Faults in gene called DIS3L2 are linked to an increased risk of a form of childhood kidney cancer, scientists have discovered.
The finding, published in Nature Genetics, gives scientists crucial insights into how Wilms's tumours are caused.
The research could lead to better ways to detect and treat the disease, according to Cancer Research UK, which part-funded the project.
Wilms's tumours, also called nephroblastoma, mainly affect children under the age of five.
Although rare, it is the most common form of kidney cancer in children, affecting around 70 children in the UK each year.
Most children are treated successfully.
The team studied children with Perlman Syndrome, a rare genetic condition in which children are uncommonly large at birth, and have an increased risk of developing Wilms's tumour.
Looking at DNA samples from the children, scientists found evidence of a genetic fault in a region of one of the children's chromosomes (chromosome two).
They then pinpointed a gene in this region, DIS3L2, as the cause of the increased growth, and greater risk of Wilms's tumour.
The team, from the University of Birmingham and led by Professor Eamonn Maher then proved that, in Perlman syndrome, changes in the DIS3L2 gene stop it from working.
They also showed that putting a working copy of DIS3L2 back into cancer cells in which the original copy was faulty, stopped them from multiplying.
Professor Maher said that although Perlman syndrome is a rare disorder, this study "will enable us to diagnose the disorder more easily and give us clues to the pathways that are important in causing the most common kidney tumour in children".
Dr Julie Sharp, senior science information manager at Cancer Research UK, said: "In the future families with Wilms's tumour will benefit from this discovery, which will help doctors to detect and treat this cancer even more effectively."