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Tumour genes mapped in major milestone for cancer treatment

21 December 2009
Appeared in BioNews 539

Scientists at the Wellcome Trust Sanger Institute have sequenced the genomes of two cancers - malignant melanoma skin cancer and an aggressive form of lung cancer. Their findings were published in Nature last week and could transform cancer treatments.

The team, led by Dr Mike Stratton, determined the entire DNA sequence of cancer cells from two individuals and compared it to the sequence of their healthy cells. This allowed them to identify all of the DNA changes, or mutations, in the cancerous cells.

The team analyzed the mutations to determine how many there were, what type they were, what caused them and which ones led to the cell becoming cancerous. 'It's like doing archaeological excavation. You've got traces and imprints of all these processes that have been operative for decades before the cancer arose,' said Dr Stratton.

In the lung cancer patient, they discovered over 23,000 mutations that were exclusive to the cancerous cells. Many of these will be harmless, but some will trigger cancer. Most of these mutations were caused by chemicals in cigarette smoke. 'We can say that one mutation is fixed in the genome for every 15 cigarettes smoked,' said Dr Peter Campbell, who led the lung cancer part of the study. Most of the melanoma mutations were caused by ultraviolet radiation.

The research is the first to emerge from a 10-year global consortium that is analysing the genetic makeup of 50 different types of cancer. By understanding the genetic changes behind cancer, scientists hope to develop more powerful and precise anti-cancer drugs.

The DNA sequence will give researcher clues to exactly which mutations are behind the formation of cancers as well as how the cells attempt to repair mutated DNA.

Dr Campbell said: 'The knowledge we extract over the next few years will have major implications for treatment. By identifying all the cancer genes we will be able to develop new drugs that target the specific mutated genes and work out which patients will benefit from these novel treatments.'

Previous studies have looked at mutations in small numbers of genes or in small sections of DNA, but this research determined the entire genetic sequence of cancerous cells. Advances in technology means DNA sequencing can be done more quickly, easily and economically than ever before. 'In the long term, every cancer patient will have this done in a clinically relevant timeframe, so in the six weeks it takes to be seen, biopsied and taken into the clinic,' said Dr Stratton.

Harpal Kumar, chief executive of Cancer Research UK, added: 'The next step will be to find out which of these thousands of mutations are just collateral damage, and which actually drive these cancers. Only then can we begin to find ways to correct or prevent them. Never before has the potential of genomics to bring benefits to patients been so apparent.'

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BBC News |  16 December 2009
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