Human anti-cancer drugs could help treat transmissible cancers in Tasmanian devils

Transmissible cancers are incredibly rare in nature, yet have arisen in Tasmanian devils on at least two separate occasions. New research from the University of Cambridge identifies key anti-cancer drugs which could be trialled as a treatment for these diseases, which are threatening Tasmanian devils with extinction.

A Tasmanian devil. Image credit: JJ Harrison/Wikipedia (CC BY-SA 3.0)

Tasmanian devils are marsupial carnivores endemic to the Australian island of Tasmania. The species is considered endangered due to devil facial tumour 1 (DFT1), a cancer that is passed between animals through the transfer of living cancer cells when the animals bite each other. DFT1 causes grotesque and disfiguring facial tumours, which usually kill affected individuals.

The DFT1 cancer first arose in a single individual devil several decades ago, but rather than dying together with this devil, the cancer survived by ‘metastasising’ into different devils.

Therefore, the DNA of the devils’ tumour cells is not their own DNA, but rather belongs to the individual devil that first gave rise to DFT1 all those years ago. Remarkably, DFT1 cells can escape the devils’ immune systems despite being in essence a foreign body.

The DFT1 cancer was first observed in north-east Tasmania in 1996, but has subsequently spread widely throughout the island, causing significant declines in devil populations.

In 2014, routine diagnostic screening revealed a second transmissible cancer in Tasmanian devils, devil facial tumour 2 (DFT2), which causes facial tumours indistinguishable to the naked eye from those caused by DFT1, and which is probably also spread by biting.

However, analysis showed that the two types of cancer differ at a biological level, and whereas DFT1 first arose from the cells of a female devil, DFT2 appears to have first arisen from a male animal. For now, DFT2 appears to be confined to a peninsula in Tasmania’s south-east.

The team studied the genetic and physical features of the tumours, and compared the two lineages with each other and with human cancers. In doing so, they identified an important role in the tumours for particular types of molecules known as receptor tyrosine kinases (RTKs) in sustaining growth and survival of DFT cancers.

Importantly, drugs targeting RTKs have already been developed for human cancer, and the researchers showed that these drugs efficiently stopped the growth of devil cancer cells growing in the lab. This leads to hope that it may be possible to use these drugs to help Tasmanian devils.

Why Tasmanian devils should be particularly susceptible to the emergence of DFTs is not clear. However, devils bite each other frequently around the facial area, often causing significant tissue injury.

Given the important role for RTK molecules in wound healing, the researchers speculate that DFT cancers may arise from errors in the maintenance of proliferative cells involved in tissue repair after injury. (University of Cambridge)

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