Exposed mice pass increased risk of leukemia to offspring

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Wednesday July 22 10:26 PM EDT 

MANCHESTER, England (AP) - Scientists have found that a group of mice 
exposed to radiation passed on an increased risk of leukemia to their 
offspring, according to research published Wednesday. 

Brian Lord, head of a research team at the Paterson Institute for Cancer 
Research in Manchester, northwest England, said that although more work 
was needed, research carried out on mice exposed to radiation suggested 
that it could damage offspring if a second cancer trigger was also 
present in the offspring. Lord's research was published this week in the 
British Journal of Cancer. 

``What it does show us, for the first time, is a potential way in which 
paternal irradiation can lead to an increase in leukemia risk for the 
next generation. It shows us how DNA defects can be passed from 
generation to generation,'' he said. 

Researchers independent of the British study said they were skeptical 
that cases of childhood leukemia could be connected to fathers' 
radiation exposure. 

Scientists in Britain have been debating whether radiation causes 
childhood leukemia for many years. A controversial study in 1990 claimed 
that a cluster of leukemia cases in northern England resulted from 
parents working at the Sellafield nuclear power plant in Cumbria, 
northwest England. Other studies of atomic bomb survivors and people who 
have had radiotherapy found no evidence to support the theory. 

In the journal, Lord said that research was carried out on 40 mice, with 
half of them injected with plutonium-239 three months before being mated 
with healthy females. Plutonium-239 is used in the production of nuclear 
weapons. 

Their offspring were then injected with a second cancer-causing agent 
and monitored for the onset of leukemia and lymphoma. The mice injected 
with plutonium had DNA damage in their bone marrow and passed some of 
the damage on to cells in their offspring, increasing their 
vulnerability. 

Leukemia developed earlier and more frequently in those affected cells 
when the mice were exposed to a second cancer-causing chemical than in 
normal mice exposed to the same chemical. 

Lord said that although this alone was not enough to cause leukemia in 
its offspring, it nearly doubled vulnerability to the disease. 

Dr. Michael Thun, chief of epidemiological research for the American 
Cancer Society, said he had not read the study and was reluctant to 
comment directly. He said the question of radiation affecting the 
fathers' sperm was ``scientifically interesting,'' but had little 
practical importance to patients at this time. 

``The way to avoid cancer is not to worry about your father's 
occupational exposure,'' he said. ``It's likely that what you do in life 
would be much more harmful and contribute to your risk of getting 
cancer.''