Abstract #95

# 95
Mammary gland growth—It’s not just estrogen.
Russell C. Hovey*1, Grace E. Berryhill1, Josephine F. Trott1, Adam L. Lock2, 1University of California, Davis, Davis, CA, 2Michigan State University, East Lansing, MI.

The mammary gland goes through a coordinated series of developmental states during postnatal life in preparation for lactation. These changes ultimately reflect a changing endocrine environment alongside local alterations in the microenvironment. A longstanding assumption has been that estrogens serve as the first essential component for any of these developmental changes to be realized in the mammary glands. Indeed, estrogens can initiate the onset of allometric growth during puberty, and they subsequently potentiate the effects of other endocrine cues on the mammary epithelium during lobulo-alveolar development throughout gestation. More recent evidence from our laboratory indicates that alternative pathways are equally effective in promoting growth of the mammary glands independent of a primary role for estrogens. One fascinating example is the ability of dietary trans-10,cis-12 conjugated linoleic acid (10,12 CLA) to promote allometric growth of the mammary ducts of ovariectomized mice. In subsequent studies we showed that the specific effects of this dietary fat are independent of estrogenic action, and are mediated through IGF-I receptor signaling. The relevance of these findings is emphasized by the fact that this dietary intervention mimics several aspects of the metabolic syndrome manifest in obese humans. At the same time, additional findings from our laboratory indicate that prolactin and progesterone have synergistic effects on epithelial growth and morphogenesis independent of any role for estrogens, which are partly mediated by changes in the local microenvironment. These data collectively support the notion that while estrogens are clearly mitogenic for the growing and developing mammary glands, they are not necessarily requisite. These findings have potential implications for our understanding of mammary growth in all mammals including livestock, as well as direct relevance to the regulation of mammary cancers.

Key Words: prolactin, progesterone, lipid

Speaker Bio
Dr Russ Hovey received a Bachelor of Agricultural Science, major in Animal Science, with First Class Honors from University of Queensland, Australia in 1992. In 1993 he moved to New Zealand in 1993 where he undertook his PhD at Massey University while studying at the Ruakura Research Center in Hamilton, working on the role of the mammary fat pad during development of the mammary gland. In 1997 he moved to the NIH in Bethesda, MD to work in the  Molecular Endocrinology Section of the National Cancer Institute. There he worked on the regulation of mammary gland development and breast cancer by prolactin and steroid hormones. In 2001 he joined the Department of Animal Science at the University of Vermont where he held a joint appointment in the Department of Pathology and the Vermont Cancer Center. In 2007 he relocated to UC Davis and is Professor where he is Professor of Animal Science. There he teaches Lactation Physiology to a class of ~180 students, while his lab is focused on the hormonal and dietary regulation of mammary gland growth, lactation and breast cancer.