Do We Know What Causes Childhood Leukemia?

The exact cause of most childhood leukemias is not known. Most children with leukemia do not have any known risk factors.

Still, scientists have learned how certain changes in the DNA inside normal bone marrow cells can cause them to become leukemia cells. Normal human cells grow and function based mainly on the information in each cell’s DNA. The DNA inside our cells makes up our genes, which are the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. But our genes affect more than how we look.

Some genes control when our cells grow, divide into new cells, and die at the right time. Certain genes that help cells grow, divide, or stay alive are called oncogenes. Others that slow down cell division or cause cells to die at the right time are called tumor suppressor genes.

Cancers can be caused by DNA mutations (or other types of changes) that turn on oncogenes or turn off tumor suppressor genes. These gene changes can be inherited from a parent (as is sometimes the case with childhood leukemias), or they may happen randomly during a person’s lifetime if cells in the body make mistakes as they divide to make new cells.

A common type of DNA change that can lead to leukemia is known as a chromosome translocation. Human DNA is packaged in 23 pairs of chromosomes. In a translocation, DNA from one chromosome breaks off and becomes attached to a different chromosome. The point on the chromosome where the break occurs can affect oncogenes or tumor suppressor genes. For example, a translocation seen in nearly all cases of childhood chronic myeloid leukemia (CML) and in some cases of childhood acute lymphocytic leukemia (ALL) is a swapping of DNA between chromosomes 9 and 22, which leads to what is known as the Philadelphia chromosome. This creates an oncogene known as BCR-ABL. Many other changes in chromosomes or in specific genes have been found in childhood leukemias as well.

Some children inherit DNA mutations from a parent that increase their risk for cancer (see the section “ What are the risk factors for childhood leukemia?”). For instance, a condition called Li-Fraumeni syndrome, which results from an inherited mutation of the TP53 tumor suppressor gene, increases a person’s risk of developing leukemia, as well as some other cancers.

Certain inherited diseases can increase the risk of developing leukemia, but most childhood leukemias do not seem to be caused by inherited mutations. Usually, DNA mutations related to leukemia develop after conception rather than having been inherited. Some of these acquired mutations might occur early, even before birth. In rare cases, acquired mutations can result from exposure to radiation or cancer-causing chemicals, but most often they occur for no apparent reason.

A few studies have suggested that some childhood leukemias may be caused by a combination of genetic and environmental factors. For example, certain genes normally control how our bodies break down and get rid of harmful chemicals. Some people have different versions of these genes that make them less effective. Children who inherit these genes may not be as able to break down harmful chemicals if they are exposed to them. The combination of genetics and exposure might increase their risk for leukemia.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: April 17, 2015 Last Revised: February 3, 2016

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.