Do we know what causes Wilms tumor?
Although there is a clear link between Wilms tumors and certain birth defect syndromes and genetic changes, most children with this type of cancer do not have any known birth defects or inherited gene changes.
Researchers do not yet know exactly why some children have Wilms tumors, but they have made great progress in understanding how normal kidneys develop, as well as how this process can go wrong, leading to a Wilms tumor.
The kidneys develop very early as a fetus grows in the womb. Changes (mutations) in certain genes in cells may lead to problems as the kidneys develop. Some of the cells that are supposed to develop into mature kidney cells stay as early kidney cells instead. Clusters of these early kidney cells sometimes remain after the baby is born. Usually, these cells mature by the time the child is 3 to 4 years old. If this does not happen, the cells may somehow begin to grow out of control. The result is a mass of primitive cells that may develop into a Wilms tumor.
Normal human cells grow and function based mainly on the information contained in each cell's chromosomes – long molecules of DNA in each cell. DNA is the chemical in each of our cells that makes up our genes – the instructions for how our cells function.
Some genes control when our cells grow, divide into new cells, and die. Certain genes that help cells grow and divide 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 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 cancers) or may happen during a person's lifetime as cells in the body divide to form 2 new cells.
Changes in certain genes increase the chance that some kidney cells will remain in an early form and turn into a Wilms tumor.
For example, a small number of Wilms tumors are caused by inherited changes (mutations) in or loss of the WT1 or WT2 genes, which are tumor suppressor genes found on chromosome 11. Changes in these genes lead to overgrowth of certain tissues. That is why other abnormalities, like some of those described in the section, “What are the risk factors for Wilms tumor?” are sometimes found together with Wilms tumors.
But most Wilms tumors do not seem to be caused by inherited gene mutations. Instead, they seem to be the result of gene changes that occur early in a child's life, perhaps even before birth.
In a small number of Wilms tumors there is a change in a tumor suppressor gene known as WTX, which is found on the X chromosome. Another gene that is sometimes altered in Wilms tumor cells is known as CTNNB1. It's not clear exactly what causes these genes to be altered.
Because the genes described above are not altered in all cases of Wilms tumors, there must be changes in other genes that have not yet been found. In many cases, more than one gene change is involved.
Researchers now understand some of the gene changes that may occur in Wilms tumors, but it's still not clear what might cause these changes. Some gene changes may be inherited, but most Wilms tumors are not the result of known inherited syndromes. Other gene changes may just be random events that sometimes happen inside a cell, without having an external cause. There are no known lifestyle-related or environmental causes of Wilms tumors, so it is important to remember that there is nothing these children or their parents could have done to prevent these cancers.
Last Medical Review: 07/27/2012
Last Revised: 01/17/2013