One of the few known transmissible cancers - a type of cancer that can spread between individuals through living cancer cells that is considered to be extremely rare - is the cancer that causes facial tumors in Tasmanian devils. Now, University of Cambridge researchers have discovered a second contagious form of cancer in Tasmanian devils that might cause us to rethink our current understanding of these unique diseases.
"The second cancer causes tumors on the face that are outwardly indistinguishable from the previously discovered cancer," Ruth Pye, first author of the study, said in a press release. "So far it has been detected in eight devils in the southeast of Tasmania."
Transmissible cancer is currently threatening Tasmanian devils with extinction, and outside of the species, there are only two other known forms of transmissible cancer - in dogs and in soft-shelled clams.
"Until now, we've always thought that transmissible cancers arise extremely rarely in nature," said Elizabeth Murchison, a senior author on the paper, "but this new discovery makes us question this belief."
Although cancer typically occurs when cells in the body proliferate uncontrollably and invade it through "metastasis," the cancerous cells typically do not survive beyond the host's body. However, transmissible cancer cells have the ability to spread beyond the body of the host and invade new hosts.
"Previously, we thought that Tasmanian devils were extremely unlucky to have fallen victim to a single runaway cancer that emerged from one individual devil and spread through the devil population by biting," Murchison said. "However, now that we have discovered that this has happened a second time, it makes us wonder if Tasmanian devils might be particularly vulnerable to developing this type of disease, or that transmissible cancers may not be as rare in nature as we previously thought."
"It's possible that in the Tasmanian wilderness there are more transmissible cancers in Tasmanian devils that have not yet been discovered. The potential for new transmissible cancers to emerge in this species has important implications for Tasmanian devil conservation programmes," said Gregory Woods, a senior author on the paper.
The findings were published in the Nov. 30 issue of the Proceedings of the National Academy of Sciences.
