מתוך medicontextt.co.il
WESTPORT, CT (Reuters Health) – Increased levels of tumor suppressor protein p53 are brought on by early pregnancy in rats and mice, perhaps explaining why early pregnancy is associated with a reduced risk of breast cancer. The data are reported in the early online edition of the Proceedings of the National Academy of Sciences for October 23.
"Women who have a pregnancy at age 19 or younger have a 40% to 50% decreased risk of breast cancer," Dr. Bert W. O'Malley from the Baylor College of Medicine, Houston, Texas, noted in an interview with Reuters Health. "So there is something about an early pregnancy that gives a protective effect against cancer."
To identify the mechanism involved in this protective effect, Dr. O'Malley and colleagues administered estrogen and progesterone to young female rats and mice. They found "a striking increase in both the levels and nuclear accumulation of p53" compared with untreated age-matched virgin animals.
When the researchers induced cancer with carcinogenic chemicals later in the animals' lives, they observed that hormone administration blocked mammary gland epithelial cell proliferation. "The answer seemed to be that this short exposure to estrogen and progesterone early in life leads to a chronic continuous higher level of p53," Dr. O'Malley said.
Whether this effect is the same in humans is not known, but the findings "raise the question whether a short period of drug therapy could make young women resistant to breast cancer," he noted.
Dr. O'Malley and his group plan to continue their work to find the mechanism whereby p53 expression becomes elevated, and to find the least toxic therapy that could be given to raise the level of p53 and provide protection against breast cancer.
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