In a unique animal study presented at the annual meeting of the American Association for Cancer Research, the scientists found that rats susceptible to developing uterine tumors inevitably developed tumors when exposed to an environmental toxin just three days after birth. A single, three-day exposure was enough to "reprogram" the uterus to respond to normal hormonal signals in a way that promoted tumor growth.
The researchers theorize this new model of gene-environment interaction may go some way in explaining why, in a population of people at the same genetic risk, some develop cancer and others don't.
"In genetically susceptible individuals, exposures that occur early in life may have as great or greater an impact on tumor outcome as those that occur during their adult life," says the study's first author, Jennifer Cook, a graduate student in M. D. Anderson's Science Park Research Division in Smithville, Texas.
Molecular biologist Cheryl Walker, Ph.D., the principal investigator on the study and professor of carcinogenesis at M. D. Anderson, says the finding "establishes developmental programming as a novel type of gene-environment interaction."
In the experiment, Cook, Walker and a team of other researchers used rats genetically susceptible to developing uterine leiomyoma, the same kind of benign fibroid tumors that many women have. They exposed these rats to a known environmental estrogen, DES, three to five days after birth, a crucial period in development of the animals' reproductive tract. As adults, a little over half of the genetically predisposed rats developed tumors, compared to 100 percent of DES-exposed rats.
Then, the researchers looked at how uterine tissue in exposed animals responded to normal hormones,
Contact: Julie Penne
University of Texas M. D. Anderson Cancer Center