Microbiologist Michele Fluck studies a virus that induces many kinds of tumors in mice, particularly in their mamary glands. A protein produced by the virus turns on a cancer switch in the mice. Fluck explains that "when a cell is supposed to grow, it receives a signal to divide from a growth factor such as a hormone. Through a series of relays, that message makes its way to the cell nucleus. But when a cell undergoes a mutation, it believes the relay switch is always on and doesn't stop growing. Even for the most astute biologist, understanding this relay process is a nightmare."
For twenty years, Sandra Haslam and her students have studied the role of hormones and cell-cell interactions in controlling growth of normal breast cells. Such research could affect the estimated 39 million female baby boomers about to enter menopause, among whom hormone replacement therapy or HRT is popular because of its known positive effects on cardiovascular disease and osteoporosis. Working directly with human breast tissue, they have found that the type of hormones taken and the timing of HRT have a potent effect on cell growth. These types of studies can help us understand if HRT plays a role in cancer.
Fluck and Haslam have joined forces to study the induction of mammary gland tumors in mice following viral infections. They are particularly interested in how tumor outcome is affected by the age of the mice and estrogen. A correlation has emerged: in young mice, tumors arise independently of the presence of estrogen; in older mice, tumors are estrogen-dependent. "Few people are using this model to study breast cancer," says Haslam. "If we can understand the basis of transitions in cells, we may be able to find treatment strategies."
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