The link between alcohol and cancer

New research from the UK shows how alcohol damages DNA in stem cells and helps to explain why drinking can increase your risk of cancer.

The study, by scientists at the MRC Laboratory of Molecular Biology in Cambridge has been published in the journal Nature, and used mice to show how alcohol exposure leads to permanent genetic damage.

Scientists gave diluted alcohol (known as ethanol) to mice. They then used chromosome analysis and DNA sequencing to examine the genetic damage caused by acetaldehyde, a harmful chemical produced when the body processes alcohol.

They found that acetaldehyde can break and damage DNA within blood stem cells which leads to rearranged chromosomes and permanently altered DNA sequences in these cells.

Lead author of the study, Professor Ketan Patel, says when the DNA blueprint within stem cells is damaged, it can give rise to cancer.

He says these new findings demonstrate how drinking alcohol increases the risk of developing certain cancers, including common types like breast and bowel.

“Some cancers develop due to DNA damage in stem cells. While some damage occurs by chance, our findings suggest that drinking alcohol can increase the risk of this damage,” he says

The study also examined how the body tries to protect itself against damage caused by alcohol. The first line of defence is a family of enzymes called aldehyde dehydrogenases (ALDH). These enzymes break down harmful acetaldehyde into acetate, which our cells can use as a source of energy.

However, millions of people, particularly those from South East Asia, either lack these enzymes or carry faulty versions of them. This means that when they drink, acetaldehyde builds up and causes them to have a flushed complexion and feel unwell.  

In the study, when mice lacked the critical ALDH enzyme (ALDH2)and were given alcohol, it resulted in four times as much DNA damage in their cells compared to mice with the fully functioning ALDH2 enzyme.

The second line of defence used by cells is a variety of DNA repair systems. Most of the time these DNA repair systems fix and reverse different types of DNA damage, but they don’t always work and some people carry mutations which mean their cells aren’t able to carry out these repairs effectively.

Professor Patel says: “Our study highlights that not being able to process alcohol effectively can lead to an even higher risk of alcohol-related DNA damage and therefore certain cancers. But it’s important to remember that alcohol clearance and DNA repair systems are not perfect and alcohol can still cause cancer in different ways, even in people whose defence mechanisms are intact.”

The research was funded by Cancer Research UK, Wellcome and the Medical Research Council (MRC).

17 April 2018

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