Rogue gene linked to breast and childhood cancer risk

Women who inherit one damaged copy of a gene called PALB2 have double the risk of developing breast cancer. And children who inherit two damaged copies have a newly identified serious disorder linked to childhood tumours, according to the findings from two papers published by scientists in Nature Genetics* today (Sunday).

A Cancer Research UK funded team at The Institute of Cancer Research looked for faults in the PALB2 gene in 923 women with breast cancer and a family history of the disease, not caused by the known breast cancer genes BRCA1 or BRCA2. The team also looked for faults in the PALB2 gene in 1084 healthy control women. Their discovery could eventually help identify women at greater risk of developing breast cancer. Understanding more about the specific genetic faults that lead to the disease will hopefully help with improving prevention, diagnosis and “tailor-made” treatment in the future.

The team found faults in ten breast cancer patients and no faults in the healthy women. This difference, which is bigger than would be expected by chance, indicates the gene is linked to some cases of breast cancer. The findings show that carrying a faulty version of PALB2 more than doubles a woman’s risk of developing breast cancer – taking her lifetime risk from one in nine to around one in five.

Professor Nazneen Rahman from The Institute of Cancer Research, who led both studies, said: “We estimate that faults in the PALB2 gene contribute to around 100 cases of breast cancer in the UK each year. Interestingly, one of the ten breast cancer cases we identified as being linked to PALB2 was a male breast cancer, which may mean faults in the PALB2 gene are associated with a higher risk of male breast cancer, but we need to investigate this link further before we know for sure.”

In the second study**, the research team associated the PALB2 gene with a new sub-type of the childhood disorder Fanconi anaemia. The researchers studied 82 children with Fanconi anaemia that was not due to any of the 11 genes known to be responsible for this disease. Seven children were identified as belonging to this new sub-type, – which is characterised by a high risk of childhood solid tumours including medulloblastoma, a type of brain tumour, and Wilms’ tumour, a form of kidney cancer. It is when, very rarely, two faults in the PALB2 gene are inherited that this newly identified sub-type of Fanconi anaemia develops.

Professor Rahman added: “Not only have we found that carrying a single faulty version of PALB2 leads to a small increased risk of breast cancer, but also that carrying two faulty copies of the gene is related to an aggressive form of the childhood disorder Fanconi anaemia.”

PALB2 is a DNA-repair gene, so people with a faulty version of this gene cannot repair damaged DNA correctly. Individuals who carry faulty DNA-repair genes are at an increased risk of cancer because their healthy cells are more likely to accumulate genetic damage that can trigger cells to replicate uncontrollably, causing cancer.

Professor John Toy, Cancer Research UK’s medical director, said: “The discovery of another gene that increases breast cancer risk albeit only for a small number of women is very important. Gradually, we are beginning to learn more and more about the rogue genes that cause cancer in some families, and we hope one day to use this knowledge to help those at an increased risk of the disease. All children with Fanconi anaemia are already monitored very closely for signs of cancer, particularly leukaemia. Identifying children with a unique type of this disease, one characterised by a high risk of developing certain solid tumours, is a significant finding that will assist doctors looking after these particular patients in the future.”

ENDS

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