Immortal dog

Some time more than 200 years ago, a dog or wolf in China or Siberia got cancer. It was a strange type of cancer: the cancer cells were contagious. That cell line is still alive today, and will probably be alive forever.

You may have already read or heard about Henrietta Lacks, the early 20th century woman whose cancerous cell line (called HeLa) was stolen and is now used in medical research. Because of a mutation, that cell line does not die but continues to replicate – which makes it extremely useful for research purposes. HeLa has been “alive” since 1951. But it’s not the oldest cell line in existence.

That trophy goes to the canine transmissible venereal tumour (CTVT). It’s a cancerous tumour that is transmissible from dog to dog. Unlike regular cancers, it’s not a mutation of the host’s cells. Instead, the cancer is made from the cells from a single animal, growing and spreading to dogs across the world. (No-one tell John Carpenter. Please.)

We don’t know much about this animal, but recent research suggests that it was probably a dog or wolf in China or Siberia, and it lived somewhere between 200 and 2500 years ago. Because the cells are effectively clones from that one animal, the cell line is the oldest one in the world. At least, that we know about.

• Canine transmissible venereal tumor
• HeLa