childhood leukemia, possibly caused by common infections such as the flu

Scientists believe that childhood leukemia is driven by common childhood infections that encounter precancerous cells in the blood.

Experts at the Institute for Cancer Research (ICR) in London have found that babies develop the risk of leukemia in the womb, but will not develop the disease without a second ‘hit’ from a viral or bacterial infection such as the flu.

Research highlights the importance of allowing babies to socialize with other children early in life to prepare their immune systems for infections.

The discovery came by examining pairs of twins who initially developed acute lymphoblastic leukemia (ALL), the most common type of cancer in children, in only one of them.

Identical twins are about 15-25 percent more likely to develop ALL if their siblings already have the disease, while less than one percent of identical twins or other siblings go on to develop the disease.

The researchers followed the twins for up to 15 years and found that the higher risk was only true if identical twins shared a single placenta before birth—which only happens in about 60 percent of identical twins.

Findings ‘confirm disease can be traced back to uterus’

It confirms that the conditions necessary to trigger leukemia first appear in the womb, and that even the healthy twin will carry in their blood “pre-leukemia” cells formed by a spontaneous developmental error and passed between the two.

But clinically silent cells won’t turn into cancer without a postnatal “hit”, possibly from common childhood infections.

Founding Director of the Center for Evolution and Cancer and Professor of Cell Biology at the Cancer Research Institute of London, Prof.

“These new findings confirm that when pre-leukemia cells spread through the twins’ shared blood supply, the disease can be traced back to the womb.

“What has remained a mystery until now is why sometimes only one twin is diagnosed with leukemia.

“We still don’t know for sure what caused the first ‘hit’ of genetic changes in the uterus, but we think the second ‘hit’ of genetic changes was likely triggered by common childhood infections – opening up the possibility of ‘primering’. ‘ The immune system in infancy to prevent the disease from developing later in life.

Acute lymphoblastic leukemia is the most common type of childhood cancer, accounting for 80 percent of leukemia cases in children.

The team is now focused on finding the second infection-induced hit after birth.

Strengthening the gut may protect children against illness

They believe the gut microbiome may play an important role in protecting children against developing leukemia, even if they have precancerous cells. While vaccines have little effect in preventing ALL, strengthening the gut early in life can help.

Prof Greaves added: “The risk of ALL is increased by cesarean delivery, lack of breastfeeding and lack of social contacts during infancy.

Conversely, participation in playgroups during infancy is protective. So, to some extent, the risk can be changed without medical intervention.”

The findings will also allow doctors to assess the risk of ALL for twins by first determining whether the twins are the same and share a placenta, and then regularly monitoring the levels of pre-leukemia cells in their blood.

Sarah McDonald, assistant director of research at Blood Cancer UK, which funded the study, said: “Understanding the mechanism by which cancer develops in identical twins and why only one develops leukemia is an important question to answer.

“It not only helps us understand the risk of developing leukemia in the other sibling, but also provides insight into how leukemia develops in all children.

“This research shows that when one twin develops leukemia and both twins share the same placenta during pregnancy, two events are needed, one before birth and the other after birth, to determine whether the other sibling develops the disease.”

The research was published today in the journal Leukaemia.

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