PHILADELPHIA — The hormone prolactin is produced by the
pituitary gland in the brain and then travels via the
bloodstream to cells throughout the body, where it exerts
multiple reproductive and metabolic effects, most notably on the
breast where it is the master regulator of lactation. In recent
years researchers have found that prolactin is also produced by
some tissues outside the brain, however little is known about
the functions of extra-pituitary prolactin or how its production
is regulated in these tissues. Now, the laboratory of Lewis A.
Chodosh, MD, PhD, chair of the Department of Cancer Biology at
the Perelman School of Medicine, University of Pennsylvania,
reports in Genes & Development that activation of the PI3K-Akt
oncogenic signaling pathway in the mammary glands of mice
rapidly induces cells in the breast itself to produce prolactin.
This, in turn, triggers Stat5 activation, mammary epithelial
differentiation and milk production in virgin mice within a
matter of hours. “Remarkably, these change