MU researcher links hormone replacement therapy to bre...( COLUMBIA Mo. Millions of post-menop...)

COLUMBIA, Mo. Millions of post-menopausal women use hormone replacement therapy (HRT) as a method to reduce symptoms associated with menopause. In a recent University of Missouri study, researchers found that one of the hormones used in HRT, a synthetic progestin, could be a major factor in promoting breast cancer. At the same time, the researchers have compelling evidence that using an antibody that prevents new blood vessel formation in tumors, or a small molecular drug, known as PRIMA, with similar properties as the antibody may be effective in treating or preventing the negative effects of progestin.

In a study published in the journal, Cancer Research, MU scientist Salman Hyder and his research team found that exposing tumor cells to progestin caused an increase in a growth factor that is involved in the formation of new blood vessels in tumors. Increasing the blood supply allows the tumors to expand as the availability of nourishment increases. However, when they used an antibody that inhibits the growth factor, the tumor shrank. Hyders team found similar results using PRIMA, which re-activated a protein known as p53. When p53 was activated within tumor cells, the number of breast cancer cells reduced significantly.

As women age, many develop tiny lesions in their breasts, said Hyder, professor of biomedical sciences in the College of Veterinary Medicine and the Dalton Cardiovascular Research Center. The majority of the time, these lesions never expand. We think this might be due to a specific protein, p53, that, under normal circumstances, prevents tumor cells from living. We found in our study that when the protein is active, it reduces the number of breast cancer cells in the body by inhibiting the growth factor that supplies blood vessels to the tumor. However, when the cells of these lesions are exposed to progestin in a body that does not have an active p53 protein, we found that the cells might start expanding and turn into tumo
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