title: Cell proliferation in the normal mouse mammary gland and inhibition by phenylbutyrate.
abstract: Ovarian hormones have a pivotal role in the control of proliferation in the mammary gland, and cumulative life-time exposure to ovarian hormones is known to be a determinant of breast cancer risk. We have shown previously that a p.o.-active, long-acting butyrate analogue, sodium phenylbutyrate (PB), reduced proliferation in normal and malignant human breast cells in culture and reduced expression of ovarian hormone receptors, suggesting that PB had cellular effects consistent with decreasing breast cancer risk. The aim of this study was to determine the in vivo effects of PB in the normal mammary gland on epithelial cell proliferation, estrogen receptor alpha (ER alpha) expression, and cyclin D1 expression. BALB/c mice were treated with PB, delivered by mini-osmotic pumps, for 7 days. Moderate (250 mg/kg/day) and high (500 mg/kg/day) PB treatment resulted in a decrease in proliferation in mammary epithelial cells (P < 0.001), determined by bromodeoxyuridine incorporation. Analysis of ER alpha immunostaining revealed a significant reduction in moderate- and high-treatment groups (P = 0.01 and P = 0.02), and expression of cyclin D1 was virtually ablated (P < 0.001). Histone deacetylase inhibition is a known mechanism of butyrate action, and consistent with this, PB increased levels of acetylated histone H3 in the mammary gland. In summary, PB decreased proliferation in the mammary gland in vivo at clinically achievable doses. Decreased proliferation was accompanied by changes in the levels of ER alpha and cyclin D1. These data show that PB modulates parameters thought to be involved in the carcinogenic process in the normal mammary gland, and compounds in this class may therefore be useful candidates for breast cancer chemoprevention.
authors.affiliation: Department of Gynaecological Oncology, Westmead Institute for Cancer Research, Westmead Hospital, Westmead, New South Wales 2145, Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Kennedy
authors.forename: Karen
authors.initials: K
authors.lastname: Byth
authors.forename: Christine L
authors.initials: CL
authors.lastname: Clarke
authors.forename: Anna
authors.initials: A
authors.lastname: deFazio
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D019938:Cyclin D1 / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D047628:Estrogen Receptor alpha; D005260:Female; D006657:Histones / Q000378:metabolism; D007150:Immunohistochemistry; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D010654:Phenylbutyrates / Q000494:pharmacology*; D011960:Receptors, Estrogen / Q000096:biosynthesis
chemical_list: D000970:Antineoplastic Agents; D047628:Estrogen Receptor alpha; D006657:Histones; D010654:Phenylbutyrates; D011960:Receptors, Estrogen; D019938:Cyclin D1; C075773:4-phenylbutyric acid; D001973:Bromodeoxyuridine