Marking a major step forward in cancer research, a team from Britain’s Wellcome Trust Sanger Institute has outlined a complete map of the genes and underlying mutations in the melanoma and lung cancers of two patients.

"Today for the first time, in two individual cancers, a melanoma and a lung cancer, we have provided the complete list of abnormalities in DNA in each of those two cancers," researcher Mike Stratton told the BBC. "We now see uncovered all the forces that have generated that cancer and we now see all the genes that are responsible for driving those two cancers.”

Even more astonishing is the fact that most of the mutations, the researchers say, are traceable back to the damaging effects of UV light or tobacco smoke, for the skin cancer and lung cancer, respectively.

The number of mutations involved in the two forms of cancer is stunning: 33,345 for melanoma and 22,910 for lung cancer. Even more astonishing is the fact that most of the mutations, the researchers say, are traceable back to the damaging effects of UV light or tobacco smoke, for the skin cancer and lung cancer, respectively. This finding underlines the idea that these two forms of cancers are in large part the result of preventable causes.

Stratton points out that being able to trace a cancer back to the specific mutations that caused it will help researchers and clinicians devise more effective modes of treatment. "Now that we have these comprehensive complete catalogues of mutations on individual cancers, we will be able to see how each cancer developed, what were the exposures, what were the environmental factors and that's going to be key for our understanding generally of how cancers develop."

He adds that "for our individual patients, we will see all the genes that are abnormal and are driving each cancer and that's really critical, because that will tell us which drugs are likely to have an effect on that particular cancer and which are not."

Researcher Peter Campbell describes how mutations damage a genome – a somewhat abstract concept to most – with a familiar example: "Every pack of cigarettes is like a game of Russian roulette. Most of those mutations will land where nothing happens in the genome and won't do major damage, but every once in a while they'll hit a cancer gene."

The findings were presented in the January 14th issue of the British journal Nature.