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Colon cancer can be caused by an ordinary intestinal bacterium

A common type of intestinal bacteria can play a role in the development of colon cancer, research suggests.

An international team of scientists has shown that a toxin released by a strain of E.coli – a dangerous bacterium that is usually found in the lower intestine – causes unique ‘fingerprints’ of DNA damage to cells along the intestine.

These patterns were mainly observed in colon cancer tumors, which show “a direct link” between the microbial toxin and the genetic changes that stimulate cancer development.

The toxin in question is called colibactin and it can mutate and multiply in the cells of the stomach wall and cause colon cancer, the second most deadly cancer in the UK.

Scientists have shown that a toxin released by a strain of E.coli - a bacterium usually found in the lower intestine - causes unique patterns or 'fingerprints' of DNA damage to cells along the intestine

Scientists have shown that a toxin released by a strain of E.coli – a bacterium usually found in the lower intestine – causes unique patterns or ‘fingerprints’ of DNA damage to cells along the intestine

What is Colibactin?

Certain E. Coli strains present in the human gut produce colibactin.

It is a small toxin that damages the genetic information in a cell and causes mutations that can lead to cancer.

However, the chemical structure of colibactin and the molecular mechanism underlying its genotoxic effects have remained unknown since it was first discovered in 2006.

Professor Hans Clevers and his team at the Hubrecht Institute in the Netherlands focused on one strain of E. coli that produced colibactin, which is more common in the bowel samples of people with colon cancer compared to healthy people.

Because colibactin can cause DNA damage in cells grown in the laboratory, they thought the toxin could do the same with cells along the intestine in humans.

The team used human gut organoids or miniature replicas of the gut that were cultured in the laboratory and exposed them to colibactin-producing E. coli.

They analyzed the DNA sequence of the intestinal cells in the mock-up intestines after five months and found about twice the DNA damage in them, compared to the dolls exposed to ‘normal’ E. coli that did not produce colibactin.

The researchers also discovered that the DNA damage caused by colibactin followed two very specific patterns – such as a fingerprint – that were unique to the toxin.

To determine whether the DNA damage caused by the bacteria played a role in colon cancer, the researchers then analyzed the DNA sequences of more than 5,500 tumor samples from the United Kingdom and the Netherlands, with the help of Dr. Henry Wood and Professor Philip Quirke from the university. from Leeds.

More than 40,000 Britons are diagnosed with colon cancer every year and it is the second largest cancer killer (file)

More than 40,000 Britons are diagnosed with colon cancer every year and it is the second largest cancer killer (file)

More than 40,000 Britons are diagnosed with colon cancer every year and it is the second largest cancer killer (file)

First they checked the two colibactin DNA damage fingerprints in more than 3600 Dutch samples of different types of cancer. The fingerprints were present in several tumors and much more often in colon cancers than other types of cancer.

The researchers then specifically refined their research into colon cancer tumors and analyzed more than 2,000 colon cancer samples from the UK, collected as part of the Genomics England 100,000 Genomes project.

Of these samples, colibactin fingerprints were present in 4-5% of patients. This suggests that colibactin-producing E. coli can contribute to 1 in 20 cases of colon cancer in the UK.

Scientists said that other bacterial toxins from gut bacteria can have similar effects and the hunt for them is now underway while researchers are trying to determine whether this mechanism of DNA damage is widespread.

Understanding the early triggers that can lead to colon cancer can help doctors prevent its development and detect it at the earliest stage when treatment is most likely to be successful.

There are approximately 42,000 new colon cancer cases in the UK every year.

Understanding the early triggers that can lead to colon cancer can help doctors prevent its development and detect it at the earliest stage when treatment is most likely to be successful.

What is colon cancer and what are the symptoms?

Colon cancer is a general term for cancer that starts in the colon. Depending on where the cancer starts, colon cancer is sometimes referred to as colon or rectal cancer.

Colon cancer is one of the most common cancers diagnosed in the UK. Most people with a diagnosis are older than 60 years.

Symptoms of colon cancer

The 3 most important symptoms of colon cancer are:

  • persistent blood in your poo – that happens for no apparent reason or is associated with a change in bowel movements
  • a persistent change in bowel movements – which usually has to defecate more and your shit can also become more fluid
  • persistent abdominal pain (abdomen), bloating or discomfort – this is always caused by eating and can be accompanied by loss of appetite or significant unintended weight loss

Most people with these symptoms do not have colon cancer. Other health problems can cause similar symptoms. For example:

  • blood in the poo if associated with pain or pain is more often caused by piles (hemorrhoids)
  • a change in bowel movements or abdominal pain is usually caused by something that you have eaten
  • a change in bowel movements to go less often, with harder shit, is usually not caused by a serious condition – it may be worth trying laxatives before visiting your doctor

These symptoms should be taken more seriously as you age and when they persist despite simple treatments.

Source

This led scientists to investigate the role that the microbiome – trillions of bacteria, viruses, fungi and other single-cell organisms – plays in the development of colon cancer.

Further down the line, the researchers said that DNA damage search fingerprints such as those associated with colibactin in the cells of the intestinal wall can be used to identify those at greater risk of developing the disease.

Professor Philip Quirke, co-investigator of Grand Challenge at the University of Leeds, said: “Our goal is to understand the causes of colon cancer, so discovering the role of colibactin is an important step.

“As a Grand Challenge team, we are now looking at other bacteria and their toxins associated with colon cancer, and we hope to identify more fingerprints of DNA damage to get a better picture of risk factors.

‘We will then have to figure out how we can reduce the presence of risky bacteria in the intestine. But this is all in the future, so for the time being people should continue to eat healthily and participate in colon cancer screening. “

John Barnes, advocate of the Grand Challenge, said: “As a cancer survivor, I don’t want others to experience what I’ve been through. Capturing colon cancer at an earlier stage, while still being treatable, can save thousands of people’s lives.

“This brilliant research gives me hope that people may no longer have to suffer from colon cancer in the future.”

Nicola Smith, senior health information manager at Cancer Research UK, said: “The more doctors understand how colon cancer develops, the better they are at detecting and helping people reduce their risk.

“But there are already things people can do now to reduce their risk of colon cancer. No smoking, maintaining a healthy weight, following a high-fiber diet and little red and processed meat all help. And for those who are eligible, participation in bowel screening can help to detect the disease at an early stage. “

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