EAST LANSING, Mich. Researchers have identified how the hormones progesterone and estrogen interact to increase cell growth in normal mammary cells and mammary cancers, a novel finding that may explain why postmenopausal women receiving hormone replacement therapy with estrogen plus progestin are at increased risk of breast cancer.
The discovery that both estrogen and progesterone must be present for the increased production of the protein amphiregulin, which binds to mammary cells and promotes cell growth, could lead to new treatment methods for the disease, said Sandra Haslam, director of Michigan State University's Breast Cancer and the Environment Research Center and lead researcher on the project.
The study, funded by the Department of Defense's Breast Cancer Research Program and published in Hormones and Cancer, looked at why progesterone combined with estrogen may contribute to increased breast cancer risk. In the study, researchers used both the native hormone, progesterone, and a synthetic compound, progestin obtaining the same results.
The finding might help explain earlier results from the groundbreaking Women's Health Initiative showing the risk of breast cancer is significantly greater for postmenopausal women who received hormone replacement therapy with combined estrogen plus progestin compared to women receiving estrogen alone.
"Also, breast cancers that develop in women receiving estrogen plus progestin are more invasive and deadlier," Haslam said. "What is the progestin doing to increase the risk of tumor growth?"
Along with co-investigator Anastasia Kariagina, a colleague in the College of Human Medicine and Department of Physiology, Haslam identified the protein amphiregulin and its receptor as one potential culprit.
|Contact: Jason Cody|
Michigan State University