Infected Tasmanian Devils Reveal How Cancer Cells Evolve in Response to Humans

Tasmanian Devil Facial Tumour Disease (DFTD) has ravaged the world’s largest carnivorous marsupial since it emerged in 1996, resulting in a population decline of over 90%. Conservation work to defeat the disease has including removing infected individuals from the population and new research in Evolutionary Applications explains how this gives us a unique opportunity to understand how human selection alters the evolution of cancerous cells.

DFTF is an asexually reproducing clonal cell line, which during the last 16 years has been exposed to negative effects as infected devils, approximately 33% of the population, have been removed from one site, the Forestier Peninsula, in Tasmania between 2006 and 2010.

However, this parasitical disease has been able survive and counteract the effect of deleterious mutation, genomic instability as well as being able to infect more than 100,000 devils.

“In this study, we focus on the evolutionary response of DFTD to a disease suppression trial,” said Beata Ujvari, from the, The University of Sydney. “Tumours collected from devils subjected to the removal programme showed accelerated temporal evolution of tetraploidy compared with tumours from other populations where no increase of tetraploid tumours were observed.”

The disease eradication trial provides a unique opportunity to discover the long-term effects of human selection on DFTD evolution and to explore this, the team collected tumour tissue samples between 2006 and 2011 at 11 sites within the DFTD affected areas of Tasmania.

“Our study clearly demonstrates that DFTD tumours are able to rapidly respond to increased selection and adapt to a selective regime,” said Ujvari. “The results suggest that ploidization may offer yet another pathway to which DFTD is able to adapt to the ever-changing evolutionary landscape sculptured by the devils’ immune system. Our study is the first to show that anthropogenic selection may enhance cancer evolution in the wild, and it therefore cautions about what measures we employ to try to halt the spread of this devastating disease.”

1 COMMENT

  1. It is difficult to understand of course , if so much has been already known about the `natural history and transmission of the disease` why conservationists and veterinarians in charge in Tasmania let it go and allow DFTD to spread so far ? Which has emerged only recently in 1996, and resulting in a population decline of over 90% . Neglect as well as lack of funds and organization are all dominant factors here obviously . Since this is rather UNIQUE Cancer Cell Clone Transmission true `biting and injecting cancer cells in between two individuals it is really interesting and rare ` among all species currently exist in the world .
    Tasmanian DFTD (Devil Facial Tumor Disease) `is primarily `unique` Contact Transmitted Cancer Cell Disease between individual members of the population – biting each other at the head and neck during mating behavior- and Cancer Cells being transmitted with the bite to another individual who has –no `different` natural HLA type diversity and so cellular immunity defense to differentiate between self/non-self – against the other individual Cancer Cells .
    It is known that the isolated and inbreed populations in Tasmanian island have similar problems and very poor diversity not only Transmitting the Cancer Cells originating from one individual and being transmitted generation after generation through –biting and Cancer Cell Injecting- in between each other , but also `lack of diversity` and `inbreeding` predisposed them to other infectious diseases that they have never been exposed before and to be extinct as a result as well . In fact the real problem Tasmanian Devils face is `lack of variability-diversity- and inbreeding in an isolated island so long , rather than recently 1996 Discovered unique Clonal Parasitic type Cancer Cell Transmission in between individuals through biting each other during mating so called DFTD .
    The solution and the cure specifically for the DFTD is relatively simple and easy like any other infectious disease transmitted with contact (biting during mating in this case) and I have few suggestions :
    A- You have to IDENTIFY and ISOLATE and SEPARATE the adult Tasmanian Devils who had already contacted the disease in early or late stages ; from the unaffected ( not bitten ones ) . Since the disease is NOT genetically transmitted but Cancer Cell Clone lines transmitted through `transplantation by biting behavior ` among population of Tasmanian Devils with no cellular immunity diversity/variability in between each other . Especially the isolation time is important which should start before the `mating/biting cycle starts ` in between Juvenile Tasmanian Devils , some adults as well as Juveniles might have contacted the Cancer Cell lines already from their parents or partners . The Tasmanian devil is said to be a solitary animal, but at times is also highly social, such as when feeding communally, or during the breeding season . Mating usually occurs over a short, intense period in March, but can continue into July . It is also said and observed that the female exhibits little in the way of fidelity, visiting several males in quick succession –Evolutionary behavior` to increase diversity ` – with same biting behavior each other , whilst each male, uncertain of their own paternity, will try to physically prevent the promiscuous female from leaving . After a three week gestation period, the female gives birth to two to four young that immediately attach to one of four teats in the backward-opening pouch. At around five months old, the fully-furred young emerge from the pouch and take up residence in a simple, grass-lined den. Another month on, and they start to explore the den’s surroundings, eventually becoming fully weaned and independent at about ten months old . Sexual maturity is reached towards the end of the second year, with an average life expectancy of around five to six years in the wild .
    B- At the second stage you have to start planned `DIVERSIFICATION `separation in different geographical locations ` and controlled breeding in order to increase `variability` among the individuals , inbreeding type of mating behavior may be evolutionary pattern among Tasmanian Tigers in other words they are `predisposed ` to inbreed . The inbreeding cycle if in reality really exists –which I doubt it – rather than manifestation of being isolated in the island so long that can be changed by controlled dispersion and increasing –planned contact and breeding in between diverse genetic makeup individuals – of Tasmanian Devils .

    Thank you

    Detailed in depth characteristics of the DFTD of Tasmanian Devil at the link
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3281993/
    http://eol.org/pages/311781/details

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