![]() DFT1 was first identified in 1996 in the northeast of Tasmania ( Hawkins et al., 2006), but has since spread widely, causing close to 100% mortality and drastic decline of affected populations ( Hamede et al., 2015). Although both cancers have similar gross morphology, causing tumours on the face, neck and oral cavity, genetic analysis shows that they emerged in different individuals ( Pearse and Swift, 2006 Pye et al., 2016b Stammnitz et al., 2018). The Tasmanian devil is the only mammalian species in which two independent contagious cancers exist, Devil Facial Tumour 1 (DFT1) and Devil Facial Tumour 2 (DFT2) ( Pye et al., 2016b). Understanding the role of MHC in DFT2 could lead to better ways to prevent rejection following transplants.Ĭontagious cancers have emerged and circulate in two species of mammals (dogs and Tasmanian devils) and four species of molluscs ( Metzger et al., 2015, 2016 Novinski, 1876 Pearse and Swift, 2006). In addition, there are many similarities between contagious cancer cells and organ transplants. These results could also reveal how other cancers avoid the immune system and may help to detect them during treatment. While DFT2 provides a unique opportunity to study an emerging cancer as it develops, this research will also help to protect the devils and may lead to effective vaccines. As top predators, devils are key to the ecosystem in Tasmania and their preservation is vital. These two contagious cancers threaten the future of the Tasmanian devil. This means DFT2 could, with time, become as contagious as DFT1. Further analyses also reveal that the cancer cells are slowly evolving to lose their MHCs. This finding may explain how the cancer can spread undetected in these animals, because the immune system does not recognize it as coming from outside the body. Biochemical tests showed that the DFT2 cells do carry MHCs, but that the MHC barcodes of DFT2 are similar to those of the devils infected with the disease. have now examined the MHC on cells from DFT2 cancers, including cells grown in the laboratory and cells taken from cancer biopsies. In 2014, scientists identified a new Tasmanian devil cancer named DFT2, but it was unclear how this second cancer evades the immune system as it spreads from host to host.Ĭaldwell et al. DFT1 can avoid the immune system and spread to new hosts because it has lost MHC. The immune system uses these molecules to help it tell the difference between the body’s own cells and those from elsewhere. Each healthy cell carries molecules known as the major histocompatibility complex (MHC) that act as a barcode showing where each cell comes from. This challenge became more urgent in 2014, when the second contagious cancer, DFT2, was discovered circulating in the population.Ĭontagious cancers are rare because the immune system usually eliminates cells coming from outside the body. Preserving the few remaining healthy devils has been a major challenge for conservationists. ![]() Since it emerged in the 1990s, DFT1 has killed 60–90% of the devil population. These tumours are known as Devil Facial Tumour 1 (or DFT1) and Devil Facial Tumour 2 (or DFT2) both cause tumours round the faces of infected devils. Remarkably, two examples have emerged in a single species, the Tasmanian devil, a marsupial carnivore. While cancer cells typically cannot spread between individuals, there are a few examples of contagious tumours.
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