Pregnancy spurs a tumor suppressor

Women who undergo a full-term pregnancy at an early age are less likely to develop

breast cancer than are women who never get pregnant. Scientists experimenting with

rodents now have evidence that a cancer-fighting protein called p53 accounts for

this protection.

The researchers propose that estrogen and progesterone, produced in abundance

during pregnancy, alter breast cells in some fundamental way that enables them to

produce ample p53 later in life.