Could the gut microbiome play a key role in preventing childhood leukaemia?

There’s a community inside you. It’s made up of trillions of microbes, including bacteria, fungi and even viruses.  

This is called the microbiome.  

You may have heard of it when talking about gut health. The word might even be on some of your food packaging.  

Now you might be wondering why the microbiome is so important to our health.  

Well, it helps us digest food and control our immune system by keeping the balance between good and bad bacteria. And this can protect us from harmful bugs and bacteria that cause diseases.   

The microbiome is comprised of hundreds of different bacteria mainly located inside the gut. And just like a fingerprint, it’s completely unique to you. It can be influenced by factors like genetics, the environment and lifestyle. 

It’s been a buzzing area of research over the past decade. Researchers have been able to link the microbiome to various diseases, like type 2 diabetes, and even mental health. 

Now, findings from a team of researchers at the Institute of Cancer Research (ICR) in London suggest that the microbiome could also play an important role in the development of acute lymphoblastic leukaemia (ALL) in children.

Starting young

Our microbiome starts developing from birth (and possibly before). Day by day, different microbes begin to populate our gut, but their stay isn’t always permanent. Like a bustling city, there are some which are only there for a short visit, while others may become a settling resident.  

The microbiome can change quickly over the first two years of life, and the unique combination of microbes that live in our guts can depend on our environment when we’re young.   

And a diverse microbiome functions better than one with only a few microbes. That’s because having a wide variety of different microbes can support the immune system and help the body adapt to defend from different pathogens. 

The team at the ICR first shared evidence that the microbiome could play a role in some cases of leukaemia in 2018.  

Leukaemia is the most common type of cancer affecting children. ALL is a blood cancer that starts from white blood cells called lymphocytes in the bone marrow. And it’s the most common type of leukaemia diagnosed in children 0-4 years old, with around 440 children being diagnosed in the UK each year. 

Their research found that a blood cell mutation occurring during early development can cause a small number of children carrying those mutant cells to go on to develop ALL.  

But they also highlighted a second factor that, in combination, triggers this type of cancer.  

The team showed having a weakened immune system can later lead to infections which could trigger other mutations. This, in combination with the blood cell mutation, could lead to ALL. And they hypothesised this could be linked to a lack of microbes present in the gut.

A gut reaction

Recently, in a systematic review funded by Cancer Research UK, the ICR team showed that children with ALL have far less diverse microbiomes than children without the disease. 

“We’ve discovered there’s quite a striking difference between the microbiomes of children with and without ALL,” says Professor Sir Mel Greaves, Professor of Cell Biology at the ICR. 

It’s hard to define what exactly makes up a healthy gut. But researchers agree that overall, a more diverse microbiome is healthier because it improves the immune system. These protective microbes take time to settle, and building diversity doesn’t happen overnight. 

“You have 3 successive waves of different bacteria species coming up in the first three years of life,” Greaves explains.  

These 3 phases consist of a developmental phase (months 3–14), followed by a transitional phase (months 15–30), and a stable phase (months 31–46).  

“And for those with ALL, it’s as if the microbiome is at the beginning phases – it’s less diverse and less mature. And this can have long-term implications for the immune system.” 

The researchers think the lack of diversity means that children’s immune systems are not as well trained to fight off common bugs. And that causes inflammation, which could contribute to ALL.