Abstract
Tasmanian devils have spawned two transmissible cancer clones, known as devil facial tumour 1 (DFT1) and devil facial tumour 2 (DFT2). DFT1 and DFT2 are transmitted between animals by the transfer of allogeneic contagious cancer cells by biting, and both cause facial tumours. DFT1 and DFT2 tumours are grossly indistinguishable, but can be differentiated using histopathology, cytogenetics or genotyping of polymorphic markers. However, standard diagnostic methods require specialist skills and equipment and entail long processing times. Here, we describe Tasman-PCR: a simple polymerase chain reaction (PCR)-based diagnostic assay that identifies and distinguishes DFT1 and DFT2 by amplification of DNA spanning tumour-specific interchromosomal translocations. We demonstrate the high sensitivity and specificity of this assay by testing DNA from 546 tumours and 804 normal devils. A temporal–spatial screen confirmed the reported geographic ranges of DFT1 and DFT2 and did not provide evidence of additional DFT clones. DFT2 affects disproportionately more males than females, and devils can be co-infected with DFT1 and DFT2. Overall, we present a PCR-based assay that delivers rapid, accurate and high-throughput diagnosis of DFT1 and DFT2. This tool provides an additional resource for devil disease management and may assist with ongoing conservation efforts.
Highlights
Tasmanian devils (Sarcophilus harrisii) are marsupial carnivores endemic to the Australian island of Tasmania
We considered the following three explanations for the 13 remaining confirmed devil facial tumour 1 (DFT1) tumours which did not amplify DFT1-A: (i) they belong to a DFT1 subclone which diverged from a clonal ancestor prior to DFT1-A being acquired; (ii) they belong to a DFT1 subclone which lost DFT1-A, or acquired mutations within the DFT1-A primer binding sites or (iii) the biopsy used for DNA extraction included only non-neoplastic host tissue, or included devil facial tumour disease (DFTD) cells at levels that were undetectable under our polymerase chain reaction (PCR) and gel electrophoresis conditions
We present a PCR-based genetic diagnostic test for DFTD, Tasman-PCR, which complements existing diagnostic methods to provide rapid and cost-effective confirmation of DFT1 and devil facial tumour 2 (DFT2)
Summary
Tasmanian devils (Sarcophilus harrisii) are marsupial carnivores endemic to the Australian island of Tasmania. This species is affected by two transmissible cancers, known as Tasmanian devil facial tumour 1 (DFT1) and Tasmanian devil facial tumour 2 (DFT2). DFT1 and DFT2 manifest as facial tumours collectively known as devil facial tumour disease (DFTD) and are transmitted between animals by the direct transfer of living allogeneic cancer cells, probably by biting [1,2]. DFT1 was initially reported in 1996 in northeast Tasmania and is widespread across the island, causing significant declines in devil populations [5,6,7]. DFT2, on the other hand, which was first observed in 2014, has been reported in only five animals, all located in the Channel, an approximately 550 km peninsula in Tasmania’s southeast [2]
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