Tumour has it: cancer’s culprit is finally uncovered

World

Tumour has it: cancer’s culprit is finally uncovered

Researchers have figured out how carcinogens change the genetic code of DNA to form cancerous cells

Sarah Knapton


The cause of cancer is written into the DNA of tumours, scientists have discovered, in a breakthrough that could finally show how much the disease is attributable to factors such as air pollution or pesticides.
Until now the roots of many cancers have proved elusive, with doctors unable to tease out the impact of myriad carcinogenic causes that people encounter every day.
In the case of lung cancer, it is not known 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.
Now scientists at Cambridge University and King’s College London have 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 the biggest culprit.
The researchers have released a catalogue of the signatures caused by 41 environmental agents linked to cancer.
“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 at Cambridge.
“They allow us to treat tumours as a crime scene and, like forensic scientists, allow us to identify the culprit – and their accomplices – responsible for the tumour.”
About 360,000 people are diagnosed with cancer in the UK alone each year, and 163,000 will die from the disease.
About 38% of cases are thought to be preventable, but the study helps 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 that occur because of factors such as ultraviolet light, alcohol or tobacco smoke, leading to, for example, an A becoming a G.
As cells divide and multiply, they make copies of their DNA, so any mistakes are reproduced. Over time, the number of errors accumulates, leading to uncontrolled cell growth – the development of tumours.
Each cancer-causing factor changes the code in a slightly different way.
“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 Prof David Phillips, who led the King’s College team.
“It should allow us to examine a patient’s tumour and identify some of the carcinogens they have been exposed to that may have caused the cancer.”
“Our reference library will allow doctors in future to identify those culprits responsible for causing cancer,” added 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.
– © Telegraph Media Group Limited (2019)

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