tumor fighters. Estrogen and progesterone-trigger fight against cancer proteins in rat cells (C and D), compared to those without additional hormone (A and B).
Women who have a baby before they are 35 tend to have a lower risk of breast cancer. This has been clear for years now, researchers have found finally found out why. The effects of the fight against cancer in pregnancy may be due to an inhibitor of tumor famous, p53.
The p53 protein helps keep the cancer in check by controlling a cell raking in response to DNA damage. One strategy is to stop a cell from dividing until it destroys itself, or its DNA can be repaired. In rats, the researchers found that treatment with pregnancy hormones estrogen and progesterone protects against breast cancer. Pregnancy hormones also cause a spike in the levels of p53. However, the rats are protected against breast cancer long after the hormone levels return to normal. Molecular biologist Bert O'Malley and colleagues at Baylor College of Medicine in Houston, Texas, wanted to understand why.
When the team of O'Malley exposed female rats to estrogen and progesterone to mimic pregnancy, the animals maintained high levels of p53 in mammary cells long after the hormone treatment ended. Pregnancy induced the same effect: During 35 days after the rats had given birth, p53 levels were significantly higher than in virgin rats. When rats were then exposed to a carcinogen, rats treated with hormones showed high levels of p53 and cell proliferation reduced compared to untreated rats, blank controls. The researchers report their findings in the October issue of the early edition of Proceedings of the National Academy of Sciences 16.
The group from O'Malley showed for the first time the additional protection afforded by p53 lasts well beyond the initial hormonal explosion, said D. Joseph Jerry, a cancer researcher at the University of Amherst, Massachusetts. He speculates that this new understanding may lead to preventive treatments that target p53 - and avoid the side effects associated with hormones. Jerry warns, however, that other molecular players can play a central role in keeping cancer at bay.
Related Sites
More on p53
bracing p53 to the war on cancer ( science NOW, December 23, 1999)
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