Tumor DNA ‘treasure’ gives UK researchers hope for new cancer cures

UK cancer researchers have identified dozens of new DNA patterns in cancerous tumours, raising hopes that more effective prevention, treatment and even cures could be a step closer.

The scientists described their findings as a “treasure trove” of new clues to the causes of cancer.

In the largest study of its kind, researchers at Cambridge University Hospitals examined the genomes of more than 12,000 people with cancer in England.

They spotted 58 new patterns in their DNA, called mutational signatures, suggesting there are causes scientists aren’t yet aware of.

The researchers hope that this discovery will allow future studies to determine the root of these carcinogenic mutations.

Scientists were only aware of 51 mutational signatures before the new finding, including changes caused by smoking or UV light.

Identifying these signatures also allows doctors to examine each patient’s tumor and associate it with specific treatments and medications.

British scientists examined 12,000 cancer patients and identified 58 new patterns in their DNA, called mutational signatures

Cambridge University researchers have studied the genetic make-up of more than 12,000 people with cancer in England, enabling them to see the origins of the tumour.  They spotted 58 new patterns in cancer's DNA, suggesting there are causes scientists aren't yet aware of

Cambridge University researchers have studied the genetic make-up of more than 12,000 people with cancer in England, enabling them to see the origins of the tumour. They spotted 58 new patterns in cancer’s DNA, suggesting there are causes scientists aren’t yet aware of

However, the patterns can only be detected in cancer patients whose entire genome has been sequenced by scientists, which is not routinely done.

Professor Serena Nik-Zainal, a genomics expert who led the study, said these patterns are like “fingerprints at a crime scene”.

She said the findings could point to an “Achilles heel” in individual cancers that could be targeted for treatment.

HOW DOES CANCER DEVELOP?

Cancer starts in the cells.

Inside almost every cell in the body is a copy of your genome, made of DNA.

The genome can be thought of as the instructions for making a cell work. It tells the cell what type of cell it should be – like a skin cell or a liver cell – and has instructions that tell the cell when to grow, divide and die.

When a cell divides to become two cells, the genome is copied. Usually this happens in a controlled way and this is how bodies grow and repair themselves.

But sometimes errors occur when copying the genome. This is called mutations.

Errors can be caused by natural processes in cells, by chance, or by external factors, such as UV light or smoking.

Most damage is repaired immediately with no negative effects.

But sometimes mutations in critical genes mean it no longer understands its instructions and multiplies out of control.

The abnormal cell continues to divide and make more and more abnormal cells. These cells form a mass, called a tumour.

Source: Genomics England

Around 1.7 million new cases of cancer are confirmed in the US each year and 375,000 in the UK

Cancer is caused by mutations in the genome of cells, which cause cells to multiply out of control until they form a tumour.

The latest study, published in the journal Science, analyzed the whole genome of 12,222 cancer patients treated by the National Health Service (NHS) as part of the 100,000 Genomes project in England.

Genome sequencing examines the thousands of DNA building blocks in each tumor, showing the mutations that contribute to each person’s cancer.

Some of the novel mutational patterns observed were present in many different cancer patients, while others were rarer.

Cancers are thought to have a finite amount of mutational processes, fueling research to identify them all and what causes them.

Knowing that the signatures are present in a tumor helps determine the root cause and whether the mutation was caused by environmental factors or a genetic problem.

Professor Nik-Zainal told MailOnline: ‘I sometimes use the analogy of footprints in the sand where the mutational signatures are the footprints.

“When you look across a beach, there can be footprints everywhere (analogous to cancer, mutations seem a bit random, they’re everywhere).

“But if you study the footprints in detail, there are characteristics that tell you if the footprints are those of an animal or a human.”

She added: “Mutational signatures are like these footprints. We can begin to determine if something is due to external or cellular factors by studying mutation patterns in detail.

The researchers used their findings to develop an algorithm called Signature Fit Multi-Step (FitMS) that can spot mutational signatures in new cancer genome samples.

Only patients whose complete cancer genome has been sequenced will be able to benefit from this tool, but the team thinks it can be deployed to them “very quickly”.

At present only childhood cancers, specific leukaemias and sarcomas – rare cancers affecting tissues in the body – are sequenced by the NHS, but experts expect this list to be expanded in the years to come.

FitMS will spot these patients’ cancer mutational signatures, which the scientists hope will accelerate the ability to match them to a more specific treatment.

Professor Nik-Zainal said: ‘The reason it is important to identify mutational signatures is that they are like fingerprints at a crime scene – they help identify the culprits of cancer.

“Certain mutational signatures have clinical or therapeutic implications – they may highlight abnormalities that can be targeted by specific drugs or may indicate a potential ‘Achilles heel’ in individual cancers.”

Michelle Mitchell, Chief Executive of Cancer Research UK, said: “This study shows how powerful whole genome sequencing tests can be in giving clues about how cancer may have developed, how it will behave and what treatment options would work best.”

The results can “potentially be used within the NHS to improve the treatment and care of people with cancer”, she added.

Professor Matt Brown, scientific director of Genomics England, said applying mutational indices to patients “could improve the diagnosis and management of cancer patients”.

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