title: RANK ligand mediates progestin-induced mammary epithelial proliferation and carcinogenesis.
abstract: RANK ligand (RANKL), a TNF-related molecule, is essential for osteoclast formation, function and survival through interaction with its receptor RANK. Mammary glands of RANK- and RANKL-deficient mice develop normally during sexual maturation, but fail to form lobuloalveolar structures during pregnancy because of defective proliferation and increased apoptosis of mammary epithelium. It has been shown that RANKL is responsible for the major proliferative response of mouse mammary epithelium to progesterone during mammary lactational morphogenesis, and in mouse models, manipulated to induce activation of the RANK/RANKL pathway in the absence of strict hormonal control, inappropriate mammary proliferation is observed. However, there is no evidence so far of a functional contribution of RANKL to tumorigenesis. Here we show that RANK and RANKL are expressed within normal, pre-malignant and neoplastic mammary epithelium, and using complementary gain-of-function (mouse mammary tumour virus (MMTV)-RANK transgenic mice) and loss-of function (pharmacological inhibition of RANKL) approaches, define a direct contribution of this pathway in mammary tumorigenesis. Accelerated pre-neoplasias and increased mammary tumour formation were observed in MMTV-RANK transgenic mice after multiparity or treatment with carcinogen and hormone (progesterone). Reciprocally, selective pharmacological inhibition of RANKL attenuated mammary tumour development not only in hormone- and carcinogen-treated MMTV-RANK and wild-type mice, but also in the MMTV-neu transgenic spontaneous tumour model. The reduction in tumorigenesis upon RANKL inhibition was preceded by a reduction in pre-neoplasias as well as rapid and sustained reductions in hormone- and carcinogen-induced mammary epithelial proliferation and cyclin D1 levels. Collectively, our results indicate that RANKL inhibition is acting directly on hormone-induced mammary epithelium at early stages in tumorigenesis, and the permissive contribution of progesterone to increased mammary cancer incidence is due to RANKL-dependent proliferative changes in the mammary epithelium. The current study highlights a potential role for RANKL inhibition in the management of proliferative breast disease.
authors.affiliation: Department of Hematology/Oncology Research, Amgen Inc, Seattle, Washington 98119, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Gonzalez-Suarez
authors.forename: Allison P
authors.initials: AP
authors.lastname: Jacob
authors.forename: Jon
authors.initials: J
authors.lastname: Jones
authors.forename: Robert
authors.initials: R
authors.lastname: Miller
authors.forename: Martine P
authors.initials: MP
authors.lastname: Roudier-Meyer
authors.forename: Ryan
authors.initials: R
authors.lastname: Erwert
authors.forename: Jan
authors.initials: J
authors.lastname: Pinkas
authors.forename: Dan
authors.initials: D
authors.lastname: Branstetter
authors.forename: William C
authors.initials: WC
authors.lastname: Dougall
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000008:administration & dosage / Q000009:adverse effects; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced* / Q000187:drug effects* / Q000473:pathology; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000556:secondary; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics / Q000502:physiology; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage / Q000009:adverse effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009361:Neoplasm Invasiveness; D011230:Precancerous Conditions / Q000473:pathology / Q000517:prevention & control; D011374:Progesterone / Q000008:administration & dosage / Q000009:adverse effects; D011372:Progestins / Q000008:administration & dosage / Q000009:adverse effects*; D053245:RANK Ligand / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism
chemical_list: D011372:Progestins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011374:Progesterone; D015127:9,10-Dimethyl-1,2-benzanthracene; D017258:Medroxyprogesterone Acetate