Cancer causes the genetic code of DNA to change and the alterations can now be read
The cause of cancer is written into the DNA of tumors, scientists have discovered, in a breakthrough which could finally show how much disease is attributable to factors like air pollution or pesticides.
Until now the roots of many cancers have proved elusive, with doctors unable to tease out the impact of a myriad of carcinogenic causes which people encounter everyday.
Even with lung cancer, it is not known just how much can be attributed to smoking and how much could be linked to other factors, such as living by a busy road, or inhaling pollutants at work.
But now scientists at Cambridge University and King’s College London have shown that tumors hold information like a ‘black box’ pointing to the cause of disease.
They exposed stem cells to dozens of known carcinogens and recorded how each alters its DNA code as cancer forms. It provides a ‘fingerprint’ or ‘mutational signature’ of the underlying cause and could even show which was the biggest culprit.
The genomes of cancer types with the colors representing different environmental factors CREDIT: CAMBRIDGE UNIVERSITY
The researchers have today released a catalogue of the signatures caused by 41 environmental agents linked to cancer so that scientists and doctors can understand its origin.
“Mutational signatures are the fingerprints that carcinogens leave behind on our DNA, and just like fingerprints, each one is unique,” said Dr Serena Nik-Zainal from the Department of Medical Genetics and MRC Cancer Unit at the University of Cambridge, who led the Cambridge Team.
“They allow us to treat tumors as a crime scene and, like forensic scientists, allow us to identify the culprit – and their accomplices – responsible for the tumor.”
Around 360,000 people are diagnosed with cancer in Britain each year, and 163,000 people will die from their disease. It is thought that around 38 per cent of cases are preventable, but the new study helps to give a better estimation of exactly how deadly environmental factors can be.
The human genetic code is written in molecules known as nucleotides, represented by the letters A, C, G and T. The new technique works by studying ‘spelling mistakes’ or mutations in DNA which occur because factors such as ultraviolet light, alcohol of tobacco smoke, such an A becomes a G.
As cells divide and multiply, they make copies of their DNA, so any spelling mistakes will be reproduced. Over time, the number of errors accumulates leading to uncontrolled cell growth – the development of tumors. And each cancer-causing factor changes the code in a slightly different way.
The technique is so powerful it can even show which individual chemicals in tobacco smoke were to blame for lung tumors.
“We’ve used this technique to create the most comprehensive catalogue to date of the patterns of DNA damage produced by environmental agents across the whole human genome,” said Professor David Phillips, who led the King’s College London team.
“It should allow us to examine a patient’s tumor and identify some of the carcinogens they have been exposed to that may have caused the cancer.”
The team also identified the fingerprints left behind by common chemotherapy drugs, some dietary chemicals and some present in diesel exhaust fumes, showing just how vulnerable human DNA is to environmental contaminants.
“Our reference library will allow doctors in future to identify those culprits responsible for causing cancer,” added Dr Nik-Zainal.
“Such information could be invaluable in helping inform measures to reduce people’s exposure to potentially dangerous carcinogens.”
The research was published in the journal Cell.
Via The Telegraph