Cancer risk in children of radiation-exposed parents

The children of a person who is exposed to radiation could be susceptible to cancer as a result, according to research carried out in Britain. Even low levels of radiation could cause mutations that cross the generational divide and could be detected in offspring.

"We did not expect these results," said Dr Yuri Dubrova, Wellcome Trust Senior Lecturer in the Department of Genetics at the University of Leicester, who yesterday presented his research at the 11th International Congress on Radiation Research under way in Dublin. "We finalised them two weeks ago and we checked them twice."

Dr Dubrova and colleagues were looking at mice exposed to nuclear radiation and watching for signs of cell mutations in their offspring. They were looking in particular at small segments of the genetic blueprint known as "microsatellites" which are very susceptible to mutation.

The researchers found the offspring of exposed male mice had six times the rate of mutation compared to mice that had not been irradiated. "We are dealing with an enormous increase in the mutation rate," he told a conference session at University College Dublin yesterday.

The radiation causes a phenomenon known as "genomic instability", a tendency for genetic material in the cells to recombine to cause unpredictable mutations that in turn could cause cancers. This subject is under intense study at the Radiation Science Centre of the Dublin Institute of Technology, organisers of the week-long conference which has brought 1,200 delegates to Dublin.

Exposure to radiation caused an increased probability of blood disorders such as leukaemia in subsequent generations, according to research by Dr Brian Lord and colleagues of the Paterson Institute for Cancer Research at the Christie Hospital, Manchester. There was a considerable increase in incidence of the disease in these offspring compared to unirradiated control groups, he said.

The data suggested it was not caused by direct inheritance but by an increased likelihood of genomic variability passed on to the next generation.

Earlier, a number of researchers presented data which tried to demonstrate the effects of genomic instability and the changes it caused in test mice. Dr Bob Ullrich, of the University of Texas in Galveston, described his work which attempted to answer the question "What does radiation do to ultimately lead to cancer?"

Their test results were able to separate the damage caused directly by the radiation exposure and the changes brought about due to genomic instability. They cultured cells that were changed because of it. They then studied what genes might be involved and whether there was a genetic component to this instability.

Dr Anders Wennborg and colleagues of the Karolinska Institutet in Sweden and the Bo Lambert company described studies of chromosomal damage that arose many days after exposure to radiation. These changes were linked to instability and not to direct mutations caused by the radiation. The data he said were "strongly indicative of a progressive aberration" in the genome.