"This study is telling us that an environmental reprogramming of a normal response, combined with an inherited gene defect, work together to promote cancer," said NIEHS Director David Schwartz, M.D. "If this model is correct, it will help doctors to determine which individuals are more likely to develop cancers of the uterus, breast and prostate."
The finding should alert doctors to ask more questions about a patient's early-life exposures to chemicals and other harmful agents in order to better predict that person's cancer risk.
"Most people with a family history for a particular disease are concerned about their recent exposures to harmful agents in the environment," said Cheryl Walker, Ph.D., professor of molecular carcinogenesis at the M.D. Anderson Cancer Center and lead author on the study. "We are just beginning to realize that exposures received decades earlier, during critical developmental stages, may be much more important in determining who develops cancer as an adult."
The researchers used a special strain of rats with a defect in a gene called Tsc-2 (tuberous sclerosis complex 2) that made them more susceptible to uterine leiomyomas, benign tumors that are common in women over 30 years of age. These rats were then treated with DES during days 3, 4 and 5 of life, during a critical period of uterine development.
Once the rats reached adulthood, almost 95 percent had developed the uterine tumors. Furthermore, the tumors were much larger and more numerous than those in genetically defective rats not receiving the DES treatment. "These data suggest that environmental exposures during development of the uterus can interact with a preexisting genetic susceptibility to increase the risk of disease," said Walker. "We are looking at a new kind of gene-environment interaction that determines who gets cancer and who doesn't."
According to Walker, the increase in frequency and size of the uterine tumors
Contact: John Peterson
NIH/National Institute of Environmental Health Sciences