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 get 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 early kidney cells can 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 doesn’t happen, the cells might somehow begin to grow out of control, which might result in a Wilms tumor.
Normal human cells grow and function based mainly on the information contained in each cell’s chromosomes (long strands of DNA in each cell). DNA carries the instructions for nearly everything our cells do . DNA is divided into units called genes.
Some genes control when our cells grow, divide into new cells, and die. 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 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 they may happen during a person’s lifetime as cells in the body divide to make 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 changes (mutations) in or loss of the WT1 or WT2 genes, which are tumor suppressor genes found on chromosome 11. Changes in these genes and some other genes on chromosome 11 can lead to overgrowth of certain body tissues. This may explain why some other growth abnormalities, like those described in the section “What are the risk factors for Wilms tumor?” are sometimes found with Wilms tumors.
Sometimes these gene changes are passed on from a parent to a child, but most Wilms tumors don’t seem to be caused by inherited gene mutations. Instead, they seem to result from 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 Wilms tumors, there must be gene changes 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 can occur in Wilms tumors, but it’s still not clear what causes these changes. Some gene changes can 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 outside cause. There are no known lifestyle-related or environmental causes of Wilms tumors, so it is important to know that there is nothing these children or their parents could have done to prevent these cancers.
Last Revised: 02/16/2016