered another animal species that appears to be able to infect other specimens of their species with cancer. As the scientists from Columbia University in New York report in the journal "Nature", these are mussels that can pass on a leukemia-like disease.

In their research, Michael Metzger and his colleagues focused on three types of mussels that they had collected in different regions of Spain and Canada: a mussel species (Mytilus trossulus), the common cockle (Cerastoderma edule) and the golden carpet mussel (Polititapes aureus ). They checked which animals had cancer and then analyzed the genetic material of the cancer cells and that from the healthy tissue. Whether an animal is affected or not can be seen from an excess of large, changed cells in the circulation. In the event of an illness, the body cavity fluid consisting of blood and lymph in the animals (“hemolymph”) appears thickened and cloudy, and the tissue is successively infested with cancer cells.

Results indicate transferability
It was shown that certain genetic characteristics were different in the modified tissue than in the tissue of the healthy animals. In contrast, the scientists discovered that the characteristics matched in the tumors of different types of mussels. This could therefore indicate that the cancer cells were transferred between individual animals, the researchers said.

They also found that in the golden carpet mussel, the infectious cancer cells came from the spotted carpet mussel (Venerupis corrugata) - a related but independent species, in which no cancer has yet been detected in the wild. According to the experts, the spotted carpet shell could possibly have been able to find a way to fight cancer in the course of evolution, so that it is then transmitted in a different way.

Transmission between different species has been an exception so far
"Now that we have observed the spread of cancer among several marine species, our future research will focus on the mutations responsible for these cancer cell transmissions," said the lead author of the study, Dr. Stephen Goff, according to a message from the CUMC. So far it has been assumed that a tumor is normally restricted to one species and that transmission between different species is an exception.

Based on the results of the new study, a total of eight contagious tumor types in animals are now known. In addition to five forms of four types of mussels, science has already proven two transmissible forms of cancer in mammals in recent years. It is a facial tumor that threatens to wipe out the marsupial “Tasmanian devil” (Sarcophilus harrisii) and the “sticker sarcoma” described, which occurs worldwide in dogs.

Cancer does not respect borders
"We thought these things were happening now and in nature and that it was a coincidence. But now the evidence that these seem to be fairly common among bivalve molluscs is changing the perspective, ”says molecular biologist Elizabeth Murchison of the University of Cambridge (UK), commenting on the article in Nature.

The finding that cancer could possibly jump back and forth between different species was "shocking" to the expert and led to the question of what that could mean for humans. So far, transmission from person to person has only become known in rare cases, for example after an organ transplant - cases that only affected the two people involved. Nevertheless, the cancer risk is "innate in multicellular organisms, and the basic evolutionary drive of this disease does not respect individual boundaries and not even species boundaries," Murchison continued. (No)

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