First of its kind, it lays bare every genetic mutation the patients have acquired over their lifetime that eventually caused healthy cells in their bodies to turn into tumours.
“This is a really fundamental moment in the history of cancer research.

We have never seen cancer revealed in this way before,” said Mike Stratton, a co-leader of the Cancer Genome Project at the Wellcome Trust Sanger Institute near Cambridge. The researchers took diseased cells from a 45-year-old man with a type of skin cancer called malignant melanoma, and from a 55-year-old man with small cell lung cancer. They then used advanced genetic sequencing machines to read the full genomes.

In the case of the lung cancer patient, they discovered 23,000 mutations that were exclusive to the diseased cells. Almost all were caused by the 60 or so chemicals in cigarette smoke that stick to DNA and deform it. “We can say that one mutation is fixed in the genome for every 15 cigarettes smoked,” said Peter Campbell, who led the lung cancer part of the study. “That is frightening because many people smoke a packet a day.”

Genetic sequencing of the skin cancer cells revealed 33,000 mutations caused by exposure to direct sunlight.