Devil Facial Tumor Disease (DFTD)
Devil facial tumor disease (DFTD) is a transmissible cancer that affects Tasmanian devils (Sarcophilus harrisii) and is spread between individuals by biting.
The cancer lineage as an infectious agent
DFTD was first observed in 1996 in northeast Tasmania and has since spread across most of the island, reducing devil populations by roughly eighty percent in affected areas. The cancer arose from a single founder tumor in a Schwann cell and passes directly from animal to animal as an allograft: a devil that bites an infected individual receives living cancer cells, which implant and grow into disfiguring facial tumors that kill within months, typically by metastasis or by interfering with feeding.
Devils are outbred enough that allografts between individuals would normally be rejected, and one lineage of DFTD evades rejection by down-regulating major histocompatibility complex molecules on the tumor cell surface. The tumor lineage has persisted and evolved in the devil population for decades, acquiring thousands of somatic mutations while remaining a single clonal line — a cancer that behaves, in transmission and phylogeny, like a parasite.
Related
- CTVT — the canine transmissible venereal tumor, the oldest known cancer lineage
- HeLa cells
- De-darwinization