Why some types of leukemia mainly affect young children

According to the Josep Carreras Foundation, the leukemia it is the most frequent childhood cancer: it accounts for 30% of pediatric cancers with a total of 300 new cases in Spain every year. 80% are acute lymphoblastic (ALL) and the highest incidence It occurs between 2 and 5 years. In all subtypes of the disease can be detected chromosomal translocations (displacement of one fragment of chromosome to another) and molecular alterations which vary the prognosis and treatment of the disease.

It manifests itself in various forms, and subtypes that primarily affect children generally They progress rapidly and require immediate and aggressive treatment. There are similarities between children and adults, but evidence suggests that cancers They don't share the same genetic roots.

"What has been known for some time is that there are clear genetic differences between the leukemia of a child and an adult," he says. Thomas Mercher, hematology-oncology research director of the National Institute of Medical and Health Research of France and Gustave Roussy, from the Research Institute of Villejuif to 'Live Science'. Studies suggest that the specific genetic peculiarities observed in the cells of this disease in children may arise very early and even in the uterus, but the way in which this happens step by step "is generally not very clear," they add.

Mutations

New research suggests that this type of leukemia may being able to 'kidnap' only young cells in development such as those found in fetuses and children and not the mature adults. To make the discovery, the scientists used genetic samples in a particularly aggressive way that some children suffered and replicated them in mice.

The study, published in 'Cancer Discovery', suggests that this type of cancer appears before two years. "These alterations that we study are only found in childhood leukemia. In 2012, the team gathered cells of small and adult ages that had AML-M7 (a rare subtype), discovering a key difference between genetic material. Many of the cells in the children contained genes that had merged to form new hybrid genes.

Madrid researchers identified genetic mutations in the PHF6 gene that contribute to the development of acute lymphoblastic leukemia

"Individually, these play an important role in the development of blood cells, but once united, these genes can direct them to build unusual proteins and finally transform them into cancerous, "the experts explain. After several investigations and observations of the behavior of these cells, the scientists concluded that by activating one of the mutations (ETO2-GLIS2), the resulting they seemed to alter cell pathways that normally make them healthy.

The results "show that it should pay attention to the environment of the fetal bone marrow where hematopoietic stem cells can be found, "he says Mignon Loh, a pediatric hematologist-oncologist at the University of California. "Research on ETO-GLIS2 can also shed light on how other forms of childhood leukemia depend on fusion genes, as long as the team's findings in mice are true in humans," he adds.

Other studies

In 2010, researchers from the Severo Ochoa Molecular Biology Center in Madrid participated in an international study that identified genetic mutations in the PHF6 gene that contribute to the development of acute lymphoblastic T-cell leukemia (T-ALL, according to its acronym in English). This gene that is encoded on the X chromosome, linked to the female sex, and expressed in a single copy in the male genome.

The study suggests that this type of cancer appears before two years. "These alterations are only found in childhood leukemia"

The authors have discovered losses of fragments and mutations that deactivate this gene in 16% of the pediatric leukemia analyzed and 35% of adult samples. "This type of leukemia has a higher incidence in men, in a proportion of three cases for each affected woman. This fact suggested the existence of a possible tumor suppressor factor in this type of ailments, which should be linked to X chromosome. Our work demonstrates its existence. "

The group of acute lymphoblastic leukemias represents more than a quarter of the cancers diagnosed in children under 15 years and T-ALL accounts for 15% of cases. It is a cancer located in the blood and bone marrow caused by an abnormal growth of a type of white blood cells, T lymphocytes. Its prognosis is favorable, although it depends on the age and the stage of disease progression.

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